Amphoriscus ancora, Van, Rob W. M., 2017

Van, Rob W. M., 2017, Sponges of the Guyana Shelf, Zootaxa 1, pp. 1-225 : 201-204

Amphoriscus ancora sp. nov.

Figures 128 a–d, 129a–e

Material examined. Holotype RMNH Por. 9741, Suriname, ‘Luymes’ Guyana Shelf Expedition, station 43, 6.5167°N 53.9333°W, depth 35 m, Agassiz trawl, bottom shell gravel, 28 August 1970 .

Description. ( Fig. 128 a) Thin flattened oval tube, length 18 mm high, 4 mm in greatest diameter. Oscule naked, with two short root-like holdfasts. Color (in alcohol) dirty white to pale beige.

Skeleton. ( Figs 128 b–d) Inarticulate, with choanosomal skeleton made up of the apical actines of the cortical tetractines and the unpaired actines of subatrial triactines. No scattered spicules in the choanosome. In cross section ( Fig. 128 b) from ectosome to atrium, there are successively the cortical skeleton ( Fig. 128 c) consisting of the paired and unpaired actines of large tetractines, choanosomal skeleton ( Fig. 128 d) consisting of the apical actines of the cortical tetractines and the unpaired actines of the subatrial triactines, paired actines of the subatrial triactines, and the atrial skeleton consisting of small atrial tetractines, with their apical actines protruding in the atrial cavity. The root skeleton consists of a bundled mixture of thin diactines and peculiar curved anchoring triactines.

Spicules. ( Figs 129 a–e) Tetractines, triactines, anchoring triactines, diactines.

Tetractines divisible in (1) larger cortical tetractines ( Figs 129 a), with apical actines as long or longer than the basal actines, sizes: unpaired actines, 151– 216 –330 x 12 – 16.1 –21 µm, paired actines 135– 239 –320 x 8 – 15.4 –21 µm, apical actines 258– 311 –366 x 8 – 17.8 –20 µm, and (2) smaller atrial tetractines ( Figs 129 b) tending to be sagittal, with shorter apical actines, sizes: unpaired actines 42– 87 –186 x 3 – 8.6 –12 µm, paired actines 57– 99 –165 x 3 – 7.7 –11 µm, apical actines 9– 26 – 60 x 3 –5.3–15 µm.

Subatrial triactines ( Figs 129 c), in a large size range but less diverse and not readily divisible in categories, paired actines may be slightly wavy, unpaired actines 201– 367 –468 x 7 – 10.1 –12 µm, paired actines 129– 218 –324 x 7 – 8.6 –10.5 µm.

Anchoring triactines ( Figs 129 d,d1) from the roots, with characteristically curved unpaired actine and beaklike paired actines, in a large size range, unpaired actines 96– 386 –660 x 7 – 8.6 –10 µm, paired actines 18– 24.8 – 29 x 5 –6.8–9 µm.

Diactines ( Figs 129 e,e1) from the roots, long and thin, 600–1 0 17 – 1230 x 3 – 4.2 –6.5 µm.

Distribution and ecology. Guyana Shelf, gravel bottom at 35 m depth.

Etymology. Ancora (Gr., latinized, a female noun) meaning anchor, referring to the shape and function of the beak-like root spicules.

Remarks. The new species shares its anchoring spicules with those of the Brazilian species Syculmis synapta Haeckel, 1872 , assigned to Amphoriscus by Borojevic et al. 2002b (p. 1178). This species is close to the new species, both geographically and morphologically. It differs by having the anchoring spicules all consisting of tetractines (the beak-like part of the spicule has three actines instead of two as in the new species), by the apparent entire lack of triactines (their subatrial position is taken up by tetractines in A. syculmis ), and by the possession of a prominent apical fringe of long thin diactines. Despite the morphological similarity these differences merit recognition at the species level.

Further close, but more dissimilar, species are Caribbean A. amphora ( Haeckel, 1872) (as Leucilla ) and Venezuelan A. urna Haeckel, 1872 . The shape of A. amphora is similar to that of the new species, but there is no report of anchoring root spicules, and like A. synapta the subatrial spicules are tetractines, not triactines, nor are there any other triactines. The shape of A. urna is more globular, but in other aspects of skeleton and spiculation it is similar to A. amphora .

Other Amphoriscus species of the region are: Floridian A. oviparus ( Haeckel, 1872) (as Sycaltis ovipara ) has small cortical triactines overlying the subcortical tetractines, lacking subatrial triactines (but having subatrial tetractines) and lacking root spicules. Cuban A. testiparus ( Haeckel, 1872) (as Sycaltis testipara ) is similar to A. oviparus (so possesses cortical triactines and subatrial tetractines) but forms groups of tubes.

Figures

FIGURE 128. Amphoriscus ancora sp. nov., a, habitus of holotype RMNH Por. 9741 (scale bar = 1 cm), b – d, SEM images of cross sections of the skeleton, b, overview of skeleton, c, cortical skeleton, d, inarticulate choanosomal skeleton.

FIGURE 129. Amphoriscus ancora sp. nov., a – e, SEM images of the spicules of holotype RMNH Por. 9741, a, large cortical tetractines, b, small atrial tetractines, c, triactines, d, anchoring triactines, d 1, detail of d, e, root diactine, e 1, details of e.