Paradexamine marlie J. L. Barnard 1972

Paradexamine marlie

DESCRIPTION (of female). — Lateral cephalic lobe with sharp anterior cusp, head lacking anteroventral definition at base of antenna 2, rostrum very short, blunt; article 1 of antenna 1 with ventral spines thin and arranged in 2 groups of 3 each, article 2 about 1.15-1.33 times as long as article 1, apically simple and bearing a set of spines ventroproximally, flagellum 3.5 times as long as peduncle; flagellum of antenna 2 about 1.7 times as long as peduncle, multiarticulate; mandibles lacking spines, molar with regular setae on right, nearly smooth except for castellations, only ragged seta on left, accessory molar bulge distinct; outer lobe of lower lip bearing 1 medium-to-long cone, 1 short cone, mandibular lobes very thin, upturned; palp of maxilla 1 large, of normal breadth, extending beyond apex of outer plate, bearing apical and medial setae and 2 weak-to-moderate apical cones (differing on left-right); inner plate of normal size, bearing 1 seta; inner plate of maxilla 2 narrower than outer, both appressed, inner with apex very oblique, outer weakly curved, inner reaching 70 percent along outer, outer plate with 2 subproximal setae on inner face; inner plate of maxilliped of medium size, bearing about 3 large and 1 small apical setae and 2-3 facial setae, outer plate of ordinary size, rather thin, spines small, simple, palp robust, slightly exceeding outer plate; coxa 1 expanded at distal mark 67, naked anteriorly, weakly setose ventrally and scarcely serrate, coxae 2-3 rectangular, weakly setose ventrally, bearing one midposterior spine, coxae 5-6 with thin ventral spines; gnathopod 1 with article 6 about 0.7-0.8 times as long as 5, on gnathopod 2 about 0.66 times, gnathopods moderately thin, palms oblique, medial faces of hands with 4-6 thin, weakly pectinate setae, gnathopod 1 with 3 rows of anterofacial setae, gnathopod 2 with 2-3 single setae, dactyls bearing very minute pectinations proximal to inner tooth, palms regularly and deeply serrate; pereopods 1-5 thin, with sharp spines except for a few weakly blunt spines on article 6 of pereopods 1-2, ratio of articles 4-7 on pereopods 1-2 about 17:14:18:11; article 2 of pereopod 3 of ordinary stoutness, posteroventral lobe broad and deep, article 2 of pereopod 4 pyriform, posteroventral lobe obsolescent but spinose; article 2 of pereopod 5 thinly pyriform, posterior margin weakly serrate, not spinose, article 5 elongate, ratio of articles 4-7 about 21:32:24:13; pleonal epimera 1-2 with lateral ridge, small sharp tooth on 1, medium sharp on 2, epimeron 3 with medium basally thick tooth, posterior margins of epimera smooth, epimeron 1 with bundle of 4 spines in facial row, epimeron 2 with facial row of 8-10 spines, epimeron 3 with posterofacial row of 5 spines, then anteriorly groups of 2-3, 1, and 1 spines; pleonite 1 dorsally smooth, pleonites 2-3 with sharp dorsal tooth and sharp tooth on ridge of each side, pleonite 4 with sharp, subprostrate dorsal tooth, no lateral tooth but with spine on lateral ridge, pleonites 5-6 (fused) with 2 dorsolateral spines on each side; dorsal margin of peduncle on uropod 1 evenly spinose; rami of uropod 3 lacking setae; telson with long high crest on each lobe, apices broad, with about 8-11 serrations but about 3 of them grouped as bifid, 1 small spine in notch space, lateral margins of each lobe with about 5-6 medium-to-long spines; cuticle of posterior body segments smooth.

MALE. — Eyes enlarged; antennal peduncles with numerous marginal setule groups but spines of pleonites 4-6 half as long as on female; gnathopodal dactyls usually lacking long pectinae, weakly developed in young males; fully adult male with tooth on epimeron 3 obsolescent; inner plate of maxilla 2 longer than in female.

HOLOTYPE. — WAM, female, 3.3 mm.

TYPE-LOCALITY. — JLB Australia 2, Jervois Bay, Cockburn Sound, Western Australia, on groin 1.6 miles southeast of Woodman Point, 1 meter, algae on rocks, collected by Dr. Barry R. Wilson, 10 June 1968.

RELATIONSHIP. — The taxonomic status and relationships of this species are complicated by enigmas regarding Sheard’s (1938) lectotypes of P. pacifica from New Zealand. Sheard showed P. pacifica with no teeth on pleonite 1, no cones on the lower lip, and an elongate article 2 of female antenna 1. The first and last characters are typical of this new Australian species, but J. L. Barnard (in press), and herein, studied collections of P. pacifica from New Zealand and found 2 cones on each outer lobe of the lower lip. Stephensen (1927) also had a Paradexamine, like Sheard’s lectotype, from Auckland and the Campbell Islands, with no teeth on pleonite 1 and an elongate article 2 of antenna 1; the lower lip was not described.

Paradexamine marlie differs from P. pacifica in the absence of mandibular spines, the smaller inner plate of the maxilliped, the presence of 1 strong posterior spine on coxae 2-3, and the singularity of the distal spine position on the peduncle of uropod 3.

This species, being distinguished by the mandible, could be classified as a race of P. pacifica in view of Sheard’s lectotypes, but it is a distinct species in comparison to P. houtete, differing from it in pleonite 1, mandible, maxilla 2, article 2 of pereopod 3, antenna 1 of female, and telson. Its racial rank is also confuted by the presence of a “sibling-cryptic” species associated sympatrically with it. That species, P. linga, is characterized by the long spines on the mandibles and by the absence of a seta on the inner plate of maxilla 1. The characters of mandible and cephalic lobe have been observed in small juveniles, indicating that the two morphs are not simply post-ephebic phenotypes; they might remain generalized phenotypes except for the fact that the condition of the mandibular spines has been found to be a good specific character in other species of this genus.

The general aspect of P. marlie in resembling P. pacifica has not been figured because the figures of Sheard (1938) are comparable. This species has a pleon like P. pacifica in the absence of teeth on pleonite 1, the head and antennae are generally similar, with male antenna 2 and article 2 of antenna 1 being elongate normally, and the mandibular and inner lobes of the lower lip are similar, but the palp of maxilla 1 is slightly thinner and shorter in the Australian species (Sheard’s figures differ from specimens of P. pacifica in this regard), and the gnathopods and coxae 1-4 and 7, the accessory flagellum, and the upper lip are similar.

Paradexamine marlie differs from P. moorhousei, a species definitely known in the male sex only, in the presence of spines on pleonites 5-6, in the short maxillipedal palp, which in P. moorhousei extends well beyond the outer plate, in the presence of cones on the lower lip, and in the much stouter gnathopods.

Paradexamine marlie is very close to P. barnardi, especially in the absence of spines on the mandible. Sheard wrote that only 1 cone occurred on each lobe of the lower lip, but the small cones can easily be overlooked, confused with setules, or, in shriveled lower lips, they are often not observed. Paradexamine barnardi is based only on males from New Zealand, which are neritic and possibly more advanced in their development than those remaining on the bottom. Males of P. marlie differ from those of P. barnardi in the normally extended maxillipedal palp, which in P. barnardi is shortened, and in the sparsity of setae in the main setal row of the gnathopodal hand faces, which in P. barnardi has 10 setae as opposed to 6 in P. marlie. Several characters of P. barnardi, plus its female, have not been clarified, including the questions of whether pleonites 5-6 have 1 or 2 spines on each side, whether pleonite 4 has a spine on each side, what are the characters of spines on coxae 2-3, and what are the details of pereopods 1-5. K. H. Barnard (1930) wrote that P. barnardi has dorsal and lateral teeth on pleonite 1, a characteristic that differs from both P. marlie and P. linga.

Paradexamine moorhousei is another species from Australia based on males (presumably, though Sheard called them females). Paradexamine marlie resembles P. moorhousei in the lack of mandibular spines, the seta on the inner plate of maxilla 1, the shape of the first maxillary palp, and generally maxilla 2, but P. moorhousei has a slightly more elongate maxillipedal palp, a broader article 2 of pereopod 5, and extremely thin gnathopods, with article 5 of gnathopod 2 very elongate. Perhaps P. moorhousei is an advanced male of P. marlie, but Sheard has not stated the details of spination on urosomites 1-3 nor clarified the other following characters: pereopods 1-4, coxae 1-4, mandibular lobes of lower lip, telsonic apices, epimeral spination.

MATERIAL. — JLB Australia 2 (11), 4 (1).

DISTRIBUTION. — Southwestern Australia, intertidal and sublittoral.