Arthuria tubuloreticulosa Soest & Voogd, 2015, sp. nov.
Creators: name: Van Soest, Rob W. M.
name: De Voogd, Nicole J.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Calcarea
Clathrinida
Clathrinidae
Arthuria
Arthuria tubuloreticulosa

description: Arthuria tubuloreticulosa sp. nov.
Figures 11a–c, 12a–b
Material examined. Holotype RMNH Por. 5547, Indonesia, Halmaheira, Ternate, Sulamadaha Bay, 0.8661°N 127.3316°E, depth 5–15 m, SCUBA, coll. N.J. de Voogd, #TER.05/261009/1, Ternate-Halmahera Expedition, 26 October 2009.
Description. An orange flattened mass of short oscular tubes (Fig. 11a), connected at the substratum by a basal tubular network, growing on an encrusting octocoral (Briareum). The erect tubes maybe divided into one or two side tubes. The preserved specimen (Fig. 11b) is fragmented, but there are several larger pieces that show the short erect tubes forming the main basis of the specimen. Overall size estimated to be 5 x 3 cm, with small tubes about 2– 4 mm in diameter. Color beige in preserved condition.
Skeleton. (Fig. 11c) The walls of the tubes are thin, approximately 15 µm in thickness. The spicules are dominated by triactines. The choanoderm lines all internal surfaces.
Spicules. (Figs 12a–b) Triactines, tetractines.
Triactines (Fig. 12a), equiangular, predominantly equiactinal, but a fair number are slightly parasagittal, with the longer actines often slightly wobbled; most actines are cylindrical with abruptly pointed ends, but small triactines may have their actines conical, size of actines 63– 112.1 –138 x 4– 5.3 –6.5 µm.
Tetractines (Fig. 12b), similar to triactines in size and shape, actines of basal triadiate system, 62– 119.5 –156 x 4– 5.4 –6 µm; apical actines 39–132 x 3.5–6.5 µm.
Ecology. Shallow-water reef.
Distribution. Known only from the type locality, Ternate.
Etymology. The name reflects the combination of a network of tubes on the substratum and erect tubes protruding from it.
Remarks. The dominance of triactines over tetractines, and the normal-shaped apical actines of the tetractines makes this Clathrina -like species a likely member of the recently erected genus Arthuria. The genus has a few Indo-Pacific species, but none of them seem to be close to our new species: South Australian A. dubia (Dendy, 1891) (as Leucosolenia) has much thicker actines (averaging 15–16 µm) and the tetractines are very rare (they were not mentioned by Dendy, but subsequently reported by Klautau & Valentine, 2003: 26). Red Sea A. sueziana Klautau & Valentine, 2003 has a different habitus and also much thicker actines. The above-described A. tenuipilosa possesses diactines.
Haeckel’s (1872) description and figures of Ascaltis darwinii reminds rather strongly of the present species and at first we assumed that it could be conspecific. However, shapes and sizes of the tri- and tetractines presented by Haeckel consistently differ: actines are equiangular equiactinal, shorter (80–100 µm) but more robust and conical (10–12 µm thick) than those of our new species. Clathrina darwinii should be transferred to Arthuria (see below).
Genus Ernstia Klautau, Azevedo, Cóndor-Luján, Rapp, Collins & Russo, 2013
Clathrinidae with asconoid aquiferous system possessing both triactines and tetractines in approximately equal proportions or tetractines more frequently. The apical actine of the tetractines is long and thin (after Klautau et al. 2013).
description: Published as part of Van Soest, Rob W. M. & De Voogd, Nicole J., 2015, Calcareous sponges of Indonesia, pp. 1-105 in Zootaxa 3951 (1) on pages 20-21, DOI: 10.11646/zootaxa.3951.1.1, http://zenodo.org/record/14950882