The effects of semi-purified diets on growth and condition of Sepia officinalis L. (Mollusca: Cephalopoda).

The effects of five different surimi diets (fish myofibrillar protein concentrate) on growth and condition of Sepia officinalis were evaluated in terms of individual growth using different morphometric and biochemical parameters. A casein supplemented surimi diet produced significant growth (instantaneous growth rate 0.4-0.8% body weight). The digestive gland-to-body weight ratio increased and the cuttlebone-to-body weight ratio decreased significantly in relation to instantaneous growth rate. The RNA content of mantle muscle increased significantly, while the DNA content of mantle muscle did not change in relation to instantaneous growth rate. Mantle muscle protein content was depleted in cuttlefish with instantaneous growth rate < or = 0. No compensatory food consumption, food conversion or growth was observed for cuttlefish fed surimi diets after refeeding them with a natural diet (thawed raw shrimp). Digestive gland and cuttlebone-to-body weight ratios, and RNA content in mantle muscle could be used as short-term indicators of instantaneous growth rate and condition of cuttlefish. Mantle muscle protein content could be used as a long-term indicator.