Ovarian cycle and scanning electron micrographs of the spawned egg of female mantis shrimp Oratosquilla massavensis (Alexandria, Egypt)

Mantis shrimp Oratosquilla massevensis is an abundant marine crustacean in Egypt. It is common among the most important predators in many shallow, tropical and subtropical marine habitats. It is poorly understood as many species spend most of their life tucked away in burrows and holes. The objective of this study is to provide information on the histological characteristics of the ovary of female mantis shrimp O. massevensis and the morphology of the spawned egg, using scanning electron microscope. The ovaries showed a pronounced macroscopic differentiation in size and color with the maturation of the ovary, in six developmental stages namely: immature stage, previtellogenesis, primary vitellogenesis, secondary vitellogenesis, maturation and spent stage. Staining affinities of different structural components, size of different oocytes and nuclear sizes, as well as the follicular cells and their association with oocytes were used to differentiate between different oocyte developmental stages. Scanning electron micrographs of the spawned egg of O. massavensis revealed spherical forms of the egg with well noticed stalk or funiculus. The chorion is ornamented as a wrinkled layer with different textures. Two different yolky materials or matrices were observed, the first one constitutes a conical shaped hard matrix with glassy appearance, while the second one appears spongy with somewhat soft appearance

Application of enriched Cyclops abyssorum divergens with mixed algal diet compared to Artemia franciscana for improving larval growth and body composition of Dicentrarchus labrax

Larval rearing techniques with suitable nursery feed should be prioritized for better survival and growth. We evaluate the potential use of Cyclops abyssorum divergens as a natural live food candidate instead of the costly traditional Artemia franciscana in the feeding strategy for Dicentrarchus labrax larvae. C. abyssorum divergens and A. franciscana were enriched with mixed valuable algae strains (Isochrysis galbana, Tetraselmis chuii, Chlorella marina and Nannochloropsis oculata) that were used in equal biomass proportions (1:1:1:1) on dry weight basis. Amino acids and fatty acid profiles were found to be highly significantly different in enriched C. abyssorum divergens (EC) compared to enriched A. franciscana (EA). The findings also revealed compensated deficiency in some amino acids such as histidine, isoleucine, and methionine in EC and also increased levels of total essential amino acids (EAA) in EC by 8.2 % more than that of EA. Further metabolizing of palmitic acid (C16:0) and bio-conversion of α- linolenic acid, ALA (C18:3 n-3) to high accumulation of DHA fatty acid lead to higher PUFAs contents in EC and lower levels in EA. Specific growth rates (SGR) and survival percentages (S %) of D. labrax were higher in larvae fed with EC compared to the lower values in EA. Moreover, analyzing final carcass composition revealed increased levels of DHA fatty acid attaining DHA/EPA ratio in fish-fed EC of 2.95 % (>1) compared to 0.90 % (<1) in larvae-fed EA. The elevated levels of the amino acids in the larvae-fed EC were a yardstick to the surged growth and survival rate of the examined species. The present study concluded that C. abyssorum divergens is the best promising candidate for Sea bass larvae-culture