Neanthes kerguelensis (McIntosh 1885)

“Nereis kerguelensis, Baird ? (Pl. XXXV. figs. 10, 11, 12 ; Pl. XVI_A. figs. 17, 18).

Habitat.—Dredged off Kerguelen, in 10 to 100 fathoms. A variety occurred at Station 149_E, to the west of Cape Maclear, Kerguelen, January 21, 1874 ; depth, 30 fathoms ; sea-bottom, volcanic mud.

Head about as long as broad ; tentacles somewhat stout, considerably shorter than the head. Eyes rather large, widely separated transversely, but approaching each other antero-posteriorly ; no trace of a lens. Palpi large, but the terminal boss is small. Tentacular cirri of moderate length, the longest reaching the ninth foot. Paragnathi­—I. two points, or absent ; II. triangular groups of small points ; III. a small and somewhat irregular series ; IV. larger triangular groups than II. ; V. absent; VI. a single point in each ; VII. and VIII. five single points, each in a lozenge. Maxillæ brown, five large teeth below the bare region at the fang. The first segment is very little broader than the succeeding. The feet anteriorly have more elongated processes than in Nereis dumerilii, while posteriorly they are less elongated. The cirri are shorter than in the latter species. Dorsal bristles have comparatively short tips ; falcate bristles have somewhat elongated tips.

A fragment, consisting of forty segments of the anterior region, measuring 28 mm. in length, with a diameter at its widest part of about 5 mm. including the bristles.

The head (Pl. XXXV. fig. 10) is about as long as broad. The tentacles are rather stout, and considerably shorter than the head. The basal portions of the palpi are large, the terminal boss on the other hand being small. The longest tentacular cirrus reaches to the ninth foot, but the body is much contracted in front (the proboscis being extruded). The eyes on each side are wide apart, and of considerable size, the anterior pair being the larger. There is no trace of a lens.

The extruded proboscis exhibits dorsally a point (VI.) on each side of the basal (buccal) region in front of the palpi, and a somewhat triangular group of small paragnathi (II.) on each side of the base of the maxillæ. Ventrally there is a similar but larger group (IV.) corresponding to the latter; and in the centre a small series (III.), in a line drawn between the posterior borders of the lateral groups. The buccal (basal in extrusion) region has a single point of considerable size in each lozenge (formed by the wrinkles), in all five in number (VII. and VIII.). It is interesting that, though differing in number and in the outline of the spaces, these occur on the same sites as in Nereis pelagica, Linn. The maxillæ show five large teeth, a portion at the tip being bare.

In the variety from Cape Alaclear the basal ring of the proboscis in extrusion shows dorsally a single point (VI.) in front of each palpus, a feebly developed double row (II.) near the base of the maxillæ,and two points (I.) between them. Ventrally there is a larger patch of paragnathi (IV.) at the bases of the maxillæ on each side, besides a some­what scattered group (III.) in the centre. The basal collar (VII. and VIII.) has six points, five of them being very distinct.

The feet as a whole do not show any marked change of series. They have the glandular pigment-spots analogous to those of Nereis dumerilii. The tenth foot (Pl. XXXV. fig. 11)^. presents more elongated processes than in the latter species. Dorsally is a somewhat large tapering cirrus, which extends beyond the tip of the first lobe. The latter is broadly triangular, the upper and lower edges being also convex. The second lobe is double, since an unusually large process occurs in front of the bristles. The larger division is somewhat ovoid, with a blunt tip, which scarcely reaches that of the superior lobe. The double setigerous lobe beneath extends quite as far outward as the foregoing. The inferior lobe is lanceolate, the point falling short of the setigerous region above. The ventral cirrus proceeds a little beyond the middle of the latter lobe. Superiorly the bristles are all setose, with comparatively short tips (Pl. XVI_A. fig. 17). The very fine spikes or setæ on these are hardly seen under ordinary circumstances, except as a filmy margin. Similar bristles occur at the superior border of the inferior series. One or two falcate forms with elongated tips occur in the same group. The next division of the inferior series shows superiorly setose forms with shorter tips, and inferiorly a number of falcate bristles with long spinose tips (PL XVI_A. fig. 18), some of which have an adnate wing just under the terminal hook.

At the thirty-seventh foot (Pl. XXXV. fig. 12) all the lobes have become more acute. The dorsal cirrus is more prominent, and extends about half its length beyond the superior lobe. The latter nearly forms an isosceles triangle. The second lobe has its accessory superior process much diminished (in comparison with the tenth foot) ; its inferior margin is convex at the base, its tip is pointed, and does not reach as far outward as the superior lobe. The setigerous lobes are massive, broad at the base and acute at the tip. The inferior lobe does not reach as far outward as the latter. The ventral cirrus passes along two thirds of the margin of the inferior lobe.

In the intestine is muddy debris containing long sponge-spicules, fragments of Radiolarians, a few Gregarinæ (parasitic), fragments of Algae, often with groups of chlorophyll-granules, and many Diatoms.

The nerve-cords in this form are arranged somewhat like those of Nereis pelagica, Linn., viz., above the attachment of the oblique muscles, and connected with the hypoderm by a median pedicle. They have thus externally the attachment and decussation of the oblique muscles, the thin circular fibres, hypoderm and cuticle. The ventral longitudinal muscles have a comparatively small pennate fold superiorly and externally. The perivisceral cavity contains large granular ova in the larger example dredged off Kerguelen in 10 to 100 fathoms. In these and allied forms a series of vertical fibres are found between the oblique muscles, passing up on each side of the nerve-cord to the wall of the alimentary canal, the fibres partly keeping to the same side, and partly crossing to the opposite.

This appears to correspond with an imperfect specimen collected at Kerguelen by the “Antarctic” Expedition, and presented to the British Museum by the Admiralty, though no description by Dr. Baird has yet been found. It is allied to the Nereis (Lycoris) masalacensis of Grube¹ from Masalac in the Philippines.”

(McIntosh, 1885)

Known from seamounts and knolls

Ninety-six entire specimens examined: length 5.9–61.3 mm, width 0.7–3.3 mm (excluding parapodia, measured at 8th chaetiger) for 29–70 chaetigers. Colour pale cream in alcohol, some with dark brown, uniform shading remaining over anterior chaetigers. Body depressed dorso-ventrally, of mostly uniform width, tapering in last few chaetigers. Prostomium longer than broad (Fig. 4A), antennae and palps about equal in length, with antennae 1/4 width of palpophores. Palpostyles very short, 1/5 length of palpophores. Four pairs tentacular cirri, postero-dorsal pair extending 2–7 chaetigers, usually 2–3. Two pairs small, equal-sized, black eyes, anterior pair more laterally placed. Pharynx with conical paragnaths (Fig. 9C, D), variable in size, sometimes faint, not easily lost. Paragnaths arranged as follows: I = 1 (absent or too small to see in specimens of less than 45 chaetigers); II = 1–8; III = 1–9; IV = 6–17; V = 0; VI = 1 (2 on one specimen only); VII–VIII = 3–8. Jaws dark brown to black, 7–10 teeth. Notopodia with dorsal and median ligule throughout. Of almost equal size, globular anteriorly (Fig. 4B), dorsal ligule becoming conical, median ligule becoming digitiform, in median chaetigers. Notopodial prechaetal lobe present from chaetigers 5–6 (Fig. 4B), increasingly fused to median ligule, absent posteriorly, difficult to determine more precisely due to the very gradual fusion, generally obvious for at least 10 chaetigers. Dorsal cirrus 1–1.5 times length of dorsal ligule anteriorly (Fig. 4B), increasing to 2–2.5 times length posteriorly (Fig. 4C). Neuropodia with postchaetal lobe and ventral ligule throughout; postchaetal lobe rounded anteriorly, reduced in size and digitiform posteriorly, ventral ligule globular anteriorly, conical posteriorly (Fig. 4B, C). Ventral cirrus approximately 3/4 length of ventral ligule, becoming equal in length posteriorly (Fig. 4B, C). Parapodia biramous from chaetiger 3, sub-biramous on chaetigers 1–2. Notochaetae homogomph spinigers only. Neurochaetae with homogomph spinigers and heterogomph falcigers (Fig. 4D, E) in both superior and inferior (from 3) fascicles throughout. No heterogomph spinigers found. Pygidium terminal; 2 long, tapering anal cirri inserted ventrally.

Recorded widely across the southern hemisphere including Australia, New Zealand, Tasmania, Fiji, Taiwan, Antarctic Peninsula, sub-Antarctic Islands (incl. Kerguelen, Macquarie, South Shetlands, South Orkneys), Chile and the Falkland Islands. Previous records from the Falkland Islands exist from Pratt (1898), Fauvel (1916), Ramsay (1914), Monro (1930) and Hartman (1953) and the species was recorded from almost every location sampled during this survey. Neanthes kerguelensis is also recorded from the Northern hemisphere from the Mediterranean and Azores (von Marenzeller 1902) and the UK (Comely 1973). The latter record, however, is discounted as the author describes his specimen as having 6–7 paragnaths in Area VI which would not identify it as this species.