Lophogaster schmidti Fage, 1940

Lophogaster schmidti Fage, 1940 View in CoL

( Fig. 6 View Fig )

Lophogaster schmidti Fage, 1940: 326 View in CoL ; — 1942: 34, figs. 23, 24d, 25e; O. S. Tattersall, 1955: 45, fig. 3a–f; — 1960: 539, fig. 5; Yolanda et al., 2023b: 419 View Cited Treatment .

Material examined. Central Pacific. 1 male (cl 4.2 mm), KH-74-2, St. 20, 28°07.3′N 178°25.0′W – 28°10.2′N 178°35.0′W, ca. 1200–0 m, IKMT, 10 June 1974, coll. M. Murano (NSMT-Cr 32889). Western Pacific. 3 juvs (cl 3.1–3.3 mm), KH-67-5, St. H 14-2, 00°03.9′N 148°39.1′E – 00°02.7′N 148°37.3′E, 110 m, ORI net, horizontal tow, 25 Dec 1967, coll. M. Murano (NSMT-Cr 32890) GoogleMaps ; — 1 male (cl 3.8 mm), 1 juv. (cl. 2.8 mm), KH-67-5, St. H14- 16, 00°17.9′S 148°48.0′E – 00°17.2′S 148°50.3′E, 800–0 m, ORI net, oblique tow, 26 Dec 1967, coll. M. Murano (NSMT-Cr 32891) GoogleMaps ; — 1 female (cl 5.4 mm), l Kaiyo-Maru z, T-2, off Okinotorishima Is., 20˚23.9′N, 136˚16.5′E, 120-0 m, attached on mantle of squid, 22 Sept 1988, coll. M. Murano (NSMT-Cr 32936). Celebes Sea . 1 female (cl 5.3 mm), KH-72-1, St. 23-4, 04°41.4′N 122°43.3′E – 04°46.2′N 122°45.2′E, 1330–0 m, IKMT, 14 June 1972, coll. M. Murano (NSMT-Cr 32892). South Pacific GoogleMaps . 1 male (cl. 5.7 mm), KH-69-4, St. H123-1, 10°00.6′S 154°58.6′W – 09°59.5′S 154°58.6′W, 270– 190 m, ORI net, horizontal tow, 5 Oct 1969, coll. M. Murano (NSMT-Cr 32893) GoogleMaps ; — 1 juv. (cl. 1.4 mm) KH-69-4, St. H122-4, 14°48.5′S 155°04.3′W – 14°47.5′S 155°04.8′W, 720– 590 m, ORI net, horizontal tow, 15 Oct 1969, coll. M. Murano (NSMT-Cr 32894) GoogleMaps ; — 1 juv. (cl. 3.0 mm), KH-69-4, St. H 123-1, 14°30.0′S 155°18.7′W – 14°30.6′S 155°18.1′W, 1580–0 m, ORI net, oblique tow, 16 Oct 1969, coll. M. Murano (NSMT-Cr 32895); —2 juvs (cl 1.1, 1.2 mm), KH-69-4, St. H123-2, 14°30.7′S 155°18.0′W – 14°31.2′S 155°17.5′W, 155– 105 m, ORI net, horizontal tow, 16 Oct 1969, coll. M. Murano (NSMT-Cr 32896). Indian Ocean GoogleMaps . 1 male (cl 5.2 mm), KH-72-1, St. 35-3, 11°58.0′S 119°59.0′E – 11°51.3′S 119°55.2′E, 1480–0 m, IKMT, 27 June 1972, coll. M. Murano (NSMT-Cr 32897) GoogleMaps ; — 1 male (cl 5.3 mm), KH-72-1, St. 37-3, 11°52.5′S 109°59.5′E – 11°53.0′S 110°05.0′E, 3000–0 m, IKMT, 30 June 1972, coll. M. Murano (NSMT-Cr 32898) GoogleMaps ; — 1 female (cl 7.0 mm), KH-76-5, St. 11, 4°57.3′S, 87°08.1′E – 4°59.2′S 87°01.1′E, 870–0 m, ORI net, oblique tow, 23 Jan 1976, coll. M. Murano (NSMT-Cr 32899) GoogleMaps .

Diagnosis. Body integument somewhat lesscalcified, surface rather smooth and basically without distinct tubercles.

Carapace ( Fig. 6a, b View Fig ) with rostral plate well developed, grooved on dorsal part, completely covering basal 2 segments of antennular peduncle and eyes, exposing narrow distal part of cornea, stout tooth in antero-lateral part directed slightly outwards; rostral process moderately long, barely reaching end of antennular peduncle in male, while in females extending well beyond antennular lamina, occasionally extending beyond antennal scale; post-ocular process absent; posterior dorsal median carina noticeably ridged or sometimes obscure; postero-lateral tooth (alar spine) rather long, directed almost straightly backwards.

Eyes ( Fig. 6a, b View Fig ) rather small, cornea slightly wider than eye-stalk.

Abdomen ( Fig. 6c, d View Fig ) with median ventral process on anterior 5 somites, decreasing its height posteriorly; sixth somite sub-equal to or slightly longer than fifth, with sharp and long tooth on posterior dorso-lateral part; pleura normally ending in distinct tooth at postero-ventral part except first somite, of which that on second pleuron rarely obtuse.

Telson ( Fig. 6c, e View Fig ) 2.2–2.4 times as long as sixth abdominal somite, dorsal surface slightly sulcate, with feeble dorsal median process in basal part, commonly with 3, rarely 2, small setal-spines on lateral margin in addition to ordinary distal 2 pairs, among latter penultimate pair much smaller than distal pair and arising somewhat apart from terminal pair and barely reaching or falling just short of terminal margin; distal plate very indistinct and posterior margin truncate or weakly sinuous, bearing 9–11 small spines and 1 pair of plumose setae.

Endopod of uropod ( Fig. 6c, e View Fig ) extending slightly beyond last posterior pair of lateral setal-spines of telson; exopod sub-equal in length to endopod, outer margin ending in distinct tooth.

Antennular lamina ( Fig. 6f, g View Fig ) with anterior margin widely rounded and small projection at distal inner part, forming shallow groove, from which part single seta arising, but occasionally distal inner projection absent, merely forming rounded distal corner.

Antennal scale ( Fig. 6h View Fig ) ring-bell shaped, 1.4– 1.6 times as long as broad, widest near base owing to marked swollen; outer margin weakly convex or nearly straight in posterior half while slightly convex in anterior half bearing 4 or 5 teeth increasing its size anteriorly; apical tooth distinctly curving inwards.

Remarks. This species is diagnosed by having a combination of several remarkable characters: the carapace shows a rather smooth surfaces, with a well-developed rostral plate possessing a relatively long rostral spine reaching or extending far beyond the antennular peduncle, together with a long postero-lateral tooth (= alar spine); the second to fifth pleura of the abdomen armed with postero-ventral teeth; and the sixth abdominal somite with a long tooth at the postero-lateral end.

Distribution. Lophogaster schmidti is one of the most abundantly captured species in the present sampling series and probably distributed in common in the tropical waters of the West Pacific and Indian Oceans (see also O. S. Tattersall, 1960; Fage, 1942; Yalanda et al., 2023b).