Schellencandona dui, Ma & Yu, 2018

Ma, Shunxin & Yu, Na, 2018, Freshwater ostracods (Crustacea) from Tiantong National Forest Park and Dongqian Lake, eastern China, with descriptions of two new species, Journal of Natural History 52 (27 - 28), pp. 1825-1868 : 1836-1840

Schellencandona dui sp. nov.

( Figures 7a–d , 8 )

[non] Schellencandona cf. belgica Kong et al., 2013: 167–169 , pl. I (7–8), fig. 2.

Type locality

North area of Dongqian Lake [29.785978º N, 121.652147º E, elevation 12 m above sea level (asl)], Ningbo, Zhejiang province, China; lakeside with abundant water plants, such as lotuses; surface water chemistry at 8.50 am (13 September 2014): water temperature 26.7°C, dissolved oxygen 1.44 mg /l .

Additional localities

Southern littoral zone of Dongqian Lakeside (29.736181º N, 121.652722º E, elevation 17 m asl) with sandy sediment; water chemistry at time of collecting (13 September 2014): water temperature 26.4°C, dissolved oxygen 7.31 mg /l . Streams in Tiantong National Forest Park (29.808636º N, 121.790111º E, elevation 135 m asl) with muddy substrate and unsubmerged vegetation; water chemistry at time of collecting (9 September 2014): water temperature 22°C, dissolved oxygen 7.69 mg /l . Ditches in in Tiantong National Forest Park (29.800322º N, 121.788786º E, elevation 64 m asl) with muddy substrate; water chemistry at time of collecting (9 September 2014): water temperature 19.8°C, dissolved oxygen 4.67 mg /l .

Type material

Holotype: one female (ECNU20160827/TT76) dissected, valves for SEM. Paratype: three females (ECNU20140913/TT30, 31, 33) dissected, another 16 specimens preserved in 70% ethanol.

Etymology

The species is named in honour of the late Professor Nanshan Du (1917–2017), the School of Life Science, East China Normal University, for his great contributions to Chinese carcinology.

Dimensions

(Female, n = 4) Length, 0.56–0.57 mm; height, 0.26–0.28 mm; width, 0.20 mm.

Diagnosis

Carapace small and smooth. First segment of A1 with two setae anteriorly. Two setae on the end of first endopodal segment of A2 different lengths. Two g setae present on L6, the longer one exceeding end of terminal segment by one-half of its total length. Seta Sp on the UR long, exceeding end of ramus; UR attachment with lateral branches on main branch.

Description

Carapace small and smooth. Maximum height at middle. In lateral view, dorsal margin arched. Anterior end wider than posterior. Ventral margin slightly convex. In dorsal view, LV overlapping RV on all free margins. Calcified inner lamella narrow at both ends, posterior margin with narrow fused zone.

A1 seven-segmented. First segment with two setae on dorsal margin and two long setae ventrally. Second and third segments with one seta each. Fourth segment with one dorsal and one ventral seta. Fifth segment with two dorsal setae and one ventral seta. Sixth segment with three setae. Terminal segment with one short aesthetasc ya, one long and two short setae.

A2 four-segmented. Three setae present on basal segment. Exopod consisting of a small plate and three setae (one long and two short); long one reaching to end of first endopodal segment. First endopodal segment with two-segmented aesthetasc Y, almost reaching to end of this segment; two setae present on the end of this segment. Setae z all short. Claw G2 short, not reaching middle of claw G1. Claw GM reaching tips of claws G1 and G3. Claw Gm exceeding the middle of claw GM.

Md first segment of the palp with seta s1 long and hirsute; seta s2 short, stout and hirsute. Second segment with 3 + 2 setae ventrally. Setae α, β and γ all slender. Seta γ long. Coxa narrow.

Mx1 palp two-segmented. Terminal segment of the palp short and broad, with one terminal claw fused to segment.

L5 with one a seta, one long b and one long d seta.

L6 five-segmented. Basal segment with long d1 seta. Second segment with seta e reaching to middle of next segment. Third segment with seta f reaching to end of next segment. Penultimate segment with two g setae, long one exceeding end of terminal segment by one-half of its total length. Terminal segment with one distal claw and two h setae. Seta h1 longer than seta h3.

L7 four-segmented. Basal segment with d1 and dp setae. Penultimate segment with long g seta. Terminal segment with long setae h2 and h3 and short seta h1.

UR robust. Seta Sp and claw Gp of equal length. Claw Gp equalling four-fifths the length of claw Ga. Seta Sa short, equalling one-seventh the length of claw Ga.

UR attachment two lateral branches (one big and one small) present on main branch, distal end with inflated structure.

Remarks

In the tribe Candonini , the genus Schellencandona can be distinguished from other genera by the following characters: carapace smooth or with shallow pits, second segment of the Md palp with 3 + 2 setae, seta d1 on L6 present, setae d1 and dp present and seta f missing on L7, claw Gp on the UR not reduced, Zenker organ with 4 + 2 whorls of spines, etc. ( Meisch 2000; Karanovic 2012). There are seven species recorded in this genus: Schellencandona belgica (Klie) , Schellencandona insueta (Klie) , Schellencandona schellenbergi (Klie) , Schellencandona simililampadis ( Danielopol, 1978) , Schellencandona tea Karanovic and Lee, 2012 , Schellencandona triquetra and Schellencandona yakushimaensis Smith and Kamiya, 2006 . Among them, S. yakushimaensis and S. tea are the only two species reported from Asia (Smith and Kamiya 2006; Karanovic and Lee 2012), and the other five species are from Europe; moreover, six species, except S. yakushimaensis , were found from hypogean environments. In this study, S. dui sp. nov. was found in different water bodies (including ditches, streams, ponds and a lake, see Table 1) in the Tiantong National Forest Park, which expands our knowledge of the distribution and habitat of the genus.

Similar to the other two Asian species ( S. yakushimaensis and S. tea ), no males of the new species were found, and its identification as a Schellencandona species relies mainly on the following characters: small size of the carapace, three setae in the seta group of the Md palp, chaetotaxy of L7, etc. Comparing the new species with other Schellencandona species ( Figure 9 ), we found that: seta Sp on the UR is shorter in S. schellenbergi and S. triquetra ( Meisch 2000) ; the UR attachment of S. insueta is simple ( Meisch 2000); S. tea and S. simililampadis lack a dorsal-distal seta on the basal segment of A1 ( Danielopol 1978; Karanovic and Lee 2012). The new species shares some morphological features with S. yakushimaensis and S. belgica , such as the shape of carapace, basal segment of A1 with one dorsal-distal seta, the length of seta Sp on UR and UR attachment with many branches ( Meisch 2000; Smith and Kamiya 2006). However, the new species can be distinguished from S. yakushimaensis and S. belgica by the length and number of seta g on the L6. There is only one seta g on the L6 of S. yakushimaensis and S. belgica , and in both cases, it is noticeably shorter than the longest g seta in S. dui sp. nov. ( Meisch 2000; Smith and Kamiya 2006) ( Figure 8e ). Additionally, in S. dui sp. nov., two setae on the end of the first endopodal segment of A2 are different lengths, and the short one reaches to end of next segment ( Figure 8b ); whereas in S. yakushimaensis , the short one only reaches to middle of next segment (Smith and Kamiya 2006). The structure of UR attachment of S. dui sp. nov. ( Figure 8h ) is more complicated than that of S. yakushimaensis (Smith and Kamiya 2006) .

The new species has been previously identified as S. cf. belgica (Klie) from China ( Kong et al. 2013; Yu 2014) based on the shape and size of carapace, the length of two setae on the end of first endopodal segment of A2, the complicated branches of UR attachment, etc. In fact, two g setae present on L 6 in S. dui sp. nov. ( Figure 8e ) and only one in S. belgica , and the long one in S. dui sp. nov. is much longer than the one in S. belgica ( Meisch, 2000) , and the length of setae e and f on L6 are longer in S. dui sp. nov. ( Figure 8e ) than in S. belgica . Moreover, S. dui sp. nov. were found from diverse water bodies and S. belgica from wells and interstitial habitats ( Meisch 2000).

Figures

Figure 7. (a–d) Schellencandona dui sp. nov. Female. (a) ECNU20160827/TT7601, dorsal view; (b) ECNU20160827/TT76, internal view of RV; (c) ECNU20160827/TT76, internal view of LV; (d) ECNU20160827/TT7602, external view of LV. (e) Physocypria kraepelini (G. W. Müller 1903). Female. (e) ECNU20140907/TT12, external view of RV. Scale bars: 100 μm.

Figure 8. Schellencandona dui sp. nov. (a, f and g) (ECNU20140913/TT31); (b–e and h) (ECNU20160827/TT76). Female. (a) A1; (b) A2; (c) Md; (d) Mx1 palp; (e) L6; (f) L7; (g) UR; (h) UR attachment. Scale bars: 100 μm.

Figure 9. Graphical key for species of the genus Schellencandona.