The use of histology, molecular techniques, and ex situ feeding experiments to investigate the feeding behavior of the coral reef predator Hermodice carunculata, the bearded fireworm




Lewis, Staci A.

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Three studies on the invertebrate corallivore Hermodice carunculata, commonly known as the bearded fireworm, were conducted to provide baseline information on the general anatomical features, nutritional requirements, feeding behavior, and growth rates of this poorly documented reef inhabitant. Through histological techniques, the species’ feeding mechanisms, digestive system, and sensory structures were studied to understand its ability to adapt to a changing reef habitat. Several previously unreported features were observed including a simple layer of cells on the outer cuticle resembling, and the size of, bacteria, a specialized tissue in the foregut, and pigment granules penetrating the ventral cuticle at the nerve cord connection. This study also documented the appearance of gut content in the digestive tract and the presence of secretory cells on the proboscis. These observations provide insight into the feeding behavior of H. carunculata. Ex situ feeding experiments were conducted in Barbados to monitor organisms’ weight change in different coral reef feeding regimes as an indication of nutritional value of coral species. During the experiments, H. carunculata specimens experienced a Millepora complanata feeding regime and a short time period in a Montastraea annularis feeding regime. In both experiments, the average weight change was not statistically significant, which indicates the H. carunculata specimens did not gain weight in the presence of M. complanata. These results suggest H. carunculata may supplement their diet with other food sources to meet nutritional requirements. Finally, during an outbreak of an unknown white syndrome on coral colonies in the Flower Garden Banks National Marine Sanctuary, field samples, including H. carunculata specimens associated with the coral tissue loss margins, were collected to test the use of the Polymerase Chain Reaction (PCR) and DNA fingerprinting to identify H. carunculata associated with tissue loss lesions. Specific H. carunculata primers were designed to amplify H. carunculata DNA in the samples. The H. carunculata tissue samples (positive controls) were the only samples amplified during the PCR tests. These results suggest H. carunculata organisms do not leave detectable amounts of DNA at foraging sites. However, future molecular tests should be conducted using other target sequences for amplification and take into considerations the sensitivity of conditions including the number of PCR cycles.



Corallivore, Hermodice carunculata, Coral disease, Histology, Feeding behavior, Fireworm