Apocepon pulcher Nierstrasz & Brender

Yu, Jianmei An Haiyan & Li, Xinzheng, 2006, A review of the genus Apocepon Nierstrasz & Brender à Brandis (Isopoda: Epicaridea: Bopyridae) parasitic on purse crabs (Decapoda: Brachyura: Leucosiidae) from Chinese waters, with description of a new species, Zootaxa 1199, pp. 1-17 : 3-11

Apocepon pulcher Nierstrasz & Brender à Brandis, 1930

( Figs 1–3 )

Apocepon pulcher Nierstrasz & Brender à Brandis, 1930: 9, text­figs 17–20 [Tsingtau, China, infesting Philyra pisum de Haan ]. — Shiino, 1934: 272 –273, text­fig 7, [Tomioka, Kanazawachô, Kanagawa­ken (near Tokyo), Japan, infesting P. pisum de Haan ]. — Shiino, 1936: 170 [Shimoda, Japan, infesting P. pisum de Haan ]. — Shiino, 1936: 185 –186 [Koajiro, Misaki, Japan, infesting P. pisum de Haan ]. — Shiino, 1939: 98 [Sioiri, Tomioka Bay, Amakusa, Kyûsyû, Japan, infesting P. pisum de Haan ]. — Shiino, 1958: 68 [Tomioka, Amakusa Island, Japan, infesting P. pisum de Haan ]. — Choe & Kwon, 1982: 260 [ Korea, infesting P. pisum de Haan ]. — Kim & Kwon, 1988: 207 –208, text­fig 5 [ Korea, infesting P. pisum de Haan ].

Material examined

Infesting Philyra pisum de Haan. EL500601, 7♀, 4♂, Shicheng Island , Liaoning province, 122°44”E, 39°48”N, 18 June 1950 ; EL631001, ♀, ♂, Cangkou , Qingdao, Shandong province, 120°19”E, 36°04”N, Yuheng Cui coll., 7 October 1963 ; EL640101, ♀, ♂, Cangkou , Qingdao, Shandong province, 120°19’’E, 36°04”N, Zhengang Fan, Jieshan Xu, Huilian Chen coll., 18 January 1964 ; EL630501, 2♀, ♂, Cangkou , Qingdao, Shandong province, 120°19”E, 36°04”N, Zhengang Fan, Xiubin Fang, coll., 22 May 1963 ; EL640901, ♀, ♂, Cangkou , Qingdao, Shandong province, 120°19”E, 36°04”N, 9 September 1964 ; EL510801, ♀, ♂, Cangkou , Qingdao, Shandong province, 120°19’’E, 36°04”N, 18 August 1951 ; EL641201, ♀, ♂, Cangkou , Qingdao, Shandong province, 120°19”E, 36°04”N, 21 December 1964 ; EL570501, ♀, Cangkou , Qingdao, Shandong province, 120°19”E, 36°04”N, Weiquan Zhang coll., 15 May 1957 ; EL500801, 2♀, 2♂, Cangkou , Qingdao, Shandong province, 120°19”E, 36°04”N, 15 August 1950 ; EL641001, 2♀, 2♂, Cangkou , Qingdao, Shandong province, 120°19”E, 36°04”N, 26 October 1964 ; EL630701, 2♀, 2♂, Cangkou , Qingdao, Shandong province, 120°19”E, 36°04”N, 23 July 1963 ; EL340701, 3♀, 3♂, Cangkou , Qingdao, Shandong province, 120°19’’E, 36°04”N, 25 July 1934 ; EL640401, ♀, Cangkou , Qingdao, Shandong province, 120°19”E, 36°04’’N , 15 April 1964; EL510801, 2♀, 2♂, Cangkou , Qingdao, Shandong province, 120°19’’E, 36°04’’N , 5 August 1951; EL581001, ♀, Cangkou , Qingdao, Shandong province, 120°19’’E, 36°04’’N , 14 October 1958; EL640201, ♀, ♂, Cangkou , Qingdao, Shandong province, 120°19’’E, 36°04’’N , 29 February 1964; EL521001, ♀, ♂, Xianren Island , Liaoning province, 122°53’’E, 39°56’’N , 2 October 1952; EL500501, 8♀, ♂, Chenjiacun , Liaoning province, 122°10’’E, 39°15’’N , 27 May 1950; EL570901, 3♀, 2♂, Huangdao , Shandong province, 119°45’’E, 35°50’’N , 9 September 1957; EL520801­1, 2 ♀, EL520801­2, 2♂, Lianyungang , Jiangsu province, 120°07’’E, 33°23’’N , 28 August 1952; EL500502, 4♀, 3♂, Zhuanghe , Liaoning province, 122°30’’E, 39°40’’N , 16 May 1950; EL550801, ♀, ♂, Dengying , Shandong province, 120°45’’E, 36°30’’N, Chongli Zhang coll. , 12 August 1955; EL810601, 6♀ (3 immature), 4♂, Xiaoqinghe , Shandong province, 119°40’’E, 36°30’’N, Yongliang Wang, coll. , 29 June 1981; EL560301, ♀, ♂, Zhujiajian , Zhejiang province, 120°28’’E, 29°32’’N , 16 March 1956; EL800601, ♀, ♂, Bohai Bay , 119°40’’E, 38°26’’N, Daoyuan Sun, Yincheng Liu coll. , 18 June 1980; EL740901, ♀, ♂, Qinhuang Island , 119°37’’E, 39°55’’N , 5 September 1974.

Infesting Philyra carinata Bell. EL530701, 2♀, ♂, Cangkou, Qingdao, Shandong province, 120°19’’E, 36°04’’N, Xiuji Zhang coll., 15 July 1953; EL510601, ♀, Cangkou, Qingdao , Shandong province, 120°19’’E, 36°04’’N, 8 June 1951 .

Infesting Philyra heterograna Ortmann. EL530601, ♀, ♂, Leqing, Zhejiang province, 120°30’’E, 29°25’’N, 9 June 1953.

Infesting Philyra sp. EL600701, 2♀, 2♂, Cangkou, Qingdao, 120°19’’E, 36°04’’N, 15 July 1960.

Description of reference female ( Fig. 1 ) (EL520801­1)

Head length 1.1 mm, head width 2.0 mm, maximal width across third pereomere 4.8 mm, pereon length 4.6 mm. All body segments distinct, slightly asymmetrical, distortion angle ~11º ( Fig. 1A, B ).

Head bilobate, frontal lamina short, eyes absent, posterior margin straight. Antenna 1 of three articles, antenna 2 of five articles with one terminal seta ( Fig. 1C ). Barbula with two simple falcate lateral projections on each side, outer lateral pair of projections larger than inner, median region with two obtusely angled convexities ( Fig. 1D ). Maxilliped with slightly curved, nonarticulated, pointed, setaceous palp and blunt plectron ( Fig. 1E, F ).

Pereon broadest across third pereomere, tapering gradually anteriorly and posteriorly. No middorsal projections on pereon. Pereomeres 1, 6 and 7 narrower than other pereomeres, lateral side of last pereomeres enlarged. Dorsolateral bosses on first pereomere prominent, tergal projections on second to fourth pereomere distinct and covering small dorsolateral bosses on respective pereomeres. Oostegites incompletely enclosing brood pouch ( Fig. 1B ), oostegite 1 smoothly round anteriorly, with digitate internal ridge, almost smooth margin posteriorly and blunt rounded posterolateral point ( Fig. 1G, H ). Oostegites 2–5 anteriorly smooth, posterior edge with setae, oostegite 4 largest. Pereopods essentially alike, one suture on ischia of every pereopods, carpus of pereopod 7 trapezoid, other carpi quadrate, and pereopods larger posteriorly ( Fig. 1I, J ).

Pleon cylindrical, pleon of 6 pleomeres, first 5 bearing biramous pleopods and digitate lateral plates ( Fig. 1 K–O), last four lateral plates exceed half­length of respective exopodite, lateral plates of first pleopod short (arrow indicate). Digitate margin of lateral plates and exopodites are similar and simple. Endopodite (gray in figure) of pleopod as rudimentary smooth linguiform protuberance, and endopods of 5 pleopods largest. Terminal pleomere with wide uniramous uropods with irregular margins directed posteriorly ( Fig. 1P ).

Description of reference male ( Fig. 2 ) (EL520801­2)

All body regions and segments distinct, head length 0.2 mm, head width 0.4 mm. Pereon length 1.9 mm, maximal width across pleon 4 0.8 mm, pleon length 1.6 mm, pleomere 1 width 0.7 mm, pleomere 5 width 0.5 mm ( Fig. 2A, B ).

Head suboval, wider than long, posterior edge straight, head narrower than first pereomere, without eyes. Antennae of three and five articles respectively ( Fig. 2C, D ), second antenna three times as long as antennae 1. Antenna 1 with tuft of 5 or 6 setae distally, second segment with approximately 4 setae, basal segment bearing a tubercle with 3 setae. Antenna 2 with terminal tuft of approximately 6 setae, second segment bearing 1 seta on distal edge, third segment bearing 3 setae on distal edge.

Pereon. Pereomeres 2–5 almost equally wide, with truncate margins, pereomere 4 slightly broader than others, all pereomeres deeply separated laterally. Pereomeres 1–7 without midventral projections. All pereopods subequal ( Fig. 2E ).

Pleon of 6 pleomeres, width of pleomeres 1–2 almost equal to pereomere 7, pleomere 1 with large prominent lateral extensions of pleomere 1, but without pleopods. Last four pleomeres with pair of small rudimentary tuberculiform pleopods on prominent lateral extensions of pleomeres. Without midventral projections, and last pleomere V­shaped with pointed extremity, no uropods.

Variation

Female. Other female specimens agree in all respects with the reference female except that the palps of maxillipeds in some specimens are shorter and blunter ( Fig. 3A ), the posterior margin of the head is cuspate in immature females ( Fig. 3B ), and sizes of the bodies varies. Head length 0.92–1.47 mm, head width 1.83­2.66 mm, maximal width across pereomere 3, and 4.33–5.96 mm, distortion angle 11–20º. Immature female ( Fig. 3 B–D) with empty brood pouch, whitish body, wider frontal lamina, pereon with medial nonarticulated ridge. Tergal projections not apparent, margin of lateral plates almost smooth, and the endopodites in immature females are relatively longer than those in mature females.

Male. Two forms found, first form compact as reference male, other form elongate, with pereomeres more deeply separated laterally ( Fig. 3E ). Range of male’s size, head length 0.20–0.26 mm, head width 0.39–0.48 mm, pereon length 1.77–2.21 mm, maximal width across pleon 4 and 5 0.73–0.88 mm, pleon length 1.32–2.03 mm, pleomere 1 width 0.61–0.73 mm, pleomere 5 width 0.36–0.51 mm.

Distribution

Qingtao, other regions of Shandong province, Liaoning, Jiangsu, Zhejiang, Bohai Bay, China; Kanazawachô, Kanagawa­ken (near Tokyo), Shimoda, Koajiro, Misaki, Sioiri, Tomioka Bay , Amakusa, Kyûsyû, Amakusa Island , Japanese waters; Songapto Island , Mungapto Island , Soyado Island, Chagykto Island, and several location on Korea .

Remarks

Nierstrasz & Brender à Brandis (1930) reported this species from Chinese waters. Shiino (1934, 1936, 1939, 1958) reported this species many times from Japanese waters, Choe & Kwon (1982) and Kim & Kwon (1988) reported it from several Korean locations. All previous descriptions of A. pulcher are incomplete, with some key characters not provided. This paper records two new hosts: Philyra carinata Bell and Philyra heterograna Ortmann.

Apocepon digitatum Stock, 1959

( Figs 4–6 )

Apocepon digitatum Stock, 1959: 30 –32, text­fig 3, pl. 1 [Siglap, Singapore, infesting Leucosia craniolaris (Herbst) ].

Material examined Infesting Leucosia sinica Shen et Chen, Huilian Chen , det. of host; EL615001, ♀, EL615002, ♂, South China Sea, Stn. 6150, 110°45”E, 21°15”N, 11 m, Guangzong, Wu, coll., 11 February 1960; EL615002, 2 ♀, 2♂, South China Sea, Stn. 6150, 110°45”E, 21°15”N, 14 m, Yongliang Wang coll., 29 January 1959 .

Description of reference female ( Figs 4 & 5 ) (EL615001)

Head length 1.3 mm, head width 1.4 mm, maximal width across pereomere 3 4.3 mm, pereon length 4.3 mm. All body segments distinct, slightly asymmetrical, distortion angle ~8º ( Fig. 4A, B ).

Head bilobate, frontal lamina short, eyes absent. Antenna 1 of 3 articles, antenna 2 of 5 articles setae absent. ( Fig. 4C ). Barbula with two lateral projections on each side, outer lateral pair of projections smooth and pointed, larger than inner, inner lateral projections digitate, median region with two blunt points that abut against inner lateral projections ( Fig. 4D ). Maxilliped with upright, nonarticulated, rounded, setaceous palp and pointed plectron ( Fig. 4E ).

Pereon broadest across pereomere 3, coxal plates visible on pereomeres 1–4. No middorsal projections on pereon, pereomeres 1, 2 and 7 narrower than other pereomeres. Dorsolateral bosses on pereomeres 1–4 prominent, tergal projections on pereomeres 2, 3 distinct and 4 smaller than the former ( Fig. 4B ). Oostegites almost completely enclosing brood pouch, oostegite 1 smoothly round anteriorly, with irregular simple digitate internal ridge, deeply crenulate margin posteriorly and bluntly crenulate posterolateral point ( Fig. 4F, G ). Oostegites 2–4 anteriorly smooth, posteriorly crenulate, oostegite 5 almost smooth ( Fig. 4H, I ). Pereopods 1–4 similar except ischia posteriorly larger, dactyli of pereopods 5–7 tightly embed into propodi, and there are three large spines on the carpus and merus of pereopod 5 ( Fig. 4 J–L).

Pleon of 6 pleomeres, first 5 bearing biramous pleopods and digitate lateral plates ( Fig. 5 A–E), last four lateral plates long, lateral plates of pereomeres 3–5 slightly shorter than respective exopodites, pereomere 1 with short lateral plates as long as its endopodites. Digitate margin of lateral plates and exopodite similar. Endopodites of pleopods 1–4 rudimentary and slightly digitate; endopodites of pleopod 5 long and digitate, half as long as their exopodites. Terminal pleomere with uniramous digitate uropods directed posteriorly ( Fig. 4A ).

Description of reference male ( Fig. 6 ) (EL615002)

All body regions and segments distinct, head length 0.2 mm, head width 0.4 mm. Pereon length 1.6 mm, maximal width across pereon 4, 0.7 mm, pleon length 1.3 mm, pleomere 1 width 0.6 mm, pleomere 5 width 0.5 mm ( Fig. 6A, B ).

Head suboval, rather narrower than pereomere 1, posterior edge round, eyes absent. Antennae of three and four articles respectively ( Fig. 6C, D ), antenna 2 longer than antenna 1. Antenna 1 with tuft of 5 setae distally, second segment with approximately 2 setae, basal segment bearing 3 setae. Antenna 2 with 5 terminal setae, second segment bearing 1 seta on distal edge, third segment bearing 3 setae on distal edge.

Pereon. Pereomeres 3–7 almost equally wide, pereomere 5 slightly broader than others, all pereomeres rather deeply separated laterally. Pereomeres 3–7 with midventral projections. All pereopods essentially similar ( Fig. 6E ), with small tubercles and two spines on propodus, one tubercle on the base of dactylus.

Pleon of 6 pleomeres, pleomere 1 almost equal in width to pereomere 7, only slightly tapering to pleomere 6. First five pleopods are reduced to small, pointed tuberculiform on lateral extensions of pleomeres. Pleomere 1 with square midventral projection, last pleomere U­shaped with round extremity, no uropods.

Variation Other specimens agree in all respects with the reference specimens except for variation in body size.

Distribution Siglap, Singapore; the South China Sea

Remarks This is only the second record of Apocepon digitatum , so its locality ( China) and the host ( Leucosia sinica Shen et Chen ) are new. Our materials conform well to the characters previously recorded for A. digitatum except for the tergal projections of pereomeres 2 and 3, which were notched in the type specimen ( Stock, 1959). This character varies among our specimens, so it cannot be considered of interspecific significance. Our redescription adds details about the female’s last four pleopods, oostegite 1, and the male’s ventral characters. In females, A. digitatum differs from A. pulcher in the structure of the first oostegite and the pleopodal endopodites. The last pleopods of the males are also different.

Figures

FIGURE 1. Apocepon pulcher Nierstrasz & Brender à Brandis. Reference female, EL520801­1. A, dorsal view. B, ventral view (except pleon). C, right antennae. D, barbula, right side. E, right maxilliped, external view. F, palp of right maxilliped. G, right oostegite 1, external view. H, same, internal view. I, J, right pereopods 1 and 7, respectively. K–O, right pleopods and respective lateral plates 1–5 (endopodites of pleopods in gray) (arrow indicates lateral plate 1). Scale = 2.0 mm for A, B; 0.38 mm for C, F; 0.80 mm for D, E; 1.31 mm for G, H, K–O; 0.64 mm for I, J.

FIGURE 2. Apocepon pulcher Nierstrasz & Brender à Brandis. Reference male, EL520801­2. A, dorsal view. B, ventral view. C, left antenna 1. D, left antenna 2. E, right pereopod 2. Scale = 1.0 mm for A, B; 0.06 mm for C, D; 0.12 mm for E.

FIGURE 3. Apocepon pulcher Nierstrasz & Brender à Brandis. A, right maxilliped (EL641001). B, immature female (EL810601), dorsal view. C, same specimen, ventral view. D, immature female (EL570501), dorsal view. E, dorsal view of male (EL740901). Scale = 0.75 mm for A; 1.0 mm for B–D; 0.67 mm for E.

FIGURE 4. Apocepon digitatum Stock. Reference female, EL615001. A, dorsal view. B, dorsal view except pleon. C, right antennae. D, barbula. E, left maxilliped. F, right oostegite 1, external view. G, same, internal view. H, I, right oostegites 2 and 5, respectively. J–L, right pereopods 2, 5 and 7, respectively. Scale = 2.0 mm for A; 1.66 mm for B; 0.41 mm for C, J–L; 1.50 mm for D, F, G; 0.81 mm for E, 1.30 mm for H, I.

FIGURE 5. Apocepon digitatum Stock. Reference female, EL615001. A–E, right pleopods and respective lateral plates 1–5 (endopodites of pleopods in gray). Scale = 1.6 mm.

FIGURE 6. Apocepon digitatum Stock. Reference male, EL615002. A, dorsal view. B, ventral view. C, left antenna 1. D, left antenna 2. E, right pereopod 3. Scale = 1.0 mm for A, B; 0.10 mm for C, D; 0.18 mm for E.