Overview

Immunological studies in elasmobranchs have been conducted using a number of model organisms, including the Atlantic sharp-nosed ray, the cow nose ray, the catshark, the dogfish, and the nurse shark. Many of these animals have been used primarily as laboratory models for the study of the evolution of the human immune system. Elasmobranchs are one of the earliest groups of vertebrates to exhibit a fully functional innate and adaptive immune system comparable to that found in mammals. Both innate and adaptive components of the shark immune system have now been described in the literature in detail and many of the pathways for immune reactivity are well known. However, much of this information has been derived from only a few species used as models, which are primarily smaller, benthic species because of the ease with which they are kept in captivity and/or handled in lab settings. Very little is known about oceanic, pelagic shark species in terms of their immune system and immune reactivity. In particular, we know very little about the susceptibility of wild sharks to disease following injuries associated with being caught as by-catch or associated with other environmental stresses and/or behavioral patterns. It is not known whether the immunological reactivity seen in model organisms is uniform across different species not yet examined. Some evidence suggests that there is a high degree of variation in the immune systems of different shark species which would be expected given the length of evolutionary time between divergences among various shark lineages.

One of the challenges for studying the immune system of pelagic sharks is the ability to collect tissue samples and conduct field immune assessment. Current monitoring programs that include tagging studies present an opportunity to investigate the immune status and gain further understanding of the immune system of wild sharks. An important consideration is whether we can use immune status to evaluate the well-being of wild sharks under various stresses, in diverse habitats, at different levels of maturity, etc. Several examples of this have popped up in the literature where investigators have sought to measure well-being in sharks in polluted and non-polluted habitats by measuring an immunological parameter such as inflammation. However, before such studies can really take shape and provide critical information for the conservation of each species, baseline data for various immunological parameters must be established. Once baseline information about the immune reactivity for each species is established, a methodology can be developed to apply these immune assessments to current monitoring protocols and maximize information regarding wild shark immune status. This would allow investigators to assess the health/immune status of wild sharks for the first time and relate their immune condition to their age, maturity, habitat use, migration pattern, and reproductive activity for various species of interest. In order for the immune status of wild sharks to be used in marine conservation, baseline data across species must be collected as an initial step. The purpose of the present study is to conduct a preliminary immune assessment on wild sharks caught off the coasts of South Florida as part of an on-going ecological study and use these data as a baseline to determine whether immune status can be applied to global conservation efforts. It is expected that the results of this exploratory project will yield information about the relevant immunological parameters that can be accurately collected and measured in different pelagic shark species with the intent to include immune status as a critical component to be assessed in monitored populations around the world.