Candona quasiincarum, Karanovic, Ivana & Datry, Thibault, 2009

Karanovic, Ivana & Datry, Thibault, 2009, Overview of Candoninae (Crustacea, Ostracoda) of South America and the West Indies, with the description of two new species and one new genus, Zootaxa 2267, pp. 1-25 : 13-17

Candona quasiincarum sp. nov.

( Figures 6 , 7 )

Etymology: The species is named after Candona incarum (Moniez, 1899) with the species name prefixed by Latin adverb “quasi”, meaning “appearing as if, like”, referring to the close similarity between the two species.

Type material. Holotype female (dissected on one slide, TMAG G5901), 7 paratype females (all in alcohol, TMAG G5902)

Type locality: C1BA, Chile, Region XII: Magallanes and Antártica Chilena Region, Madre de Dios Archipelago, Condor lake area, 18/01/2006, T. Datry & T. Lefebure, 50° 17' 28,604 S / 75° 15' 12,924 W.

Other material: 10 females (in alcohol, TMAG G5903) from: SN5 AB ( Chile, Region XII: Magallanes and Antártica Chilena Region, Madre de Dios Archipelago, Seno nord area, 04/02/2006, T. Datry & T. Lefebure, 50° 15' 30” S / 75° 16'10” W; 6 females (in alcohol, TMAG G5904) from PAC Ben 2 ( Chile, Region XII: Magallanes and Antártica Chilena Region, Madre de Dios Archipelago, Pacific cave area, 25/01/ 2006, T. Datry, 50° 22' 35” S / 75° 27' 25” W; female (on slide, TMAG G5905), 4 females (in alcohol, TMAG G5906) from: TAIB ( Chile, Region XII: Magallanes and Antártica Chilena Region, Madre de Dios Archipelago, Tarlton island area, 05/02/2006, T. Datry & T. Lefebure, 50° 25' 06” S / 75° 26' 55” W; 2 females (on slide, TMAG G5907 & TMAG G5908), 1 female in alcohol ( TMAG G5909) from: 1B Benthos ( Chile, Region XII: Magallanes and Antártica Chilena Region, Madre de Dios Archipelago, Guarello base camp area, 06/01/2006, T. Datry & T. Lefebure, 50° 22' 05” S / 75° 20' 58” W.

Diagnosis. Species with asymmetrical carapace, LV being considerably larger than the RV. Greatest H around the middle, posterior and anterior setae on caudal ramus long.

Description. Dorsal margin evenly rounded, with greatest H situated around middle, equaling 50 percent of total L ( Figure 6 A). Ventral margin concave, anterior and posterior margins rounded, the anterior one slightly wider than the posterior one. LV overlapping RV on all free margins, dorsally with a flange, which is weakly developed ( Figure 6 B). In dorsal view, greatest W around mid-length ( Figure 6 C). Calcified inner lamella narrow, anteriorly 10 percent, posteriorly 8 percent of L. Marginal pore canals straight and relatively dense. Carapace surface without ornamental sculptures, covered only with Porenwarzen from which very short setae originate.

A1 ( Figure 7 E): 7-segmented. First segment with four setae. Second segment with one anterior seta reaching only end of following segment; second segment with one anterior and one posterior seta, anterior exceeding, while posterior reaching distal margin of fourth segment; fourth and fifth segments with two setae anteriorly and one posteriorly, posterior setae short, while anterior ones long; sixth segment with two posterior (two times longer than terminal segment) and two anterior, long setae, plus very short alpha seta. Terminal segment with two setae, one thin claw and aesthetasc ya which is 1.4 times longer than terminal segment. L ratio of endopodal segments 1: 1: 1: 1: 1.2: 1.8.

A2 ( Figure 7 A): exopod consisting of plate with one long and two short setae. Two setae on distal end of first endopodal segment subequally long. All t-setae present and subequally long, exceeding by far terminal segment. Seta z1 transformed into claw, slightly exceeding distal end of terminal segment, while z2 and z3 seta like and two times longer than z1. Claws G2, G1, G3 and GM subequally long and almost as long as other terminal claws. Claw Gm 1/3 shorter. All aesthetascs well-developed: Y reaching distal margin of first endopodal segment, y2 and y3 very short, y3 slightly shorter than Gm.

Rake-like organ ( Figure 7 B): with 7-8 strong teeth.

Md palp ( Figure 7 F): Palp 4-segmented. First segment with three setae observed. Second segment exteriorly with two long setae exceeding distal end of terminal segment, inner edge with variable number of setae in a group: 3+2 ( Figure 7 H), 4+2 ( Figure 7 G) and 5+2 ( Figure 7 F). Gamma seta smooth. Penultimate segment with three setae exteriorly and four setae distally. Terminal segment with one central claw, one exteriorly claw, and seta interiorly.

Mxl palp ( Figure 7 D): first segment three plumed and one smooth seta. Second segment with two claws and three setae.

T1 ( Figure 6 G): with only one a seta, both b and d setae present. Two setae in exopod. Masticatory process with about 10 seate.

T2 ( Figure 7 C): basal segment with one long seta d1; first and second endopodal segments with one seta each; penultimate segment with two setae. Terminal claw 1.2 times longer than three distal segments combined. Seta h3 twice as long as seta h1.

T3 ( Figure 6 F): basal segment with only d1 and dp setae. First endopodal segment bare, following segment not subdivided, seta g as long as segment. Terminal segment with three setae, all long, L ratios of h1, h2 and h3 setae 1: 1.5: 1.9.

CR ( Figure 6 E): all claws and setae well developed. Posterior seta situated on 20 percent of L of posterior margin, and as long as posterior claw. Anterior seta 1/3 of anterior claw. Posterior margin of CR proximally with group of setules. L ratio of anterior margin, anterior and posterior claws 1.4: 1. 3: 1. Caudal seta ( Figure 6 D) well developed. Genital field rounded without any process.

Dimensions. L of carapace varies from 0.57 mm to 0.92 mm (average 0.68 mm, n=9). Greatest H in all examined specimens varying between 48 percent and 51 percent of total L.

No males found.

Remarks and affinities. The following Candona Baird, 1845 species were recorded in South America: C. araucana Löffler, 1961 ; C. parva Daday, 1905 ; and C. incarum (Moniez, 1899) . Martens & Behen (1994) listed another five species: C. albida ( Dana, 1852) , C. annae Mehés, 1914 ; C. capsularis Klie, 1935 ; C. cyproides ( Daday, 1905) and C. pedropalensis Mehés, 1914 . Candona albida does not belong to the subfamily Candoninae at all, as on the figures provided by Dana (1853), the species is illustrated with the swimming setae on the antenna ( Dana 1852: Figure 10). Candona annae , C. capsularis and C. pedropalensis were transferred into the genus Typhlocypris Vejdovský, 1882 by Karanovic (2005a). Candona cyproides is characterized by the presence of the e, and f setae on T3, a posterior seta on the CR which is claw-like and attached at a very proximal position. The absence of the swimming setae and the appearance of the terminal segment of T3 place C. cyproides in the subfamily Candoninae , but the appearance of CR and Mxl palp (with a spatula-shaped terminal segment) place it in the family Cyprididae . Ekman (1908) described Candona pygmea from Sweden, another species with f seta on the cleaning leg, but this is not characteristic of other Candona species. Therefore the position of C. cyproides remains uncertain.

Candona quasiincarum sp. nov., like the other three remaining species of Candona recognized here from South America ( C. incarum , C. araucana , and C. parva ), has a 4-segmented T3 which makes them an easily recognizable group. The only species with this feature from outside South America is the Holarctic C. candida (O. F. Müller, 1776) . All South American species of the genus Candona belong into the candida - group, because the second segment of their Md palp bears an interior group of 5+2 setae. Although it is an important character, it is variable in C. quasiincarum , as there are specimens with 3+2 and 4+2 setae. In one animal, one Md palp carried 4+2, while the other one had 5+2 setae. It is also worth noticing that smaller specimens tend to have fewer setae on the palps. Variability in the number of setae in this place is also noticed in the genus Typhlocypris (see Karanovic 2005a).

Candona quasiincarum differs from the remaining species of Candona with 4-segmented T3, in the asymmetrical carapace, the LV being considerably larger than the RV. It differs from C. incarum also in having a much shorter posterior claw on the CR and a slightly different carapace shape: the greatest H in the new species is around the middle, while in C. incarum it is behind the middle, so the frontal margin is narrower than the caudal one. Candona araucana has a carapace shape which is similar to that of C. incarum , but the posterior seta on the CR is positioned more proximal on the ramus than in C. quasiincarum . In contrary to C. quasiincarum , C. parva has (in lateral view) a very wide posterior end of the carapace, the dorsal margin sloping down towards the anterior end, which is considerably narrower than the posterior one. The posterior seta on the CR is very short in C. parva . Candona candida has an almost straight posterior margin of the carapace. There are a few Candona species described from the Lake Baikal ( Mazepova 1990) with a 4-segmented cleaning leg, but their carapace shape is different, with many additional differences in the morphology of the soft parts.

Figures

FIGURE 6. Candona quasiincarum sp. nov.: Holotype (female): A, carapace, exterior view from the right side; B, LV, interior view (arrow showing flange); C, carapace, dorsal view; D, caudal seta; E, caudal ramus; F, T 3; G, T 1. Scales = 0.1 mm.

FIGURE 7. Candona quasiincarum sp. nov: A-F Holotype; G, H Female: A, A 2; B, rake-like organ; C, T 2; D, Mxl palp; E, A 1; F, Md palp; G, H, group of setae on the second segment of Md palp. Scale = 0.1 mm.