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Physiology Studies

Although often not a primary study objective, the PIER research team continues to collaborate on several physiological and ecological studies on highly migratory species. The bulk of these studies have been on species that are relatively difficult to access and therefore have received relatively little study to date.

Understanding the physiological basis behind movements and performance helps us understand how different species use and partition the marine environment. 

An unexpected result of the trial and testing of Deep-Set Buoy Gear was the unprecedented access it provided to live and healthy swordfish specimens for tagging and physiological studies.  Although swordfish continue to support vast commercial fisheries around the globe, many aspects of the basic biology remain poorly understood.  One example is related to its capacity to withstand extremely cold temperatures at depth.   PIER researchers are working collaboratively with several laboratories to investigate how swordfish tolerate such intense daily temperature fluctuations.  Ongoing studies range from examining heat balance and vascular specialization to the effects of temperature on muscle performance.

See Past publications for more information

Swordfish Physiology Studies

Heat conservation, vascular specialization and muscle function.

Collaborative researchers:

Diego Bernal, Ph.D. (University of Mass., Dartmouth)
Ashley Stoer, doctoral candidate (UMD)
Jeanine Sepulveda, PhD (MiraCosta College)
Doug Syme, PhD (University of Calgary)

An unexpected result of the trial and testing of Deep-Set Buoy Gear was the unprecedented access it provided to live and healthy swordfish specimens for tagging and physiological studies.  As a large predatory fish that is uniquely deep-dwelling, many aspects of the basic biology of swordfish are of particular interest; yet remain poorly understood due to their elusive nature.   The markedly low temperatures that swordfish experience at depth demand the use of special adaptations in heat regulation and muscle function, especially in regards to its high functioning predatory nature.   PIER researchers are working collaboratively with several laboratories to investigate these aspects of swordfish physiology.  Ongoing studies range from examining heat balance and vascular specialization to the effects of temperature on muscle performance.

Thermal Studies

This work uses a suite of laboratory and field techniques to better understand how the swordfish is capable of expanding its thermal niche to waters well below the thermocline.  The thermal studies use electronic tags to log the internal body temperature of free swimming swordfish.  This specialized tag has a temperature probe that records body temperature at the location of the tag anchor.  Once the tag releases from the swordfish, the PIER team sets out to locate and recover it for analysis in the laboratory.  Muscle heating and cooling rates are examined over the course of the track period to assess the degree to which swordfish elevate internal muscle temperatures above ambient temperature.

Vascular Specialization

The vascular tissue responsible for circulating blood throughout the body is fixed, stained and sectioned for examination under a microscope.  Additional work includes the tracing of the circulation to and from the red muscle to better understand blood flow pathways in swordfish.

Muscle Function

This work brings together a collaborative team of researchers to investigate the effects of temperature on the contractile kinetics, or muscle performance, of swordfish muscle using the work-loop technique.  Muscle preparations from freshly caught swordfish are isolated and transported live to the PIER laboratory.  Once in the lab, the muscle preparations are cut down in size and mounted to a force transducer in a temperature controlled rig (shown to the right).  The live muscle bundle  is then subjected to work loop experiments over a series of temperatures (4-24oC).  This work assesses how swordfish muscle performs over a range of operating temperatures and forms the basis for doctoral student Ashley Stoer’s dissertation in the Bernal Laboratory at the University of Massachusetts, Dartmouth.

Swimming Muscle Physiology of Thresher Sharks

The Functional Significance of Divergent Locomotor Designs in Pelagic Fish (National Science Foundation IOB-0617384)

Collaborative Researchers:
Diego Bernal, Ph.D. (University of Massachusetts)
Jeanine Sepulveda, Ph.D (Mira Costa College)
Douglas Syme, Ph.D. (University of Calgary, Canada)

This project  compared several aspects of locomotor muscle function and design within a single family of large pelagic sharks, the thresher sharks (Alopiidae). Within the thresher family there are three different species (common thresher, bigeye thresher and pelagic thresher) that all possess an extremely elongate upper caudal lobe, which is as long as their entire body.

Superficially, all three thresher species appear to be very similar, however, recent studies have shown that the internal anatomy of the common thresher is surprisingly distinct from the pelagic and bigeye threshers (Sepulveda et al. 2005).

In the common thresher, the red muscle (sometimes referred to as the blood-line) is condensed in to a solid, piston-like muscle mass that is predominantly distributed over the anterior body in a medial position (i.e. near the vertebral column). Anatomically, this layout is strikingly similar to that of tunas and lamnid sharks, two groups known for specialized swimming muscle physiology. Common threshers also differ from the other two species in having a blood supply to the RM through a set of lateral vessels that give rise to a countercurrent heat exchange system. This heat exchange system allows for RM temperature elevation, just as it does in tunas and lamnid sharks (Bernal et al., 2005).

Whole-body reconstructions of the three thresher shark species, showing the very different positions of the red, aerobic locomotor muscle (RM).

 

 

 

 

 

 

 

 

 

The threshers are the only group known to posses both regionally endothermic and ectothermic taxa, and represent the ideal system for testing hypotheses on the evolution of divergent locomotor mechanisms.

This study examined the swimming biomechanics and twitch kinetics of this group and compared these data to other high performance species (i.e., mako sharks).