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Patterson J.C.,University of Massachusetts Dartmouth | Sepulveda C.A.,Pfleger Institute of Environmental Research | Bernal D.,University of Massachusetts Dartmouth
Journal of Morphology | Year: 2011

The thresher sharks comprise a single family (Alopiidae) of pelagic sharks most easily recognized by the elongate dorsal lobe of their caudal fin. Despite morphological similarities among the alopiids, the common thresher (Alopias vulpinus) is unique in that its red, aerobic myotomal muscle (RM) is medially positioned (i.e., closer to the vertebrae), its systemic blood is supplied through a lateral circulation which give rise to counter-current heat exchanging retia, and it is capable of regional RM endothermy. Despite this information, it remains unknown if the other two alopiid species (bigeye thresher, Alopias superciliosus and pelagic thresher, Alopias pelagicus) also possess some or all of the characteristics related to regional RM endothermy. Thus, this study aimed to 1) document the presence of vascular specializations necessary for heat retention and RM endothermy and 2) measure the in vivo muscle temperatures of all three alopiid species. Laboratory dissections of the thresher species showed that only A. vulpinus possesses the lateral branching of the dorsal aorta giving rise to a lateral subcutaneous circulation and retial system, and that RM temperatures are elevated relative to ambient temperature. By contrast, both A. pelagicus and A. superciliosus have a similar systemic blood circulation pathway, in which the dorsal aorta and postcardinal vein form the basis for the central circulation and in vivo RM temperature measurements closely matched those of the ambient temperature at which the sharks were captured. Collectively, the vascular anatomy and in vivo temperature data suggest that only one species of thresher shark (A. vulpinus) possesses the requisite vascular specializations (i.e., lateral subcutaneous vessels and retia mirabilia) that facilitate RM endothermy. © 2011 Wiley-Liss, Inc.

Marshall H.,University of Massachusetts Dartmouth | Field L.,University of Massachusetts Dartmouth | Afiadata A.,University of Massachusetts Dartmouth | Sepulveda C.,Pfleger Institute of Environmental Research | And 2 more authors.
Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology | Year: 2012

For many shark species, little information exists about the stress response to capture and release in commercial longline fisheries. Recent studies have used hematological profiling to assess the secondary stress response, but little is known about how, and to what degree, these indicators vary interspecifically. Moreover, there is little understanding of the extent to which the level of relative swimming activity (e.g., sluggish vs. active) or the general ecological classification (e.g., coastal vs. pelagic) correlates to the magnitude of the exercise-induced (capture-related) stress response. This study compared plasma electrolytes (Na +, Cl -, Mg 2+, Ca 2+, and K +), metabolites (glucose and lactate), blood hematocrit, and heat shock protein (Hsp70) levels between 11 species of longline-captured sharks (n=164). Statistical comparison of hematological parameters revealed species-specific differences in response to longline capture, as well as differences by ecological classification. Taken together, the blood properties of longline-captured sharks appear to be useful indicators of interspecific variation in the secondary stress response to capture, and may prove useful in the future for predicting survivorship of longline-captured sharks where new technologies (i.e., pop-up satellite tags) can verify post-release mortality. © 2012 Elsevier Inc.

Wegner N.C.,University of California at San Diego | Sepulveda C.A.,Pfleger Institute of Environmental Research | Bull K.B.,University of California at San Diego | Graham J.B.,University of California at San Diego
Journal of Morphology | Year: 2010

This comparative study of the gill morpho-metrics in scombrids (tunas, bonitos, and mackerels) and billfishes (marlins, swordfish) examines features of gill design related to high rates of gas transfer and the high-pressure branchial flow associated with fast, continuous swimming. Tunas have the largest relative gill surface areas of any fish group, and although the gill areas of non-tuna scombrids and billfishes are smaller than those of tunas, they are also disproportionally larger than those of most other teleosts. The morphometric features contributing to the large gill surface areas of these high-energy demand teleosts include: 1) a relative increase in the number and length of gill filaments that have, 2) a high lamellar frequency (i.e., the number of lamellae per length of filament), and 3) lamellae that are long and low in profile (height), which allows a greater number of filaments to be tightly packed into the branchial cavity. Augmentation of gill area through these morphometric changes represents a departure from the general mechanism of area enhancement utilized by most teleosts, which lengthen filaments and increase the size of the lamellae. The gill design of scombrids and billfishes reflects the combined requirements for ram ventilation and elevated energetic demands. The high lamellar frequencies and long lamellae increase branchial resistance to water flow which slows and streamlines the ram ventilatory stream. In general, scombrid and billfish gill surface areas correlate with metabolic requirements and this character may serve to predict the energetic demands of fish species for which direct measurement is not possible. The branching of the gill filaments documented for the swordfish in this study appears to increase its gill surface area above that of other billfishes and may allow it to penetrate oxygen-poor waters at depth. © 2009 Wiley-Liss, Inc.

Agency: NSF | Branch: Continuing grant | Program: | Phase: Physiolg Mechansms&Biomechancs | Award Amount: 287.19K | Year: 2014

Temperature plays an important role in the biology of animals, particularly for those that sustain high levels of locomotor activity, as both muscle performance and blood-oxygen binding properties are directly affected. For most vertebrates, in which body temperature is similar to that of the surrounding environment, a change in ambient temperature will have profound effects on physiology. Marine pelagic fishes live in a thermally-stable environment marked by significant variation in temperature only with depth and latitude. While many fish remain within a narrow temperature range some are known to migrate across wide latitudinal ranges or dive into deeper, colder water. Of those species that routinely dive, few are capable of sustaining long periods of time within the cold, deep ocean. The swordfish is one of relatively few active fish species capable of diving for extended periods of time in the deep, cold, and oxygen depleted waters and then rapidly returning to the warm surface waters. The ability to withstand and routinely transition between disparate environmental regimes makes the swordfish an ideal candidate for studies of the effects of temperature and hypoxia on vertebrate muscle function and oxygen transport.

This study will assess the effects of temperature and hypoxia tolerance on muscle performance, cardiorespiratory function, and gene expression in fishes with different levels of tolerance for these extreme ambient conditions. This study builds upon previous NSF-funded research on muscle function and will increase our understanding of how selective pressures have lead to adaptations for life on the edge. This project will involve numerous students (high school, undergraduate, and graduate level) in hands-on field and laboratory research. The findings from this work will be communicated to the general public (including local fishermen and K-12) via seminars, presentations and internet portals. The results from this work will also be communicated in accessible formats to scientific, management, and public communities with the intent to foster greater awareness of scientific inquiry, discovery and progress.

Sepulveda C.A.,Pfleger Institute of Environmental Research | Aalbers S.A.,Pfleger Institute of Environmental Research | Ortega-Garcia S.,Centro Interdisciplinario Of Ciencias Marinas Ipn Av Ipn S N Col Playa Palo Of Santa Rita | Wegner N.C.,University of California at San Diego | Bernal D.,University of Massachusetts Dartmouth
Marine Biology | Year: 2011

The depth distribution and temperature preferences of wahoo (Acanthocybium solandri) were quantified in the eastern North Pacific using archival tags. One hundred and eight data-loggers were deployed on wahoo (105-165-cm fork length) from 2005 to 2008 at three locations off of the coast of Baja California Sur, Mexico (Alijos Rocks, 25°00′N/115°45′W; Magdalena Bay Ridge, 25°55′N/113°21′W; Hurricane Bank, 16°51′N/117°29′W). Twenty-five tagged individuals (23%) were recaptured within close proximity (< 20 km) of their release sites. Collectively, depth and temperature data from 499 days revealed a predominant distribution within the upper mixed layer, with an average (±SD) depth of 18 ± 4 m during the day and 17 ± 6 m at night. Wahoo spent 99.2% of the daytime and 97.9% of night above the thermocline, and the greatest depth achieved by any fish was 253 m. Mean dive duration (3.8 ± 2.9 vs. 2.3 ± 0.8 min) and the vertical rate of movement (3.8 ± 1.3 vs. 3.0 ± 0.5 m min-1) were greater at night when compared to day. Ambient temperatures obtained from tag records ranged from 11.1 to 27.9°C, with an average of 25.0 ± 1.1°C. These data identify the importance of the warm, upper mixed layer for the wahoo. High recapture rates proximal to the deployment sites suggest seasonal site fidelity and reveal the economic importance of this resource to both commercial and recreational fisheries of the region. © 2011 Springer-Verlag.

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