Candidia (Nakabo, 2013)

Huang, Shih-Pin, Wang, Feng-Yu & Wang, Tzi-Yuan, 2017, Zavreliella shidai Han & Liu & Luo & Tang 2021, sp. n., Zoological Studies 56 (40), pp. 1-13 : 9-10

Candidia and Nipponocypris are distinct genera

All valid species of Candidia and Nipponocypris were used in this study to reassess their relatedness. The BI and ML trees both showed that Candidia and Nipponocypris were well separated with high support (1.00 in BI, and 65 in ML); our results were consistent with several previous studies ( Huynh and Chen 2013; Liao et al. 2011c; Tang et al. 2013). Morphologically, these two genera can be easily distinguished: Candidia has maxillary barbels, which are absent in Nipponocypris ( Chen and Fang 1999; Nakabo 2013). The present study thus strongly suggests that they should be regarded as distinct genera.

Evolutionary implications of the color pattern

Among all studied species, only those in the Opsariichthys group have distinct longitudinal or vertical stripes. Most of them are known to have color dimorphism, especially Opsariichthys and Zacco ( Chen and Chang 2005) . This study’s tree topologies revealed that the type of stripe pattern on the sides of the body was highly correlated with molecular phylogeny ( Fig. 5 ). The BI tree showed that Parazacco , Candidia , and Nipponocypris share similar longitudinal stripe patterns. Opsariichthys and Zacco both share similar vertical stripe patterns, although independent bars always appeared in Opsariichthys and the otherwise typically smaller bars are usually fused into a single wide bar in Zacco , but both could be defined as the same type of color pattern. Otherwise, members of Xenocyprididae have only an indistinct longitudinal stripe.

These representative stripes or bars can also be found in several groups under Cypriniformes , such as Danio , Crossocheilus and Acrosscheilus. The genus Danio , a primitive cyprinids, already shows these stripe and bar patterns of the Opsariichthys group ( McCluskey and Postlethwait 2015). Among these, D. erythromicron and D. choprae have distinct vertical stripes and D. nigrofasciatus and D. rerio have distinct longitudinal ones. Furthermore, Danio is the earliest offshoot in tree topologies ( Tang et al. 2013; Stout et al. 2016). Therefore, we hypothesize that the types of vertical and longitudinal stripes presented in the Opsariichthys group might have originated from an primitive ancestor, then distinct vertical stripes might have been lost among these cyprinids but retained in the Opsariichthys group.

Figures

Fig. 5. Correlation between stripe patterns and molecular relationships in the Opsariichthys group (tree reconstructed based on Bayesian inference in this study). © 2017 Academia Sinica, Taiwan