Sexual, ontogenetic, temporal and spatial effects on the diet of Urotrygon rogersi (Elasmobranchii:Myliobatiformes)

Abstract

The food habits and trophic ecology of Urotrygon rogersi were analysed to ascertain sexual, ontogenetic, temporal and spatial effects on the diet. These effects were examined with contingency tables, simple correspondence analysis and MANOVA. The trophic relationships of the species were determined with Levin's niche amplitude index and Pianka's diet overlap index. Urotrygon rogersi is a predator of benthic organisms, especially shrimp and polychaetes. Analysis of sex and time showed no significant differences, but differences among class sizes were found. A strong trend towards diet specialization and a strong overlap between sexes and between class sizes were found. Finally, fishing activity on shrimps in the study area could force U. rogersi to change its trophic spectrum over time as an adaptation to the considerable reduction in its principal prey.

Age and Growth of the Round Stingray Urotrygon rogersi, a Particularly Fast-Growing and Short-Lived Elasmobranch

“…Changes in feeding habits with size or age can generate changes in behavior; ontogenetic changes in diet were detected in U. rogersi from individuals < 20 cm total length (< 11.5 cm DW, ca. 1 year old) compared to larger ones, with a shift from polychaetes to shrimps [4]. This size or age is closer to that corresponding to the onset of maturity than to the inflection point in the growth curve.…”

“…This species is a specialist that feeds mainly on crustaceans and polychaetes, showing a strong diet overlap between sexes and size classes [4]. This aplacental viviparous species attains a maximum size of 20 cm disc width (DW), its median size at maturity is 11.5–11.8 cm DW in males and 11.8–12.3 cm DW in females, size at birth is 7.5–8.2 cm DW and 11.5–14.7 cm total length, gestation lasts about 5–6 months, and the reproductive cycle is triannual and aseasonal [5].…”

Feeding ecology and dietary comparisons among three sympatric Neotrygon (Myliobatoidei: Dasyatidae) species

“…As with the interspecific comparisons, the intraspecific differences in Neotrygon diets were attributed in part to the improved foraging and predation capabilities of larger rays (Gray et al , 1997; Bizzarro et al , 2007; Jacobsen & Bennett, 2011). This again would provide larger rays with more opportunities to access a wider range of prey, which in itself could reduce competition for food resources with smaller conspecifics (Powter et al , 2010; Sommerville et al , 2010; Navia et al , 2011). This is arguably most notable in N. kuhlii where the % I RI of polychaetes increased by over 70% between the smallest and largest size class [Table II and Fig.…”

A new genus with two new species of lecanicephalidean tapeworms (Cestoda) from the mangrove whipray, Urogymnus granulatus (Myliobatiformes: Dasyatidae),from the Solomon Islands and northern Australia

“…Okada and Taniguchi 1971, Hambright 1991, Mittelback and Persson 1998, Dörner and Wagner 2003, Huss et al 2008, Byström et al 2012. Such ontogenetic shifts in diet are particularly well documented within the Elasmobranchii (Hoffmayer and Parsons 2003, Bethea et al 2006, Hussey et al 2011, Newman et al 2012, Shiffman et al 2014, including batoids (Brickle et al 2003, Farias et al 2006, Dale et al 2011, Navia et al 2011, Espinoza et al 2013, Šantić et al 2013, Spath et al 2013. Body size has been demonstrated to have such a significant impact on prey choice that a predatory individual will likely share a greater proportion of its diet with a similarly-sized individual of a different species than with a conspecific of a different size (Polis 1984, Bax 1998.…”