Diphasia anaramosae, Gil & Ramil, 2017

Gil, Marta & Ramil, Fran, 2017, The genus Diphasia L. Agassiz, 1862 (Cnidaria, Hydrozoa) in Northwest Africa, Zootaxa 4363 (3), pp. 301-349 : 339-341

Diphasia anaramosae n. sp.

( Fig. 19 , Table 12)

Diphasia delagei: Ramil & Vervoort, 1992: 200 –201, fig. 56A (not Diphasia delagei Billard, 1912 ).

Material examined. Morocco. MAROC-0411, stn MO14, 35º31´08"– 35º29´25"N, 6º27´51"– 6º27´17"W, 724– 720 m, 18-XI-2004: one colony 2 mm high growing on Diphasia margareta , with a male gonothecae, holotype ( MNCN 2.03 /683).

Etymology. The specific name anaramosae is in honor of our colleague and friend Dr. Ana Ramos, Instituto Español de Oceanografía, in appreciation and recognition of her extensive and important contributions to the study of benthic fauna in Northwest African coasts.

Biology. The single colony was found growing on D. margareta on muddy bottoms; the colony, collected in November, was fertile. Previously, the species has been recorded on Diphasia sp. and S. gayi gayi ( Ramil & Vervoort 1992, as D. delagei ).

Distribution. This species is known from two localities off Cape Spartel, Morocco, between 150 and 1250 m ( Ramil & Vervoort 1992). The present material was obtained from the same area and was collected at a depth of 720– 724 m.

Description. Small colony, composed by some erect, monosiphonic and unbranched axes arising from a creeping hydrorhiza growing on the axis of D. margareta .

Axis divided into internodes by little marked transverse nodes, and each internode bearing one pair of opposite hydrothecae along the length of a hydrocladium; sub-opposite hydrothecae were not observed.

Hydrothecae tubular, adnate from 1/3 to half of its length and curving outwards at an angle of ca. 45°. Free part of the adcauline wall almost straight. Abcauline wall concave, with slightly and evenly thickened perisarc all along its length but without any internal folds. Hydrothecal rim smooth with adcauline sinus; aperture semi-circular, oriented upwards and closed by a one-flap operculum attached to the adcauline sinus; presence of an internal lamina attached to the free part of the adcauline wall is also very common (fig. 19A). Renovations of the hydrothecal border are very frequent and sometimes very numerous; in this case, the free part of the hydrothecae was curved upwards. All external surfaces of the hydrotheca show numerous and fine transverse striae slightly marked, which is characteristic of this species.

Male gonotheca, the only one observed, arises from the axis on a short pedicel under the base of a hydrotheca. The gonotheca is pear-shaped, with a narrow base and a distal part distinctly hexagonal in the cross-section. The external wall has six longitudinal ribs well-developed in the distal half. The upper part is flat, with the six ribs curving at a right angle on the top and surrounding a central and circular aperture located at the end of a conical process (fig. 19B).

Remarks. Diphasia anaramosae n. sp. shows affinities with Diphasia delagei Billard, 1912 , especially with respect to the morphotype with the hydrothecae vertically separated. Nevertheless, the axis lacks the athecate basal part, and the ornamentation of the hydrothecae is formed by fine and very numerous transverse striations in Diphasia anaramosae n. sp., whereas the axis of D. delagei shows an athecate basal part separated by an oblique node from the thecate part and its hydrothecae have more developed transverse ridges that are not so closely packed. In addition, morphology of the male gonotheca, the only known one in both species, is clearly different: in D. delagei , it is S-shaped with well-developed transverse ridges throughout, while, in Diphasia anaramosae n. sp., it is pear-shaped and has six longitudinal ribs but no transverse ridges or striae.

Differences with D. tropica have been explained below.

MAROC-0411 BALGIM Stn MO14 Stn CP62 Diphasia tropica Nutting, 1904: 110 , pl. XXX, fig 1; van Gemerden-Hoogeveen, 1965: 17–21, figs. 1–5; Calder, 1991: 88–89, fig. 46.

Diphasiella ornata Vannucci, 1949: 239 –240, pl.II, figs. 26–28.

Remarks. Diphasia tropica is not represented in the material studied in this report, but it has been included here because Buchanan (1957) recorded it in Northwest Africa. This species approaches D. delagei and Diphasia anaramosae n. sp. by the transverse striation of the hydrothecal wall. Differences with D. delagei have been already discussed by Cornelius (1979), Calder (1991) and Ramil & Vervoort (1992) and deals with the pentagonal cross-section of the hydrothecae with five longitudinal ribs crossed by transverse striation and the morphology of the gonotheca, oval in shape and with many spines disposed in irregular longitudinal rows in D. tropica . The same differences also apply to Diphasia anaramosae n. sp.

Diphasia tropica seems to be an amphi-Atlantic species, mainly known in the Western Atlantic, with many records in the Caribbean Sea (summarized by Calder & Kirkendale 2005), Bermuda ( Calder 1991) and Brazil (see Migotto et al. 2002). In the Eastern Atlantic, it was only reported in Ghana ( Buchanan 1957).

Figures

FIGURE 19. Diphasia anaramosae n. sp. A–B, stn MO14; A, part of hydrocladium; B,male gonotheca.Scales: a–b, 0.5 mm.