Recruitment to the reef
column spacer Recruitment to the reef: sexual reproduction
 
 

Spawning, larval development, & dispersal of larvae

 
This section deals with spawning, larval development, & dispersal of larvae in sea urchins & relatives. The same topic for other reef organisms can be accessed via the icons. Other topics relating to recruitment, namely, SETTLEMENT & METAMORPHOSIS and SURVIVAL DURING EARLY LIFE, are found in their own sections. hot buttons for spawning/metamorphosis/dispersal section of BCCR website hot button for sponges section on spawning/metamorphosis/dispersal hot button for corals section on spawning/metamorphosis/dispersal hot button for snails section on spawning/metamorphosis/dispersal hot button for sea urchins & relatives section on spawning/metamorphosis/dispersal hot button for fishes section on spawning/metamorphosis/dispersal
 
 

Spawning, larval development, & dispersal of larvae: sea urchins & relatives (sea stars, brittle stars, & basket stars)

 
  In sea urchins, as in most other echinoderms, sexes are separate and fertilisation is external. Development in sea urchins leads to a pluteus larva, which has long ciliated arms for locomotion and for collecting phytoplankton for food. After a few weeks feeding and floating in the plankton, the larva settles to the sea bottom and metamorphoses.
 
diagram showing reproductive cycle in sea urchins
 
 

photograph of sea star Linckia guildingiiSpawning and larval development in sea stars follows a similar pattern to that seen in sea urchins. In both groups, potential recruitment from sexual reproduction can number in the millions from a single spawning. Photograph courtesy Anne Dupont, Florida.

 

 

 

 

 

A comet sea star Linckia guildingii can reproduce both sexually,
via larvae and gametes, and asexually, by dropping its arms and growing
new ones. Each dropped arm regenerates a new body. Note in the
photograph that this individual is regenerating a lost arm 0.5X

  Most sea stars, including Linckia, have separate sexes. Gametes are released into the open water, fertilisation occurs, and the first larval stage is the bipinnaria. The bipinnaria feeds on phytoplankton that it collects in its ciliated grooves. After a few weeks floating in the plankton, the bipinnaria transforms into a second larval stage known as a brachiolaria. It is non-feeding and uses its long sensory arms to locate a suitable spot on the sea bottom on which to settle and metamorphose.
 
diagram showing sexual reproduction in a comet star Linckia guildingii
 
 

photograph of brittle star Ophiothrix suensonii courtesy Anne Dupont, Florida
photograph of brittle star Ophiocoma echinataStudies in Belize show that several species of Caribbean brittle stars (ophiuroids) augment normal larval dispersal by floating, or being carried on floating debris, as juveniles. As the larval life-span of ophiuroids is often less than a week, dispersal to new habitats may be greatly increased by this juvenile-floating strategy. The floating juveniles are about 15mm overall diameter. Hendler et al. 1999 Bull Mar Sci 65: 283. Photograph of Ophiothrix suensonii courtesy Anne Dupont, Florida.

Related species of brittle star to the ones
studied in Belize are Ophiothrix suensonii
(Left) and Ophiocoma echinata (Right) 1X

Note the differences in relative arm and spine lengths in the 2 species. As a
small juvenile, Ophiothrix suensonii (Left) would have much greater relative
surface area for flotation than the more chunkily structured Ophiocoma echinata

 
  Let's hear from the brittle stars:
 
cartoon 1 in a series on brittle stars
cartoon 2 in a series on brittle stars
 
cartoon 3 in a series on brittle stars
cartoon 4 in a series on brittle stars
 
 

photograph of basket stare Astrophyton muricatum before spawningphotograph of a spawning basket star Astrophyton muticumBasket stars Astrophyton muricatum spawn their gametes in broadcast fashion at night as shown in the accompanying photos of an individual in Grand Bahama Island. The smaller organisms are epitokous polychaetes attracted to the illumination from the SCUBA-divers’ lights. McMurray et al 2012 Coral Reefs 31: 703.

 

Individual partially expanded
for nighttime feeding 0.25X

 

Male engaged in spawning,
accompanied by swimming
epitokous polychaetes 0.25X

 

 
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