MFWB_A - Echinoderm Feeding and Reproduction

asteroids feeding

carnivores, scavengers, some suspension, snails, bivalves, crustaceans small fish, detect by chemical cues, some sit and wait, can pry open bivalve with tube feet/arms, even stomach and secrete digestive juices, solidify catch collagen to keep shell open (can be just 0.1mm)

ophiuroids feeding

suspension - wave arms to coat water currents, mucous covers underside of arms, tube feet gather and pass to mouth, deposit - tube feet gather and sort food, carnivores/scavengers - catch small passing crustaceans or polychaete with arms

echinoids feeding

reg - largely herbivorous, irreg - deposit feeders

example of echinoid feeding

Aristotles later - jaw made of 5 arrowhead shaped ossicles, crash in sea otters in Alaska led to devastation of kelp forests by urchins, crash in black urchin in 1983 affected algal growth on caribbean coral reefs

crinoids feeding

passive suspension, mucous covered tube feet, primary and secondary tube feet capture passing food, tertiary tube feet rake off food and pas to ambulacral groove and to mouth

holothuroids feeding

deposit/suspension feeders, mucous covered buccal podia around mouth, food scraped off in mouth and recoated with mucous, branched podia (burrows), mobile deposit feeders found on surface - shovel shaped podia, sedentary deposit feeders burrow - ingesting sand

asexual reproduction

offspring genetically identical to parent, asteroids, ophiouroids and holothuroids, fission or autotomy, energy consuming, slow population increases, reduced dispersal, lack of outbreeding

fission

animal splits down fission plane, some develop furrow of weakened tissue and/or stretch and split, can use tube feet to pull body apart, e.g.,odd rayed star - obligate fissiparous reproducers (no gonads), sclerasterias only reproduce this way as juveniles, holothuroids twist and stretch body to split

autotomy

regeneration of whole animal from breaking off one arm, one fifth of central disc required, can have anti-predation advantages

sexual reproduction

most external, pentamerous gonads found in: arms (asteroids, pinnules (crinoid), bursae (ophiouroids), inter-ambulacral regions (echinoids), gametes released through gonopores, seasonal breeders (spring) to coincide with algal blooms

brood protection

increases survival by protection from remaining in association with adult, rare, cold water species commonly, often produce large yolky eggs

asteroid brood protection

under arched body, e.g., leptisterias brood in their stomachs

ophiuroids brood protection

bursae used as brood pitches, e.g., small brittlestar has no known larval stage and young emerge as juveniles, large broods can restrict/prevent feeding

echinoids brood protection

external brooders, carry eggs between spines or around peristome surrounding Aristotles lantern

holothuroids brood protection

internally, juveniles exit through ruptures in body wall, exhibit viviparity - birth live young, Synaptula hydriformis provide young with extra nutrients

crinoids brood protection

eggs stuck to pinnules (antendon genus), some show internal brooding in pouches on pinnules

brood protection advantages

increased survival chance, parental fitness increases

brood protection disadvantages

feeding may be reduced, fecundity decreased due to large egg size, large eggs expensive to produce, reduced dispersal of young