Paraescarpia echinospica, Southward & Schulze & Tunnicliffe, 2002

Southward, Eve C., Schulze, Anja & Tunnicliffe, Verena, 2002, Vestimentiferans (Pogonophora) in the Paci c and Indian Oceans: a new genus from Lihir Island (Papua New Guinea) and the Java Trench, with the rst report of Arcovestia ivanovi from the North Fiji Basin, Journal of Natural History 36 (10), pp. 1179-1197 : 1183-1192

Paraescarpia echinospica gen. nov, sp. nov.

(gures 3–7)

Material examined

FS Sonne; cruise SO-133; 1 km SE of Edison Seamount ; 03ss19.4¾S, 152ss35.5¾E; depth 1600 m; 26 July 1998; Grab 44 GTV, mussel clump, one specimen ; Grab 45 GTV, sediments near mussel clump, three specimens .

FS Sonne, cruise SO-139, Java Trench, sample 100KD; 06ss25.01¾S, 104ss49.53¾E; depth approx. 1100–1550 m; 25 February 1999; Chain-Bag Dredge, one specimen.

Types

HOLOTYPE: female (specimen #4) from SO-133 45 GTV (Senckenberg Institute SMF 10034) ; PARATYPES: two specimens from SO-133 45 GTV (Senkenberg Institute SMF 10035, 10036 ) .

Type locality Edison Seamount, Lihir Island.

Description

Edison Seamount specimens. Three of the tubes have a segmented anterior region with large funnel-shaped collars or anges at the anterior margins of the segments (gures 2, 3; table 1). The anteriormost funnel is particularly wide (20–25 mm). Below the segmented region, the tube is smooth surfaced and about 10 mm diameter, tapering gradually to about 5 mm and then more rapidly to about 1 mm. The thin wire-like posterior region of the tube (gure 3B) continues for a considerable distance, 400 mm in one specimen. The segmented anterior part is colonized by stalked barnacles (gure 3B, C), polychaetes and, sometimes, byssus threads of mussels, whereas the smooth posterior part is clean. In situ photographs show the anterior ends of tubes standing above the sediment while the posterior parts appear to be buried in the sediment (gure 2). The tubes are brownish buOE in colour, with dark lines at the segment boundaries. The tube walls are stiOE, multilayered and di cult to cut.

The fourth tube is white and about 10 mm in diameter anteriorly, with a clean surface and small overlapping increments near the top (gure 3A). It is at an earlier stage of growth than the other three tubes and lacks their characteristic funnels. The animal inside is the only male.

The only complete animal was 720 mm long, in a tube more than 1 m long. Its opisthosoma lay within the narrow posterior part of the tube.

Among the four specimens the obturaculum ranges in length from 15 to 22 mm; the diameter is half to two-thirds the length ( table 1; gure 4A, D). The anterior surfaces of the obturacular halves are covered by a brownish cuticular crust about 1 mm thick (gure 4D). Sections show that the surface is a rough pavement of small blocks, each made up of multiple thin columns (gure 4C), whereas the basal 200 M m of crust is colourless and multilayered.

The obturacular surfaces surround a thick, yellowish brown spike, secreted by the epidermis posterior to the encrusted region (gure 4A, D); most of the spikes are broken oOE short, but the one complete spike tapers to a sharp point and is 20 mm long (gure 4A). The maximum spike diameter is 8 mm. The spikes are made of cuticular material containing ne bres that run outward from the centre to strong spines on the surface. Transverse sections of the spike show parallel waves in these bres, giving the appearance of iridescent zones (gure 4B). The top of the obturaculum is cylindrical, while the stalk is elliptical in cross section (gure 4D). The laments making up the anterior ve to seven branchial lamellae are straight and smooth, without pinnules (gure 5A). The major part of the plume is composed of thinner, pinnulate, laments with short, curled tips forming a velvety surface layer. Their oval pinnules are extremely small (gure 5B). The proximal parts of the laments adhere to one another, lying parallel to the axis of the obturaculum and the thickness of the base of the plume is increased by many rows of short laments, within the collar folds (gures 4D, 5C). The vestimental region is 50–70 mm long and the lateral vestimental folds terminate midventrally, without fusing, behind the ventral ciliated eld (gures 3C, 5D).

The long trunk becomes very narrow posteriorly. It bears numerous epidermal papillae, of two types, the smaller ones topped by plaques and the larger ones without plaques (size range 50–80 M m). The papillae on the vestimental region are about 100 M m in diameter and are topped by plaques about the same size. All the plaques are oval and colourless, with raised anterior margins (gure 5E, F).

The opisthosoma has about 15 chaetigerous segments (gure 6A), carrying irregular, single to triple rows of chaetae. The heads of the chaetae are 7–9 M m long, 4 M m wide, with a small anterior group of two to three teeth and a larger posterior group arranged in three to four rows (gure 6B).

Specimen from the Java Trench. When rst collected the tube was thought to be a bamboo stick. The preserved material consists of a vertical slice of the anterior end of the tube, plus the anterior 65 mm of the animal. The tube has a spreading anterior funnel and three more well-marked collars, each 7–8 mm long on the 65 mm long fragment. The animal has an obturaculum about 15 mm long, 10 mm diameter, with a brown crust and a massive brown spike, elliptical in cross section, 20 mm long, broken anteriorly, and 4–6 mm diameter. The surface of the spike is covered with spines. The plume of branchial laments is shorter than the obturaculum; there appear to be anterior smooth laments and posterior pinnulate laments, but their condition is poor. The vestimental region is 47 mm long and 11 mm wide and the posterior vestimental fold is split, as in the Edison Seamount specimens. There is no obvious diOEerence from the Edison Seamount specimens, but the animal and tube are incomplete.

Internal anatomy of Edison Seamount specimens. The excretory system is in the anterior part of the vestimental region. There is a fused medial excretory organ, consisting of small branching tubules, extending from the dorsal area of the brain anteriorly to the sinus valvatus posteriorly, penetrated by the paired obturacular vessels and their perivascular cavities. There is no obvious connection between the perivascular coelom and the excretory organ. Two large excretory ducts drain this medial organ, running rst posteriorly and then turning to run anteriorly, dorsal to the brain. The ducts unite just before reaching a single, slit-like excretory pore, opening dorsally close to the narrow base of the obturaculum (gure 7).

In the trunk, the lobes of the trophosome surround the reproductive organs, as a brownish to blackish tissue. Its cells are lled with globular bacteria, those observed by SEM vary in diameter from 1.5 to 3 M m (gure 6C).

The gonoducts of the female, found by dissection, lie dorsally in the paired trunk coeloms and open through gonopores into the dorsolateral grooves of the vestimental region, some 10 mm in advance of the hind ends of the vestimental folds. The largest oocytes in the oviducts are about 150 M m in diameter. In the male, as revealed by light microscopic studies of histological sections, external genital grooves are present but are short and shallow and are lined by glandular tissue which appears to be the same as that which covers the entire dorsal vestimentum. There are no prominent genital ridges. The male gonopores are near the posterior ends of the vestimental folds. Sections of the left side of the trunk show that the distal genital duct is lined by a densely ciliated glandular epithelium. Its lumen is lled with globular secretions and sperm. Posteriorly it joins the left central seminal channel.

The proximal genital duct is lined with a strongly folded ciliated epithelium without any obvious gland cells. From the anterior seminal channel, sperm sacs extend anteriorly, lled with clusters of sperm. The sperm have spirally grooved nuclei about 27 M m long (gure 6D).

Comparison with other species

Escarpia spicata and E. laminata both have crusted obturacula and E. spicata has a central spike, rather thinner than that of the new species. Escarpia laminata has a thin median plate ( Jones, 1985). Both have anterior branchial laments without pinnules and posterior laments with pinnules, a single excretory pore and no dorsal groove on the obturacular stalk ( table 2). The chief character diOEerentiating the new species from E. spicata and E. laminata is the split posterior vestimental fold and this is the character that distinguishes the new genus Paraescarpia .

A wide gap in the posterior vestimental fold occurs in all Lamellibrachia species ( Webb, 1969; Southward, 1991; Miura et al., 1997) but the genus Lamellibrachia is distinguished from Paraescarpia by its special lamellar sheaths around the branchial plume ( table 2) and by the smooth anterior surface of its obturaculum, without crust or spike. The other vestimentiferan genera have a continuous posterior vestimental fold, but studies of the formation of vestimental folds in juvenile Ridgeia piscesae and Riftia pachyptila show that the lateral folds form rst, the collar folds next, and the posterior ends of the lateral folds later fuse to form the ventral fold ( Jones, 1988; Southward, 1988; Jones and Gardiner, 1989). Thus, Paraescarpia and Lamellibrachia show incomplete development of the vestimental folds, in comparison with the other genera.

Collars on the tubes of many vestimentiferan species vary considerably in size and frequency, notably in Ridgeia piscesae ( Southward et al., 1995) . The three larger tubes of Paraescarpia echinospica have a wide anterior funnel followed by a series of wide collars (gure 3B, D), while the lack of any funnel on the smallest tube (gure 3A) shows that funnels are initiated at a late stage in tube growth. Escarpia laminata and E. spicata lack collars on the tube at any size ( Jones, 1985). Most Lamellibrachia species have collars of some sort, with the exception of L. columna , so the presence or absence of collars need not be a generic character.

The morphology of the excretory organs has been investigated in several vestimentiferans (Schulze, in press) and certain distinctions have been noted between genera, particularly in the topology of the excretory ducts. Paraescarpia echinospica has looped excretory ducts and a single excretory pore, as do Escarpia and Lamellibrachia species.

Analysis of the 16S rDNA gene of Paraescarpia echinospica by K. M. Halanych (personal communication) supports its closer relationship to the genus Escarpia than to Lamellibrachia .

We place the new genus Paraescarpia in the Escarpiidae , and the diagnosis of this family has been widened to include Paraescarpia and Escarpia (p. 1183).

Etymology

The generic name Paraescarpia is derived from para (Latin) meaning like, and Escarpia , an existing generic name ( Jones, 1985). The speci c name echinospica is descriptive of the remarkably spinous surface of the obturacular spike, from echinus (Latin), a hedgehog and spica (Latin), a spike.