Published online by Cambridge University Press: 11 May 2009
Spirontocaris lilljeborgii is a dioecious species and no protandrous hermaphrodites have been seen.
The majority of males become sexually mature in the first year (7–9 months). Some of these may die after fertilizing the females and the majority die after fertilizing the females for a second year (18 months old).
Only a small proportion of the females breed in their first year, all breed during their second year and a few appear to live for a third year.
A first-year female lays from 130 to 160 eggs, and the usual output of a second-year female is from 450 to 650 eggs.
Egg laying begins at the end of November and hatching is complete by the end of March.
The total incubation period is about 90 days. Eye pigmentation first appears at about half the incubation period (47 days).
Juveniles can be distinguished as males and females by the shape of their pleopods within 4–6 months of hatching.