Hincksella cornuta, 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 : 13-15

Hincksella cornuta sp. nov.

urn:lsid:zoobank.org:act:5DC46422-9914-47FF-8CE3-49AB51B0014A

Fig. 5 A–D; Table 3

Diagnosis

Stems simple, monosiphonic, nodes indistinct; internodes relatively short, slightly geniculate, each carrying a hydrotheca; the latter alternate, tubular, bent in middle; rim often renovated; gonothecae arising from within the hydrothecae, broadly ovoid, lateral walls wrinkled; two prominent horns distally.

Etymology

From the Latin, cornūtus, meaning "horned", making reference to the prominent horns of the gonotheca.

Material examined

Holotype

NEW CALEDONIA: campaign Bathus 4, station DW923, 18°52’ S, 163°24’ E, 502– 470 m, 6 Aug. 1994; whole stem 3.6 cm high, bearing two fully-formed gonothecae (IK-2012-10297).

Paratypes

NEW CALEDONIA: data as for holotype, four specimens (3.1 cm high fragment with no basal part, bearing two gonothecae; 3.3 cm high fragment devoid of its basal part; entire, 4.0 cm high stem with one gonotheca; entire, sterile stem 3.8 cm high) (IK-2012-10298).

Description

Stems erect, up to 3.8 cm high, unbranched and monosiphonic, arising from tubular hydrorhizae; basal constriction at origin from stolon; lower parts ahydrothecate and quite long (1.0– 1.2 cm), occasionally with signs of breakage and subsequent regeneration; perisarc smooth. Division by nodes indistinct, but equivalents of internodes rather short, slightly geniculate, bearing single hydrothecae on distal halves. Hydrothecae alternate, although the two proximal-most ones may be given off on same side of stem; tubular, adnate for less than half of length; free part facing out- and upward; free adcauline wall slightly convex to almost straight; abcauline wall convex in middle and straight elsewhere; basal foramina with multiple renovations of perisarc ( Fig. 5C ); rim of hydrotheca often renovated; aperture circular, imperceptibly tilted adaxially. Hydranths enveloped by inner, thin, collapsible periderm, distinct from hydrothecal wall; tentacle number could not be counted. Gonothecae given off from within hydrothecae; broadly ovoid, with wrinkled perisarc, distally with two prominent horns; no signs of aperture; gonophore apparently single, large ovoid mass (oocyte?) occupying nearly entire lumen of gonotheca. 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, the gonothecae given off from within the hydrothecae, as well as the large macrobasic heteronemes (mastigophores?) scattered in the coenosarc place this species in the genus Hincksella Billard, 1918 . The two horns on the distal part of its gonothecae distinguish this species from its congeners with known gonosomes, viz. H. alternans ( Allman, 1888) (see original description), H. formosa (Fewkes, 1881) (see Galea 2013), H. pusilla Ritchie, 1910 (see Galea & Ferry 2015), and H. sibogae Billard, 1918 (see Vervoort & Watson 2003).

The remaining congeners with unknown gonothecae differ from H. cornuta sp. nov. in the following respects: 1) H. corrugata Millard, 1958 has comparatively shorter hydrothecae, adnate for as much as half their length, and their surface is transversely wrinkled ( Millard 1958); 2) H. indiana Millard, 1967 is a much larger species, with fascicled stems, shorter hydrothecae, conspicuously tilted adaxially ( Millard 1967); 3) the poorly described H. projecta ( Fraser, 1938) appears to be different due to the lower length/width ratio of its hydrothecae, as well as on biogeographical grounds ( Fraser 1938); 4) the hydrothecae of H. rigida ( Fraser, 1938) are nearly as broad as deep and, according to Fraser (1938), they are comparatively shorter.

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.