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Marthasterias glacialis (ECHINODERMATA: ASTEROIDEA) POTENTIAL FOR
DEEP-SEA INVASION FROM THE NORTH ATLANTIC.
3.1. Introduction ………………………………………………………………..…….35
3.1.1. Chapter objectives ……………………………………………………..………41
3.2. Material and methods ……………………………………………………………..41
3.2.1. Field sampling and spawning …………………………………………………….41
3.2.2. Temperature/pressure effects on fertilized eggs …………………………………...42
3.2.3. Temperature/pressure effects on larvae ……………………………………………45
3.3. Results ………………………………………………………………………………46
3.3.1. Temperature/pressure effects on fertilized eggs …………………………….…..…46
3.3.2. Temperature/pressure effects on swimming bippinaria at 24 h …………….……54
3.4. Discussion ………………………………………………………………………………55
3.5. Recommendations………………………………………………………………………60
CHAPTER FOUR – REPRODUCTIVE FEATURES OF ASTEROIDS IN THE
PORCUPINE SEABIGHT AND PORCUPINE ABYSSAL PLAIN, N.E. ATLANTIC
AND THEIR RELATION TO DEPTH DISTRIBUTION OF THE SPECIES
4.1. Introduction ……………………………………………………………………...62
4.1.1 Fecundity and egg size ……………………………………………………………..63
4.1.2. Body size ………………………………………………………………………………68
4.2. Material and methods …………………………………………………………..…69
4.2.1. Collection of data ……………………………………………………………………...69
4.2.2. Histology ………………………………………………………………………………72
4.2.3. Image analysis and estimation of fecundity …………………………….……..72
4.2.4. Statistical analysis ………………………………………………………..……75
4.3. Results ………………………………………………………………………………76
4.4. Discussions …………………………………………………………………...…82
4.4.1. Body size, fecundity and egg size ……………………………………………….……82
4.4.2. Depth allocation of the species and possible causes ……………………..……86
CHAPTER FIVE – SYNTHESIS AND CONCLUSIONS
5.1- Factors controlling the bathymetric distribution of species and their effects on early
life-history stages of echinoderms
…………………………………………………….94
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