Variability in egg and jelly-coat size and their contribution to target size for spermatozoa: a review for the Echinodermata

Abstract

Fertilisation and development in broadcast-spawning marine invertebrates depends on the ability of the egg to attract spermatozoa and provision progeny. Echinoderm eggs have a jelly coat that facilitates sperm–egg collisions. We investigated variation in egg volume and target area for spermatozoa provided by the jelly coat within and between three sea urchin species (Heliocidaris erythrogramma, Heliocidaris tuberculata, Centrostephanus rodgersii), as well as across 22 echinoderm species for which data are available. Egg and jelly-coat size varied within spawns of individual females, between females of a species and between species. The jelly coat increased egg target area by 125–489% for echinoids with planktotrophic development. In general, planktotrophic echinoids (n=16) with larger eggs had thicker jelly coats, as did H. tuberculata females with larger eggs. Variability in egg and jelly-coat size within a species indicates that these traits are prone to maternal effects and may be influenced by factors such as sperm environment and offspring fitness that drive selection on egg investment. The greater variability in jelly-coat size compared with that of the egg has a large potential to affect fertilisation and should be considered in models of fertilisation kinetics. Egg size alone cannot be used as a metric to infer target size for spermatozoa.

Egg size‐mediated sex allocation and mating‐regulated reproductive investment in a haplodiploid thrips species

“…The importance of egg size for fertilization success is also known for some diplodiploid animal species. For example, in free‐spawning marine invertebrates, larger eggs have a higher chance of collision with sperm (Deaker et al., 2019). Likewise, egg size‐dependent mechanism may also apply in some diplodiploid insects where smaller eggs remain unfertilized, do not hatch and then act as trophic eggs for hatched siblings of the same clutch (Kudo et al., 2006).…”

Crown of thorns starfish life-history traits contribute to outbreaks, a continuing concern for coral reefs

“…Aggregation by adults during spawning [ 55 ] would increase the chances of syngamy and promote genetic diversity [ 56 , 57 ]. The eggs of COTS at ∼220 µm diameter are unusually large for a sea star with planktotrophic development [ 58 ]. Larger eggs benefit fertilisation by providing a larger target size for sperm [ 59 ].…”

Women in marine science in Australia

“…With this backdrop, Marine and Freshwater Research brings together 12 contributions led by women and involving other women (or men) as co-authors (Buddle et al 2019;Coleman et al 2019;Day et al 2019;Deaker et al 2019;Green et al 2019;Heupel et al 2019;Joyce et al 2019;Lara-Lopez et al 2019;Morgan et al 2019;Schaefer et al 2019;Wood et al 2019;Woodings et al 2019). These contributions span a diversity of fields within marine science and represent ,40 women across all career stages from ,20 institutions.…”