Eduarctus pyrrhonotus, Holthuis, 2002

Holthuis, Lipke B., 2002, The Indo-Pacific scyllarine lobsters (Crustacea, Decapoda, Scyllaridae), Zoosystema 24 (3), pp. 499-683 : 602-607

Eduarctus pyrrhonotus n. sp.

( Figs 38-40 )

TYPE MATERIAL.— Holotype: ovigerous 23 mm, REVES 2, stn 16 (MNHN-Pa 1876); paratypes: 1 15 mm (MNHN-Pa 1878), 1 15 mm (MNHN-Pa 1879), 1 ov. 17 mm (MNHN-Pa 1877), 1 12 mm and 1 ov. 19 mm (MNHN-Pa 586).

TYPE LOCALITY. — Seychelles. 5°35.9’S, 56°55.6’E, 46- 55 m.

ETYMOLOGY.— The name pyrrhonotus is derived from pyrrhos (Greek) = red, and notos (Greek) = back; in reference to the red colour observed on the back of several of the animals.

MATERIAL EXAMINED.— Kenya. 4°41’S, 54°24.5’E, 37 m, RV Manihine, cruise 336, stn 32, 7.II.1972, A. J. Bruce, 1 paratype 15 mm ( RMNH D 49576).

Seychelles. REVES 2, stn 11, 5°04.9’S, 55°53.2’E, dredge, 58 m, sand with shells (sable coquillier), 7.IX.1980, 1 paratype 15 mm (MNHN-Pa 1879). — Stn 16, 5°35.9’S, 56°55.6’E, trawl, 46-55 m, bottom maerl, 5.IX.1980, 1 ov. holotype 23 mm (MNHN-Pa 1876). — Stn 17, 5°42.7’S, 56°38.9’E, trawl, 55 m, bottom flat, maerl, 5.IX.1980, 1 paratype 15 mm (MNHN-Pa 1878). — Stn 19, 5°51.1’S, 56°20.5’E, trawl, bottom flat, of shelly sand with Pinna , 30-35 m, 5.IX.1980, 1 ov. paratype 17 mm (MNHN-Pa 1877).

Madagascar. RV Vauban, stn CH 72, 25°11.24’S, 47°14.7’E, trawl, 85-90 m, 3.III.1973, 1 ov. paratype 19 mm, 1 paratype 12 mm (MNHN-Pa 586).

South China Sea. Macclesfield Bank, 15°37.5’N, 114°12.2’E- 15°36.8’N, 114°15.4’E, 73-84 m, bottom with coral, RV Cape St. Mary, cruise 3/64, stn 48, trawl 169, 17.V.1964, A. J. Bruce, 1 paratype 20 mm ( RMNH D).

DISTRIBUTION AND HABITAT.— So far the species only known from the area of the western Indian Ocean and the South China Sea. It was found at depths of (30-)35-85(-90) m, on flat bottoms of shelly sand and maerl, or with coral.

DESCRIPTION

The rostrum is short and bears three dorsal tubercles at the anterior margin, the outer being largest. There is no rostral tooth. The pregastric tooth is rather well-developed and distinct, but smaller than the gastric tooth. Both are triangular in lateral view. Behind the pregastric tooth are some four or five tubercles. Behind the gastric tooth, tubercles are arranged in about three or four longitudinal curved rows of two or three tubercles each. The cardiac tooth is rather large and obscurely two-topped, it reaches slightly over the cervical groove. Behind it the tubercles are arranged more or less in two longitudinal rows of about four tubercles each, the posterior being the largest. At either side of the cardiac tooth there is a distinct rounded tubercle, that reaches slightly farther forward than the cardiac tooth itself. The branchial carina is bisected by the cervical groove; two tubercles lie slightly medially of the gap so is formed. The anterior branchial carina ends in two rather small teeth placed on the inner orbital margin; the anterior tooth is followed by a tubercle, so that sometimes the impression of three supraorbital teeth is given. Behind the posterior supraorbital tooth the anterior branchial carina shows a number of squamiform tubercles. The posterior branchial carina ends anteriorly in a strong blunt tooth, which is followed by five transverse rows of squamiform tubercles. There are many squamiform tubercles between the postrostral and branchial carinae. The intermediate row consists of four tubercles the anterior of which is largest and is situated right behind the cervical groove, it sometimes is subdivided. The lateral margin of the carapace behind the anterolateral angle consists of three small anterolateral, two rather large mediolateral and about eight posterolateral teeth. These teeth are arranged in a single uninterrupted line. The intercervical ridge is covered by about six tubercles, which completely fill the intercervical space. There are about three or four postorbital tubercles. The space between the branchial carina and the lateral margin of the carapace is completely filled with distinct squamiform tubercles. The marginal groove along the posterior margin of the carapace is distinct and filled with hairs. Behind it there is a transverse row of about 20 distinct flattened squamiform tubercles, and behind these one or two more irregular and less distinct rows of smaller tubercles. The posterior margin of the carapace is triangularly incised in the middle; the incision is rather wide with a blunt top. The squamiform tubercles of the carapace have a fringe of hair along the anterior and lateral margins.

The first abdominal somite has a complete transverse groove. The anterior half of the somite, before this groove is smooth; the posterior half shows about 20 longitudinal grooves which partly are branched and anastomosing; they do not reach the posterior margin of the somite. The abdominal somites I to IV have a median incision in the posterior margin, that of the fourth somite being rather indistinct. The anterior half of somites II to V have one or two rows of flattened tubercles along the posterior margin; thereby the median transverse groove of these somites has its anterior margin crenulated. The posterior half of somites II to V have the normal arborescent pattern of narrow grooves. The median area of these somites shows a smooth longitudinal carina, which, however, is not very highly elevated and never shows the high ridge seen in E. martensii n.comb. The carinae of somites II and III slightly higher than the others and in the male they are slightly higher than in the females; the carina of somite II is the most pronounced and has a longitudinal groove in its posterior part. The carinae are lobulated laterally. The pleura of the first somite are short and have the lateral margin divided into three or four lobes, the posterior of which is largest. The tips of pleura II to IV are bluntly rounded and not curved posteriorly. The margins of pleura II and III are crenulated or incised. The solid part of the telson is covered with squamiform tubercles but shows no sharp teeth. Of the two pairs of posterior teeth of this solid part, the inner shows as a narrow rounded lobe, the outer is very wide and quadrangular with a long posterior margin, having at most a tiny triangular denticle at the posterolateral angle.

The anterior margin of the antennular somite is almost straight or slightly curved with a median incision; a few squamiform tubercles are seen in the basal part of this somite.

The sixth (last) antennal segment ends in four or five broadly truncated distal teeth; there are two, aremore triangular, on the inner margin. The upper surface of the segment bears a few scattered tubercles. The fifth segment ends in a bluntly rounded top, and has a short dorsal carina that does not quite reach the top of the segment. The anterior margin of the fourth antennal segment bears a row of six or seven teeth, the inner of which usually is the largest, the outer the smallest. The outer margin of the segment has three or four large teeth (the apical tooth excluded). The oblique median carina is strong and ends in the apex; it bears flat tubercles, which are quite distinct in the basal part and become more indistinct distally. An erect blunt spinule is placed at the base of the carina. The outer half of the dorsal surface of the segment shows a curved row of rather large tubercles, the basal of which is largest. The inner half of this dorsal surface has scattered tubercles.

The epistome is not incised in the middle.

The first pereiopods are more robust and shorter than the following. The dactylus, propodus and carpus are naked. The merus shows a wide hairy groove in the lower part of the outer surface; sometimes a trace of a similar, but shorter groove can be seen in the distal upper part of that surface. The dactylus of the first leg is about two thirds as long as that of P.2, but is much wider. The dactylus of P.2 is longer than that of any of the other legs; the dactylus of P.3 is longer than that of P.4. In both sexes the dactylus of P.5 is shorter than that of P.4; in the female the fixed finger of the chela of P.5 is short and triangular and does not reach the middle of the dactylus, it has minute denticles on the cutting edge. P.2 has its segments naked except for the merus which has a row of short hairs on the dorsal margin and two faint hairy grooves on the outer surface. In P.3 the dactylus has a few short hairs in the basal part of the upper margin; the propodus has a dorsal fringe of short hairs and shows a wide and shallow longitudinal hairy groove in the lower part of the outer surface and a vague one in the upper half. The propodus is somewhat compressed. The carpus and the merus of P.3 have a fringe of short hairs on the dorsal margin; the merus furthermore has two wide and shallow longitudinal hairy grooves on the outer surface, while the lower surface also shows such a groove. The dactylus of both P.4 and P.5 have some hairs in the basal part, sometimes these are restricted to the dorsal surface, sometimes covering also the rest of the basal part. The propodus of P.4 has a scraggly row of short dorsal hairs, and traces of two longitudinal hairy grooves on the outer surface. The carpus of P.4 has a very small tuft of hairs at the anterior end of the dorsal margin; it also shows a trace of a longitudinal hairy groove on the outer surface. The merus is provided with a dorsal fringe of hairs, a distinct wide hairy groove on the outer surface and one on the lower surface. P.5 has traces of two wide grooves on the outer surface of the propodus and carpus; on the merus these grooves are more distinct and a dorsal fringe of hairs is present.

The anterior margin of the thoracic sternum is very shallowly U-shaped, it is almost transverse. The anterolateral teeth are short and hardly reach beyond the anterior margin. The margin shows a median incision, which is flanked by a pair of low and wide tubercles. The median part of the first sternite is sunken because a wide ridge extends along the anterior margin and merges laterally with a carina which extends from the anterolateral teeth back. This lateral carina shows a tooth some distance behind the tip of the anterolateral tooth. Some small tubercles are visible in the sunken part. The surface of the thoracic sternum shows a short pubescence and an indistinct median tubercle may be seen on somites III, IV and V. The posterior margin of the sternum is straight and carries a row of some small tubercles, which are most distinct laterally. Behind the base of the last pereiopod is a rounded carina; no teeth are present here.

The first pleopods of the male (placed on abdominal somite II) are elongate triangular, they are very slender and of about the same length; the exopod is slightly wider than the endopod. Pleopods 2 to 4 have the exopod broadly lamellar, the endopod is only a small bud.

Size

The two males examined have cl. 12 and 15 mm. The non-ovigerous females have cl. 15 to 20 mm, in ovigerous females cl. is 17 to 23 mm.

Colour

The colour of the holotype, when fresh, was described by Dr A. J. Bruce on the label with the material as follows: “Mottled patches of orange squames and inky plum coloured squames, with also scattered white squames. Pereiopods white, propodus and merus centrally purple, dactylus yellow. Abd[ominal somite] 6 and telson white, margin of uropods purple”. In the preserved specimens very little of the original colour pattern is noticeable. A few specimens, however, show a large irregular reddish spot in the median area of the posterior post-rostral carina.

REMARKS

The species differs from E. martensii n.comb., E. aesopius n.comb. and E. lewinsohni n.comb. by the relatively low carina on the second and third abdominal somite and from E. modestus n. comb. by the straight lateral margin of the carapace.

Figures

FIG. 38. — Eduarctus pyrrhonotus n. gen., n. sp., Seychelles, ovigerous holotype, carapace length 23 mm (MNHN-Pa 1876); A, dorsal view; B, lateral view.

FIG. 39. — Eduarctus pyrrhonotus n. gen., n. sp., Seychelles, ovigerous holotype carapace length 23 mm (MNHN-Pa 1876), thoracic sternum.

FIG. 40. — Eduarctus pyrrhonotus n. gen., n. sp., Madagascar, RV Vauban, stn CH 72, ovigerous paratype (MNHN-Pa 586); A-E, pereiopods 1 to 5. Scale bar: 2 mm.