Laboratory-reared larval stages of Dissodactylus mellitae (Decapoda: Braohyura: Pinnotheridae) and developmental patterns within the Dissodactylus species complex

Abstract

Eggs of Dissodactylus mellitae were incubated for 9–10 days at 28 °C and larval development consisted of three or four zoeal stages and a megalopa. Beginning with the first zoea, the mean duration of successive stages was 5, 3, 4, and 5 days, the first megalopa appearing 10 days after hatching. Among the megalopae obtained, 87% molted from a third zoea, whereas 13% passed through a fourth zoeal stage before metamorphosing to a megalopa. The last zoea is not considered a substage, since it showed no morphological variation, and molting resulted in growth and consistent morphological changes. Compared with other species within the Dissodactylus complex, the development of D. mellitae represents an intermediary level between three and four zoeal stages. The number of zoeal stages of the ancestor of the Dissodactylus species complex cannot presently be inferred. Among larvae of Dissodactylus s.str., D. mellitae zoeae are characterized by a small carapace with relatively long spines and megalopae by a carapace that is as wide as long. The latter can also be distinguished among Atlantic species by the lack of a dactyl on maxilliped 3, by the absence of serrate setae on the chela, and by the blade of the scaphognathite bearing 5 simple setae but lacking a plumodenticulate seta. Within the Dissodactylus species complex significant relationships were determined between egg size and incubation period and between egg size, carapace length, and time to reach the megalopa stage. Another significant relationship was determined between egg size and the duration of the first zoeal stage, but this correlation did not hold for subsequent stages. Differences in survival rates from those of other species may be attributable to differences in diet and the use of antibiotics.