MAINBAZA

During the CALSUB cruise, bathyal environments were explored off the New Caledonia corallian platfdrms (southwestern Pacific). Green algae were observed down to a depth of 1 IO m, and red algae down to 145 m. Algal blocks, pebbles and sands contribute to sedimentation to a depth of 400 m and beyond, and are mixed with autochthonous fossils and bioclasts produced by bathyal benthos. Epibathyal fauna suggests similarities with Jurassic and Cretaceous fauna of Tethyan margins (Nautilus, pleurotomarian gastropods, sponges, brachiopods and crinoids…). Richness and abundance of the benthos are the highest in areas where currents are frequent between 300 m and 700 m (sometimes 10 to 20 terebratulid brachiopods per m2 or dense populations of echinoderms entirely covering the substrate). Such currents induce erosion of' substrate or bioclastic accumulations. Biocorrosion seems to be very active in erosion processes, especially on hard grounds. Burrows and traces show the importance of sediment bioturbation on slopes. The occurrence on bathyal slope of some taphonomic processes previously known from geological series and generally considered as closely related lo shallow-water environments should be emphasized.

CALSUB

L'exploration de la faune profonde de NouvelleCalédonie a débuté par des campagnes d'essai de 1977 à 1979 sur des fonds de 200 m à 1000 m au large de la Grande Terre, de l'île des Pins et des îles Loyauté (Intès, 1978). A partir de 1985, elle s'est élargie et intensifiée avec les campagnes MUSORSTOM 4 à 6 et CHALCAL (Richer de Forges, 1990), BIOCAL, BIOGEOCAL et SMIB, complétées par des observations directes à l'aide de la soucoupe plongeante Cyana lors de la campagne CALSUB. Nous ne donnerons ici que les grands traits de l'étagement de la macrofaune et de la mégafaune benthique en insistant sur les observations directes insitu lors de la campagne CALSUB et sur la liaison avec les caractères du milieu.

CALSUB

A "living fossil" of the group Sphinctozoa has been discovered in the Indian Ocean and in New Caledonia in a very cryptic habitat of the outer slope of coral reefs. The living tissue is inside a series of hemispherical chambers. The perforated chamber walls are composed of aragonite and consist of a feltwork of microfibrills. In the growing sponge, the skeleton of a new chamber appears first as an organic matrix, which is the template for a later calcification. There are no spicules. The histology, cytology and sexual reproduction are compared to those of the recent Porifera. They are similar ·to those of the Ceractinomorpha in the class Demospongea. This study shows that most fossil Sphinctozoa were relatives of Demosponges. They are cons idered by the author as an order of the class Demospongea. These sponges were devoid of spicules. Thus, the exclusion from the Porifera of some fossil groups as Stromatopores or some Tabulates on the ground of the absence of spicules is not valid. A new order Sphaerocoelida is proposed for cretaceous sponges which have the same structure, but which have calcareous spicules and probably are homeomorphs of the class Calcarea. A comparison is made between the 14 recent sponges which possess a nonspicular calcareous skeleton. The large diversity of both the skeleton and the living tissue of these sponges indicates that their hypercalcification is an archaic character, which was frequent in the past and which disappeared in most of the recent sponges.

BENTHEDI

Sphinctozoan sponges were major reef-builders in the Permo-Triassic. For a long time, they were considered to be extinct, until a discrete, solitary "living fossil" was found in cryptic reef habitats. A new extant sphinctozoan, with the same colonial morphology and construction capabilities as its fossil counterparts, has been discovered in bathyal environments off from New Caledonia. A significant difference from modern scleractinian reff-builders is the particularly low growth rate: the basal part of a 10 cm thick contruction is approximately 700 years old.

CALSUB

Discorhabdella pseudaster n. sp. is an incrusting sponge from the upper bathyal zone of the ‘Banc du Geyser’, north of Madagascar, Mozambique Channel. This new species is described only from a single specimen but it is remarkable by the presence of spicules similar to euasters, a type of microsclere unknown in Poecilosclerida. These spicules are in fact a new example of homoplasy, being derivatives of the typical Discorhabdella pseudoastrose acanthostyles, which are here reduced to the aster-like tyles. The isochelae with a large lamella on the shaft are also quite unique in Poeciloclerida.

BIOMAGLO

Three new species of carnivorous sponges of the genus Abyssocladia (Demospongiae, Cladorhizidae), A. kanaconi, A. microstrongylata and A. mucronata, are described from the bathyal zone of the Tropical Southwestern Pacific, south of New Caledonia. They were collected in 2016 and 2019 during the KANACONO and KANADEEP 2 expeditions of the Tropical Deep-Sea Benthos program of the French Museum National d’Histoire Naturelle. A new record is reported for the cladorhizid Cercicladia australis Rios, Kelly & Vacelet, 2011, and the spicules of the holotype of the type species of Abyssocladia, A. bruuni Lévi, 1964 are illustrated.

KANACONO, KANADEEP 2

BIOCAL, KANACONO, KANADEEP 2