Temperature and laboratory feeding rates in Carcinusmaenas L. (Decapoda: Portunidae) larvae from hatching through metamorphosis

Abstract

Larvae of Carcinus maenas L. were reared in the laboratory and temperature-dependent stage durations of successive instars were examined at 12, 15, 18, and 25°C. Feeding rates (FR), in numbers of newly hatched Artemia nauplii, biomass, and energy consumed by a single crab larva during 24 h, were measured daily through the moulting cycles of all larval stages at the four temperatures. Dry weight (DW) and elemental content of carbon (C), nitrogen (N) and hydrogen (H) were analysed in newly hatched (0 h) and 1-day-old (24 h) Artemia nauplii at six temperatures (6, 9, 12, 15, 18, 25°C). Due to a 24 h feeding regime, the temperature dependent “mean nutritive value” of newly hatched brine shrimp nauplii is defined, individual biomass (DW, C, N, H) and energy (Joule) 12 h after hatching. General figures in changing individual daily FR, and temperature-dependent peculiarities are discussed. The total amount of food ingested by successive larval instars increases exponentially, while the increasing cumulative quantity consumed by individual crab larvae on successive days of development is described by power functions. At higher temperatures significantly less absolute biomass and energy is consumed during the entire larval development. C. maenas megalops are the main energy consumers in larval life, contributing 41 to 67% (12 to 25°C) to the total larval energy intake between hatching and metamorphosis. Larval ability to adapt to increasing metabolic costs for maintenance in higher water temperatures is discussed with average daily feeding rates (AFR). Improved efficiencies are presented for the cumulative larval energy budget, 31% in assimilation, and 4.4% in gross growth (K 1).