Hydrodendron mirabile ( Hincks, 1866 )

Hydrodendron mirabile ( Hincks, 1866) View in CoL

Ophiodes mirabilis Hincks, 1866: 422–423 View in CoL , pl. 14 figs 1–5.

Hydrodendron mirabile View in CoL : Gili et al., 1989: 81–82, fig. 10B.— Bouillon et al., 1995: 47.— Cornelius, 1995a: 309–311, fig. 73.— Medel & Vervoort, 2000: 26–28.— Peña Cantero & García Carrascosa, 2002: 81–82, fig. 16 b–c.— Choong et al., 2018: 60–61, fig. 12.

Ophiodissa caciniformis : Ritchie, 1907: 500–501, pl. XXIII figs 11–12, pl. XXIV fig. 1, pl. XXV fig. 5.— Vervoort, 1959: 218–221, figs 1, 2.

Hydrodendron caciniformis View in CoL : Millard, 1975: 158–160, fig. 51A–F.

Material examined. BISSAU-0810, stn BS191, 10º18'25"– 10º19'20"N, 16º08'47"– 16º08'47"W, 24–25 m, 3-XI-2008: one colony without gonothecae, growing on a bryozoan.

Remarks. For many years, some authors have noted the need to evaluate the appropriateness of the inclusion of the genus Hydrodendron Hincks, 1874 within the family Haleciidae ( Watson 1969; Cornelius 1975), due to the presence of nematophores. Furthermore, during the last decades, several molecular studies have shown a clear divergence between Hydrodendron and Halecium species ( Maronna et al. 2016). Moreover, the peculiar morphological characters of H. mirabile are shared with genera of the superfamily Plumularioidea ( Choong et al. 2018) . Consequently, several authors proposed to include this species in the family Phylactothecidae within the superfamily Plumularioidea to accommodate all the species belonging to the genus Hydrodendron (see Choong et al. 2018), an opinion followed here.

Biology. This species has been often collected growing on algae, but also on rocks, seagrasses, hydroids and other invertebrates ( Peña Cantero & García Carrascosa 2002). In the northern hemisphere, fertile material has been collected in July in the Mediterranean ( Motz-Kossowska 1911).

The colony studied by us was found growing on a bryozoan.

Distribution. Hydrodendron mirabile is an Indo-West Pacific species restricted to tropical and temperate waters ( Peña Cantero & García Carrascosa 2002). In West Africa, it has been recorded from the Cape Verde Archipelago ( Ritchie 1907, as O. caciniformis ; Rees & Thursfield 1965, as H. caciniformis ), Guinea-Bissau ( Vervoort 1959, as O. caciniformis ; Gili et al. 1989) and Congo ( Bouillon et al. 1995). Its bathymetric range extends from 0 (Millard 1975; Ramil & Iglesias 1988, as O. mirabilis ) to 65 m ( Vervoort 1959, as O. caciniformis ).

Our material was collected at depths between 24–25 m.

CHECKLIST OF THE HYDROIDS REPORTED FROM GUINEA-BISSAU

In the checklist provided below, we have also included the taxa identified by Moura et al. (2024). Nevertheless, we believe that the hydroid species cited in this study should be taken with caution, due to all species identifications were based only on morphospecies separation and molecular analyses, as the proper authors recognize. Of the 15 hydrozoan species mentioned there, 11 are identified as cf. or aff. An integrative taxonomic study with formal taxonomic descriptions, drawings and biometric date of the sequenced material is required to confirm their identifications or to describe putative new species. Records of species dealt with by Moura et al. (2024) are marked with an asterisk.