Ceratothoa

Martin, Melissa B., Bruce, Niel L. & Nowak, Barbara F., 2015, Review of the fish-parasitic genus Ceratothoa Dana, 1852 (Crustacea: Isopoda: Cymothoidae) from Australia, with description of two new species, Zootaxa 3963 (3), pp. 251-294 : 254

Key to the Australian species of Ceratothoa

1. Pleonite 5 posterior margin bisinuate; coxae 4–7 posteroventral margins narrower than anteroventral margins........... 2

- Pleonite 5 posterior margin not bisinuate; coxae 4–7 posteroventral margins similar to anteroventral margins............. 4

2. Body ovate; less than 2.0 times as long as greatest width; pleotelson wider than long............................... 3

- Body elongate; more than 2.0 times as long as greatest width; pleotelson longer than wide............ Ceratothoa guttata

3. Pereopod 7 basis without carinae; coxae 2–3 anteroventral margins smaller than posteroventral margins............................................................................................... Ceratothoa globulus sp. nov.

- Pereopod 7 basis with carinae; coxae 2–3 anteroventral margins similar to posteroventral margins.. Ceratothoa usacarangis

4. Pereonite 1 with broad anterolateral margins reaching anterior of cephalon; eyes not visible............ Ceratothoa retusa

- Pereonite 1 with weak or slightly protruding anterolateral margins not reaching anterior of cephalon; eyes visible......... 5

5. Pereopod 7 ischium anterior margin dilated; cephalon anterolateral margin concave................................ 6

- Pereopod 7 ischium anterior margin not dilated; cephalon anterolateral margin smooth or straight...................... 7

6. Pleotelson posterior margin deeply concave; dorsum with distinct median ridge; pleopod 1exopod longer than wide............................................................................................ Ceratothoa carinata

- Pleotelson posterior margin, shallow not deeply concave; dorsum evenly convex, without distinct median ridge; pleopod 1 exopod wider than long........................................................ Ceratothoa barracuda sp. nov.

7. Pereopod 1 and 7 merus proximal margin with bulbous protrusion; pleopod endopod 1–5 proximal borders extending below exopod to peduncle.............................................................. Ceratothoa oxyrrhynchaena

- Pereopod 1 and 7 merus proximal margin without bulbous protrusion, pleopod endopod 1–5 proximal borders not extending below exopod to peduncle.............................................................................. 8

8. Pleotelson narrower than pereonite 7; posterior region of pereonites darker than anterior............ Ceratothoa imbricata

- Pleotelson as wide or wider than pereonite 7; posterior region of pereonites lighter than anterior....... Ceratothoa banksii