1Zoologische Staatssammlung München, Münchhausenstr. 21, 81247 München, Germany2Huinay Scientific Field Station, Fundación San Ignacio del Huinay, Casilla 462, Puerto Montt, Xa Región, Chile
The hardbottom benthic communities of the southern Chilean fjord region are among the leaststudied worldwide. Within the framework of biodiversity surveys of the Comau Fjord system(42°10’ – 42°30’S), new distributional and biological information on chitons has been obtained.This paper deals with nine species, belonging to four families, observed and collected in shallowwater (0–39 m depth) between 2003 and 2005. Photographs of living specimens in their habitat aregiven for the first time. Radulae and external features are compared. Problematic taxa, such asChiton magnificus, are discussed. Based on examination of the type material, Tonicia calbucensis isre-evaluated and recognized as a valid species, differing from T. lebruni by a number of characters.For the first time an infection by an endoparasitic nematode is reported in chitons. The speciesreported herein were already known from southern Chile, but the species composition in ComauFjord system differs from that of the more exposed Pacific Ocean coast.
Introduction The Polyplacophora of the southern Chilean fjord system (42ºS–55ºS) have been studiedlittle because of the remoteness, difficult access, and inhospitable conditions of the region.Leloup (1956) was the first to summarize all available geographical and taxonomicinformation on southern Chilean chitons. More recently, Reid & Osorio (2000), Osorio etal. (2002), and Osorio & Reid (2004) contributed further distributional data on thePolyplacophora from the southern Chilean fjord region.
1341ZOOTAXA Leloup (1956) revised the chiton material collected from shallow water to a depth of
300 m during the Lund University Chile Expedition in the years 1948–1949. He providedvaluable distributional and ecological data from 52 stations along the Chilean coastbetween Iquique (20°S) and Punta Arenas (53°S) and mentioned 19 chiton species fromthe region between Puerto Montt (41°28’S) and the Chonos Archipelago (44°50’S).Unfortunately, Leloup’s species interpretations were not always clear and illustrations ofthe material he investigated are in most cases restricted to perinotum elements and aesthetearrangements. Thus, to date, no clear taxonomic statement is possible without a re-examination of some of the species (e.g. members of Tonicia) from Leloup’s originalmaterial.
Reid & Osorio (2000) were the first to give a substantial molluscan bioinventory forthe Chilean fjord system. Specifically, they reviewed the hydrographical and biologicalconditions at approximately 46°S in the protected Estero Elefantes and Laguna San Rafael.Their investigation focused on shallow-water depths (0–15 m) at 31 stations, for whichthey reported a total of 62 molluscan species. Their findings included nine species ofpolyplacophorans: Leptochiton (Leptochiton) medinae (Plate, 1899), Chaetopleura(Chaetopleura) peruviana (Lamarck, 1819), Ischnochiton (Ischnochiton) stramineus(Sowerby in Broderip & Sowerby, 1832), Ischnochiton (Haploplax) pusio (Sowerby inBroderip & Sowerby, 1832), Plaxiphora (Plaxiphora) aurata (Spalowsky, 1795), Chiton(Amaurochiton) magnificus bowenii King & Broderip, 1832, Chiton (Chondroplax)granosus Frembly, 1827, Tonicia atrata (Sowerby, 1840), and Tonicia chilensis (Frembly,1827). All of these species were mentioned in Leloup’s revision of chitons from the area.
While sampling two transects in the tide-line of the intertidal zone in the vicinity of theIsla Traiguén (45°S 73°W), Osorio et al. (2002) identified a total of 18 molluscan speciesincluding the previously recorded chitons I. pusio, P. aurata, C. magnificus boweni (sic),and T. atrata. They also reported the depth ranges for two of these species and summarizedthe temperature and salinity conditions for one of the two sampling sites. Osorio & Reid(2004) reported 22 molluscan species from a 12 day survey (20 trawl stations) within thearea between Boca del Guafo (43°39’S) and the Estero Elefantes (46°28’S). Their materialcontained an additional chiton, not new for this area, but with a remarkable bathymetricrecord, namely Tonicia disjuncta (Frembly, 1827) from 300 m depth.
Most recently, Sirenko (2006b) listed chitons from the Magellan Strait and theFalkland Islands, including some new geographic records, depth range extensions andobservations on reproductive behavior. Of 17 species known from the Magellan Strait,Sirenko re-examined 14 species using own material.
In contrast to the above cited works, which mainly refer to the more or less exposedwaters of the Pacific Ocean, this study presents a catalogue of Polyplacophora found in theComau area. This fjord system is as protected as the Estero Elefantes but is located at thenorthern end of the Chilean southern fjord system. The specimens were collected duringjoint field surveys in March 2004 and February 2005; additional material comes from
1341ZOOTAXAlong-term collecting activities of Günter Försterra and Verena Häussermann. Comau Fjord
with its two lateral Cahuelmo and Quintupeu fjords opens towards the Gulf of Ancud andshows both highly specific abiotic conditions and a remarkable variety of benthiccommunities (Försterra & Häussermann 2003, Försterra et al. 2005, Schrödl et al. 2005).This catalogue is intended to be the basis for future collecting and monitoring efforts in theChilean fjord area, providing relevant characters for chiton identification and availablehabitat information.
Collecting sites and methods
Comau Fjord is characterized by steep slopes and a maximum depth of nearly 500 m in thecenter, with the deepest part near the mouth. The surrounding mountains rise up to 2000 mand are covered by dense extratropical rainforest with its lower limit coinciding with themaximum tide level. Very high precipitation (an annual average of approximately 6000mm was measured during the last 3 years) is responsible for a low salinity layer (LSL).The LSL has a thickness between 0.5 m in summer and 10 m in winter at the head of thefjord, with minimum salinities < 20, and a marked pycnocline. The LSL, in combinationwith a maximum tidal amplitude of more than 7 m, extends the zone influenced bybrackish water down to 15–18 m. Temperatures of the surface water vary between morethan 20°C in summer and 5–6°C in winter. Water below 15 m has a fairly constanttemperature of 8–12°C with salinities between 28‰ and 32‰.
Between September 2004 and February 2005 surveys of invertebrates at 12 stations(Figure 1) within Comau Fjord and the lateral Quintupeu fjord were performed by SCUBAdiving to 40 m depth. Chitons were photographed in situ. In most cases referencespecimens were collected to maximize the overall species number, but not quantitativelyper station. Reference material was either fixed in 4% formalin-seawater or in 78–96%ethanol, and has been deposited in the Mollusca Section of the Bavarian State Collectionof Zoology (hereafter ZSM Moll). Additional material from Comau Fjord system andphotographs of living specimens in their habitat were provided by two of the authors (GFand VH).
This review provides ranges of body sizes, coloration, valve and perinotummorphology, and distribution, based mainly on the available literature (Leloup 1956; Kaas& Van Belle 1985a, 1994; Bullock 1988). All radula characteristics, and the descriptivesection of the Tonicia species, are based on light microscope observations of specimens atthe ZSM. The radula of Tonicia calbucensis was examined by scanning electronmicroscopy (SEM) as described in Schwabe & Ruthensteiner (2001). The identification ofthis species was verified by comparisons with the lectotype. No reference specimen (NRShereafter) is available for Nuttallochiton martiali. Size information is available forreference specimens only (i.e., not for all of the living specimens photographedunderwater).
1341ZOOTAXA(3) Western shore of Comau Fjord opposite Huinay Station (cross Huinay N):
42º23.276´S; 072º27.657´W; steep rocky wall with cobbles and some blocks on silty-muddy sediment, volcanic liquids with bacteria mats, with Macrocystis, 6–39 m.
(4) Western shore of Comau fjord opposite of Huinay Station (cross Huinay S): 42º23.460´S; 072º27.445´W; 3–25 m, rocky wall with terraces with stones and some
sand, Macrocycstis, (in 5–15 m depth a dense coverage of Membranipora and somehydrozoans).
(5) Steep wall north of Punta Llonco (S.W.A.LL): 42º19.894´S; 072º27.661´W; 3–17.5m.
(6) Punta Llonco. 42º20.634´S; 072º27.429´W; 0–30 m, sandy slope with blocks andstones, upper part with large Macrocystis.
(7) Punta Huinay: 42º22.483´S; 072º25.693´W; 0–30.5 m, tide pools and rocks withred encrusted algae.
(8) Playa Llonco (bay south of Punta Llonco; 50 m east of (6)): 42º20.695´S;072º27.212´W; 2–20 m; sandy slope with blocks and stones, upper part with largeMacrocystis.
(9) Rio Tambor: 42º24.161´S; 072º25.235´W (no chitons were collected).(10) Entrance Quintupeu fjord: 42º28.215´S; 072º28.214´W (no chitons were
Lepidopleurus medinae Plate, 1899: 82–89, pl. 5, figs. 204–206.Detailed bibliography and synonymy in Kaas & Van Belle (1985a: 80).
Size: Maximum length about 10 mm (Plate 1899). Body outline: Elongate oval, dorsumround. Color: Cream, normally covered by a darker properiostracum. Valves: Rather thin;head valve semicircular, posterior valve margin widely V-shaped, slightly notched inmiddle, sculptured by approximately 80 radial ribs of fine roundish granules; intermediatevalves rectangular, posterior margin straight, apex not present, lateral areas slightlyelevated, with about 15 radial rows of granules, central area with about 70 longitudinallyarranged, closely set, roundish granules; tail valve semicircular with mucro centrally,postmucronal slope steep and straight, postmucronal area sculptured like head valve,antemucronal area similar to central area of intermediate valves; growth marks present onterminal valves and lateral areas. Articulamentum: Thin and white. As diagnostic forgenus insertion plates missing, apophyses well developed. Perinotum: Dorsally coveredwith flat, finely ribbed conical scales, up to 6 ribs, not imbricated. Ventrally with elongatescales arranged in radial rows. Ctenidia: Restricted to posterior part of mantle cavity, incontact with anal papillae. Radula (ZSM Moll 20050428; 7 mm body length): radulalength 4.3 mm. Radula cartilage length 1.4 mm. 67 teeth rows, 51 of them withmineralized teeth. Central tooth slender and very short, centrally constricted; blade simpleand directed inwards. First lateral tooth slightly larger, also with simple inward-directedblade. Second lateral tooth with elongate sharply pointed, bidentate head; outer denticlesmaller than inner.
Material: A single specimen (ZSM Moll 20050341) was found at station 4, at a depthbetween 20–25 m on a steep wall under a stone (see Table 1).
Distribution: The species occurs in the Magellanic Region south of 42°S along bothsides of South America down to the Straits of Magellan (Kaas & Van Belle 1985a). Whilealso reported from the intertidal zone, it generally seems to prefer depths around 15–30 m(fide Reid & Osorio 2000; this report). Maximum depth is recorded from 250–300 m(Leloup 1956). Leptochiton medinae inhabits a variety of hard substrata, such as holdfastsof Macrocystis, cobbles encrusted with calcareous red algae, or pebbles and shells on silt.Leptochiton medinae was found in areas with oceanic salinity levels, and also inhyposalinic locations with only 15–22‰, thus it seems to be tolerant of wide salinityvariations. The single record of the species in Comau Fjord does not necessarily mean thatit is rare. It is more likely that the species was overlooked, because of its small size and itsdark properiostracum, which may provide it with camouflage.
Remarks: The species could be easily mistaken for Ischnochiton stramineus(Sowerby in Broderip & Sowerby, 1832). Compared to the latter species, L. medinae lacksinsertion plates in the valves, has a much narrower perinotum, the dorsal perinotum scales
1341ZOOTAXAare of a different form, and the ctenidia differ in their posterior position and in being in
contact with the anal papillae.
FIGURES 2–5. Leptochiton medinae (Plate, 1899). 2. Dorsal view of the damaged specimen fromstation 3 (ZSM Moll 20050341). 3. Ventral view of the same specimen as Figure 2. 4. Dorsal viewof a complete specimen from Isla Cailin, Chile (ZSM Moll 20000862). 5. Ventral view of samespecimen as Figure 4. 6. dorsal view of Ischnochiton (Haploplax) pusio (Sowerby in Broderip &Sowerby, 1832) from station 4 (ZSM Moll 20040967). 7. Underwater photograph of Chitonmagnificus Deshayes, 1827 in situ (ZSM Moll 20034101) from station 7, illustrated specimenmeasures 26 mm in length. Scale bars: 2–6 = 1 mm.
Type species: Chiton textilis Gray, 1828, by subsequent designation Gray (1847: 168, as“Chiton textile” Gray, 1828).
Subgenus Haploplax Pilsbry, 1894
Type species: Lophyrus smaragdinus Angas, 1867, by original designation.
Ischnochiton (Haploplax) pusio (Sowerby in Broderip & Sowerby, 1832)(Figure 6)
Chiton pusio Sowerby in Broderip & Sowerby, 1832: 105.Detailed bibliography and synonymy in Kaas & Van Belle (1994: 67).
Size: Maximum length 21 mm (Kaas & Van Belle 1994). Body outline: Oval, ratherelevated, dorsum subcarinated. Color: Usually olive-brown to blackish brown, withbrighter spots. Valves: Rather solid; appear smooth (microgranulated) except forcommarginal growth lines on terminal valves and lateral areas of intermediate valves; headvalve less than semicircular, posteriorly widely V-shaped, slightly notched in middle;intermediate valves rectangular, posteriorly faintly convex on both sides of slightlyprotruding apex, lateral areas hardly raised; tail valve with mucro in anterior third,postmucronal slope nearly straight and rather steep. Articulamentum: Bluish white togreenish blue, sometimes with darker streaks in central part, apophyses subtrapezoidal andrather short, slit formula: 11–14 / 1 / 11, slit rays present in all valves, teeth sharp andrather smooth at outside. Perinotum: Dorsally covered with smooth, solid, imbricatedscales obtusely pointed; ventral side with radial rows of opaque rectangular to elongatescales. Ctenidia (ZSM Moll 20040966; 12 mm body length): 25 holobranchial ctenidia oneach side of foot, posterior ctenidia longer than anterior ones. Radula (12 mm specimen):about 3.2 mm in length; radula cartilage 1.6 mm in length; 87 teeth rows, 72 showingmineralized teeth. Central tooth slender, extended at its base, with simple roundish blade;first lateral tooth twice length of central one, leaf-shaped, second lateral tooth withbicuspid head, inner denticle longer than outer.
Material: Four specimens were collected at station 1, in a depth between 5 and 30 m
1341ZOOTAXAand two additional specimens at station 4, between 5 and 20 m (see Table 1).
Distribution: Ischnochiton pusio occurs from Tumbes, Perú, southwards to theAtlantic coast of Tierra del Fuego, Argentina. It is also known from offshore of theChilean Juan Fernández Archipelago (Kaas & Van Belle 1994). According to Reid &Osorio (2000), I. pusio inhabits the underside of stones and other hard substrata from theintertidal zone down to 90 m, with a depth preference around 5–30 m in fjord areas. This issupported by our study and we speculate that Ischnochiton pusio is less tolerant of salinityfluctuations and therefore lives below the halocline.
Chitonidae Rafinesque, 1815
Chiton Linnaeus, 1758
Type species: Chiton tuberculatus Gray, 1828, by subsequent designation, Dall (1879:297).
Chiton magnificus Deshayes, 1827: 454.Detailed bibliography and synonymy in Bullock (1988: 163).
Size: Maximum length 90 mm (Bullock 1988). Body outline: Broad-oval, slightlycarinated, rather flat. Color: In general dark bluish grey (orange red specimens also occur)with brighter dots and various black marks. Valves: Head valve semicircular, with wide V-shaped to straight posterior margin unnotched in middle, with numerous radially arranged,shallow ribs; intermediate valves rectangular with slightly concave posterior margin atboth sides of faintly protruding apex, lateral areas slightly elevated, sculptured with up to 5radial ribs between a wider diagonal ridge and a very wide posterior rib; tail valvesemicircular with an anterior mucro, postmucronal area with same sculpture as head valveand lateral areas. Aesthetes appear porous, occurring in interspaces of faintly elevatedradial ribs, generally brighter in coloration than underlying areas. Growth marks visible onall valves. Articulamentum: Strongly developed, bluish-white, apophyses short,trapezoid, jugal sinus serrated, slit formula: 14 / 1 / 14, slit rays present in all valves, teethstrongly grooved outside, teeth short, sharp. Perinotum: Dorsally covered with solid,smooth, roundish-triangular, obtusely pointed scales of two different sizes. Scales situatedclosest to valves smaller than scales towards the outer margin, clear boundary visible.Perinotum fringe consisting of smooth, sharply pointed, straight, brownish, calcareousspicules. Elongate, ventral scales opaque and arranged in radial rows. Ctenidia (Moll
1341ZOOTAXA 20034098, 28 mm body length): 48 ctenidia on each side of foot arranged holobranchially;
ctenidia close to anus smaller than those under 7th valve. Radula (specimen of 28 mmbody length): Radula 13.5 mm long, 78 teeth rows, 64 of them mineralized. Radulacartilage 4.9 mm in length. Central tooth very slender, with simple backward directedblade. First lateral tooth of double size, distally extended to simple spoon-like inward-directed blade. Head of second lateral tooth shows simple discoidal blade, slightly pointedin middle of cutting edge.
Material: Of the 14 specimens collected in the investigated area, five are from station5 (6–30 m) and nine from station 7 (2.3–30.5 m) (see Table 1). One specimen (ZSM Moll20050026) from station 3 was found in the immediate vicinity of an underwater thermalspring at a depth of 28 m. The surrounding area was densely covered by a mat of filiformsulphur-oxidising bacteria (Figure 8).
Distribution: Chiton magnificus occurs from Perú southwards to the ChonosArchipelago. It inhabits rock pools and boulder fields with strong water exchange (Bullock1988). It was reported from depths between 0–13 m (Zagal & Hermosilla 2001). The newmaterial in this study extends its depth distribution down to 30.5 m.
Remarks: Bullock (1988) interpreted this species as Chiton magnificus magnificus.Based on similarities in shell characters and perinotum and on the basis of nearly completegeographical isolation he also considered Chiton bowenii King & Broderip, 1831 to be asubspecies of Chiton magnificus, being aware that there are intermediate forms in thetransition zone around Chiloé Island. Reid & Osorio (2000) already discussed theproblems with Bullock’s conclusions, pointing out that he mentioned both subspecies fromChiloé Island. Unfortunately, we do not have enough material to revise the Chitonmagnificus complex. While Reid & Osorio’s specimens from the Chonos Archipelagolook more like the southern Chiton bowenii, the specimens reported herein correspondwell with the specimens illustrated by Bullock (1988: figures 57, 58), which could besyntypes of Chiton subfuscus Sowerby in Broderip & Sowerby, 1832. Except for someminor shell differences, the latter species does not differ significantly from C. magnificus,and thus Bullock (1988) regarded them as synonymous.
One of the examined specimens (ZSM Moll 20050027) was infested by endoparasiticnematodes. According to Dr. Nicola Reiff (Munich), two larger females (2.1–2.5 mm)were found which most probably belong to the family Chromadoridae. A more detailedexamination of the parasites is in progress.
Tonicia Gray, 1847
Type species: Chiton elegans Frembly, 1827 [non de Blainville, 1825], by subsequentdesignation Gray (1847: 168).
FIGURE 8. Underwater photograph of a bacteria mat at an underwater spring with sulphurouswater at station 3, the upper chiton is Tonicia chilensis (Frembly, 1827) (ZSM Moll 20050025)illustrated specimen measures 17.3 mm in length, the lower Chiton magnificus Deshayes, 1827(ZSM Moll 20050026) illustrated specimen measures 15.6 mm in length. 9. Underwaterphotograph of Tonicia atrata (Sowerby, 1840) in situ (ZSM Moll 20050020) at station 3, illustratedspecimen measures c. 30 mm in length. 10. Underwater photograph of Tonicia calbucensis Plate,1897 in situ (NRS). 11. Underwater photograph of Tonicia chilensis (Frembly, 1827) in situ (NRS)at station 7. 12. Underwater photograph of Tonicia smithi Leloup, 1980 in situ (ZSM Moll20050012) at station 12, illustrated specimen measures c. 50 mm in length. 13. Underwaterphotograph of Plaxiphora aurata (Spalowsky, 1795) in situ (ZSM Moll 20034100) at station 7,illustrated specimen measures c. 28 mm in length.
Chiton atratus Sowerby, 1840: 294.Detailed synonymy in Kaas & Van Belle (1998: 25).
Size: Maximum length 85 mm (Reid & Osorio 2000). Body outline: Elongate oval,moderately high elevated, subcarinated dorsum. Color: Variable but generally greyish, orblackish purple. Valves: Head valve semicircular, with straight posterior valve marginunnotched in middle. Intermediate valves broadly rectangular, with distinct protrudingapex and concave posterior valve margins. Lateral area hardly elevated, but clearlyindicated by faint depression in front of diagonal ridge. Jugal area weakly developed, butshowing partly a more or less distinct keel, especially in the more posterior intermediatevalves. Tail valve with centrally situated, forward-directed, and slightly elevated mucro,straight antemucronal area and rather steep, straight postmucronal slope. Jugal area of tailvalve extending towards anterior. Tegmentum without sculpture, except for growth marksand faint radial striations on terminal valves and lateral areas. Radial rows of ocellisituated on terminal valves, as well as on anterior region of lateral zones.Articulamentum: Solid, thickened, white with a hue of brown or red under mucro orapical regions. Apophyses rather long, rectangular (in intermediate valves), to trapezoidalin tail valve. Apophyses connected by well-developed, strongly serrated jugal plate.Insertion plates long, with pectinated outside. Slit formula: 8 / 1 / 11–12. Slits deep, teethwith rather sharp edges. Slit rays present in all valves. Perinotum: Wide and fleshy,appears naked. Dorsally with small elongate oval calcareous spicules showing finestriation at distal end, minute smooth and slender spicules, and corneous processesoccurring randomly. Ventrally short rectangular to squarish scales, arranged in radial rows;theses scales, slightly bent and showing distinct radial sculpture. Marginal short fringe ofminute scale–like spicules. Ctenidia (ZSM Moll 20040973, specimen measuring 15.4 x8.6 mm): 39 ctenidia on each side of foot, arranged holobranchially and adanally. Radula(same specimen): 5.6 mm long, 2.4 mm of which taken up by radula cartilages. 62 teethrows, 49 of them mineralized. Extremely slender central tooth showing forward-bent,obtuse, simple cutting edge. First lateral tooth noticeably longer than central one, withdeeply notched distal end. Base of first lateral moderately extended, with wing-likeextension covering lowermost part of central tooth. Second lateral tooth long with sharplykeeled shaft and having discoidal unicuspid head with sharp edge. Major uncinal toothspoon-like.
Material: Tonicia atrata is commonly found within the fjord at virtually all stations(see Table 1). According to Reid and Osorio (2000), the species ranges bathymetricallyfrom the low eulittoral to a depth of 10 m. The specimens reported here were foundbetween 1.5–36 m depth.
Distribution: Tonicia atrata occurs between 40° and 54°S along the Chilean coast, at
1341ZOOTAXATierra del Fuego, and around the Falkland Islands (Reid and Osorio 2000, and material
from ZSM).
FIGURE 14. Nuttallochiton martiali (de Rochebrune in de Rochebrune & Mabille, 1889) in situ(NRS), at station 7. 15. Underwater photograph of Chiton magnificus Deshayes, 1827 in situ(NRS), at station 7. 16. Underwater photograph of Tonicia calbucensis Plate, 1897 in situ (NRS), atstation 7. 17. Underwater photograph of Tonicia chilensis (Frembly, 1827) in situ (NRS), at station7. 18. Underwater photograph of Tonicia atrata (Sowerby, 1840) in situ (NRS), at station 11. 19.Underwater photograph of Plaxiphora aurata (Spalowsky, 1795) in situ (ZSM Moll 20040961), atstation 7, illustrated specimen measures c. 24 mm in length.
1341ZOOTAXA Remarks: Plate (1901) described Tonicia atrata as hosting the simple unicellular
parasite Chitonicum simplex Plate, 1898. Unfortunately, the systematic position of thisparasite is unknown and no further work has been done to evaluate Plate’s findings.
Tonicia lebruni var. calbucensis; Forcelli 1999: 186, illustrated.
Size: Maximum length 40 mm (Forcelli 1999). Body outline: Elongate oval, moderatelyelevated, subcarinated to slightly keeled (Figures 21–23). Color: Orange brown tobrownish red with darker radial streaks on terminal valves and lateral areas, on centralareas these streaks orientated longitudinally. Jugal area in general chestnut brown with twowider white streaks on both sides (Figures 21–26). Valves: Solid and smooth except forfaint growth marks arranged commarginally, more distinct at valve margins. Smallgranules partly extending along diagonal ridge. Head valve (Figure 24) semicircular withwide V-shaped posterior margin, weakly notched in middle. Intermediate valvesrectangular, straight posterior and anterior valve margins parallel, but anterior valvemargin extends anteriorly in valve ii. Apices slightly protruding. Lateral areas slightlyelevated and clearly indicated by different arrangement of brownish streaks, radially inlateral areas, longitudinally in pleural areas (Figure 25). Semicircular tail valve (Figure 26)with narrow antemucronal area, mucro elevated but directed backward. Mucro situated infront of valve middle. Postmucronal slope steep and straight. Ocelli on radial streaks oflateral areas and terminal valves only (not in white zones in between). Articulamentum:White and strongly developed. Centrally with a brownish spot. Apophyses solid,moderately large, triangular on valve ii, rectangular-trapezoidal on remaining valves(Figures 25–26). Apophyses connected by short sawed jugal sinus, laterally deeplynotched. Slit formula: 8 / 1 / 8 (9 / 1 / 9 in original description), teeth rather short but wide.Teeth strongly pectinated on outside. Slit rays present in all valves. Perinotum: Very wideand fleshy. Dorsally covered with minute conical spicules (appears naked), which aresmooth and sharp-pointed, round in cross section (Figures 27–28). Ventrally with radialrows of roundish to squarish scales, rounded at their free end. Scales not imbricated.Radial rows always interrupted. Scale arrangement resembles that of short pearl necklets(Figure 29). Ctenidia (specimen 28.8 mm body length): 41 ctenidia on each side of foot,arranged holobranchilly and adanally, group of largest ctenidia situated beneath valves vi-vii. Radula (same specimen): Radula length 9.4 mm, radula cartilage 2.9 mm in length; 66
1341ZOOTAXAteeth rows, 55 already mineralized. Central tooth slightly depressed in middle, slender,
with simple inward-directed blade. First lateral tooth elongate, widened at base, on itsupper end directed inward with simple blade, latter slightly notched in middle. Head ofsecond lateral tooth discoidal, with slightly extended side margins and obtusely pointed tipof cutting edge. Major lateral tooth spoon-shaped and smooth (Figure 30).
Material: Thirty-four specimens were collected from 4 stations within the fjord,covering a bathymetric range from 5 to 30 m depth (see Table 1).
Distribution: Tonicia calbucensis occurs from Puerto Montt southwards to PuntaArenas in the Straits of Magellan, from 0 to 35 m depth (Thiele 1908).
Remarks: Besides the specimens cited above, and the lectotype (Natural HistoryMuseum Berlin [ZMB] Moll 102.006, Figures 21–23), material from additional localitiesbetween Puerto Montt and Punta Arenas (ZSM) was examined. Specimens from thesamples observed showed consistent valve shapes and shell coloration.
Tonicia calbucensis was synonymized with Tonicia lebruni de Rochebrune, 1884(Figure 20) by Leloup (1956). He interpreted a small specimen of T. lebruni with similarcoloration, perinotum elements and radula to refer to Tonicia calbucensis. Externalexamination of two dry, flat preserved syntypes of T. lebruni (Muséum National d'HistoireNaturelle, Paris, France [MNHN]) show them to reach approximately 48 mm in length,having all valves in situ, and being chestnut with a shiny surface. Comparison betweentype samples of T. calbucensis (Figures 21–23) and T. lebruni (Figure 20) reveals anumber of differences: 1) the head valve has a much steeper slope in T. lebruni, 2) theapices in T. calbucensis are hardly protruding in the first two intermediate valves, whilethey protrude in all valves of T. lebruni, 3) dorsally T. calbucensis is more carinated than T.lebruni, 4) the lateral areas are defined more clearly in T. lebruni and have an anteriorlyshallow slope, while the diagonal ridge in T. calbucensis is elevated immediately abovethe anterior slope, 5) T. lebruni has uniformly commarginal striations on the central area,while this region is longitudinally striated in T. calbucensis, 6) the postmucronal slopeappears lesser steep in T. calbucensis. These characters are consistent with the newlycollected specimens, and intermediate forms were not observed. This leads us to reinstateT. calbucensis as distinct from the sympatric T. lebruni. Sirenko (2006b) also underscoredvalve and perinotum characters and came to the same conclusion.
Tonicia chilensis (Frembly, 1827) sensu lato(Figures 8, 11, 17)
Chiton chilensis Frembly, 1827: 204–205, suppl. pl. 17, fig. 8.
The entire genus, especially this species, is in an urgent need of revision, precluding a listof synonyms.
Size: Maximum length 70 mm (Reid & Osorio 2000). Body outline: Broad oval,
1341ZOOTAXA rather low elevated and subcarinated. Color: Variable, generally pale pinkish, yellowish-
orange to brownisch tones occur, interrupted by darker maculations on some specimens.Valves: Head valve semicircular with straight posterior valve margin unnotched in middle.Intermediate valves rectangular with concave posterior valve margin at both sides ofprotruding valve margin. Lateral areas slightly elevated and jugal area with more or lessdistinct keel. Tail valve nearly elliptical; central mucro slightly elevated and directedforward. Postmucronal area straight and moderately steep. Valves sculpture consisting ofgrowth marks on terminal valves and lateral areas; micro-granulation on all valvesbecoming more distinct towards outer margins (especially in lateral areas), more or lessfaint striation in central areas. Ocelli occurring over terminal valves and from diagonalridge to middle part of lateral areas. Articulamentum: White and solid, forming welldeveloped insertion plates and round to trapezoidal apophyses; latter connected bydenticulated, laterally deeply notched jugal plate. Slit formula: 9 / 1 / 11. Slit rays presentin all valves. Teeth long and wide, strongly pectinated at outside. Perinotum: Thickcuticle with randomly arranged, short, deeply embedded scale-like spicules of differentsizes. Ventrally, radial rows of short, thickset, more or less pointed scales with faintstriation. Slender spicules of different sizes along margin. Radula (ZSM Moll 20034137,specimen 29 x 16 mm in size): 10.7 mm radula length, 5.3 mm radula cartilage. 64 teethrows, 52 with mineralized teeth. In general, radula resembling T. calbucenis, withfollowing exceptions: first lateral tooth lacking wing-like extensions covering centraltooth; cutting edge of second lateral tooth more thickened, tip more pointed in middle;major uncinal tooth more thickset. Ctenidia (same specimen): 37 holobranchial andadanal ctenidia on each side of foot.
Material: Twenty-one specimens were collected from 6 stations (see Table 1). In theinvestigated area the species was found in depths between 5 and 28 m.
Distribution: Tonicia chilensis occurs from Perú southwards to Tierra del Fuego, witha former known bathymetric range from 0–15 m (Leloup 1956, Reid & Osorio 2000).
Remarks: The list of nominal species that are united under Tonicia chilensis, as eithersubspecies, forms, or synonyms, is extensive (Leloup 1956, Forcelli 1999, Kaas & VanBelle 1998). The type material of T. chilensis was not located together with the otherFrembly types [personal communication, Kathie Way, Natural History Museum, London,March 2006]. Specimens from the coast between Callao, Perú and Valparaiso, Chile, thetype locality, were not available to the authors. Thus, the identification of specimens fromComau can only be tentative, since the genus Tonicia, especially T. chilensis, is in urgentneed of revision.
One of the specimens (ZSM Moll 20050025) was found close to an underwater springwith sulphurous water and was partly covered by aggregations of filamentous bacteria(Figure 8). Results of a forthcoming stable isotope analysis of this specimen will showwhether the bacteria live around and on the chiton, or whether the chiton was feeding on it.
Tonicia smithi Leloup, 1980: 5–7, text-figs. 2–5, pl. 1, fig. A.; Kaas & Van Belle 1998: 172; Sirenko& Gallardo 2005: 89; Sirenko 2006b: 85, fig. 9.
Size: Maximum length 56 mm (ZSM Moll 20050456). Body outline: Slender oval, ratherflat, subcarinated to carinated. Color: Bright- to chestnut-brown, mainly with bluish orwhitish triangular dots arranged in terminal valves and lateral areas. Valves: Tegmentumsmooth, except for growth marks. Head valve semicircular, posterior margin widely V-shaped, unnotched or with small beak in middle. Intermediate valves rectangular, withprotruding apex and straight posterior margin (but widely V-shaped). Jugal area anteriorlywider than anterior valve margin. Jugal area not keeled, but clearly elevated, becomingmore elevated toward posterior valve. Lateral areas not elevated, but indicated througharrangement of ocellis restricted to anterior half of lateral areas. Tail valve withsemicircular posterior margin and backward-directed anterior margin. Mucro swollen,situated in middle of valve. Posterior slope slightly concave, rather flat. Articulamentum:Solid, white with brownish hue in centre, slit formula: 8 / 1 / 11, slit rays present in allvalves. Teeth long and with sharp edges. Strongly pectinated outside. Apophyses verylarge, rectangular or trapezoidal. Connected with a long, strongly sawed jugal platenotched on both sides. Perinotum: Very fleshy, appearing naked, dorsally covered withmicroscopic fine irregular calcareous corpuscles deeply embedded in cuticle. Isolatedrandomly arranged hook-like spicules all over the dorsal perinotum. Darker spicule tipssharply pointed. Ventrally, radiating rows of non-imbricating squarish scales, faintlystriated, one side straight, obtusely rounded on the other. Thick perinotum bridges betweenvalves; bridges becoming wider with age. Ctenidia (ZSM Moll 20050456, 56 mm body
length): 48 ctenidia on each side of foot, groups of largest ctenidia situated under 6th and 7th
valves. Radula (same specimen): 15 mm radula length, 3.8 mm account for radulacartilage. 59 teeth rows, 45 already mineralized. Central tooth rather short, slender andrectangular; blade simple and directed inward. First lateral tooth double size of centralone; shaft slender and parallel-sided. Blade simple and inward-directed, wider than shaft.Head of second lateral tooth with elongate-oval blade, with simple sharp edge, pointed inmiddle. Major uncinal tooth spoon-shaped.
Material: One specimen each, from stations 4 and 12, was collected between depthsof 19 and 25 m (see Table 1).
Distribution: Along the Pacific coast of South America from 38°S southwards via theStraits of Magellan to the Falklands with a bathymetric range of 3–21 m (Leloup 1980;Sirenko 2006b).
Chiton auratus Spalowsky, 1795: 88, figs. 6a–b.Detailed bibliography and synonymy in Kaas & Van Belle (1994: 266).
Size: Maximum length 110 mm (ZSM Moll 20060497). Body outline: Oval, moderatelyelevated, dorsally subcarinated. Color: Varying from greenish to blackish brown, withlongitudinal streaks on most specimens, commarginal marks or other different colorationof brighter tones. Jugal area whitish in most species. Valves: Eroded or encrusted in mostspecimens; tegmentum rather smooth with fine streaks on younger animals. Head valveless than semicircular, with unnotched, widely V-shaped posterior margin. In subadultspecimens more or less distinct radial ribs visible. Intermediate valves rectangular withslightly protruding apex and concave posterior margin. Lateral areas, although notelevated, clearly indicated by distinct diagonal ridge and smaller posterior rib. Tail valverather depressed, oval with nearly terminal mucro, with vague posterior sinus in a fewspecimens. Growth marks arranged commarginally in all valves. Articulamentum:Strong, bluish green, forms rounded to trapezoid apophyses, slit formula: 8 / 1 / 0 (callus),slit rays weakly developed, teeth sharp and long. Perinotum: Fleshy, dorsally coveredwith randomly (but in all sutures) arranged tufts of long (up to 8 mm) corneous hairs.Otherwise densely beset with minute, reddish-brown, blunt-tipped calcareous spicules.Ventrally beset with minute straight spicules, longitudinally striated in upper half.Ctenidia (ZSM Moll 20034100, approximately 40 mm body length) 42 ctenidia on eachside of foot, arranged holobranchially and largest ctenidia situated posteriorly. Radula(same specimen): 10.9 mm long, with 50 teeth rows, 43 already mineralized. Radulacartilage 5.4 mm in length. Central tooth rather short, rectangular, frontally keeled, andwith deeply notched blade. First lateral tooth extended at its base; head very narrow, withan inward-directed simple blade. Second lateral tooth with squarish head with three largedenticles of equal length, but central one wider than outer ones. First seven anterior rowsof examined specimen have simple blades, without denticles, just sharp cutting edge. Fewheads with smaller fourth denticle on outside.
Material: Eight specimens were collected at station 7 between 0–10 m (see Table 1).
FIGURE 20. Tonicia lebruni de Rochebrune, 1884, dorsal view of one syntype in MNHN, anteriorat left (modified photograph kindly provided by Delphine Brabant, MNHN). 21–23. Toniciacalbucensis Plate, 1897, lectotype from Punta Arenas, Chile, from a depth of “8 Faden” [= 14.63 m](ZMB Moll 102.006). 21. Dorsal view of the intermediate valves, anterior at left. 22. Right lateralview, anterior at left. 23. Dorsal view of the last two valves, anterior at top. 24–26. Toniciacalbucensis Plate, 1897, dorsal view of a disarticulated specimen from station 7, from a depth of 20m (ZSM Moll 20050326), anterior at top. 24. Head valve. 25. Valve ii. 26. Tail valve.Scale bars: 20 = 5 mm; 21, 22, 24–26 = 2 mm; 23 = 1 mm.
Distribution: This circum-subantarctic distributed species is reported from Valparaísosouthwards to the Straits of Magellan, the Falklands, the Tristan da Cunha and GoughIslands, and from the Neozelanic Subantarctic Islands (Kaas & Van Belle 1994).Plaxiphora aurata is known to inhabit rocky shores where it lives on and under rocks,accepting sheltered and sometimes muddy situations (Reid & Osorio 2000, this study) Due
1341ZOOTAXA to its dorsal coverage of several sessile marine organisms (most often algae) it is well
camouflaged. It has also been recorded from holdfasts of Macrocystis. Bathymetrically itoccurs from 0–12 m (Reid & Osorio 2000).
Remarks: Reid & Osorio (2000) mentioned a certain tolerance regarding decreasingsalinity (salinity ranging from 15–31‰) for this species.The sample (ZSM Moll 20034106) contains two specimens; the smaller one has apolychaete deeply buried in the specimen’s cuticle between the valves.
Nuttallochiton Plate, 1899
Type species: Schizochiton hyadesi de Rochebrune in de Rochebrune & Mabille, 1889sensu Plate 1899, by original designation = Nuttallochiton martiali (de Rochebrune in deRochebrune & Mabille, 1889) fide Thiele (1906: 333).
Nuttallochiton martiali (de Rochebrune in de Rochebrune & Mabille, 1889)(Figure 14)
Tonicia martiali de Rochebrune in de Rochebrune & Mabille, 1889: H.139–H.140, pl. 9, figs. 8a–b.Detailed bibliography and synonymy in Kaas & Van Belle (1987: 199).
While evaluating the underwater pictures of Comau Fjord chitons we came across a singlespecimen (Figure 14) that, at first sight, strongly resembles Plaxiphora aurata. However,the figured specimen differs in the following characters: 1) P. aurata has long hairs at thedorsal perinotum side, while in N. martiali they are missing, 2) N. martiali has 8prominent radial ribs on the head valve, whereas in P. aurata the head valve is only weaklysculptured, 3) radial ribs on lateral areas of N. martiali are wider and more strongly raised;in contrast they are moderately raised, widely separated and narrow in P. aurata, 4) whilethe pleural areas are smooth in P. aurata, longitudinally to obliquely arranged folds occurin N. martiali, 5) the dorsum is obviously stronger carinated in N. martiali, and 6) apicesare less prominent in N. martiali, while in P. aurata the posterior valve margin is convexon both sides of the protruding apex.
Unfortunately there is no reference material of this single specimen from station 7 (15m depth) available, and we failed to find more specimens. However, a careful comparisonof the illustrated specimen with an approximately 42 mm long specimen, from the CanalBetecoi (43°56’S 73°49’W), collected in a depth between 8–13 m (ZSM Moll 20050419),leaves no doubt of its correct identification.
Although Kaas & Van Belle (1987) considered Nuttallochiton martiali to be “rathercommon”, it is obviously rare along the southern Chilean coast. Neither the LundExpedition (Leloup 1956) nor the extensive sampling efforts in the Chonos Archipelago(Reid & Osorio 2000, Osorio et al. 2002, Osorio & Reid 2004) found Nuttallochiton
1341ZOOTAXAmartiali in this area. According to Sirenko’s (2006b) observation, Nuttallochiton martiali
is a “rather rare species”, bathymetrically ranging from 0–92 m. The photograph of aliving specimen from Comau Fjord is the northernmost record of N. martiali.
TABLE 1. Species and specimens collected by station.
Station no. Depth in m L. medinae I. pusio C. magnificus T. atrata T. calbucensis
1 5–30 4 1 1
2
3 6–39 5 8 7
4 3–25 1 2 2 3
5 3–17.5 3
6 2–20 1
7 0–28 9 14 12
8 10–12 3
9
10
11 6–36 2
12 19
Total specimen number per species
1 6 14 34 23
Station no. Depth in m T. chilensis T. smithi P. aurata TotalSpecimen no. per station
FIGURES 27–30. Tonicia calbucensis Plate, 1897, disarticulated specimen from station 7, from adepth of 20 m (ZSM Moll 20050326). 27–28. Spicules of the dorsal perinotum, in situ. 29. Ventralperinotum scales, in situ. 30. Anterior portion of the radula, showing central and inner lateral teeth.Scale bars: 27–29 = 10 µm; 30 = 100 µm.
Discussion
Altogether, 109 chiton specimens were collected between the depths of zero to 39 m,examined in the laboratory, and identified (Table 1). According to our survey, the ComauFjord region is inhabited by at least nine species of Polyplacophora. Its polyplacophorandiversity is thus comparable to the Estero Elefantes and Laguna San Rafael area fromwhere nine species also were reported (Reid & Osorio 2000). As expected because theshort geographic distance and similarly protected hydrographic situations, there isconsiderable faunal overlap. Tonicia smithi, Tonicia calbucensis and Nuttallochitonmartiali were found at Comau Fjord but were not mentioned by Reid and Osorio (2000).On the other hand, Ischnochiton stramineus (Sowerby in Broderip & Sowerby, 1832),Chaetopleura peruviana (Lamarck, 1819) and Chiton granosus Frembly, 1827 werereported by Reid & Osorio (2000), but were not observed in Comau Fjord.
1341ZOOTAXAIn his revision of Chilean chitons, Leloup (1956) reported a few additional species
from the area between Puerto Montt and the Chonos Archipelago. Specifically, herecorded Callochiton puniceus (Couthouy MS, Gould, 1846), Stenosemus exaratus (G.O.Sars, 1878) and Chiton cumingsii Frembly, 1827 from the Gulf of Ancud. Callochitonpuniceus has a bathymetric range from intertidal to a maximum depth of 300 m (Kaas &Van Belle 1985b), and S. exaratus lives between 100 and 2580 m deep (Kaas & Van Belle1990). These species were probably not found because sampling activities in Comau Fjordwere restricted to diving depths (0–39 m). In addition, the intertidal zone of Comau Fjordis strongly influenced by low salinity water that might not be tolerated by C. cumingsii,which is an intertidal species (Bullock 1988).
Sirenko & Gallardo (2005) reported 39 species of chitons from Chilean waters and ourresults from Comau only contains about 21% of those reported species. Sirenko (2006b)reported and partly illustrated 17 chiton species from the Magellan Strait. With theexception of Chiton magnificus and Tonicia chilensis, all of the species from Comau Fjordalso occur in the Magellan Strait.
It is likely that the number of chitons known from Comau Fjord will increase with alarger collecting effort, including additional sampling methods such as dredges andsamples from greater depths. The more exposed mouth of the fjord was not yetinvestigated in detail and could yield additional species. The special hydrographiccondition of Comau Fjord, with its thick LSL and high tidal amplitudes, might also limitthe occurrence and diversity of chitons, at least in the intertidal and upper subtidal areas ofthe inner fjord, which is influenced by brackish water. Species such as Plaxiphora aurata,which were formerly known to have a certain tolerance regarding salinity fluctuations(Simpson 1976), are found from the tide line downward. Other species such asIschnochiton pusio seem to submerge in the Comau system, with specimens only foundbelow the halocline at 5 m.
Chitons are well-known hosts for endoparasitic copepods (Franz & Bullock 1990,Nagasawa et al. 1991, Avdeev & Sirenko 1991, 1994, 2005), Sporozoa (Pixel-Goodrich1915, Ball & Neville 1979, Baxter et al. 1989), and monocellular parasites (Plate 1901).For the first time we report here the infection of a chiton by a nematode. In the mantlecavity of Chiton magnificus Deshayes, 1827, we found a cyst that contained severalspecimens of a nematode, and these were tentatively placed in the family Chromadoridae.It remains unsettled whether the cyst is a result of the infection or if the nematodespenetrated the animal secondarily (e.g., through a wound). Surprisingly, despite the highinfestation rates by copepods of Chilean nudipleuran gastropods (Schrödl 2002) there areno records of copepod parasitism on chitons in Chilean waters (Avedeev & Sirenko 2005).
We do report, for the first time anywhere, that two chitons were found in the vicinityof a spring where water rich in sulphur gushes out surrounded by mats of bacteria. Thebacteria thrive in these conditions, covering the substrate (Figure 8). One of the chitonsfound there, T. chilensis, was even partially covered by filamentous bacteria. The
1341ZOOTAXA occurrence of bacteria on the chiton’s dorsal surface indicates that it has been more or less
permanently exposed to and, thus tolerates such warm and sulphur-rich waters. Anongoing isotopic analysis should reveal whether or not bacterial mats are normally eatenby this chiton. Future monitoring activities will hopefully provide more data on theecology of these sulphur-loving chitons (e.g. food preferences, spawning).
Acknowledgements
We thank the staff of the Huinay Scientific Station for great hospitality. Andrea Salmen,Roddy Foley and all other divers that helped collecting specimens are especiallyacknowledged. Field work was supported by a research stipend of the Fundación SanIgnacio del Huinay to MS. Part of the diving and travel expenses of RM and MS were
covered by the GeoBioCenterLMU, Munich. Dr. Nicola Reiff (Munich) is thanked for a firstidentification of the nematodes. Our special thanks go to Dr. Matthias Glaubrecht andFrank Köhler (ZMB) for the loan of the type material of Tonicia calbucensis and to Dr.Philippe Bouchet and Delphine Brabant (MNHN) for providing the photograph of Tonicialebruni. Dr. Douglas Eernisse (California State University, Fullerton; USA) and Dr. AlanBeu (Institute of Geological & Nuclear Sciences Lower Hutt, New Zealand) kindlypolished the English and provided helpful comments. This is publication number 12 of theHuinay Scientific Field Station.
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