Chrissia Hartmann, 1957

Chrissia Hartmann, 1957 View in CoL

Chrissia ueluenakarati sp. nov. resembles C. aldabrae (G.W. Müller, 1898) , C. fascigera ( Sars, 1924) , C. junodi ( Delachaux, 1919) and C. sinuata (G.W. Müller, 1898) . It differs from the last two species by the more elongated Cp and the aspects of the CR, especially the ramus length and the spines on the right ramus (see Delachaux 1919; G.W. Müller 1898). Chrissia ueluenakarati sp. nov. differs from C. aldabrae by the Cp shape in lateral view, which is more strongly arched and has the greatest height situated at mid-length (less arched and the greatest height is situated at 1/3 of the length in C. aldabrae ). Additionally, the ramus of the new species is considerably shorter and marginal spines on the right ramus are divided into five small subgroups having gaps between them, whereas in C. aldabrae the ramus is very long and the marginal spines are arranged into two large subgroups without intervals (see G.W. Müller 1898). Chrissia ueluenakarati sp. nov. can be distinguished from C. fascigera by the more strongly arched Cp in lateral view, and the larger marginal spines on the right ramus (see Sars 1924). Moreover, the morphologies of the male reproductive organs and limbs (Hp, prehensile palps and ZO) of the new species are different from those of the three species C. aldabrae , C. fascigera and C. sinuata . Compared to species recorded in Southeast Asia, C. ueluenakarati sp. nov. is most similar to C. ceylonica ( Daday, 1898) than other Chrissia View in CoL . One obvious differences is the morphology of the CR in which the ventral spines are set into several subgroups in the new species (without subgroups in C. ceylonica – see Daday 1898).

Thus far, seven Chrissia View in CoL species have been reported from Southeast Asia (including the new species), five of them encountered in Thailand ( Savatenalinton & Suttajit 2016; Savatenalinton 2023b). Chrissia ueluenakarati sp. nov. is the second species of the genus described from this country, and the third one from Southeast Asia, after C. spinosa ( Tressler, 1937) and C. muangkanensis View in CoL (see Tressler 1937; Savatenalinton 2023b). In addition, the discovery of female and male specimens of C. ueluenakarati sp. nov. in this study is the first record of a sexual population of the genus in Southeast Asia and the fourth one in the OL, after the two Indian species C. achandii ( George & Martens, 1993) and C. goddeerisi ( George & Martens, 1993) (see George et al. 1993) and the Chinese C. acuminata (see Zhai et al. 2023). Species with sexual populations of Chrissia View in CoL are presented in Table 1, most of which were reported from the AT, particularly South Africa.

There are three types of reproductive modes in non-marine ostracods: parthenogenesis, sexual reproduction and geographical parthenogenesis ( Horne et al. 1998). The first type occupies a large fraction of ostracods, including most species of Chrissia , which reproduce by parthenogenetic mode, based on indirect evidence (no males have been encountered to date). The second type is indicated by the occurrence of both sexes in all populations of the species, whereas species with partial existence of sexual populations are defined to the third group. All nine Chrissia species with sexual populations belong to the second type (G.W. Müller 1898, 1908, 1914; Sars 1924; Rome 1965; George et al. 1993). In the Thai ostracod fauna, the third mode of reproduction has been found only in two species of the subfamily Cypricercinae , namely Tanycypris siamensis Savatenalinton & Martens, 2009 (see Savatenalinton & Martens 2009; Savatenalinton 2014) and Strandesia martensi (see Savatenalinton 2024a) in which sexually reproducing populations inhabited the middle part of the Chi River Basin and the distal part of the Lower Songkhram River Basin, respectively. This suggests that the appearance of sexual populations in the third type could relate to the habitat environments as both parts are commonly flooded in the rainy season.

Taxonomic characters of Chrissia were comprehensively provided by Savatenalinton (2023b), all of them non-sexual related characters, whereas diagnostic features, including characters of male reproductive organs, were summarized in the diagnoses of Herpetocypridinae tribes and genera, including Chrissia , by Martens (2001). Based on this summary, the male reproductive organs of C. ueluenakarati sp. nov. are congruent to the diagnosis of Chrissia , for example the medial shield of the Hp without a hook-like process and the two additional internal loops of the spermiduct. The detailed comparisons revealed that there are two groups of Chrissia Hp. The first group possesses the dorsal subtriangular protrusion on the ls, which has been seen in six species, including the new species: C. acuminata , C. bispinosa (G.W. Müller, 1914) , C. fascigera , C. hodgsoni ( Sars, 1924) , C. smaragdina ( Sars, 1924) and C. ueluenakarati sp. nov. (see G.W. Müller 1914; Sars 1924). On the other hand, the second group indicated by the absence of such a protrusion is composed of four species, namely C. ametra (G.W. Müller, 1908) , C. sinuata , C. achandii and C. goddeerisi (see G.W. Müller 1898, 1908; Sars 1924; George et al. 1993). It should be noted that both aspects of the Hp exist in both Afrotropic and Oriental lineages.

In Chrissia View in CoL , the spiny whorls of the ZO are numerous. Most African species possess a large number of spiny whorls, with a range of 45–50 (e.g. C. fascigera , C. hodgsoni , C. smaragdina - Sars 1924), while the number ranges from 25 to 40 in the Oriental species. It should be noted that the smallest number in the genus is recognized in C. ueluenakarati sp. nov. (25 spiny whorls) possibly due to its small size. A similar situation occurs in C. sinuata , a species with the same size as C. ueluenakarati sp. nov., in which the ZO also bears a small number of spiny whorls (33 spiny whorls). To the contrary, large Chrissia View in CoL species (e.g. C. fascigera , C. hodgsoni , C. smaragdina – see Sars 1924) show a higher number, with a range of 38–50 ( Table 1).

n.d. = no data