No abstract

Stable nitrogen (delta(15)N) and carbon (delta(13)C) isotopes of Atlantic sharpnose shark Rhizoprionodon terraenovae embryos and mothers were analysed. Embryos were generally enriched in (15)N in all studied tissue relative to their mothers' tissue, with mean differences between mother and embryo delta(15)N (i.e. Deltadelta(15)N) being 1.4 per thousand for muscle, 1.7 per thousand for liver and 1.1 per thousand for cartilage. Embryo muscle and liver were enriched in (13)C (both Deltadelta(13)C means = 1.5 per thousand) and embryo cartilage was depleted (Deltadelta(13)C mean = -1.01 per thousand) relative to corresponding maternal tissues. While differences in delta(15)N and delta(13)C between mothers and their embryos were significant, muscle delta(15)N values indicated embryos to be within the range of values expected if they occupied a similar trophic position as their respective mothers. Positive linear relationships existed between embryo total length (L(T)) and Deltadelta(15)N for muscle and liver and embryo L(T) and Deltadelta(13)C for muscle, with those associations possibly resulting from physiological differences between smaller and larger embryos or differences associated with the known embryonic nutrition shift (yolk feeding to placental feeding) that occurs during the gestation of this placentatrophic species. Together these results suggest that at birth, the delta(15)N and delta(13)C values of R. terraenovae are likely higher than somewhat older neonates whose postpartum feeding habits have restructured their isotope profiles to reflect their postembryonic diet.

No abstract

The eyes from six Greenland sharks, Somniosus microcephalus (Bloch & Schneider), infected with the parasitic copepod Ommatokoita elongata (Grant) were collected in the Arctic waters of Victor Bay, North‐west Territories, Canada, for study. Transformed adult female copepods, one per eye, were firmly attached to the corneas by an anchoring structure (i.e. the bulla) and each bulla was associated with an opaque area on the cornea. Two eyes additionally had one O. elongata copepodid attached to the cornea via frontal filaments with bullas which were each associated with a small corneal opacity. In addition to opacities associated with copepods at the time of collection, there were several randomly distributed, small, round‐to‐irregular, full‐thickness corneal opacities which were not associated with copepods. Two unfixed eye lenses grossly examined in the field were normal in appearance. Histologically, corneal epithelial ulceration and heterophilic keratitis, disruption, mineralization, and detachment of Bowman's membrane, thinning, disorganization, mineralization and fibrosis of the corneal substantia propria, and focal thinning and mineralization of Descement's membrane were observed. Mild heterophilic and mononuclear anterior uveitis was also present. Based on the present observations, it is concluded that parasitism by O. elongata could lead to severe vision impairment (possibly including blindness) in Greenland sharks. However, the otherwise healthy appearance of the infected sharks studied and the information contained in the literature suggests that O. elongata infections do not significantly debilitate the hosts.