New records of two trypetesid burrowing barnacles (Crustacea: Cirripedia: Acrothoracica: Trypetesidae) and their predation on host hermit crab eggs

Abstract

Acrothoracican barnacles of the genusTrypetesaare obligate symbionts of hermit crabs that burrow into the gastropod shells occupied by their hosts. In the present study, hermit crabs were examined for the presence of trypetesids, based on collections from the United States, Jamaica, and the Philippines made between 1997 and 2008. Shells from Jamaica and New York containedTrypetesa lateralis, a trypetesid previously documented from central California.Trypetesa lateralisis redescribed based on light and scanning electron microscopy, showing the presence of an external mantle flap and asymmetrical opercular bars diagnostic for this species. The mean prevalence of trypetesids in Jamaica was 8.3% and most barnacles were associated withCalcinus tibicen; in New York the barnacles were found in 1.6% of shells occupied byPagurus longicarpus. Specimens from the Philippines were identified asTrypetesa spinulosa(formerly known only from Madagascar) based on the presence of their diagnostic orificial palps. The mean prevalence ofT. spinulosain the Philippines was 3.7% and most barnacles were associated withCalcinusspp. Hermit crab eggs were observed in the guts ofT. lateralisfrom Jamaica andT. spinulosafrom the Philippines. In both of these regions the trypetesids were found significantly more often in shells occupied by female hermit crab hosts (80–87% with females). These findings suggest the barnacles be classified as transient parasites. The biology of trypetesids is reviewed and a key to the family is provided. Further studies are needed to determine if egg predation occurs in all trypetesids and the impacts on hosts.

History of Discovery of Parasitic Crustacea

“…Other studies have showed blue-green algae-like particles in the gut of Trypetesa lampas (see Kamens 1981), and it may be that barnacles in male hermit crabs filter feed on particles from the water, whereas barnacles in females feed on the hermit crab eggs (Williams et al 2011). Murphy and Williams (2013) verified this study and suggested that the more accurate term for these barnacles may be "transient parasites" as they can be harmful in some cases but cause no harmful impact in other cases. Larsen et al (2016) added that the barnacles do not rely on the egg predation to any substantial degree and found much of the data they collected on prevalence, load, reproductive cycles, and host relationships differed from previous studies.…”

Life Cycle and Life History Strategies of Parasitic Crustacea

“…However, this was predation, not parasitism. Murphy and Williams (2013) suggested burrowing barnacles in hermit crab shells were 'transient parasites' because they somehow consumed hermit crab eggs and preferred female hermit crab shells. In our opinion, burrowing barnacles are not parasites, as least when considering the current available information.…”