Rhizoprionodon acutus (Rüppell)

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 : 223

Rhizoprionodon acutus (Rüppell)

( Figs. 4B , 14 I–J)

The existence of undescribed diversity in the Rhizoprionodon acutus species complex complicates identification of the single specimen (SL-21) of this complex we encountered in the Erinchamman Kovilady market in Point Pedro in the Northern Province. Based on the molecular and morphological data presented by Caira & Jensen (2015), the specimen from Sri Lanka is most similar to R. acutus from the Gulf of Oman, rather than to any of the numbered designations (i.e., Rhizoprionodon cf. acutus 1, Rhizoprionodon cf. acutus 2, and Rhizoprionodon cf. acutus 3) for the three undescribed members of this species complex recognized by Naylor et al. (2012a). In the tree resulting from our Neighbor-Joining analysis, which included all seven described members of the genus and all three undescribed member of the R. acutus complex, the specimen from Sri Lanka grouped most closely with the reference specimen of R. acutus (MM-4; JQ518653 ) from the Gulf of Oman, differing from this specimen by only 1 bp. In contrast, it differed from our reference specimen of R. cf. acutus 1 from Senegal (SE-219; JQ518652 ) by 10 bp, from our reference specimen of R. cf. acutus 2 from Australia (AU-120; JQ518649 ) by 13 bp, and from our reference specimen of R. cf. acutus 3 from Malaysian Borneo (HBO-30; JQ519100 ) by 18 bp.

This name is in current use for this species in Sri Lanka (e.g., De Silva 1984 –1985, 2006, 2015; De Bruin et al. 1995; Joseph 1999).

Figures

FIGURE 4. Neighbor-Joining trees of p-distances based on 1,044 bp of aligned NADH2 sequence data for individual selachian 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. Carcharhinus and close relatives (Carcharhinidae). B. Rhizoprionodon (Carcharhinidae). C. Galeocerdidae. D. Hemigaleidae. E. Pseudotriakidae. F. Sphyrnidae. G. Iago (Triakidae).

FIGURE 14. Carcharhinus amblyrhyncoides (A–D) and C. cf. limbatus (E–H) (Carcharhinidae), and Rhizoprionodon acutus (I–J) and Rhizoprionodon oligolinx (K–L). A. Lateral view of female (SL-18). B. Ventral view of head of female (SL-18). C. Teeth of upper jaw of female (SL-18). D. Teeth of lower jaw of female (SL-18). E. Lateral view of immature female (SL- 52). F. Ventral view of head of immature female (SL-52). G. Teeth of upper jaw of immature female (SL-52). H. Teeth of lower jaw of immature female (SL-52). I. Lateral view of mature female (SL-21). J. Ventral view of head of mature female (SL-21). K. Lateral view of maturing male (SL-22). L. Ventral view of head of mature male (SL-53).