Teeth of odontocetes accumulate annual dentinal growth layer groups (GLGs) that record isotope ratios, which reflect the time of their synthesis. Collectively, they provide lifetime records of individual feeding patterns from which life history traits can be inferred. We subsampled the prenatal dentin and postnatal GLGs in Risso's dolphins (Grampus griseus) (n = 65) that stranded or were collected as bycatch in Taiwan (1994–2014) and analyzed them for δ15N and δ13C. Age‐specific δ15N and δ13C values were corrected for effects of calendar year, stranding site, C/N, and sex. δ15N values were higher in prenatal layers (14.94‰ ± 0.74‰) than in adult female GLGs (12.58‰ ± 0.20‰), suggesting fetal enrichment during gestation. Decreasing δ15N values in early GLGs suggested changes in dietary protein sources during transition to complete weaning. Weaning age was earlier in males (1.09 yr) than in females (1.81 yr). Significant differences in δ15N values between weaned males and females suggest potential sexual segregation in feeding habits. δ13C values increased from the prenatal to the 4th GLG by ~1.0‰, indicative of a diet shift from 13C‐depleted milk to prey items. Our results provide novel insights into the sex‐specific ontogenetic changes in feeding patterns and some life history traits of Risso's dolphins.

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With limited inconclusive data provided by gut content analysis, stable isotope analysis has recently emerged to validate trophic position and dietary intake. In this study, a dual isotope approach was used to reveal parrotfish feeding. Comparisons of δ13C and δ15N values of muscle and liver among yellow barred (Scarus dimidiatus), rosy cheek (S. psittacus), and blue-barred (S. ghobban) parrotfishes from Canigao Island, Matalom, Leyte were made to track dietary shifting and to compare dietary carbon intake. Trophic assignment was based on the assumption that consumers are enriched by a factor of 3-4‰ for δ15N, relative to their diet. The δ13C values of muscle tissues of the three species of parrotfish were significantly higher (p=0.001) than those of their liver suggesting dietary shifting. The δ13C values of both muscle and liver tissues of S. dimidiatus were significantly (p<0.001) higher than those of S. psittacus and S. ghobban, but δ13C values of muscle and liver of S. psittacus and S. ghobban did not vary significantly. These mean that S. dimidiatus have different long term and recent dietary carbon intake compared to the other two species, while S. psittacus and S. ghobban have relatively the same dietary carbon intake. Considering the 1‰ δ13C trophic enrichment of consumers relative to their diet, possible dietary carbon sources of the sampled parrotfish include Dendronephthya spp., Ulva reticulata, Sargassum oligocystum, Dictyota sp., Digenea sp., Chlorodesmis sp., and Sargassum muticum suggesting that parrotfishes are generalist consumers. Mean stable isotope nitrogen ratios of S. dimidiatus (5.9‰), S. psittacus (6.9‰) and S. ghobban (6.7‰) together with their carbon isotope ratios confirmed that all sampled parrotfish species are generalist primary consumers.

Uropterygius concolor Rüppell, the type species of the genus Uropterygius, is a small, uniformly brown moray considered to be widely distributed in the Indo‐Pacific region. However, a recent study indicated that the real U. concolor is currently known only from the type locality in the Red Sea, and species recorded outside the Red Sea may represent a species complex that comprises several species. In this study, we assess the genetic and morphological variations of this species complex based on available data. Analyses of cytochrome c oxidase subunit I sequences revealed at least six distinct genetic lineages recognized under ‘U. concolor’. After carefully comparing the morphologies, one of the lineages is described herein as a new species, Uropterygius mactanensis sp. nov., based on 21 specimens collected from Mactan Island, Cebu, Philippines. Another distinct lineage is considered to be a possibly undescribed species based on diagnostic morphological characters. Although the taxonomic status of junior synonyms of U. concolor and some lineages still remain unresolved, this study provides informative morphological characters (i.e., tail length, trunk length, vertebrae number, and arrangement of teeth) that can be used in future studies on this species complex.