Hygum, B.H., C. Rey & B.W. Hansen. (2000). Growth and development rates of Calanus finmarchicus nauplii during a diatom spring bloom. Marine Biology, Berlin 136(6):1075-1085.

89612

Hygum, B.H., C. Rey & B.W. Hansen

2000

136(6):1075-1085.

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Growth and development rates were determined for nauplii of Calanus ®nmarchicus (Gunnerus) in the near-shore waters of a western Norwegian fjord from in situ mesocosm incubations. The major food source for the nauplii was diatoms, but Phaeocystis sp., dino¯agellates and ciliates were also part of the diet. At local temperatures ranging from 4.8 to 5.2 °C the cumulative median development time from hatching to Nauplius VI was 19 d. The time taken to molt to the next naupliar stage was approximately constant (3 d) from Stages IV to VI, but Stage III needed the longest development time (5 d). The instantaneous growth rate in terms of body carbon was negative from hatching to Nauplius Stage II, but as high as 0.25 to 0.30 d )1 from Stage III to V. Enhancement of food resources by nutrient addition led to no signi®cant change in speci®c growth rates. Additionally, the cohorts from di7erent nutrient regimes showed almost equal development time, size and body carbon within stages. Length±weight relationships of nauplii from the two di7erent food resources were: W low resources = 4.17 ´10 )6 ´L 2.03 (r 2 = 0.84) and W high resources = 4.29 ´10 )6 ´L 2.05 (r 2 = 0.92), where weight (W) is in micrograms of C and body length (L) in micrometers. The natural body morphology of naupliar stages I to VI is illustrated with digital images, including the ®nal molt from Nauplius VI to Copepodid Stage I. In general, development of the nauplii was faster than that of the copepodids of C. ®nmarchicus, and structural growth was exponential from naupliar stages III to VI. This study validates our earlier results that nauplii of C. ®nmarchicus can obtain high growth and nearly maximal developmental rates at relatively low food levels (?50 lg C l)1 ), suggesting that nauplii exhibit far less dependence on food supply than copepodids.

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