Lec 13 Reproduction Flashcards
Eugene K. Balon
envisioned of ecological and ethological classification of reproductive systems.
The majority of fishes uses what kind of reproduction?
They’re oviparous, so the eggs are reproduced, laid and then fertilized.
Eggs come in two kinds
- Pelagic eggs that float
- demersal eggs that sink
Most marine fishes start out life as pelagic eggs
The marjority of marine fishes that start off as pelagic eggs includes
- most fishes that live over continental slope
- nearly all those that range over surface waters of the open ocean
- pelagic deep sea fishes.
How are pelagic eggs able to float?
made buoyant by low density fluids from folicle cells or they develop an oil droplet independent of ovacrian tissue.
What is the epipelagic zone?
upper sun lit layers of the ocean.
definition of nursery grounds
rish, upper, sun lit layers that are able to support the myraid of developing forms
What happens when the eggs hatch?
colorless larvae live off stored yolk, when its used up, they begin to feed on tiny phytoplankton and zooplankton
Fishes that produces floating eggs must also do what?
produce a large number of small eggs.
an example
mola mola 300 million
Why would high numbers of pelagic eggs be important?
Neccessary for successful recruitment cuz thousands of eggs and larvae and disperse to area beyond optimal conditions.
Has wide geographic distributions
Where are demersal eggs usually placed?
In nests, fastened to rocks, shells seaweed, sponges.
Where do the fishes that lay demersal live near?
They live in near shore waters.
Ex fishes blennies, gobies and other tidepool forms.
What’s the advantages of demersal eggs?
It sinks, so it’s more suited for tidepool environments. While floating eggs would be smashed up.
What kind of geographic distribution do demersal eggs have?
Restricted geographic distribution.
The eggs sink and are unlikely to be swept into unfavorable regions.
What are the size of demersal eggs?
Larger eggs, larger concentration of yolk. Later development. Fewer eggs
Are demersal or pelagic eggs more vulnerable to predation?
The demersal eggs since it is less likely to be swept away from tides. Usually they can be hidden by burying them in sand or under a rock. Some have parental care to guard the eggs.
Which egg is the rule for freshwater?
Demersal.
- Physiologically more difficult to produce an egg with a sp gravity < freshwater
- freshwater doesn’t provide rich food resource in upper layers compare to marine env
- fast movin rivers and streams would remove nearly all eggs and larvae from local population
Nearly all freshwater fishes deposit eggs that are sticky or scattered?
sticky and sink to bottom.
Others have many non adhesive eggs that scatter
What are some derived strategies to protecting eggs?
- bury or lay eggs in some kind of nest
2. hide and protect eggs in other organisms, i.e european bitterling deposits eggs inside freshwater mussels
What’s the difference between ovoviviparous and viviparous? How are they similar?
Similar: both are live bearing and require internal fertilization
Difference, ovovivivparous are eggs that are in the mom. Viviparous is when young is nourished by some placental connection with mother.
Example of ovovivipartiy and viviparity
It’s pretty rare among fishes.
i.e Chondrichthyes, live bearers, freshwater half beak, scorpioni fishes, surfperches, eel pouts
What is an intromittant organ?
Involved in internal fertilization.
Structure used to pass sperm to the female.
What is the best known case of ovoviviparity?
Eggs are fertilized within egg follicles of ovary and develop for sometime.
What is a simple kind of pseudoplacenta?
Wall of ovarian follicle acquire network of capillaries that extend out as villi and make intimate association with external surface of developing embryos.
What is the branchial placenta?
A more efficient pseudoplacental. Linging of ovary forms highly cascularized folds that makes contact with gills of developing ovaries.
What is the process of trophonema/trophotaenia.
food absorbing processes that grow out of the hind gut of the embryo
What is parental care?
when eggs are retained after being laid.
Forms of parental care, four kinds
- male parental care: sea catfishes, sticklebacks
- Female parental care: 3 types
- biparental care: bullheads
- juvenile helpers
3 types of female parental care
- oviparity with post spawning care
- ovoviviparity w/o post spawning care
- viviparity w/o post spawning care
explaing a type of male parental care
oral incubation.
the male keeps the eggs well oxygenated and protected from predation.
how do bunocephalid catfishes care for the young?
They lie down on the eggs after it’s been laid and fertilized. The eggs sink to underside and sticks there.
How does nurseryfishes care for the eggs?
Has bony hook on forehead, the hook is used to carry eggs which are in two bundles connected by a fibrous thread.
What kind of fishes tend to be hermaphrodites?
Deep sea fishes. There’s a definite trend toward an increase in the number of hermaphroditic species with depth.
Why do hermaphrodites occur at the depth they do?
increase scarcity of food with increasing depth causes reduction in population. So meeting between sexes are fewer.
What’s the difference between sex reversal and hermaphrodites?
Hermaphrodites has both reproductive organs. THe other has the ability to completely change its sex over.
When does sex reversal occur?
When no males are present. The females become male and act like one too.
What is protandry?
First half of the life cycle is spent in male state.
What is protogyny?
When they’re first females.
