Glandulotiron postremus, Just, 2022

Just, Jean, 2022, Tirons of the world: a review of ‘ tironid’ amphipods, description of new genera and species, and establishment of a new subfamily Tironinae Stebbing, 1906 stat. nov. (Crustacea, Synopiidae), Zootaxa 5139 (1), pp. 1-89 : 61-64

Glandulotiron postremus sp. nov.

( Figs 35–36 )

Type fixation. Holotype, ♀.—Here designated.

Etymology. This species was the last to turn up in this new genus, hence postremus (Latin for ‘last’).

Material examined. Holotype, ♀, 5.3 mm. Australia, Victoria, Western Bass Strait, 15 km S of Port Fairy, 38°32.00’S, 142°28.36’E, 52 m, medium sand, sled, R. Wilson , 20 November 1981, RV Tangaroa , stn BSS 187 , NMV J73733 .

Paratypes. Australia, Victoria, 50 km S of Mallacoota, 38°06.12’S, 149°45.30’E, 188 m, R. Wilson , 14 October 1984, FRV Soela, stn S05/84/30 ( BSS 228 S), NMV J73718 (1 ♀, 6.3 mm) . Australia, Tasmania, Eastern Bass Strait, 24 km NNE of Eddystone Point, 40°43.9’S, 148°32.5’E, 56 m, muddy sand, R. Wilson , 14 November 1981, RV Tangaroa , stn BSS 163 , NMV J75161 (paratype A, ♀, 4.5 mm) . Australia, Tasmania, Eastern Bass Strait, 24 km NNE of Eddystone Point, 40°43.9’S, 148°32.5’E, 56 m, muddy sand, R. Wilson , 14 November 1981, RV Tangaroa , stn BSS 163 , NMV J75162 (3 specimens) .

Description. Rostrum bluntly rounded. Interantennal lobes upper part a shallow even curve, lower margin a blunt, nearly right-angled corner. Accessory eye of 3 lenses, 2 adpressed anteriorly and 1 separate more posteriorly.

Mouthparts. Maxilla 1 palp with 5 simple, pointed robust setae, corner setae more slender than middle ones; outer plate with 9 robust setae, mostly smooth. Maxilliped outer plate with 1 long slender seta and 2 shorter spatulate setae, medial margin without spatulate setae, lateral surface with several simple, curved setae; inner plate medial margin with single plumose seta.

Antenna 1 as long as pereonites 1–5 combined along dorsum, peduncle article 2 about 2/3 length of 1, article 3 length 2/3 length of 2, article 1 with single large penicillate seta ventrally in posterior half and several setae mid dorsally, flagellum as long as peduncle articles 1 and 2 combined, of 6 articles, sparsely setose, assessory flagellum of 3+ articles. Antenna 2 as long as pereonites 1–6 and 3/4 of 7 combined along dorsum, peduncular article 4 one third longer than article 5, flagellum of 6 articles, articles 1 and 2 with single slender, curved robust seta anterodistally; antenna generally with scattered setae.

Coxal plates 1–3 with a few simple setae apically, plate 3 not much longer than broad, posterior margin slightly concave, plate 4 anterior margin an even convex curve, posterior margin concave in proximal half.

Gnathopod 1 basis anterior margin with a few short and medium setae, posterior margin with short row of long setae in proximal half, carpus anterior margin with 4 long setae, posterior margin with about 6 groups of a few long setae, propodus half as long as carpus, posterior margin with row of several pectinate setae and a few simple setae, dactylus length twice width, unguis as long as dactylus. Gnathopod 2 basis posterior margin with simple setae of varying length, anterior margin with a single long simple seta in proximal half, ischium with tuft of simple setae on posterodistal corner, carpus as long as basis, more slender than in gnathopod 1 with 4 long setae on anterior margin, about 5 groups of a few setae of varying length on posterior margin, propodus with a few setae of varying length on both margins, dactylus short, about twice as long as wide at base, unguis as long as dactylus.

Pereopods 3–4 normal, basis about twice as long as greatest width, with very few setae, propodus with small anteroterminal robust seta.

Pereopods 5 basis oval, distally widening to broad, rounded posterior lobe, posterior margin sinuous with concave proximal half, anterior margin with a few tiny setae, ischium anterior margin with single simple seta, merus posterodistal corner with 1 slender robust setae, anterodistal margin with single similar robust seta, carpus posterior margin with 1 long and 1 short robust setae in distal corner, anterior margin with 2 groups of 2 and 3 robust setae of different length, propodus with 4 posterodistal robust setae of different length. Pereopod 6 basis ovoid, with rounded posterodistal lobe, posterior margin with a few setules. Pereopod 7 basis width 0.9 length, broadest proximally, posterior proximal lobe larger than distal lobe, posterior margin with a few setules, medial surface with a few long setae, merus posterior margin with 1 long and 1 tiny robust setae in posterodistal corner, anterior margin small robust setae mid-margin and in distal corner and single long simple seta mid-margin, carpus length twice width, longer and more slender than in pereopods 5 and 6, posterior margin with 2 unequally long robust setae in distal corner, anterior margin with group of 3 short robust setae mid-margin and 2 separate robust setae, propodus with 2 long and 1 short robust setae in posterodistal corner.

Uropod 1 reaching as far as uropod 2, both reaching to about 1/4 along uropod 3 outer ramus, peduncle with a few short robust setae dorsolaterally, a couple of long setae mediodorsally, and setae in both distal corners, rami with 2 short robust setae apically, outer ramus with single long seta middorsally. Uropod 2 similar to uropod 1 but with fewer setae. Uropod 3 peduncle as long as basic article of ramus, outer ramus basal article with 4 dorsal robust setae and short row of 3 small robust setae ventrolaterally, second article with 3 increasingly long robust setae dorsally, inner ramus reaching 0.8 along outer ramus, dorsolateral margin with row of long plumose setae and 1 robust seta distally, apex with 3 robust setae similar to outer ramus.

Telson reaching 0.7 along outer ramus of uropod 3, dorsal view length/width 2.3, each lobe with row of 3 robust setae and a few simple setae, apices pointed triangular with single robust seta in hollow, lobes with internal row of elongate glands with ventrolateral opening.

Size. Largest ♀, 6.3 mm. ♂ not known.

Distribution. Australia, W and E Bass Strait, 52– 188 m.

Figures

FIGURE 35. Glandulotiron postremus gen. et sp. nov. Holotype, ♀, except P, paratype A. clv, head lateral view; mx1, maxilla 1; mxp, maxilliped; s, plumose seta of ventral margin of article 1 of antennula; up3 ir, uropod 3 tip of inner ramus; us, urosome.

FIGURE 36. Glandulotiron postremus gen. et sp. nov. Holotype, ♀. cox3, coxal plate 3; gp1–gp2, gnathopods 1 and 2; p4–p7; pereopods 4 to 7; tel, telson with glands in left lobe indicated.