A histological atlas for the Palinuridae (Crustacea: Decapoda: Achelata): A guide to parasite discovery and spotting the abnormal in spiny lobsters.

Crustaceans suffer from diseases that can alter their survival and ecology with additional economic consequences for fisheries and aquaculture. Many parasites have been described from crustaceans and with the advent of novel technologies such as next generation sequencing, the discovery of novel parasites has become increasingly efficient. Molecular techniques are beginning to surpass more conventional tools for parasite discovery, but they typically do not provide information on pathology. Histopathology remains one of the least expensive methods for parasite discovery and allows for both detection of parasites and descriptions of the pathology they cause. When used in concert with modern molecular and electron microscopy techniques, the approach is powerful; however, there are few informational tools for the interpretation of histological slides from crustaceans. Those available do not provide comprehensive images of all organs and early works were limited to lower resolution than currently available. More recent texts provide in-depth details of infection in histological section, but few provide images of healthy material or describe a baseline from which to compare. Here, we provide a series of image plates derived from histologically processed tissues from three palinurid lobsters: Panulirus argus, Palinurus elephas and Panulirus guttatus. Histology from these lobsters shows high visual similarity in all tissue types. We provide a histological atlas of healthy tissue that can be used as a baseline resource for pathobiologists working on these common species (and related crustaceans) and we discuss how disease may result in visual aberrations to these tissues.

White spot syndrome virus and the Caribbean spiny lobster, Panulirus argus: Susceptibility and behavioral immunity.

The Caribbean spiny lobster Panulirus argus is susceptible to infection by Panulirus argus Virus 1 (PaV1), the only virus known to naturally infect any lobster species. However, P. argus is able to mitigate PaV1 transmission risk by avoiding infected individuals. P. argus may also be susceptible to another lethal virus, White Spot Syndrome Virus (WSSV). WSSV has not been documented in wild populations of spiny lobsters, but has been experimentally transmitted to six other lobster species from the genus Panulirus. Although WSSV has been detected intermittently in wild populations of shrimp in the Caribbean region, the risk to P. argus has not been evaluated. Potential emergence of the disease could result in fisheries losses and ecological disruption. To assess the risk to P. argus, we tested its susceptibility to WSSV via injection and waterborne transmission. We also tested whether healthy lobsters can detect and avoid conspecifics with qPCR-quantifiable WSSV infections. We found P. argus to be highly susceptible to WSSV via intramuscular injection, with mortality reaching 88% four weeks post inoculation. Panulirus argus was also susceptible to WSSV via waterborne transmission, but WSSV burden was low after four weeks via qPCR. Behavioral assays indicated that P. argus can detect and avoid conspecifics infected with WSSV and the avoidance response was strongest for the most heavily infected individuals - a response comparable to PaV1-infected conspecifics. Panulirus argus is the first spiny lobster found to be susceptible to WSSV in the Americas, but it is possible that a generalized avoidance response by healthy lobsters against infected conspecifics provides a behavioral defense and may reduce WSSV infection potential and prevalence. Preliminary evidence suggests that the infiltration of hemolymph constituents into the urine may be the source of the avoidance behavior and could therefore extend to other directly transmitted pathogens in spiny lobster populations preventing them from becoming common in their population.