Tylokepon bonnieri Stebbing, 1904

An, Jianmei, Zhang, Miao & Paulay, Gustav, 2018, New records of Tylokepon with the description of a new species (Epicaridea, Bopyridae, Keponinae), ZooKeys 790, pp. 77-85 : 80-83

Tylokepon bonnieri Stebbing, 1904 Figure 2

Tylokepon bonnieri Stebbing, 1904: 716-717, pl. LIII, B, C; Shiino 1950: 166; Pillai 1954: 19; Pillai 1964: 187-188, figs. 7-11; An 2009: 96-98.

Material examined.

UF 42219: 1♀, 1♂, Australia, Queensland, Lizard Island, north side, at "Washing Machine, 14°39.02'S, 145°27.73'E, from dead Pocillopora , 21 February 2009, coll. Molly Timmers. Infesting right branchial chamber of Tylocarcinus styx (Herbst, 1803) (UF 18294).

Description of female.

Length 3.58 mm (excluding uropods), maximum width 2.28 mm across pereomere 3, head length 0.66 mm, head width 1.26 mm. (Figure 2A).

Head large, covering pereomere 1, wider than long, completely bilobed, with two ellipsoid structures separated by a deep median groove. Frontal lamina narrow, visible in dorsal view. Small black eyes near frontal lamina (Figure 2A). First and second antennae rudimentary, with three and five articles, respectively, terminally setose (Figure 2B). Barbula (Figure 2C) with two large falcate projections and a mediad sharp projection on each side. Anterior article of maxilliped (Figure 2D) much larger than posterior one, with prominent, inwardly-directed and setose palp, plectron short.

Pereon broadest across pereomere 3. Head covering much of pereomere 1. Distinct dorsolateral bosses on first four pereomeres on both sides. Coxal plates absent. Tergal projection present on pereomeres 2 and 3. Middorsal projections on last two pereomeres: three parallel projections on pereomere 6, one large and posteriorly extended projection on pereomere 7 (Figure 2A). Brood pouch incompletely covered by oostegites. Oostegite 1 (Figure 2E, F) composed of two subequal in size articles, with smooth internal ridge that bears three marginal projections; ending in extended posterolateral point. Pereopod 1 much smaller than others, all pereopods with short dactyli (Figure 2G, H).

Pleon of six distinct pleomeres, first five with well-developed, tuberculate lateral plates, and biramous, tuberculate pleopods. All lateral plates and exopodites of pleopods with digitate margins. Endopodites of pleopods 1-5 small and smooth (Figure 2A). Uniramous uropods similar to exopodites of pleopod 5.

Description of male.

Length 1.08 mm, maximal width 0.32 mm, across pereomere 3, head length 0.11 mm, head width 0.16 mm, pleonal length 0.39 mm. Body gradually tapered posteriorly, all segments distinct (Figure 2I).

Head semicircular, broader than long; without eyes. First and second antennae of three and five articles, respectively (Figure 2J), basal articles greatly expanded, final articles fringed with setae. Pereon broadest across pereomere 3. Pleon of six segments, first five pleomeres with tuberculate uniramous pleopods. Pleomere 6 bilobed, with tuberculate projections and setae (Figure 2K).

Remarks.

Stebbing (1904) erected Tylokepon for T. bonnieri infesting Tylocarcinus styx from the Indian Ocean. Pillai (1954, 1966) recorded the species from Kovalam, southwest India, infesting Menaethius monoceros . An (2009) reported it from Beibu Gulf and Hainan, China, infesting Hyastenus diacanthus and the parthenopid crab Enoplolambrus validus (De Haan, 1837). Although Hyastenus diacanthus was recorded to be infested by Tylokepon naxiae from Hong Kong, it is not impossible that a single host is found bearing two different species, such as the case of Petrolishthes quadratus Benedict, 1901 bearing Aporobopyrus crutatus (Richardson, 1910) and A. bonairensis Markham, 1988.

As for T. naxiae , Bonnier (1900) only gave a brief description, and Markham (1982) found that the holotype female is badly damaged, and only three useful characters can be defined. However, from the figure ( Markham 1982: fig. 18), it can be seen that the species has an almost smooth surface to the pleopods and the lateral plates are not covered with tuberculate (while the pleopods and lateral plates of T. bonnieri are densely covered with tubercles). Therefore, T. bonnieri differs from T. naxiae .

The present specimens conform well to Stebbing’s description (1904), except for some minor differences, such as the male specimen lacking eyes. There are slight differences between the present specimens and those from Beibu Gulf ( An 2009) in the middorsal projections on pereopod 6 and frontal lamina of the head, but the key characters of the females, such as oostegite 1, maxilliped, barbula, lateral plates and pleopods, as well as of males, are similar.