Hincksella similis, Galea, 2015

Galea, Horia R., 2015, Two new genera and nine new species of hydroids (Cnidaria: Hydrozoa) from off New Caledonia, European Journal of Taxonomy 135, pp. 1-19 : 16-17

Hincksella similis sp. nov.

urn:lsid:zoobank.org:act:DBF94D6B-02BA-4364-B599-A411A95D8EC5

Fig. 5 G–H; Table 3

Diagnosis

Stems simple, monosiphonic; nodes indistinct; each internode with a distal hydrotheca; the latter long, tubular, distinctly facing outward, finely and densely striated on free adcauline wall and lower part of abcauline wall.

Etymology

From the Latin similis , meaning "similar", on account of its resemblance to H. pusilla Ritchie, 1910 .

Material examined

Holotype

NEW CALEDONIA: campaign Norfolk 1, station DW1722, 23°18’ S, 168°10’ E, 540 m, 26 Jun. 2001; sterile, 2.2 cm high stem (IK-2012-10300).

Description

Colony erect, 2.2 cm high, arising from creeping, tortuous, branching stolon. Stem monosiphonic, unbranched; basal part 9 mm long, ahydrothecate; remainder of stem divided by means of indistinct nodes; each equivalent of internode rather short, slightly geniculate to almost collinear, each bearing a hydrotheca distally. Hydrothecae tubular, given off at an angle of c. 65–70° with internode, long axis slightly sigmoid; abcauline wall markedly curved where hydrotheca becomes free; aperture rounded, rim even, slightly flared; renovations occasional; perisarc of hydrotheca finely and densely striated, especially on free adcauline side and proximal part of abcauline wall. Gonotheca unknown. Large macrobasic heteronemes (none seen discharged), with parallel walls and rounded ends, and with straight or slightly curved longitudinal axes, occur abundantly in coenosarc.

Remarks

The alternate, long, tubular, non-operculate hydrothecae and the large nematocysts scattered in the coenosarc place this species, with little doubt, in the genus Hincksella Billard, 1918 . This species resembles both H. pusilla Ritchie, 1910 , through the shape of its hydrothecae, and H. neocaledonica sp. nov. through their striations. However, the former is a much smaller species (see dimensions in Galea 2010: table 3), while the latter has comparatively longer and more geniculate internodes, its hydrothecae are given off at more acute angles, their free part is shorter, and the striations extend over the whole perisarc of the colony.

Figures

Fig. 5. — A–D. Hincksella cornuta sp. nov. A. Basal portion of stem with hydro- and gonothecae. B. Hydrotheca. C. Detail of the foramen for the passage of the hydranth into hydrotheca. D. Gonotheca arising from within a hydrotheca. — E–F. Hincksella neocaledonica sp. nov. E. Portion of stem. F. Hydrotheca, showing outer striations. — G–H. Hincksella similis sp. nov. G. Portion of stem. H. Hydrotheca, showing extent of external striations. Scale bars: A, E, G = 1 mm; B, D, F, H = 500 μm; C = 200 μm.