JapaneseJapaneseSociety Society ofSystematicof Systematic Zoology

Proc. Japan. Soc. Syst. Zoul,, No. 42: 14-20. December 2S, 1990.

The First Zoeal Larva of the Gulfweed Crab Planes cyaneus DANA, 1851 (Crustacea: Brachyura: Grapsidae)

Kooichi KoNisHii) and Megumi MiNAGAwA2)

i' National Research Institute of Aquacutture, Nansei, Mie 516-Ol, Japan 2} Tokyo Metropolitan Fi,s'heries Experiment Station, Hachiio Branch, HachiJ'o-iima, Tokyo 100-l5, Japan

ABsTRAc'i' The first zeeal larva of the gulfweed erab, Planes cyaneus DANA, is described and illustrated for the first time. General morphology of the zeea closely resembles those of Planes zoeas in the prcvious descriptions. Larval features of the subfamity Grapsinae are also compared and discussed,

The gcnus Planes, ocean-drifting crabs which have a wide distribution, contains three species: P. marinus RA'rHBuN from the Indo-Pacific, P. cyaneus DANA from the West Pacific and I'. minutus LiNNEAus from the Atlantic (CHAcE, 1951, 1966; TAKEDA and KuRATA, 1977). We have, however, a little informa- tion on their life cycle, including larval phase. The zoeal ]arvae of Planes have been documented for two species based on laboratory-hatched material. HyMAN (1924) and LEBouR (1944) described first zoea of P. minutus. WEAR (1970) TV!egalopaFand gave a description of the prezoea and first zoea of P. marinus. samptes m P. mmutus juvcnlies have bcen studied mainly by rearing of plankton and P. cyaneus (LEBouR, 1944; MuRAoKA, 1973). In Japan, two Planes species have been recordcd: P. marinus and P. cyaneus (TAKEDA and KuRATA, 1977; MIyAKE, 1983), No zoeal morphology of P. cyaneus has been givcn, in spite of common spccies in Japan. This study gives 1) a larval description of P. cyaneus based on laboratory-hatched material, and 2) morphological comparison with zoca of previous describcd Planes species and among the subfamily Grapsinae.

Materials and Methods

Three ovigcrous femalcs wcre collected from floating seaweed off Hachijo- jima (33008'N, 139048'E) on 8 May 1989. Sizc of immature eggs in formalin- fixed condition was O.33 × O.37mm in mean value (N=50). One of the berricd crabs, 10.9 mm in carapace width, released first zoeas on the next day. Active zocas were fixed with 5% formalin and preserved. Terminology, tech- niques for dissection and drawings of the specimens are almost the same as in a previous paper (KoNisHi, 1989). The carapacc lcngth (CL) was mesially measured from the anterior border of the eye to the posterior border of the carapacc, and the total carapace length (TCL) from thc tip of the rostral spine to the tip of the dorsal spine. All setal arrangements are sequenced from pro-

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First Zoeal Larva of Planes cyaneus 15

ximal to distal. The spceimcns uscd in this study are deposited in the National Science Museum (Nat. Hist.), Tokyo, under accession number NSMT-Cr 10228.

Description of first zoeal stage Dimensions. CL=O.51-O.55mm (mean O,54mm, 9 specimens); TCL= 1.04-1.19 mm (mean 1.14 mm). Carapace (Fig. IA): Rostral and curvcd dorsal spines, no lateral spines; pair of short dorsolatcral setae near base of dorsal spine. Eyes sessile, large relative to overall size of zoea. Antennule (Fig, IB): Uniramous, ¢ onical process with 3 aesthetascs and 2 thin sctae. Antenna (Fig. IC): Uniramous, pointed spinous process with a vestigial exopod seta preximally; nearly as long as rostral spine; spinules progrcssively larger distally. Mandible (Fig. ID): Molar and welL-developed incisor processes; no palp. Maxittute (Fig, IE): Coxal endite with 6 plumose setae, basial endite with 5 stout plumose setae and 2 small knobs; ¢ ndopod 2-segmented bearing 1,5 (rarely 1,6) setae. MaxiUa (Fig. IF): Coxal and basial endites bilobcd with 5+4 and 4+4 2 long plurnose setae, respectively; endopod unscgmcnted, bilobed with plumose setae on each tobe; scaphognathite with 4 marginal soft plumose setae and a long posterior process. Maxittiped 1 (Fig. IG): Coxa bearing a short seta; basis with mcdial setae arranged 2+2+2+2; endopod 5-segmcnted with 1, 2, 1, 2, 5 setae; exopod unscgmented with 4 long natatory sctae at apex. Maxitliped 2 (Fig. IH): Coxa without seta; basis with 1+1+1+1 sctae; endopod 3-segmented with O, l,5 setae; exopod as in maxilliped 1. Abdomen (Fig. II): 5 somites plus bifurcated telson; one pair of postero- dorsal setae on somites 2-5; somitcs 3-5 with conspicuous posterior projections with bifurcatcd ridge; somite 2 with pair of lateral tubcrcles; somite 3 with pair of lateral tubercles directed slightly backward; somite 4 with pair of posteriorly directed latcral tubercles. Telson (Fig. II): Bifurcated, distal portion of furcae covered with fine setae; 3 pairs of spines on posterior margin and 2 short outer spines at base of each furca,

Discussion

Table 1 summarizes previous larval studics on Ptanes specics; as for the first zoeal stagc, descriptions are now given in all species of the genus Planes. Thc larval descriptions of P. minutus by HyMAN (1924) and LEBouR (1944) were, however, too brief to compare larval characters with the standards of modern larval study, such as dimensions and setations of appendagcs. We must, thcrefore, estimate some larval characters from their illustrations, although

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16 K. Konishi and M. Minagawa ;t..--=k 1 c x

B /A=F-]

'( /;:,T tsX

...t.S.tt l!i..tt- t

,r-r'tk'i' / /

f if,s･ew ･et...---- H /L G , Y " n"'/ itg..;lsssK ai･･#i LXxE.21-th."-.".tt"'fX t.;ttuLt]=tt x ." x"Ntxst'. i -.T- nd +.---.Sft-"llW. 6 w ,{

w-//' tt ,',K.Y -A

- I

e･xet{r:･:- - D,G,H .e}f s,C,E,F - (O,lmm)

Fig. 1. Ptanes cyaneus DANA, zoea 1 stagc. A, lateral view; B, antennule; C, antenna; D, mandible; E, maxillule; F, maxi]la; G, maxilliped 1; H, maxillipcd 2; I, abdomen and telson. Natatory setae on maxillipedal exopod are omitted. Scale bars=O.1 mm,

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First Zoeal Larya of Plahes cyaneus 17

Table 1. Larval descriptions in the genusPlanes.

Specieg Described stage(s>' Author --' P. minutus zoeal(L) HyMAN, lg2s P, minutus zoea1(L), megalopa (P), crab1(P!L) LEBouR, 1944 P, marinzas zoeal

P. cyaneus zoeal(L) 'pa'rentheses this study " The source of material is given in by'lhe followln'g a66reviations: L: laboratory-hatched (-reared), P: plankton sample,

Table 2. Comparison of main morphological characters among first zoeas of Planes.

P. minutus P. minutus P. marinus P. cyanezas (LEB9UR,1944) (WEAR, 1970) (thisstudy) ..(Sl.YM.A.N: -l.9.2.P.l ''---i.tt4L'i. - Dimension (mm) ? ? (i. oi' o. s7 (TcL) iSITcL) O. 49 (CL*) O. 51-O. 55 (CL) Carapace: -:- -1- restral spine + -- dorsal spine + + -I- + - - '- - lateral spine Antennule:

aesthetac 4' ? 4 3 Antenna: - exopod r n - -E- expodal seta + + + Maxillule: endopod 1,4" ? 1,52) 1,5 Maxilla: endopod 2-F2** ? 2+2 2-I-2

Maxilliped 1: basis 212･l･2[･2*' ? 2+2+2+2 2+2+2+2 endopod 1, 2, 1, 2, 5'" ? 1, 1, 1, 2, 5 t, 2, 1, 2, 5

Maxilliped 2: endopod O, 1,4- 5*' ? O, 1,5 O, 1,5 Abdomen: postero-lateral processes + + + + Telson: s.e-t-a.-.T-"r--.. 2.. 2 Louter ..1.i-- .. ..---2 -. -. -: +: present, absent, ?: no data, ' Estimated from the illustration. ** Complimented by WILSON (1980). 1) LEBOuR (1944) did not mention about her measurement method (CL or TCL ?). 2) 1,O,5 in WEAR's (1970) deseription.

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18 K. Konishi and M, Minagawa

WiLsoN (1980) complemented HyMAN's description of the P. minutus zoea Table 2 shows morphological comparison among first zocas of three Planes spccics. Main larval characters of P. cyaneus closely resemble those of P. marinus and P. minutus except that thc antennule and the maxillular cndopod. WEAR (1970) described 3-segmented endopod in P, marinus, but wc consider this condition of segmentation as 2-segmented, because the proximal scgment fused with the protopod. The number ef antcnnular aesthetascs is 3 in P. c)]aneus, whilc 4 in P. marinus and P. minutus. It is, howcver, possible the prcvious works counted the minute seta as aesthetascs. All of available morphological characters are identical in three species of Planeb'. Thus wc can hardly distinguish these zoeas, at least at the first stage within the genus Planes. On the othcr- hand, megalopas of P. minutus and P, cyaneus arc different in setation of thc uropod (MuRAoKA, 1973). In the subfamily Grapsinae, larval development has been documented in five genera: Grapsus (AiKAwA, 1937), Pachygrapsus (HyMAN, 1924; LEBouR, 19441 ViLLALoBos, 1971; ScHLoTTERBEcK, 1976; PAuLA, 1985), Planes (l.c.), Leptograpsus (WEAR, 1970), and Iliograpsus (FuKuDA, 1978). Most of thesc previous works on Iarvae show that the zoeas of the Grapsinae are closely rcsembte to each other, whereas they are distinguishable from those of other subfamilies, cspecially in the abdomen; grapsinid zoeas have a lateral tubercle and a postero-lateral projection on somites 3-5. General morphology of the zoeas of the Grapsinae may be summarized as follows:

1)2)3)no lateral carapacc spmes, antenna with vestigial exopod scta instead of exopod, endopod setations of maxillule, maxilliped 1 and maxMiped 2 are l, 5, 2+2, 1,2, 1,2,5 and O, 1,5, respcctivcly; setation of basis of rnaxil- liped 1 is 2+2+2+2, 4)5) abdomina] somitcs 3-5 with remarkable postero-lateral projections, telson with 2 short outer spines on outer margin. Two exceptional examples wcre presented in the grapsinid zoeas. AiKAwA (1937) describcd the first zoea of Grapsus tenuicrustatus (HERBsT) (under the name of G, grapsus L,) to have the antennal exopod and to lack the remarkable abdominal projections; this zoea is v ¢ ry similar to varuninid or sesarminid zoeas. In his prcliminary report, FuKuDA (1978) mentioned that thc first zoea of Iliograpsus pal"dicola (RATHBuN) also shows closc aMnity in Iarval characters to those of the Ocypodidac rather than the Grapsidae. Although morphology of the first zoea of Planes is now known in all the species, complete larval dcvelopment remains unknown. In future studies, the completing of larval series of the genus Planes would be beneficial for systematic study of the Grapsidae.

Acknowledgements

We are grateful to Dr. J.W, MARTiN, Los Angeles County Museum of Natural History, U.S.A., for critical reading of the manuscript. We acknowledge anonymous reviewers whese comments improvcd the manuscript cssentially. Our

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First Zoeal Larva of Planes cyaneus 19

National Sciencc Museum Tokyo also due to Dr ．M ．TAKEDA ， ， cordial thanks are ， for providing us helpful advice and information on adult taxonomy of Planes．

摘 要 ． 一 ・ ニ 小 西 光 （養 殖 研 究 所 ） 皆 川 恵 （東 京 都水 試 八 丈 分 場 ） オ キ ナ ガ レ ガ Plα nes

Cy α neus の 第 1 ゾ エ ア 幼 生 に っ い て

3 種 を 含 む オ キ ナ ガ レ ガ ニ 属 （Pla，nes ） の カ ニ は イ ワ ガ ニ 亜 科 の 中 で は 遊 泳 力 が 強 く， の で 。 沿 岸 で 普 通 に 見 られ る に もか か わ らず ， そ 生 活史 に 関す る 知 見 は 少 な く断 片 的 あ る

現 在 ま で に ゾ エ ア 幼 生 の 形 態 に つ い て は ，大 西 洋 の P ．minutUS （L ．）お よ び 南 太 平 洋 の

ン P ．m α rinus RATHBUN で 報 告 例 が あ り ， わ が 国 も含 め た イ ド 太 平 洋 域 に 分 布 す る オ キ

ナ ガ レ ガ ニ P ．ey α neus DANA の み が 未 記 載 で あ る 。 そ こ で 八 ．丈島 沖 か ら採 集 さ れ た 抱

の エ 卵 雌 よ り本種 第 1 ゾ ア を得 て ， 幼 生 形 態 の 記 載 を 行 う と 共 に 同 属 ， 同亜 科 お よ び 他 亜

科 と幼 生 形 質 を比 較 した ．本 種 の ゾ エ ア の 形 態 は 既 報 告 の 2 種 と は 区 別 し 難 い ． ま た イ ワ − ガ ニ 亜 科 内 で は こ れ ま で に 5 属 に お い て 幼 生 記 載 が あ る が ， オ オ イ ワ ガ ニ お よ び Jlio 一 9Tapsus plαudicola （RATHBUN ） の 2 例 を 除 い て は 互 い に 非 常 に 似 て い る ． 方 で 本亜

科 の ゾ ヱ ア は 特 徴 的 な 腹 節 形 態 に よ っ て 他 亜 科 の そ れ と 区 別 す る 事 が 可 能 で あ る ．

References

AIKAwA ， H ．1937 ． Further notes on brachyuran larvae． Rec ． ocecrnogr ． Wks ．ノa ρ an ， g ： 87− 162． ’ F ． A ．1951 ． The occanic crabs of the and 厂apsus ． 厂 o ‘ ．ひ ．∫． CHAcE ， genera Ptanes Pach ）g P nat Mus 101 ： ＿ ． ．， 65 103． Jbid 1966． Decapod crustaceans from Sし Helena lsland， South Atlantic． ．， 118 ： 622＿662． FuKuDA ， Y ．1978， Preliminary notes on recently obtained larvae of brachyuran Crustacea

Aitsu Marine Biological Station C α ’α 川 ぜ∫ 6 ： 10− 16 ln Iapanese of the sea around the ． ， ．（ ， with English summary ．） HYMAN ，0 ． W ．1924 ． Studies on larvae crabs of the family Grapsidae， Proc， U ．S．襯 ． − Mus ．， 65 ： 1 8． KoNIsH 匸 K 1989 Larval of the mud shrimp Upogebia Upogebia ma or ， ． ． dcvelopment （ ） ／ （DE HAAN ） （Crustacea： Thalassinidea： Upogebiidae ）． Bull． natl ． Res ． Jnst． A匂 uacult ．．

15 ： 1− 17 ． LEBouR ， M ．V ，1944． Larval crabs from Bermuda ． Zoo ’oglc α ， N ．y ．，29 ： 113 − 128 ． MIYAKE ， S． 1983． Iapanese crustacean decapods and stomatopods in color ． VoL II． Hoikusha Osaka ．261pp ．56pls ． ln Iapanese ． Brachyura， ， ， （ ） − MuRAoKA ， K ．1973 ． On the characters of the larva and the seasonal change of occur rcncc of the Sarga ∬ um crab ， Planes cyaneus DANA ． Bu 〃． Kanaga ｝槻 Pref． Mus ．，6 ： 45− 53 ln Japanese with English summary ．（ ， ．）

PAuLA J．1985 ． The first zoeal stages of Poly わ伽 5 ’卍ensleiv ’ LEAcH Ma a squinado HERBsT ， ， ／ （ ）， P α c 乃graps 〃 ∫ tnarmoratus （FABRIcIus）， and σ ω tangeri （EYDoux ） （Crustacea， Decapoda ， − Brachyura ）． 14r （i．ハ4us． Bocage Ser． B ，2 ： 137 147． ScHLoTTERBEcK ， R ． E ，1976 ． The larval devclopment of the lined shore crab ， Pac ／lygrapsus crassipes RANDALL ，1840 （Decapoda Branchyura ， Grapsidae） reared in the laboratory． ’

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Crustaceana, 30: 184-200. TAKEDA, M, and Y. KvRATA 1977, Crabs from the Ogasawara Islands IV. A collection made at the new volcanic island, Nishino-shima-shinto, in 1975. Buil. nat. Sci. Mus. (Zool.), 3: 91-111. ViLLALoBos, C.R. 1971. First zoeal stage of Pachygrapsus crassipes RANDALL. Revta BioL trop. IS: I07-113. WEAR, R.G, 1970. Life-history studies on rvew Zealand Brachyura. 4. Zoea larvae hatched from crabs of the family Grapsidae. N,Z. J. mar. freshw. Res., 4: 3-35. WiLsoN, K.A. 1980, Studies on decapod Crustacea from the Indian River region of Florida. XV. The larval development under laboratory conditions of Euchirograpsus americanus A, MILNE EDwARDs, 1880 (Crustacea Decapoda: Grapsidae) with notes on grapsid subfamilial larval characters. Bull. mar. Sci. 30: 756-775.

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