Kalliapseudes obtusifrons ( Haswell, 1882 )

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 : 25-32

Kalliapseudes obtusifrons ( Haswell, 1882)

Figures 16–21

Apseudes obstusifrons Haswell, 1882 ; – Kalliapseudes obtusifrons Drumm & Heard, 2006 , 29–38, figs 1–4 (redescription, literature).

Material examined. A total of 684 individuals were examined from 65 samples, including 361 females (71 with oostegites, 75 with brood pouches), 141 males, 100 juveniles and 82 mancae. Samples were from West of Cape Otway to Port Philip Bay (depths from 9 to 124 m), Port Phillip Bay itself(15to 20 m), Western Port (2 to 19 m), East of Wilson’s Promontory (11 to 40 m), and the Gippsland coast (22 to 29 m), thus ranging from 142.03°E to 148.7°E, and variously between 38.24°S to 40.4°S. Substrata included mud, but mainly fine to coarse sands, to sandy gravel and shell. Numbers per sample ranged from 1 to 141 specimens. A selection of the samples examined is listed in Appendix 1. Numerous further samples held in the collections of Museum Victoria and confirmed as this species were not examined in detail .

Remarks. Kalliapseudes obtusifrons was originally known from Port Jackson, New South Wales (33.85°S 151.27°E), and the species remained somewhat enigmatic until Drumm & Heard (2006) rediscovered a syntype (designating it the lectotype) and valuably redescribed a further specimen – an ovigerous female collected from Cabbage Tree Island, New South Wales (31.95ºS 152.59ºE) (these authors also gave an identification key to the Australian species of Kalliapseudes ). These had been the only known specimens of this species. It was therefore of some surprise to find K. obtusifrons common throughout the Bass Strait.

The large amount of material available has enabled us to confirm the description of the female given by Drumm & Heard (2006) and to supplement that description where their material was damaged, to describe the dimorphism of the male, and to examine intraspecific variation in some meristic characters across the width of the Bass Strait.

Supplementary description of female ( Fig. 16). Antennule ( Fig. 17A) main flagellum with 7 to 10 segments, accessory flagellum with 3 or 4 segments, both with three distal setae; antenna ( Fig. 17B) first article with large apophysis with 4 to 6 plumose setae, squama with 4 to 7 simple setae, third article with two inner plumose setae, fourth article fused to fifth; flagellum of 6 segments, distal segment with four distal setae.

Cheliped ( Fig. 18A) basis with two longer and one shorter ventrodistal setae. Pereopod 1 ( Fig. 19) basis with group of ventrodistal simple setae, exopodite with three distal setae; ischium with ventral seta; propodus with 4 to 6 ventral propodal spines. Pereopod 2 ( Fig. 20A) with group of long subdistal ventral setae on basis. Pereopod 6 ( Fig. 20E) basis with 4 to 6 plumose setae on ventral margin.

Pleopod ( Fig. 20F) basis with 3 to 5 plumose seta on outer margin. Uropod endopod filiform, 2.7 times as long as pleotelson, of about 19 segments.

Dimorphism of male. Antennule ( Fig. 18C) peduncle article 3 and 4 shorter than wide, main flagellum with 8 segments, segments 2 to 5 each bearing distal row of four or five aesthetascs. Cheliped ( Fig. 18B) basis swollen, as long as wide, with corrugated ventrodistal margin; merus with ventral and distal margins corrugated; carpus twice as long as wide, with parallel ventral rows of filtering setae increasing in length distally; propodus robust, ventral margin corrugated in distal two-thirds, palm of chela as long as wide, with row of five plumose filtering setae as long as width of palm. Fixed finger about half length of palm, cutting edge with corrugated triangular distal apophysis and smooth triangular tooth-like proximal apophysis; dactylus cutting edge with proximal triangular tooth-like apophysis, distally corrugated.

Note: Drumm & Heard (2006) describe a “distinct line of fusion” on the cheliped carpus; this would be a stress line in the cuticle related to the internal proximal attachment of the caudal carpus muscle, as seen elsewhere in Apseudes bruneinigma Bamber, 1998 (q.v.) and Pakistanapseudes goofi Bamber & Sheader, 2003 ( Bamber & Sheader, 2003, fig. 4A). It was not observed in any of the Bass Strait K. obtusifrons material.

Morphometric variation. As mentioned above, the large amount of material from the Bass Strait has allowed observation of variation in certain meristic characters.Variations were found in the numbers of segments in the antennule flagella (the NSW specimen of Drumm & Heard, 2006, had 10 segments in the main flagellum, 4 in the accessory flagellum; Fig. 17A shows an example of a main flagellum of 7, accessory flagellum of 3), in the number of squama setae (the NSW specimen had 7, the example in Fig. 17B shows 6), in the number of pereopod 1 propodus ventral spines ( Fig. 19 shows an adult range of 4 to 6, and a manca with 3), in the number of pereopod 1 exopodite setae (the NSW specimen had 2, most Bass Strait specimens had 3, as in Fig. 19A), and in the number of pleopod basis setae (the NSW specimen had 4, Bass Strait juveniles had 1 to 2, Bass Strait adults had 3 to 4 or once 5, e.g. Fig. 20F).

When those features with sufficient variation are plotted across the east-west range of the Bass Strait material, a distinct trend is revealed: the number of ventral propodal spines in adults ( Fig. 21A) and the number of squama setae ( Fig. 21B) show either a decline from east to west, or a step somewhere around 147°E (east of Wilson’s Promontory). An identical trend is shown in the number of ventral propodal spines in juveniles (not figured). A step change around 147°E may represent a general separation of two populations, possibly partially isolated by hydrographic conditions, as has been shown in other crustaceans with intraspecific meristic variation between populations (e.g. Henderson et al., 1990); there would then be no reason why the New South Wales specimens should continue this trend directly, as they would again be a semi-isolated population. Intraspecific ranges in meristics in other species of Kalliapseudes were discussed by Bamber et al. (2003), who found increases in the number of accessory flagellum segments and the number of squama setae in Kalliapseudes makrothrix Stebbing, 1910 , K. gobinae Bamber, 1999 and K. tomiokaensis Shiino, 1966 , but inrelation to size (larger in larger individuals), and based on much smaller samples. The patterns found here for K. obtusifrons are not size-related.

The adult female to male sex ratio of all the material examined was 2.6:1.