Genus Nerocila Leach, 1818

Nerocila Leach, 1818: 351 .— Desmarest, 1825: 307.— Milne Edwards, 1840: 250.— Dana, 1853: 747.— Schiöedte & Meinert, 1881: 4.— Gerstaecker, 1882: 231.— Richardson, 1905: 219.— Hale, 1926: 202.— Monod, 1931: 5.— Van Name, 1936: 431.— Barnard, 1936: 163.— Brian & Dartevelle, 1949: 135.— Szidat, 1955: 216.— Menzies & Kruczynski, 1983: 55.— Brusca & Iverson, 1985: 45. — Bruce, 1987b: 355–412.— Bruce & Harrison-Nelson, 1988: 591.— Yu & Li, 2002: 266– 269.

Ichthyophilus Latreille, 1802: 133 .

Emphylia Koelbel, 1879: 413–414.

Pterisopodus Boone, 1918: 596 .

Nerocila (Emphylia) . Miers, 1880: 4.— Bowman, 1978: 34.

Diagnosis. A detailed diagnosis was provided by Bruce (1987b).

Type species. Leach (1818) clearly indicated Nerocila blainvillei as the single species he was placed in the genus. He also listed Cymothoa falcate Fabricius, 1787 but the identity of that species is not known. Nerocila blainvillei is apparently an unjustified replacement name for N. falcata (G.C.B. Poore and H. Lew Ton, in litt.). Leach’s material is held at the British Museum (BMNH 1979: 400:2) but has never been fully described. Material currently being identified as Nerocila bivittata (Risso, 1816) (see Trilles 1975b) appears conspecific with Nerocila blainvillei (see Bruce 1987b).

Remarks. Nerocila can be identified by the body not vaulted, dorsoventrally flattened, widest at pereonite 6; cephalon posterior margin trilobed, anterior margin truncate; antenna widely separated, antennula shorter than antenna; mandible palp slender, elongate, article 1 longest; article 3 as long as, or longer than 2, with setae on distolateral margin; pereonite 1 antero-lateral angles not produced; pereonite 7 extends past pleonite 1; pereonites 6 and 7 postero-lateral margins produced; brood pouch from coxae 1–4 and 6; posterior pocket present; pleopods 3–5 with large fleshy folds, with proximomedial lamellar lobe and peduncle lobes; uropod rami extend past the pleotelson posterior margin, exopod longer than endopod.

This genus has been considered as a subgenus of Emphylia Koelbel, 1879, by Bowman (1978). This view has not been supported by Bruce (1987b). Bruce (1987b) stated that the subgenus is not clearly separated from Nerocila as some of the characters utilised intergrade. Bruce (1987b) considered the major characters that separate the genera Anilocra, Creniola, Pleopodias, Renocila and Nerocila, it can be seen that two suites of characters separate genera: mouth part differences, and coxal and pleonal differences. Emphylia has an identical mouthpart, coxae and pleonal morphology to Nerocila .

In the Cymothoidae, the external-attaching genera include but are not limited to Anilocra, Nerocila, Renocila Miers, 1880, Creniola Bruce, 1987, and Pleopodias Richardson, 1910 . Nerocila can be distinguished from Anilocra by the posterior margin of the cephalon, which is conspicuously smooth and straighted in Nerocila, whereas the posterior margin of the cephalon of Nerocila is trilobed. The posterolateral pereonite margins of Nerocila are more produced, elongate and pointed than that of Anilocra . To date the genera Creniola, Pleopodias and Renocila have not been reported from India.

Species in this genus tend to show a broad host preference, apparently based more on their life history strategies and ecological preferences than on taxonomic specificity, with most preferring demersal and schooling. Published host data reveals that most species are associated with three to ten species of fishes, in several families. To date, the genus Nerocila Leach 1818 includes forty nominal species of which 16 species have been reported from India (Trilles et al. 2011; 2013). Following this present study, we accept 12 species of Nerocila as valid from India.