Schizoplumularia vervoorti, Agís, José Ansín, Ramil, Fran & Calder, Dale R., 2016

Agís, José Ansín, Ramil, Fran & Calder, Dale R., 2016, One new genus and three new species of plumulariid hydroids (Cnidaria, Hydrozoa, Plumulariidae) from the western Pacific Ocean, with a re-examination of Plumularia insignis Allman, 1883 and related taxa, Zootaxa 4169 (1), pp. 57-86 : 61-64

Schizoplumularia vervoorti n. sp.

( Figs 2‒3 ; Table 2)

Material examined. Fiji. MUSORSTOM 10, stn CP 1364, 18º11,9'S, 178º34,5'E, 80‒86 m, 15-VIII-1998: one fragment 45 mm high with female? gonothecae, holotype ( MNHN-IK-2012-16600).

Western Pacific Ocean. Stn without label. One damaged colony 75 mm high, no gonothecae, paratype ( MNHN-IK-2012-16601; RMNH.Coel.42070).

Etymology. The specific name vervoorti honours Dr Willem (Wim) Vervoort (1917–2010) for his extensive and important contributions to hydrozoan taxonomy.

Distribution. Currently known only from Fiji, at depths between 80‒ 86 m. A second colony, without accurate station data, was collected in the western Pacific region.

Description. Examined colonies both fragmentary with missing hydrorhizae, each comprising an erect, polysiphonic, geniculate main axis giving rise to alternate, monosiphonic hydrocauli bearing alternate hydrocladia. In holotype, base of main axis with three tubes, one primary and two accessory, with only primary tube bearing apophyses and hydrocladia along proximalmost 25 mm. At approximately 17 mm from base, one of two accessory tubes disappearing; further on, primary tube giving rise to first hydrocaulus of colony and to a new secondary axial tube adhering to remaining secondary tube. This remaining secondary axial tube giving rise to a second hydrocaulus on opposite side of main axis, and at same point to a new secondary axial tube adhering to secondary axial tube formed in axil of first branch. Above second branch, main axis comprising two tubes broken, with remainder of colony lost. In paratype, main axis distinctly geniculate, with four tubes along entire length; hydrocauli alternate, long, curved, graceful, conferring distinctive appearance to colony. Two central accessory tubes of main axis fused and interconected along their entire length. Lateral tubes (secondary axial tubes) giving rise to hydrocauli and to a supplementary attached tube near origin of each branch towards apical end. Hydrocauli divided into internodes by slightly oblique nodes; each internode with two or three apophyses, these alternately directed to left and right, and slightly frontally. Each apophysis with a mamelon on upper surface, with two axillary nematothecae, and with one perisarcal ring at distal end. One to three nematothecae placed irregularly between two consecutive apophyses. Hydrocladia beyond apophyses homomeric, consisting of a succession of hydrothecate internodes with slightly oblique nodes, each internode with one hydrotheca on distal half and with four nematothecae, two mesial inferior and two lateral. Hydrothecae cup-shaped, widening towards margin, adcauline wall fully adnate, abcauline wall straight, aperture circular, tilted downwards, rim smooth. Mesial inferior nematothecae two, with one near basal node arising on a small elevation and another near middle of internode. Lateral nematothecae longer than mesial inferior ones. All nematothecae conical, bithalamic, movable. Each internode with two internal perisarc rings near extremities.

Gonothecae inserted on apophyses; each one pear-shaped, with circular terminal aperture closed by an operculum; nematothecae absent.

Variability. Ahydrothecate internodes sometimes appear on the hydrocladia as a result of damage and subsequent regeneration. Such internodes have one nematotheca, with the following hydrothecate internode bearing a single mesial inferior nematotheca.

FIJI stn CP 1364

Height of colony (in mm) 44 Length hydrothecate hydrocladial internodes 610‒830 Diameter at node 45‒50 Hydrotheca

Length abcauline wall 65‒80 Length adcauline wall 70‒90 Diameter at rim 70‒80 Mesial nematotheca, length 60‒70 Diameter at rim 25‒35 Lateral nematotheca, length 90‒130 Diameter at rim 30‒40 Gonotheca, length 580‒660 Greatest diameter 230‒260 Remarks. Schizoplumularia vervoorti n. sp. somewhat resembles Plumularia antonbruuni Millard, 1967 in the morphology of its hydrothecae, with hydrothecal rims tilted down, and in having two mesial inferior nematothecae. However, dimensions of both internodes and hydrothecae are larger in P. antonbruuni . Moreover, clear differences exist in the structure of the colonies, with those of P. antonbruuni having monosiphonic and unbranched hydrocauli that arise from a hydrorhiza, and those of S. vervoorti having similar hydrocauli that arise from a main axis that is polysiphonic and geniculate.

Millard (1967) described only male gonothecae in her original account of P. antonbruuni . Later, both male and female gonothecae of the species were described on the same colony by Rees & Vervoort (1987). In S. vervoorti , observed gonothecae, probably female, were uniform in morphology and different from descriptions of Millard (1967) and Rees & Vervoort (1987).

Figures

FIGURE 2. Schizoplumularia vervoorti n. sp. A, holotype (MUSORSTOM 10, stn CP 1364), B – E, paratype (stn without label). A, habit of colony. B, habit of colony; C, fragment of colony, with accessory tube (arrow); D, cross-section of stem, showing component tubes; E, detail of polysiphonic main stem, showing origins of alternate hydrocauli and peculiar secondary axial tubes that originate in the axils of consecutive hydrocauli (accessory tube not illustrated). Scales: A and B, 1 cm; C, 0. 5 mm; D, 0.1 mm; E, 1 mm.

FIGURE 3. Schizoplumularia vervoorti n. sp. A ‒ E, holotype (MUSORSTOM 10, stn CP 1364); A, proximalmost internodes of a hydrocladium; B ‒ C, internodes, frontal view; D, internode, lateral view; E, gonotheca. Scales: a ‒ e, 0.1 mm.