Caledoniana decussata, 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 : 4-6

Caledoniana decussata sp. nov.

urn:lsid:zoobank.org:act:B302DBC1-9E6F-427F-A3B6-3843F8FAE77C

Figs 1B , 2 C–D; Table 1

Diagnosis

Colonies lightly fascicled basally, loosely branched, coplanar; nodes indistinct, internodes relatively short; hydrothecae in opposite pairs in both coplanar and decussate series; long, tubular, free part straight.

Etymology

From the Latin dĕcusso, meaning "to form or create a cross in the form of an X", to characterize the arrangement of the hydrothecal pairs in this species.

Material examined

Holotype

NEW CALEDONIA: campaign Bathus 2, station CP737, 23°03’ S, 167°00’ E, 357–400 m, 13 May 1993; 5.5 cm high, sterile colony attached to mineral concretion and adjacent sponge, as well as 3 smaller fragments detached from it (IK-2012-10289).

Description

Colony erect, 5.5 cm high, arising from rhizoid stolon firmly attached to substrate. Basal part of stem fascicled, with several accessory tubes creeping over main tube; in monosiphonic parts, division into internodes indistinct; each equivalent of internode relatively short, bearing a pair of opposite, though not contiguous, hydrothecae. Branching sparse and irregular, up to 2 nd order; side branches given off singly or in pairs from below a stem hydrotheca; stem and side branches coplanar; structure of latter similar to that of stem, except for first hydrotheca, which is usually unpaired, though a pair of hydrothecae also occurs within colony. Basal parts of stem and side branches with successive pairs of hydrothecae in coplanar series; more distally, pairs become decussate. Hydrothecae large, tubular, adnate for about half of length, or less, to corresponding internodes; free part bent at about 45°; diameter nearly constant throughout, slightly expanding at rim; rim conspicuously thickened; aperture circular in frontal view; opercula not seen. Gonothecae absent, though basal remains at insertion of one of these (below a hydrotheca) present; numerous, large foramina (obliterated by thin pellicle of perisarc) below most hydrothecae, making the possibly future insertion points for them. Coenosarc badly preserved, not suitable for tentacle counting or cnidome studies.

Figures

Fig. 1. A. Caledoniana alata gen. et sp. nov., holotype (below) and paratype (above). B. Caledoniana decussata gen. et sp. nov., colony silhouette (part of holotype). C. Caledoniana microgona gen. et sp. nov., colony silhouette (holotype). The red arrows indicate the presence of gonothecae. Scale bars: 1 cm.

Fig. 2. — A–B. Caledoniana alata gen. et sp. nov. A. Portion of fertile stem (note gonotheca above) and basal part of a side branch, showing positions of hydrothecae. B. Hydrotheca. — C–D. Caledoniana decussata gen. et sp. nov. C. Portion of stem with first and second order side branches from region of colony with coplanar hydrothecae, showing their relative position. D. Hydrotheca. — E–G. Caledoniana microgona gen. et sp. nov. E. Portion of stem. F. Hydrotheca. G. Three gonothecae. Scale bars: A, C, E, G = 3 mm; B, D, F = 1 mm.