Zygophylax sp.

Gil, Marta & Ramil, Fran, 2021, Hydroids (Cnidaria, Hydrozoa) from the Vema and Valdivia seamounts (SE Atlantic), European Journal of Taxonomy 758, pp. 49-96 : 57-59

Zygophylax sp.

Fig. 3A–C ; Table 2

Zygophylax? biarmata – Millard 1958: 176–177, fig. 4a; 1975: 193, fig. 63c.

Material examined

SOUTH ATLANTIC OCEAN • 29 colonies, 16–61 mm high (1 growing on ghost fishing net), without coppiniae; Valdivia Seamount, stn BT12; 24°49′01″–24°47′38″ S, 6°24′40″–6°25′26″ E; 887– 886 m depth; 7 Feb. 2015;SEAFO-2015 leg.; SEAFO-2015-40192 , SEAFO-2015-40282 , SEAFO-2015-40432 , SEAFO-2015-40492 , SEAFO-2015-40767 , SEAFO-2015-40811 , SEAFO-2015-40827 , LZM-UV slide R. 580 .

Description

Colonies branched, stems erect, with a main primary tube surrounded by many secondary tubes, grading to monosiphonic distally. Lateral hydrocladia, originating from the primary tube, monosiphonic, forming an angle of 45° in all directions around the stem, always with an axillary hydrotheca. Some branches are occasionally branched once (secondary hydrocladia). The existence of internodes in both the stem and branches was not observed. Main stem and branches with the same structure and provided with alternately disposed hydrothecal apophyses, slightly directed to the ‘frontal’ side of the colony ( Fig. 3B ). Some isolated apophyses and hydrothecae were also observed arising from secondary tubes.

Hydrothecae slightly shifted frontally, long, tubular, with the adcauline wall convex and the abcauline wall almost straight; basal part tapering below into a short pedicel, separated from hydrotheca by a slightly oblique, thin diaphragm; rim smooth, circular and slightly everted; renovations of the hydrothecal rim common and usually multiple; diaphragm occasionally renovated as well. Nematothecae inserting on small apophyses, usually one on each side of hydrotheca, but when lost, only a circular depression, corresponding to their origin, could be observed; tubular, with short, spherical pedicel; rim smooth, circular, slightly everted; renovations absent ( Fig. 3C ).

Variabillity

In one colony we found one hydrocladium that was polysiphonic at its basal part and distally monosiphonic.

Remarks

Our material clearly resembles Zygophylax biarmata Billard, 1905 , but the hydrothecae are larger and, in addition, the arrangement of branches in all directions around the stem makes it easy to differentiate between species, as Z. biarmata presents branches that are arranged in the same plane as the main stem.

Among all species of Zygophylax reported from West Africa, only one, Z. parabiarmata Vervoort, 2006 , shows the lateral branches arranged in several planes, but in this case hydrothecae are arranged in different planes as well, whereas in Zygophylax sp. hydrothecae are almost in the same plane. Moreover, in Zygophylax sp. hydrothecae are longer and narrower than in Z. parabiarmata .

Nevertheless, the material studied here agrees with that described by Millard (1958, 1975) as Zygophylax ? biarmata (not Z. biarmata Billard, 1905 , see Ramil & Vervoort 1992: 60–65) in both measurements and the irregular disposition of the lateral branches around the stem, and the occasional presence of

hydrothecae on secondary tubes. Consequently, we consider that all belong to the same species, but the absence of coppinia prevents us from assigning this material to a new species.

Distribution

This species has previously been recorded from off Natal, South Africa ( Millard 1958, 1975, as Zygophylax ? biarmata ), at depths of 164 to 333 m.

Figures

Fig. 3. A–C. Zygophylax sp. A. Colony. B. Distal part of colony with hydrocladia. C. Part of hydrocladia with two hydrothecae. — D–E. Stegopoma giganteum Ramil & Vervoort, 1992. D. Hydrotheca on pedicel. E. Gonotheca. — F. Campanulina denticulata Clarke, 1907, part of colony ramified with hydrothecae. — G–H. Campanularia africana Stechow, 1923, detail of hydrotheca, lateral view.