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the larvae controlled the adult distribution. They proposed that larval tolerances affected the rate of colonization and speciation. The authors also proposed that the genus Echinus invaded the deep sea during isothermal glacial periods and that speciation ocurred either by geographical (depth) isolation or by reproductive (temporal) isolation. Reproductive isolation could occur as a result of differences in the timing of spawning in relation to seasonal changes in the vertical flux of organic matter to the seabed (Tyler & Young, 1998). Young et al. (1996b) experimented with early embryos of 7 littoral species of tropical echinoids from Hawaii and the Bahamas and 3 bathyal species from the Bahamas. The embryos were incubated at pressures as great as 300 atm. In every case, embryos tolerated pressures greater than those of their adult normal distributional ranges, but at temperatures found in shallow water. This suggests that pressure does not set actual depth limits for most species and would not prevent recruitment or invasion of depths as great as 2000 m. In research carried out by Sewell & Young (1999) it was concluded that the geographic distribution of the echinoid Echinometra lucunter (Blainville) does not appear to be limited by the temperatures at which normal embryonic/larval development occurs, but by 1) adult temperature tolerances, 2) temperatures needed for growth or spawning, or 3) hydrographic features that limit larval settlement and juvenile survival. Only one experiment has been carried out onto pressure tolerances of a bathyal asteroid species, Plutonaster bifrons (Wyville Thomson) (Young et al. 1996a). The greatest percentage of embryos developing normally occurred at pressures equivalent to 2000 m depth, the depth at which the species is most common. No normal development occurred at a pressure corresponding to 3000 m depth. Therefore, 13
embryonic tolerances could determine the bathymetric limits of distribution for Plutonaster bifrons. 1.2- Larval type and its role in dispersal Dispersal plays a significant part in the establishment and maintenance of biological diversity and is thought to have important consequences at ecological, biogeographic, genetic and evolutionary levels. In ecological time, dispersal potential can influence biological interactions, such as competition or reduction of predation. In addition, the capability of larvae to explore a variety of prospective environments will allow a species to persist in heterogeneous environments (Strathmann, 1974; Palmer & Strathmann, 1981). In evolutionary time, dispersal can increase geographic range of the species allowing 1) exploitation of new habitats, 2) the reduction of inbreeding and 3) the maintenance of genetic continuity between metapopulations (Scheltema, 1986; Wilson & Hessler, 1987). It is generally recognized that, in a given habitat, the distribution and abundance of sessile marine benthic species are controlled by larval recruitment, asexual reproduction and mortality whereas for mobile benthic organisms, immigration and emigration are also important agents of control (Chia, 1989). Demographic features have important implications in community dynamics, particularly considering larval and/or juvenile mortality in relation to successful recruitment events. Community structure regarding larval recruitment is controlled by larval supply, success at settlement, and the mechanisms acting in larval transport at a particular site. These components are very important in order to explain species fluctuation in space and time (Giangrande et al., 1994) and the long term, 14
Page 1 and 2: University of Southampton Research
Page 3 and 4: Graduate School of the National Oce
Page 5 and 6: UNIVERSITY OF SOUTHAMPTON ABSTRACT
Page 7 and 8: Marthasterias glacialis (ECHINODERM
Page 9 and 10: Acknowledgments I know everybody sa
Page 11 and 12: Prière de l’étoile de mer Seign
Page 13: species of asteroid Patiriella para
Page 17 and 18: dispersed over great distances and
Page 19 and 20: lecithotrophic development. The pre
Page 21 and 22: al., 1997). In a review (Vrijenhoek
Page 23 and 24: Although larval dispersal and settl
Page 25 and 26: 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 and 78:
Species Volume Energy Dev Class Ref
Page 79 and 80:
4.1.2- Body Size The reproductive o
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
Page 128 and 129:
Inaba, D. 1934. On some holothurian
Page 130 and 131:
of the 6 th International Echinoder
Page 132 and 133:
Lieberkind, I. 1926. Ctenodiscus au
Page 134 and 135:
McEdward, L.R. and S.F. Carson. 198
Page 136 and 137:
Minchin, D. 1987. Sea-water tempera
Page 138 and 139:
Pawson, D.L. 1976. Some aspects of
Page 140 and 141:
Pingree. R.D., B. Sinha and C.R. Gr
Page 142 and 143:
Savidge, G., H.J. Lennon, and A.D.
Page 144 and 145:
Shilling, F.M. and D.T. Manahan. 19
Page 146 and 147:
Turner, R.L. and J.M. Lawrence. 197
Page 148 and 149:
Vickery, M.S. and J.B. McClintock 2
Page 150 and 151:
(Eds.): Reproduction Genetics and D
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