Paradexamine alkoomie J. L. Barnard 1972

Paradexamine alkoomie

DESCRIPTION (of female-like specimens).—Lateral cephalic lobe rounded, thick, head with distinct anteroventral definition at base of antenna 2, rostrum medium to small and weakly pointed; article 1 of antenna 1 lacking ventral protrusion, bearing 3 long spines in tandem, article 2 about 1.5 times as long as article 1, apically simple and bearing several long ventral spines, flagellum about 1.25 to 2.0 times as long as peduncle; flagellum of antenna 2 about 1.3 to 1.5 times as long as peduncle, peduncular articles 4-5 with many long spines, article 3 especially produced ventrally; mandibles with large spines, 2 on right, 3 on left, molar heavily triturative, accessory bulges numerous and blunt, both molars with ordinary setae, and 1 ragged seta; outer lobe of lower lip with 5-6 medium cones, mandibular lobes tapering and apically curled; palp of maxilla 1 small, shorter than outer plate, narrow, bearing 2 apical setae and rounded cone, inner plate thin, naked; plates of maxilla 2 narrow, appressed, curved inner plates reaching about 75 + percent along outer, inner with subtruncate apex and 4 setae; inner plates of maxilliped vestigial, each bearing 2 spinules, outer plate large, bearing bifid spines, palp thin and small, scarcely exceeding outer plate, palp article 4 of medium elongation: coxa 1 with slight anterior bulge near mark 65, below that tapering and bearing anterior setae below bulge, coxae 1-3 lacking posterior spines, coxae otherwise of ordinary dimensions, well setose ventrally, 5-6 with thin ventral spines; gnathopods large, elongate, gnathopod 1 with article 6 about 0.82 times as long as article 5, about 0.72 times on gnathopod 2, fifth articles of medium width, expanding apically, palms oblique but weakly so, extremely finely castellate, dactyls smooth proximal to main inner tooth, palmar faces on gnathopod 1 with oblique row of 2 pectinate and 3 simple setae, anteriorly with 2 sets of 4 and 3 setae, on gnathopod 2 oblique row with 1-2 pectinate and 2-3 simple (total 3-5) setae, anterior sets with 3 and 1 setae each; pereopods 1-5 very thin distally, spines generally sharp, but spine sets on articles 4-5 with several sausage-shaped, tumid spines with granulated matrix, appearing finely spotted, ratio of articles 4-7 on pereopods 1-2 about 18:21:24:12; article 2 of pereopod 3 of medium breadth, with regular posteroventral lobe; article 2 of pereopod 4 circulopyriform, posteroventral lobe well developed but bearing only setules; article 2 of pereopod 5 ovatopyriform, posteroventral region with large spinose lobe, posterior margin deeply serrate, ratio of articles 4-7 about 20:38:26:11; pleonal epimera 1-2 with lateral ridge, epimeron 1 with tiny posteroventral tooth, epimera 2-3 with medium to long tooth, epimeron 3 especially serrate posteriorly and bearing rudimentary setae, epimeron 1 with 1-2 anteroventral spine (s) or 1 seta instead of spine, epimeron 2 with 5 ventral spines, epimeron 3 with 6 ventral spines, no facial spines; pereonite 7 with 3 lobular teeth dorsally; pleonites 1-4 each with 3 sharp teeth, dorsomiddle tooth low, pleonite 4 with spine on lateral ridge, pleonites 5-6 (fused), with 2 short spines in tandem on each side; dorsal margin of peduncle of uropod 1 evenly spinose or almost so, small apparent gap near apex according to interpretation, lateral base of peduncle with 2 spines; uropod 3 far exceeding apex of telson, rami of uropod 3 bearing only spines; telson flat, apices of medium breadth, each with about 7 serrations and 1 small apicolateral spine, lateral margins with 5-6 medium spines in tandem, none paired; cuticle of epimera, middle coxae, article 2 of pereopod 3 covered with weak crescent slits, setules extremely rare.

VARIATIONS AND ILLUSTRATIONS. — Posterior spines on article 6 of pereopods 1-2 closely crowded toward apex; flagella of antennae on view of head drawn mainly as straight lines to show true lengths; illustration of gnathopod 2 from medial surface converted from left-sided appendage; the 4.1 mm specimen from Shepherd 30 has both penial processes and brood plates but otherwise retains the apparently normal female characteristics, though it is highly unique in the materials of Paradexamine from Australia in having sternal teeth (Figure 19vn) especially on pereonites 3-6; in the figure, pereonite 7 has 1 penial process, shaped like a boomerang, hanging ventrad.

HOLOTYPE. — SAM, female (ovigerous), 4.9 mm.

TYPE-LOCALITY. — Shepherd 30, Pearson Islands, South Australia, station B, 1540 feet, algae, 8 January 1969.

RELATIONSHIP. — This species and P. narluke may be synonymous; the single male of P. narluke is small and comes from Western Australia, whereas P. alkoomie is based on 5 large (relatively one-third larger) specimens from South Australia, none of which is an ordinary male; hence, the differences listed below may be those associated with sexual and size characteristics. Paradexamine alkoomie differs from P. narluke in the absence of facial spines on epimeron 2, the apically crowded posterior spines on article 6 of pereopods 1-2, the presence of a distinct anterior bulge on coxa 1, with several setae occurring anteriorly, the even smaller inner plate of the maxilliped, the deeper lobe on article 2 of pereopod 5, the broader and more strongly serrate telsonic lobes, the presence of side teeth on pleonite 1, and the presence of 3 large rounded teeth on pereonite 7. Paradexamine narluke has the rudiments of a bulge on coxa 1 seen in P. alkoomie, but the first two differences cited above appear to confirm that genetic difference occurs between the two groups of specimens.

Paradexamine alkoomie is also related to P. windarra in approximately the same way that P. narluke is, but P. windarra differs far more from both species than do either of the latter from each other. Paradexamine windarra has a heavy spine on coxa 2, broad lobes on maxilla 2, much stouter and shorter gnathopods, no indication of an anterior bulge on coxa 1, and many setae above the halfway mark on the anterior margin, straight, blunt mandibular lobes on the lower lip, no cuticular slits, a definite gap in the spination on uropod 1, poorly projecting uropod 3, and blunt article 3 on antenna 2.

Paradexamine alkoomie also resembles P. lanacoura sufficiently to cause some confusion in routine identifications, but P. alkoomie differs in the shorter, almost blunt rostrum, the absence of a protrusion on article 1 of antenna 1 in females, the long flagellum of antenna 2 in females, the anterior setae and bulge of coxa 1, the absence of posterior spines on coxae 2-3, the presence of cuticular crescents, and the rudimentary setae on the posterior margin of epimeron 3.

MATERIAL. — Shepherd 13 (1), 30 (3), 52 (1).

DISTRIBUTION. — South Australia, sublittoral in epifauna.