Didemnum lithostrotum Brewin 1956
Creators: name: Page, M. J.
name: Willis, T. J.
name: Handley, S. J.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Ascidiacea
Aplousobranchia
Didemnidae
Didemnum
Didemnum lithostrotum

description: <i>Didemnum lithostrotum</i> Brewin, 1956 (Figure 11F) <i>Didemnum lithostrotum</i> Brewin, 1956a: p. 127 –129, figs 3A 1, A 2, A 3. <i>Didemnum lithostrotum</i>: Millar 1982: 49, 51. <i>Material examined</i> <i>New record</i>: Caswell Sound, Paua Bay (45° 01.01’S, 167° 08.40’E, 20 m, 3 February 2009, NIWA 49980, one colony). <i>Previously recorded</i>: New Zealand: Chatham Islands (Brewin 1956a); Chatham Rise (Brewin 1956a); Stewart Island (Brewin 1958a). <i>Description</i> The pink/orange (YR 7/6) colony from Caswell Sound is 1 mm thick, encrusting on the brachiopod <i>Liothyrella neozealandica</i>. The test is divided into irregular polygonal areas, each with a central common cloacal aperture (Figure 11F). Spicules occur throughout the colony, although more are concentrated in a layer near the surface and at the substratum. They have eight rounded rays in optical cross-section and measure 40–70 µm in diameter. The zooids are 1 mm long in fixed material, the branchial aperture is relatively tall with six low pointed lobes, and the atrial aperture is smooth rimmed with a short simple lappet. The stomach is small and globular. There are two testis follicles with six to seven coils of the vas deferens. <i>Remarks</i> Possible synonymy of this species to <i>Didemnum densum</i> (Nott 1892) was mentioned by Millar (1982). We have placed the Fiordland colony in the species <i>Didemnum lithostrotum</i> based on the southern distribution of the holotype, and different morphology of the tunic (not in polygonal pattern in <i>D. densum</i>) and the branchial aperture lobes. The zooids in the current species are smaller than given by Brewin (1956a), but this is because they were contracted on collection and preservation. <i>Didemnum densum</i> in relaxed colonies has a branchial siphon with needle-like lobes whereas <i>D. lithostrotum</i> does not. An <i>in-situ</i> photograph by Stocker (1985) identified as <i>D. densum</i> shows polygonal pattern in the tunic; it could be a misidentification because this is an important character.
description: Published as part of <i>Page, M. J., Willis, T. J. &amp; Handley, S. J., 2014, The colonial ascidian fauna of Fiordland, New Zealand, with a description of two new species, pp. 1653-1688 in Journal of Natural History (J. Nat. Hist.) (J. Nat. Hist.) 48 (27 - 28)</i> on page 1680, DOI: 10.1080/00222933.2014.896487, http://zenodo.org/record/5193878
description: {"references": ["Brewin, BI. 1956 a. Ascidians from the Chatham Islands and the Chatham Rise. Trans Proc Royal Soc New Zealand. 84: 121 - 137.", "Millar, RH. 1982. The marine fauna of New Zealand: Ascidiacea. New Zealand Oceanogr Mem. 85: 114 pp.", "Brewin, BI. 1958 a. Ascidians of New Zealand. Part XI. Ascidians of the Stewart Island region. Trans Royal Soc NZ. 85: 439 - 453.", "Nott, JT. 1892. On the composite ascidians of the North Shore reef. Trans Proc New Zealand Inst. 24: 305 - 334.", "Stocker, LJ. 1985. An identification guide to some common New Zealand ascidians. University of Auckland Leigh Marine Laboratory, Auckland, New Zealand. 74 p."]}