Resumen del producto

The embryology of euphausiids has been studied only in temperate and polar broadcast spawning krill species, which apparently have highly synchronized gonad and molt cycles. In the past it has been assumed that these species have gonad development, interbrood period, brood size and proportion of the gonad spawned similar to sac-spawning krill species. This study describes histologically the embryogenesis of the sac-spawning euphausiid Nyctiphanes simplex and explores its temporal association with the gonad development and molt cycle. Swarms of euphausiids were collected in the Gulf of California during July 2007 and March 2010 and incubated shipboard. 115 ovigerous females in different stages of embryonic and gonadal development were preserved, and later processed and stained with various histological techniques. We describe embryogenesis of one cell, multiple cells, morula, blastula, gastrula and early or late limb bud and twiching stages. Larvae hatch as nauplius (N) and develop later as pseudo-metanauplius (PMN). The larvae are released from the ovigerous sac as metanauplii (MN). Ovigerous females with embryos in cell division stage have gonads in the multiplication stage, from nauplius stage some females have pre-vitellogenesis gonad and only females with MN occasionally have gonads in vitellogenesis. The gonad maturity occurs only after completing the release of the embryos from the ovigerous sac. Females with ovigerous sac were invariably in intermolt stage suggesting a precise synchronization among processes of molting, gonad development and the release of the embryos to produce consecutive broods. Lipid storages decrease throughout the embryonic development until the first feeding stage (calyptopis 1).

Palabras clave: histology; Nyctiphanes simplex; embryology; larval development

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