NUCLEIC-ACID LEVELS, CELLULAR-ACTIVITY AND GROWTH DURING THE PUERULUSSTAGE OF THE WESTERN ROCK LOBSTER (PANULIRUS-CYGNUS (GEORGE) DECAPODA, PALINURIDAE)

The potential impact of non-feeding in pueruli of the Western Rock Lob ster Panulirus cygnus (George; Decapoda, Palinuridae) on cellular acti vity and growth was investigated through fluorometric quantification o f nucleic acid levels. Late phyllosomata, post-settlement pueruli and juveniles were collected along the Western Australian coast between Au gust and December 1992, by means of plankton nets and puerulus collect ors. Early phyllosomata were obtained through laboratory rearing. Nucl eic acid levels, as well as dry weights (DW), increased gradually duri ng early phyllosomal stages; the RNA/DNA ratio remained fairly constan t between 0.3 and 0.5 units. During puerulus development, DNA levels ( a measure for cellular growth) demonstrated a slight but insignificant increase; DW remained fairly constant. However, after ecdysis to the first juvenile stage, DNA levels were significantly higher (similar to 0.93 mg DNA . individual(-1)), compared with early post-settlement pu eruli (similar to 0.35 mg DNA . ind(-1)), and increased further during juvenile development (similar to 1.08 mg DNA . ind.(-1) in the second moult juvenile). DW of the second juvenile stage (142.5 mg) was appro ximately double that of the puerulus. RNA levels demonstrated a slight but insignificant decrease during puerulus development, and an increa sing trend during juvenile development. RNA/DNA ratios (an indicator f or cellular activity) are high in the final phyllosoma (1.17 +/- 0.13 units), and decrease significantly during the puerulus stage (to 0.49 +/- 0.05 units in the early post-settlement puerulus) and first moult juveniles (0.26 +/- 0.13 units), and only demonstrates a slight but in significant recovery after the second moult juveniles (0.45 +/- 0.07 u nits). Water temperature appears to have an important impact on RNA le vels, which approach zero immediately after ecdysis to the first juven ile stage when post-settlement pueruli were maintained at 23 degrees C ; those maintained at 18 degrees C did not demonstrate a significant d ecrease. These observations are consistent with absence of feeding dur ing the puerulus stage and further suggest that water temperature may have a substantial effect on puerulus development.