Syncyamus ilheusensis Haney, De Almeida and Reis, 2004

Iwasa-Arai, Tammy, Carvalho, Vitor Luz & Serejo, Cristiana Silveira, 2017, Updates on Cyamidae (Crustacea: Amphipoda): redescriptions of Cyamus monodontis Lütken, 1870 and Cyamus nodosus Lütken, 1861, a new species of Isocyamus, and new host records for Syncyamus ilheusensis Haney, De Almeida and Reis, 2004, Journal of Natural History (J. Nat. Hist.) 51 (37 - 38), pp. 2225-2245 : 2241-2242

Syncyamus ilheusensis Haney, De Almeida and Reis, 2004

( Figure 8 )

Syncyamus ilheusensis Haney, De Almeida and Reis, 2004: 410–416 , figs 1–5.

Material examined

Host Peponocephala electra : one male, 3.4 mm, four females, 3.4–5.5 mm, two juveniles, 1.5 mm, Aracati (4.457°S; 37.746°W), Ceará, Brazil, MNRJ 26765 (AQUASIS 02C1511/562); one male, 3.2 mm, two ovigerous females, 3.5–4.3 mm, one female, 3.6 mm, Fortaleza (3.808°S; 38.411°W), Ceará, Brazil, MNRJ 26766 (AQUASIS 05C1511/673); host Stenella clymene : one male, 3.1 mm, one female, 4.3 mm, Aquiraz (3.893°S; 38.353°W), Ceará, Brazil, MNRJ 28469 (AQUASIS 02C1151/720); host Globicephala macrorhynchus : one male, 3.5 mm, Cruz (2.812°S; 40.415°W), Ceará, Brazil, MNRJ 26767 (AQUASIS 02C1921/527) .

Hosts

Globicephala macrorhynchus , Peponocephala electra (new host record), Stenella clymene (new host record).

Diagnosis (adapted from Haney et al. 2004)

Anterior margin of pereonite 2 bilobed, with intern lobe much larger in size ( Figure 8 (a)); lateral gills uniramous and ventrally directed, not reaching anterior margin of pereonite 2 ( Figure 8 (b,c)); accessory gills of male subtriangular, approximately two-thirds length of lateral gill; pereonites 3 and 4 lacking acute ventral processes; pereonites 5 and 6 of male bearing two pairs of acute ventral processes, pereonite 7 of male with one pair of acute ventral processes ( Figure 8 (d)).

Remarks

Syncyamus is a genus of small cyamids composed of four described species all of which are ectoparasites of warm-water dolphins. Syncyamus ilheusensis differs from S. aequus Lincoln and Hurley, 1981 by the number of acute ventral processes on pereonite 5, the presence of accessory gills in males and larger body size. Syncyamus ilheusensis differs from S. pseudorcae Bowman, 1955 by the asymmetrical lobes on anterior margin of pereonite 2, the absence of acute ventral processes on pereonites 3 and 4, and the presence of an acute process on the postero-medial margin of the basi-ischium of pereopod 7. The original description of S. ilheusensis was based on specimens collected from a short-finned pilot whale ( G. macrorhynchus ) stranded on the north-east coast of Brazil ( Haney et al. 2004).

The specimens examined from P. electra and S. clymene agree with the general description of S. ilheusensis . A small difference was noticed, in the presence of a large blunt process on the postero-medial margin of the basi-ischium of pereopod 7 instead of a small acute process ( Figure 8 (d)). Comparative material examined from G. macrorhynchus also exhibited a blunt process. This is a new record of S. ilheusensis for Ceará, which was also found on different host species, P. electra and S. clymene . It is known that melon-headed whales host another species of whale-louse, Isocyamus delphinii ( Wardle et al. 2000) ; however, the two cyamids were not recorded together. Cyamids from Stenella clymene were previously assessed by Carvalho et al. (2010), who reported the whale louse S. pseudorcae .

Figures

Figure 8. Syncyamus ilheusensis Haney, De Almeida and Reis, 2004. Non-type male, 3.4 mm. MNRJ 26765. (a) Dorsal view. (b) Ventral view. (c) Ventral view. Gills. AG: accessory gill; LG: lateral gill. (d) Ventral view of pereopod 7. Arrow indicates blunt process on basi-ischium.