Atlantic bluefin tuna Thunnus thynnus feeding ecology in the northern Gulf of Mexico: a preliminary description of diet from the western Atlantic spawning grounds.

A combination of stomach contents, nitrogen stable-isotope and tissue C:N values are presented to demonstrate feeding activity of Atlantic bluefin tuna Thunnus thynnus on the Gulf of Mexico (GOMEX) spawning grounds. Diets include teleosts, cephalopods, crustaceans and a pelagic tunicate (Pyrosoma atlanticum). Results reveal the need to classify the GOMEX as a T. thynnus feeding ground.

Single nucleotide polymorphism discovery in albacore and Atlantic bluefin tuna provides insights into worldwide population structure.

The optimal management of the commercially important, but mostly over-exploited, pelagic tunas, albacore (Thunnus alalunga Bonn., 1788) and Atlantic bluefin tuna (BFT; Thunnus thynnus L., 1758), requires a better understanding of population structure than has been provided by previous molecular methods. Despite numerous studies of both species, their population structures remain controversial. This study reports the development of single nucleotide polymorphisms (SNPs) in albacore and BFT and the application of these SNPs to survey genetic variability across the geographic ranges of these tunas. A total of 616 SNPs were discovered in 35 albacore tuna by comparing sequences of 54 nuclear DNA fragments. A panel of 53 SNPs yielded FST values ranging from 0.0 to 0.050 between samples after genotyping 460 albacore collected throughout the distribution of this species. No significant heterogeneity was detected within oceans, but between-ocean comparisons (Atlantic, Pacific and Indian oceans along with Mediterranean Sea) were significant. Additionally, a 17-SNP panel was developed in Atlantic BFT by cross-species amplification in 107 fish. This limited number of SNPs discriminated between samples from the two major spawning areas of Atlantic BFT (FST  = 0.116). The SNP markers developed in this study can be used to genotype large numbers of fish without the need for standardizing alleles among laboratories.

Physiologic and clinicopathologic effects of crude oil on loggerhead sea turtles.

The physiologic and clinicopathologic effects of weathered South Louisiana crude oil exposure were studied in the laboratory in juvenile loggerhead sea turtles. Sea turtles ingested oil incidentally, and oil was observed clinging to the nares, eyes, and upper esophagus, and was found in the feces. Oiled turtles had up to a four-fold increase in white blood cell counts, a 50% reduction in red blood cell counts, and red blood cell polychromasia. Most serum blood chemistries (e.g., BUN, protein) were within normal ranges, although glucose returned more slowly to baseline values than in the controls. Gross and histologic changes were present in the skin and mucosal surfaces of oiled turtles, including acute inflammatory cell infiltrates, dysplasia of epidermal epithelium, and a loss of cellular architectural organization of hte skin layers. The cellular changes in the epidermis are of particular concern because they may increase susceptibility to infection. Although many of the observed physiological insults resolved with a 21-day recovery period, the long-term biological effects of oil on sea turtles remain completely unknown.

Serotonin is necessary for short-term modulation of the exercise ventilatory response.

The exercise ventilatory response is augmented during conditions of increased respiratory dead space (delta Vd), a phenomenon that we refer to as short term modulation (STM). To test the hypothesis that serotonin is necessary in the mechanism underlying STM, experiments were conducted on ten awake goats. Ventilation, CO2 production and PaCO2 were measured at rest and during treadmill exercise (4 km/h, 5% grade), with and without delta Vd (0.25 L), before and after systemic administration of the serotonin receptor antagonist, methysergide maleate (n = 6; 1 mg/kg, i.v.), or the tryptophan hydroxylase inhibitor, p-chlorophenylalanine (PCPA; n = 4; 100 mg/kg, i.v.). Pre-methysergide: (1) PaCO2 decreased from rest to exercise to a similar degree with (-1.9 mmHg) and without (-1.8 mmHg) delta Vd; (2) the exercise ventilatory response increased 59% +/- 13% (P < 0.01) with delta Vd, accounting for similar exercise PaCO2 regulation and demonstrating STM; and (3) effects of delta Vd on exercise tidal volume and frequency responses were inconsistent. Post-methysergide: (1) there were no significant effects on ventilation or PaCO2 at rest or during exercise in control (mask) conditions; (2) the exercise ventilatory response was unaffected by delta Vd, thereby allowing PaCO2 to increase 4.1 +/- 3.0 mmHg from rest to exercise (P < 0.05); and (3) with delta Vd during exercise, the tidal volume response was increased, but was offset by a decreased frequency response. Following PCPA (16-24 h): (1) hyperventilation was evident at rest and during exercise; (2) the exercise ventilatory response was augmented, indicating STM; and (3) the exercise ventilatory response with delta Vd was not affected further, allowing PaCO2 to increase from rest to exercise and indicating an inability to elicit further STM. These data suggest that serotonin is necessary for short term modulation of the exercise ventilatory response with increased respiratory dead space, although the location of relevant serotonin receptors is not yet clear.

Respiratory mechanics of the loggerhead sea turtle, Caretta caretta.

Respiratory mechanics were evaluated in excised lungs and in spontaneously breathing loggerhead sea turtles (Caretta caretta). Respiratory compliance curves reflect the pressure volume characteristics of the body wall. Compliance values are comparable to those of reptiles having simpler lung structure. Maximum flow rates in excised lungs (18-25 ml.sec-1.kg-1) were only slightly below the range reported for marine mammals. During spontaneous tidal breathing expiratory flow rates (11.8 ml.sec-1.kg-1) were lower than maximum values. In the sea turtle, respiratory adaptations including reduced airway resistance and muscular contribution to breathing are similar to marine mammals. These mechanical specializations shorten breathing time, which contributes to diving performance.