Nerocila trichiura ( Miers, 1877 )

Ravichandran, S., Vigneshwaran, P. & Rameshkumar, G., 2019, A taxonomic review of the fish parasitic isopod family Cymothoidae Leach, 1818 (Crustacea: Isopoda: Cymothooidea) of India, Zootaxa 4622 (1), pp. 1-99 : 61-66

Nerocila trichiura ( Miers, 1877)

( Figs13 d–f, 14–16)

Anilocra trichiura Miers, 1877: 677–678 ; pl. LXIX ( fig. 6 ).

Restricted synonymy.— Nerocila trichiura .— Trilles, 1979, pl. 2 (fig. 10); 1976; 621.— Kurochkin, 1980: 289.— Bruce, 1987b: 406.— Bruce & Harrison-Nelson, 1988: 596, fig. 7.— Trilles, Ravichandran & Rameshkumar 2011: 453.— Trilles, Rameshkumar & Ravichandran, 2013: 1273–1286, figs 2k, 7j.

Type and type locality. The holotype, held at British Museum (Natural History), London ( BMNH 186:104), Parasitic on flying fishes, Mauritius, Indian Ocean.

Materials examined. 1 ovig. female (27 mm), Parangipettai, 18 June 2011, from Exocoetus volitans , coll. G. Rameshkumar ( CAS / MBRM 497); 1 non ovig. female (30 mm), Parangipettai, 25 March 2017, from Exocoetus volitans , coll. S. Ravichandran ( ZSI / MBRC D1-548 ) ; 1 ovig. female (28 mm), Pazhaiyar, 29 January 2017, from Parexocoetus mento (Valenciennes, 1847) , coll. P. Vigneshwaran ( CAS / MBRM C 216 ) , all from Southeastern coast of India.

Description female. Body elongated, 1.6 times as long as wide widest between pereonites 6–7. Cephalon anterior margin produced narrowly rounded. Eyes small, about 0.26 width of cephalon; ocular surface. Posteroventral corners of pereonites 1–7 slightly rounded. Posterior angles of pereonites 1–7 not produced. Pereonites 1 and 5–7 longest, 2–4 subequal in length. Coxae 2–5, not visible in dorsal view, produced into rounded processes, not exceeding beyond posterior of pereonites. Coxae 5–7, much more long than the anterior margin. All pleonites visibles, pleonite 1 and 2 longest and widest, pleonite 5 shortest, pleonies 3 and 4 subequal, ventrolateral margins of pleonites 1 and 2 posteriorly directed and acute, extending to pleonites 3 or beyond pleonite 4, pleonites 3–5 lateral margins weakly acute. Pleotelson round-triangular, slightly wider than long, lateral margins convex, converging to indistinct apical point.

Antennula with 8 articles, articles 1–3 much wider than other article. Antenna with 10 articles. Mandible palp with several setae on distolateral margin of article 3, with 1 setae on distal margin of article 2. Maxillula with 4 terminal spines. Maxilla with 2 spines each on medial and lateral lobe respectively. Maxilliped with oostegial lobe with many plumose setae and a palp with 2 apical and one lateral small recurved spines on article 3.

Pereopods 1–5 swelling on proximal part of extensor margin of dactyl; pereopods 1 and 2 dactylus about 2.6 times longer than propodus. Pereopod 6 with 2 spines on posterior margin of merus, carpus with 4 spines, and propodal palm with 6 spines. Pereopod 7 with 6 marginal spines on propodus and 2 spins on posterior margin of merus. Pleopods prominent in dorsal view; pleopods 1 and 2 with suture on exopod lateral margin, and on both margins of exopods of pleopods 3–5. Pleopods 3–5 endopods with prominent proximo medial lobe.

Uropod slender, tapering, exopod about 2.5 times longer than endopod, both rami extending far beyond posterior margin of pleotelson.

Colour. Yellowish-tan.

Size. Ovig. females 22–31 mm; non ovig. females 22–29 mm.

Remarks. Nerocila trichiura is readily identified by the anterior margin of the cephalon is subtruncate, the posterior angle of pereonite 7 does not extend posteriorly in an acute process, the coxae 2–7 are produced into a rounded process and the ventrolateral margins of pleonites 1 and 2 are distinctly shorter. The uropods are much longer, exopod and endopod extending far beyond the distal margin of pleotelson.

Bruce & Harrisson-Nelson (1988) stated, does not seem possible to distinct N. excisa Richardson, 1901 , from N. trichiura , both having similar coxae, pereonal and pleonal morphology. Unfortunately, the holotype of Nerocila excisa is in poor condition with the pleotelson torn and the uropods missing (see Bruce 1987c, fig. 34F). It seems probable that the two species are conspecific, there being no discernible differences between the holotype of N. excise and specimens of N. trichiura . This is species widely spread occurring in the Atlantic, Pacific and Indian oceans. Until now this species collected from the host Exocoetus volitans only. Nerocila exocoeti and N. trichiuri have been collected from fishes belonging to the family Exocoetidae and both of these species are readily distinguished from each other (see under Remarks for N. exocoeti ).

Distribution. Widespread species occurring in the Atlantic, Pacific and Indian oceans (Bruce & Harrisson-Nelson 1988; Trilles et al. 2013).

Hosts. Nerocila trichiura collected from the family Exocoetidae : Exocoetus volitans (Bruce & Harrisson-Nelson 1988; Trilles et al. 2013) and Parexocoetus mento (Daniel & Rama Rao (1967).

Figures

FIGURE 6. Nerocila depressa Milne Edwards, 1840, female (30 mm), (ZSI/MBRC D1-541). a, dorsal view; b, lateral view; c, forns; d, antennula; e, antenna; f, mandible; g, maxillula; h, maxilla; i, maxilliped.

FIGURE 13. a–c, Nerocila sundaica Bleeker, 1857, female (24 mm), (ZSI/MBRC D1-547); d–f, Nerocila trichiura (Miers, 1877), female (30 mm), (ZSI/MBRC D1-548); g–i, Norileca indica (H. Milne Edwards, 1840), female (26 mm), (ZSI/MBRC D1-549); j–l, Norileca triangulata (Richardson, 1910), female (16 mm), (ZSI/MBRC D1-550); m–o, Ryukyua circularis (Pillai, 1954), female (13 mm), (CAS/MBRM C-227); p–r, Ryukyua globosa Williams & Bunkley-Williams, 1994, female (14 mm), (ZSI/MBRC D1-552).