Caught in the Act!  This pair of mating amphipods was found in the Ulva area.  The larger male often clasps the smaller female for days at a time, hoping to mate with her when she molts.

The majority of the fauna observed in False Bay consist of polychaete worms, bivalves, snails, and crustaceans. Reproductive strategies can be divided into two categories: those species in which development takes place away from False Bay in the plankton (free-spawning and epitoky), and those in which development occurs benthically in the bay (oviposition and brooding). This page will focus on a sampling of species exhibiting these habits.
 
 
Free-Spawning

The majority of the fauna observed in False Bay spend part or all of the larval stage in the plankton. The sand dollar Dendraster excentricus spawns both eggs and sperm (separate individuals) in late spring/summer. Although cues for spawning are unknown, it has been suggested that following low tide, spawning is induced by the influx of cold water on the incoming tide (Strathmann 1987). This strategy would ensure that Dendraster embryos are carried safely out into the plankton on the next ebb tide and also that embryos are not exposed to the harsh, hot conditions of low tide at False Bay.  Sand dollar larvae spend a variable period of time in the plankton, and often prefer to settle near pre-existing populations of adults (Strathmann 1987).
 

Epitoky

Epitoky is an unusual mode of reproduction unique to polychaetes in which the worm undergoes a partial or entire transition into a pelagic, sexually reproductive morph known as an epitoke. Polychaete epitokes can often be seen swarming around submerged lights during summer nights in the San Juan Islands. In many cases, epitoky involves loss or degeneration of digestive structures and enhancement of swimming, sensory, and gonadal structures (Strathmann 1987). In the case of False Bay, worms such as nereids and glycerids that engage in epitoky leave the sandflats and enter the plankton in order to reproduce. Populations are replenished when larvae come in on the incoming tide and settle out of the plankton to take up the benthic lifestyles of adult polychaetes.
 
 
Benthic Oviposition

Many snails and some worms of False Bay lay their eggs in gelatinous masses anchored to sand, algae, or bits of debris.  Bubble snails such as Melanochlamys and Haminoea develop in embryo masses to at least the veliger stage, at which time they become planktonic for a period before settlement.  Embryo masses are exposed to extreme temperature fluctuations and other hazards of low tide, as well as predation at both high and low tide.
 
 
 

Haminoea adult	Haminoea egg mass

Brooding

Many False Bay animals, particularly arthropods, exhibit brooding behavior. Upogebia pugettensis, the mud shrimp, carries eggs cemented to its abdominal appendages throughout the winter.  Larvae are released in spring and spend 2 or 3 weeks, as a stage called a zoea, in the plankton before returning to the mud flats on nocturnal spring flood tides (Dumbauld et al 1996). Brooded embryos and larvae are protected from predation and from the worst extremes of tidal fluctuations. However, brooding incurs a significantly higher cost of reproduction to the female parent than reproductive strategies in which parental responsibility ends with egg release.
 

Brooding female Upogebia, ventral view.  The eggs are cemented to the abdominal  appendages, called pleopods, to the left.