Diasterope wirraka, Syme, Anna E. & Poore, Gary C. B., 2006

Syme, Anna E. & Poore, Gary C. B., 2006, Three new ostracod species from coastal Australian waters (Crustacea: Ostracoda: Myodocopa: Cylindroleberididae), Zootaxa 1305, pp. 51-67 : 56-60

Diasterope wirraka new species

Figures 3 , 4

Material examined.— Holotype: NMV J53210 one adult female on slide and in alcohol. Paratypes: NMV J53211 one adult male on slide and in alcohol; NMV J53212 one adult female on slide and in alcohol, NMV J53213 one adult female on slides and in alcohol.

Type Locality.—Eastern Bass Strait, Victoria, Australia. 15.3 km ESE of eastern edge of Lake Tyers. 37°53.23' S, 148°15.24' E, benthic, 43 m. Collected by N. Coleman using Smith­McIntyre grab. Collection date: 1 February 1991.

Distribution.—Known only from type locality.

Diagnosis.—Article 3 of first antenna with 5 dorsal setae; mandible basale with 3 (male) or 5 (female) dorsal setae; seventh limb with 12 setae.

Description.—Adult female. NMV J53210 . Carapace oval and slightly broader posteriorly, inner end of incisur at valve midheight, posterior end evenly rounded, carapace length 1.64 mm, height 0.84 mm. Infold: rostrum with 60 setae anterior and dorsal to list, anteroventral infold with 20 setae between list and valve edge, narrow list continuing ventrally with about 40 setae on list, list broadening slightly at posterior infold with 21 broad triangular transparent setae and 23 smaller setae placed between. Selvage: fringe of hairs at inner end of ventral margin of incisur. Vestment: anterodorsal corner of vestment proximal to infold with clusters of long spines.

First antenna: article 2 with 1 spinous dorsal seta and 1 lateral seta. Article 3 with 1 short ventral seta and 5 dorsal setae; first 2 with longer spines and remainder with short marginal spines. Article 4 with 1 dorsal seta with short marginal spines and 2–3 ventral setae. Article 5 with sensory seta with 1 short proximal and 6 terminal filaments. Article 6 with bare medial seta, 1.5x length of a­claw. Article 7 with a­claw, b­seta with 4 marginal filaments, c­seta with 4 marginal filaments. Article 8 with minute peg d­seta, e­seta bare with blunt tip, f­seta bent dorsally with bifurcate tip, g­seta with 4 marginal filaments.

Second antenna: protopod with bare distal medial seta. Endopod with 3 articles, end article with terminal filament. Exopod: article 2 seta with marginal spines, reaching ninth article. Articles 3–7 with long setae with marginal spines. Article 8 with basal spine and long seta with marginal spines. Article 9 with larger basal spine, 1 shorter seta and 2 long setae with marginal spines.

Mandible: coxale endite missing. Basale endite with 4 spinous end setae, 3 triaenid setae with 5–6 paired spines excluding terminal pair, 2 dwarf setae of equal length and small glandular peg. Basale: ventral margin with 1 smaller triaenid seta with 2 pairs of spines excluding terminal pair, proximal to U­shaped boss; dorsal margin with 5 setae at midlength and 2 long terminal setae, equilength, with spines. No hairs/spines on medial side of basale. Exopod with hirsute tip and 2 subterminal setae, exopod length approximately 0.4 of dorsal margin of first endopod article. Endopod article 1 with 3 long ventral setae (1 with short spines, 2 with long spines). Endopod article 2: ventral margin with 3 long terminal setae with short spines, dorsal margin with stout a­, b­, c­, and d­setae, 2 slender seta proximal to a­seta; medial side with 9 cleaning setae, and 1 long g­seta distal to base of d­seta; lateral side with 1 long e­seta between b­ and c­ setae and 1 long f­seta between c­ and d­ setae. Endopod article 3 with stout dorsal claw, 4 stout spinous setae and 1 slender shorter spinous seta.

Maxilla (fourth limb): epipod missing, endites folded and obscured. Basale spinous on medial side with 1 proximal seta at midheight. Ventral margin with 5 setae near midlength and 1 long spinous terminal seta. Dorsal margin with 2 proximal setae, 2 middle setae and 1 distal seta. Endopod article 1 with ventral spines, short alpha seta and long beta seta. Endopod article 2 with long terminal seta.

Fifth limb: missing on holotype. For paratype NMV J53212 , comb with long exopod seta, 4 shorter lateral setae near ventral margin of comb. Sixth limb: anterior margin with seta at each endite suture, lateral flap of skirt with 4 setae, ventral margin with 14 setae with spines, posteroventral corner with 6 plumose setae. Seventh limb: with 12 setae, each with 3 bells. Combs forming obtuse angle, each comb with 8 teeth.

Furca: each lamella with 7 claws and setae decreasing evenly in size, and 1 lateral seta pointing posteriorly. Bellonci organ with no obvious sutures. Medial eye with 3 pigmented sections. Lateral eye with 14 ommatidia. Lips: presence/absence unable to be determined. Posterior of body: thumb­like dorsal process with long spines at tip and shorter spines at mid­height. Reproductive organs: presence/absence unable to be determined. Gills: partly obscured and distorted by embryos in marsupium, but appear well­developed. Embryos: holotype with 6 embryos in marsupium; length of typical embryo 0.33 mm.

Adult male. NMV J53211 . All features compared to adult female; important differences noted here: carapace length 1.50 mm, height 0.76 mm. First antenna: article 5 with sensory seta with robust stem and many filaments. Article 7 with c­seta broken from both antennae. Article 8 with f­seta with 8 marginal filaments and g­seta with 7 marginal filaments. F­seta not particularly long, approximately equal to length of first antenna. Second antenna: endopod with 3 articles. Article 2 with 4 setae, article 3 narrower than other articles, recurved, with 1 proximal seta. Mandible: basale dorsal margin with 3 setae at midlength, endopod article 2 with 3 dorsal proximal setae. Lateral eye: with 18 ommatidia. Reproductive organs: small oval with vas deferens leading to copulatory structure. Posterior of body: rounded posterior process.

Remarks.— The existing diagnosis of Diasterope includes a mandible exopod length greater than 50 percent of length of dorsal margin of endopod article 1. Diasterope wirraka has a relative exopod length of only 40%. However, the species fits more closely into Diasterope than into other genera and is thus included in this genus here. As noted above, a phylogenetic analysis is in progress and may alter the available genera of the Cylindroleberididae ; thus, a formal change to the diagnostic features of Diasterope is not presented here.

Diasterope wirraka is similar to D. grisea ( Brady, 1898) ( New Zealand) but differs in the following characters: carapace smaller (adult female 1.64 mm compared to 2.64 mm), article 3 of first antenna with 5 (not 6) dorsal setae; mandible basale of female with 5 (not 3) dorsal setae, male f­seta of first antenna of similar length to g­seta (not twice as long), and male carapace with no posterior row of hairs. D. wirraka is also similar to D. schmitti Kornicker, 1975 ( Antarctica) in the number of dorsal setae on the mandible basale (5) but differs in the following characters: carapace much smaller (adult female 1.64 mm compared to 3.51 mm), article 3 of first antenna with 5 (not 6–7) dorsal setae, seventh limb with 12 (not 31) setae. No males are known for D. schmitti . D. wirraka c an be differentiated from D. procax Kornicker & Iliffe, 2000 ( Bahamas) , D. pilosa Poulsen, 1965 (Northeast Pacific) and D. bisetosa Poulsen, 1965 (Red Sea) by the number of dorsal setae on the mandible basale (5 compared to 1). Comparisons have not been made with those species for which only juvenile males are known, D. canina Poulsen, 1965 and D. tenuiseta Poulsen, 1965 , both from the West Indies.

The adult male carapace is lacking a posterior row of hairs. Presence of this row of hairs is common in males of the subfamily. The relatively short f­seta is in contrast to most known males of the subfamily, which have very long c­ and f­setae (twice length of first antenna).

Species of Diasterope have a disjunct distribution, known from the Red Sea, northwest Atlantic, northeast Pacific and New Zealand to Antarctica. D. wirraka has morphological similarities with species from New Zealand and Antarctica, and its discovery extends the distribution of this genus to southeast Australia.

Etymology.—“ Wirraka ” is an Australian aboriginal word from the Wemba Wemba language of southeastern Australia, meaning “to swim.”

Figures

FIGURE 3. Diasterope wirraka, new species, adult female holotype NMV J 53210; A, carapace; B, first antenna, left, m. v., base of medial seta on sixth article and g­seta on 8 th article are shown as circles, d­seta of 8 th article is a small peg on lateral side represented by dotted lines (110 X); C, second antenna, right, m. v., setae on exopod articles 3 ­ 9 not shown (87 X); D, mandible, left, m. v., one seta on basale endite broken, basale terminal setae partially shown, bases of ventral endopodial setae represented by circles, medial seta on endopod article 2 and terminal setae on article 3 not shown (except for terminal claw) (128 X); E, maxilla, left, m. v., epipod broken, endites obscured (157 X); F, sixth limb, left, m. v. (88 X); G, seventh limb (115 X); H, furca, right lamella (97 X); I, medial eye and Bellonci organ (65 X); J, lateral eye (97 X). Adult female paratype NMV J 53212, K, fifth limb comb (136 X).

FIGURE 4. Diasterope wirraka, new species, adult male paratype NMV J 53211, A, carapace; B, first antenna, right, m. v., filaments on s­seta not shown, base of medial seta on sixth article shown as circle, d­seta tiny peg (not shown), c­seta missing, base shown as circle (108 X); C, endopod of second antenna, right, m. v. (113 X); D, posterior of body from left side showing copulatory organ and first claw of furca (48 X).