Habitat

Dardanus megistos is a species associated with coral reefs. Larger individuals inhabit deeper waters of the lower reef slope (Tudge 1995), typically to 50m but as deep as 100m (Poupin and Juncker 2010), but smaller individuals are not uncommon across the reef crest and flat. This was the case at Heron Island and a similar pattern has been recorded from Kenya (Reay and Haig 1990), where it was found only from the reef crest and occasionally from lagoonal bommies. Hence D. megistos appears to prefer a rocky or structurally complex habitat (consistent with records of Haig and Ball 1975), never being observed from the sandy substrate of the lagoon on Heron Isand, where the sympatric and ecologically most similar D. lagopodes was abundant.

Followed closely by D. lagopodes, D. megistos is reportedly the most common of six Dardanus species from Kenya (Reay and Haig 1990), a pattern potentially extending across its East African distribution. At Heron Island D. megistos likewise appeared to most closely share its habits with D. lagopodes, here however the latter appeared to be the more common species.

It has been suggested that hermit crabs may use algal or seagrass beds as recruitment habitats, harbouring juveniles before they move onto the reef proper (Litulo 2005). This hypothesis has seen some support from research conducted in Fiji (Alfaro et al. 2009), which found D. megistos to be inhabiting such beds.

Photo: Storm Martin, Heron Island, 2012