Diphasia cristata Billard, 1920

Galea, Horia R., 2016, Notes on some sertulariid hydroids (Cnidaria: Hydrozoa) from the tropical western Pacific, with descriptions of nine new species, European Journal of Taxonomy 218, pp. 1-52 : 4-5

Diphasia cristata Billard, 1920

Fig. 1 C–J

Diphasia cristata Billard, 1920: 147 , fig. 1f.

Diphasia cristata – Billard 1925b: 218, fig. 57, pl. 3 fig. 32. ― Hirohito 1983: 38, fig. 15; 1995: 161, fig. 51a–c.

Material examined

SMIB 4: Stn. DW57, several sterile stems and fragments, up to 2.5 cm high (MNHN-IK-2012-16509).

SMIB 6: Stn. DW127, a female colony composed of several stems up to 4 cm high, epizoic on Gonaxia sp. (MNHN-IK-2012-16510).

MUSORSTOM 8: Stn. DW1021, small female colony composed of a few stems, up to 2 cm high, epizoic on Caminothujana molukkana (MNHN-IK-2012-16511).

BORDAU 1: Stn. CP1447, small female colony composed of several stems up to 2.4 cm high (MNHN- IK-2012-16512); Stn. CP1448, dense, fertile colony (or colonies?), up to 4 cm high, on dead antipatharian (MNHN-IK-2012-16513).

BORDAU 2: Stn. DW1513, male and female colonies with stems up to 1.5 cm high, on antipatharian and aglaopheniid hydroid (MNHN-IK-2012-16514).

Remarks

This species is immediately recognizable through the presence of five prominent, longitudinal, perisarcal crests running over the whole body of hydrothecae, as well as of an additional one found on the dorsal side of the internodes. For the most recent description, see Hirohito (1995). It should be noted that the oblique node demarcating the junction between the basal, ahydrothecate part and the main, distal, hydrothecate part of the stems and side branches is not always present in the material examined here.

The gonothecae of this species, hitherto unknown, are described from the present material. Male and female gonothecae present, each sex borne on different stems, but, due to their high density and the numerous branches and anastomoses of the stolon, it is impossible to determine if it is a single colony or whether several colonies are represented. The male gonothecae ( Fig. 1 I–J) are 1505–1580 µm long, ovoid (480–530 µm wide in middle), and provided with numerous upturned spines (width including the spines 1000–1170 µm). The aperture occurs on the apex of a short neck region and is surrounded by a few, short spines. The female gonothecae ( Fig. 1 F–H) are comparatively larger (2985–3160 µm long), have a rhomboidal cross-section (940–1010 µm wide), forming four crests at each angle; each one is provided with a succession of moderately long, upturned spines (width of gonotheca including the spines ca 1300 µm). A central, piriform chamber is attached to the walls of the gonotheca through four perisarcal connections, whose position alternates with that of the crests. The aperture is situated apically, and is small and quadrangular.

Geographical distribution

Previously known from the Philippines ( Billard 1920, 1925b) and Japan ( Hirohito 1983, 1995). The present material originates from New Caledonia, Vanuatu, Fiji, and Tonga.

Figures

Fig. 1. ― A–B. Caminothujaria molukkana von Campenhausen, 1896 (BORDAU 2, Stn. CP1582). A. Fragment of internode with verticil of hydrothecae. B. Gonotheca. ― C–J. Diphasia cristata Billard, 1920 (BORDAU 1, Stn. CP1448). C. Pair of hydrothecae, frontal view. D. Same, dorsal view. E. Cross section through basal part of hydrothecal pair, showing perisarcal crests. F. Female gonotheca. G. Same, apical view. H. Same, cross section. I. Male gonotheca. J. Same, apical view. ― K. Diphasia orientalis Billard, 1920 (MUSORSTOM 3, Stn. DR117), internode with pair of hydrothecae. ― L–O. Dynamena heterodonta (Jarvis, 1922) (MUSORSTOM 9). L. Pair of hydrothecae in material from Stn. DW1204. M. Same sample, hydrothecal aperture, showing internal, submarginal cusps. N–O. Isolated (N) or stacked (O) pairs of hydrothecae in material from Stn. CP1265. ― P. Geminella ceramensis Billard, 1925a (MUSORSTOM 8, Stn. CP1084), internode with pair of hydrothecae. Scale bars: A–D, K–L, N–P = 500 µm; E = 400 µm; F–J = 1 mm; M = 100 µm.