Tanaopsis oios, 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 : 212-217

Tanaopsis oios sp. nov.

Figures 144–145

Material examined. 1 (J58547), holotype (on microscope slide), 1 further (lost), Eastern Bass Strait , 28 km SSW of Marlo, Stn BSS 207 , 37º59'S 148º27'E, 51 m depth, muddy sand and fine shell, 30 July 1983 ; coll. M.F. Gomon & R. S. Wilson .

Description of female. Body slender with widened pleon, typical for the genus but damaged (not figured).

Antennule ( Fig. 144A) of four longer articles but with incipient articulation of minute distal article, proximal article 1.9 times as long as wide, three-quarters as long as distal three articles together, outer margin with tufts of three penicillate setae at mid-length and four penicillate and one simple setae distally, inner margin with simple distal seta; second article 1.25 times as long as wide, 0.6 times as long as first article, subdistally with single inner and outer simple setae; third article compact, 0.4 times as long as second article, distally with single inner and outer simple setae; fourth article tapering, 2.4 times as long as third article, with single simple subdistal seta and four simple distal setae.

Antenna ( Fig. 144B) of six articles, proximal article compact, naked; second article as long as wide, 2.5 times as long as first article, with single dorsodistal and ventrodistal setae and microtrichia; third article shorter than wide, 0.6 times as long as second article, with fine dorsodistal seta longer than article; fourth article longest, three times as long as third article, three times as long as wide, slightly curved, with two simple and five penicillate distal setae; fifth article just longer than third, naked; sixth article minute with five distal setae.

Labrum ( Fig. 144C) acorn-shaped, naked. Mandibles and labium not recovered. Maxillule ( Fig. 144D) with five distal spines, one stouter than the others, and outer tufts of setules, palp not recovered. Maxilla ( Fig. 144E) linguiform but medially expanded, naked. Maxilliped palp ( Fig. 144F) first article naked, second article with one outer and two inner distal setae; third article with three inner distal setae; fourth with six inner to distal setae, distal two much longer than the others; basis seta not seen; endite distally with inner seta and setules below outer corner. Epignath ( Fig. 144G) elongate, linguiform, distally hooked, naked.

Cheliped ( Fig. 145A) with rounded basis 1.9 times as long as wide, single dorsodistal seta; merus subtriangular with single ventral seta; carpus stout, 1.4 times as long as wide, with two midventral setae, one mid-dorsal and one dorsodistal setae; propodus stout, 1.5 times as long as wide, fixed finger 0.7 times as long as palm, with two ventral setae, three setae on cutting edge, distal claw with typical inner and outer bifurcate rounded apophyses ( Fig. 145B); dactylus dorsally coarsely crenulate.

Pereopod 1 ( Fig. 145C) without coxal apophysis, coxa with seta; basis 3.6 times as long as wide, with dorsoproximal simple seta; ischium compact, with ventral seta; merus one-third as long as basis, wider distally, with sparse microtrichia; carpus 0.9 times as long as merus, with three dorsal and single ventral distal setae; propodus 1.9 times as long as carpus, with three dorsal subdistal setae, one ventral subdistal seta, sparse dorsal microtrichia and dorsodistal spine-like apophysis; dactylus with longer proximal seta, half as long as slender unguis, both together 1.3 times as long as propodus. Pereopod 2 ( Fig. 145D) basis 3.5 times as long as wide, dorsally with one simple seta and one penicillate seta in proximal half; ischium with seta; merus as long as carpus, naked; carpus with two dorsal and one ventral distal setae and sparse microtrichia; propodus 2.4 times as long as carpus, with two dorsal subdistal setae, one longer ventral subdistal seta exceeding tip of dactylus, and sparse microtrichia; dactylus with longer proximal seta, slender unguis 1.7 times as long as dactylus, both together as long as propodus. Pereopod 3 (not figured) similar to pereopod 2.

Pereopod 4 similar to pereopod 5, but basis without penicillate setae. Pereopod 5 ( Fig. 145E) basis relatively stout, 2.3 times as long as wide, with two midventral penicillate setae; ischium with two ventrodistal setae; merus, carpus and propodus subequal in length; merus with two small distally-denticulate ventrodistal spines; carpus with one inner distal seta and three small distally-denticulate ventrodistal spines; propodus with fields of microtrichia, mid-dorsal penicillate seta, one dorsodistal and two ventrodistal spines finely denticulate in distal half; dactylus with fields of microtrichia, 1.5 times as long as unguis, both together 0.9 times as long as propodus. Pereopod 6 ( Fig. 145F) as pereopod 5, but basis without penicillate setae, propodus with three dorsodistal spines.

Pleopods ( Fig. 145G) all alike, with naked basis, endopod shorter than exopod and with rounded proximal apophysis on inner margin; endopod with inner subdistal plumose seta and nine outer plumose setae in distal half; exopod without setae on inner margin, outer margins with 21 plumose setae, proximal seta not separated from others.

Uropod ( Fig. 145H) biramous, basis naked; exopod and endopod each of two subequal segments; exopod distinctly longer than proximal endopod segment, proximal segment with one and distal segment with one shorter and one longer distal setae; endopod with two distal penicillate setae on first segment and five simple and one penicillate distal setae on second segment.

Male. Unknown.

Etymology. From the Greek oios – alone, singular, as only one specimen from a remote part of the Bass Strait remains.

Remarks. Of the previously-described species of Tanaopsis with two clear segments in both uropod rami, only three have the uropod exopod exceeding the length of the proximal endopod segment. In comparison with T. oios sp. nov., T. graciloides sensu Lang, 1967 has a much less slender cheliped basis, the rugosity on the cheliped dactylus not restricted to the distal half; a more slender antennal article 4, and fewer distal setae on anterior pereopod carpi. T. laticaudata has a more compact cheliped carpus, the rugosity of the cheliped dactylus more extensive, fewer distal setae on anterior pereopod carpi, and is without the long ventral seta on the propodus of pereopod 2. T. cadieni has a more slender antennal article 4, has a triangular coxal apophysis on pereopod 1, and is without the long ventral seta on P2 propodus.

T. oios was only found in the Eastern Bass Strait to the east of the Gippsland Lakes, at 51 m depth on shelly muddy sand.