Bicornucandona fineganensis, Külköylüoğlu, Okan, Gibson, Randy, Diaz, Peter H. & Colin, Jean-Paul, 2011

Külköylüoğlu, Okan, Gibson, Randy, Diaz, Peter H. & Colin, Jean-Paul, 2011, Bicornucandona gen. nov., sp. nov. (Crustacea, Ostracoda) from Finegan Springs (Texas, U. S. A.), Zootaxa 3059, pp. 47-58 : 50-56

Bicornucandona fineganensis sp. nov.

( Figs 2–6 )

Material examined. Holotype: (one dissected male), Finegan Springs (29°54'067ʺN – 100°59'924ʺW), Devils River State Natural Area, Texas Parks and Wildlife Department, Val Verde County, Texas, collected by Randy Gibson.

Allotype (one dissected female) and about 40 paratypes (13 males, 17 females, 10 juveniles), 25 February 2010. Soft body parts dissected in lactophenol; empty valves kept in a micropalaeontological slide (no: OK-TX- 20100225-01-03).

Allotype: One female from Blue Hole Springs (29°53'630ʺN 100°59'672ʺW), Dolan Falls Preserve, The Nature Conservancy, Val Verde County, Texas, collected by Randy Gibson, 11 September 2008.

Dissected paratypes: two males and one female from the type locality and Blue Hole Springs, respectively. (no: OK-TX-20100225-04-06).

Additional material examined. 1) Four females from Blue Hole Springs collected on 11 September 2008; kept in 70% ethanol.

2) Three individuals (two females, one male) from Finegan Springs, 18–19 August 2009; kept in 70% ethanol.

Paratypes: more than 60 individuals collected from the sampling sites listed above. Leg. R.G. and P.D.

Non-dissected paratypes: ca. 30 individuals (males, females, juveniles) from the type locality kept in 70% ethanol deposited at the United States Museum of Natural History (Smithsonian Institution). USNM, Washington, D.C., catalogue number 1145121.

Description. Male:

Measurements: L = 0.85–0.90 mm (n = 12), H (LV) = 0.52–0.59 mm, H (RV) = 0.44–0.50 mm, W = 0.28–0.30 mm. LV overlapping RV ( Figs 2 A–E) along the entire valve margin.

RV almost trapezoidal in shape with a slightly concave dorsal margin in the middle. Valve surface pitted, with setae ( Fig. 3 A). Medium sized, trapezoidal candonine species with two horn-like prolongations on the mid-dorsal side of LV ( Figs 3 B–D). Internal view of both valves: inner calcified lamella wide both, anteriorly and posteriorly; five to six muscle scars located in the median part of the valves ( Fig. 3 E). Color translucent to opaque white ( Fig. 3 F). In dorsal view: carapace laterally compressed. Hinge adont. Outer marginal areas of both valves smooth in the areas pitted and covered with conspicuously long and stiff setae with normal pore openings.

Antennula (A1): ( Fig. 4 A). Seven-segmented. Two long and smooth setae on first segment (protopodite) well developed. Rome organ absent or tiny reduced as usual for the subfamily Candoninae . Aesthetasc ‘ya’ on the terminal segment reduced or not seen.

Antenna (A2): ( Fig. 4 B). Four-segmented, penultimate segment undivided. Exopod with three setae (one long, two very short); long seta barely extending to the end of the first endopodal segment, one of the two short seta strongly curved. Only one short t-seta present, about the size of terminal segment, not transformed into sensory bristles.

All three z -setae (z1-3) small, barely reaching to the end of the terminal segment. G1 and G3 claws conspicuously and equally long, reaching about the combined length of the three distal segments of A2. G2 claw short, about 1/3 as long as G1. GM claw extends about to 2/3 of G3. Gm a slender seta reaching ca 2/3 of GM seta. Aesthetasc Y well developed, reaching about 70% of the first endopodal segment. y2 short, about the length of the penultimate A2-segment. Setae y1 and y3 not seen.

Rake-like organ with eight to nine teeth ( Fig. 4 C).

Mandibula (Md): ( Fig. 5 A). Md palp four-segmented. Interiorly, first segment bearing two short (one smooth and one plumosed S1 barely reaching 1/3 the length of the S2 seta.) and two long setae (one plumosed S2 seta and one smooth seta). α seta smooth and short, about 1/3 of S2. No setae on outer edge of this segment. Second segment with a group (3+1) of setae interiorly. β seta present, medium sized, about the length of the outer edge of the corresponding segment. Two setae present on the outer edge; 1 long seta reaching to about midpoint of the claws, the other seta extending to about the tip of the terminal segment.

Third segment externo-distally with two long setae (both barely reaching to the end of the terminal claws). Distally, one short smooth gamma (γ) seta and one short seta exceeding the terminal segment. Interio-distally, one long smooth seta reaching to midpoint of the terminal claws. Both second and third segments bearing two setae externodistally. Terminal segment cylindrical, ending with two long claws. Mandibular coxa with about seven well developed teeth and one short seta distally.

Maxilla (Mxl): ( Fig. 5 B). Mxl-palp trapezoidal, with two claw-like, two smooth and one short setae on terminal segment. Penultimate palp-segment with three long setae reaching almost to midpoint the terminal claws. First endite (masticatory process) with eight short claw-like setae, second endite with five setae and third endite with four smooth (two normal and two smooth teeth bristles) and 1 short setae. Vibratory plate with 21 well developed and plumosed setae.

T1: ( Figs 5 C, D). Prehensile palps on endopod asymmetrical, left palp slender with an elongated finger and two equally-sized claw-like setae ( Fig. 5 C). Right palp anteriorly broadened with two setae ( Fig. 5 D). 2 a, 1 c, and 1d setae present with equal length, but seta b absent. Exopod with one short plumose seta extending the length of palp. Masticatory process distally with about 13 claw-like setae.

T2 (walking leg): ( Fig. 6 A). Five-segmented. First (basal) segment (protopodite) with one short seta almost equal in size to this segment. Second segment with one seta of about the length of the third segment. Third segment with one seta slightly longer than this segment. Fourth (penultimate) segment has two setae (long seta twice the length of the terminal segment while short one extending to about midpoint of terminal segment). Fifth (terminal) segment with 1 short seta about half as long as the segment, and a claw, which is longer than the three combined distal segments. About 1/3 of the claw serrated.

T3 (cleaning leg): ( Fig. 6 B). Four-segmented (penultimate segment undivided) with three setae (dp, d1, d2) on basal segment. dp seta long, reaching the end of the second segment. Setae d1 and d2 about the same size, not plumose. Second segment without any seta. Seta g on the third segment reaching about the length of that segment. Terminal segment with three setae arranged in length as h3> h2> h1. Seta h1 straight and about twice as long as the terminal segment. Seta h2 shorter, about 2/3 as long as h3. Seta h3 reaching to midpoint of the second segment and weakly plumose.

Uropod (furca) ( Fig. 6 C) with two weakly plumose claws of about the same size and slightly curved. Anterior seta tiny, sometimes not seen, about 1/5 the size of the posterior seta. Posterior seta slender and short in size to about 1/4 that of the terminal claw. Urapodal attachment (Ua) simply branched.

Zenker organ: with well developed 5+2 whorls of spines ( Fig. 6 D).

Hemipenis: Lobe ‘a’ (outer lobe) squared, and flattened distally. Lobe ‘b’ (inner lobe) distally enlarged and rounded ( Fig. 6 E). Lobe ‘h’ (medial lobe) ventrally triangular, broadly rounded inwards. ‘M’ process dorsally elongated, slightly curved and pointing to the ‘h’ lobe.

Female: Carapace very similar in shape, size and structure to that of the male but postero-dorsal margin steeper than the anterior one. Genital lobe rounded without any appendages. T1 normally developed not transformed into clasping organs but note to segmentation ( Fig. 5 E). Exopod with two setae. Endopod terminally with three setae ranged in length as h2> h1> h3. All other soft parts similar to that of the male.

Ecology. So far, the individuals of the species Bicornucandona fineganensis gen. nov. sp. nov. have been found drifting out of limestone spring orifices with relatively warm, oxygenated, and neutral (pH 7.0 – 7.2) waters ( Table 1 ). This suggests that the species is probably a stygobiont, inhabiting underground waters.

Figures

FIGURE 2. SEM photographs of Bicornucandona fineganensis sp. nov. A, B, female: Left and right valves, respectively. C – E, male: C, Dorsal view; D, Ventral view; E, Anterior margin from dorsal view (Scale: 100 µm).

FIGURE 3. SEM photographs of Bicornucandona fineganensis sp. nov. A – F, male. A, Left valve interior view (Note mid-ventral area broken); B, External view of right valve; C, Close view of a single horn from dorsal view along with normal pore openings; D, Left valve external view of horn-like structures dorsally; E, Muscle scars in interior view; F, Two horns on the left valve, dorsal view. (Scale: A, F: 100 µm; B – E: 10 µm).

FIGURE 4. Bicornucandona fineganensis gen. nov., sp. nov. holotype (male L = 0.90 mm): A, A 1; B, A 2; C, Rake-like organ.

FIGURE 5. Bicornucandona fineganensis gen. nov., sp. nov. (A – D, male; E, female). A, Md-palp; B, Max-palp; C, left prehensile palp; D, right prehensile palp; E, T 1 (arrow indicating segmentation). (Scale: A – B: 100 µm; C – D: 10 µm; E: 20 µm).

FIGURE 6. Bicornucandona fineganensis gen. nov., sp. nov. (male). A, T 2; B, T 3; C, Uropod (Fu); D, Zenker organ; E, Hemipenis; (Scale: 25 µm).