Pseudochrysogorgia bellona, Pante & France, 2010

Pante, Eric & France, Scott C., 2010, Pseudochrysogorgia bellona n. gen., n. sp.: a new genus and species of chrysogorgiid octocoral (Coelenterata, Anthozoa) from the Coral Sea, Zoosystema 32 (4), pp. 595-612 : 601-605

Pseudochrysogorgia bellona n. gen., n. sp. ( Figs 1-6; Tables 1, 2)

HOLOTYPE. — W of New Caledonia. Bellona Plateau , EBISCO stn CP 2557 ( MNHN-IC.2008-006) . PARATYPES. — W of New Caledonia. Bellona Plateau, EBISCO stn CP 2557 ( MNHN-IC.2008-007).

N of New Zealand. Otara Seamount, stn TAN0413/41 ( NIWA 16273).

ETYMOLOGY. — The specific epithet refers to the type locality. Noun in apposition.

ADDITIONAL MATERIAL EXAMINED. — Only polyps were examined (see note in Material and methods section).

N of New Zealand. Otara Seamount, stn TAN0413/35 ( NIWA 15611). — stn TAN0413/41 ( NIWA 16272).

DISTRIBUTION. — Known from the type locality (Bellona Plateau, Coral Sea) and Otara Seamount, at southern tip of the Kermadec Ridge (N of New Zealand). The two localities are separated by approximately 2550 km.

DIAGNOSIS. — Same as that of the genus.

DESCRIPTION

Measurements and estimates of variation in character states are detailed in Table 2. Colonies are black and matte at the base, and are characterized by a dark metallic luster (holotype and paratype NIWA16273 black; paratype MNHN-IC.2008-007 dark brown). Branching sequence, as defined for Chrysogorgia (e.g., Versluys 1902; Cairns 2002, 2007) is 2/7R for the holotype, and irregular for the paratypes (see Discussion). Th e irregular branching pattern seen on the paratype is linked to the fact that the stem bifurcates and anastomoses. Th e distance between branches along the stem is regular, particularly on the holotype. Coenenchyme covers most of the upper part of the stem and branches and contains numerous sclerites. Th e stem is stiff, robust, and significantly thicker than the base of branches along most of the colony (proximal area: stem twice as thick as branches; distal area: stem and branches equally thick). Branches are stiff and stem from the main axis at nearly right angles. Order of branching is variable, mostly between four and six; the number of nodes per branch varies between 10 and 39. Branching occurs in multiple planes. The internodal distance and the angle between subdividing branches are regular. Axial polyps were not observed on the holotype or the paratype, and polyp occurrence starts on the second branch internode. Over half of the polyps lean to one side. Polyps appear to always be leaning in the direction of branch growth. They are on average as wide as they are tall and their size varies between 1.7 and 3.5 mm. Th ey are constricted at the neck, a character that seems to be exacerbated when polyps are left to dry. The arrangement of sclerites is detailed in the diagnosis of the genus. Sclerites do not appear tightly interlocked: while exposing polyps to bleach in an effort to remove the upper tissue layer covering the sclerites, these would fall off the polyp very rapidly (see Material and methods). All observed types of sclerites are warted; rods are more finely warted than scales. Scales have blunt extremities. Crosses (scales and rods with four rays in one plane) are rare but occur in the coenenchyme, body wall and tentacles. Most sclerites of the coenenchyme are scales and few are plates (for example, the fourth sclerite of Figure 6A is considered as a plate). While the proximal part of the polyp body wall (anthostele) is almost exclusively covered by scales, the distal part is richer in rods. Th e longest rods are found at the base of the tentacles, while smaller rods are found along the back of the tentacles.

REMARKS

The holotype and the paratype MNHN-IC.2008-007 were associated with hydroids, which were attached at the tips of a few branches. While the sister taxon M. melanotrichos is found in close association with Ophiocreas oedipus Lyman, 1879 ( Mosher & Watling 2009), no brittle stars were observed on the colonies examined (however, the symbionts might have been separated during or after sampling).

Specimens from the NIWA:NIWA15611, colony highly fragmented,main stem missing;NIWA16272, colony highly fragmented, only part of the main stem is available; NIWA16273, colony fragmented, main stem present. As NIWA16272 and NIWA16273 come from the same station (TAN0413/41), and that both lots contain branch fragments, it cannot be excluded that each lot may contain fragments from more than one colony.

Bifurcation pattern of secondary branches, polyp morphology, size and spacing of the NIWA specimens is consistent with that of the MNHN specimens. However, while axial polyps were not observed on the MNHN specimens, these appear to be present on NIWA16273. In addition, polyps can be observed on first internodes ( Fig. 4). While the stems of both the MNHN type specimens were broken at the base, NIWA16273 had an intact, root-like holdfast ( Fig. 4). Th is may indicate that the colony was collected from soft-sediments.

Polyp preparation: the speed at which sclerites fall from the polyp when exposed to bleach might depend on specimen fixation and preservation. Indeed, exposure to glutaraldehyde had the desired effect of locking sclerites into place, allowing for the digestion of the upper tissue layer. The same observation was made for M. melanotrichos . The described arrangement of sclerites (scales in body wall and rods in tentacles) corresponds to the “Squamosae aberrantes” (group B) as defined by Versluys (1902) for Chrysogorgia . Finally, polyps leaning distad have a swollen base, in which eggs can be found. Th is condition might be associated with the production of eggs.