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The Bathyal Holothurians of the New Zealand Region

Echinocucumis Sars, 1859

Echinocucumis Sars, 1859

Diagnosis: Tentacles 10, unequal in size. Body spherical; mouth and anus placed at ends of non-retractile tubes. Pedicels scarce, slender, threadlike, restricted to ambulacra. Body covered by very large scales (diameter greater than 1mm), perforated by numerous regular holes. Scales single-layered, never built up into several layers of reticulated network. Most scales with a single long spire placed near margin. (Partly after Deichmann, 1930.)

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Type Species: Echinocucumis hispida (Barrett).

Remarks: This genus, as well as Ypsilothuria, is remarkable in possessing large overlapping spired scales in the bodywall, which give the body rigidity, and a characteristic shape.

Two species, the type and E. paratypica Heding, are known. The latter was described from material collected off East Africa in a depth of 1,289 metres.

Echinocucumis hispida (Barrett) (Text-fig. 1, fig. 1; Text-fig. 2)

Eupyrgus hispidus Barrett, 1856, 46, Pl. 4, figs. 1 a-b.

Echinocucumis typica Sars, 1861, p. 102, Pl. 10, figs. 11–20, Pl. 11, figs. 1–17; Pourtales, 1869, p. 359; Theel, 1886a, p. 118; Theel, 1886b, p. 9, fig. 3; Herouard, 1923, p. 118.

Cucumaria typica Ludwig, 1901, p. 149.

Echinocucumis hispida: Mortensen, 1927, p. 404, figs. 242 (1), 243; Deichmann, 1930, p. 150; Ludwig and Heding, 1935, p. 167; Heding, 1942, p. 29, figs. 31, 32; Panning, 1949, p. 454.

Material Examined: N.Z.O.I. Stn. G.603, 2 specimens.

Description: Both specimens U-shaped (Text-fig. 1, fig. 1), total length (measured about greater curvature of body) 50mm in one specimen, 40mm in the other. Oral extremity in both specimens 2.5mm in diameter. Bodywall hard and brittle but thin, with numerous elongate spinous projections. Tubefeet present in small numbers confined to radii, more common ventrally, difficult to distinguish from spinous projections. Colour in alcohol greyish-white, darker at extremities. Tentacles fingerlike, conical.

Calcareous ring fragile, each piece with a shallow posterior notch. Intestine long, light yellow, coiled at the middle (Text-fig. 2, fig. 1); rectum transparent, large, supported in "tail" by fine muscle fibres. Respiratory trees three, of which one extends to anterior end of body cavity. Remaining two trunks short, about half length of body cavity. Respiratory caeca simple sacs, sparsely scattered on trunks (Text-fig. 2, fig. 1). At base of one short trunk is a small clump of respiratory caeca. Two elongate, tubular Polian vesicles.

A tuft of short unbranched genital caeca filled with large eggs lies at middle of body (Text-fig. 2, fig. 1). Long genital duct opens to exterior in mid-dorsal interradius, immediately posterior to tentacles.

Intestine, gonad, and (to a lesser extent) respiratory trees held close against lesser curvature of body by a short, fragile dorsal mesentery; thus large portions of body cavity virtually empty. Radial muscles thin strands, retractors well developed.

Calcareous deposits in bodywall exclusively single-layered, oval to rectangular plates (Text-fig. 2, fig. 3), with many perforations and an average length of 1.0mm. Most plates bear a single tall excentric spire, which lies near edge; spire spinous (Text-fig. 2, fig. 2), up to 0.7mm in length, derived from three vertical pillars joined by several crossbars. Smaller perforated plates, lacking spires, also common, especially near anterior and posterior ends of body. Tubefeet pass between plates, not through them. Tentacles contain large numbers of curved rods, of average length 0.3mm, perforated mainly at extremities, and with short blunt projections (Text-fig. 2, fig. 4).

Remarks: These specimens represent Echinocucumis hispida, or a near relative of that species. Some slight differences in the calcareous deposits and internal anatomy between the present specimens and the typical E. hispida are evident. The large spired plates in the New Zealand specimens seem to have more numerous perforations than those in E. hispida from northern waters. In addition Deichmann (1930) notes that the respiratory trees are "quite abortive, with 1–2 small lobes" in E. hispida, while Heding (1942) states that the trees are well developed, and each has "two main branches of nearly equal size". In the page 9
Text-fig. 2.—Echinocucumis hispida (Barrett): Fig. 1, internal anatomy, right lateral view (partly diagrammatic); Fig. 2, spires from plates; Fig. 3, spired plates; Fig. 4, tentacle deposits. Abbreviations: c.r., calcareous ring; g.d., genital duct; g.tub., genital tubules (caeca); p.v., polian vesicle; r.m., retractor muscle; resp.t., respiratory tree; r.l.m., radial longitudinal muscle.

Text-fig. 2.—Echinocucumis hispida (Barrett): Fig. 1, internal anatomy, right lateral view (partly diagrammatic); Fig. 2, spires from plates; Fig. 3, spired plates; Fig. 4, tentacle deposits. Abbreviations: c.r., calcareous ring; g.d., genital duct; g.tub., genital tubules (caeca); p.v., polian vesicle; r.m., retractor muscle; resp.t., respiratory tree; r.l.m., radial longitudinal muscle.

page 10 New Zealand specimens the trees are not of equal size (Text-fig. 2, fig. 1), and while there are two main branches in one tree, the other has one branch, and a small bunch of caeca at its base (an aborted second branch?).

Echinocucumis hispida is known from the north-eastern part of the Atlantic Ocean, from the West Indies (as Echinocucumis hispida forma atypica Deichmann) and from east of New Zealand. The species is presumably cosmopolitan, and has a known bathymetric range of about 50 metres to 1,400 metres.