Female reproductive output in the squid Loligo pealeii: multiple egg clutches and implications for a spawning strategy

We examined actual and potential reproductive output with particular attent ion to the females' abilities to lay multiple clutches of eggs. Combining t he results of 2 summer spawning seasons, 28 of 47 females that laid eggs in captivity produced substantial clutches (i.e., 5 or more egg capsules per clutch) at least twice. Multiply-ovipositing females exhibited a variety of patterns of oviposition, ranging from relatively small clutches at short i ntervals to large clutches several weeks apart. Actual reproductive output varied greatly between females. In both years, the number of egg capsules a nd ova laid showed a negative relationship with the combined mass of the ov ary and oviduct at the time of death. Separate correlations between the num ber of ova laid and the combined number of oocytes and ova remaining in the reproductive tract at death revealed a similarly negative, although statis tically weaker, relationship in both years. Most importantly the number of ova laid in captivity (mean = 11800 in 1993 and mean = 15 293 in 1998) exce eded the combined number of ova and oocytes remaining at death (mean ca 450 0 in both years) by roughly 3 x, providing an indication of the extent to w hich only counting remaining oocytes and ova can underestimate fecundity. T he ages of ovipositing females spanned 4 to 6 mo, Interestingly, neither ag e nor mantle length consistently affected reproductive output, i.e., short young females could be just as fecund as longer older females. A supplement ary feeding experiment failed to demonstrate an effect of feeding regime on captive Lifespan or reproductive output. The females in one year (1998) we re maintained in isolation without access to males; these females laid fert ilized eggs, some over periods of 15 or more days, demonstrating the use of stored sperm. For females that had oviposited in both years, the oocytes r emaining in the ovary always ranged greatly in size and structure. Thus, th e 'spawning strategy' of Loligo pealeii appears to involve multiple oviposi tions over weeks or months, with oocytes possibly being developed continual ly. Placing the results of this study in a larger context, reproduction by females in this and other loliginids most likely entails copulation with mu ltiple males and the laying of multiple clutches of eggs, possibly in diffe rent locations.