EGG SIZE, FECUNDITY, AND SPAWNING IN FEMALES OF THE GENUS ILLEX (CEPHALOPODA, OMMASTREPHIDAE)

Ripe egg dimensions in the squid genus lllex are close to the minimum for cephalopods. The average diameter varies significantly depending on species (0.7741.82 mm in /. coindeti,0.75-0.88 mm in /. illecebrosus, and 0.96-1.04 mm in I. argent inus), on geographical distribution intraspecifically, e.g. 1. argentinus (0.96-0.97 mm in the shelf groups and 1.04 mm in the slope oceanic group), and between pre-spawning and spawning females of the summer-spawning shelf group of /. argentinus (0.97 and 0.92 mm, respectively). The potential fecundity (PF), defined as total oocyte stock both in the ovary and oviducts, depends on mantle length (ML) in each species. It varies from 90 000 (ML = 150-160 mm) to 800 000 (ML = 230-250 mm) in !. coindeti, from 200000 to 630000 (M L = 220-280 mm) in /. illecebrosus, and from 75 000 (M L = 150-170 mm) to l 200 000 (ML = 360-380 mm) in Iargentinus. It is possible to estimate the actual value of PF shortly before vitellogenesis begins and up to a start of spawning, when the diameter of the smallest oocytes exceeds 0.05 mm. The summer-spawning shelf females of /. argentinus release about of 70% of PF. Their spawning is intermittent and ripe egg production decreases over time with only a 50% replacement of the initial stock of vitelline oocytes and a decreasing volume of eggs at each release. Feeding activity decreases and the mantle wall and internal organs shrink once spawning commences. In spent animals, a degeneration of both vitelline and protoplasmic oocytes occurs. The squids genus Hex is one of typical r-slrategists among the cephalopods. © 1993 Conseil International pour l’Exploration de la Mer.