Category: General Article
It may be surprising to find a team of marine biologists exploring a dark cave on the coast of Hungary, but looking for life in unusual places is all in a day’s work for Dr. Heather Bracken-Grissom. Although Heather may encounter numerous animal species during her cave excursions, her focus is on crustaceans — or “crusties” as they are affectionately known in her field.
Crustaceans are an extremely large group of arthropods, or animals which have no backbone, segmented bodies and jointed legs. Currently, there are over 67,000 known species of crustaceans in the world but more are being discovered every year.
“Crustaceans play are really vital role in the food chain, bridging the gap between the primary producers and high level consumers such as fish and marine mammals,” Heather told the Oceanscape Network during a phone interview. “As a result, any little event that affects crustaceans is going to have a larger impact on that whole ecosystem.”
Heather’s research is focused on how crustaceans have evolved. Evolution is the scientific theory that organisms change and adapt to their environment over time. The theory of evolution by natural selection was first advanced by Charles Darwin, an English naturalist and geologist, who theorized that some organisms have characteristics which allow them to better survive within a particular ecosystem. Over time, through the process of “natural selection,” organisms with beneficial characteristics would thrive and successfully reproduce while those without beneficial characteristics would struggle and eventually die off.
In her research, Heather examines how crustaceans are able to colonize “extreme environments” such as the deep-sea and remote marine and freshwater caves where other life would surely perish due to the lack of food and other harsh conditions. Another form of extreme environment Heather studies are those created by people, such as areas affected by oil spills, pollution and anthropogenic climate change.
“A lot of my research has been focused on the Gulf of Mexico and the Caribbean,” Heather said. “Most of my fieldwork occurs on research cruises where we go out and study these animals in their natural habitats but we also collect specimens and bring them back into the lab for genetic analysis.”
One of the most interesting extreme environments Heather investigates are anchialine caves. These are inland caves that are generally found close to the coast and have complex subterranean connections to the marine environment. In some cases, the species found in anchialine caves can be completely isolated from the outside world, making these caverns excellent living laboratories for the study animal adaptation. See the sidebar for a fact sheet on anchialine caves.
Anchialine cave-adapted species can include fish and invertebrates, with crustaceans representing over 80% of animal biodiversity in these systems. The transition from the sunlit surface to nearly lightless caves with limited food resources have resulted in unique adaptations, including the degeneration of eyes, loss of pigments, the development of unusual sensory structures (i.e., setae), and the alteration of life cycles. This pattern of evolutionary change is called troglomorphism. Troglomorphs may also exhibit novel physiological adaptations in comparison to their surface relatives, including increased life spans and development times, reduced metabolic rates, and altered feeding structures for cave-specific nutrient sources.
Crustaceans’ unique ability to adapt to these extreme conditions have allowed them to flourish and outcompete other forms of life. Crustaceans found in anchialine caves often share these characteristics with those found in the deep-sea, another area where Heather conducts a great deal of her research. (To learn more about Heather’s work in the deep-sea, see the Virtual Explorations Creep into the Deep and Creep into the DEEPEND.)