Oncosclera diahoti (Rützlerı 1968)

Pronzato, Roberto & Manconi, Renata, 2019, An overview on the freshwater sponge fauna (Demospongiae: Spongillida) of New Zealand and New Caledonia with new insights into Heterorotula from deep thermal vents of the Lake Taupo, Journal of Natural History 53 (35), pp. 2207-2229 : 2207-2229

Oncosclera diahoti (Rützlerı 1968)

( Figures 1 (B)ı 2)

Spongilla (Stratospongilla) diahoti Rützlerı 1968 ; Oncosclera diahoti Volkmer-Ribeiro and Rützlerı 1997 ; Manconi and Pronzatoı 2002; Manconi et al. ı 2012; Copeland et al. ı 2015; van Soest et al. ı 2018 Comparative materials

IRScNBı 24 Por Dı I.G.9243ı FW-POR 361 ı Oncosclera gilsoni from Fiji. MNRJ-001ı typeı O. jewelli ı type species of the genus Oncosclera . USNM 23881 ı holotypeı Spongilla (Stratospongilla) diahoti not examined (5 fragments) .

Description (emended after Rützler 1968)

Growth form encrusting (1 mm thick) as tiny porous patches 1 cm 2. Colour dark grey (alcohol). Consistency very softı compressible. Spongin scanty. Skeleton as an irregular meshwork of spicules. No fibres and tracts. Megascleres smooth oxeas (210 – 280 × 9 – 14 µm)ı slightly bentı tapering gradually to sharply point tips. Microscleres absent. Gemmules sessile at the basal spongin plateı spherical (350 – 500 µm) to egg – shaped (520 – 600 µm) with simple foramen (40 – 50 µm); pneumatic layer absent; gemmuloscleres tangentially and loosely arranged at the gemmular theca surface; gemmuloscleres as smooth oxeas usually centrotylote (100 – 250 × 2 – 8 µm) more or less strongly bentı sometimes aberrant i.e. stylelike with swelling 6 – 11 µm in diameter.

Habitat

This species was discovered associated to Pachyrotula raceki on the lower surfaces of stones (0.05 – 0.20 m depthı water temperature 20.30 °Cı 250 m asl)ı in water flowing through a deep valley partly covered with rain forest (modified after Rützler 1968).

Geographic range

Oncosclera diahoti is a New Caledonian endemic known only in the middle course of the River Diahot (type locality) near Quénia (Chapel St. Josephı North New Caledoniaı 16. IX. 1965ı coll. Dr. Ferdinand Starmuhlnerı Zoologisches Institut der Universität Wien).

Remarks

Oncosclera diahoti was originally described with few details as Spongilla (Stratospongilla) diahoti (family Spongillidae ) by Rützler (1968). It was transferred to the genus Oncosclera described by Volkmer-Ribeiro (1970) in the family Potamolepidae by Volkmer-Ribeiro and Rützler (1997). The comparison vs the only known species of the genus Oncosclera in South – Eastern Pacific i.e. O. gilsoni (Topsentı 1912) from the Fiji Archipelago indicates that O. diahoti is quite atypical ( Figure 2 ; see diagnosis in Manconi and Pronzato 2002 and its emendation in Manconi et al. 2012). Integrative taxonomy with also molecular analyses is necessary.

Figures

Figure 1. (A) Study area of Spongillida (Porifera, Demospongiae) in insular freshwater of Australasia. (B) New Caledonia Island harbours three endemic species viz. Heterorotula caledonensisı Oncosclera diahoti, and Pachyrotula raceki (genus Pachyrotula is also endemic). Heterorotula multidentata is shared by New Caledonia and Eastern Australia. (C) Geographic range of Heterorotula kakahuensis endemic to New Zealand.

Figure 2. Oncosclera diahoti (modified after Rützler 1968) endemic to New Caledonia. (A) grouped gemmules. (B1a and B2a) centrotylote oxeas as gemmuloscleres. (B2b), smooth oxea as megasclere (detail).