The role of temperature and maternal ration in embryo survival: using the dumpling squid Euprymna tasmanica as a model

Using a ‘model’ sepiolid, Euprymna tasmanica, this study investigated the role of maternal nutritional and thermal history on egg quality and subsequent embryo survival. E. tasmanica is a multiple spawner, therefore it was possible to track egg quality and hatching success over successive spawning episodes. A two-factor orthogonal experimental design, involving two feeding levels (high and low rations) and two temperatures (summer and winter), was implemented with half of the replicates used to explore embryonic development and the remaining half examining egg-yolk quality via fatty acid analysis. Differences in reproductive output and embryo mortality were largely attributed to maternal ration and not temperature. Females maintained on low ration produced smaller clutches, consisting of smaller eggs and exhibiting higher embryo mortality rates than high ration females. Both batch fecundity and relative hatching success declined over successive clutches. Lipid content was also significantly lower in low ration females, however, the relative quality in terms of lipid and fatty acid constituents was maintained regardless of treatment and spawning frequency. It is suggested that elevated embryo mortality rate in eggs spawned by low-fed females was a function of insufficient maternally derived yolk resources to fuel embryogenesis. Results indicate that maternal nutritional and reproductive history are important determinates for offspring survival, potentially having significant effects on the magnitude of subsequent recruitment events in squid populations.