Bathytanais bathybrotes (Beddard, 1886)

Błażewicz-Paszkowycz, M. & Bamber, R. N., 2012, The Shallow-water Tanaidacea (Arthropoda: Malacostraca: Peracarida) of the Bass Strait, Victoria, Australia (other than the Tanaidae), Memoirs of Museum Victoria 69, pp. 1-235 : 98-102

Bathytanais bathybrotes (Beddard, 1886)

Figures 65–67

Paratanais bathybrotes Beddard, 1886 (a), 119 – Bathytanais bathybrotes Bamber, 2008 , 175–176, literature.

Material examined. 12 specimens (including 2 brooding) (J56271), 1 (J56272), from sand wall at front of Pope’s Eye , Port Philip Bay, 7 m depth, 28 February 1982, coll. R Lipson .

The female of this species was comprehensively redescribed by Lang (1972); however, the male was previously unknown – indeed, no male of any Bathytanais species has been recorded before, making the following description particularly important.

Description of male. Body ( Fig. 65A, B) with typical gross appearance of a Paratanais male, 2.1 mm long, 5.3 times as long as wide. Cephalothorax subrectangular, as long as wide, as long as pereonites 1 to 3 together, with conspicuous subtriangular rostrum; eyes large, one-third as long as cephalothorax, with black ommatidia. Pereonite 1 shortest, pereonites 2, and 3 subequal in length, 1.4 times as long as pereonite 1, pereonites 4 and 5 subequal, 1.8 times as long as pereonite 1, pereonite 6 just shorter than pereonite 5 (all pereonites respectively 3.6, 2.7, 2.8, 2, 2 and 2.3 times as wide as long). Pleon of five free subequal pleonites bearing pleopods, ventrally with blunt keel; pleonites 2.7 times as wide as long and 1.2 times as long as pereonite 1. Pleotelson ( Fig. 47K) semicircular, as long as pereonite 6, 1.5 times as wide as long.

Antennule ( Fig. 66A) of three peduncular and four flagellar articles, proximal peduncle article 1.9 times as long as wide, with outer mesial tufts of penicillate setae, inner distal simple seta; second article just shorter than wide, 0.4 times as long as first article, with outer-distal tuft of penicillate setae; third article one-third length of second, with two simple distal setae; first flagellar article half as long as third peduncle article, with proximal and distal rows of six or seven aesthetascs and outer-distal simple seta; second and third flagellar articles subequal in length, four times as long as first, with distal rows of six aesthetascs; fourth flagellar article just shorter than third, distally with four simple setae, one penicillate seta and one aesthetasc.

Antenna ( Fig. 66B) of six articles, proximal article compact, naked; second article with ventrodistal tuft of three penicillate setae and one ventrodistal and one dorsodistal simple setae; third article as long as wide, 0.6 times as long as second article, with dorsodistal seta; fourth article twice as long as third, with one mid-dorsal and three dorsodistal penicillate setae, single dorsal and ventral subdistal simple setae; fifth article 0.9 times as long as fourth with one dorsal subdistal seta; sixth article minute with five simple and one penicillate distal setae.

Mouth parts underdeveloped in comparison with those of female. Labrum ( Fig. 66C) apically rounded, naked. Mandibles absent. Maxillule ( Fig. 66D) with naked endite and simple palp bearing distal setule; maxilla ( Fig. 66D) ovoid, naked. Maxilliped ( Fig. 66E) endites relatively wide, with two minute ovate tubercles and single inner seta; palp first article with outer-distal seta; second article with three inner-distal simple setae; third article with three inner setae in proximal half; fourth article with five inner to distal setae and one outer subdistal seta; single inner seta on basis not reaching distal margin of endites.

Cheliped ( Fig. 66F) compact, basis twice as long as wide, naked; merus subtriangular, ventrally convex, with one mid-ventral seta; carpus 1.3 times as long as wide with two mid-ventral setae, one dorsoproximal and one dorsodistal fine setae; propodus as long as wide, with inner comb-row of 12 setae; fixed finger just shorter than palm, with two ventral setae, three setae adjacent to cutting edge; dactylus with dorsoproximal seta, two proximal setae on cutting edge.

Pereopod 1 ( Fig. 67A) longer than others, coxa simple with seta; basis slender, 4.25 times as long as wide with dorsoproximal penicillate seta; ischium compact with single seta; merus one-third as long as basis, with fine ventrodistal seta; carpus 0.9 times as long as merus, with fine ventrodistal seta and two dorsodistal setae; propodus 1.8 times as long as carpus, with one dorsal and two ventral subdistal setae, and dorsal and ventral marginal microtrichia; dactylus half as long as slender unguis and with distal seta, dactylus and unguis together 0.9 times as long as propodus. Pereopod 2 ( Fig. 67B) similar to pereopod 1, but more compact, basis 3.4 times as long as wide; merus and carpus equal in length, carpus without dorsodistal setae; propodus with two dorsal and one ventral subdistal setae, dactylus with proximal seta. Pereopod 3 ( Fig. 67C) similar to pereopod 2.

Pereopod 4 ( Fig. 67D) basis stout, 2.6 times as long as wide, with three ventral subdistal penicillate setae; ischium with two ventral setae; merus one-third as long as basis, naked; carpus as long as merus, with two ventrodistal and one dorsodistal tooth-like spines; propodus 1.7 times as long as carpus with dorsodistal seta, two ventrodistal spines, mid-distal penicillate seta and marginal rows of penicillate setae; dactylus long and slender, four times as long as distinct unguis, both together 0.8 times as long as propodus. Pereopod 5 ( Fig. 67E) similar to pereopod 4, but basis with dorsoproximal pair of penicillate setae, merus with two ventrodistal tooth-like spines, carpus with additional larger outer distal spine and dorsodistal seta, dactylus and unguis distinctly more curved. Pereopod 6 ( Fig. 67F) as pereopod 5.

Pleopods ( Fig. 67G) all alike, with naked basis, rami subequal; endopod with inner subdistal plumose seta and 13 plumose setae around outer margin; exopod without setae on inner margin, 19 plumose setae around outer margin.

Uropod ( Fig. 67H) basis naked; exopod of two subequal segments, together more than half as long as endopod, first segment with simple outer-distal seta, second segment with two unequal distal simple setae; endopod of three segments, proximal segment short, naked, second segment twice as long as first, with proximal array of seven penicillate setae, distally with one simple and one penicillate setae; third segment as long as second, distally with five simple and one penicillate setae.

Remarks. The history of this species was discussed by Bamber (2008), from which we may disregard the type-locality as being a lapsus calami. Bathytanais bathybrotes was previously known from New South Wales at depths of 6 to 50 m depth ( Beddard, 1886b; Lang, 1972) and from Moreton Bay, Queensland at depths between 8 and 42 m ( Bamber, 2008) on clean sand. The present material extends its distribution further west to Victoria.

The Bathytanais male is very similar to males of Paratanais species, and does not show the expanded antenna peduncle articles of the females, but appears to differ in the presence of a proximal seta on the dactyli of pereopods 2 and 3. Discovery of the males of other species is necessary to confirm this as a generic character.