Obelia bidentata Clark, 1875

Gil, Marta & Ramil, Fran, 2025, Hydroids (Cnidaria, Hydrozoa) from Guinea Bissau, Zootaxa 5577 (1), pp. 1-89 : 34-35

Obelia bidentata Clark, 1875

Obelia bidentata Clark, 1875: 58–59 , pl. 9 fig. 2.— Gili et al., 1989, 106–107, fig. 3B.— Calder, 1991: 70–72, fig. 37.— Ramil

& Vervoort, 1992a: 241–243, fig. 68A–B.— Cornelius, 1995b: 292–295, fig. 68.— Medel & Vervoort, 2000: 46–49, fig.

12.— Peña Cantero & García Carrascosa, 2002: 159–161, fig. 31A.— Vervoort, 2006: 272–273. Obelia bifurcata : Billard, 1906a: 71. Laomedea bicuspidata : Vervoort, 1946: 344–345, fig. 10A–B.— Buchanan, 1957: 359. Obelia bicuspidata : Patriti, 1970: 36, fig. 46. Obelia oxydentata : Picard, 1951a: 110.

Material examined. BISSAU-0810, stn BS134, 11º28'17"– 11º29'11"N, 17º13'12"– 17º13'22"W, 374–385 m, 23-X-2008: one colony 36 mm high without gonothecae, substrate unknown.

BISSAU-0810, stn BS142 11º14'17"– 11º13'22"N, 17º13'07"– 17º13'12"W, 335–393 m, 25-X-2008: two colonies, 25–35 mm high without gonothecae, substrate unknown.

BISSAU-0810, stn BS147, 11º08'35"– 11º08'27"N, 17º11'31"– 17º10'37"W, 186–306 m, 26-X-2008: two colonies, 21–139 mm high without gonothecae, substrate unknown.

BISSAU-0810, stn BS152, 10º31'12"– 10º30'19"N, 17º12'34"– 17º12'32"W, 300–305 m, 27-X-2008: eight colonies without gonothecae, 4–30 mm high, of which one growing on Aglaophenia lophocarpa , one on Lytocarpia myriophyllum , one on Diphasia margareta , one on a worm tube and one on a bryozoan.

BISSAU-0810, stn BS216, 10º30'53"– 10º31'39"N, 16º31'33"– 16º32'02"W, 56–58 m, 7-XI-2008: two colonies, 35–36 mm high with gonothecae, substrate unknown.

CCLME 2012-404 , stn SL-04, 10º48’29’’N, 16º34’57’’W, 32 m, 18-V-2012: two colonies up to 20 mm high without gonothecae, both growing on Eudendrium sp .

Remarks. The large and deep, campanulate hydrothecae provided with about 10 bicuspidate cups on the hydrothecal rim are diagnostic for this species.

Biology. Obelia bidentata colonizes a great variety of substrates, such as rocks, bio-concretions, algae, seagrasses, hydrozoans, bryozoans, worm tubes, mollusk shells (sometimes inhabited by hermit crabs), isopods, cirripedes, ascidians, wreck hulls and fouling communities ( Cornelius 1995b; Peña Cantero & García Carrascosa 2002). In the northern hemisphere, gonothecae have been found in February ( Vervoort 1959; Gili et al. 1989) and between May and December ( Peña Cantero & García Carrascosa 2002; Gil & Ramil 2017a).

In our material, colonies were found growing on the hydroids A. lophocarpa , L. myriophyllum , D. margareta and Eudendrium sp. , as well as on worm tubes and bryozoans. Gonothecae were found in November.

Distribution. This species has mainly a circumglobal distribution in tropical and temperate waters ( Peña Cantero & García Carrascosa 2002; Gil & Ramil 2017a), but it has also been recorded from the Southern Ocean ( Peña Cantero 2004). In West Africa, it has been collected from Morocco ( Patriti 1970), Western Sahara ( Vervoort 1946, as Laomedea bicuspidata ), Mauritania ( Billard 1906a, as Obelia bifurca ; Medel & Vervoort 2000; Gil & Ramil 2017a), the Cape Verde region ( Medel & Vervoort 2000), Senegal ( Picard 1951a, as Obelia oxydentata ), Gambia [ Vervoort 1959, as L. (Obelia) bicuspidata ], Guinea-Bissau [ Vervoort 1959, as L. (Obelia) bicuspidata ; Gili et al. 1989], Ghana [ Buchanan 1957, as L. bicuspidata ; Vervoort 1959, as L. (Obelia) bicuspidata ] and Nigeria [ Vervoort 1959, as L. (Obelia) bicuspidata ]. Its bathymetric distribution extends from 0.5 ( Calder 1991) to 2600 m ( Vervoort 2006).

Our material was collected at depths between 32–385 m.