Heterocepon marginatum Shiino, 1936

Boyko, Christopher B. & Williams, Jason D., 2024, New records of bopyrid parasites (Crustacea, Isopoda, Epicaridea) of pea crabs (Crustacea, Decapoda, Pinnotheridae) with descriptions of two new species of Rhopalione Pérez, 1921 and a review of the genus, Zoosystema 46 (7), pp. 149-175 : 153-154

Heterocepon marginatum Shiino, 1936

( Figs 1; 2 )

Heterocepon marginatum Shiino, 1936a: 161 , 165-168, fig. 2 [ex Pinnotheres parvulus Stimpson, 1858 , Japan]; 1936c: 185 [ex P. parvulus , Japan]; 1972: 9 [list]. — Morita 1940: 76-77 [ ex Pinnotheres sp. , Japan]; 1949: 13-14, figs A-E [ ex Nepinnotheres cardii (Bürger, 1895) , Japan; description of cryptoniscus larva]; 1951: 48 [ ex N. cardii , Japan]; 1952: 54-59, figs 1-3; 1953a: 10, 13 [ex N. cardii , Japan; 1953b: 14-20, figs 1-4 [ ex N. cardii , Japan; description of epicaridium larva, bopyridium, juvenile male and female]; 1955: 53-59 [ ex N. cardii , Japan; fig. 1-5]. — Danforth 1963: 8 [list]. — Wells & Wells 1966: 57 [mention]. — Janssen & Brandt 1994: 12-17, 24, table 1, figs 3-9 [ ex Arcotheres palaensis (Bürger, 1895) , Philippines]. — Saito et al. 2000: 42 [list]. — Boyko & Williams 2001: 656 [mention]. — Miura et al. 2014: 31, 35, 36 [mention]. — Ozeki et al. 2014: 49 [mention]. — Williams et al. 2023: 532 [list], 539 [mention].

“bopyrid isopod” – Janssen 1986: 15, 23, fig. 5 [ex A. palaensis , Philippines].

“hyperparasite” – Janssen 1986: 18 [ex A. palaensis , Philippines].

“bopyrid”– Ahyong & Ng 2007: 200 [ex A. palaensis , paralectotype female (SMF-ZMG948b), Palau; photographs examined herein]. — Ng & Ahyong 2022: 145 [ex ZRC 1987.537-539; specimen examined herein], 148 [ex ZRC 1993.120-122; host examined herein], 195 [ex ZRC 2013.1416; specimens examined herein].

“unidentified bopyrids” [of Arcotheres palaensis (in part) and Arcotheres rayi ] – Williams et al. 2023: 533 [list].

MATERIAL EXAMINED. — Peninsular Malaysia or Singapore • 1 ovigerous ♀ (4.5 mm TL), 1 mature ♂ (3.0 mm TL), from left branchial chamber of female Arcotheres palaensis (Bürger, 1895) (5.7 mm CL, 9.6 mm CW; ZRC 1987.537-539), ex Tegillarca granosa (Linnaeus, 1758) ( Arcidae ); from markets; 20.XI.1986; P. K. L. Ng, leg.; ZRC 2023.0257.

Malaysia • 1 mature ♀ (3.5 mm), 1 mature ♂ (1.8 mm), from right branchial chamber of female Arcotheres rayi Ahyong & Ng, 2007 (5.0 mm CL, 7.0 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0262 • 1 mature ♀ (3.2 mm), mature ♂ (2.8 mm), from left branchial chamber of female A. rayi (4.9 mm CL, 8.0 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0263 • 1 ovigerous ♀ (3.4 mm), 1 mature ♂ (2.6 mm), from right branchial chamber of female A. rayi (5.0 mm CL, 7.5 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0264 • 1 ovigerous ♀ (3.6 mm), 1 mature ♂ (3.2 mm), from right branchial chamber of female A. rayi (4.9 mm CL, 8.0 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0265 • 1 immature ♀ (2.5 mm), from left branchial chamber of female A. rayi (3.8 mm CL, 5.7 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0266 • 1 ovigerous ♀ (4.0 mm), 1 mature ♂ (2.9 mm), from right branchial chamber of female A. rayi (5.0 mm CL, 8.5 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae Rafinesque, 1815 ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0267 • 1 ovigerous ♀ (4.2 mm), 1 mature ♂ (3.5 mm), from left branchial chamber of female A. rayi (6.0 mm CL, 10.0 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0269 • 1 ovigerous ♀ (3.6 mm), 1 mature ♂ (2.8 mm), from left branchial chamber of female A. rayi (4.7 mm CL, 8.0 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0270 • 1 ovigerous ♀ (3.6 mm), 1 mature ♂ (2.8 mm), from left branchial chamber of female A. rayi (4.6 mm CL, 8.0 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0271 • 1 ovigerous ♀ (3.0 mm), 1 mature ♂ (2.8 mm), 1 immature ♂ (1.0 mm), from right branchial chamber of female A. rayi (4.7 mm CL, 7.3 mm CW; ZRC 2013.1416), ex Paphia sp. ( Veneridae ); Pahang, Bentong Market; 10.V.2010; M. Low leg.; ZRC 2023.0272.

“ Singapore? ” • 1 ovigerous ♀ A. palaensis (7.1 mm CL, 9.0 mm CW; with swollen empty right branchial chamber), ex T. granosa ; market; 8.XII.1987; P. K. L. Ng leg.; ZRC 1993.120-122.

REMARKS

This is the first record of the species from Malaysia and likely Singapore based on the host branchial chamber swelling; however, because some specimens were obtained from markets where field sites were not noted, the country of origin remains unclear for some of the museum lots. The female ( Figs 1A, D; 2 ) and male ( Fig. 1B) specimens match the original description. An additional parasitized ovigerous female Arcotheres palaensis ( ZRC 1993.120-122) was examined but the swollen branchial chamber was empty. In light of the identity of the host, the bopyrid was probably H. marginatum .

In situ photographs of a female specimen in a host Arcotheres palaensis ( SMF-ZMG 948b) ( Fig. 1C) and the extracted female ( Fig. 1 D ) were examined. The female bopyrid identity was confirmed, but no male was present.

Figures

FIG. 2. — Heterocepon marginatum Shiino, 1936, ZRC 2023.0271 (A-I): A, right antenna and antennule of female; B, barbula of female (asterisk shows missing outer lobe); C, left maxilliped of female, outer view with outer barbular lobe attached; D, left oostegite 1 of female, outer view; E, left oostegite 1 of female, inner view; F, left pereopod 1 of female; G, left pereopod 7 of female. Scale bars: A, F, G, 50 µm; B, 250 µm; C-E, 200 µm.

FIG. 1. — Heterocepon marginatum Shiino, 1936, ZRC 2023.0264 (A), ZRC 2023.0269 (B), SMF-ZMG948b (C, D): A, female, dorsal view (dashed line shows where oostegites are cut-off in the picture); B, male, dorsal view; C, female in host Arcotheres palaensis (Bürger, 1895); D, female, dorsal view. Scale bars: A, B, D, 1 mm; C, 2.5 mm.