Tanaissus giraffa, Błażewicz-Paszkowycz & Bamber, 2012

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 : 187-193

Tanaissus giraffa sp. nov.

Figures 126–129

Material examined. 1 (J58475), holotype; 1 (J23599), paratype, stn MSL-EG 45, Eastern Bass Strait , 13.5 km E of eastern edge of Lake Tyers , 37º51.74'S 148º14.77'E, 37 m depth, sand-shell, 25 September 1990, R. V. Sarda, Smith-McIntyre Grab. 1 (J28482), dissected, stn MSL-EG 67, Eastern Bass Strait, 13.3 km E of eastern edge of Lake Tyers, 37º51.42'S 148º14.36'E, 37 m depth, sand-shell, 4 June 1991, coll. N. Coleman, Smith-McIntyre Grab .

Description of female. Body ( Fig. 126A, B) slender, ten times as long as wide, 1.4 mm long. Cephalothorax as long as pereonites 2 and 3 combined, twice as long as wide, rostral half much narrower than posterior, with finely-rugose rounded rostral margin ( Fig. 127A). Pereonites all rectangular, pereonite1 shortest, 0.2 times as long as cephalothorax; pereonite 2 twice as long as pereonite 1; pereonites 3 to 6 subequal, 2.8 times as long as pereonite 1 (all pereonites respectively 2.5, 1.2, 0.9, 0.9, 0.9 and 1.0 times as wide as long). Pleon nearly twice as long as pereonite 6; pleonites subequal in length, three times as wide as long, all bearing pleopods; pleotelson subrectangular, as long as two preceding pleonites, 1.4 times as wide as long, with two setae above each uropod attachment and two fine distal setae.

Antennule ( Fig. 127A) slender, as long as cephalothorax, three–articled; article 1 four times as long as wide, 1.6 times as long as articles 2 and 3 combined, with proximal and distal outer clusters of four penicillate setae, and single inner and outer simple distal setae; article 2 longer than wide with single inner and outer simple distal setae; article 3 three times as long as wide, 1.5 times as long as article 2, with six simple distal setae and one penicillate seta.

Antenna ( Fig. 127B) six–articled, article 1 short and annular, article 2 twice as long as article 1, 1.5 times as long as wide, with dorsal seta; article 3 as long as article 1, with dorsal seta; article 4 longer than articles 1 to 3 combined, five times as long as wide, curved, with six distal and subdistal penicillate setae; article 5 as long as article 1, with long seta; article 6 very small, with four setae.

Labrum ( Fig. 127C) rounded, hood-shaped, naked. Mandibles stout; left mandible ( Fig. 127D) with triangular incisor and broader denticulate lacinia mobilis, molar gently curved, weak and acutely pointed; right mandible ( Fig. 127E) with finely denticulate distal margin and bifid incisor; molar as on left mandible. Labium ( Fig. 127H) two-lobed with slightly notched distal processes.Maxillule ( Fig.127F) endite sigmoid, with two distal setae and eight terminal spines; palp with two distal setae. Maxilla ( Fig. 127G) triangular, naked. Maxilliped ( Fig. 127I) basis with short seta near articulation with palp; palp article 1 naked, article 2 with three inner weak setae, article3 with three unequal inner setae, and article 4 with two longer and three shorter simple setae; endites almostcompletely fused. Epignath ( Fig. 127J) with distinct basal lobe, distally slender and finely setulose.

Cheliped ( Fig. 128A) attachment posterior on cephalothorax, basis extending past anterior margin of pereonite 1 ventrally, with rounded posterior free margin, 1.4 times as long as wide, with small laterodistal seta; merus subtriangular, with ventral seta; carpus 1.3 times as long as broad, with one dorsal and two ventral setae; chela 1.4 times as long as carpus, propodus without bifid dorsodistal crest, anterior comb-row of five dendritic setae; fixed finger robust, with convex cutting edge, two ventral setae and three setae near cutting edge; dactylus narrow, curved and acute, with several dorsal nodules and one small anterior seta.

Pereopod 1 ( Fig. 128B) longer and more slender than pereopods 2–3; coxa with seta; basis 7.3 times as long as wide; ischium with small seta; merus three times as long as wide, half as long as basis, with ventrodistal seta; carpus as long as merus, with two distal setae, both much shorter than propodus; propodus 0.8 times as long as carpus, with small dorsodistal spine-like apophysis; dactylus half as long as unguis, both together 0.7 times as long as propodus. Pereopod 2 ( Fig. 128C) stouter than pereopod 1, coxa with seta; basis narrow proximally, 3.5 times as long as wide, with one mid-dorsal and two ventral penicillate setae; ischium with one small seta; merus distally expanded, 0.4 times as long as basis, with one seta and one spine ventrodistally; carpus 0.7 times as long as merus, rectangular, with one dorsodistal and one ventrodistal spines; propodus 1.2 times as long as carpus, with two ventrodistal spines; dactylus and unguis together 0.8 times as long as propodus. Pereopod 3 ( Fig. 128D) similar to pereopod 2.

Pereopod 4 ( Fig. 128E) basis 3.8 times as long as wide with two mid-ventral penicillate setae; ischium with two setae; merus 0.8 times as long as carpus, with two ventrodistal spines; carpus nearly three times as long as wide, with outer and inner dorsal spines longer than outer and inner ventral spines, simple dorsodistal seta; propodus 1.25 times as long as carpus, 2.4 times as long as wide, with one dorsodistal seta and two ventrodistal spines; dactylus and very short bifurcate unguis apparently distinct, together 0.9 times as long as propodus. Pereopod 5 ( Fig. 128F) similar to pereopod 4, dactylus with microtrichia, together with unguis as long as propodus. Pereopod 6 ( Fig. 128G) similar to pereopods 4 and 5 but basis without penicillate setae, propodus with three dorsodistal setae, dactylus plus unguis shorter than propodus.

Pleopods all similar ( Fig. 128H), with basal article about as long as wide, naked; endopod and exopod rami similar, but endopod somewhat wider, with eight terminal setae, exopod with nine terminal setae; all setae plumose and longest barely as long as rami.

Uropod ( Fig. 128I) slender, twice as long as pleotelson; basal article twice as long as wide, naked; exopod two-segmented, just longer than proximal article of endopod, with one distal seta on longer proximal segment, two unequal distal setae on distal segment; endopod two–segmented, proximal segment shorter and with one simple and two penicillate distal setae, distal article with one subdistal and three distal simple setae and one distal penicillate seta.

Distinctions of male. Body ( Fig. 126C) slightly larger than female, length 1.5 mm. Cephalothorax similar to that of female. Pereonites more or less rectangular, or with slightly concave lateral margins; pereonite 1 not shortest, 0.7 times as long as each of cephalothorax and pereonite 2; pereonites 2 and 3 subequal, pereonites 4 to 6 progressively shorter, pereonite 6 half as long as pereonite 1. Pleon as long as pereonites 4 to 6 inclusive.

Antennule ( Fig. 129A) seven–articled, shorter than cephalothorax; peduncle article 1 stout, 3.3 times as long as wide, with array of nine dorsal penicillate setae in proximal half, mid-inner simple seta, one longer and one shorter outer distal simple setae with adjacent penicillate seta, and one dorsodistal seta; peduncle article 2 compact, 0.2 times as long as article 1, with two inner setae; flagellum of five segments, proximal four segments with group of five or six outer distal aesthetascs; distal segment with four simple distal setae.

Mouthparts absent apart from large maxillipeds. Maxilliped ( Fig. 129B) basis with seta near articulation with palp; palp articles 1 and 2 similar in length, article 2 with two small and one long setae; article 3 longer than articles 1 and 2 combined, with three inner setae; article 4 small, with two short, tow medium and two very long terminal setae.

Cheliped ( Fig. 129C) similar to that of female, but carpus more slender, 1.7 times as long as wide, chela more slender and longer than carpus, fixed finger narrower; comb-row of 20 setae.

Pereopods ( Fig. 129D to G) generally similar to those of female; pereopod 2 ( Fig. 129E) propodus with microtrichia; pereopods 4 to 6 ( Fig. 129F, G) with more slender propodi (about 5 times as long as wide), dactyli slender and severely curved.

Pleopods all similar ( Fig. 129H), proportionately larger than in female and rami more elongate; endopod with one distal and eleven outer plumose setae, exopod with fourteen plumose setae, longest setae more than twice as long as rami.

Uropod similar to that of female.

Etymology. With reference to the unusually long pereonite 1 of the male, Giraffa (from the Arabic – zirafah) is the genus of the African camelopard ruminant with an extraordinarily long neck (noun in apposition).

Remarks. There are four described species of Tanaissus (see Bird, 2002: Bamber et al., 2009), all from the Northern Hemisphere, three from the North Atlantic and one from the Mediterranean. Bamber et al. (2009) give a key to three of these, in which the female of T. giraffa sp. nov. fails at couplet 2, owing to its having a single-pointed, acuminate molar process on the mandible but no bifid dorsal crest on the chela; the male of the present species fails at couplet 4 owing to its having a pleon longer than pereonites 4 and 5 together, but no ventral apophysis on the cheliped carpus; in addition, its antennular segmentation is distinct from all of these species, as is the very long pereonite 1. The fourth species, T. psammophilous ( Wallace, 1919, q.v.), known only from the female, is incompletely described, but differs from T. giraffa in being less elongate (about 7 times as long as wide), in the proportions of the pereonites and of the antennule, and in the structure of the chela.

Tanaissus giraffa was recorded from the Eastern Bass Strait on shelly sand at 37 m depth.