Feeding and Reproduction in Echinoderms Flashcards
What kind of feeders are Asteroids?
Carnivores and scavengers, some suspension feeders
What do asteroids eat?
Snails, bivalves, crustaceans, small fish
How do asteroids catch prey?
Detect prey by chemical cues. Some are sit and wait predators.
Pry open bivalve shells with tube feet/arms. Evert stomach and secrete digestive juices.
What kind of feeders are Ophiuroids?
Suspension/deposit feeders, carnivores and scavengers
How do ophiuroids catch prey using suspension feeding?
Wave arms to create water currents.
Mucous covers underside of arms
Tube feet pass food to mouth
How do ophiuroids catch prey using deposit feeding?
Tube feet gather and sort food
How do ophiuroids catch prey as carnivores/scavengers?
Catch small passing crustaceans or polychaetes with arms
What kind of feeders are regular urchins?
Largely herbivorous
What kind of feeders are irregular urchins?
Deposit feeders
What kind of feeders are Crinoids?
Passive suspension feeders
How do Crinoids catch prey as passive suspension feeders?
Have mucous-covered tube feet. Primary and secondary tube feet capture passing food.
Tertiary tube feet rake food of and pass to the ambulacral groove and onwards to mouth
What kind of feeders are Holothuroids?
Deposit or suspension feeders
How do Holothuroids catch prey as deposit or suspension feeders?
Mucous covered buccal podia around mouth
Food scraped from podia in mouth and recoated with mucous
Suspension feeders often live in burrows/crevices - branched podia
Mobile deposit feeders found on surface - shovel shaped podia
Sedentary deposit feeders burrow - ingesting sand
In what echinoderms is asexual reproduction found?
Asteroids, ophiuroids and holothuroids
What are the main methods of asexual reproduction in echinoderms?
Fission or Autotomy
What happens in fission?
Animal splits down fission plane
Some develop furrow of weakened tissue and/or stretch and split
What happens in autotomy?
Regeneration of whole animal from breaking off one arm
1/5 of the central disc required for regeneration
Which method of asexual reproduction can have anti-predation advantages?
Autotomy
What are the issues with fission and autotomy?
Energy consuming, slow population increases, reduced dispersal, lack of outbreeding
What method of reproduction do the majority of echinoderms use?
Sexual reproduction - release gametes into water column for external fertilisation
What are gametes often released through?
Gonopores
When do many echinoderms breed and why?
Seasonal breeders in spring - coincide with algal blooms
What is the advantage of brood protection?
- Increased survival through protection from remaining in association with an adult, environmental conditions are often improved as well, plus nutrients provided
- Increased parental fitness
Do echinoderms often engage in brood protection?
No, this is rare behaviour
Which group of species commonly brood?
Cold water (Antarctic) species
Where do Asteroids brood eggs?
Mostly brood eggs under arched body
Leptisterias sp. brood eggs in their stomachs
Where do Ophiuroids brood eggs?
Bursae used as brood pouches
In some species young emerge as juveniles
What is the disadvantage of Ophiuroids having large broods?
Large broods can restrict/prevent feeding
Where do Echinoids brood eggs?
External brooders - carry eggs between spines or around peristome surrounding Aristotle’s lantern
Where do Holothuroids brood eggs?
Internally - juveniles exit through ruptures in the body wall. Viviparous - birth live young
What species of Holothuroids provide young with additional nutrients?
Synaptula hydriformis
Where do Crinoids brood eggs?
Often eggs are stuck to pinnules - such as Antedon genus
Some show internal brooding in pouches on pinnules
What are the costs of brooding young?
- Feeding may be reduced with large broods
- Fecundity decreased due to large egg size
- Large eggs are expensive to produce
- Reduced dispersal of young
- But advantages must outweigh otherwise would not have evolved
