Active parental care in the peppermint shrimp Lysmata boggessi: the effect of embryo age and circadian cycle

The presence/absence of active parental care (APC) was tested in the simultaneously hermaphroditic shrimp Lysmata boggessi . Lysmata boggessi was predicted to engage in APC given that the egg masses spawned by hermaphrodites are > 1 mm thick, the theoretical limit that allows sufficient oxygen supply by diffusion in living tissue. Furthermore, APC was predicted to increase in intensity with embryo development. Lastly, the ultrastructure of appendages used for APC was examined and it was predicted that these appendages will bear specialized structures to aid in this function. Hermaphrodites brooding early and late embryos were collected August–November 2017 from near Tavernier, Florida, USA (25.0115°N, 80.5151°W), transported to the laboratory, and maintained in aquaria to describe and quantify APC during day and night. The morphology of an appendage involved in APC was compared with two other appendages not associated with APC using scanning electron microscopy. Lysmata boggessi engaged in APC likely using some behaviors to clean (e.g., grooming using second pereiopods) and provide oxygen to the eggs (e.g., pleopod fanning). Pleopod fanning was performed more frequently by hermaphrodites carrying late compared to early embryos, likely permitting hermaphrodites to minimize problems related to oxygen limitation in older more metabolically active embryos. Lysmata boggessi also engaged in APC both day and night. The 2nd pereiopods have setae that may be well suited for aiding in APC. This study supports evidence that small brooding marine invertebrates that produce small but compact embryo masses engage in APC.