Allorchestes compressa Dana 1852

Allorchestes compressa subspecies V

DIAGNOSIS.—Hand of male gnathopod 1 and female gnathopods 1–2 apically tumid, dactyl of gnathopod 1 lacking outer facial ridges; article 2 of pereopod 5 evenly rounded ventrally; epimera 2–3 with medium strong posteroventral cusp; flagellum of female antenna 2 about 1.8 times as long as articles 4–5 of peduncle together.

MATERIAL.—Port Phillip 73 (50).

Allorchestes compressa Dana

Allorchestes compressa Dana, 1852:205.

Allorchestes australis Dana, 1852:206; 1853:892, pl. 60: fig. 7.

Allorchestes gaimardii Dana, 1853:884, pl. 60: fig. 1.

Aspidophoreia diemenensis Haswell, 1880a: 101–102, pl. 6:fig. 2.

Allorchestes compressus.—Stebbing, 1899:410–412, pl. 33B; 1906:581–582.—?Stephensen, 1927:351; 1938:261.

DIAGNOSIS.—Mature male gnathopod 1 with hammer-shaped hand protruding at palmar corner, dactyl fitting palm or slightly shortened, strongly striate, not heavily swollen, with simple apical nail, medial face of hand near palmar corner with up to seven medium-to-small defining spines in group, no spine discontiguous; posteroventral protrusions of epimera of medium extent to obsolete; body dorsally smooth; cuticle with complex alae surrounding bulbar setules; spines of pereopods 3–5 sharp, slender; inner ramus of uropod 1 with two dorsal spines.

Allorchestes compressa subspecies W

DIAGNOSIS.—Hand of male gnathopod 1 and female gnathopods not apically tumid, dactyl of male gnathopod 1 wtih numerous outer facial ridges; article 2 of pereopod 5 asymmetrically rounded ventrally; epimeron 3 sharply quadrate posteroventraly, epimeron 2 with extremely weak posteroventral tooth; flagellum of female antenna 2 about 1.25 times as long as articles 4–5 of peduncle together.

MATERIAL.—JLB Australia 5 (1), 7 (7.5 × 105 specimens, examined 50), 8 (3); WAM, Pt. Peron, 25 November 1946 (4); Cottesloe, February 1925 (36); North Beach, 6 June 1927 (23); Twilight Cove, out of washed up sponge, Mrs. Loney, 5 June 1966 (40+).

GENERAL DESCRIPTION OF MALE.—Eyes subcircular, black; lateral cephalic lobe extended, broad and obliquely truncate; antenna 1 extended to apex of peduncle on antenna 2, flagellum about 1.5 times as long as peduncle, aesthestascs weak; antenna 2 of medium length, articles 3–5 of peduncle stout, poorly armed laterally, flagellum thick, about as long as peduncle, base conjoint in terminal adults; margins of upper lip largely papillate; palp of maxilla 1 in typical subspecies longer and with longer apical spine than in A. compressa w; palp article 3 of maxilliped with one main apical row of setae, article 4 with one main apical spine; posterior acclivities of anterior coxae weak, softly rounded; article 2 of gnathopod 1 apically simple, lacking vertical ridge on either face, article 4 unproduced, lobe of article 5 shallow, broad, set proximally, palm smooth (minutely), transverse, defined by one lateral spine and two or three large mediofacial spines, hand with two or three groups of weak posterior setae; gnathopod 2 with anterodistal process on article 2 in A.c. w but not A.c. v, anterior lobe on article 3 stronger in A.c. w than A.c v, palm about 1.5 times as long as posterior margin of hand, palm lined with short spines, unsculptured, posterior margin of hand poorly setose, palm defined by spine group, dactyl ordinary, apex inserted into palmar pocket; dactyls of pereopods with apical nail, weak setule near base of nail, inner margin of dactyl weakly castellate, locking spine one in number, simple, large, blunt, first pair of marginal spines on article 6 very close to locking spine; peduncle of uropod 1 with two or three basolateral spines, long gap, then small apicolateral spine, apicomedial spine small, outer rami of uropods 1–2 without dorsomarginal spines, inner rami with dorsal spines; peduncle of uropod 3 expanded from lateral view, bearing two apical spines, ramus bearing two or three short apical spines (A.c. w) or one or two spines and up to three setae (A.c. v); telson almost sharply rectangular, broader than long, cleft halfway; cuticle bearing numerous alate pits with short setule, pits extremely small.

FEMALE.—Antenna 1 like that of male but antenna 2 short, peduncle not strongly thickened, base of flagellum not conjoint; article 2 of gnathopod 1 with apicofacial ridge; lobe of article 5 weaker and sharper than in male, hand nearly parachelate, dactyl more slender than in male and lacking ridges (but bearing circular setule pits as in male); gnathopod 2 resembling gnathopod 1 but article 4 bluntly extended, lobe of article 5 large and long, hand broad; uropod 3 generally with three peduncular spines; posterior margins of lobes on telson slightly excavate.

VARIATIONS.—The largest male of A.c. v is 16 mm long, of A.c. w, 10.3 mm. In the large males of A.c. v the subsidiary piece on the right mandibular lacinia mobilis is less prominent than in males the same maximum size of A.c. w. The left mandible of those large males has three additional rudimentary spines besides the regular three and on the right one extra rudimentary spine is present. In A.c. v, the peduncle of uropod 1 has up to four subbasal spines, and the rami’ of uropods 1 and 2 have up to three and two dorsal spines, respectively. The smallest specimen at hand of A.c. v is 5.7 mm so that knowledge of juveniles is lacking.

The largest male of A.c. w at hand, 10.3 mm long from Pt. Peron, 25 November 1946, has a widely expanded hand, the dactyl much shorter than the palm and lacking outer dactylar ridges as in subspecies v; but other smaller males of that sample have the ridges normal to subspecies w.

On pereopods 3–5 the first pair of spines next to the locking spine is fully developed and in large adults one or two setae occur on either side of the spines; on pereopods 1–2 the first armament next to the locking spine is a single spine with one or two setae on either side.

Articles 2 and 3 of male gnathopod 2 have no mediofacial lobes, only laterofacial lobes. Pereopod 2 is slightly shorter than pereopod 1. Female gnathopod 1 has only one posterior seta on article 2 and article 4 is weakly fuzzy on the outer margin. The medial face of the peduncle on uropod 3 bears weak spinules, more on the female than on the male. The fuzz on the outer proximal setule of the pereopodal dactyls may be blue-green algae. The cuticular pits are alate mainly on the coxae and are of irregular or subcircular form in other places. They may be antecedent to those pits so prominently developed on species of Ceinidae.

Juveniles of A.c. w about 2.6 mm long have five flagellar articles on antenna 1, six on antenna 2, with the first article elongate on antenna 2; eyes dark; acclivities on coxae 1–3 rudimentary; peduncle of uropod 3 with only one spine and the inner rami of uropods 1–2 with only one dorsal spine. Article 6 of gnathopod 1 is relatively elongate compared with adults, article 2 has no midposterior setae; article 2 on gnathopod 2 has two posterior setae in tandem. Otherwise, juveniles are generally recognizable as this species.

In the few available specimens of A.c. v the hand of gnathopod 1 has a basal sleeve extending the hand at an angle not occurring in A.c. w; whether this is a characteristic of living specimens is unknown.

DISTRIBUTION.—Jervis Bay, Western Australia, south and east to Tasmania, north to Illawarry, New South Wales; ?Campbell Island; ?Auckland Islands.

Allorchestes compressa is a species of amphipod in the family Dogielinotidae. It is found around the coast of Australia from Western Australia to Tasmania and east to Illawarra, New South Wales.