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DECLARATION This thesis is the result of work completed wholly while registered as a postgraduate in the School of Ocean and Earth Science, University of Southampton. 3
UNIVERSITY OF SOUTHAMPTON ABSTRACT FACULTY OF SCIENCE SCHOOL OF OCEAN AND EARTH SCIENCE Doctor of Philosophy REPRODUCTION AND LARVAL BIOLOGY OF NORTH ATLANTIC ASTEROIDS RELATED TO THE INVASION OF THE DEEP SEA by Francisco Benitez Villalobos A very important objective of ecological research is to explain the evolution of life histories, more specifically how natural selection modifies reproduction and development in order to generate the patterns that are observed in nature. With few exceptions, the reproductive mechanisms and patterns found in deep-water echinoderms are entirely similar to those found in shallow-water species. The aims of this study were 1) to examine the reproductive biology of the many deep-sea asteroids found on the continental slope to the west of Europe in order to determine if the reproductive adaptations are a function of depth, distribution or are phylogenetically controlled, and 2) to conduct experiments on the effects of pressure and temperature on larval development of Atlantic asteroids, to investigate the physiological potential for deep sea invasion by shallow-water species. Eggs of the shallow-water asteroids Asterias rubens Linnaeus and Marthasterias glacialis (Linnaeus) were fertilized in vitro and incubated through the early embryonic cleavages until the larval stage. They were subjected to different temperature/pressure regimes. Early embryos were able to tolerate pressures up to 150 atm at 15 o C and 100 atm at 10 o C. Survivorship of A. rubens swimming bipinnaria remained high (> 70%) after incubation at all the pressure/temperature combinations. In M. glacialis the highest survival of swimming larvae was 100% at 1 atm/5, 15 and 20 o C and 50 atm/15 and 20 o C. Data for the temperature and pressure effects on the later stages of development suggest that all the larval stages are more temperature/pressure tolerant than the early embryos and survivorship becomes greater with larval age. Therefore, the larvae of these two species could survive transport to deeper waters and these species may be capable of sending colonists to the deep sea. In the deep NE Atlantic the habitat has selected for species with specific reproductive traits, which provide them with successful and advantageous life history strategies. This can be clearly observed in the upper bathyal zone between 700 and 1100 m, where the environmental conditions have selected for small species with low fecundity and large eggs, plus habits related directly or indirectly with suspension feeding. These species exhibit reproductive features with trends to the opportunistic strategy and are distinctive of unpredictable environments, although their large egg size probably follows the general trend observed in species from cold waters in order to provide the larvae with energy sufficient for a high survival possibility. Conversely, phylogenetic and evolutionary factors are also important and seem to be decisive at the deepest waters where basically mainly species belonging to the strict deep-sea family Porcellanasteridae are found. All these species possess a mixture of features typical of classical K strategists and equilibrium strategists, which enable them to persist in a relatively stable environment with low energy availability. A comprehensive knowledge of the reproductive processes of the deep-sea fauna is essential in order to evaluate the level of variability caused in the environment principally by human activity and the possible effects on life-history of the species. 4
Page 1 and 2: University of Southampton Research
Page 3: Graduate School of the National Oce
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 and 14: species of asteroid Patiriella para
Page 15 and 16: embryonic tolerances could determin
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
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Fig. 3.7. Bippinaria larvae of Mart
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X Data were abnormal. At 150 and 20
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X Data all the embryos were abnorma
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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
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CHAPTER FOUR- REPRODUCTIVE FEATURES
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In 1973, Vance proposed a theoretic
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Species Volume Energy Dev Class Ref
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4.1.2- Body Size The reproductive o
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Species Depth of max. Depth range (
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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
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250 200 Body size (mm) 150 100 50 0
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Fig. 4.7. Hierarchical cluster anal
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(Hymenaster membranaceus Thomson).
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gamete production at low population
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varies depending on the vitellogeni
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size, high fecundity, small egg siz
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strategy described by Winemiller an
Page 104 and 105:
It seems that evolutionary features
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strategy stablished by the Winemill
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which normal embryonic/larval devel
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Larval dispersal from eight populat
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These results are very important si
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possibility. The opportunistic spec
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hypothesis that the Mesozoic and ea
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Barnes, H. and H.T. Powell. 1951. T
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Chester, C.M. 1996. The effect of a
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Crisp, D.J. 1978. Genetic consequen
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David, B., A. Guille, J-P. Féral a
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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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