Nerocila depressa Milne Edwards, 1840

Martin, Melissa B., Tuah, Alia, Muhamad, Juariah H. & Bruce, Niel L., 2022, A review of the family Cymothoidae (Isopoda: Cymothooidea) infesting marine fishes from Malaysian waters, with new host and geographical records, Zootaxa 5222 (1), pp. 1-36 : 17-18

Nerocila depressa Milne Edwards, 1840

Nerocila depressa Milne Edwards, 1840: 254 , pl. 31 (figs 17–21).— White, 1847: 108.—Schioedte & Meinert, 1881: 15, pl. 1 (figs 10, 1l).— Stebbing, 1893:351.—Lanchester, 1900: 265, pl. XII (fig.5).— Thielemann, 1910:33.— Nierstrasz,1931:124.— Trilles, 1975: 318, pl. II (fig. 13); 1979: 251.— Bruce, 1987b: 404, fig. 34e.—Bruce & Harrison Nelson, 1988: 591, fig. 3.— Kazmi, Schotte & Yousuf, 2002: 105, fig. 91.—Trilles, Ravichandran & and Rameshkumar, 2011: 451.—Printrakoon & Purivirojkul, 2011: 322–326, figs 2–4.— Trilles, Rameshkumar & Ravichandran, 2013: 1273–1286, fig. 2b.— Rameshkumar, Ravichandran & Ramesh, 2014c: 124–128, fig. 2.—Anand Kumar, Rameshkumar, Ravichandran, Nagarajan, Prabakaran & Ramesh, 2017: 3–5, fig 2d.— Ravichandran, Vigneshwaran & Rameshkumar, 2019: 47–50 , figs. 3p–r, 6, 7.

Nerocila dolichostylis Koelbel, 1879:411 , pl. II (fig. 3 a–b).— Bruce, 1987c: 404.

Nerocila pigmentata Bal & Joshi, 1959: 565 , pl. 2 (figs 6–10).— Bruce,1987b: 406.

Nerocila pigmenta .—Bal & Joshi, 1960: 446.

Not Nerocila pigmentata .—Parimala, 1984: 180–181, fig. 1 (= Nerocila sp. ?).

Type material. Nationale d’Histoire Naturelle , Paris, France MNHN (Is. 508) “in very poor condition” ( Bruce 1987b) .

Type locality. Not known.

Type host. Not known.

Host. Ariidae , Carangidae , Clupeidae , Cyprinidae , Engraulidae , and Pristigasteridae : Coilia dussumieri Valenciennes,1848 , Engraulis sp. , Cyclocheilichthys apogon (Valenciennes,1842)( Bal&Joshi,1959) ; Opisthopterus tardoore (Cuvier, 1829) (formerly written as O. turtoor ), Sardinella fimbriata (Valenciennes, 1847) ( Bruce 1988) ; Sardinella albella (Valenciennes, 1847) (Printrakoon & Purivirojkul, 2011) ; Sardinella gibbose (Bleeker, 1849) ( Trilles et al. 2013) ; Selaroides leptolepis (Cuvier, 1833) Carangoides malabaricus (Bloch & Schneider, 1801) (Rameshkumar et al. 2014) ; Setipinna tenuifilis (Valenciennes, 1848) , Alectis ciliaris (Bloch, 1787) , and Netuma bilineata (Valenciennes, 1840) (Anand Kumar et al. 2017) .

Distribution. Indo-Pacific oceans, plausibly ranging from India to Hong Kong ( Bal & Joshi 1959; Bruce, 1988; Printrakoon & Purivirojkul 2011; Trilles et al. 2013; Rameshkumar et al. 2014c; Anand Kumar et al. 2017; Ravichandran et al. 2019).

Remarks. Nerocila depressa can be identified by coxae and posterolateral pleonite angles posteriorly directed; pleonites 1 and 2 ventrolateral margins posteriorly directed, acute, extending to pleonites 3–5 respectively; pleotelson lateral margins curving to a medial point. Both Nerocila depressa and Nerocila loveni have similarly shaped pereonites, but differ by the former having the coxae and posterolateral corners of the pleonites posteriorly directed and are not bent dorsally ( Ravichandran et al. 2019).

Nerocila depressa has been reported to attach to the ventral part of the body, particularly the upper pectoral fin (Printrakoon & Purivirojkul 2011). As with other cymothoids, the prevalence and parasitic infestation of Nerocila depressa varies between different hosts and seasons. Printrakoon & Purivirojkul (2011) reported that 54% of the sampled Sardinella albella from an estuary in the Trat province, Thailand was infested with this species. The authors postulated that the parasites could occupy a host at an early phase based on the positive correlation of parasite length versus fish length and parasite infestation versus fish weight Anand Kumar et al. (2017) reported Nerocila depressa attached on three various hosts from Sarawak: Setipinna tenuifilis (Engraulidae) , Alectis indicus (Carangidae) , and Netuma bilineata (Ariidae) . The prevalence and mean intensity of the three host species (<25 individuals per species) were low (<17% and 1.3 respectively).