Halecium delicatulum Coughtrey, 1876

Gil, Marta & Ramil, Fran, 2025, Hydroids (Cnidaria, Hydrozoa) from Guinea Bissau, Zootaxa 5577 (1), pp. 1-89 : 38-39

Halecium delicatulum Coughtrey, 1876

Halecium delicatulum Coughtrey, 1876: 26 , pl. 3 figs 4–5.— Patriti, 1970: 23–24, fig. 20.—Millard, 1975: 145–147, fig. 47 F–L.— Gili et al., 1989: 78.— Ramil & Vervoort, 1992a: 82–85, fig. 20A–C.— Migotto, 1996: 30–31, fig. 6 D–L.— Medel & Vervoort, 2000: 12–13.— Peña Cantero & García Carrascosa, 2002: 63–66, fig. 12A–B.— Vervoort & Watson, 2003: 88–90, figs 15I–L, 16A–E.— Schuchert, 2005: 629–631 , fig. 12.

Halecium gracile : Billard, 1906b: 163–164.

Halecium parvulum : Vervoort, 1959: 227–229, fig. 7.

Material examined. BISSAU-0810, stn BS191, 10º18'25"– 10º19'20"N, 16º08'47"– 16º08'47"W, 24–25 m, 3-XI-2008: six colonies without gonothecae, of which two growing on Idiellana pristis , one on Tridentata loculosa and one on a bryozoan.

BISSAU-0810, stn BS192, 10º19'30"– 10º20'15"N, 16º10'27"– 16º10'59"W, 24 m, 3-XI-2008: two colonies 10 mm high, without gonothecae, growing on bryozoans.

BISSAU-0810, stn BS193, 10º21'13"– 10º21'51"N, 16º10'17"– 16º10'56"W, 20–21 m, 3-XI-2008: 47 colonies (one with male and two with female gonothecae), 4–16 mm high, of which 45 growing on bryozoans.

BISSAU-0810, stn BS194, 10º21'59"– 10º22'36"N, 16º13'23"– 16º14'03"W, 21–24 m, 3-XI-2008: five colonies without gonothecae, 7–24 mm high, of which three growing on bryozoans.

BISSAU-0810, stn BS195, 10º22'44"– 10º23'22"N, 16º15'37"– 16º16'18"W, 29 m, 3-XI-2008: 13 colonies without gonothecae, 5–77 mm high, of which 10 growing on bryozoans and one on Idiellana pristis .

BISSAU-0810, stn BS226, 11º22'11"– 11º21'55"N, 17º02'30"– 17º01'54"W, 35–37 m, 9-XI-2008: one colony without gonothecae growing on Sertularelloides cylindritheca .

Remarks. The presence of female gonothecae and the morphology of the colony allowed us to identify the present material as H. delicatulum .

Halecium mediterraneum Weismann, 1883 was considered a synonym of H. delicatulum by Ralph (1958), Rees & Vervoort (1987), Ramil & Vervoort (1992a) and Peña Cantero & García Carrascosa (2002). Schuchert (2005) described slight differences between colonies collected from New Zealand and the Mediterranean Sea. These differences were related to the variability of the female gonothecae, the number of eggs per gonotheca and the color and shape of the colonies, but he also pointed out that they may not be truly representative, and that the two nominal species are almost indistinguishable. Nevertheless, and mainly for biogeographical reasons, he kept the two species separate until a molecular approach clarifies their relationships.

Given that almost all hydrozoan taxonomists in the last century have accepted the synonymy between H. delicatulum and H. mediterraneum , and that Schuchert’s conclusion is speculative, we prefer to keep the West African material under the name Halecium delicatulum Coughtrey, 1876 .

Biology. This species colonizes living substrates, such as rhizomes of Posidonia oceanica , sponges, other hydroid species, anthozoans, mollusk shells, worm tubes, bryozoans, cirripedes and ascidians ( Medel & Vervoort 2000; Peña Cantero & García Carrascosa 2002). In the northern hemisphere, gonothecae were found from April to September ( Peña Cantero & García Carrascosa 2002), while in the southern hemisphere, fertile colonies were found in March, June, July, August, October and November ( Migotto 1996; Vervoort & Watson 2003).

In our material, colonies were found growing on hydroids and bryozoans. Gonothecae were observed in November.

Distribution. Halecium delicatulum is a circumglobal species ( Schuchert 2005). In West Africa, it has been collected from Morocco ( Billard 1906b, as H. gracile ; Patriti 1970; Ramil & Vervoort 1992a), Mauritania ( Billard 1906a, as H. gracile ; Medel & Vervoort 2000; Gil & Ramil 2017a), Senegal, Guinea-Bissau and Ghana ( Vervoort 1959, as H. parvulum ; Gili et al. 1989). Its bathymetric distribution ranges from 0 (Millard 1975) to 2250 m ( Vervoort & Watson 2003).

Our colonies were collected at depths between 20–37 m.