Energy partitioning within the developing eggs and early juveniles of the gastropod Pomacea canaliculata was investigated from the time of fertilization to newly hatched snails. The forms and locations of the energy stored as well as their changes while development proceeded were studied in six stages (from morula to 3-day hatchlings). The rates of utilization of different lipid classes, protein classes, and total carbohydrates were measured for the first time in embryos and perivitelline fluid.Perivitelline fluid is the primary energy store. Its biochemical composition at stage I is represented by carbohydrates, proteins, and lipids with 34.8%, 13.0%, and 1.5% dry weight, respectively. Dry weight of eggs showed no significant increase during development, indicating there was no important mass exchange with the medium.Carbohydrates and proteins were identified as the major energy-providing components, and lipids as the minor one, contributing 142, 56, and 12 cal/100 mg egg, dry weight, respectively. The overall conversion efficiency (CE) was 32.8% (calculated as percentage of perivitellus energy transformed into embryonic tissues). Carbohydrates were the most important energy reserve supplying virtually all the catabolic demand (CE 14.6%).Protein electrophoretic profiles during embryogenesis showed three distinct phases: An accumulation period (up to stage IV); a more active accumulation and selective utilization phase (stage V), and a selective consumption and protein synthesis period (hatchlings). Structural lipids from perivitellus (phospholipids and free sterols) were selectively conserved in embryos and juveniles, whereas triacylglycerols, hydrocarbons, and esterified sterols were preferentially depleted by hatchlings.Therefore, protein and lipid reserves in P. canaliculata perivitellus provide structural precursors during embryogenesis, while they partially contribute to the energy supplied by carbohydrates.

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Energy partitioning, composition of lipids and fatty acids, and their utilization by embryos were determined in the lecithotrophic shrimp Macrobrachium borellii during seven development stages. The biochemical composition at stage I is represented by lipids, proteins, and carbohydrates, with 29.3, 28.7, and 0.2% dry weight, respectively. The former two were identified as the major energy-providing components, contributing 131 and 60 cal/100 mg egg, dry weight, respectively. The overall conversion efficiency (CE) was 45.0% (calculated as percentage of vitelline energy transformed into embryonic tissues). Lipids were the most important energy reserve (CE 39.3%), followed by proteins (CE 57.1%), both being simultaneously utilized during development while carbohydrates were synthesized de novo (CE 587.5%). Variation in the lipid class composition of embryos and vitellus showed an accumulation of triacylglycerols (TAG) and phospholipids (PL) up to stage IV, a more active accumulation and selective utilization phase (stages V and VI), and a consumption and de novo synthesis period until hatching. Structural lipids (PL and cholesterol) and pigment astaxanthin were selectively conserved in embryos, but TAG, hydrocarbons, and esterified sterols were preferentially depleted. Monounsaturated fatty acids (FA) were the major group in TAG, whereas polyunsaturated FA (PUFA) were the major group in PL after organogenesis. Certain PUFA such as 22:6n-3 and 20:5n-3 were selectively accumulated in PL.