Asymmetrione globifera, An & Markham & Yu, 2010

An, Jianmei, Markham, John C. & Yu, Haiyan, 2010, Description of two new species and a new genus of bopyrid isopod parasites (Bopyridae: Pseudioninae) of hermit crabs from China, Journal of Natural History 44 (33 - 34), pp. 2065-2073 : 2066-2068

Asymmetrione globifera sp. nov.

( Figure 1 )

Material examined

Infesting Dardanus hessii (Miers, 1884) . Det of host, Yongliang Wang. Holotype: Beibu Gulf, Stn 6271, 19°00′ N, 106°30′ E, 44.7 m, 11 February 1960, Coll. Zhengang Fan, one female, CIEA627101 . Allotype: Beibu Gulf , Stn 6271 , 19°00′ N, 106°30′ E, 44.7 m, 11 February 1960, Coll. Zhengang Fan, one male, CIEA627102 . Paratypes: Beibu Gulf , Stn 6251 , 19°45′ N, 107°30′ E, 51.5 m, 4 December 1959, Coll. Xiutong Ma, one female, CIEA625101 , one male, CIEA625102 . Beibu Gulf , Stn 6264 , 18°30′ N, 107°00′ E, 62 m, 25 May 1960, coll. Fuzeng Sun, one female, CIEA626401 . one male, CIEA626402 . Woody Island , 16°50′ N, 112°20′ E, 17 May 1957, one female, CIEA570501 .

Infesting Spiropagurus sp. South China Sea, Stn 6159, 18°45′ N, 110°30′ E, 31 m, 6 May 1960, Coll. Shoupeng Shen, one female, CIEA615901 .

Description of holotype female (CIEA627101) ( Figure 1A–I )

Length 7.51 mm, maximal width 17.1 mm, head length 2.18 mm, head width 2.91 mm, distortion 98°, dextral, body outline nearly oblong. All body regions and segments distinct. No pigmentation ( Figure 1A,B ).

Head subcircular, with large frontal lamina, its posterior margin irregularly six-lobed. Eyes absent ( Figure 1A ). Antennae of three and five articles, respectively ( Figure 1C ), setae not evident. Each side of barbula ( Figure 1D ) bearing two slender, pointed large falcate projections laterally and three pairs of irregular digitate projections medially. Maxilliped ( Figure 1E ) subtrapezoidal, its anterior article much larger than posterior; anterior article lacking palp but produced into anteromedial corner; posterior article with tiny sharp plectron.

Pereon distinctly segmented, pereomeres 4–6 sharply convex anteriorly. Dorsolateral bosses on left sides of pereomeres 1–4 and on right sides of pereomeres 1–5. Prominent tergal projections on right sides of pereomeres 1–5. Oostegites completely enclosing brood pouch; first oostegite ( Figure 1F,G ) with articles of nearly equal lengths, outer groove deep and conspicuous, internal ridge medially bearing four straight projections with digitate margins, posterolateral point sharp. Pereopods about equal in size, all articles distinct; all propodi large, each produced into deep distal socket receiving tip of curved dactylus ( Figure 1H ).

Pleon of six distinct pleomeres, first five bearing lanceolate lobed lateral plates on both sides, surfaces of which conspicuously tuberculate. Five pairs of biramous pleopods, their exopodites of shape and size similar to that of lateral plates, endopodites of first four pairs slightly broader than respective lateral plates and exopodites, all of these rami conspicuously tuberculate ( Figure 1I ). Lateral plates of fifth pleopods and uropods small and globose, nontuberculate.

Description of allotype male (CIEA627102) ( Figure 1J–N )

Length 5.5 mm. maximal width, across pereomere 4, 1.6 mm, head width 1.1 mm, pleon length 1.5 mm; outline narrowly elliptical. All body regions and segments distinct. No pigment except eyes ( Figure 1J,K ).

Head pentagonal, markedly extended from pereon, with small dark eyes near posterolateral margins. Antennae of three and five articles respectively, each setose distally; second antennae, visible in dorsal view, much longer than first ( Figure 1L ).

Pereon broader than head and pleon, broadest across pereomeres 2–4. Pereomeres deeply separated by anterolateral gaps. No midventral projections ( Figure 1K ). Pereopods 1–3 much larger than others, their dactyli long ( Figure 1M ); pereopods 4–7 progressively smaller and with smaller dactyli ( Figure 1N ); all meri and carpi fused.

Pleon of six distinct pleomeres, abruptly narrower than pereon and tapering smoothly posteriorly. Lateral margins of all pleomeres reflexed laterally and posteriorly ( Figure 1K ). Five pairs of uniramous flap-like pleopods progressively smaller posteriorly. Pleomere 6 with prominent anal cone and produced posteriorly into extended nonarticulating falcate uniramous uropods.

Description of paratype specimens

All paratype specimens essentially similar to the holotype and allotype specimens, but one paratype female ( CIEA625101 ) smaller than the holotype female. Another paratype female ( CIEA626401 ) less distorted than the holotype .

Etymology

Species name globifera , first declension Latin adjective meaning “sphere-bearing” in reference to globose endopodites of last pleopod and uropod of holotype female.

Distribution and hosts

Beibu Gulf, Woody Island, China, infesting Dardanus hessii (Miers, 1884) ; the South China Sea, infesting Spiropagurus sp.

Discussion

Asymmetrione globifera illustrates well the characters diagnostic for the genus Asymmetrione , as summarized most recently by Pardo et al. (2009). Its female has the propodi of all pereopods distally produced into “sockets” that receive the ends of the sharp curved dactyli, a structure unique to this genus. It is also very greatly distorted, more than 90°, a character common to most species of Asymmetrione (though not all of them), the source of the name of the genus and almost unique in the subfamily Pseudioninae . Males of all known species of Asymmetrione are two to three times as long as wide, with extended separated heads, all pereomeres and pleomeres separate, first two pairs of pereopods markedly larger than others, pleopods as extended uniramous flaps and uniramous uropods prominent.

Pardo et al. (2009) published a key to females of the 10 species of Asymmetrione heretofore known worldwide. In having very great asymmetry and barbula without finely digitate margins and tuberculate pleopods, the female of A. globifera keys to A. nossibensis Bourdon, 1976 , which differs, as described by Bourdon (1976), from A. globifera as follows. Female: sides of body not parallel but broader forward; frontal lamina not divided; barbula with much shorter projections both laterally and medially; internal ridge of first oostegite bearing many more but shorter projections; pleopods proportionately narrower. Male: head suboval, not pentagonal; pereon proportionately wider and tapering more from front to back.

Codreanu et al. (1965) erected the genus Asymmetrione , of which they designated Pseudione asymmetrica Shiino, 1933 , the type-species. Markham (1975) reviewed the genus Asymmetrione and incorporated Megachelione Bourdon, 1968 , into it. Pardo et al. (2009) recently discussed the genus in detail and presented a key to the females of the 10 species heretofore known. Occurrence of those species, the new one described herein and two probable but undescribed species is summarized in Table 1.

Figures

Figure 1. Asymmetrione globifera sp. nov. Holotype female (A–I). Allotype male (J–N). (A) Dorsal view; (B) ventral view; (C) left antennae; (D) right side of barbula; (E) right maxilliped, external view; (F) right oostegite 1, external view; (G) right oostegite 1, internal view; (H) right pereopod 1; (I) left side of pleon, dorsal view; (J) dorsal view; (K) ventral view; (L) right antennae; (M) left pereopod 2; (N) left pereopod 7. Scale bars: 1.00 mm for A,B; 0.22 mm for C; 0.25 mm for D; 0.40 mm for E; 0.67 mm for F,G,I; 0.36 mm for H,J,K; 0.09 mm for L; 0.11 mm for M,N.