Egg production and hatching success in the peri-Antarctic copepod Calanus simillimus

Abstract

In situ rates of egg production and hatching success are reported for Calanus simillimus, one of the most abundant calanoid species in peri-Antarctic regions, during the Italian 'Italica' cruise in the Straits of Magellan in March-April 1995. Low fecundity (8.6 eggs female-1 day-1) and fecal pellet production (0.8 fecal pellets female-1 day-1) in this period indicate that the species was feeding very poorly. Sixty-six of the 126 females sampled did not produce eggs and 80 of these did not produce any fecal pellets during the 24 h period of incubation. Striking abnormal naupliar and embryonic development was recorded in 81.8% of the eggs spawned. Aberrant eggs did not undergo normal cleavage, and failed to develop to hatching. Deformed nauplii were asymmetrical and presented strong anatomical anomalies in the total body length and number of swimming appendages. These results are discussed in the light of recent findings on the causes of low hatching success in copepods.