Abyssorchomene abyssorum (Stebbing 1888)

Orchomene (Abyssorchomene) abyssorum Stebbing

Orchomene abyssorum Stebbing, 1888:676–679, pl. 21; 1906:84.—Chevreux, 1900:23–24; 1903:92; 1905:7; 1935:59–60.—Stephensen, 1925:125.—Nicholls, 1938:35–36, fig. 15.—Dahl, 1954:282.—Birstein and Vinogradov, 1960:188–189, fig. 8; 1962:44; 1964:164.

?Not Orchomenopsis chilensis forma abyssorum Schellenberg, 1926a:291–292, fig.27.

?Orchomenella abyssorum K.H. Barnard, 1932:69, figs. 27b, 28.—?Nicholls, 1938:35–36, fig. 15.

DIAGNOSIS.—(Based on new material.) Lateral cephalic lobes broadly rounded. Eyes long, lunate, colorless in alcohol, glandular, ommatidia not evident, about 40 percent as high as head. Peduncle of antenna 1 barely keeled. Epistome flat and and upper lip rounded anteriorly, projecting equally, epistome weakly dominant in size. Each mandible with 3 rakers, molar of medium size, trituration surface of medium extent, with 4 crater-pits, hairy process attached medial to molar; article 1 of palp very short. Inner plate of maxilliped with mediodistal extension.

Carpus of gnathopod 1 short, posterior lobe narrow, well exceeding posterior tangential line between merus and propodus, guarding propodus, lobe rounded apically, propodus 1.75 times as long as carpus, weakly tapering, posterior margin weakly sinuate, lacking tubercle, palm transverse, convex, almost chelate, dactyl barely overriding palm. Carpus of gnathopod 2 not greatly elongate, about 0.40 times as wide as long, propodus about 0.44 times as long as carpus, 50 percent as wide as long, much narrower than carpus, palm short, chelate, not lunate, dactyl short and covering 100 percent of palmar edge, palm defined by thin spinule and bearing weak inner setal basket.

Coxa 5 with weak posterior lobe exceeding anterior ventral tangent. Article 2 of pereopods 5–7 with sparse, weak posterior setule-notches. Article 2 of pereopod 5 of normal breadth and dimensions. Article 4 of pereopod 5 weakly expanded and bearing posterior few posterior setae, of pereopods 6–7 narrower and with short posterior spines only; article 6 of pereopods 5–7 much longer and slightly narrower than article 5.

Epimeron 3 weakly sinuous posteriorly, produced into weak blunt tooth posteroventrally, smooth. Dorsal process of urosomite 1 hood-shaped, weakly overvaulting urosomite 2. Female uropod 3 sparsely setose on medial margins of both rami, outer non-apical margins naked. Telson cleft 50 percent of its length.

DESCRIPTION.—Male “s”: See illustrations. Right antenna 2 with only one calceolus present, on article 4 of flagellum; see left antenna 2 illustrated. Upper lip with asymmetrical weakly bifid anterior lobe as shown for O. distinctus. Left lacinia mobilis with 2 apical prongs. Weakly plaited gills present on coxae 2–7, those of coxae 5–6 with terete accessory lobe. Male penes extremely small and located centrally on sternite 7. Oostegites unknown, female not collected.

ILLUSTRATIONS.—Uropod 3 and telson equally magnified, uropod 2 less, uropod 1 even less. Maxillae 1–2 not evenly magnified. Straw-like publescence on enlargement of inner plate on maxilliped reduced in illustratioon. Enlargement for gnathopod 2 more magnified than for gnathopod 1; note on propodus apex of gnathopod 2 medial side with giant complex setae, lateral side with thin simple setae. Dactyl of pereopods 3–4 like O. abyssorum illustration.

MATERIAL.—Illustrated, SIO Station 882, Galapagos Vents, 00°47.9′N, 86°09.2′W, 23 Jan 1979,2491 m, mussel bed, clam bucket residue, one male “s” 6.41 mm.

DISTRIBUTION.—Type locality, off Buenos Aires; confirmed also from north of New Zealand and from the Galapagos Vent area, 2491 m; depths generally 550 to 4330 m; if other antarctic records prove to be valid, depths in Antarctica may be much shallower; and individuals there may be very abundant.


Schisturella Norman

Schisturella Norman, 1900:208 [Tryphosa putchra Hansen, 1887, monotypy).—J.L. Barnard, 1967:71 [key].

Pseudonesimus Chevreux, 1926:3 [Pseudonesimus abyssi Chevreux, 1926, monotypy).

Thrombasia J.L. Barnard, 1966a:72 [Thrombasia tracalero J.L. Barnard, 1966a, original designation).

DIAGNOSIS.—Mouthparts forming quadrate bundle. Labrum and epistome differentially produced, prominent, separate, labrum strongly dominant in projection, blunt Incisor ordinary, molar weakly triturative, large, also setulose; palp attached opposite molar. Inner plate of maxilla 1 weakly (2) setose; outer plate with 7 spines; palp triturative, large. Inner and outer plates of maxilliped well developed, palp strongly exceeding outer plate, dactyl well developed.

Coxa 1 strongly shortened and partly covered by coxa 2, tapering or truncate.

Gnathopod 1 short, nearly simple (type) or strongly subchelate, palm oblique to transverse, articles 5 and 6 subequal, or 6 shorter than 5, dactyl large; article 6 of gnathopod 2 greatly shorter than article 5, ordinary, propodus minutely chelate.

Inner ramus of uropod 2 with large notch. Uropod 3 almost aequiramous, ordinary, peduncle ordinary, outer ramus 2-articulate. Telson elongate (type) or short, weakly to deeply (type) cleft

ADDITIONAL CHARACTERS.—Inner plate of maxilla 2 medially setose, one seta enlarged, apex of outer plate of maxilliped with 2–3 spines (versus 5–7 in Parsehisturella).

SEXUAL DIMORPHISM.—Male flagellum of antennae 1–2 elongate and calceoliferus, female antenna 1 with calceoli.

VARIABLES.—Antenna 1 apex of flagellum article 1 with large spine (S. pulchra); mandibular molar poorly triturative and well setulose (S. tracalero; S. totorame), palp article 3 very short (S. zopa) (S. grabensis); coxa 1 variable, short or long, quadrate or triangular, but coxa 1 also slightly elongate (S. tracalero); gnathopod 1 simple (type), subchelate, palm oblique (S. adversicola, S. rotundatus, S. dorotheae), almost simple (S. cocula), subchelate, palm transverse (S. zopa; S. robusta; S. abyssi); telson deeply cleft (type, etc.), cleft 1/3 (S. adversicola, etc.)

RELATIONSHIP.—Metambasia differing from Schisturella and Ambasiopsis primarily in complete loss of palm in gnathopod 1.

From Ambasiopsis in the strong notch on the inner ramus of uropod 2, stronger medial setation on maxilla 2, and lack of major dorsal hump or tooth on urosomite 1. The type species of Ambasiopsis has no apical spines on the outer plates of the maxillipeds. The type species of Schisturella has many distal spines. Usually Ambasiopsis has a stout gnathopod 1 and Schisturella has a thin gnathopod 1.

From Hirondellea in smaller head, sharper ocular lobe, dominance of labrum, and lack of inner serration on palp of maxilla 1.

From Aristiopsis in lacking hump on epistome and absence of lobe on carpus of gnathopod 1.

From Gronella groenlandica in dominance of upper lip (not dominance of epistome), unlobed carpus of gnathopod 1 and more distally placed mandibular palp.

REMOVAL.—Schisturella galatheae Dahl (1959) transferred to Galathella Barnard and Karaman (1987).

SPECIES.

S. abyssi (Chevreux, 1926, 1935).—J.L. Barnard, 1967.—S. a. tasmanensis J.L. Barnard, 1961 [420A]

S. adversicola (K.H. Barnard, 1925).—Schellenberg, 1926b.—J.L. Bamard, 1962 [735BA]

S. cocula J.L. Bamard, 1966a [372]

S. dorotheae (Hurley, 1963) [373]

S. grabensis J.L. Bamard, 1967 [309B]

S. pulchra (Hansen, 1888).—Shoemaker, 1930a.—Schellenberg, 1935.—Gurjanova, 1962.—Sekiguchi and Yamaguchi, 1983 [200 + AB]

S. robustus (J.L. Bamard, 1961).—S. r. cedrosiana J.L. Bamard, 1967 [715A + 309B]

S. rotundatus (K.H. Bamard, 1926).—J.L. Bamard, 1962, 1967 [735BA]

S. totorami J.L. Bamard, 1967 [373]

S. tracalero J.L. Bamard, 1966a [373]

S. zopa J.L. Bamard, 1966a [310B]

DISTRIBUTION.—Marine, cosmopolitan cold water, thus tropically submergent, 75-4961 m, comes to baited traps, 11 species.