Heterorotula caledonensis (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

Heterorotula caledonensis (Rützlerı 1968)

( Figures 1 (B)ı 4(A))

Ephydatia multidentata f. caledonensis Rützlerı 1968 (figs. 13 – 19ı p. 64); Heterorotula caledonensis Volkmer-Ribeiro and Rützlerı 1997 ; van Soest et al. ı 2018

Comparative materials

BMNH 1890.1.9.339ı holotypeı Heterorotula capewelli type species of the genus Heterorotula . WAM Z27997 ı FW-POR 881 ı Heterorotula multiformis . WAM Z98316ı FW- POR 883 ı Heterorotula cf . multidentata. USNM 23884 type material of Heterorotula caledonensis (3 specimens) not examined here .

Description (emended after Rützler 1968)

Growth form small irregular cushions (~ 1 cm 2) on dead plant stems or thin (2 mm) crusts (2 cm 2) on dead leaves. Consistency soft compressible. Scanty spongin. Colour in alcohol whitish in the macerated peripheral partsı greyish brown centrallyı where abundant gemmules accumulate in several layers. Oscula and inhalant apertures not detected. Skeleton as polygonal meshwork of primary spicuları ascendingı tracts sometimes branching to the surface (200 – 600 µm apart); secondary tracts from 2 – 3 oxeas horizontally placed to single spicules in the interior of the sponge. Megascleres entirely spiny (100 – 150 × 8 – 19 µm). Gemmuloscleres spiny oxeas and birotules (30 – 100 × 5 µm) with very irregular rotules (15 µm in diameter). Gemmules sphericalı brownish (450 – 600 µm in diameter) with gemmuloscleres arranged in a single layerı and single foraminal tube (40 µm).

Habitat

Sponges have been discovered in a well-shaded pond (0.5 m depth; water temperature 18.60 °C) along a stream bed growing on decaying woodı dead leaves and plant stems (Eichorniaı Lemnaı Characea and Potamogetonacea).

Geographic range

Heterorotula caledonensis is endemic to New Caledonia and exclusively known from the type locality an unnamed pond along a stream flowing towards La Foa ( Figure 1 (B)ı South Western New Caledoniaı 25.VII. 1965ı coll. Dr. Ferdinand Starmuhlner from the Zoologisches Institut der Universität Wien).

Remarks

Heterorotula caledonensis was originally described as H. multidentata f. caledonensis by Rützler (1968) ı with few details. It was subsequently ranked to the species level and redescribed by Volkmer-Ribeiro and Rützler (1997 ı p. 495) with exhaustive illustrations of diagnostic morphotraits distinguishing the species: ‘ The great variations in the gemmoscleres of H. caledonensis could not be found in specimens of H. multidentata from either eastern Australia or New Caledonia and are now considered to be of such magnitude that they denote a new species ’. The present comparative analysis of morphology vs previous descriptions and illustrations of the two latter species shows that the shaft length range is almost identical (~ 30 – 80 µm)ı and both species also bear similar malformed gemmuloscleres. Consequentlyı it is very difficult to distinguish between the two species from the morphological point of view. 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.