Leptocheliidae Lang, 1973

Bamber, Roger N, Bird, Graham, Błażewicz-Paszkowycz, Magdalena & Galil, Bella, 2009, Tanaidaceans (Crustacea: Malacostraca: Peracarida) from soft-sediment habitats off Israel, Eastern Mediterranean, Zootaxa 2109, pp. 1-44 : 29-34

Family Leptocheliidae Lang, 1973

Genus Leptochelia Dana, 1849

Leptochelia tanykeraia Bamber sp. nov. Figs 12–14

Synonymy:? L. dubia Monod, 1933 non- Tanais dubius Krøyer, 1842 (partim)

Material examined. Holotype: female holotype (NHM.2008.4822), station RFI 7, off the coast of Israel, 31º48.809’N 034º28.892’E, 62 m depth, fine mud, 14 September 2006. Allotype: 1 male (NHM.2008.4823), station RFI 4, 31º54.193’N 034º33.241’E, 59 m depth, fine mud, 14 September 2006. Paratypes: 2 females (NHM.2008.4824–4826), 1 female, dissected, station RFI 7, same sample as holotype; 3 females ( TAU AR 28429), station RFI 1, 31º53.640’N 034º33.069’E, 57 m depth; 1 female ( TAU AR 28430), station RFI 5, 31º53.633’N 034º33.251’E, 55 m depth; all 14 September, 2006. 3 females ( TAU AR 28431), RFI 3, 31°53.842’N 0 34°33.300’E, 57.0 m depth; 3 females ( TAU AR 28432), RFI 5; 159 specimens (NHM.2008.4827–4836), including brooding females and 2 males, RFI 7; all 20 October 2007. All fine mud. 1 female, 2 neuters (NHM.2008.4837–4839), station NM H71, 32º45.057’N 034º56.565’E, 10.3 m depth, 17 August 2006.

Other material: 1 female, AGAN 6, 31°51.342’N 034°39.050’E, 11.8 m depth; 0 2 May 2007. 2 females, AGAN 8, 31°51.707’N 034°38.855’E, 11.3 m depth; 0 2 May 2007. 1 female, RFI 4; 92 specimens, including brooding females, RFI 7; both 20 October 2007. 1 female, NMI H7, 32 0 32.696’N 34 0 53.717’E, 12.5 m depth, 0 7 August 2007. 1 female, HMA DA19, 31° 52.447’N 034° 38.468’E, 27.2 m depth, 20 October 2007.

Diagnosis: Leptochelia with three distal setae on maxilliped basis and third article of female antennule 1.4 times as long as the second. Pereopod 1 basis slender, 4.4 times as long as wide; dactylus and unguis together some 1.4 times as long as propodus. Pereopods 2 and 3, merus as long as carpus. Uropod exopod of one segment, two-thirds as long as proximal endopod segment, endopod of five slender segments. Male of the “ dubia ”- type, antennule half as long as body.

Description of female: body ( Figure 12 A) slender, holotype 2.1 mm long, 7.4 times as long as wide. Cephalothorax subrectangular, 1.25 times as long as wide, twice as long as pereonite 1, with slight rostrum, eyelobes conspicuous, eyes present and black. Six free pereonites; pereonite 1 shortest, pereonites 2 to 5 progressively longer (pereonite 5 one-and-a-half times as long as pereonite 1), pereonite 6 as long as pereonite 1 (all pereonites respectively 1.6, 1.4, 1.2, 1.1, 1.1 and 1.5 times as wide as long). Pleon of five free subequal pleonites bearing pleopods; each pleonite about 5 times as wide as long, with paired lateral setae. Pleotelson ( Figure 13 F) semicircular, just shorter than last two pleonites together, twice as wide as long, with single lateral setae on each side and two distal setae lateral to, and two distal setae on, caudal protrusion.

Antennule ( Figure 12 B) of three tapering articles and one minute distal article, proximal article 3.9 times as long as wide, longer than distal three articles together, with two long outer and two shorter inner setae; second article over twice as long as wide, one third as long as proximal article, distal outer seta 0.6 times as long as article; third article 1.4 times as long as second, with two distal setae; fourth article minute, eccentric, with five distal setae and one aesthetasc.

Antenna ( Figure 12 C) of six articles, proximal article compact with small ventral seta; second article longer than wide, with single inner distal and dorsodistal slender spines; third article as long as wide, with dorsodistal slender spine; fourth article longest, four times as long as wide, with paired distal setae; fifth article half as long as fourth, with one distal seta; sixth article minute, with four distal setae.

Labrum ( Figure 12 D) trapezoid, setose. Left mandible ( Figure 12 E) with smooth lacinia mobilis, four crenulations on pars incisiva, pars molaris robust with strong rugosity; right mandible ( Figure 12 F) similar but without lacinia mobilis, pars incisiva with finer crenulations. Labium ( Figure 12 G) relatively narrow, distally finely setose, without palp. Maxillule ( Figure 12 H) with ten distal spines and setose outer margin; palp distinct, with two distal setae. Maxilliped ( Figure 12 I) palp first article naked, second article with one outer and three inner distal setae, distal-most inner seta reaching only half length of third palp article; third and fourth articles with filtering rows of five setae, third article with three further inner distal setae, fourth article with two outer setae; basis with three long distal setae not extending to distal margin of second palp article; endites distally with single seta and two robust spatulate spines, inner distal edge with two fine spines. Maxilla (not figured) oval, naked; epignath not seen.

Cheliped ( Figure 13 A) with rounded, elongate basis twice as long as wide; merus triangular with three ventral setae; carpus 2.5 times as long as wide, with three midventral setae and two dorsal marginal setae; propodus slender, palm just longer than maximum width, fixed finger about half length of palm, with three ventral and three inner setae, cutting edge crenulate; dactylus naked.

Pereopod 1 ( Figure 13 B) longer than other pereopods; coxa naked; basis slender, 4.4 times as long as wide; ischium compact; merus as long as carpus, with single ventrodistal seta; carpus with three distal setae, longest of which (dorsodistal seta) half length of propodus; propodus as long as carpus and merus together, with four subdistal setae on dorsal swelling, one ventral subdistal seta; dactylus slender, extending into slender unguis of equal length, the two together some 1.4 times as long as propodus; single proximal seta on dactylus. Pereopod 2 ( Figure 13 C) more compact than pereopod 1; ischium with one seta; merus as long as carpus, merus with ventrodistal spine, carpus with dorsodistal and ventrodistal setae; dactylus and short unguis together 0.6 times as long as propodus. Pereopod 3 similar to pereopod 2.

Pereopod 4 ( Figure 13 D) basis stout, twice as long as wide; ischium with two setae; merus 1.2 times as long as carpus, with two short, ventrodistal spines (only one visible in Figure 13 D); carpus with one outer, one ventral and one inner distal short spines (the last not visible in Figure 13 D); propodus 1.5 times as long as carpus, with two ventrodistal slender simple spines, three longer and two shorter dorsodistal setae, the longest almost as long as dactylus plus unguis; dactylus and unguis just longer than half propodus, curved. Pereopod 5 as pereopod 4, but with only three dorsodistal setae on propodus. Pereopod 6 ( Figure 13 E) similar to pereopod 4, but propodus as long as carpus and with crown of seven distal setae.

Pleopods ( Figure 12 J) all alike, typical for the genus, basis naked.

Uropod ( Figure 13 F) biramous, basis naked; exopod of one segment, two-thirds as long as proximal endopod segment, outer distal seta longer than inner distal seta; endopod of five slender segments, setose as figured.

Description of male: smaller than female (allotype length 1.7 mm), body ( Figure 14 A) more compact, 6 times as long as wide; cephalon as long as wide, just longer than pereonites 1 and 2 together, with large eyelobes bearing large black eyes; pereonite 1 shortest, pereonites 2, 3 and 6 progressively slightly longer, pereonites 4 and 5 subequal, longest, 1.7 times as long as pereonite 1. Sexual dimorphism as follows.

Antennule ( Figure 14 B) elongate, half as long as body, first peduncle article 4.6 times as long as wide with conspicuous rounded inner proximal apophysis; second article 0.45 times as long as first; third article half as long as second; flagellum of 8 segments, most bearing distal pair of aesthetascs, proximal segment with additional proximal pair of aesthetascs. Mouthparts atrophied.

Cheliped ( Figure 14 D) more slender than that of female; carpus curved, 4.7 times as long as wide; propodus fixed finger as long as palm, with two low inner tooth-like apophyses on cutting edge; dactylus with setose crenulations along cutting edge. Setation of pereopods (e.g. Figs 14 E, F) similar to that of female; dactylus and unguis of first pereopod 1.1 times as long as propodus; carpal spines on pereopods 4 to 6 longer than in female; propodus of pereopod 6 one-and-a-half times as long as carpus.

Etymology: from the Greek tany —long, and keraia —antenna.

Remarks. The second and third articles of the antennule in Leptochelia species are normally subequal in length: the present species is quite distinct (and thus recognizable without dissection) in having the third article 1.4 times as long as the second. Monod (1933) figures something similar in some of his “ Leptochelia dubia ” material from the Gulf of Suez, which was thus probably the same species, but as little other information was presented, it is not possible to be sure. There are four described species of Leptochelia which have three distal setae on the maxilliped basis, L. itoi Ishimaru, 1985 from Japan, L. lusei Bamber & Bird 1997 from Hong Kong, L. nobbi Bamber, 2005 from Western Australia, and L. karragarra Bamber, 2008 from Queensland, Australia; a further as-yet-unpublished species has been recognized from the Azores (Bamber, in prep.). Of these five, only L. itoi also has a pereopod 1 basis significantly more than four times as long as wide (4.2 times) and the dactylus and unguis of the first pereopod as much as 1.3 times as long as the propodus, but the proximal antennule article of that species is only 2.5 times as long as wide (3.9 times in L. tanykeraia sp. nov.), and none of these other species has such a slender cheliped carpus (2.5 times as long as wide in L. tanykeraia , 2.1 times or less in all the others).

In addition to the unique antennule-article proportions, the ornamentation of the maxilliped endite of L. tanykeraia is unique in having only two robust spatulate spines distally but with two fine spines on the inner distal edge, all other described species of Leptochelia having three robust spatulate spines distally, and no fine spines on the inner distal edge. The male of the present species is less remarkable, being broadly similar to that of L. “ dubia ” sensu Sars, 1886 from the Mediterranean coast of Italy.

Leptochelia is a shallow-water genus, normally found from the littoral zone down to about 15 m depth; the present species, largely taken from between 55 and 62 m depth (although as shallow as 10 m towards the north of the survey area), is the deepest so far recorded.

Figures

FIGURE 12. Leptochelia tanykeraia sp. nov., female, A, holotype, dorsal; B, antennule; C, antenna; D, labrum; E, left mandible; F, right mandible; G, labium; H, maxillule; I, maxilliped; J, pleopod. Scale line = 0.4 mm for A; 0.1 mm for B to J.

FIGURE 13. Leptochelia tanykeraia sp. nov., female, A, cheliped; B, pereopod 1; C, pereopod 2; D, pereopod 4; E, pereopod 6; F, pleotelson and right uropod. Scale line = 0.2 mm.

FIGURE 14. Leptochelia tanykeraia sp. nov., male allotype, A, entire, dorsal; B, antennule; C, antenna; D, cheliped, E, pereopod 1; F, pereopod 6. Scale line = 1 mm for A; 0.25 mm for to F.