Biodiversity of Fishes Sex under Water Rainer Froese IFM-GEOMAR 18.12.08.
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Transcript of Biodiversity of Fishes Sex under Water Rainer Froese IFM-GEOMAR 18.12.08.
![Page 1: Biodiversity of Fishes Sex under Water Rainer Froese IFM-GEOMAR 18.12.08.](https://reader035.fdocuments.net/reader035/viewer/2022081518/551a64cb550346545e8b5c80/html5/thumbnails/1.jpg)
Biodiversity of FishesSex under Water
Rainer Froese
IFM-GEOMAR
18.12.08
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The Mechanics of Sex under Water
• Eggs have to be fertilized (or activated) by the right sperms
• Eggs are few and large (< 10 cm) or numerous and small (< 1 mm), internal, attached or drifting
• Sperms are very small, very numerous, mobile, outside
• Survival of gametes in water is short (few minutes)
• Courtship and mating aims to increase fertilization rate
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Powell, M. L. et al. Integr. Comp. Biol. 2005 45:158-165; doi:10.1093/icb/45.1.158
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Vertebrate Sex through the Ages• Hagfish: keeping a secret for 600 million years
– Eggs are large (~ 4 cm) with horny shell, produced in batches of 20-30
– Males have no penetrating organ– Eggs found in females were not fertilized
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Vertebrate Sex through the Ages Lampreys (450 Million Years)
Genital papilla in males
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Vertebrate Sex through the Ages Lungfishes (400 Million Years)
• External fertilization of large eggs• Males guard eggs in burrow (Protopterus, Lepidosiren) • Eggs are deposited among plants (Neoceratodus)
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Vertebrate Sex through the Ages Coelacanths (400 Million years)
• Another secret: internal fertilization without special male organ
• Young hatch from large eggs within the female, older embryos feed on unfertilized eggs, gestation takes 3 years
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Vertebrate Sex through the AgesChimaeras (400 Million years)
• Finally: the advent of the male intromittent organ and the separate urogenital opening
• Females lay few, large (~10 cm), horny eggs
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Vertebrate Sex through the AgesSharks and Rays (200 Million Years)
• Internal fertilization with claspers, but separate urogenital opening lost
• Few large young• From egg-laying (oviparity) to hatching after birth, to
hatching within the mother (viviparity), to a placenta-like arrangement
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Vertebrate Sex through the AgesRay-finned Fishes (150 Million Years)
• Separation of anus and urogenital opening• Wide variation in strategies for fertilization and
development of eggs and larvae• New strategies include:
– In-mouth fertilization and brooding (cichlids, Apogon)– In other animal (bivalve, Rhodeus armarus,
ovipositor) – Outside of the water (Leuresthes tenuis)– Sex change (protogyny, protandry, simultaneous)– Self-fertilization (Rivulus marmoratus)– Millions of small eggs
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Indigo Hamlets
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Mandarin fish
Video: http://www.youtube.com/watch?v=Tar9so2Jvfw
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Sockeye salmon
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Betta imbellis
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Exercises
• In FishBase, select a species of your choice and discuss its reproductive strategy with respect to phylogeny and environment (check for online photos or video)