Calcium accumulation during the transition from puerulus to juvenile in the western rock lobster, Panulirus cygnus (Decapoda: Palinuridae)

Abstract

Dry weight in P. cygnus increases from 58.4 ± 5.4 mg in pueruli to 88.5 ± 11.9 mg in first-moult juveniles. Changes in ash-free dry weight, from 51.2 ± 4.9 mg in pueruli to 56.7 ± 9.5 mg in first-moult juveniles, are insufficient for the increase in dry weight to be attributable to accumulation of organic matter. The ash weight increased substantially after ecdysis of the puerulus (6.9 ± 2.3 mg for pueruli; 31.9 ± 2.8 mg for first-moult juveniles). This change may be attributed to the process of mineralization, which involves accumulation of calcium salts, and other mineral salts, as well as a range of organic components. Calcium contents, measured with flame emission, increased from 0.46 ± 0.06 mg in pueruli to 1.59 ± 0.26 mg in first-moult juveniles.

Histological studies showed substantial calcium deposits in the gastric mill and mouth region of the juvenile but not of the post-settlement puerulus. Since internal calcium reserves are small in the puerulus, calcium may initially be taken up directly from the sea water following ecdysis.