Table Of ContentZOOSYSTEMATICA ROSSICA
I S S N Zoological Institute, Russian Academy of Sciences, St Petersburg ▪ https://www.zin.ru/journals/zsr/
2410-0226
[online] Vol. 29(1): 87–92 ▪ Published online 12 June 2020 ▪ DOI 10.31610/zsr/2020.29.1.87
0320-9180
[print]
RESEARCH ARTICLE
Leptochiton tahitiensis sp. nov. (Mollusca: Polyplacophora: Leptochitonidae)
from the Society Islands, Polynesia
Leptochiton tahitiensis sp. nov. (Mollusca: Polyplacophora: Leptochitonidae)
с островов Общества, Полинезия
B.I. Sirenko
Б.И. Сиренко
Boris I. Sirenko, Zoological Institute, Russian Academy of Sciences, 1 Universitetskaya Emb., St Petersburg, 199034, Russia.
E-mail: [email protected]
Abstract. A new chiton species, Leptochiton tahitiensis sp. nov., is described from Polynesia. The new
species differs from other congeners in the structure of granules of tegmentum, in dorsal scales and teeth
of radula.
Резюме. Описан новый вид хитонов Leptochiton tahitiensis sp. nov. из Полинезии, который
отличается от других видов рода структурой гранул тегментума, дорсальными чешуйками и
зубами радулы.
Key words: chitons, Pacific Ocean, Tahiti, Leptochitonidae, Leptochiton, new species
Ключевые слова: хитоны, Тихий океан, Таити, Leptochitonidae, Leptochiton, новый вид
Zoobank Article LSID: urn:lsid:zoobank.org:pub:553092BA-13DE-45D2-95A2-9D3229936484
Introduction tonida. It includes more than 100 described spe-
cies (Kaas & Van Belle, 1985, 1987, 1990, 1994;
The Society Islands are located in the middle of Kaas et al., 2006; Saito, 1997, 2001; Sirenko,
the Pacific Ocean, far from the areas with the 2001, 2015, 2016, 2018; Sigwart & Sirenko, 2012;
greatest biodiversity, so we cannot expect a large and others).
number of species there. Indeed, near these islands The aim of this article is to describe another
only five species of chitons have been found: new species of the genus Leptochiton collected
Rhyssoplax perviridis (Carpenter, 1865), Lucilina near the Society Islands. The species is known
nigropunctata (Carpenter, 1865), and Plaxiphora from only a single specimen but possesses unique
kamehamehae Ferreira et Bertsch, 1979 near the morphological features.
Tahiti Island; Lucilina pacifica (Leloup, 1981)
and Weedingia mooreana Kaas, 1988 near the Material and methods
Moorea Island (Carpenter, 1865; Ferreira &
Bertsch, 1979; Leloup, 1981; Kaas, 1988; Kaas & Philippe Bouchet have loaned me the only spec-
Van Belle, 1990; Kaas et al., 2006). imen of the genus Leptochiton from Tahiti, collect-
The genus Leptochiton Gray, 1847 is the most ed by the French TARASOC (TARAva seamounts
widely distributed genus of the order Leptochi- and SOCiety Island) expedition in 2009.
© 2020 Zoological Institute RAS and the Author(s)
B.I. Sirenko. Leptochiton tahitiensis sp. nov. from the Society Islands
The body parts selected
for study under a scanning
electron microscope (SEM)
were boiled in 7% KOH for
five minutes, and then boiled
twice in fresh water. Then
several valves (valves I, V,
VII and VIII), half of the
radula and a portion of the
girdle were examined with a
FEI Quanta 250 SEM. The
rest of the radula and girdle
were dried and slide-mount-
ed in Canada balsam for ex-
amination under a light mi-
croscope.
The holotype of Lepto-
chiton tahitiensis sp. nov. is
deposited at NMHN.
The following abbrevi-
ations are used: MNHN –
Muséum national d’Histoire
naturelle, Paris, France;
ZIN – Zoological Institute,
Russian Academy of Scienc- Fig. 1. Leptochiton tahitiensis sp. nov., holotype. Dorsal view (A); lateral
es, St Petersburg, Russia. view (B).
Taxonomy
Note. In the holotype, all valves except seventh
and eighth are damaged. The specimen is now
Class Polyplacophora Gray, 1821
disarticulated and consists of the following parts:
Subclass Neoloricata Bergenhayn, 1955 SEM stubs of the valves I, V, VII, VIII, a part
Order Lepidopleurida Thiele, 1909 of the perinotum and radula; the slide-mounted
parts of the perinotum and radula; and a vial with
Family Leptochitonidae Dall, 1889
other valves.
Genus Leptochiton Gray, 1847 Diagnosis. Chiton of small size; valves low ele-
vated, subcarinated. Intermediate valves broadly
Type species: Chiton cinereus Montagu, 1803
rectangular. Tegmentum covered with flattened,
(non Linnaeus, 1767) = Leptochiton asellus (Gme-
oval granules arranged uniformly and quincun-
lin, 1791) fide Lovén, 1846, subsequent designa-
tion by Gray, 1847. cially; granules with fine concentric lines and
Distribution. Worldwide; Carboniferous–Re- eleven pores of aesthetes. Dorsal scales obtusely
cent. pointed, with eight or nine double ribs. Central
tooth of radula very short and strongly narrowed
Leptochiton tahitiensis sp. nov. in middle; major lateral tooth with sharply point-
(Figs 1–4) ed unicuspid head. Nine gills per side arranged
from valve VI to anus.
Holotype. Adult chiton (No. MNHN-IM-2007-
Description. Holotype small (body length
39265), French Polynesia, Society Islands, Tahiti
6.5 mm), valves low elevated (dorsal elevation
I sland, 17°47′S, 149°23′W, depth 450–720 m
(oceanogra phic cruise TARASOC, station DW 3489, 0.38 mm), subcarinated, not beaked. Colour of
23 Oct. 2009). tegmentum and girdle white.
88 ( Zoosystematica Rossica, Vol. 29, No. 1, pp. 87–92
B.I. Sirenko. Leptochiton tahitiensis sp. nov. from the Society Islands
Fig. 2. Leptochiton tahitiensis sp. nov., holotype. Valve I, dorsal view (A); valve VII, dorsal view (B); valve VIII,
dorsal view (C); half of valve V, ventral view (D); valve VII, sculpture of tegmentum in central area (E); valve VII,
rostral view (F); valve VIII, lateral view (G). Scale bars: 1 mm (A–D, F); 100 µm (E); 500 µm (G).
Head valve semicircular, with V-shaped poste- posterior margin nearly straight, not beaked; lat-
rior margin. Intermediate valves rectangular, short eral margins rounded; lateral areas slightly raised.
and wide. Their anterior margin slightly convex; Tail valve roughly triangular in outline, narrower
( Zoosystematica Rossica, Vol. 29, No. 1, pp. 87–92 89
B.I. Sirenko. Leptochiton tahitiensis sp. nov. from the Society Islands
Fig. 3. Leptochiton tahitiensis sp. nov., holotype. Dorsal and ventral scales (A); central teeth of radula (B, D);
dorsal scales (C). Scale bars: 100 µm (A, B); 50 µm (C, D).
than head valve; anterior mucro not prominent; mental areas with long needles (up to 150 ×
antemucronal slope slightly convex; postmucronal 17 µm) embedded in chitinous cups, in the shape
slope weakly concave. of “Ringschaftnadeln” sensu Thiele (1908). Mar-
Tegmentum uniformly sculptured with quin- ginal fringe composed of slender spicules, up to
cuncially arranged, flattened, oval granules; each 85 × 15 µm, with four or five longitudinal ribs.
granule with fine concentric lines; one megalaes- Ventrally, girdle covered with elongate, smooth
thete and ten micraesthetes around; all aesthete and bluntly pointed scales (up to 78 × 25 µm) be-
pores of approximately equal size. ing larger than dorsal scales.
Articulamentum weakly developed; apophyses Radula of holotype 2.5 mm long, with 43 trans-
small, widely separated, triangular in valves II– verse rows of mature teeth. Central tooth of rad-
VII, more or less trapezoidal in tail valve. ula very short, strongly narrowed in middle and
Girdle moderately wide relative to valves, with large rhomboidal base; major lateral tooth
about 0.5 mm wide near valve V, dorsally densely with sharply pointed unicuspid head.
covered with blunt pointed scales (80 × 46 µm) Nine gills on each side extending from valve VI
with eight or nine partly double ribs. Interseg- to anus.
90 ( Zoosystematica Rossica, Vol. 29, No. 1, pp. 87–92
B.I. Sirenko. Leptochiton tahitiensis sp. nov. from the Society Islands
this group by the smaller and
narrower central teeth of the
radula, by eleven aesthetes
in the tegmental granules
(vs five in L. mutschkeae
and six in L. taiwanensis),
and by eight or nine ribs on
the dorsal scales (vs two in
L. mutschkeae and 14–16 in
L. taiwanensis).
The new species is simi-
lar to L. gascognensis Kaas
et Van Belle, 1985 occurring
near Europe, in having the
narrow central teeth and the
unicuspid head of major lat-
eral teeth of the radula (Car-
mona Zalvide & Urgorri,
1999), but differs from it in
the quincuncially arranged
granules on the central area
of tegmentum (vs longitu-
dinal rows in L. gascogn-
ensis), by eleven aesthetes
in the tegmental granules
(vs five in L. gascognensis),
Fig. 4. Leptochiton tahitiensis sp. nov., holotype. Sutural needle (A); dorsal
and by eight or nine ribs on
scale (B); marginal spicule (C); ventral scale (D); central and first lateral teeth
of radula (E); heads of major lateral teeth of radula (F); aesthete group on cen- the dorsal scales (vs 14–16
tral area (G). Scale bar: 100 µm. in L. gascognensis).
Distribution. The species is known only from Acknowledgements
the type locality, Tahiti Island, depth 450–720 m.
I would like to thank Philippe Bouchet (NMHN)
Etymology. Named after Tahiti Island.
who gave me the opportunity to study the new spe-
Comparison. Leptochiton tahitiensis sp. nov.
cies, Mihael Blikshteyn (Portland, Oregon, USA)
has several unique features that are absent or rare
for polishing the English, Alexey Miroljubov (ZIN)
in other species of the genus. The new species has for his technical assistance with SEM and Galina
unusual granules with fine concentric lines; the Kuznetsova (ZIN), who prepared the digital plates.
central teeth of the radula are very short, strongly The present research was performed using equipment
narrowed in the middle and with the large blade of the Research Resource Center “Taxon” of ZIN.
and rhomboidal base; the tail valve is triangular in This work was supported by the State scientific pro-
gram “Taxonomy, biodiversity and ecology of inver-
shape. The new species is slightly similar to some
tebrates from Russian and adjacent waters of World
species of Leptochiton belknapi Dall, 1878 group
ocean, continental water bodies and damped areas”,
(L. taiwanensis Sirenko, 2018 occurring near Tai-
No. AAA-A19-119020690072-9.
wan and L. mutschkeae Sirenko, 2015 occurring
near Chile) (Sirenko & Sellanes, 2015), which
References
also have the quincuncially arranged granules on
the tegmentum, and the unicuspid head of major
Carmona Zalvide P. & Urgorri V. 1999. Description
lateral teeth of the radula. Leptochiton tahitiensis of two new species of Mollusca Polyplacophora
sp. nov. can be distinguished from the species of from the Iberian Atlantic coast: Leptochiton (L.)
( Zoosystematica Rossica, Vol. 29, No. 1, pp. 87–92 91
B.I. Sirenko. Leptochiton tahitiensis sp. nov. from the Society Islands
gascognensis Kaas and Van Belle, 1985 and L. (L.) Leloup E. 1981. Chitons de Tulear, Reunion, Maurice
compostellanum sp. nov. Iberus, 17(2): 97–107. et Tahiti. Bulletin de l’Institut royal des Sciences
Carpenter P.P. 1865. Descriptions of two species naturelles de Belgique, 53(3): 1–46, figs 1–22, pls
of Chitonidae from the collection of W. Harp- 1–4.
er Pease, Esq. Proceedings of the Zoological So- Saito H. 1997. Deep-sea chiton fauna of Suruga Bay
ciety of London, 33(1): 511–512. https://doi. (Mollusca: Polyplacophora) with descriptions of
org/10.1111/j.1469-7998.1865.tb02380.x six new species. National Science Museum Mono-
Ferreira A.J. &. Bertsch H. 1979. A new species of graphs, 12: 31–58.
chiton (Mollusca: Polyplacophora) from the Ha- Saito H. 2001. Chitons (Mollusca: Polyplacophora)
waiian Islands and Tahiti. Transactions of the San collected by the R/V Kotaka-Maru from Tosa Bay,
Diego Society of Natural History, 19(7): 75–84, figs western Japan, with descriptions of two new spe-
1–5. cies. National Science Museum Monographs, 20:
Kaas P. 1988. New species and a new genus of chitons 101–119.
(Mollusca: Polyplacophora) from Polynesian coral Sigwart J.D. & Sirenko B.I. 2012. Deep-sea chitons
reefs. Basteria, 52: 139–145, figs 1–30. from sunken wood in the West Pacific (Mollusca:
Kaas P. & Van Belle R.A. 1985. Monograph of living Polyplacophora: Lepidopleurida): taxonomy, dis-
chitons (Mollusca: Polyplacophora). Vol. 1. Order tribution, and seven new species. Zootaxa, 3195:
Neoloricata: Lepidopleurina. Leiden: E.J. Brill & 1–38. https://doi.org/10.11646/zootaxa.3195.1.1
Dr. W. Backhuys. 240 p. Sirenko B.I. 2001. Deep-sea chitons (Mollusca, Poly-
Kaas P. & Van Belle R.A. 1987. Monograph of living placophora) from sunken wood off New Caledonia
chitons (Mollusca: Polyplacophora). Vol. 3. Subor- and Vanuatu. In: Bouchet P. & Marshall B. (Eds).
der Ischnochitonina, Ischnochitonidae: Chaetopleu- Tropical deep-sea benthos. Volume 22. Mémoires du
rinae & Ischnochitoninae (pars), additions to Vols 1 Muséum national d’Histoire naturelle, 185: 39–71.
and 2. Leiden: E.J. Brill & Dr. W. Backhuys. 302 p. Paris.
Kaas P. & Van Belle R.A. 1990. Monograph of living Sirenko B.I. 2015. Shallow and deep-sea chitons of the
chitons (Mollusca: Polyplacophora). Vol. 4. Subor- genus Leptochiton Gray, 1847 (Mollusca: Polypla-
der Ischnochitonina: Ischnochitonidae: Ischnochi- cophora: Lepidopleurida) from Peruvian and Chil-
toninae (continued). Additions to Vols 1, 2 and 3. ean waters. Zootaxa, 4033(2): 151–202. https://doi.
Leiden: E.J. Brill. 402 p. org/10.11646/zootaxa.4033.2.1
Kaas P. & Van Belle R.A. 1994. Monograph of living Sirenko B.I. 2016. New, rare bathyal leptochitons
chitons (Mollusca: Polyplacophora). Vol. 5. Subor- (Mollusca, Polyplacophora) from the South and
der Ischnochitonina: Ischnochitonidae: Ischnochi- West Pacific. In: Heros V., Strong E. & Bouchet
toninae (concluded), Callistoplacinae; Mopaliidae. P. (Eds). Tropical Deep-Sea Benthos. Volume 29.
Additions to Vols 1–4. Leiden: E.J. Brill. 402 p. Memoires du Museum national d’Histoire naturelle,
Kaas P., Van Belle R.A. & Strack H.L. 2006. Mon- 208: 25–63. Paris.
ograph of living chitons (Mollusca: Polyplacopho- Sirenko B.I. 2018. A new small chiton (Mollusca:
ra). Vol. 6. Suborder Ischnochitonina (concluded): Polyplacophora) from Guadelupe. The Bulletin
Schizochitonidae; Chitonidae. Additions to Vols of the Russian Far East Malacological Society,
1–5. Leiden–Boston: E.J. Brill. 463 p. 22(1/2): 55–62.
Received 8 April 2019 / Accepted 2 June 2020. Editorial responsibility: P.V. Kijashko
92 ( Zoosystematica Rossica, Vol. 29, No. 1, pp. 87–92
