Lophocalyx profundum, Janussen, Dorte & Reiswig, Henry M., 2009

Janussen, Dorte & Reiswig, Henry M., 2009, Hexactinellida (Porifera) from the ANDEEP III Expedition to the Weddell Sea, Antarctica, Zootaxa 2136, pp. 1-20 : 7-10

Lophocalyx profundum n. sp.

( Figs. 4 & 5 , Table 2 )

Material examined: Holotype, SMF 10524, ANDEEP III, R.V. 'Polarstern', stn PS67/080-6, Weddell Sea, Antarctica , 22 Feb. 2005, 70°40.23'S, 14°43.78'W to 70°40.42'S, 14°43.83'W, 3006– 2978 m, ethanol. Paratypes: SMF 10605, and SMF 10604, same data

Description: All three specimens are small globular, nearly spherical forms ( Figs 4 A–C), 19–23 mm in diameter, with small terminal osculum 4–9 mm in diameter with smooth margins (without marginalia). Short basal extensions project from the lower margin, increasing contact with the substratum; attachment appears to be a combination of both direct (basiphytous) anchorage to small pebbles and insinuation of anchorate prostalia into sediments (lophophytous). All external surfaces carry prostalia projecting individually (not in tufts) up to 23 mm; these consist of a mixture of three spicule types: stout diactins, raised hypodermal anchorate pentactins, and raised regular hypodermal pentactins. Anchorate pentactins have not been found in the paratypes but since the distal ends of all prostalia are broken, they may well have been present in raised position before collection. The atrial cavity is deep and narrow; the body wall is up to 6 mm in thickness. The general surface is smooth, tissues are soft but well supported by spicules, and the color is light brown (khaki). Spicule fusion does not occur in any of the specimens.

Megascleres (dimensions in Table 2 ) consist of hypodermal (and prostal) anchorate pentactins, hypodermal (and prostal) regular pentactins, diactine dermalia, pinular hexactine atrialia, thick prostal and primary diactins, and thin choanosomal diactins. Anchorate hypodermalia ( Figs. 4 E, 5A) have tangential rays bent abruptly back from 30 to 90° near their mid-points; they are covered with fine spines (shagreen) but the proximal ray is smooth. Ray tips are parabolic-rounded or bullet-shape. Regular hypodermal (and prostal) pentactins ( Fig. 5 B) have straight to undulatory tangential rays; some are entirely smooth except for roughening at ray ends; other pentactins are entirely finely tuberculate. Dermalia are almost exclusively rough diactins ( Figs. 4 H, 5E), but a very few stauractins, triactins and monactins can be found amongst this spicule type; ray tips may be sharp-pointed, rounded, or inflated, depending upon spicule thickness; the central swelling is usually well developed with two alternate rays being developed to short stumps up to 20 µm long. Atrialia are sub-pinular hexactins ( Fig. 5 F) that lie embedded deep within the atrial tissues in subatrial position; the pinular ray is not bushy but distinguished from the other rays by its greater length, extent of spination, and curvature; these spicules are mostly smooth but all ray ends are rough and terminate in parabolic-rounded tips. Prostal and principal choanosomal diactins ( Fig. 5 C) are moderately thick, slightly curved, and entirely shagreened with larger spines developed near the ray ends; the ray tips are rounded with a bare cap and they bear no distinct central swelling. Thin choanosomal diactins ( Fig. 5 D) are abundant smooth spicules with rounded to parabolic roughened tips and usually a slight swelling at the spicular center. They occur primarily in bundles.

Antarctica (dimensions in µm unless otherwise indicated).

Microscleres (dimensions in Table 2 ) consist of oxyhexasters, hemioxyhexasters, rare oxyhexactins, and strobiloplumicomes. Oxyhexasters and hemioxyhexasters are the most abundant microscleres ( Figs. 4 D & F, 5G); their short primary rays each bear 1–3 thin straight terminals; both primary and terminal rays are covered with very fine recurved thorns only visible with SEM; very rarely are terminals bent or curved; rare oxyhexactins occur among this spicule category. Strobiloplumicomes ( Figs. 4 G, 5H) are uncommon and usually broken; each short primary bears a small subterminal spherical swelling from which about 40 sigmoid terminal rays arise in 4–5 whorls, the terminals of each successively distal whorl being longer than those of the more proximal whorls. The terminals all bear two rows of sharp recurved thorns on the inner concave surface of their distal halves, endowing this spicule type with enormous snaring capacity – when another spicule has been "grasped", they can only be separated by destruction.

Etymology: The species name, profundum , reflects the great depth from which this form has been collected.

Remarks: This new species possesses all of the characters defining the genus Lophocalyx . It differs from all ten previously known species, as summarized by Menshenina et al. (2007), in having diactins as the major dermal spicule. All other species have either stauractins, hexactins, or a combination of hexactins and pentactins as dermalia.

Figures

FIGURE 4. Lophocalyx profundum, n. sp. A. Holotype deck photo (SMF 10524). B. & C. Paratypes, deck photos. D. Oxyhexaster (SEM). E. Anchorate hypodermalium tip (SEM). F. Segment of oxyhexaster terminal ray (SEM). G. Terminal tuft of strobiloplumicome (SEM). H. Diactine dermalium (SEM). (All spicules from holotype).

FIGURE 5. Spicules of Lophocalyx profundum, n. sp. holotype (SMF 10524). A. Anchorate hypodermal pentactin in end and side views. B. Two regular hypodermal pentactins with enlargements of tangential and proximal ray ends. C. Thick diactin with enlargements of ends. D. Thin choanosomal diactin with enlargements of ends. E. Diactine, triactine and monactine dermalia. F. Pinular hexactine atrialium with enlargements of ray ends. G. Oxyhexaster with enlargement of terminal ray segment. H. Strobiloplumicome in optical section with rays perpendicular to the page omitted, with enlargement of a terminal ray end.

Tables

TABLE 2. Spicule dimensions of Lophocalyx profundum, n. sp., holotype, SMF 10524, from the Weddell Sea,

parameter	mean	st. dev.	range	n.
Anchorate hypodermalia
tangential ray length	958	189	610–1,463	54
tangential ray width	53.1	16.0	24.2–102.4	72
proximal ray length (mm)	6.36	2.36	0.39–13.64	17
proximal ray width	53.9	19.7	29.0–107.0	29
Regular hypodermalia
tangential ray length	702	170	445–1,650	152
tangential ray width	33.8	6.7	20.8–50.3	50
proximal ray length (mm)	1.10	0.52	0.15–2.59	57
proximal ray width	32.6	6.9	12.4–52.8	59
Dermal diactin ray length	225	27	164–291	50
width	10.2	2.1	6.6–15.1	50
Atrial pinular hexactin
pinular ray length	490	90	309–663	51
pinular ray width	23.9	5.7	11.5–39.4	66
tangential ray length	492	101	248–766	118
tangential ray width	26.1	5.1	15.0–35.8	50
proximal ray length	306	92	144–526	54
proximal ray width	22.7	4.9	12.5–32.6	61
Thick diactin length (mm)	12.27	3.56	8.17–14.65	3
width	65.0	9.8	35.1–79.9	20
Thin diactin length (mm)	3.07	1.12	1.46–5.97	50
width	14.4	5.0	5.5–31.5	50
Oxyhexaster diameter	141	16	108–182	50
primary ray length	7.1	1.5	4.8–11.9	50
secondary ray length	64.9	7.1	50.8–83.4	50
Plumicome diameter	59.4	5.1	49.5–69.9	50
primary ray length	11.7	1.3	9.6–15.0	50
long secondary ray length	22.2	2.1	16.6–27.2	50