Typhlotanais Sars, 1882

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 : 16-19

Genus Typhlotanais Sars, 1882

Typhlotanais angstromensis Bła ż ewicz-Paszkowycz & Bamber sp. nov. Figures 5–6

Material examined. Holotype: 1 female (NHM.2008.4817), station RFI 1, off the coast of Israel, 31º53.640’N 034º33.069’E, 57 m depth, fine mud, 14 September 2006. Paratypes: 2 females, dissected (NHM.2008.4818–4819), same sample as holotype; 1 female (NHM.2008.4820), station RFI 4, 31º54.193’N 034º33.241’E, 59 m depth; 1 female (NHM.2008.4821), station RFI 7, 31º48.809’N 034º28.892’E, 62 m depth; all fine mud, 14 September, 2006. 1 female ( TAU AR 28425), RFI 3, 31°53.842’N 034°33.300’E, 57.0 m depth; 1 female ( TAU AR 28426), RFI 7; both 0 3 May 2007. 3 females ( TAU AR 28427), RFI 2; 6 specimens ( TAU AR 28428), RFI 7; both fine mud, 20 October 2007.

Other material: 1 female, dissected, station RFI 2, 31º53.328’N 034º32.853’E, 58 m depth; 14 September, 2006. 1 specimen, RFI 4; fine mud, 20 October 2007.

Diagnosis: (female) very small Typhlotanais , body 7.2 times as long as wide, pereonites with slightly rounded lateral margins, pleotelson with small distal setae. Antennule little shorter than carapace, article 3 less than twice as long as article 2; anterior pereopods without coxal apophysis, compact; pereopod 1 basis naked; pereopod 2 basis twice as long as wide; pereopods 4 to 6 carpus with prickly-tubercles of moderate size, not surrounded by spines; propodal distal seta as long as dactylus. Uropod rami 1-segmented, exopod about half as long as endopod.

Description of female: body ( Figure 5 A, B) compact, small (holotype 0.8 mm long, 7.2 times as long as wide). Cephalothorax margin slightly rounded, tapering anteriorly, 1.2 times as long as wide, as long as pereonites 1 and 2 together, naked, eyes absent. Six free pereonites with lateral margins slightly rounded; pereonite 6 shortest, pereonites 1 and 2 subequal, 1.25 times as long as pereonite 6, pereonites 3 to 5 subequal, 1.5 times as long as pereonite 6 (all pereonites respectively 2.1, 1.9, 1.6, 1.5, 1.5 and 2.3 times as wide as long). Pleon of five free subequal pleonites bearing pleopods; each pleonite 4.7 times as wide as long. Pleotelson subtriangular, as long as last two pleonites, distally pointed, with one posterolateral seta on each side and four distal setae ( Figure 6 G).

Antennule ( Figure 5 C) shorter than carapace, of three articles, proximal article 2.4 times as long as wide, longer than distal two articles together, with two simple and four penicillate setae in two groups along article; second article one-third as long as first article, with three distal setae; third article tapering, 1.7 times as long as second article, with five distal setae and one aesthetasc.

Antenna ( Figure 5 D) of six articles, proximal article compact, naked; second article twice as long as proximal article, longer than wide, with two short distal setae; third article as long as wide, with dorsodistal seta; fourth article longest, 2.6 times as long as second and four times as long as wide, with four distal setae; fifth article as long as second with one distal seta; sixth article minute with five distal setae.

Labrum ( Figure 5 E) flat, distal margin setose. Left mandible stout ( Figure 5 F) with well-developed, crenulate lacinia mobilis, pars molaris with sharp tooth-like protrusions and spinules, pars incisiva robust, crenulate; right mandible without lacinia mobilis. Labium ( Figure 5 H) bilobed, both lobes sparsely setose distally. Maxillule ( Figure 5 G) with nine distal spines, palp not seen; maxilla elongate, angular. Maxilliped ( Figure 5 I) bases each with single seta reaching only half length of endite; endites distally with setose outer margins and each with two distal oval tubercles; palp first article naked, second article wedge-shaped with one outer and three inner setae, one of these strongly serrated; third article with two simple and two serrated inner setae; fourth article with five distal and one dorsal simple setae.

Cheliped ( Figure 6 A) with rounded, naked basis 1.9 times as long as wide; merus subtriangular with single ventral seta; carpus with rounded dorsoproximal extension, elongate, 2.5 times as long as wide, with two midventral setae, smaller ventrodistal seta and single dorsodistal and dorsoproximal setae; chela welldeveloped, palm of chela 1.9 times as long as wide, with outer and inner distal setae, fixed finger more than half as long as palm, with two ventral setae, three setae and three teeth distally on cutting edge; dactylus slender, curved, with two spines on cutting edge.

Pereopod 1 ( Figure 6 B) of walking-type ( sensu BłaŻewicz-Paszkowycz, 2007 ), longer than others, coxa without apophysis, with seta; basis slender, 5 times as long as wide, sinuous, naked; ischium compact with ventrodistal seta; merus 1.7 times as long as wide, just longer than carpus, naked; carpus with one distal seta; propodus 1.3 times as long as carpus, 2.7 times as long as wide, with two dorsodistal setae, one subdistal ventral seta, dorsodistal pointed apophysis; dactylus half length of distinct, slender unguis, with distal seta, both together 0.8 times as long as propodus. Pereopod 2 similar to pereopod 3. Pereopod 3 ( Figure 6 C) of walking-type, basis twice as long as wide with two proximodorsal setae; ischium compact with ventrodistal seta; merus subequal to carpus; carpus 1.7 times as long as wide, with two simple distal setae; propodus 1.8 times as long as wide and 1.25 times as long as carpus, with single dorsodistal and minute ventrodistal setae; short, stout, naked dactylus with slender unguis together two-thirds as long as propodus.

Pereopod 4 ( Figure 6 D) of clinging-type ( sensu BłaŻewicz-Paszkowycz, 2007 ); basis stouter, 1.7 times as long as wide; merus and carpus of equal length, merus with two short ventrodistal spines and ventral fields of microtrichia; carpus with distal hooks and simple seta, prickly tubercles of moderate size, numerous microtrichia ventrally; propodus 1.5 times as long as carpus, dorsal margin serrate, with two short ventrodistal spines and distal seta almost as long as dactylus; dactylus ventrally serrate, distally bifurcated, together with unguis 0.6 times as long as propodus. Pereopod 5 as pereopod 4. Pereopod 6 ( Figure 6 E) as pereopod 4, but propodus with three dorsodistal setae.

Pleopods ( Figure 6 F) all alike, with naked basis, endopod and exopod each with ventrodistal plumose setae, and proximal seta separated from others by distinct gap.

Uropod ( Figure 6 G) biramous, both exopod and endopod of one segment; exopod about half as long as endopod with stout longer and fine shorter setae; endopod with four distal setae and group of subdistal penicillate setae.

Male unknown.

Etymology: named after the small unit of length, an Angstrom, owing to this species being probably the smallest Typhlotanais yet described.

Remarks. Typhlotanais sensu lato was another “dustbin” genus, which is currently being resolved. Recently, BłaŻewicz-Paszkowycz (2004; 2005), while redefining Peraeospinosus Sieg, 1986 (comprising species originally attributed to Typhlotanais as well as new taxa), pointed out the presence of a number of “morpho-groups” within Typhlotanais sensu lato which warranted distinction as separate genera, and she reported the principal phase of that work in BłaŻewicz-Paszkowycz (2007) giving us our current understanding of the Typhlotanaidae .

The present species does not accord with any of the new genera or morpho-groups defined by BłaŻewicz- Paszkowycz (2007: 25), remaining in Typhlotanais sensu lato at present. Only three species of the Typhlotanaidae have been recorded previously from the Mediterranean, viz. Typhlotanais aequiremis (Lilljeborg, 1864) (the type and currently only species of Typhlotanais sensu stricto), T. messinensis Sars, 1882 (of the “ greenwichensis ”-group of BłaŻewicz-Paszkowycz, 2007), and T. spinipes Kudinova-Pasternak, 1982 (of the “ eximius ”-group of BłaŻewicz-Paszkowycz, 2007). T. angstromensis sp. nov. does not have the long antennule of the “ eximius ”-group (twice as long as the carapace), nor the pronounced coxal apophysis of the “ greenwichensis ”-group, nor the setation of the basis and carpus of pereopod 1 characteristic of Typhlotanais sensu stricto, and is thus easily distinguished from the other Mediterranean species (as well as on its size).

The new species is most closely related to T. grahami BłaŻewicz-Paszkowycz, 2004 (included in Typhlotanais sensu lato), known only from its type locality in the West Antarctic. Both species are very small tanaidaceans no longer than 1 mm, and they share numerous characters, including the slightly rounded lateral margins of the pereonites, the relatively robust cheliped (with the carpus 2.5 times as long as wide, and the chela almost the size of the carpus), compact pereopods 1 to 3, the moderate size of the prickly tubercles on pereopods 4 to 6, and the distal seta on the propodus of these pereopods about the same length as the dactylus.

The new species however is much more slender than T. grahami , and has a one-segmented uropod exopod (two-segmented in T. grahami ) and relatively short setae on the pereopod 1 propodus and the pereopod 2 carpus, these being long in T. grahami .

Typhlotanais angstromensis was only found in the finer mud sediments of the RFI stations, at between 55 and 62 m depth. It is the smallest species of the genus known: again, its discovery probably reflects the merit of using 0.25 mm mesh sieving.

Figures

FIGURE 5. Typhlotanais angstromensis sp. nov., female, A, holotype, dorsal; B, holotype, lateral; C, antennule; D, antenna; E, labrum; F, left mandible; G, maxillule; H, labium; I, maxilliped. Scale line = 0.4 mm for A, B; 0.1 mm for C to I.

FIGURE 6. Typhlotanais angstromensis sp. nov., A, cheliped; B, pereopod 1; C, pereopod 3; D, pereopod 4; E, pereopod 6; F, pleopod; G, uropod. Scale line = 0.1 mm.