Herdmania momus, (SAVIGNY, 1816)

Kott, Patricia, 2002, The genus Herdmania Lahille, 1888 (Tunicata, Ascidiacea) in Australian waters, Zoological Journal of the Linnean Society 134 (3), pp. 359-374 : 366-369

HERDMANIA MOMUS ( SAVIGNY, 1816) ( FIG. 4 )

Cynthie momus Savigny, 1816: 143 .

? Halocynthia momus: Sluiter, 1905a: 102 ; 1905b: 13.

Pyura momus: Hartmeyer, 1909: 1340 .

Pyura momus f. typica Michaelsen, 1918a: 9; 1918b: 30.

Herdmania momus f. curvata Kott, 1952: 282 ; 1964: 143.

Herdmania momus: Millar, 1975: 317 ?. Kott (1981): 208; 1985: 338 (part only).

Cynthia papietensis Herdman, 1882: 143 ; 1886: 406.

Herdmania contorta Monniot, 1992: 18 .

Herdmania curvata: Kennett, 1997: 86 . Kott (1998): 179.

Cynthia pallida: Herdman, 1886: 406 .

Cynthia pallida billitonensis Sluiter, 1885: 183 ; 1890: 331.

Rhabdocynthia tenuis: Sluiter, 1895: 24 .

Distribution

Previously Recorded. Queensland (SE Qld, Kott, 1964; Great Barrier Reef, Kott, 1952, 1964, 1985). Western Pacific ( Fiji, Kott, 1981; French Polynesia, Herdman, 1882, 1886; Coral Sea Plateau, Monniot, 1992). Indonesia ( Ambon, Billiton, Sluiter, 1885, 1890, 1895; Herdman, 1886). Indian Ocean ( Sluiter, 1905a,b?). Red Sea ( Savigny, 1816; Michaelsen, 1918a,b).

Examined Material. Queensland (Moreton Bay, QM G308580; Noosa, QM G4965; Capricorn Grp, AM Y1811 holotype H. curvata Kott, 1952 ; AM Y2334 paratypes H. curvata Kott, 1952 ; G9363 G10014 GH2554; Keppel I., G11999); Swain Reefs (QM GH4842.; Lizard I., GH771). Philippines (QM GH561-2).

Herdmania momus is tropical and in Australia has a recorded range in Queensland waters between Moreton Bay and Lizard I. where it is the common species in shallow water reefal and littoral habitats ( Kott, 1964). It has not been recorded from the western coast of the continent although it is known from Indonesia and, in view of its presence in the Red Sea, is very likely to occur in the Indian Ocean. Herdmania pallida is recorded from the Arafura Sea ( Tokioka, 1952) and Torres Strait (see below), but there are no records of the present species from the northern coast of the continent.

Description

Smaller specimens to 3 cm pink with translucent test; larger specimens (to 8 cm) test becomes tough, opaque or even leathery, especially anteriorly (QM G10014). Cylindrical siphons originate close to one another on upper surface, branchial siphon directed laterally and atrial siphon vertical. Minute spicules just under the surface layer of test, larger ones in internal layer. Largest spicules (to 1.5 mm long) in posterior end of body wall. They are shorter anteriorly and in blood vessels of branchial wall. Spines longitudinally arranged and parallel in siphons, but randomly orientated in body wall, in which they form a felt-work of calcareous spicules when it contracts. Circular muscles surround each siphon. On each side, about 20 longitudinal branchial muscles and 15 longitudinal atrial muscles radiate over the anterior half of body terminating at the same level just anterior to horizontal gut loop on left and gonad on right. Anterior atrial muscles and posterior branchial ones cross each other. Dorsal tubercle, a small cushion in large open peritubercular ‘V’, usually has U-shaped slit with opening directed anteriorly in smaller specimens; larger specimens with both horns turned in or out, sometimes forming double spiral. One specimen (QM GH2554) has two separate U-shaped openings, the left one with the gap turned to the left. In one large specimen (8 cm) the dorsal tubercle is a circular cushion with a complex convoluted slit. Dorsal lamina a wide membrane with laterally flattened languets on the edge. In an 8 cm specimen the branchial sac has 8–12 wide, longitudinal folds on each side. Depending on size of individual, one to six internal longitudinal vessels are between dorsal lamina and dorsal fold. Gut in posterior half of body forms simple horizontal loop enclosing left gonad. Liver composed of several compact masses of small, vertical, crowded tubules tightly enclosed in body wall over pyloric region. Anal lobes variable, anus basically bilabiate with each lip subdivided into long, sometimes branched, ribbon-like lobes (QM G4965 G9363) or one or two triangular lobes with scalloped margins (QM G10014). Variations in anal border are not size dependent. Gonads, one on each side of the body, consist of a long ovarian tube in characteristic tight undulations obscured by an opaque band of testis follicles that undulates from side to side along the top of the ovary. Testis ducts numerous, short and vertical, with elliptical openings that appear to be sessile between crowded testis follicles. Oviduct short with fan-shaped to semicircular hood projecting from body wall just behind triangular oviducal opening close to anus. Oviducal hood large delicate, membranous, transparent in smaller specimens folding down over tip of oviduct to form conical chamber in front of opening. Smaller, firmer hood with vascular network in it forms slightly concave lid over oviducal opening in larger specimens. In large (about 6 cm) specimens from Philippines oviducal hood is a wide, fan-shaped flap, packed with spines symmetrically arranged across its width.

Remarks

Michaelsen (1918a,b) reviewed and tabulated those taxa (as formae) known to contain the long echinated needle-like spines characteristic of this genus. In the group he assigned to f. typica ( Michaelsen, 1918b: 40 no. 42) are specimens with the ovary a straight tube with small branches and testes around the edges. These and other specimens may not be accurately assigned. Nevertheless he interpreted the type specimens of H. momus as having a continuously winding band of testis follicles along the top of the ovary. Although neither Savigny nor Michaelsen saw the separate male ducts, Savigny (1816) correctly identified the oviducal opening with a membranous ‘cornet’ around it. Kott (1957, 1966, 1972a) referred to H. momus var. curvata as a junior synonym of H. momus var. typica . Later (1985), she regarded all varieties of Herdmania as growth forms of the one taxon until Kennett (1997) observed the release of sperm from many points along the surface of the ovary. The multiplicity of separate short vasa deferentia from crowded clumps of lobed testis follicles were duly demonstrated, evenly spaced along the curved band of testis follicles on the surface of a tightly curved ovarian tube in specimens referable to H. curvata Kott, 1952 (a senior synonym of H. contorta Monniot, 1992 : see Kott, 1998), now known to be a junior synonym of H. momus . Although Monniot (1992) shows a male duct opening at the base of the oviduct ( Monniot, 1992, fig. 6b), he reports that he did not see either a vas deferens or its opening.

Cynthia pallida billitonensis Sluiter, 1885 from Indonesia has relatively few longitudinal muscles, the dorsal tubercle and dorsal lamina are like H. momus and the convoluted course of the testis follicles along the surface of the ovary can be seen in the figure ( Sluiter, 1885; pl. IV figs 1–2). Also like the present species, Rhabdocynthia tenuis: Sluiter, 1895 from Ambon, with a translucent thin, gelatinous test, has seven folds per side, two internal longitudinal vessels in the interspace, a broad dorsal lamina with long thin languets and the slit on the dorsal tubercle with both horns spiralling in. It is taken from the same location as Cynthia pallida: Herdman, 1886 , which also has a undulating ovary. Cynthia papietensis Herdman, 1882 and 1886, from Tahiti, with the same broad dorsal lamina as the present species and lacking internal longitudinal branchial vessels between the dorsal midline and the dorsal folds, is conspecific.

Herdmania momus: Millar, 1975 from Japan, Singapore and Indonesia cannot be accurately assigned owing to lack of information on gonads and gonoducts. Some specimens of the present species may be included, although others also may be present.

The species is distinguished by the tight undulations of its ovarian tube; the hood over and in front of the oviducal opening produced from the body wall over the oviduct; the undulating band of crowded clumps of testis follicles along the top of the ovary; a separate short, vertical duct from each clump of testis follicles; absence of a male opening at the base of the oviduct; relatively small dorsal tubercle with one or two Ushaped openings with the horns turned or spiralling in or out (except in one large specimen 8 cm, in which the slit is convoluted); and relatively few internal longitudinal vessels between the dorsal lamina and dorsal fold.

Herdmania momus: Nishikawa, 1991 from the Sea of Japan has an oviducal hood and numerous vas deferens openings but the course of the ovary is not recorded. Herdmania fimbriae has a lobed anal border, an undulating ovarian tube and an oviducal hood, but it has a large, straight common vas deferens with a single opening surrounded by an elaborate membranous fringe. Herdmania mentula has a similar oviducal hood but a common vas deferens projecting into the atrial cavity at its distal end, a gently undulating ovary and the anal rim divided into four smooth, shallow lips.

Herdmania inflata ( Van Name, 1918) , from the Philippines ( Fig. 5A ), like the present species has many short vasa deferentia opening over the surface of the male follicles which are in a conspicuous undulating band. However, in H. inflata the ovary is straight, it lacks an oviducal hood, the vas deferens is less interrupted and the separate openings fewer than in H. momus and the terminal part of the vas deferens opens with the oviduct, on a cylindrical short projection into the atrial cavity.

Figures

Figure 4. Herdmania momus (A, C, QM G10093; B, QM GH561; D, L, QM G308151; E-G, QM G9363; H, QM GH2554; I-K, QM GH771): A, body from left side showing muscles; B, portion of dorsal lamina; C, D, dorsal tubercles; E, gut loop and gonads; F-H, distal part of gonad showing oviducal hood and male openings surrounded by testis follicles; I, testis follicles with tips of vas deferens showing amongst them; J, clumps of testis follicles with vas deferens; K, L, anal borders. Scale bars: A, E = 5.0mm; B-D, F = 1.0mm; H, J = 0.5mm; K, L = 2.0 mm.

Figure 5. Herdmania inflata (A, USNM 6037): A, distal portion of right gonad. Herdmania pallida (B, E, QM G12803; C, QM 12792; D, AM Y1813): B, body from left side showing muscles; C, portion of dorsal lamina; D, E, gut loops and gonads. Scale bars: B, D, E = 5.0mm; A, C = 1.0mm.