Norileca triangulata ( Richardson, 1910 )

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 : 68

Norileca triangulata ( Richardson, 1910)

( Figs 13 j–l, 17–19)

Livoneca triangulata Richardson, 1910: 23 , fig. 22 .— Nierstrasz, 1931: 143.

Norileca triangulata . — Bruce, 1990: 294–296, figs 30, 31.— Rameshkumar & Ravichandran, 2015: 33–36, figs 1, 2.

Type and type locality. Syntype, held at National Museum of Natural History , Smithsonian Institution ( USNM 40915 ) from Tanimdao Island, Philippines ( Richardson 1910) .

Material examined. 4 ovig. females (15–19 mm) Mandapam, 18 January 2012, from Sardinella gibbosa , coll. G. Rameshkumar ( CAS / MBRM C- 216– C- 219), 1 ovig. female (16 mm) Parangipettai, 14 April 2017, from Sardinella gibbosa , coll. S. Ravichandran ( ZSI / MBRC D1-550), the Southeastern coast of India.

Description female. Body 2.5 times as long as wide, weakly twisted; widest at pereonite 4; dorsum moderately convex. Cephalon as long as wide, posterior part not deeply immersed in pereonite 2; anterior margin moderately rounded, moderately turned down. Eyes large, 0.5 width of cephalon. Pereonites 1 and 7 shortest, 4, 5 longest 2, 3, 6 subequal in length. Pereonite 7 posterior margin with moderate indentation. All coxae are narrow from pereonites 2 and 4–6; coxae of pereonite 2 as long as segment; those of pereonites 3 and 4 shorter than respective segment. Pleonite 1 longest, as wide or slightly wider than pereonite 7; pleonite 1 distinctly narrower, 0.8 times wider than pleonite 5. Pleotelson 1.5 times wide as long, triangular.

Antennula consists of 8 articles; peduncle articles 1 and 2 distinct and articulated; article 2 1.1 times as long as article 1; article 3 1.6 times as long as wide, 0.5 times as long as combined lengths of articles 1 and 2; flagellum with 5 articles, extending to posterior margin of eye with tufts of simple setae on articles 3–6 and 8. Antenna consists of 9 articles; peduncle article 3 1.0 times as long as article 2; article 4 2.2 times as long as wide, 1.4 times as long as article 3; article 5 twice as long as wide, 0.7 times as long as article 4. Antenna flagellum with 6 articles, terminal article with 1–5 short simple setae, extending to anterior margin of pereonite 1. Mandibular molar process present, with no simple setae; mandiblepalp article 2 and 3 without setae. Maxillula simple with 4 terminal robust setae. Maxilla medial lobe partly fused to lateral lobe; medial and lateral lobe with 2 recurved robust setae, lateral lobe with 1 large recurved robust setae. Maxilliped palp article 2 with tiny setae; article 3 with 3 recurved robust setae.

Pereopods 1–4 shorter than 6 and 7. Pereopod 1 propodus with 5 spines on palm; dactylus abruptly angled at proximal 0.3, extending to merus. Pereopod 2 with 3 spines on propodal palm; pereopods 2 and 3 similar to 1. Pereopods 4–7 similar to each other, all bases with distinct anterolateral carina. Pereopod 7 basis and ischium subequal in length; dactylus extending to posterior of carpus. Pleopod 1 rami round, proximomedial lobe fairly developed and peduncle lateral lobe weakly developed; pleopods 2–5 with endopod proximomedial lobe well developed. Pleopods 3–5 endopods with folded proximomedial lobe; pleopod 5 endopod posterior surface complexly folded.

Uropods about 0.75 length of pleotelson, reaching the middle of the lateral margin of pleotelson, endopod slightly longer than exopod, rami subequal in length.

Colour. Pale brown, black chromatophores overndorsal surface, particularly on pleon, and also pleotelson which appears black.

Size. Ovig. females 15–19 mm.

Remarks. Norileca triangulata can be characterised by a nearly flat dorsum, large eyes, cephalon weakly immersed in pereonite 7, weakly twisted body, mandible palp article 2 greatly expanded, pleonite 5 narrower than 1 and triangular pleotelson.

Norileca triangulata can be distinguished from N. indica by several characters, the easiest to observe being the nearly straight body, larger eyes, pleonite 5 narrower than 1 and the proportionally longer uropods. It differs from N. borealis by having longer uropods, larger eyes, and a larger length-to-width ratio of the pleotelson, other characters are discussed under the remarks of N. indica .

Distribution. Previously record from the Philippine Islands (Richardson 19l0) and latterly from Queensland- Eel Reef, Cape York; Michaelmas Cay, near Cairns; and Mooloobah, south-eastern Queensland ( Bruce 1990). Recent records from the southeast coast of India ( Rameshkumar & Ravichandran 2015).

Hosts. Norileca triangulate was collected from Parexocoetus brachypterus ( Bruce 1990) and Sardinella gibbosa ( Bruce 1990; Rameshkumar & Ravichandran 2015).

Figures

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).

FIGURE 22. Ryukyua globosa Williams & Bunkley-Williams, 1994, female (14 mm), (ZSI/MBRC D1-552). a, pereopod 6; b, pereopod 7; c–g, pleopods 1–5; h, uropod.