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Biodiversity of Fishes Sex under Water Rainer Froese IFM-GEOMAR 18.12.08.

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Presentation on theme: "Biodiversity of Fishes Sex under Water Rainer Froese IFM-GEOMAR 18.12.08."— Presentation transcript:

1 Biodiversity of Fishes Sex under Water Rainer Froese IFM-GEOMAR

2 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

3 Copyright restrictions may apply. Powell, M. L. et al. Integr. Comp. Biol : ; doi: /icb/

4 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 –Males have no penetrating organ –Eggs found in females were not fertilized

5 Vertebrate Sex through the Ages Lampreys (450 Million Years) Genital papilla in males

6 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)

7 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

8 Vertebrate Sex through the Ages Chimaeras (400 Million years) Finally: the advent of the male intromittent organ and the separate urogenital opening Females lay few, large (~10 cm), horny eggs

9 Vertebrate Sex through the Ages Sharks 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

10 Video startstart

11 Vertebrate Sex through the Ages Ray-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)Rhodeus armarus –Outside of the water (Leuresthes tenuis)Leuresthes tenuis –Sex change (protogyny, protandry, simultaneous) –Self-fertilization (Rivulus marmoratus)Rivulus marmoratus –Millions of small eggs

12 Indigo Hamlets

13 Mandarin fish Video:

14 Sockeye salmon

15 Betta imbellis

16 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)


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