Southern Rock Lobster Jasus Edwardsii Research Articles

MOLT STAGING IN THE SOUTHERN ROCK LOBSTER JASUS EDWARDSII

A molt staging technique is described for use in the southern rock lobster Jasus edwardsii and estimates are presented for the length of molt stage and of molt cycle in juvenile lobsters.The molt cycle can be divided into 13 stages or substages, of which 10 are relatively easy to distinguish using a combination of cephalothorax rigidity, pleopod epidermis retraction, and setal formation. The stages are similar to those described for other lobsters and crustaceans with interspecific differences, including the length of D0 (apolysis) and the timing of barbule appearance. The application of this technique to field studies is discussed.

Molt Staging in the Southern Rock Lobster Jasus Edwardsii

A molt staging technique is described for use in the southern rock lobster Jasus edwardsii and estimates are presented for the length of molt stage and of molt cycle in juvenile lobsters. The molt cycle can be divided into 13 stages or substages, of which 10 are relatively easy to distinguish using a combination of cephalothorax rigidity, pleopod epidermis retraction, and setal formation. The stages are similar to those described for other lobsters and crustaceans with interspecific differences, including the length of D0 (apolysis) and the timing of barbule appearance. The application of this technique to field studies is discussed.

Respiratory gas transport, haemocyanin function and acid–base balance in Jasus edwardsii during emersion and chilling: simulation studies of commercial shipping methods

The Southern Rock Lobster Jasus edwardsii is a commercial species often shipped in air. Respiratory gas transport, haemocyanin function and acid–base balance were assessed during emersion and emersion with chilling; i.e. reduced packing and shipping temperature. The affinity of the haemocyanin (Hc) for O 2 was low ( P 50=3.44 kPa, 20°C) but was increased by urate and Ca but not l-lactate. Chilling from 25 to 5°C increased Hc-O 2 affinity (Δ H=36.6 kJ mol −1 at pH 7.4) and reduced the Bohr shift from φ=−0.2 to −0.09. In air, non-chilled lobsters became acidotic while chilling induced an alkalosis. The haemolymph P O 2 of non-chilled J. edwardsii in air decreased and the a−v P O 2 difference declined, prompting immediate anaerobiosis. Chilling J. edwardsii lowered metabolism and maintained P aO 2 for up to 5 h in air. Thereafter, emersion depleted the venous O 2 reserve. In non-chilled lobsters a urate-induced increase in Hc-O 2 affinity appeared important but these lobsters were unable to maintain respiration adequately and were reliant on anaerobiosis. As the chilled lobsters warmed they were unable to load adequate O 2 and the venous reserve became depleted. Oxygen transport and respiration were assisted by increased haemolymph urate, and together with chilling enabled O 2 uptake and transport to meet demand for 30 h in air.

Circulatory, respiratory and metabolic response to emersion and low temperature of Jasus edwardsii: simulation studies of commercial shipping methods

The Southern Rock Lobster Jasus edwardsii is a commercial species. The respiratory and metabolic response of J. edwardsii during simulated commercial handling was investigated. Lobsters were dipped in 5°C seawater for 2 min and exposed to air for up to 30 h in shipping cases containing ice (chilled), or packed without chilling. Controls were immersed at 18°C. Chilling ameliorated tachycardia and hyperventilation caused by the packing process. Non-chilled J. edwardsii accumulate an O 2 deficit but chilling lobsters delayed anaerobiosis for up to a day. Haemolymph urate accumulated only in non-chilled lobsters, indicative of a rapid tissue hypoxia. The muscle ATP concentration of J. edwardsii in air decreased, regardless of chilling, with a corresponding loss of energy charge. A hyperglycaemia in emersed J. edwardsii was accompanied by decreased glycogen stores in chilled lobsters. The low IMP concentration in chilled J. edwardsii shows that 30-h emersion stress probably does not compromise taste and value of the lobsters. Chilling extends shipping time and distance, so after 10 or 30 h in transit, the lobsters are largely aerobic. When the chilled lobsters reach their destination after 30 h, accumulated IMP and inosine, and decreased glycogen, may have a significant effect on taste. Recovery is important before cooking if a fresh flavour is desired.

Development of Spines and Sensory Setae on the Tailfan of the Southern Rock Lobster (Jasus edwardsii Hutton, 1875) (Crustacea: Decapoda)

The pattern of development of setae on the dorsal surface of the telson of juvenile southern rock lobsters (Jasus edwardsii) was followed in individual animals through the first six post-settlement stages by collecting and examining their exuviae by scanning electron and light microscopy. The commonest seta is long and plumose, closely similar in appearance to the hydrodynamic receptors of other crayfish and rock lobsters. These occur only on spines raised above the surrounding surface. The spines are arranged in longitudinal columns. New spines are mostly added posteriorly so that the rostral ones are the oldest and largest, although they can also develop in midcolumn. The rate of addition of setae to spines is constant on all spines within and between animals. These two modes of addition occurring together result in an ordered pattern of setal density grading from anterior to posterior and from the midline laterally. This pattern of setal development differs from those described on the tailfan of crayfish and has not been described previously in any crustacean. Because the number of neurons that innervate setae of this type is constant, the developmental pattern may provide insight into the way in which integumental innervation develops.