Brachyscelus globiceps ( Claus, 1879 )

Zeidler, Wolfgang, 2021, A review of the hyperiidean amphipod family Brachyscelidae Stephensen, 1923 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 5026 (3), pp. 405-439 : 416-419

Brachyscelus globiceps ( Claus, 1879)

( Figs 5–6 )

Thamyris globiceps Claus, 1879: 182–183 (36–37).— Bovallius 1887a: 30.— Claus 1887: 57–60, pl. 16, figs 1–10.

Brachyscelus globiceps — Stephensen 1925: 176–177, 230 (table), fig. 65.— Barnard 1931: 130.— Barnard 1932: 293.— Barnard 1937: 190.— Shoemaker 1945: 242–243.— Shoemaker 1948: 13.— Reid 1955: 26.— Tashiro & Jossi 1972: fig. 8 (map), 20 (list), 35 (table).— Vinogradov et al. 1982 /1996: 396/489 (key), 398–400/492–493, fig. 214.— Barkhatov & Vinogradov 1988: 168 (table).—Vinogradov 1990: 77, 95 (table).— Vinogradov 1991: 261 (table), 262–263.— Zeidler 1992: 115 (key), 116, fig. 20.— Vinogradov 1993: 45 (table).— Coleman 1994: 348–349, 364–369, figs 5–6, 9.— Lin & Chen 1994: 115, 118 (list).— Lin et al. 1995: 118, 122 (table).— Shih & Chen 1995: 178 (key), 182, fig. 119.— Lin et al. 1996: 231 (table).— Zeidler 1998: 96–97.— Barkhatov et al. 1999: 808 (table).— Vinogradov 1999: 1145 (table), 1193 (incl. key), fig. 4.135.— Lowry 2000: 325 (list).— Gasca & Shih 2001: 496 (table).— Escobar-Briones et al. 2002: 367 (list).— Gasca 2003a: 308 (table).— Gasca 2003b: 118 & 119 (tables).— Gasca & Shih 2003: 96 (table).— Gates et al. 2003: 300 (text fig.), 301–302.— Gasca & Suárez-Morales 2004: passim.— Vinogradov et al. 2004: 16, 24 (table).— Brusca & Hendrickx 2005: 151 (list).— Zelickman 2005: xvii (list), fig. 43a-c (pp. 268–273).— Browne et al. 2007: 819 (table), fig. 4 (phylogenetic tree).— Gasca 2007: 118 (table).— Garcia-Madrigal 2007: 155, 192 (list).— Costa et al. 2009: 102–103, 197, fig. 186.— Gasca 2009a: 89 (table).— Gasca 2009b: 66 (table).— Lavaniegos & Hereu 2009: passim.— LeCroy et al. 2009: 969 (table).— Mori et al. 2010: 6 & 10 (lists).—Gasca et al. 2012: passim.—Hurt et al. 2013: 31 (table), figs 1, 2 (phylogenetic).— Gasca & Franco-Gordo 2014: 76 (list).— Burridge et al. 2016: passim.— Zeidler 2016: 47 (key).— Hereu et al. 2020: passim.— Espinosa-Leal et al. 2021a: passim.— Espinosa-Leal et al. 2021b: passim.

Thamyris antipodes Spence Bate, 1862: 335 , pl. 53, fig. 4.— Bovallius 1887a: 31.— Bovallius 1887b: 574. NEW SYNONYMY

Thamyris mediterranea Claus, 1887: 60 , pl. 16, figs 11–18.— Lo Bianco 1902: 423, 448.— Lo Bianco 1903: 135, 144, table facing p. 278.— Lo Bianco 1904: 44, pl. 23, fig. 77. NEW SYNONYMY

Tamyris mediterranea — Lo Bianco 1902: 426 (lapsus).

Brachyscelus mediterranea — Stebbing 1888: 1556–1557.

Brachyscelus mediterraneus — Fowler 1904: 50.—Stebbing 1904: 40–41.

Brachyscelus latipes Stebbing, 1888: 1550–1552 , pl. 197B.— Irie 1948: 36 (table).— Irie 1959: table 4.

Type material. Type material of Thamyris globiceps could not be found in any major European institution and is considered lost. The type locality is the western Indian Ocean , off Zanzibar. Claus (1887) illustrates a male (about 12 mm) but does not document any other specimens .

Type material of synonyms. Type material of Thamyris antipodes could not be found in any major European institution and is considered lost. The type locality is the South Pacific, south of New Zealand [58°S 172°W]. This species has been considered a junior synonym of B. crusculum in the past but the figure of a female (about 6 mm) provided by Spence Bate (1862) clearly illustrates the basis of pereopod 6 with a rounded antero-distal lobe, characteristic of B. globiceps or B. macrocephalus rather than B. crusculum . Also, the head, as illustrated, is relatively small so it is not B. macrocephalus and is thus, regarded here, a junior synonym of B. globiceps . Brachyscelus rapax and B. rapacoides both have the basis of pereopod 6 with a narrow, more pointed, antero-distal lobe.

Type material of Thamyris mediterranea could not be found in any major European institution and is considered lost. No type locality is provided but it is obviously the Mediterranean Sea, probably the Gulf of Naples. Claus (1887) illustrates a juvenile male. Vinogradov et al. (1982, 1996) list it as junior synonym of B. crusculum but, as in the above species, the figures and description provided by Claus (1887) more closely match that of B. globiceps than any other species. Claus (1887) even casts doubt on his determination, suggesting that it might actually be his B. globiceps . Thus, it is here regarded a junior synonym of B. globiceps . Stebbing’s (1888) record of this species is included here because he says that his specimen is like that of Claus (1887); similarly, Stebbing (1904) and Fowler’s (1904) appendix to the latter. The record of Chevreux (1900) and Senna (1903) are most likely of B. crusculum .

The unique holotype female (about 7.5 mm) of Brachyscelus latipes is in the NHM, London (89.5.15.304), on two microscope slides. The type locality is the South Pacific, Challenger, surface, October 1875. An examination of this holotype has confirmed the synonymy .

Material examined. Type material of B. latipes as detailed above and the following. In AM: Tasman Sea, off Port Hacking [34°09’S 152°07’E], 550–0 m, one male (P39857) . In Canadian Museum of Nature: tropical Atlantic, just west of Barbados , 2 females. In NHMD: Mediterranean Sea, Thor station 24 [40°14’N 12°23’E], 65 metres of wire out, one female. S.E. Atlantic, Galathea station 98 [08°25’S 11°09’E], one female, 4 males. In SAM: S.W. Indian Ocean, off South Africa, Meiring Naude collection [27°35.4’S 32°44.2’E], 236–0 m, one male. In SAMA: N. Pacific, [50°0.5’N 165°0.2’W], 150 m, one female (C14086) ; [46°58.9’N 165°1.0’W], 1200–0 m, one male (C14087) ; [37°53’N 123°25’W], 50–0 m, one female, one male (C14088) . Gulf of Mexico, [19°34’03”N 87°20’04”W], one female (C14089) . N.E. Indian Ocean, off northern Western Australia, Ningaloo Reef , 10 males (4 lots, C14090–14093) .

Diagnosis. Body length up to 12 mm for females and 10 mm for males. Head globular in both sexes; depth 1.3 x length in females, 1.6 x length in males. Antennae 2 of males; length of terminal article about one-quarter preceding one. Gnathopod 1 basis slightly shorter than for G2, with distinct pocket for A 2 in males; carpus with antero-distal corner developed into feeble lobe or lobe absent; carpal process with large teeth, each with row of serrations, or small teeth, on margins; posterior margin of propodus armed in similar manner; dactylus relatively sharp, length about 0.4 x propodus. Gnathopod 2 similar to G1 but basis without pocket and antero-distal corner of carpus not produced. Pereopods 3 and 4 morphologically similar, P4 marginally longer than P3; merus slightly inflated anteriorly, length about 0.3 x basis; carpus and merus sub-equal in length; propodus 1.2 x carpus length for both P3 and P4. Pereopod 5 marginally longer than P6; basis oval-shaped, length 1.6 x maximum width, without antero-distal lobe; merus about 0.3 x basis length, slightly shorter than carpus; propodus about 1.2 x carpus length; dactylus relatively long, almost 0.4 x propodus. Pereopod 6 basis length 1.7 x maximum width for females, 1.6 x for males, anterior margin almost straight, antero-distal lobe relatively broad with evenly rounded distal margin produced just beyond ischium; posterior margin evenly rounded in females, slightly more bulging proximally in males, without postero-distal lobe; merus slightly inflated, length almost 0.3 x basis, slightly longer than carpus; propodus about 1.3 x carpus length; anterior margin of merus, carpus and propodus with small serrations; dactylus relatively short, about 0.3 x propodus. Pereopod 7 basis with posterior margin only slightly inflated, length about 2 x maximum width, about 1.5 x as long as remaining articles combined; merus 1.3 x carpus length; propodus about 0.7 x carpus length, with complex projections on antero-distal corner; dactylus hook-shaped, partly retractile. Uropod 1 with relatively broad peduncle; endopod 1.5 x peduncle and 1.2 x exopod length. Uropod 2 endopod 1.5 x peduncle and 1.2 x exopod length. Uropod 3 endopod about 3.5 x peduncle and 1.3 x exopod length, slightly broadened distally, with minor excavation terminally on inner margin. Rami of all uropods with serrated margins. Double urosomite about 1.5 x wider than long. Telson slightly shorter than width at base, apex evenly rounded.

Remarks. In this species the head of males is rounded like that of females. It is most similar to B. crusculum but, apart from the head shape, is most readily distinguished by the shape of the basis of pereopod 6, in which the antero-distal lobe is rounded, and the postero-distal lobe is not developed. Also, the basis of pereopod 5 lacks an antero-distal lobe, and the double urosomite is distinctly broader than long. It is also similar to B. macrocephalus in the morphology of the basis of pereopods 5 and 6, but is distinguished by the relatively smaller head and the morphology of the spines on the carpus and propodus of the gnathopods as defined in the key to species. Also, B. macrocephalus is a much smaller species.

Coleman (1994) examined the anatomy of the alimentary canal and compared it to several other hyperiidean species.

Distribution. A relatively uncommon but widespread species, known mainly from tropical regions worldwide. Most common in the eastern basin of the Mediterranean Sea. In the Atlantic it has been recorded from near the Cape Verde Islands in the north and the tropical western part, from the Sargasso Sea to the Gulf of Mexico, and off western Africa. In the Pacific it is widely distributed in tropical regions and is common in the China Seas. In the Indian Ocean it has only been recorded from the south western part and also the Arabian Sea. Most records are from near-surface waters.

Figures

FIGURE 5. Brachyscelus globiceps (Claus, 1879). Female 12.2 mm. N. Pacific, Alaska Gyre [50°05’N 165°0.2W], 150 m (SAMA C14068). Scale bars: 1.0 mm (habitus); 0.2 mm (A1); 0.5 mm (remainder).

FIGURE 6. Brachyscelus globiceps (Claus, 1879). Male 8.0 mm, AM P39857. Tasman Sea, 75 km E. of Port Hacking [34°15’S 152°06’E], 550–0 m. Scale bars: 1.0 mm (habitus); 0.5 mm (remainder). (Redrawn from Zeidler 1992: fig. 20).