Archaeoscina danae, Zeidler, Wolfgang, 2006

Zeidler, Wolfgang, 2006, A review of the hyperiidean amphipod superfamily Archaeoscinoidea Vinogradov, Volkov & Semenova, 1982 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 1125, pp. 1-37 : 14-19

Archaeoscina danae sp. nov. ( Figs 4 & 5 )

Material examined (6 females, 2 males)

Holotype. Female, 7.7 mm long ventrally, with pereon inflated to 7.0 mm long by 5.8 mm deep ( ZMUC CRU­ 4359); northeast Pacific, Gulf of Panama [6°48N, 80°33W]; collected by Dana (Stn. 1208 XIV), 3100 mw, 16 Jan. 1922.

Allotype. Male, 4.2 mm ( ZMUC CRU­ 4360); Banda Sea, south of Amboina [5°52S, 131°14E]; collected by Dana (Stn. 3676 VII), 5000 mw, 23 March 1929.

Paratypes. 1. Juvenile female, about 3.0 mm (ZMUC CRU­4361); South Atlantic near Gulf of Guinea [7°34S, 8°48W]; collected by Dana (Stn. 3998 IX), 3000 mw, 1 March 1930. 2. Female, about 7.0 mm long ventrally with pereon inflated to 5.9 mm long by 5.1 mm deep, and 3, two juvenile females, both about 3.7 mm (ZMUC CRU­4362); eastern north Atlantic, off Sierra Leone [8°26’N, 15°11’W]; collected by Dana (Stn. 4003 IV), 3000 mw, 9 March 1930. 4. Juvenile female, 4.7 mm (USNM 1068939); South Atlantic, south of Cape Verde Islands [8°05’– 8°04’S, 25°24’– 25°40’W]; collected by USNS Gilliss (USN00 Stn. 6–17), IKMWT 720 m, 10 Feb. 1969.

Other material. Male, about 2.0 mm ( USNM 1068940); North Atlantic, off Portugal; collected by Discovery II, 1959? (According to available USNM records)

Diagnosis

Largest female recorded with body length of about 8.0 mm; males exceed 4.0 mm. Pleon length in males about 0.8x pereon. Antennae 1 as long as head and first three pereonites in males; callynophore length about 2.0x peduncle in females, 4.0x peduncle in males; terminal article similar in length to preceding one, conical in female, rounded in male. Antennae 2 of females about 0.7x length A1; the two terminal articles at least twice as long as wide; A2 incomplete for known male specimens. Mandibular palp; length third article about twice first two articles combined. Pereopods 3 & 4 similar in length; the longest pereopods in females, about 1.2x P5; slightly shorter than P 5 in males. Pereopod 5 the longest pereopod in males. Pereopod 6; length slightly more than 0.8x P5. Pereopod 7; length slightly more than 0.7x P5. Merus length of P3–5 about 0.8x carpus; of P6 & 7 about equal in length to carpus or only slightly shorter for P 7 in males. Carpus length of P3, 4, 6 & 7 about 1.5x propodus in females, equal in length to propodus in males; of P5 about 2.0x propodus in females, 1.4x propodus in males. Dactylus of P3–7 curved; length slightly less than half of propodus for P3 & 4, about 0.5x propodus for P5–7 or slightly less for P5 & 6 in males. Uropod 3; peduncle width slightly less than 0.4x length in female, almost 0.5x length in male. Telson length about 0.4x peduncle U3.

Description of holotype

Female, 7.7 mm long ventrally, with pereon inflated to a maximum length of 7.0 mm by 5.8 mm deep. Length of pleon and urosome to telson is 2.3 mm. Head immersed in first pereonite, with lateral shield adjacent to, and slightly curved under, A1, shielding most of peduncle of A1. Eyes absent. Antennae 1; peduncle 3­articulate, the first two articles much broader than the third; callynophore conical, about twice as long as peduncle, followed by three smaller articles, the terminal one as long as preceding one with three long setae terminally. Antennae 2; length about two­thirds A1; 6­articulate, each article progressively narrower and shorter, the terminal one with three long setae terminally. Mandibular palp; first article only slightly shorter than second, both together half­length third article. Mouthparts generally like A. steenstrupi (examined in situ). Gnathopod 1; basis with convex margins, as long as ischium to propodus combined; propodus slightly shorter than carpus; dactylus thin and straight, about half­length propodus, inserted subterminally on medial surface. Gnathopod 2; length about 1.2x G1; similar to G1 except articles are more slender, basis has straight margins and dactylus is inserted terminally. Pereopods 3 & 4 of similar length and structure, longer than pereopods 5–7; basis slightly shorter than ischium to carpus combined; merus and carpus relatively broad with convex anterior margin; merus length about 0.8x carpus; carpus length about 1.5x propodus; dactylus stout, curved, slightly less than half­length propodus. Pereopod 5 with relatively slender articles; length about 0.8x P3/4; basis as long as merus and carpus combined; merus length 0.8x carpus; carpus length about 2.0x propodus; dactylus stout, curved, about half­length propodus. Pereopod 6 with slightly stouter articles than P5; length slightly more than 0.8x P5; basis slightly longer than merus and carpus combined; merus and carpus subequal in length; propodus length 1.5x carpus; dactylus stout, curved, half­length propodus. Pereopod 7 similar to P6 but shorter, only 0.7x P5. Uropod 1; peduncle with finely toothed outer margin, inner margin with seta near distal corner; rami with both margins toothed; outer ramus slightly longer than peduncle; inner ramus almost 1.2x length outer. Uropod 2 armed like U1; peduncle extends to limit of peduncle of U1; outer ramus subequal in length to peduncle; inner ramus almost 1.4x length outer. Uropod 3 armed like U2; outer ramus subequal in length to peduncle; inner ramus a little longer than outer. Telson rounded, a little longer than wide, as long as 0.4x peduncle U3.

Description of allotype

Male 4.2 mm. Cuticle with hexagonal markings. Pleon length 0.8x pereon. Head trapezoid, with slight mid­dorsal depression, height about twice width, as long as first pereonite. Eyes absent. Antennae 1 (left missing); as long as head and first three pereonites; peduncle 2­articulate, the first article longer than second; callynophore with medial two­field brush of aesthetascs, elongate, conical, length 4.0x peduncle, followed by three smaller articles, the terminal one slightly longer than preceding one, rounded terminally with one long seta. Antennae 2; right missing, left broken with only three articles remaining. Mouthparts like female (right mandibular palp missing). Gnathopod 1; basis similar in length to carpus and propodus combined; merus densly denticulate on medial surface; propodus length about 0.8x carpus; dactylus thin and straight, tip missing but longer than half propodus, inserted almost terminally. Gnathopod 2 as long as G1; similar to G1 except articles more slender; carpus and propodus equal in length; dactylus length about 0.8x propodus, inserted terminally. Pereopods 3 & 4 similar in length and structure, a little shorter than P5; basis slightly shorter than merus and carpus combined; merus and carpus relatively broad with convex anterior margin; merus with slight anterodistal bulge, slightly shorter than carpus; propodus slightly longer than carpus; dactylus stout, slightly curved, a little less than half­length propodus. Pereopod 5 the longest pereopod, with relatively slender articles; basis slightly shorter than merus and carpus combined; merus length 0.75x carpus; carpus length about 1.4x propodus; dactylus stout, curved, barely one­third length propodus. Pereopod 6 with slightly stouter articles similar to P3/4; length 0.8x P5; basis length equal to merus and carpus combined; merus slightly longer than carpus; propodus slightly longer than merus; dactylus stout, curved with broken tip but probably half­length propodus. Pereopod 7 similar to P6 but shorter, only slightly longer than 0.7x P5. Uropods and telson like female but peduncles and rami of U1­3 relatively shorter and more stout; peduncle of U1 & 3 with slightly convex margins.

Va r i a t i o n

Paratype 2, a mature female, is just like the holotype. Paratypes 1, 3 & 4 are all juvenile females with the pereon only slightly inflated; otherwise they do not differ significantly from the holotype. The only male specimen, other than the allotype, has not been included in the type series because it is in poor condition and covered in small deposits. It is less than 2.0 mm long and resembles the allotype except that the first antennae are almost as long as the pereon. Whether or not this is a juvenile character cannot be determined without additional material.

Etymology

This species is named for the Danish research vessel Dana which caught most of the specimens during the expeditions of 1920–22 and 1928–30, sponsored by the Carlsberg Foundation.

Remarks

This species initially came to my attention because of the relatively larger pereopods and urosome of females when compared with specimens of A. steenstrupi of similar size (compare figs 1 & 4 drawn to the same scale). A more detailed examination of material of both species revealed a host of other character differences as detailed in the diagnoses. In particular the morphology of the antennae, mandibular palp and pereopods differ significantly. When compared with A. steenstrupi , in both sexes of A. danae , the length of the callynophore of the first antennae, relative to the peduncle, is twice as long; the mandibular palp is relatively longer; the pereopods are of dissimilar length, with pereopod 7 distinctly the shortest (= 0.7 x P5); the dactyls of the pereopods are curved, that of pereopod 7 no longer than half of the propodus and the relative length of the merus/carpus and carpus/propodus of the pereopods is greater. In addition in females the second antennae are longer relative to the first (0.7 x A1) and consist of articles that are progressively shorter and narrower. In females of A. steenstrupi the second antennae are only about half as long as the first and the fourth article is the longest, longer than the previous two combined, and the terminal two articles are relatively small. Males of A. danae also have a relatively longer pleon and the gnathopods have longer and more numerous setae on the merus, carpus and propodus.

Archaeoscina danae is distinguished from A. stebbingi by the much longer pleon and relatively longer seventh pereopods. Also the third article of the mandibular palp is relatively longer or shorter depending on the accuracy of Wolterecks (1909) figure or description.

It seems likely that A. danae might be a larger species than A. steenstrupi because paratype 4, a female measuring 4.7 mm, has the pereon only slightly inflated, indicating that it is immature and the allotype male is longer than any other recorded male specimen of Archaeoscina . The latter specimen has well­developed aesthetascs on the callynophore of the first antennae, indicating sexual maturity. According to Vinogradov et al. (1982) females of A. steenstrupi are sexually mature at 3.5–4.0 mm and males at 2.5–3.5 mm.

Nothing is known of the biology of this species apart from distribution and catch records.

Distribution

The type locality is the northeast Pacific Ocean, Gulf of Panama. The allotype came from the Banda Sea (Indo­Pacific) and the paratypes all came from the tropical Atlantic Ocean, off Sierra Leone, near the Gulf of Guinea and south of Cape Verde Islands. The non­type male has inconclusive locality data but probably came from the North Atlantic, off Portugal (according to available USNM records).

Paratype 4 was caught at 720 m, the allotype with 5000 m of wire out and the remainder (except for the non­type male) with 3000 m of wire out.

Figures

FIGURE 4. Archaeoscina danae sp. nov., north­east Pacific, ZMUC CRU­ 4359. Holotype female. A, lateral view; B, mandibular palp. Scale bars = 1.0 mm (A), 0.5 mm (G 1 ­ P 7), 0.2 mm (Us), 0.1 mm (A 1 & 2, B).

FIGURE 5. Archaeoscina danae sp. nov., Banda Sea, ZMUC CRU­ 4360. Allotype male, 4.2 mm. A, lateral view; B, dorsal view of head; C, mandibular palp. Scale bars = 0.5 mm (A, B), 0.2 mm (G 1 ­ P 7, Us), 0.1 mm (C).