Torquella angularis Kudinova-Pasternak 1966

Torquella angularis (Kudinova-Pasternak, 1966)

Figures 1–3

Typhlotanais sp. A: Belyaev (1966): 88.

Typhlotanais angularis: Kudinova-Pasternak (1966): 529–531; Kudinova-Pasternak (1968): 73; Lang (1970): 270, 287; Shiino (1970): 98; Morino (1971): 354; Kudinova-Pasternak (1975): 213; Kudinova-Pasternak (1978): 127. Torquella angularis BłaŻewicz-Paszkowycz (2007).

Material examined. 9 females (1 dissected on slides), station XR-12, 41º37.67’– 41º37.08’N 146º54.19’– 146º52.72’E, 5473–5484 metres, 4 m ORE beam trawl, 23 September 2001.

Diagnosis. Carapace round, as long as wide. Pereonite 3 longer than wide. Chela three times longer than wide. Antennule article 3 about twice as long as article 2. Pereopod 1 merus and carpus shorter than basis, merus with short (rod) seta, carpus with three short and three rod setae, propodus with one long simple seta ventrally; pereopods 4–5 propodus distal seta reach half of dactylus.

Complementary description of female

Body (Fig. 1). Length 7.3 mm, eight to nine times as long as wide.

Carapace. Almost as long as wide, smooth, 15% of body length, rounded laterally, rostrum small, acute.

Pereonites. Pereonite 1 about 1.8 times as wide as long, latero-proximal corners expanded forward. Pereonites 2, 3 and 5 of similar size, little longer than wide. Pereonite 6 1.3 times as wide as long.

Pleon. 15% of body length, pleonites 1–5 similar in size.

Pleotelson. Rectangular.

Antennule (Fig. 2 A). Article 1 slim, three times as long as wide, with two long simple and pinnate setae in two groups medially and distally on inner margin and two simple setae medially on outer margin. Article 2 with two setae distally. Article 3 almost twice as long as article 2 with six setae distally.

Antenna (Fig. 2 B). Article 2 twice as long as article 3, naked. Article 3 with one seta. Article 4 about 2.6 times as long as article 5, with two simple and four pinnate setae distally. Article 5, with one simple seta distally. Article 6 very short, with seven terminal setae.

Mouthparts. Labrum lost during dissection. Mandibles (Figs C, D) massive; molar process well developed, edges supported with tubercle-like structures; lacinia mobilis well developed. Maxillule (Fig. 2 E) inner endite with eight apical spiniform setae; palp lost during dissection. Maxilla (Fig. 2 E) triangle shape. Labium (Fig. 2 F) bilobed, outer lobe and outer corner of inner lobe setose. Maxilliped (Fig. 2 H) bases fused, with simple setae reaching over half of endites; endite armed with seta in distolateral margin and two tubercles distally; palp article 1 naked; article 2 wedge-shaped, with one strong and two simple setae on inner margin and one seta on outer margin; article 3 with three long setae and one short simple seta on inner margin; article 4 with five strong setae distally and one short seta on outer margin. Epignath (Fig. 2 G) tip rounded.

Cheliped (Fig. 3 A). Basis 1.3 times as long as wide, with one seta dorso-distally. Merus wedge-shaped with one seta ventrally. Carpus about twice as long as broad, with two dorsal setae and with two long and one short setae ventrally. Propodus and fixed finger as long as carpus, about three times as long as wide, with one seta near insertion of dactylus. Fixed finger with three setae on inner margin and with two setae ventrally. Dactylus with proximal seta dorsally.

Pereopod 1 (Fig. 3 B). Of walking type. Coxa present. Basis as long as merus, carpus and half of propodus combined, with two minute and one pinnate setae dorsally. Ischium short, with minute seta. Merus as long as carpus, with one rod seta disto-ventrally. Carpus with three short simple and three rod setae distally. Propodus 1.5 times as long as carpus, with one long seta ventrally and three setae dorsally (serrated, rod and spiniform). Dactylus with long seta; unguis 1.5 longer than dactylus.

Pereopod 2 (Fig. 3 C). Of walking type. Coxa with one seta. Basis with two simple and one pinnate seta dorsally, as long as merus, carpus and propodus combined. Ischium with one seta. Merus subequal to carpus, with one simple and two spiniform setae distally (one robust). Carpus with two simple, two spiniform setae and two rod setae distally. Propodus as long as merus and carpus combined, with spiniform seta ventrally and with one spiniform and one long (reaching over unguis) setae dorsally; merus, carpus, and propodus with numerous microtrichiae. Dactylus with one seta; unguis 1.5 times as long as dactylus.

Pereopod 3 (Fig. 3 D). Similar to pereopod 2, but merus with one spiniform seta. Carpus with two spiniform and one simple setae distally. Ventral side of merus and carpus with some spines.

Pereopod 4 (Fig. 3 E). Of clinging type. Basis with twice as long as wide, with one pinnate seta ventrally and one short seta dorsally. Ischium with two setae ventrally. Merus with two spiniform setae and strong spines ventrally. Carpus with one setae disto-dorsally, two hooks distally and prickly tubercles surrounded by a few strong spines. Propodus over seven times as long as wide, with one pinnate seta dorsally, two strong spiniform ventro-distal setae and with distal seta shorter than dactylus. Propodus twice as long as dactylus and unguis combined. Unguis distally simple, with row spines on ventral margin.

Pereopod 5. Similar to pereopod 4.

Pereopod 6 (Fig. 3 F). Similar to pereopod 4, but propodus with three setae distally.

Pleopods (Fig. 3 G). Exopod little shorter than endopod, with row of ten setae on outer margin and one seta on inner margin. Endopod with row of fifteen plumose setae on outer margin; clear gap between the most proximal and other setae in both rami.

Uropod (Fig. 1 C). Endopod with two articles, proximal article little shorter than distal with one simple and one pinnate setae distally; proximal article with two pinnate and six simple setae distally. Exopod with two articles reaches beyond over endopod proximal article; proximal article with one seta distally, distal article with two setae distally.

Remarks: Torquella angularis was described by Kudinova-Pasternak (1966) based only on one female and two mancae but the poor condition of the holotype excluded any redescription, pending this study. Finding eight females in the close vicinity of the type locality has made it possible to present a complementary description and to define characters distinguishing the species from the other members of the genus.

Torquellids can be distinguished by the setation of the merus, carpus and propodus of first two pair of pereopods, the spination in the carpus of pereopods 4–6, and setation of propodus of pereopods 4–6. For example, T. parangularis has only one simple seta dorsally on the carpus of pereopods 2 and 3 while most Torquella species, including T. angularis, have at least one spiniform seta there. One long distal seta on the propodus of pereopod 6 distinguishes T. eltaninae from T. angularis and other members of the genus as well. The propodus of pereopod 2 in T. angularis bears one spiniform and one long, simple seta dorsally. T. elegans and T. galatheae have two long setae there. The first species has also six long setae on the carpus of pereopod 2 which is a unique character among members of Torquella. The former species, T. galatheae, has relatively short ventral seta on the propodus of pereopod 1 which is relatively long in T. angularis (reaching end of unguis). T. magdalensis has a long seta ventrally on the propodus of pereopod 2 and 3 in contrast to T. angularis and most torquellids. Finally, the North Atlantic species T. grandis has only one seta on the propodus of pereopod 2 but the carpus of pereopods 4–6 is supported in numerous small spines, which are strong and sparsely distributed in T. angularis.

T. angularis and the Antarctic species T. longisetosa show most similarity in their pereopod setation. Minute differences are in the length of the rod setae in the carpus of pereopod 1. One of those seta is relatively long (reach 0.3 of propodus length) in T. longisetosa while all three rod setae are short in T. angularis. Furthermore, the pereonite 5 of T. longisetosa is clearly longer than pereonite 4 and has a relatively short propodus in pereopods 2 and 3 which is only four times longer than wide. In T. angularis pereonites 4 and 5 are subequal, while the pereopod 2 propodus is six times longer than wide.

Distribution: Torquella angularis is known from the type locality: 40°19.7'N, 175°45.3'E (Vitjaz Station 4074, depth 6065 metres) and from station XR-12 of the KH01-2 program at a slightly shallower depth (5473–5484 metres).