Austromesocypris bluffensis, Karanovic, Ivana, Eberhard, Stefan & Perina, Giulia, 2012

Karanovic, Ivana, Eberhard, Stefan & Perina, Giulia, 2012, Austromesocypris bluffensis sp. n. (Crustacea, Ostracoda, Cypridoidea, Scottiinae) from subterranean aquatic habitats in Tasmania, with a key to world species of the subfamily, ZooKeys 215, pp. 1-31 : 5-8

Austromesocypris bluffensis sp. n. Figures 8A, B9-11

Material examined.

Holotype, female (TMAG 6206) Damper Cave, 43°30'S, 146°35'E, Precipitous Bluff, 90 km SW of Hobart, Tasmania, Australia, Site A, main stream, 30 m from entrance, 14 May 2011 (dissected on one slide), collected by R. and S. Eberhard, G. Perina, S. Catomore.

Diagnosis.

Ostracods with smooth, transparent shell densely covered with setulae. Dorsal margin straight, anterior and posterior margins almost equally wide. Calcified inner lamella narrow. A1 with fused third and fourth segments. A2 with only two short swimming setae and two t-setae. Md-palp with pappose γ-seta. L5 with one a-seta and one d-seta. L6 with d2-seta, short e-seta, second and third endopodal segments fused, and long terminal claw. UR with row of long, strong setulae along posterior margin; both distal claws strong with strong spines; anterior seta long. Rami almost symmetrical, only one ramus with slightly shorter setulae along posterior margin. Genital field with one clear thumb-like projection.

Etymology.

The species is named after its type locality.

Description of female.

Carapace (Figs 8A, B; 9A). Rectangular in lateral view; 0.58 mm in length. Greatest height situated around middle length, equalling 0.26 mm, or 45% of length. Valves clearly asymmetrical, RV being shorter than left one. Dorsal margin straight on almost entire length, rounding towards posterior end and inclined with small recess towards anterior end. Both anterior and posterior ends rounded, anterior end more so and slightly wider than posterior one. Ventral margin straight or very slightly concave. Anterior and posterior inner calcified lamellae narrow. Margina l pore canals short, except in ventral region where enlarged. Surface densely covered with relatively short hair-like setae.

A1 (Fig. 9B, C). First segment hirsute, anteriorly with only one pappose seta, reaching middle length of following segment; posteriorly with two, almost equally long, pappose setae originating close to each other and near distal margin of segment. Wouters organ not observed. Following segment with very short Rome organ posteriorly and one pappose seta anteriorly, reaching middle of following segment. Above this seta cluster of setulae present. Third segment compound, representing fused segments three and four; point of their fusion clearly marked by one short pappose seta, which almost reaches distal margin of following free segment. Distal margin of fused segment with one posterior, short and smooth seta and one long, also smooth seta anteriorly. This seta as long as length of all segments combined. Segment following fused segments (fifth segment) very short with two long and smooth setae anteriorly and one shorter seta posteriorly. Penultimate segment with total of four anterior setae, all situated very close to each other, three being longer than length of all segments combined and one equalling 1/3 of their length. Terminal segment with one long and two shorter setae, this segment with long aesthetasc y1 being eight times longer than terminal segment. Length ratios of last four segments equalling 1.8: 1: 1.5: 1.

A2 (Fig. 10A). Coxa with three pappose, equally long setae: one situated more proximally (externally) and two more distally (internally) on segment. Coxa with three rows of small setulae. Basis laterally with cluster of setulae and one anterior seta, which reaches distal end of first endopodal segment. Exopod representing small plate with three setae: most anterior one distally pappose and reaching distal margin of first endopodal segment; middle one also pappose and much shorter; most posterior one even shorter and also smooth. Endopod 3-segmented. First segment with two strong setulae along anterior margin and row of short setulae antero-distally; aesthetasc Y situated in middle of posterior margin and reaching distal end of segment; postero-distal seta pappose and extends beyond middle of second endopodal segment. Two short swimming setae situated antero-distally on segment and only one reaches 1/3 of second endopodal segment. Second endopodal segment with cluster of setulae mid-laterally; seta on middle of anterior margin distally pappose and reaches distal end of segment. Second endopodal segment posteriorly with two short aesthetascs: y1 situated more proximally and y2 at distal margin. Same segment postero-medially with three t-setae: t1 distally pappose and shorter than t2 and t3. Second endopodal segment with three smooth and equally long z-setae on distal margin, all reaching middle of terminal claws. G2 claw equalling 2/3 of G1 claw. G1 and G3 equally long and only slightly shorter than first endopodal segment. Terminal segment short with GM claw equalling 70% of first endopodal segment; Gm claw being 2/3 of GM. Same segment with one additional thin seta which is as long as Gm claw; aesthetasc y3 of same length and proximally fused with one thin seta.

Forehead and lips (Fig. 11D). Hirsute with numerous sclerotized rods and rake like organ carrying about six blunt teeth.

Md (Fig. 10C). Exopod short carrying five plumose, vibratory setae. Palp 4-segmented. First segment posteriorly with three setae, one smooth and other two with one row of long and strong setulae; one of these setae bent. Alpha seta, usually present on this segment, not observed. Second segment anteriorly with three equally long pappose setae not reaching distal margin of following segment; posteriorly with three long, smooth setae, one shorter seta with setulae along one margin, and one short and plumed seta (β-seta). Penultimate segment anteriorly with one very short seta and two long and smooth setae each exceeding distal end of terminal segment; posteriorly with total of four setae: two long and two shorter, one of which half as long as long setae, other ¼ length of these setae; γ-seta plumed, exceeding distal end of terminal segment. Terminal segment elongated (2.5 times longer than wide) with four distally curved claws and one seta half as long as claws.

Mxl (Figure 9D). Palp 2-segmented. First segment with three pappose and two smooth setae, all situated close to outer margin. Terminal segment 1.8 times longer than wide, with two claws (one fused with segment) and four setae. First endite distally with two long, pappose setae and five short claws; proximally with two short and smooth setae. Second endite with four short claws. Third endite with four claws (one fused with segment) and cluster of short setulae on anterior margin.

L5 (Fig. 10B). Exopod with two plumose vibratory setae. Endopod with three distal pappose setae, two being twice as long as third. Protopod with one pappose a-seta, one pappose d-seta and six distal pappose setae.

L6 (Fig. 11C). Basal segment (basis) with short pappose d2-seta and marginal rows of setulae. First endopodal segment with long anterior setulae, and three medial rows of shorter setulae; same segment antero-distally with short and pappose e-seta. Following segment compound, representing fused second and third segments, with f-seta near middle of anterior margin and distally with two setae (one being g-seta) and row of marginal setulae. Terminal segment with two thin setae (h1 and h3) and one strong claw (h2); latter gently serrated and 0.72 times as long as endopodal segments combined.

L7 (Fig. 11E, F). Composed of three segments plus terminal pincer. First segment with three long, pappose setae (d1, d2 and dp). Second segment with pappose e-seta reaching half length of following segment. Third segment compound, representing fused endopodal segments two and three, with f-seta near middle of anterior margin; g-seta absent. Terminal segment reduced and transformed into pincer organ. Seta h1 very thin and curved, h2-seta claw-like and distally pappose, seta h3 normal and almost as long as penultimate segment.

UR (Fig. 11A). Posterior margin with groups of long and strong setulae; posterior seta situated close to distal margin, being pappose and more than half as long as posterior claw. Posterior claw only slightly shorter than anterior one; both claws strongly serrated. Anterior seta distally pappose and as long as anterior claw. Rows of setulae on posterior margin of one ramus slightly weaker. Length ratios between anterior margin of ramus and anterior and posterior claws equalling 2.9: 1.1: 1.

Attachment of UR (Fig. 11B). Distally bifurcate, with no additional ventral or dorsal branches.

Genital field (Figure 11A) with clear thumb-like projection (indicated by arrow on Figure 11A).

Males.

Not known.

Remarks.

Austromesocypris bluffensis sp. n. stands apart from all other species of the genus in having a completely flat dorsal margin of the carapace and almost symmetrical UR. In addition, it differs from the New South Wales species, Austromesocypris berentsae Martens, De Deckker and Rossetti, 2004, in having only one segment on the A1 fused. Austromesocypris berentsae is the only species in the genus that has two segments fused (3+4, 5+6). Austromesocypris bluffensis differs from Austromesocypris australiensis (De Deckker, 1983) by having structurally similar posterior setae on both UR. Only Austromesocypris australiensis , among all species of the genus, has one seta transformed into a strong claw, the other being seta-like. The one previously described species from Tasmania, Austromesocypris tasmaniensis (De Deckker, 1983), has much stronger spines along the posterior margin of the UR. The UR of the new species is the most similar to Austromesocypris berentsae , but the former species has shorter spine-like setae along the posterior margin of the ramus. It appears that the gamma-seta on the Md-palp in Austromesocypris berentsae is not pappose (see Martens et al. 2004, Fig. 3), while it is in the other three species. There are other differences in the chaetotaxy of the Md-palp between the new species and the other three, namely Austromesocypris bluffensis has four setae postero-distally on the penultimate segment, Austromesocypris berentsae has two, while the two species described by De Deckker (1983) have three. Moreover, there are only two setae antero-distally on the same segment in Austromesocypris bluffensis , while all other species have three. It is interesting to note that the S2 seta on the first segment of the Md-palp is turned upwards only in Austromesocypris bluffensis . We are uncertain if this character has any taxonomic significance, or whether this seta was twisted during slide preparation. However representatives of many Cyprididae subfamilies ( Cypridopsinae , Cyprinotinae , Herpetocypridinae ) and some Candoninae and Cyclocypridinae have the seta S2 similar to that of Austromesocypris bluffensis (I. Karanovic personal observation).