Ceratothoa gilberti (Richardson, 1904)

Hadfield, Kerry A., Bruce, Niel L. & Smit, Nico J., 2016, Redescription of poorly known species of Ceratothoa Dana, 1852 (Crustacea, Isopoda, Cymothoidae), based on original type material, ZooKeys 592, pp. 39-91 : 52-53

Taxon classification Animalia Isopoda Cymothoidae

Ceratothoa gilberti (Richardson, 1904) Figure 5

Meinertia gilberti Richardson, 1904: 53, figs 32-33; 1905: 241-242, figs 247-249.- Schultz 1969: 157-158, fig. 237.

Codonophilus gilberti .- Nierstrasz 1931: 132.- Brusca 1977: 130; 1980: 230, 232, fig. 12.17.

Meinertia sp.- MacGinitie 1937: 1031, 1035, pl. I, fig. 1.

Ceratothoa gilberti .- Wallerstein 1980: 232.- Brusca 1981: 178-182, figs 21 a–d, figs 22 a–l.- Avdeev 1982a: 65-67; 1982b: 69-77.- Brusca and Iverson 1985: 49.- Trilles 1994: 119.- Espinosa-Pérez and Hendrickx 2001: 48.

Material examined.

Lectotype [here designated]. United States National Museum, USA (USNM 1254761) - female (22 mm TL; 9.5 mm W) collected from Mazatlan, Sinaloa (Mexico) in mouth of Mugil hospes (see Richardson 1904). The left side of pereonites 3-5 were damaged. Paralectotypes. Two males (11-12 mm TL; 4-5 mm W), same data as lectotype (USNM 29080).

Description.

Lectotype female. Length 22 mm, width 9.5 mm.

Body oval, 1.8 times as long as greatest width, dorsal surfaces slightly bumpy, widest at pereonite 4 and pereonite 5, most narrow at pereonite 1, lateral margins posteriorly ovate. Cephalon 0.6 times longer than wide, visible from dorsal view, triangular. Frontal margin rounded to form blunt rostrum. Eyes oval with distinct margins. Antennula more stout than antenna, shorter than antenna, with 7 articles. Antenna with 8 articles.

Pereonite 1 with slight indentations, anterior border straight, anterolateral angle with distinct anterior projection, extend to middle of the eye. Posterior margins of pereonites smooth and slightly curved laterally. Coxae 2-3 narrow; with posteroventral angles rounded; 4-7 acute, posteriorly pointed; not extending past pereonite margin. Pereonites 1-4 increasing in length and width; 5-7 decreasing in length and width; becoming more progressively rounded posteriorly. Pleon with pleonite 1 most narrow, visible in dorsal view; pleonites posterior margin smooth, mostly concave. Pleonite 2 not overlapped by pereonite 7; posterolateral angles of pleonite 2 narrowly rounded. Pleonites 3-5 similar in form to pleonite 2; pleonite 5 free, not overlapped by lateral margins of pleonite 4, posterior margin produced medially. Pleotelson 0.4 times as long as anterior width, dorsal surface with medial furrow, lateral margins weakly convex, posterior margin damaged and shallowly emarginate.

Pereopod 1 basis 1.7 times as long as greatest width; ischium 0.6 times as long as basis; merus proximal margin with bulbous protrusion; carpus with rounded proximal margin; propodus 1.6 times as long as wide; dactylus moderately slender, 0.9 times as long as propodus, 2.1 times as long as basal width. Pereopod 7 basis 1.4 times as long as greatest width; ischium 0.8 times as long as basis, without protrusions; merus proximal margin with large bulbous protrusion, merus 0.4 times as long as wide, 0.3 times as long as ischium; carpus 0.4 times as long as wide, 0.2 times as long as ischium, without bulbous protrusion; propodus 0.9 times as long as wide, 0.4 times as long as ischium; dactylus slender, 1.5 times as long as propodus, 2.3 times as long as basal width.

Uropod more than half the length of pleotelson, peduncle 0.9 times longer than rami, peduncle lateral margin without setae; rami not extending beyond pleotelson, marginal setae absent, apices narrowly rounded. Endopod apically rounded, 3.6 times as long as greatest width. Exopod extending to end of endopod, 4 times as long as greatest width, apically rounded.

Size.

Female: 16-29 mm TL (8-14 mm W) ( Brusca 1981).

Distribution.

Known from the south-western coast of northern America in the Gulf of California region: from southern California, USA ( MacGinitie 1937, Brusca 1981, Espinosa-Pérez and Hendrickx 2001) and the west coast of Baja California to Puerto Penasco and Mazatlan, Mexico ( Richardson 1904, Nierstrasz 1931, Brusca 1977, Brusca 1981, Espinosa-Pérez and Hendrickx 2001).

Hosts.

On tongue of the mullet Mugil cephalus (see MacGinitie 1937, Brusca 1977, 1981); from the mullet, Mugil hospes (see Richardson 1904, Brusca 1977, 1981); and from a “flatfish” ( Brusca 1981).

Remarks.

Ceratothoa gilberti has an elongate body; pleon as wide as pereon; short uropods; a elongate, triangular cephalon; short anterolateral projections on pereonite 1; and a large pleotelson with a rounded posterior margin. Furthermore, Brusca (1981) previously noted that Ceratothoa gilberti lacks an appendix masculina in the male. The female specimen is here designated as the lectotype and redescribed.

Ceratothoa gilberti has been infrequently collected and seems to be confined to the region around the Gulf of California. It has only been found on mullet species and has often been compared to Ceratothoa gaudichaudii (which has recently been placed into species inquirenda by Martin et al. [2015]).