to changes in the levels of hemolymph dopamine in its intermediate host, the crab Hemigrapsus crenulatus. These changes in the biogenic amino levels can cause behavioral changes such as changes in response to external stimuli resulting from neurological damages (escape behavior), increased conspicuity resulting from modified pigmentation and/ or behavior and castration. Previous studies have also shown that crabs infected with cystacanths exhibit higher metabolic rates and activity levels than non-parasitized crabs. The free living conditions of cystacanths in the hemocoelomic cavity of the intermediate host maybe interpreted as the direct way of altering the dopamine metabolic pathway. The alteration of dopamine levels in the hemolymph system implies that there is a generalized effect of the parasite on the body of its intermediate host, rather than an effect on the nerve ganglion level. Therefore, the increase in activity and metabolic rates for this host parasite system could be a consequence of higher metabolic cost of maintenance for the host, linked to the synthesis of monoamines and/ or the physiological consequences of their bio-availability. This altered physiological condition is beneficial for the parasite, considering that their final goal is to increase transmission by increasing the probability of predation on the intermediate host (the crab) by its definitive host (the gull). Species Profilicollis altmani (Perry, 1942) Van Cleave, 1947 Infects mole crabs as intermediate hosts in North and South America. Final hosts include scoters, Melanitta spp.; gulls, Chroicocephalus maculipennis, Leucopheus pipixcan, Larus modestus, and L. dominicanus; lesser scaup, Marilla affnis; sanderling, Calidris alba; dunlin, Calidris alpina; whimbrel, Phaeopus hudsonicus; rhinoceros auklet, Cerorhinca monocerata; and willet, Catoptrophorus semipalmatus. This species was moved to this genus by Van Cleave in 1947. This species was redescribed in great detail by Amin et al. in 2022 on the basis of specimens from Pacific mole crab Emerita analoga (Hippidae) and Belcher's gull Larus belcheri (Laridae), in Peru. Profilicollis antarcticus (Zdzitowiecki, 1985) Infects shore crabs such as Hemigrapsus crenulatus and gulls such as Larus dominicanus in Chile and New Zealand. Profilicollis arcticus (Van Cleave, 1920) Profilicollis botulus (Van Cleave, 1916) Infects shore crabs such as Hemigrapsus oregonensis and the invasive green crab Carcinus maenas as well as the lobster Homarus americanus. Its final hosts are shorebirds such as common goldeneye, Bucephala clangula; Barrow's goldeneye, B. islandica; greater scaup, Aythya marila; eider duck, Somateria mollissima; and long-tailed duck, Clangula hyemalis. Profilicollis chasmagnathi (Holcman-Spector, Mane-Garzon and Dei-Cas, 1977) Infects estuarine