Blood refractive index and ratio of weight to carapace length as indices of nutritional condition in juvenile rock lobsters (Jasus edwardsii)

Abstract

Nutritional condition reflects food quality and quantity and influences growth rate. Therefore, the ability to measure nutritional condition would be valuable in estimating the potential for growth of captive and wild lobsters. To assess potential indices of nutritional condition, we examined changes in blood refractive index and ratio of weight to carapace length of juvenile rock lobsters to treatments of varying food supply. Blood refractive index was strongly correlated with blood protein concentrations and was a reliable proxy for the circulating protein that is metabolized and diluted during periods of low food and starvation. The moult cycle imposes constraints on blood refractive index, however, so it is essential that the moult stage of the animal be assessed concurrently. Ratios of weight to carapace length were slower to respond to reduced food intake than was blood refractive index but were independent of the moult cycle and may, therefore, be a more direct reflection of nutritional health. These results showed that both blood refractive index and ratio of weight to carapace length are reliable and nondestructive indices of nutritional condition in juvenile rock lobsters.

Health management during handling and live transport of crustaceans: A review

“…Protein is believed to be the main metabolic substrate during starvation (Pascual et al, 2006). Dietary proteins and dietary carbohydrate levels (Pascual et al, 2003) have been shown to effect haemolymph protein concentration and application of blood protein concentration as an indicator of nutritional status has been proposed (Dall, 1974;Moore et al, 2000;Musgrove, 2001;Oliver and MacDiarmid, 2001). Serum proteins and haemocyanin levels were reported to be lower in Hematodinium infected versus uninfected male Callinectes sapidus (Shields et al, 2003).…”

A Global Review of Spiny Lobster Aquaculture

“…Oliver & MacDiarmid (2000) examined blood refractive index and weight/carapace length ratios as indices of condition in juveniles. McLeod et al (2004) studied the changes in the body composition of adult male southern rock lobster, J. edwardsii , during starvation.…”

Haemolymph condition of deep-water southern rock lobsters (Jasus edwardsii) translocated to inshore reefs

“…A small aliquot of the haemolymph sample was then placed in a hand-held refractometer (Model UR-2, Industrial and Scientific Supply Co.) to measure the refractive index (RI). The blood RI values were converted to blood serum protein concentration (as outlined by Musgrove 2001), which is a reliable index of physiological condition (Oliver and MacDiarmid 2001). For the analysis of total haemocyte counts (THCs), which is another common measure of health condition, a 200 mL aliquot of haemolymph was mixed with 200 mL of Na cacodylate based anticoagulant in another Eppendorf tube (4.28 g of Na cacodylate added to 90 mL of distilled water, pH adjusted to 7.0 using 1.0 M HCl, 400 mL of stock 25% glutaraldehyde solution added and volume adjusted to 100 mL with distilled water).…”

“…Haemolymph SP concentrations respond to changes in the haemolymph volume through water uptake or fluid loss, thus lowest SP levels occur in post-moult lobsters when they ingest large volume of water to expand their newly formed exoskeleton (Oliver and MacDiarmid 2001). Blood pH and concentrations of organic and inorganic ions may also alter the total protein concentrations in response to stress (Paterson and Spanoghe 1997), while some proteins may be catabolised as an energy source after glycogen reserves are exhausted.…”