Hamatipeda sima, 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 : 170-175

Hamatipeda sima sp. nov.

Figures 114–116

Material examined. 1 (J58901), holotype, 4 (J58902), paratypes, Eastern Bass Strait , 85 km NE of North Point, Flinders Island, Stn BSS 169 S, 39º02.4'S 148º30.6'E, 120 m depth, sandy-mud, 15 November 1981; coll. R. S. Wilson .

Description of female. Body ( Fig. 114A, B) elongate, slender, holotype 3.9 mm long, 13 times as long as wide. Cephalothorax subrectangular, tapering towards anterior with slight triangular rostrum, 1.4 times as long as wide, naked, eyes absent. All pereonites with parallel sides, all but the sixth longer than wide: pereonite 1 as long as cephalothorax; pereonites 2 and 4 subequal, 1.5 times as long as cephalothorax; pereonite 3 longest, 1.75 times as long as cephalothorax; pereonite 5 shorter than pereonite 4, 1.4 times as long as cephalothorax; pereonite 6 shortest, 0.6 times as long as cephalothorax (all pereonites respectively 0.8, 0.5, 0.4, 0.5, 0.6 and 1.1 times as wide as long). Pleon with five free subequal pleonites bearing pleopods; each pleonite 4.8 times as wide as long. Pleotelson semicircular, twice as long as each pleonite and 1.9 times as wide as long, with four small distal setae.

Antennule ( Fig. 115A) of three articles, proximal article stout, 2.7 times as long as wide, five times as long as distal two articles together, with one simple inner seta, outer margin with tufts of two or three penicillate setae proximally, at mid-length and distally, the last two tufts also with one simple seta; second article nearly as long as wide, attached within invagination of proximal article but as long as third article, with single outer and inner simple setae; third article tapering, 1.4 times as long as wide, with six simple and one penicillate distal setae.

Antenna ( Fig. 115B) of six articles, proximal article compact, naked; second article twice as long as wide and twice as long as first article, with dorsodistal seta; third article as long as wide, as long as first article, with dorsodistal seta and ventral microtrichia; fourth article longest, five times as long as wide, with fields of microtrichia, and distal crown of three simple and three penicillate setae; fifth article one-quarter as long as fourth with one distal seta; sixth article minute with four distal setae.

Labrum ( Fig. 115C) rounded, hood-shaped, distally veryfinely setose. Left mandible ( Fig. 115D) with subtriangular pars incisiva and linguiform, bilobed lacinia mobilis, right mandible ( Fig. 115E) without lacinia mobilis but with longer cutting edge on pars incisiva; pars molaris of both mandibles with strong, smooth distal margin. Labium ( Fig. 115I) simple, finely setose on outer margins. Maxillule ( Fig. 115F) with eight distal spines, rows of microtrichia on outer margin of endite, palp with two distal setae. Maxilla ( Fig. 115G) ovoid, naked. Maxilliped palp ( Fig. 115H) first article naked, second article with one outer and three inner setae; third article with one robust and three shorter inner setae, all finely denticulate in distal two-thirds; fourth article with five inner to distal setae, proximal of these finely denticulate in distal half, and one outer subdistal seta; basis with single, long seta not reaching distal margin of endites; endites distally with two setae and non-articulate tubercle. Epignath ( Fig. 115J) elongate, linguiform, naked.

Cheliped ( Fig. 116A) with rounded basis not reaching pereonite 1 ventrally, twice as long as wide; merus subtriangular with single ventral seta; carpus stout, 1.5 times as long as wide, with two midventral setae, one fine dorsoproximal seta, and one dorsodistal seta; propodus palm just longer than wide, fixed finger 0.85 times as long as palm, with two ventral setae, three setae on cutting edge, cutting edge finely denticulate; dactylus with fine proximal seta.

Pereopod 1 ( Fig. 116B) longer than others, coxal without apophysis, with seta; basis straight, 4.3 times as long as wide, with one simple and one penicillate dorsoproximal setae and one ventrodistal seta; ischium compact, with ventral seta; merus one-third as long as basis, with two ventrodistal and one dorsodistal simple setae; carpus just longer than merus with two ventrodistal and two dorsodistal simple setae; propodus 1.3 times as long as carpus, with two dorsal subdistal setae and one ventral subdistal seta; dactylus half as long as slender unguis, both together 0.9 times as long as propodus. Pereopod 2 ( Fig. 116C), coxa similar to pereopod 1, basis 4.1 times as long as wide without dorsoproximal penicillate seta; merus 0.25 times as long as basis, without dorsodistal seta; carpus with three dorsodistal and three ventrodistal setae and small ventrodistal spine; propodus 1.5 times as long as carpus, with two dorsal subdistal setae and one ventral subdistal seta; short, stout dactylus half as long as unguis, both together 0.7 times as long as propodus. Pereopod 3 compact ( Fig. 116D), similar to pereopod 2, merus with dorsodistal seta.

Pereopod 4 ( Fig. 116E) basis stout, 1.8 times as long as wide, with two penicillate setae near ventrodistal corner; ischium with two ventrodistal setae; merus 1.4 times as long as carpus, with field of microtrichia across ventral and ventrolateral surfaces in distal two-thirds, and two dentiform ventrodistal spines; carpus with three dentiform hook-like ventrodistal spines and dorsodistal seta; propodus 1.25 times as long as carpus, with mid-dorsal penicillate seta, strong dorsodistal seta, and two ventrodistal dentiform spines; dactylus slender, with fields of microtrichia, four times as long as curved unguis, unguis distally trifurcate, both together 0.65 times as long as propodus. Pereopod 5 ( Fig. 116F) as pereopod 4. Pereopod 6 ( Fig. 116G) as pereopod 4, but basis without penicillate setae, propodus with three dorsodistal setae.

Pleopods ( Fig. 116H) all alike, with naked basis, exopod shorter than endopod; endopod and exopod without setae on inner margin, outer margins with respectively 11 and 20 plumose setae, proximal seta on both rami separated from others.

Uropod ( Fig. 116I) biramous, basis naked; exopod and endopod of one segment, exopod shorter than endopod, with one fine proximal and two distal setae; endopod with one simple and two penicillate setae just distal of mid-length, distally with four simple and one penicillate setae.

Male. Unknown.

Etymology. From the Greek simos, meaning “snub-nosed”, alluding to the characteristic very short distal antennular articles of the present species.

Remarks. The distinctive genus Hamatipeda is characterized by the very elongate body, with pereonites 1 to 5 longer than wide and as long as (pereonite 1) or longer than the cephalothorax, and the specialized dentiform hook-like spines on the carpus of the posterior pereopods, inter alia. H. sima sp. nov. is entirely typical of the genus.

Of the two previously described species, Hamatipedia trapezoida Błażewicz-Paszkowycz, 2007 , is distinct in having trapezoidal pereonites which are narrower posteriorly than anteriorly, while H. longa ( Kudinova-Pasternak, 1975) is distinct in having a two-segmented uropod endopod. Both have a more slender cheliped carpus, more slender posterior pereopod bases, lack distinctive tubercles on the maxilliped endites, and have a much longer distal antennule article than the present species, more than twice ( H. trapezoida ) or three times ( H. longa ) as long as wide, compared with less than 1.5 times as long as wide in H. sima .

Hamatipeda sima is known only from the type-locality off Tasmania (see above).

Genus Paratyphlotanais Kudinova-Pasternak & Pasternak, 1978