In the footsteps of Darwin: dwarf male attachment sites in scalpellid barnacles (Crustacea: Cirripedia: Thoracica) – implications for phylogeny and the evolution of sexual systems

Abundance, placement and sexual identity of the epizoic barnacle Chelonibia testudinaria relative to the size and species of host turtles in Mabul Island, Malaysia

“…Dreyer et al . (2018 b ) found that inward curvature of the ventral transparent lamellae (a thin, cuticular membrane between the mantle rim and mantle cavity) in the receptacle area provides more space for cyprid settlement in larger species, a similar reasoning that can apply to the settlement pits of larger C. testudinaria . However, addressing this hypothesis requires additional measurements of the size of the pits on each hermaphrodite.…”

“…Hence, we hypothesize that a larger hermaphrodite would have a larger settlement pit, thus can house more cyprids that will specifically develop into males. The settlement pits of C. testudinaria can be analogized with the receptacles (areas on the rim of mantle cavity; Dreyer et al ., 2018 b ) of the androdioecious barnacle Scapellum scapellum , where the small complemental males are exclusively attached in the receptacle area of a hermaphrodite partner and never elsewhere (Spremberg et al ., 2012; Høeg et al ., 2016). Dreyer et al .…”

“…More complemental males were found on the larger hermaphrodites, suggesting that substratum space availability is a factor in complemental male recruitment. This is supported in scalpellid barnacles, where the size and shape of the male-housing receptacle area on the scutal shell plates are positively correlated with the number of males attached (Dreyer et al ., 2018 b ). Future insights on the aggregation pattern of complemental males on adult hermaphrodites could be done by using a zonal model to determine settlement behaviour and survival of barnacles in relation to distance of the nearest conspecific from a given individual.…”

“…The settlement pits of C. testudinaria can be analogized with the receptacles (areas on the rim of mantle cavity; Dreyer et al, 2018b) of the androdioecious barnacle Scapellum scapellum, where the small complemental males are exclusively attached in the receptacle area of a hermaphrodite partner and never elsewhere (Spremberg et al, 2012;Høeg et al, 2016). Dreyer et al (2018b) found that inward curvature of the ventral transparent lamellae (a thin, cuticular membrane between the mantle rim and mantle cavity) in the receptacle area provides more space for cyprid settlement in larger species, a similar reasoning that can apply to the settlement pits of larger C. testudinaria. However, addressing this hypothesis requires additional measurements of the size of the pits on each hermaphrodite.…”