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Polyplacophora: the Sesoko Gtation

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The malacological society of Japan VEN US Jour. MHIac.} Hn (Jap, - Vol. 5S, Nu. 1 c1996}/ 41 49 -vs mazanog= u 7 ti l K 4 twoi)ts - itimaptL ptideptkA ･ ( pan-E11i!;( ftcma j(4}!: J,!UKJI(A7mpt}ttpt) of Distribution of Four Species Acanthopteura in Sesoko Island, Okinawa' (Polyplacophora:Chitonidae) Eiji YosHIoKA and Yasuhiro NAKAsHIMA (Kobe Yamate Women's College, Nakayamate-dori 6, Kobe 650 and Faculty of Science, Kyoto University, Kyoto 606-Ol) Abstract: Horizontal and vertical distribution of chitons, Acanthopleura gemmata. A. have been investigated. In the horizontal aspect, toochooana.A. tenuispinosa and A. miles, in the sheltered-exposed A. distributes they have specific distribution gradation. gemmata all rock shores around the island. A. Ioochooana distributes almost al1 around the island area. A. tenuispinosa mainly distributes the most sheltered area. except the most exposed In the vertical aspect, their A, miies mainly distributes the most exposed area. habitats significant except between are mostly overlapping, but their mean height have difference is lower, that of A. A. tenuispinosa and A. mites. The mean height of A, gemmata toochooana is middle, those of A, tenuispinosa and A, miles are higher in their habitat counts together, those species have specific zone. Puttingthe horizontal and vertical a ¢ four `space sharing' the dimensions although their habitat area and range overlap in in twe the most cases. Introduction Ferreira (1986) reviewed the genus Acanthopleura elaborately, and surnmarized the distri- bution of Acanthqpleura spp. According to his article, the distribution of three species, A. gemrnata (Fig. 1-A), A. Ioochooana (Fig. 1-B) and A. mites (Fig. 1-D) spread to and redescribed Okinawa and its neighboring islands. In addition, Saito Yoshioka (1993) and revealed spreads from Amami and Okina- A. tenuispinosa (Fig1-C) that itsdistribution Wa to the Gulf of Thailand and Vietnarn. Sesoko Island is located 600 m distance from Okinawa Island, and surrounded by rock rock shores. Those four species of Acanthopleura, in fact, inhabit the upper-intertidal shore of the island and compose main part of its fauna. To date, some articles dealing have with fauna around Sesoko Island (Yamazato et al., 1974; Nakasone et al., 1974) ' Contribution No. 284 of the Sesoko gtation,Tropical Biosphere ResearchCenter, University of the Ryukyus NII-Electronic Library Service The malaoologioalmalacological societysooiety of Japan 42 VENUS ： Vo1 ．55， No ．1 （1996 ） Fig．1 Four species of Acanthopleura collected from Sesoko Island． ： A Agemmata ， B ： A ． looehooana ： ： miles ＝ ， C A ．tenuiSpinosa，D A ． ．（Scale bar 10 mm ） で 翩 仂 ’8 脚 ニ ヒ 瀬 底 島 採 集 され た Ac ρ 属 4 補 ．A ： オ ザ ラ ガ イ ，B ： リ ュ ウ キ ュ ウ ピ ザ ラ ガ イ ．C ： キ ク ノ ハ ナ ピ ザ ラ ガ イ ，D ： A ． miies ， ゴ ’ 127 52 E ．， で 26 chore ＼ 1 ＼ ｝ ＼ ノ Fig．2 Location of Sesoko Island and circumstances of study area ． − A F ： Points for investigation of vertical distribution，瀬底 島 の 位 − 置 と 沿 岸 地 形 の 概 略 ．A F： 垂 直 分 布 の 調 査 場 所 ． 一 NII-ElectronicN 工 工 Eleotronio Library Service The malacologicalsocietymalacological society of Japan Yoshioka.Nakashima: Distribution of Chitons in Sesoko Island 43 been written, but they paid little attention to upper intertidal animals. The aim of the present article is to reveal the detail distribution of them around Sesoko Island, and to compare their characteristics on horizontal and vertical distributions. Study area and methods Location of stucly area: The location and circumstances of study area are shown in Fig. 2. The island is mainly surrounded by rock shores and partially long and short sand beaches. The longest beach of the island (800 m) is in the north-west area. The island is surrounded by coral reefs all around the coast off shore. Distance from rock shore or sand beach to reef edge is the shortest at south-west (20 m) and the longest at southern- most (5oo m), and the distance is relatively longer at north rock shore and at north-west sand beach. There is no muddy tidal land and pebble beach around the island. Most chitons inhabit upper intertidal zone of upright rock walls on which rock shelf overhang. Herizontai distribution: On the daytime low tide on 18 and 19-August 1994, all inter- tidal rock shores around the island were observed. At 68 points of chiton's habitat, the number of individuals of each species in 2 m width of rock wall was recorded. The width of the rock walls was measured by a straight 1 m bar. So, small concaye and convex upright, were ignored from the wall width, Because the rock walls of these points stand the densities (nurnber per 2 m of the wall width) were not affected by the difference of the angle. vertical distri- Vertical distributio' n: On the daytime low tide on 2, 3 and 4-May 1995, bution of each species at 6 points around the island (Fig. 2. A-F) was recorded. Ten-meter string was strained at O.5 m height from mean tidal level. And the height of all chitons over and under the line was marked. The strict position of chiton was identified as the center of the 5th shell. The height of the line was yerified twice by measuring and compar- ing it with the height from the actual water level. Nishihira (1974a) confirmed that the tide-table at Naha can be used at Sesoko Island. Results Horizontal distribution: The occurrence and density of the four species around the island were shown in Fig. 3. A. gemmata occurred in high density at almost all the points searched. A. Ioochooana occurred around the island except on the south-west rock shore and occurred on the north-east and south-east to southernmost for 1,200 m, it densely rock shore. A. tenuispinosa appeared densely on the north-east rock shore, and fewer the individuals occurred on the north, east and south rock shore, but never occurred on west rock shore. A. mites occurred mainly on the south-west rock shore, and fewer individu- of als occurred on the north-west, south-east and southernmost rock shore. Coexistence A. tenuispinosa and A. miles was rarely observed. Jt:ertieal dtstribution: The occurrence and numbers of these four species in O.25 m in Fig. 4. A. zone of upper intertidal wall at the 6 points (A-F) were shown gemmata and A. Ioochooana occurred in all 6 points, A. tenuispinosa occurred in 4 points and All chitons appeared in the zone from MTL+ 1.25 m to A. miles occurred in 3 points. NII-Electronic Library Service The malacologicalsocietymalacological society ofJapanof Japan 44 VENUS: Vol. 55, No.1(1996) y"tX"IZ?;?... "gtpmZ/ez. A.gemmata A.Ioochoonna ''- "tl"rtW/ey.... "t"1".z A.tenujspinosa A.mi1es '･NJC' //X O 1-4 5--19 20- indiv, f2rm Fig. 3. Herizontal distribution and density of four species of Acanthopleura around Sesoko Island. vaasnJaelU!cDAcanthopleuva tt 4 mba)alg"l'-fi6' . MTL-O.25 m, and habiting zone of each species was mostly overlapping. These occur- rences and their densities fairly reflect the horizontal distribution which revealed in Fig. 3. The number of each species in each zone was totaled and shown in Fig. 5, and differ- ences of mean height between all species ¢ ombinations were examined by t-test. Mean height of A. gemmata was significantly lower than that of the other 3 species (p<O,Ol, p<O.Ol, p<O.Ol). Mean height of A. Ioochooana is significantly higher than that of A. NII-Electronic Library Service The malaoologioalmalacological societysooiety of Japan Yoshioka ・Nakashima ： Distribution of Chitons in Sesoko Island 45 A ．gemma ta ＋ ・m A B C F 肌 TL 巳o 3B 55 26 20 A ．loochooana ＋lm E 卜lTL 16 20 A tenu ユsp ．ヱnosa ・ ＋ lm A B C D E 馨 諍 ．． … M ［1． ＝ ，．．L ＿ ■ ・ 一 一 L …．∴ 20 A ． miles A B C E ー F 例 ー l 1 1 ー ユ ・ITLIL 皇．L − ＿ LL − ． L ー一 20 Sesoko Fig ，4 Vertical distribution of four species of Acantho ρleura in the selected 6 points around histogram ． The location of the Island． Total number of each species is shown in the each （ ． points A −F are shown in Fig ．2 ．） 瀬 底 島 周 辺 6 地 点 で の Acanthopieura 属 4 種 の 垂 直 分 布 ， ・ マ． 呼 ’ 4 ． ！OQ 称 、 吻 ％ 呪 ％ （b 丶 ％ 十 lm 齢 撫暦 ｝ITL L ＊ ＊ ＝ ガ ＊ ＊ − − Fig．5 The total nurnber （A −F）of each species in each zone ． Results of t test with which the differ the ence of mean height between an spe ¢ ies combinations was examined ， were shown at 榊 bottom ．6 地 点 を 合計 し た 垂 【A：分布 と 平均 高 の 差 の 検 定 結 果 ． （ ： p ＜ 0．01， NS ： p ＞ 05 ） 垂 ． 〃 〃 significantly lower than that of the other two species ＜ 0，01 ， ＜ 0．0 ） ge 1 lata ， and （p p No significance was detected （p ＞ 0．5）between mean height of the higher two species ，、4． tenu ’spin osa and ／ 4． mi ’es ． 一 NII-ElectronicN 工 工 Eleotronio Library Service The malacologicalsocietymalacological society of Japan VENUS: 46 Vol. 5S, No. 1 (1996) Discussion It is the general view that sea shore takes on gradual aspect according to the strength of surf (Morton and Miller, 1968; Tokioka et al. 1972), and some shore can be set in a situation in the gradation from exposed to sheltered areas.
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    Illustrated Summary of Chiton Terminology

    ©Zoologische Staatssammlung München/Verlag Friedrich Pfeil; download www.pfeil-verlag.de SPIXIANA 33 2 171–194 München, November 2010 ISSN 0341–8391 Illustrated summary of chiton terminology (Mollusca, Polyplacophora) Enrico Schwabe Schwabe, E. 2010. Illustrated summary of chiton terminology (Mollusca, Poly- placophora). Spixiana 33 (2): 171-194. The aims of the present paper are to summarize and offer a standard set of ter- minology used to describe morphological and partly anatomical (e. g. the radula) characters of Polyplacophora. To make the understanding of some previously misused terms easier, the identification and description of relevant parts of the animal are illustrated and discussed in context of additional literature. Enrico Schwabe, Bavarian State Collection of Zoology, Muenchhausenstr. 21, 81247 Munich, Germany; e-mail: [email protected] Introduction “An den Tentakeln des Kopfes befinden sich Riech- organe [On the tentacles of the head there are Chitons are a group of basal, exclusively marine olfactory organs.].” However, chitons do not have molluscs, which have not significantly changed cephalic tentacles at all, and certainly not olfactory their bauplan during more than 300 million years tentacles! of evolution. Their more or less solid, dorsal plates This short contribution intends to clarify the termi- have been preserved in numerous fossil records and nology of chitons and to present a detailed general allow researchers a direct comparison with living description of chiton morphology, to summarise for species, and accordingly there is a high number amateurs, students or scientists the present stage of described fossil and recent taxa. At present we of scientific knowledge of a fascinating group of count for about 930 recent species (see Schwabe animals.
  • Foraging Tactics in Mollusca: a Review of the Feeding Behavior of Their Most Obscure Classes (Aplacophora, Polyplacophora, Monoplacophora, Scaphopoda and Cephalopoda)

    Foraging Tactics in Mollusca: a Review of the Feeding Behavior of Their Most Obscure Classes (Aplacophora, Polyplacophora, Monoplacophora, Scaphopoda and Cephalopoda)

    Oecologia Australis 17(3): 358-373, Setembro 2013 http://dx.doi.org/10.4257/oeco.2013.1703.04 FORAGING TACTICS IN MOLLUSCA: A REVIEW OF THE FEEDING BEHAVIOR OF THEIR MOST OBSCURE CLASSES (APLACOPHORA, POLYPLACOPHORA, MONOPLACOPHORA, SCAPHOPODA AND CEPHALOPODA) Vanessa Fontoura-da-Silva¹, ², *, Renato Junqueira de Souza Dantas¹ and Carlos Henrique Soares Caetano¹ ¹Universidade Federal do Estado do Rio de Janeiro, Instituto de Biociências, Departamento de Zoologia, Laboratório de Zoologia de Invertebrados Marinhos, Av. Pasteur, 458, 309, Urca, Rio de Janeiro, RJ, Brasil, 22290-240. ²Programa de Pós Graduação em Ciência Biológicas (Biodiversidade Neotropical), Universidade Federal do Estado do Rio de Janeiro E-mails: [email protected], [email protected], [email protected] ABSTRACT Mollusca is regarded as the second most diverse phylum of invertebrate animals. It presents a wide range of geographic distribution patterns, feeding habits and life standards. Despite the impressive fossil record, its evolutionary history is still uncertain. Ancestors adopted a simple way of acquiring food, being called deposit-feeders. Amongst its current representatives, Gastropoda and Bivalvia are two most diversely distributed and scientifically well-known classes. The other classes are restricted to the marine environment and show other limitations that hamper possible researches and make them less frequent. The upcoming article aims at examining the feeding habits of the most obscure classes of Mollusca (Aplacophora, Polyplacophora, Monoplacophora, Scaphoda and Cephalopoda), based on an extense literary research in books, journals of malacology and digital data bases. The review will also discuss the gaps concerning the study of these classes and the perspectives for future analysis.
  • New Outlook on the System of Chitons (Mollusca: Polyplacophora)*

    New Outlook on the System of Chitons (Mollusca: Polyplacophora)*

    VENUS 65 (1-2): 27-49, 2006 Review New Outlook on the System of Chitons (Mollusca: Polyplacophora)* Boris Sirenko Zoological Institute of the Russian Academy of Sciences, Universitetskaya nab.1, St. Petersburg 199034, Russia; [email protected] Abstract: In order to build a natural classification of the chitons, a new approach is proposed that uses not only the shells, as usual, but also other suitable features including aesthetes, girdle, radula, gills, glands, egg hull projections, spermatozoids etc. Several previous classifications are discussed. A brief review of the evolution of the Polyplacophora is given and a new classification of the chitons is proposed. The roles of the articulamentum and the reductions in the tegmentum in chitons are discussed. The evolutionary line of the reduction of slits is shown for the superfamily Cryptoplacoidea. Specifically, the genera Hemiarthrum, Weedingia and Choriplax, which have unslitted valves, have been removed from the order Lepidopleurida and reassigned to the order Chitonida within the Cryptoplacoidea. Affinities of these and other genera within the Cryptoplacoidea are discussed. Keywords: Polyplacophora, taxonomy, evolution, articulamentum, reduction of tegmentum Introduction Creating classifications at its best is all about searching for phylogenetic affinities. The described natural system is a reflection of our ideas about affinities, expressed with the aid of a hierarchy of taxa. In the words of Darwin (1873): “...that Natural System is founded on descent with modification; - that the characters which naturalists consider as showing true affinity between any two or more species, are those which have been inherited from a common parents...all true classification being genealogical; - that community of descent is the hidden bond which naturalists have been unconsciously seeking...” For the early classifications of chitons, naturalists usually used a single or a few characters and their classifications were thus artificial.