Cymothoidae, Leach, 1818

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

Key to the genera of the family Cymothoidae from India

1. Maxilliped palp article 3 slender, with setae; dactyli shorter than propodus; antennula shorter than antenna....................................................................................... Elthusa Schiöedte & Meinert, 1884

- Maxilliped palp article 3 robust, without setae; dactyli expressed perhaps against propodus length; antennula and antenna subequal length......................................................................................... 2

2. Body subparallel or weakly ovate; anterior margin of cephalon without distinct rostrum; pleopods 3–5 with fleshy folds.... 3

- Body broad and rounded or ovate; anterior margin of cephalon with distinct rostrum; pleopods 3–5 without fleshy folds.................................................................... Ryukyua Williams & Bunkley-Williams, 1994

3. Body strongly vaulted; anterolateral margins of pereonite 1 minute or reaching anterior margin of rostrum, without prominent lobes........................................................................... Cymothoa Fabricius, 1793

- Body weakly vaulted; anterolateral margins of pereonite 1 extending beyond rostrum, with prominent lobes............. 4

4. Cephalon deeply immersed in pereonite 1; coxae all shorter than pereonites; pleonite 1 partly overlapped by pereonite 7................................................................................... Lobothorax Bleeker, 1857

- Cephalon not deeply immersed in pereonite 1; coxae nearly as long as or longer than respective segment; Pleonite 1 deeply immersed in pereonite 7................................................................................ 5

5. Pleotelson subtriangular; exopods of pleopods 3–5 with proximolateral triangular lobes............................. 6

- Pleotelson rounded or subtruncate; exopods of pleopods 3–5 with lamellar proximomedial lobe................................................................................................... Mothocya Costa, in Hope, 1851

6. Uropods much shorter than pleotelson, rami longer than peduncle; pleonite lateral and ventrolateral margins produced............................................................................... Joryma Bowman & Tareen, 1983

- Uropod more than half of pleotelson length, rami elongate; pleonite lateral and ventrolateral margins not produced....... 10

7. Body widest at pereonite 6; pleotelson rectangular or subtruncate............................................... 7

- Body widest at pereonite 4 or 5; pleotelson rounded or subtruncate.............................................. 8

8. Pereonite 1 anterolateral margins projecting forward, without slight recess, anterior margin concave.................... 9

- Pereonite 1 anterolateral margins projecting laterally, with slight recess, anterior margin straight or convex.................................................................................... Glossobius Schiöedte & Meinert, 1883

9. Cephalon anterior margin produced, truncate, turned down; pereopod 5–7 basis without well-developed carina; pleon and pleotelson axially twisted against the pereon....................................... Catoessa Schiöedte & Meinert, 1884

- Cephalon anterior margin ventrally directed; pereopods 5–7 basis with well-developed carina; pleon and pleotelson are not axially twisted against pereon......................................................... Ceratothoa Dana, 1852

10. Coxae 4–7 narrow, much shorter than respective pereonite; body dorsal surface strongly vaulted....... Anilocra Leach, 1818

- Coxae 4–7 as long as or longer than respective pereonite; body dorsoventrally flattened............................ 11

11. Pleonites 1 and 2 ventrolateral margins produced............................................ Nerocila Leach, 1818

- Pleonites 1 and 2 ventrolateral margins not produced........................................................ 12

12. Uropod rami short, not extending beyond posterior of pleote1son; coxae inconspicuous in dorsal view................. 13

- Uropod rami long, extending well beyond posterior of pleotelson; coxae conspicuous in dorsal view.................................................................................................. Amblycephalon Pillai, 1954

13. Antennula subequal to, or shorter than antenna; coxae posteriorly rounded........................ Norileca Bruce, 1990

- Antennula as long as, or longer than antenna; coxae 5–7 posteriorly acute........................................ 14

14. Rostrum folded back, lying between antennula bases........................................................ 15

- Cephalon without rostrum, or rostrum not projecting between antennula bases..................... Renocila Miers, 1880

15. Pereon flatted in mid-dorsally; lateral margins of pereopods with spiny and sensory setae.......... Pseudirona Pillai, 1964

- Pereon elevated mid-dorsally; pereopods without spiny and sensory setae.............. Agarna Schiöedte & Meinert, 1884