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Nearly all models of marine invertebrate reproductive patterns are characterized by having concave regions on the fitness curve, with the two major modes of planktonic larval development, planktotrophy and lecithotrophy always lying on opposite sides of the adaptive valley (McEdward and Miner, 2003). From this result, evolution between planktotrophy and lecithotrophy via natural selection would be predicted to be difficult or impossible, nevertheless phylogenetic analyses indicate that evolutionary transitions between these modes have occurred in a number of occasions (Wray, 1995; Rouse, 2000; McEdward and Miner, 2001). McEdward and Miner (2003) examined the effect of fluctuating food availability on the duration of the planktonic larval period and the number of offspring that survive to metamorphosis in marine invertebrates with planktotrophic development, using fecundity-time models of reproductive strategies. The results showed that when food was abundant, smaller eggs were favoured and fluctuations in planktonic food concentrations affected small-egg strategies more strongly than largeegg strategies, though the variation in fitness was small in relation to fitness differences across egg sizes. Conversely, when food was strongly limited, larger eggs were favoured and fluctuations in planktonic food supply led to variations in fitness that were essentially related to fitness differences inherent in the strategies. McEdward and Miner (2003) concluded that when the extent of environmentally-caused variations in reproductive success exceeds the differences in fitness among reproductive strategies, the adaptive landscape might be flattened, the intensity of disruptive or directional selection could be reduced and this should facilitate evolutionary transitions between planktotrophy and lecithotrophy or vice versa. 77
4.1.2- Body Size The reproductive output (the amount of gametes produced), the reproductive index (the amount of gametes produced per unit body weight), and the reproductive effort (the amount of gametes produced per total amount of production) are all important features of the reproductive cycle of the species. The interspecific variation in body size results in interspecific variation in reproductive output and reproductive index. Within a species, the relation between size and reproductive output is more direct. A certain minimal size of the body is required before an individual becomes reproductive. This may possibly be the body size that is necessary for the individual to be sufficiently functional in terms of feeding to support gonadal growth. The attainment of adult size occurs rapidly and results from allocating most of the acquired resources to growth rather than to reproduction. The trend seems to be to provide for an ever-increasing reproductive capacity until the adult size is reached. A major pattern of echinoderms involves their ability to cease growth when extrinsic food limitation exists. For example, Asterias rubens can stay as small individuals for months in a “waiting stage” before resuming a growth phase that eventually leads to a size at which reproduction may occur (Nauen, 1978). Some populations of Echinocardium cordatum may persist for even years as small individuals without ever becoming reproductive, apparently as a consequence of a low acquisition of nutrients (Buchanan, 1967) When extrinsic food limitation is less extreme, diverse species of echinoids, asteroids and holothurians do not reach their potential growth rate or maximum size but do reproduce (Lawrence and Lane, 1982). In this situation gonadal and somatic growth seem to have an opposite seasonal relationship. The apparent strategy here is 78
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University of Southampton Research
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Graduate School of the National Oce
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UNIVERSITY OF SOUTHAMPTON ABSTRACT
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Marthasterias glacialis (ECHINODERM
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Acknowledgments I know everybody sa
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Prière de l’étoile de mer Seign
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species of asteroid Patiriella para
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embryonic tolerances could determin
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dispersed over great distances and
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lecithotrophic development. The pre
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al., 1997). In a review (Vrijenhoek
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Although larval dispersal and settl
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larvae of shallow water echinoids f
Page 27 and 28: few hours, whereas other species su
Page 29 and 30: een defined as a unique sequence of
Page 31 and 32: therefore a developing form may wel
Page 33 and 34: adults” that have the definitive
Page 35 and 36: The dipleurula is the hypothetical
Page 37 and 38: among tunicate tadpoles, sponge and
Page 39 and 40: Fig.2.4. Bipinnaria larvae of the a
Page 41 and 42: In marine invertebrates there is a
Page 43 and 44: independent of habitat or mode of n
Page 45 and 46: whether juveniles derived from larv
Page 47 and 48: and the northern Mediterranean have
Page 49 and 50: Wares (2001) performed phylogenetic
Page 51 and 52: Fig. 3.2. A. Marthasterias glaciali
Page 53 and 54: 3.2.2- Temperature/pressure effects
Page 55 and 56: Pressure was applied using an Enerp
Page 57 and 58: Fig. 3.7. Bippinaria larvae of Mart
Page 59 and 60: X Data were abnormal. At 150 and 20
Page 61 and 62: X Data all the embryos were abnorma
Page 63 and 64: X Data blastulae, at 200atm 90% of
Page 65 and 66: 50atm more than 90% of embryos were
Page 67 and 68: Those data (Young et al., 1997; Ped
Page 69 and 70: Percentage of individuals swimming
Page 71 and 72: that settling invertebrate larvae d
Page 73 and 74: CHAPTER FOUR- REPRODUCTIVE FEATURES
Page 75 and 76: In 1973, Vance proposed a theoretic
Page 77: Species Volume Energy Dev Class Ref
Page 81: Species Depth of max. Depth range (
Page 84 and 85: arm, and the minor radius (r), from
Page 86 and 87: From Eqs.1 and 3 we obtain the esti
Page 88 and 89: Data on maximum body size, maximum
Page 90 and 91: 250 200 Body size (mm) 150 100 50 0
Page 92 and 93: Fig. 4.7. Hierarchical cluster anal
Page 94 and 95: (Hymenaster membranaceus Thomson).
Page 96 and 97: gamete production at low population
Page 98 and 99: varies depending on the vitellogeni
Page 100 and 101: size, high fecundity, small egg siz
Page 102 and 103: strategy described by Winemiller an
Page 104 and 105: It seems that evolutionary features
Page 106 and 107: strategy stablished by the Winemill
Page 108 and 109: which normal embryonic/larval devel
Page 110 and 111: Larval dispersal from eight populat
Page 112 and 113: These results are very important si
Page 114 and 115: possibility. The opportunistic spec
Page 116 and 117: hypothesis that the Mesozoic and ea
Page 118 and 119: Barnes, H. and H.T. Powell. 1951. T
Page 120 and 121: Chester, C.M. 1996. The effect of a
Page 122 and 123: Crisp, D.J. 1978. Genetic consequen
Page 124 and 125: David, B., A. Guille, J-P. Féral a
Page 126 and 127: Grant, A. 1983. On the evolution of
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Inaba, D. 1934. On some holothurian
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of the 6 th International Echinoder
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Lieberkind, I. 1926. Ctenodiscus au
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McEdward, L.R. and S.F. Carson. 198
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Minchin, D. 1987. Sea-water tempera
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Pawson, D.L. 1976. Some aspects of
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Pingree. R.D., B. Sinha and C.R. Gr
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Savidge, G., H.J. Lennon, and A.D.
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Shilling, F.M. and D.T. Manahan. 19
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Turner, R.L. and J.M. Lawrence. 197
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Vickery, M.S. and J.B. McClintock 2
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(Eds.): Reproduction Genetics and D
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