Meal size and feeding rate of the shallow-water lysianassid Anonyx sarsi (Crustacea: Amphipoda)

Abstract

[Mature or almost mature Anonyx sarsi Steele & Brunel from the Saint Lawrence Estuary and Gulf were held singly and deprived of food for up to 30 d to measure the effect of starvation on feeding response. After a fixed period of starvation, individuals were fed pieces of freeze-dried squid mantle to determine meal size, feeding rate, and satiation time. Average meal size increased steadily, while egestion decreased, over the first 15 d of starvation. The quantity of dry squid ingested after 15 to 30 d of starvation was constant and followed a normal distribution. On average, males (mean body length = 21.7 mm) starved 15 to 30 d ate 8.9 to 9.1 mg (19 to 22 % of net dry body weight). Average meal size of females apparently decreased with increasing sexual maturity: immature Estuary females (mean body length = 20.9 mm) starved 15 to 30 d ate 7.6 mg (13 % of net dry body weight), while mature Gulf females (mean body length = 22.4 mm) ate 7.5 mg (10 % of net dry body weight). The large ovaries were responsible for smaller absolute and relative meal size of females compared to males. Maximum meal size reached 16.1 to 16.4 mg (29 to 37 % of net dry body weight) in females and males, equivalent to 0.1 g of fresh squid. Meal size was positively correlated with body length and with time spent feeding. Average feeding rates of females (0.9 to 1.3 mg dry weight min⁻¹) and males (0.5 to 1.2 mg dry weight min⁻¹) starved 15 to 30 d were similar. Feeding rate was not correlated with the duration of starvation.]