Corhiza patula

Description Colony upright, ca 5 cm high, arising from dense, root-like hydrorhiza, composed of numerous branching, anastomosing tubes that converge, then loosely aggregate above substrate to form ca 3 cm high, fascicled stem; all tubes have equivalent roles; division into internodes absent; perisarc thick, smooth to slightly wrinkled. Some of component tubes of stem modified distally to become cladia; these detach from stem at acute angle, pointing upwards, in all directions around it. Cladia up to 2 cm long, composed of free, ahydrothecate proximal part with smooth perisarc, occasionally with either signs of breakage followed by subsequent regeneration, or divided by transverse nodes into succession of internodes of varied length, distally bearing row of nematothecae; last internode with oblique node distally; remainder of cladium heteromerously segmented into hydrothecate and ahydrothecate internodes by means of alternating transverse and oblique nodes; most often, transverse node only slightly indicated, especially dorsally; oblique nodes generally well-marked, though here and there they may be totally absent. Hydrothecate internodes short, with proximally oblique and distally transverse nodes, a hydrotheca and its three associated nematothecae: one mesial and pair of laterals; hydrotheca thin-walled, deep, tubular, half adnate, flaring distinctly at aperture; mesial nematotheca not reaching hydrothecal base, upper chamber with rim lowered on adaxial side; lateral nematothecae borne on short apophyses, whole structure far from reaching hydrothecal margin; upper chamber globular, with rim distinctly scooped on adaxial side. Ahydrothecate internodes with proximal node transverse and distal node oblique, of nearly same length as their hydrothecate counterparts; proximally frontal, conical nematotheca with rim of upper chamber lowered on adaxial side. Gonothecae absent.

urn: lsid: zoobank. org: act: FDCDC 082 - 2435 - 4268 - 8808 - C 5 B 7 D 74 D 7 BEB Figs 11 C, 14 A – D; Table 6

Diagnosis Stem composed of many loosely-aggregated tubes arising from root-like hydrorhiza; individual cladia arising distally, in all directions, from some of the component tubes; proximal parts of cladia with a row of frontal, bithalamic nematothecae; distal node oblique, followed by a regular succession of alternating hydrothecate and ahydrothecate internodes delimited by a heteromerous segmentation; ahydrothecate internodes short, with a frontal nematotheca proximally; hydrothecate internodes equally short, with a very deep, cylindrical hydrotheca with strongly flared margin, and its 3 associated nematothecae: one mesial, and a pair of lateral; mesial nematotheca with wall of upper chamber lowered adaxially; lateral nematothecae borne on short apophyses, upper chamber globular, with deeply emarginated wall on adaxial side. Gonothecae unknown.

Remarks Corhiza patula Galea sp. nov. is unique among its congeners through the distinctive shape and size of its hydrothecae. Only the hydrothecae of C. megatheca, if this species proves congeneric, approach their morphology, but they are slightly smaller and not distinctly flared at rim. Unlike in the new species, it has been shown above that the cladia of C. megatheca are given off exclusively from a single tube of the fascicled stem. The third species occurring in the study area, C. pauciarmata Ansín Agís et al., 2009 (see below), has comparatively shorter hydrothecae (compare Fig. 14 A and 14 E). Other congeners are immediately distinguished from C. patula Galea sp. nov. through the following features: 1) the hydrothecae of C. bellicosa Millard, 1962 are adnate for most of their length (Millard 1962); 2) two pairs of lateral nematothecae occur in C. pannosa Millard, 1962 (original account), C. scotiae (Ritchie, 1907) (Vervoort & Watson 2003), C. sociabilis Millard, 1980 (original account) and C. splendens Vervoort & Watson, 2003 (original account); 3) an axillar nematotheca is found behind the hydrothecae of C. complexa (Nutting, 1905) (Schuchert 1997).

Distribution Known only from off New Caledonia (present study).

Etymology From Latin ‘ pātŭlus, - a, - um ’, meaning ‘ provided with a wide aperture’, to illustrate the shape of its hydrothecae.

Material examined Holotype PACIFIC OCEAN • 1 sterile colony, ca 5 cm high; off New Caledonia, stn DW 4746; 22 ° 59 ′ S, 167 ° 43 ′ E; 508 – 494 m; 23 Aug. 2016; KANACONO leg.; MNHN-IK- 2015 - 602.