1. 5 Reproduction, Dispersal, and Migration
Notes for Marine Biology: Function, Biodiversity, Ecology
By Jeffrey S. Levinton
©Jeffrey S. Levinton 2001

2. Sex and Reproduction IS SEX NECESSARY?
WE MUST SEPARATE SEX AND REPRODUCTION?
SPECIES CAN REPRODUCE WITHOUT SEX (CLONAL GROWTH INVOLVING FISSION OR BUDDING OF INDIVIDUALS)

3. Sex and Reproduction Non-sexual reproduction:
Descendants are genetically identical - clone
Colonial species produce a set of individuals that are genetically identical, known as a module; each module may have arisen from a sexually formed zygote

4. Cost of Sex FEMALE gives up half her possible genes in progeny
Sex involves expenditure of energy and time to find mates, combat among males

5. Benefits of Sex?
genetic diversity - sex increases combinations of genes - resistance against disease
Alternative to sex: clones, must wait for mutations to occur
Sex - recombination produces variable gene combinations, meiosis enhances crossing over of chromosomes: new gene combinations and intragenic variants

6. Sexual Selection
selection for extreme forms that breed more successfully - major claw of fiddler crabs, deer antlers, colors of male birds
Can involve selection for display coloration, enhanced combat structures
Female choice often involved; selection for fit males (good genes hypothesis)

7. Sexual Selection The major claw of fiddler crabs is employed
for display to attract females and for combat
with other males

8. Types of Sexuality Separate sexes -gonochoristic
Hermaphroditism -individual can have male or female function

9. Hermaphroditism Simultaneous Sequential
Protandrous - first male,then female
Protogynous - first female then male

10. Sequential Hermaphroditism
Protandry - size advantage model
Eggs costly in terms of resources, so more offspring produced when individual functions as female when large
Male function does not produce great increases in offspring when it gets larger
Therefore, there is a threshold size when female function begets more offspring.Smaller individuals do better as males.

11. Male at advantage Female at advantage
Number of offspring produced
Male
Body size
The size advantage model for Protrandry

12. Protogyny
Male function must result in more offspring when male is older and larger
Important when aggression is important in mating success, e.g., some fishes where males fight to maintain group of female mates

13. Male polymorphism
Males may occur as aggressive fighting morphs, or less aggressive morphs
Found in a number of groups, e.g., some fishes and some amphipod or isopod crustaceans
Determination of morphs can be environmental, genetic
Less aggressive morphs can obtain mates by “sneaky” tactics, which are often successful

14. Factors in Reproductive Success
Percent investment in reproduction - reproductive effort
Age of first reproduction (generation time)
Predictability of reproductive success
Juvenile versus adult mortality rate

15. Life History Theory Tactics that maximize population growth
Evolutionary “tactics”:Variation in reproductive effort, age of reproduction, whether to reproduce more than once
Presume that earlier investment in reproduction reduces resources available to invest in later growth and survival

16. Examples of Life History Tactics
Strong variability in success of reproduction:reproduce more than once
High adult mortality: earlier age of first reproduction,perhaps reproduce only once
Low adult mortality: later age of first reproduction, reproduce more than once

17. Example: Selection in a Fishery
Shrimp Pandalus jordani,protandrous
Danish, Swedish catch (Skagerak)
– stable, increased slowly
– catch tripled (2000  6300 ton/y)

18. Pandalus jordani fishery
Changes in Body Size
Changes in Size of Change from Male to Female

19. Sex - factors in fertilization
Planktonic sperm: (and eggs in many cases). Problem of timing, specificity.
Direct sperm transfer: (spermatophores, copulation). Problem of finding mates (e.g., barnacles, timing of reproductive cycle)

20. Planktonic sperm and eggs
Specialized binding/fertilization proteins in sperm and receptors in eggs (bindin in sea urchin sperm, lysin in abalone sperm)
Sperm attractors in eggs
Binding proteins are species-specific, proteins with high rates of evolution

21. Gamete matching important in plankton

22. Timing of sperm and egg release
Epidemic spawning - known in mussels, stimulus of one spawner causes other individuals to shed gametes
Mass spawning - known in coral species, many species spawn on single nights
Timing of spawning (also production of spores by seaweeds) at times of quiet water (slack high or low tide) to maximize fertilization rates

23. Movement of Marine Organisms

24. Dispersal versus migration
DISPERSAL: UNDIRECTED
MIGRATION: DIRECTED, RETURN SPECIFIC

25. Migration scheme Adult Stock Spawning Area Nursery/Juvenile
Feeding Area

26. Migration Types
ANADROMOUS - fish live as adults in salt water, spawn in fresh water (shad, striped bass), more common in higher latitudes
CATADROMOUS - fish live as adults in fresh water, spawn in salt water (eel) more common in lower latitudes
FULLY OCEANIC - herring, green turtle

27. Migration

28. Norway
Migration of
the herring
in the North
Sea
Adult
feeding
area
Spawning
areas

29. N. America
Europe
Africa

30. Larval Dispersal

31. Dispersal Types in Benthic Species
PLANKTOTROPHIC DISPERSAL - female produces many ( ) small eggs, larvae feed on plankton, long dispersal time (weeks), some are very long distance (teleplanic) larvae - cross oceans
LECITHOTROPHIC LARVAE - female produces fewer eggs ( ), larger, larvae live on yolk, short dispersal time (hrs-days usually)
DIRECT RELEASE - female lays eggs, or broods young, juveniles released and crawl away

32. Lecithotrophic larva: tadpole larva of the
colonial ascidian Botryllus schlosseri
Pluteus larva of an urchin
Planktotrophic larva of
snail Cymatium parthenopetum

33. Loss to offshore waters
Wind-driven
recruitment
onshore
Internal waves,
tidal bores
Self-seeding
eddies
Longshore drift
Shore Population

34. Some helping hands in dispersal
Winds that wash larvae to shore
Internal waves - bring material and larvae to shore
Eddies that concentrate larvae in spots
Behavior - in estuaries can allow retention (rise on the flood tide, descend on the ebb tide)

35. Estuarine larval adaptations - retention
Larvae rise on the flooding tide, sink to bottom on the
ebbing tide: results in retention of larvae within estuary

36. Estuarine larval adaptations - movement of larvae to coastal waters, return of later stage larvae
Blue crab, Callinectes sapidus

37. Effect of local eddies on larval retention in a patch reef on the Great Barrier Reef, Australia
Planula
larva
Recruitment of juvenile corals
Distance from reef perimeter
Newly settled coral

38. Why disperse?
High probability of local extinction; best to export juveniles
Spread your young (siblings) over a variety of habitats; evens out the probability of mortality
Maybe it has nothing to do with dispersal at all; just a feeding ground in the plankton for larvae

39. Settling problems of planktonic larvae
Presettling problems:
Starvation
Predation in plankton
Loss to inappropriate habitats

40. Example of Effect of Starvation:
Phytoplankton variation and barnacle larval success
Abundant diatoms
1950
Normal
phytoplankton
1000
500
Cyprids
settling
Early
Larval
stages
Later
Larval
Stages
Number of larvae
1951
Failure of
phytoplankton
Diatom
failure
March April
Semibalanus balanoides settlement in a Scottish Sea Loch

41. Postsettling problems
Energetic cost of metamorphosis
Predation
Crowding --> mortality
Initial
6 months
12 months
Expectation of life
(months)
18 months 2
Interindividual contacts per cm
Expectation of life of Semibalanus balanoides as function of crowding

42. Stages in the selection of substratum by planktonic larvae
Free-swimming larva
Selection
Behavior
Alternating
Photo+ and
Photo- stages
Block in
behavior,
contact with
inappropriate
surface
Releasor
Random contact
With a
surface
Selection behavior-
crawling and test
surfaces
Releasor
Releasor
Releasor
Block in
behavior,
e.g., contact with
crowded surfaces
Contact w.
Substance on
Sfc. Of another
species
Contact w.
pits and
grooves
Contact w.
adults of
same sp.
Selection behavior-
frequent turning
and flexing
ATTACHMENT
Stages in the selection of substratum by planktonic larvae

43. The End