Corhiza pauciarmata, Agís & Vervoort & Ramil, 2009
Agís, José Ansín, Vervoort, Willem & Ramil, Fran, 2009, Hydroids of the family Halopterididae (Cnidaria, Hydrozoa) collected in the western Pacific by various French expeditions, Zoosystema 31 (1), pp. 33-61: 56-58
treatment provided by
Corhiza pauciarmata n. sp.
( Fig. 11 View FIG ; Table 11)
TYPE MATERIAL. — Norfolk Ridge. SMIB 4, stn DW 55, 23°21.4’- 23°21.4’S, 168°04.5’- 168°04.8’E, 215-260 m, 9.III.1989, 1 colony with 3 damaged gonothecae, holotype ( MNHN Hy 1296).
SMIB 5, stn DW 101, 23°21.2’S, 168°04.9’E, 270 m, 14.IX.1989, 1 colony with 4 hydrocladia, no gonothecae, paratype (RMNH-Coel. 31459).
ETYMOLOGY. — The species name is derived from Latin: pauci: poor and armata: armed. It indicates that the species has only three nematothecae around the hydrotheca; in the majority of Corhiza species the number of nematothecae on hydrothecate internodes is higher.
DISTRIBUTION. — The material originates from two stations on the Norfolk Ridge and was collected between 215 and 270 m.
Colonies with a polysiphonic stem, unbranched, which hydrocladia arising at irregular distances on all sides of the stem.
Hydrocladia unbranched, inserted on well-developed apophyses. Basal part of hydrocladia with the first internode separated by transverse nodes and without nematothecae, followed by a long internode with two or three nematothecae and distal oblique node. Remainder of stem formed by a succession of hydrothecate and ahydrothecate internodes,alternately separated by oblique and straight nodes; hydrothecate internodes with basal oblique node and distal straight node; ahydrothecate internodes reverse.
Hydrothecate internodes with one hydrotheca and three nematothecae: one mesial inferior and two laterals. Hydrotheca cup-shaped; abcauline wall straight; adcauline wall adnate for nearly half its length; hydrothecal rim circular, smooth and slightly everted. Mesial inferior nematothecae not
SMIB 4 stn DW 55
Length ahydrothecate 450-700
Length hydrothecate 370-420
Diameter at node 60-90
Length abcauline wall 310-370
Length free portion adcauline wall 240-270
Diameter at rim 260-310
Mesial infracalycine nematotheca:
Diameter at rim 35-40
Diameter at rim 60-70
Nematotheca of ahydrothecate internode:
Diameter at rim 30-35
reaching hydrothecal base and with adcauline wall of upper chamber deeply scooped. Lateral nematothecae placed on well-developed apophyses, one on each side of hydrotheca, not reaching hydrothecal margin; upper chamber with the rim deeply scooped on both sides (spanner-like shape).
Ahydrothecate internodes with two frontal nematothecae, one placed in lower third, one in upper third; nematothecae with adcauline wall of upper chamber scooped.
All nematothecae bithalamic and movable.
The gonosome is damaged; a detailed description cannot be given. Gonothecae elongate, narrowing basally, inserted laterally at the hydrothecal base by means of a two-segmented pedicel. Apex truncate, with circular aperture closed by a lid; two nematothecae on basal third.
In several ahydrothecate internodes there was only one nematotheca on basal part of internode.
Schuchert (1997) in his review of the family Halopterididae agrees with the diagnosis of the genus Corhiza given by Millard (1975). Nevertheless he indicated that several species of Antennella and Halopteris can have a Corhiza -like mode of growth as an alternative colony form; therefore in his opinion the scope of the genus must be revised.
Our material shows the typical colony form of Corhiza , with an erect, unbranched, polysiphonic stem, giving rise to hydrocladia; in consequence we include it in this genus.
The genus Corhiza comprises nine species. The main distinguishing features of eight species, C. bellicosa Millard, 1962 , C. complexa (Nutting, 1905) , C. fascicularis ( Allman, 1883) , C. pannosa Millard, 1962 , C. scotiae (Ritchie, 1907) , C. sociabilis Millard, 1980 , C. suensoni ( Jäderholm, 1896) and C. valdiviae (Stechow, 1923) , were summarised by Schuchert (1997). The ninth species, C. splendens Vervoort& Watson, 2003 , was described later.
The presence of only one pair of lateral nematothecae and the absence of axillar nematothecae behind the adcauline wall of the hydrotheca distinguishes C. pauciarmata n. sp. from the majority of Corhiza species. Corhiza bellicosa has three pairs of lateral nemathotecae and C. pannosa , C. scotiae , C. sociabilis and C. splendens two pairs; C. complexa and C. valdiviae have only one pair but carry axillar nematothecae.
Corhiza fascicularis has not been recorded since its original description, the type material is lost and, in consequence, it is a poorly known species ( Schuchert 1997). This species differs from C. pauciarmata n. sp. because its stem is dichotomously branched, all nematothecae are conical and long, the lateral nematothecae surpassing the hydrothecal rim and the upper chamber is not scooped, there are three nematothecae on ahydrothecate internodes and the transverse node between hydrothecate and ahydrothecate internodes lies at the level of the hydrothecal rim.
Corhiza suensoni , according to the original description given by Jäderholm (1896), has hydrocladia composed only of hydrothecate internodes, there are two or three unpaired nematothecae per internode (one mesial inferior and one or two distal), the lateral nematothecae surpass the hydrothecal rim and the margin of the upper chamber is not scooped.Moreover, Schuchert (1997) indicates that C. suensoni is similar to C. complexa , but the former has no axillar nematotheca. In his opinion the type material of C. suensoni should be re-examined to confirm the absence of the axillar nematotheca.
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