Validation of an Ultrasound-Guided Technique to Establish a Liver-to-Coelom Ratio and a Comparative Analysis of the Ratios Among Acclimated and Recently Wild-Caught Southern Stingrays,Dasyatis Americana

Courtship and Reproduction of the Whitetip Reef Shark Triaenodon obesus (Carcharhiniformes: Carcharhinidae) in an Ex Situ Environment, with a Description of the Late Embryonic Developmental Stage

Elasmobranchs represent a group of species under considerable anthropic pressure because of the scale of industrial and artisanal fisheries and the loss of essential areas for nursery and feeding, which are causing substantial population losses around the world. Reproduction in an ex situ environment enables a healthy population to be built and maintained in networks of public aquariums, increasing our knowledge of elasmobranch reproductive biology and offering the opportunity for reintroductions in areas where native populations have been removed. The study reports two successful pregnancies of the whitetip reef shark Triaenodon obesus, considered a vulnerable species by the International Union for the Conservation of Nature. Copulation and gestation data are provided, including ultrasound recordings of the late stage of embryo development. Ultrasonography was performed with the GE Logiq and convex transducer and revealed a fetus with defined fins and organogenesis, with definition of eyes, gills, liver, a heart with individualized chambers, partially defined kidneys, and a well-defined spiral intestine. A cartilaginous skeleton forming a posterior acoustic shadow was detailed, as well as a moving fetus with a biparietal diameter of 6.47 cm and a heart rate of 62 Beats Per Minute on spectral Doppler. This is the first successful reproduction of T. obesus in an aquarium in Brazil.

Evaluation of the use of portable ultrasonography to determine pregnancy status and fecundity in bonnethead shark Sphyrna tiburo

This study examined the usefulness of portable ultrasonography in accurately predicting pregnancy and fecundity in the bonnethead shark Sphyrna tiburo by comparing ultrasound-obtained data with those obtained from animal dissection, the gold standard for elasmobranch reproduction studies. Mature female S. tiburo (n = 66) were collected throughout the period of reproduction and examined via portable ultrasonography using two different ultrasound transducers (8-5 MHz linear array transducer and a 5.0-2.5 MHz curvilinear array transducer) to determine pregnancy status and fecundity. Ultrasound-derived data were compared with validated assessments of pregnancy and litter size obtained using animal dissection to determine the level of agreement between the two approaches. Overall, there was strong agreement (90.9%) between pregnancy determinations obtained using ultrasonography and dissection. However, the effectiveness of portable ultrasonography in accurately determining specific stages of maturity and pregnancy differed slightly between transducer types (linear = 61.3%; curvilinear = 88.9%). Measurements of fecundity also agreed well between ultrasonography and dissection and there were no significant differences between mean fecundity estimates obtained using the two methods. In general, portable ultrasonography was found to be a good alternative to lethal sampling and animal dissection in obtaining reproductive data critical for the management and conservation of elasmobranchs. Special attention should be given to factors that can influence the reliability of ultrasound-derived data such as transducer type, embryo size and sound wave interference due to gut contents.

Fish Oncology: Diseases, Diagnostics, and Therapeutics

The scientific literature contains a wealth of information concerning spontaneous fish neoplasms, although ornamental fish oncology is still in its infancy. The occurrence of fish neoplasms has often been associated with oncogenic viruses and environmental insults, making them useful markers for environmental contaminants. The use of fish, including zebrafish, as models of human carcinogenesis has been developed and knowledge gained from these models may also be applied to ornamental fish, although more studies are required. This review summarizes information available about fish oncology pertaining to veterinary clinicians.