Gymnura cf. poecilura (Shaw, 1804)

Fernando, Daniel, Bown, Rosalind M. K., Tanna, Akshay, Gobiraj, Ramajeyam, Ralicki, Hannah, Jockusch, Elizabeth L., Ebert, David A., Jensen, Kirsten & Caira, Janine N., 2019, New insights into the identities of the elasmobranch fauna of Sri Lanka, Zootaxa 4585 (2), pp. 201-238 : 217

Gymnura cf. poecilura 2

( Figs. 3A , 11 A–D)

In total, five specimens of Gymnura van Hasselt were examined. These came from fish markets in Palkanththura (SL-4) and Puttalam (SL-16) in the North Western Province, from Jaffna (SL-50, SL-51) in the Northern Province, and from the Mutur landing site (SL-75) in the Eastern Province. The latter specimen was deposited in the BRT Ichthyology Collection (BRT-I 0017). All five specimens lacked a dorsal fin. However, some morphological variation was seen across the five specimens. A tiny spine was present on the tails of three (SL-16, SL-50, and SL- 75) specimens. The tails of all five specimens were cross-banded, but the number of bands varied from 9–11. In some specimens—mainly small specimens of less than 32 cm DW—a single black dot was present between the bands ( Fig. 11D ); in other specimens—mainly larger specimens greater than 63 cm DW—a dark spot surrounded by four smaller dark spots was present between each band and the dark band had a central white spot ( Fig. 11B ). However, the five specimens from Sri Lanka differed from one another in NADH2 sequence by only 0–7 bp. In the tree resulting from the Neighbor-Joining analysis, which included sequence data for seven of the 12 described as well as the three undescribed members of the genus recognized by Naylor et al. (2012a) (i.e., Gymnura sp. 1, Gymnura cf. poecilura 1, and Gymnura cf. poecilura 2), all five specimens from Sri Lanka grouped in a tight cluster with our reference specimen of G. cf. poecilura 2 (MM-22; JQ518834 ) from the Gulf of Oman. The Sri Lankan specimens differed from this specimen by 3–5 bp, suggesting they are likely conspecific.

To expand taxon representation to include Gymnura from India, data for a specimen of Gymnura poecilura (Shaw) ( KU821581 ) from its type locality in Visakhapatnam on the eastern coast of India (see Eschmeyer et al. 2018), and a specimen identified as G. cf. poecilura ( KU821578 ) from Mumbai on the western coast of India, were obtained from GenBank. These sequences, which are only 677 and 644 bp in length, respectively, were generated by Muktha et al. (2018) to help inform a redescription of G. poecilura in which a neotype was designated. In total, Muktha et al. (2018) presented NADH2 data for five specimens of G. poecilura from Visakhapatnam, which differed from one another by 0–7 bp, but unfortunately they failed to indicate which, if any, of these specimens was the neotype. In the tree resulting from our Neighbor-Joining analysis, the specimen of G. poecilura from India grouped well away from the specimens from Sri Lanka, supporting the identity of the Sri Lankan specimens as a taxon other than G. poecilura . Moreover, the specimen identified as G. cf. poecilura from India by Muktha et al. (2018) clustered with the specimens from Sri Lanka, suggesting that G. cf. poecilura 2 occurs in both countries. The Sri Lankan specimens differed by 3–4 bp across the 644 bp available for this specimen.

This species is typically referred to in Sri Lanka as G. poecilura (e.g., De Silva 1978, 2006; De Bruin et al. 1995; Morón et al. 1998). However, it is more accurately referred to as G. cf. poecilura 2 in recognition of the fact that the Sri Lankan form appears to represent this undescribed species. As noted above, G. poecilura appears to represent a complex of genetically diverse, yet morphologically similar butterfly rays ( Naylor et al. 2012a). Examination of additional specimens from throughout its current nominal distribution ( Last et al., 2016) is required to fully resolve the taxonomy of this group.

Figures

FIGURE 3. Neighbor-Joining trees of p-distances based on 1,044 bp of aligned NADH2 sequence data for individual batoid genera or groups of genera. Taxon names are followed by country, host specimen number (in parentheses), and GenBank number. Outgroup taxa used in each analysis were omitted from the individual trees. Scale bar values indicate substitutions per site. Specimens deposited in the Blue Resources Trust Ichthyology Collection are indicted by stars (see text for details). A. Gymnura (Gymnuridae). B. Rhinoptera (Rhinopteridae). C. Acroteriobatus and Rhinobatos (Rhinobatidae). D. Torpediniformes.

FIGURE 11. Gymnura cf. poecilura 2 (Gymnuridae) (A–D) and Rhinoptera javanica (Rhinopteridae) (E–H). A. Dorsal surface of female (SL-16). B. Tail of female (SL-16). C. Dorsal surface of immature male (SL-75; BRT-I 0017). D. Tail of immature male (SL-75; BRT-I 0017). E. Dorsal surface of immature male (SL-20). F. Dorsal fin and base of tail (lateral view; SL-20). G. Tooth plates (7) of upper jaw (SL-20). H. Tooth plates (7) of lower jaw (SL-20).