Pachyrotula raceki (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

Pachyrotula raceki (Rützlerı 1968)

( Figures 1 (B)ı 3 (F – G)ı 4 (C))

Spongilla (Stratospongilla) raceki Rützlerı 1968 (figs. 5 – 9; p. 61); Pachyrotula raceki Volkmer- Ribeiro and Rützlerı 1997; Manconi and Pronzatoı 2002; van Soest et al. ı 2018

Comparative materials

USNM 23882ı holotypeı USNM 23883ı paratypeı several fragmentsı Pachyrotula raceki (as Spongilla raceki ).

Description (emended after Rützler 1968)

Growth form encrustingı thin (1 mm thick)ı small (1 cm 2) on the lower surface of stones. No oscula or inhalant apertures evident. Colour greyish-ochre (alcohol). Consistency soft. Spongin scanty. Skeleton is a dense polygonal meshwork of primary spicuları ascendingı paucispicular tracts (2 – 5 spicules) 100 – 200 µm apart. Megascleres as microspiny oxeas (160 – 245 × 7.5 – 10.5 µm). Microscleres absent. Gemmules (250 – 650 µm in diameter) loosely scattered in the basal sponge portion. Gemmulosclere as birotules radially and irregularly arrangedı spiny shaft and distinguishing globular rotules irregularly spiny (20 – 60 µm in lengthı shaft 5.5 – 6.5 µm in diameter; knobs 11 – 16 µm in diameter).

Habitat

Tiny specimens of Pachyrotula raceki have been discovered in the Lac en Huit (Plaines des Lacsı 19.VII. 1965ı coll. Dr. Ferdinand Starmuhlnerı Zoologisches Institut der Universität Wien) on boulders (5 – 30 cm depthı water temperature 21.50 °C). The pond also harbours the protected species of fish Galaxias neocaledonicus Weber & Beaufortı 1913 . In the middle course of the River Diahotı sponges have been found associated to Oncosclera diahoti (see above for environmental data). In the lower course of the River Diahot small flat sponges have been found on the lower surfaces of stones (water temperature 24.6°C) ~ 10 km upstream from the sea coastı an area still under the influence of the tidal backwater.

Geographic range

Pachyrotula raceki is a New Caledonian endemics known only from three localities in two hydrographic basinsı i.e. middle course of the River Diahot (near Quéniaı Chapel St. Josephı North New Caledoniaı 16.IX.1965); lower course of the River Diahot (next to the Bondé Mission houseı North New Caledoniaı 18.IX.1965); Lac en Huitı (Plaines des Lacsı South New Caledoniaı 19.VII.1965).

Remarks

Pachyrotula raceki (Holotype USNM 2.3882) endemic to New Caledonia was firstly described as Spongilla (Stratospongilla) raceki by Rützler (1968) and later transferred to the new monospecific genus Pachyrotula by Volkmer-Ribeiro and Rützler (1997). The most evident diagnostic trait of the genus is the unique gemmulosclere morph consisting of birotules ending in evident globular and irregularly spiny rotules ( Figure 3 (F – G)). 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 3. Gemmuloscleres with divergent diagnostic morphotraits. Comparison of type specimens of the type species of the genera Ephydatia (A–B, E. fluviatilis), Heterorotula (C–E, H. capewelli), Pachyrotula (F–G, P. raceki) and Oncosclera (H–J, O. jewelli).