An updated concept and revised composition for Hamacreadium Linton, 1910 (Opecoelidae: Plagioporinae) clarifies a previously obscured pattern of host-specificity among species Author Martin, Storm B. Author Cutmore, Scott C. Author Ward, Selina Author Cribb, Thomas H. text Zootaxa 2017 4254 2 151 187 journal article 33240 10.11646/zootaxa.4254.2.1 64b0d4b0-479e-484a-aaf5-d5237292d4a5 1175-5326 545862 0BDF72E4-5330-4EE7-8560-DF44E71C1F41 Cainocreadium gulella ( Linton, 1910 ) Durio & Manter, 1968 Synonyms: Hamacreadium gulella Linton, 1910 . Records. From Lutjanus griseus , off the Dry Tortugas , Florida , Gulf of Mexico , by Linton (1910) . From L . griseus off Matecumbe Key, Florida by Schroeder (1970) . From Gymnocranius griseus in the South China Sea, by Shen (1985) . From southern red snapper, Lutjanus purpureus (Poey) and the lane snapper, L . synagris , off Columbia, Caribbean Sea by Velez (1978) . Remarks. This species was described from two specimens among the original collection of H . mutabile . Linton (1910) described a Y-shaped excretory vesicle with lateral protrusions extending to the pharynx but McCoy (1930) found this to be a mistake; the excretory vesicle is simple and reaches only to the ovary. McCoy (1930) determined the life-cycle of C . gulella and found it and H . mutabile share the same first intermediate host, a turbinid snail, Lithopoma americanum (Gmelin) [as Astraea americana (Gmelin) ]. Linton (1910) reported only two specimens of C . gulella from 69 L . griseus , but 66 of those same fish were infected with H . mutabile (prevalence 95.7%) with densities of up to 50 worms per fish. McCoy (1930) confirmed that natural infections of C . gulella in L . griseus are both less prevalent and less intense than those of H . mutabile . Through experimentation, McCoy (1930) also showed that, when infected with high densities of C . gulella , L . griseus appeared to be able to rapidly lose most or even all of the parasites, and that fish previously infected with a heavy load of C . gulella were more resistant to subsequent infection of that species; fewer worms established and those which did were smaller. Neither of these observations appeared to be true of H . mutabile for the same host ( McCoy 1930 ). The combined evidence of Linton (1910) and McCoy (1930) might suggest that L . griseus is only an occasional or incidental host for C . gulella . Although his experiments focussed on L . griseus , McCoy (1930) experimentally demonstrated that C . gulella could establish in two other lutjanids ( L . apodus and O . chrysurus ) but failed to establish in a carangid, kyphosid, pomacanthid, serranid and a sparid. The record of Shen (1985) is dubious because of the geographical separation from the type-locality.