Assessing common bottlenose dolphin (Tursiops truncatus) population structure in Mississippi Sound and coastal waters of the north central Gulf of Mexico

1. Population structure of highly mobile marine organisms can be complex and difficult to study, but it is important to understand how populations partition themselves within their environment for accurate assessment of both natural and anthropogenic impacts and successful management. The 2010 Deepwater Horizon oil spill negatively impacted common bottlenose dolphins (Tursiops truncatus) within Mississippi Sound and the surrounding north central Gulf of Mexico (GOMx); however, little was known about their underlying population structure in these waters. Thus, it was unclear how many demographically independent populations were affected by the spill.
2. Common bottlenose dolphin samples were collected throughout inshore waters of Mississippi Sound and coastal waters of the north-central GOMx. Mitochondrial DNA control region sequence data and 19 nuclear microsatellite loci were analysed to determine how many populations are present and characterize their range throughout these waters.
3. Bayesian clustering and migration analyses identified two genetically distinct and demographically independent populations: one predominantly inhabiting Mississippi Sound and adjacent coastal waters, and a second population extending generally from offshore of Mobile Bay, Alabama, east along the Florida Panhandle. Neither of these populations align with the currently delineated management stocks previously used to estimate impacts from the oil spill on common bottlenose dolphins in this portion of the GOMx.
4. These results suggest that revisions may be necessary so that management stocks accurately represent the demographically independent populations present in these waters. Furthermore, better comprehension of underlying population structure will enhance impact assessments on common bottlenose dolphins and provide more appropriate baseline data to support future restoration and conservation objectives.

     

Stocking Density Effects on Production Characteristics and Body Composition of Market Size Cobia,Rachycentron canadum,Reared in Recirculating Aquaculture Systems

Culture density in excess of a critical threshold can result in a negative relationship between stocking density and fish production. This study was conducted to evaluate production characteristics of juvenile cobia, Rachycentron canadum, reared to market size in production‐scale recirculating aquaculture systems (RAS) at three different densities. Cobia (322 ± 69 g initial weight) were reared for 119 d at densities to attain a final in‐tank biomass of 10, 20, or 30 kg/m³. The specific objective was to determine the effects of in‐tank crowding resulting from higher biomass per unit rearing volume independent of system loading rates. Survival was ≥96% among all treatments. Mean final weight ranged from 2.13 to 2.15 kg with feed conversion efficiencies of 65–66%. No significant differences were detected in growth rate, survival, feed efficiency, or body composition. This study demonstrates that cobia can be reared to >2 kg final weight at densities ≤30 kg/m³ under suitable environmental conditions without detrimental effects on production.     

Multiple cutaneous leiomyomas in the perineum of a horse.

Multiple cutaneous masses developed in the perineum of a 14-year-old Saddlebred stallion over a period of approximately 5 years. Clinically, the masses ranged in size from 3- to 9-mm diameter and were not ulcerated, painful, or pruritic. Three of the masses were surgically excised and submitted for microscopic evaluation. The masses were dome shaped to nodular, located in the superficial dermis, and composed of haphazardly arranged bundles of plump spindle-shaped cells. The tumor cells immunoreacted with monoclonal antibodies directed against desmin, muscle-specific actin, and smooth muscle actin, confirming a smooth muscle origin. Multiple cutaneous leiomyomas have not been reported previously in horses.     

Paranasal meningioma in a horse.

Paranasal meningioma was diagnosed in a 5-year-old Appaloosa gelding. The mass occupied the right maxillary, frontal, and sphenopalatine sinuses but did not invade the calvarium. The diagnosis was based on histologic evaluation, positive immunohistochemical staining for vimentin and cytokeratin, and ultrastructural features including the presence of interdigitating spindle cells with numerous desmosomes.     

Primary epitheliotropic intestinal T-cell lymphoma in a horse.

A 17-year-old Quarterhorse gelding with a clinical diagnosis of protein-losing enteropathy was submitted for necropsy following a 4-5-month duration of weight loss, decreased appetite, and hypoproteinemia. Gross findings included multiple 1-2-cm diameter ulcers on the luminal surfaces of the duodenum and ileum. Histologic examination revealed individual large, round cells infiltrating much of the mucosal epithelium of the duodenum, jejunum, ileum, and colon in addition to multifocal areas of ulceration. Similar round cells infiltrated Brunner's glands and expanded the submucosa beneath the foci of ulceration. Immunohistochemical staining indicated the round cell population was of T-lymphocyte origin. Several features of this equine neoplasm bear similarities to enteropathy-associated T-cell lymphoma in humans.