Probably because of folk associations between porta "gate, door" and portus "harbor", the "gateway" to the sea, Portunus later became conflated with Palaemon and evolved into a god primarily of ports and harbors.
Many crustaceans like crabs (Scylla spp., Portunus spp.), spiny lobsters (Panulirus spp.), crayfish (Astacus spp., Cherax spp.) and freshwater shrimp (Macrobrachium spp.) are reported to be infected with variable severities depending on the life stage of the host and presence of external stressors (temperature, salinity, bacterial diseases, pollutants).