Pseudanthessius pictus Humes 1977

Pseudanthessius pictus

TYPE MATERIAL.—4 from 10 echinoids, Parasalenia gratiosa A. Agassiz, in 1 m, eastern side of Isle Maître, near Noumea, New Caledonia, 22°20′35″S, 166°25′45″E, 8 June 1971. Holotype and two paratypes deposited in the National Museum of Natural History, Smithsonian Institution, Washington, D.C.; the remaining paratypic female (dissected) in the collection of the author.

OTHER SPECIMENS.—3 from 23 Parasalenia gratiosa, in tidal pools, Ricaudy Reef, near Noumea, 22°19′00″S, 166°26′44″E, 10 July 1971.

FEMALE.—Body (Figure 20a) with a relatively broad prosome. Length 1.10 mm (0.99–1.14 mm) and the greatest width 0.54 mm (0.53–0.56 mm), based on 7 specimens. Ratio of the length to the width of the prosome 1.36:1. Ratio of the length of prosome to that of the urosome 1.88:1. Segment of leg 1 separated from the head by a dorsal transverse furrow.

Segment of leg 5 (Figure 20b) 73 × 151. Genital segment in dorsal view 156 × 140, widest at its midregion and abruptly narrowed in its posterior fourth. Genital areas located dorsolaterally behind the widest part of the segment. Each genital area (Figure 20c) bearing two naked setae 30 and 14 and a small spiniform process. Three postgenital segments from anterior to posterior 42 × 95, 36 × 91, and 52 × 99. Anal segment with a few very small spinules on its posteroventral margin.

Caudal ramus (Figure 20d) 63 × 44, ratio 1.43:1. Outer lateral seta 95 and naked. Dorsal seta 42, outermost terminal seta 264, the innermost terminal seta 253, and the two median terminal setae 385 (outer) and 506 (inner); all these setae with lateral spinules.

Body surface with a few hairs (sensilla) and refractile points. A complex pattern of brown markings over the dorsal surface of the prosome (indicated by stippling in Figure 20a).

Egg sac (Figure 20e,f) variable in length, in the two ovigerous females seen 484 × 190 and 1023 × 242, containing numerous eggs about 70 in diameter.

Rostrum (Figure 20g) broad and weakly developed.

First antenna (Figure 21a) 345 long. Lengths of the seven segments: 44 (55 along the anterior margin), 113, 22, 50, 50, 31, and 24 respectively. Formula for the armature as in Pseudanthessius procurrens Humes, 1966. Long seta on the first segment 150 long. All setae naked.

Second antenna (Figure 21b) moderately slender, 400 long. Formula as in P. procurrens. Third segment with a sclerotized band on the posterior surface. Fourth segment 170 long along its outer side, 112 along its inner side, and 34 wide; bearing terminally two very unequal claws, one slender and only weakly unguiform, 34 long, the other massive and strongly unguiform, 68 along its axis; segment with five setules near the claws. All elements naked.

Labrum (Figure 21c) with two broad posteroventral lobes, the inner margin of each lobe indented and having a row of small teeth proximally and distally to the indentation. Mandible (Figure 21d) with a constricted basal area. Beyond the constriction an inner group of long slender spinules and an outer serrated fringe. Lash unusually short. Paragnath a small lobe. First maxilla (Figure 21e) with three naked setae. Second maxilla (Figure 21f) with a few refractile points on the inner surface of the large first segment. Second segment slender and elongated, bearing a finely barbed seta on its outer surface and produced to form a long sinuous lash with a row of very long slender spines along the convex edge grading into short spinules distally. Maxilliped (Figure 21g) with the first segment long and unarmed, the second segment somewhat shorter and bearing two naked setae, and the small third segment having a barbed seta and a naked seta, and attenuated and finely barbed distally.

Ventral area between the maxillipeds and the first pair of legs (Figure 21h) not protuberant.

Legs 1–4 (Figure 22a–d) segmented and armed as in other species of Pseudanthessius. Leg 4 with a very small inner coxal seta about 6 long. Exopod 156. Endopod 81 × 16, with a row of hairs proximally along the outer side. Two terminal spines 39 and 55, apparently with smooth rather than barbed fringes. Ratio between the spines 1.41:1.

Leg 5 (Figure 22e) with a slender finely barbed spine 29, a smooth seta 60, and a smooth dorsal seta (held erect and not measurable).

Leg 6 represented by the two setae on the genital area (Figure 20c).

Living specimens in transmitted light pale brown, with brown markings on the dorsal surface of the prosome. (These brown markings remain in specimens cleared in lactic acid). Eye red, the egg sacs opaque gray.

MALE.—Unknown.

ETYMOLOGY.—The specific name pictus (Latin, = painted) alludes to the elaborate brown markings on the dorsal surface of the prosome.

COMPARISON WITH RELATED SPECIES.—A survey of the females of the several species of Pseudanthessius shows that all but ten have a caudal ramus that is at least 2:1, and thereby can be quickly distinguished from the new species. In seven of the 10 remaining species where the labrum has been described the inner margins of the two lobes are smooth, not indented and dentate as in P. pictus. These seven species are: P. pectinifer Stock, Humes, and Gooding, 1963; P. pusillus Humes, 1969; P. minor Stock, 1967; P. major Stock, 1967; P. madrasensis Reddiah, 1968; P. angularis Humes and Ho, 1970; and P. rostellatus Humes and Ho, 1970. The remaining three species from southeastern India may be separated from P. pictus on other grounds. In P. minutus Reddiah, 1968, the cephalosome is wider, the contour of the genital segment is different, the caudal rami appear to be shorter, and the claws on the second antenna are subequal. In P. brevicauda Ummerkutty, 1966, the caudal ramus is nearly as long as broad, the claws on the second antenna are slender and subequal, and the teeth on the lash of the second maxilla are strong. In P. anormalus Ummerkutty, 1966, the caudal rami are hardly as long as broad, the fourth segment of the second antenna is relatively shorter, and the lash of the second maxilla apparently lacks the crest of long spines seen in P. pictus.