Egg and brood sizes of oceanic pelagic crustaceans

The eggs and broods of crustaceans that carry their embryos attached to their appendages or within a marsupium are examined. Larger crustaceans within an order or suborder have larger eggs than smaller crustaceans but the egg size relative to body size decreases except in 2 groups: the relative volume of the eggs of calanoid copepods and deep-living mysids is maintained at about 1.0 O/O and 0.4 % of body volume respectively across the ranges of size of the females examined. Brood volume relative to body volume tends to remain constant as body size increases and represents about 10 to 15 % of body volume. The constraints on brood volume probably devolve from the possession of a ngid exoskeleton but some variation independent of body volume is possible. Egg size and number are dependent variables. Mysids, euphausiids and decapods divide into species that produce large and those that produce small eggs. There may be a minimum viable size of egg. Consequently, small crustaceans may increase fecundity through production of successive broods whereas larger crustaceans can increase the number of eggs by decreasing egg size. The effect of increased lipid content of large eggs relahve to an increase in egg size and incubation time is discussed.