Ceratothoa guttata ( Richardson, 1910 )

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 : 271-272

Ceratothoa guttata ( Richardson, 1910)

Meinertia guttata Richardson, 1910: 20 , fig. 19.

Codonophilus guttatus .— Nierstrasz, 1931: 132.

Meinertia venusta Avdeev, 1978a: 30 , pl. 1.

Ceratothoa venusta .— Avdeev, 1981a: 1160, fig. 3; 1990: 32, figs. 1–6.— Trilles, 1986: 625, tab. 1; 1994: 129.

Ceratothoa guttata .— Bruce & Bowman, 1989: 4, figs. 3–4.— Trilles, 1994: 119.— Kensley, 2001: 232.— Bruce, Lew Ton & Poore, 2002: 172.

Types and type locality. The syntypes are deposited at the National Museum of Natural History (USNM 40914; from Jolo Island, Plillipines; host unknown) ( Richardson 1910). The holotype of Meinertia venusta Avdeev, 1978 (synonym of Ceratothoa guttata ) is deposited at the Russian Pacific Federal Fisheries Research Institute (AGK 75054; from host Parexocoetus brachypterus ; from the Red Sea).

Material examined. ♀ ovig. (14 mm), Gulf of Carpentaria, off Mornington Island, QLD, 16 March 1983, from mouth of Parexocoetus brachypterus (Richardson, 1846) , coll. A. Harris CSIRO (QM W11752).

Remarks. Ceratothoa guttata was most recently redescribed by Bruce & Bowman (1989). The species can be distinguished by the elongate body widest at pereonite 5, both the antennula and antenna are stout and similar in length; pleonites and pleotelson narrower than pereonite 7, uropods extending to the posterior margin of the pleotelson, expanded merus on pereopod 1, expanded ischium on pereopods 5–7 and expanded basis on pereopods 4–7. Ceratothoa guttata is a parasite of flying fish and has only been reported from one host species, Parexocoetus brachypterus .

Richardson’s (1910) illustration of the syntype shows a rhomboid-like body, the uropods not extending beyond pleotelson and deeply arched posterior margins on pereonites 6 and 7. Richardson (1910) observed differences between Ceratothoa guttata , C. trigonocephala and C. oxyrrhynchaena Koelbel, 1878 in the shape of the pleonite 5, the lengths of the uropods, the shape of the coxae, and the structure of the pereopods. Ceratothoa trigonocephala differs from C. guttata in having a subparallel body shape, linear anterolateral margins of cephalon, coxae 5–7 not dorsally visible, minute projection on pereopod 1 merus and the absence of a broad protrusion of pereopod 7 ischium inferior margins. Ceratothoa oxyrrhynchaena differs from C. guttata in having a smooth and ovoid body shape (elongate body shape in C. guttata ) and pleotelson as wide as pereonite 7.

Bruce & Bowman’s (1989) syntype illustrations showed the antennula and antenna to be similar in shape, pereopod 7 with a prominent bulbous ischium and the pleon not overlapped by pereonite 7. Bruce & Bowman (1989) mentioned that both Ceratothoa carinata and C. guttata have a posteriorly expanded pereopod 7 ischium. Ceratothoa carinata differs from C. guttata in having the pleotelson wider than long with a deeply concave posterior margin, the pereon dorsal surface with a median longitudinal ridge and the depressed adjacent dorsal surfaces on either side of the pereon.

Avdeev’s (1978a) illustration showed that Ceratothoa venusta has a more stout body, slightly concave posterior margin of the pleotelson, uropod rami of similar length and width, and pereonite 7 overlapped by pereonite 6 and pleonite 3. Bruce & Bowman (1989) later synonymised C. venusta with C. guttata , a decision with which we agree on the basis of host preference and the similar pereopod 7 ischium, pleopod, pleotelson and coxal morphology.

Distribution. Philippines ( Richardson 1910; Nierstrasz 1931; Bruce & Bowman 1989; Kensley 2001); Red Sea ( Avdeev 1978a; Bruce & Bowman 1989; Kensley 2001); Madagascar; Australia; and Taiwan ( Bruce & Bowman 1989; Kensley 2001).

Hosts. On flying fish, Parexocoetus brachypterus ( Bruce & Bowman 1989; Avdeev 1978a).