Agarna Schiöedte & Meinert, 1884

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 : 8-9

Genus Agarna Schiöedte & Meinert, 1884

Agarna Schiöedte & Meinert, 1884: 238 .— Richardson, 1905: 243.— Barnard, 1936: 169.— Pillai, 1964: 211.— Bowman & Tareen, 1983: 21.

Indusa . — Pillai, 1964: 214.

Type species. Agarna carinata Schiöedte & Meinert, 1884 by monotype.

Diagnosis of female. Body asymmetrical and hunched, slightly longer than wide, widest at pereonite 4. One side of the body almost straight and other side strongly recurved. Cephalon symmetrical, wide as long, roughly triangular with narrow round apex, accommodated in the deeply recessed amphicephalic process of pereonite 1. Eyes small, distinct, sub-dorsal and in the posterio-lateral of cephalon. Mandible with a well-developed incisor process. Maxilla bi-lobed with 2 slightly recurved spines on inner median lobe and two spines on outer lateral lobe. Pereonite 1 without coxa, all the coxae are visible in dorsal view; 2–3 transversely placed, 4–7, triangular, circuitously disposed on antero-lateral surface of the lateral margin and the posterior margin free from the pereonite. All the pereonite (except pereonite 1) asymmetrical. The pereonites 1–4 abruptly increase in width towards one side; pereonite 4 widest and gradually decrease the width from 5–7. Pleonites 2–5 visible, increasing progressively in width posteriorly from 1–5; pleonite 5 widest and longest. Pleotelson wide as long, slightly shorter than pleonite 5, posterior margin broadly rounded. Brood pouch with 4 pairs of overlapping oostegites arising from the bases of pereopods 2–4 and 6. Pereopods 1–7 without spines; pereopod 1 short and robust, gradually increase in size from 1–7. Pleopods not distinctly visible in dorsal view. Uropod rami short, flattened extend almost up to the distal margin of pleotelson.

Remarks. Agarna can best be identified by the hunched and asymmetrical body; cephalon roughly triangular with narrow round apex, accommodated in the deeply recessed amphicephalic process of pereonite 1; pereon elevated mid-dorsally, pereonites 3–7 are greatly expanded laterally; pereonite 7 posteriorlaterally produced and overlapping pleonites 3–5; antenna 1 are narrowly separated at their bases, and the mandibular palp is not enlarged. Richardson (1905) made the curious statement that pereonite 4 has 2 coxae and 2 pereopods and pereonite 7 has no appendages. This statement is erroneous; pereonites 4 and 7 each have 1 pair of coxae and 1 pair of pereopods, although overlapping of coxae and lateral pereonite expansions tends to obscure the arrangement.

Agarna Schiöedte & Meinert, 1884 , a genus in the family Cymothoidae , currently include three valid species: Agarna carinata Schiöedte & Meinert, 1884 , Agarna cumulus ( Haller, 1880) and Agarna malayi Tiwari, 1952 . Three additional species of Agarna ( A. brachysoma Pillai, 1964 , A. engraulidis Barnard, 1936 and A. tartoor Pillai, 1954 ) were synonymized with Joryma Bowman & Tareen, 1983 by Bowman & Tareen (1983).

The species Agarna bengalensis Kumari, Hanumantha, Rao & Shaymasundari, 1990 very poor and incomplete description based on male specimen ( Kumari et al. 1990). Within the Cymothoidae , both generic and species diagnoses are dependent on adult female characters, therefore designating A. bengalensis (based on the male description) as the valid species is not the best action. Additionally the validity of this species is questionable and we briefly discuss its current status under the section species inquirenda (p. 79). Agarna pustulosa ( Pillai, 1954) is here regarded as junior synonymy of A. malayi .