Halopteris infundibulum

Description Stems upright and quite rigid, simple, monosiphonic, ca 8 cm high, arising from reticulate hydrorhiza; composed of long (5 – 6 cm) proximal part devoid of hydrothecae and hydrocladia, and comparatively shorter (2 – 3 cm) distal part bearing hydrothecae and hydrocladia. Proximal part with few closely-set transverse nodes immediately above origin from stolon, as well as few, irregular, more distant ones above; nematothecae in two closely-set, longitudinal rows, only in distal part of this portion of stem; nematothecae alternate along most length of nematothecate part of stem, distalmost ones being gradually arranged in subopposite to opposite pairs. Upper part of stem starting with two consecutive prosegments delimited at both ends by deeply-incised, very oblique nodes, each comprising a proximally-placed, quite damaged hydrotheca, 11 nematothecae, and cladial apophysis arising only from side of second hydrotheca; nematothecae: one mesial, two pairs of laterals, as well as 3 opposite pairs above hydrotheca, in two closely-set, longitudinal rows. Remainder of stem slightly geniculate, with faintly-marked to almost imperceptible segmentation through slightly oblique nodes; each internode with hydrotheca proximally, short cladial apophysis laterally, and at least 9 nematothecae: one mesial, two pairs of laterals and 2 pairs above hydrotheca; presence of axillar nematotheca could not be checked properly, for cladial apophyses being shifted on to anterior part of stem, forming acute angle between two rows. Cladia up to 5 mm long, bearing up to 11 hydrothecate internodes; proximally short, almost indistinct, athecate internode, with proximal node straight and distal node oblique; nodes on remainder of cladium generally indistinct but, when present, transverse, immediately above each hydrotheca; each internode with hydrotheca, flanked by double pair of nematothecae, as well as 3 – 4 additional nematothecae above; anterior pair of laterals borne on conspicuous apophyses, thecae projecting above hydrothecal rim; posterior pair sessile, at base of apophyses supporting anterior pair; proximalmost nematotheca among those situated between consecutive hydrothecae always situated behind adaxial wall of proximal hydrotheca, either decidedly in axil or certain distance above. All nematothecae conical, bithalamic, wall of upper chamber slightly lowered on adaxial side. Hydrotheca tubular, rather deep, ¾ rd adnate, abaxial wall straight or nearly so, aperture circular, forming an angle of ca 40 ° with internode. Single gonotheca arising laterally from below basis of cladial hydrotheca; urn-shaped, slightly flattened, tapering abruptly basally, distally truncate, and there provided with ovoid, deciduous, filmy flap; two exceedingly long nematothecae inserted at above ¼ rd of its length.

Figs 14 L – M, 15 C

Remarks The present material agrees generally well with the type (Vervoort 1966; Schuchert 1997) and specimens examined by Vervoort & Watson (2003) and Ansín Agís et al. (2009), although it shows a number of differences: 1) it bears 2 opposite pairs of nematothecae above the cauline hydrothecae, while the occurrence of only two nematothecae in a row has been documented previously; 2) there are 3 – 4 nematothecae, instead of only two as documented earlier, between two successive cladial hydrothecae, of which the proximalmost can be either decidedly axillar or situated a short distance above the axil; 3) the gonotheca is urn-shaped and not piriform, as described by Vervoort & Watson (2003), and bears 2 exceedingly long nematothecae. I can see little reason to separate specifically the present material from that described earlier, as the species is still poorly-known, and the intraspecific variation insufficiently documented. The gonotheca in my material could belong to the opposite sex with respect to that described earlier by Vervoort & Watson (2003); as to the length of the nematothecae it carries, this could likely not be used as a valid taxonomic criterion at this stage, given that, in this hydroid, at least the lateral nematothecae display a “ very variable ” length (Vervoort & Watson 2003).

Distribution Tasman Sea (Vervoort 1966), New Zealand (Vervoort & Watson 2003), New Caledonia (Ansín Agís et al. 2009; present study).

Material examined PACIFIC OCEAN • 2 stems, both ca 8 cm high, 1 bearing a (damaged) gonotheca; off New Caledonia, stn DW 5026; 20 ° 22 ′ S, 158 ° 40 ′ E; 360 – 410 m; 21 Sep. 2016; KANADEEP leg.; MNHN-IK- 2015 - 608.