Lec 17 Eggs and Larvae Flashcards
what does ontogeny mean?
development
Fish eggs and larvae are considered part of the plankton, meaning
they cannot swim against currents
although some larval fishes have been shown to swim vertically in the water to take advantage of dif currents
What do larval fishes eat?
phytoplanton, algae, copepods, larvaceans, and other fish
How do eggs/larvae differ from adults? Name 4
- anatomically
- physiologically
- behaviorally
- ecologically
Why is it important to know the early life history of fishes?
To have proper management of fisheries. Even of non commercial fishes because they belong in the same ecosystem with commercial fishes
How is the sampling of fish eggs and larvae helpfully?
Provides info about fish species, populations and communities.
Can determine yearly fish population.
Can be used to determine geographic distribution of spawning adults
What are vertical egg tows?
A net that is used to collect eggs, it’s lowered to 70 m and retrieved at a constant rate
What is a neston tow
method to collect larvae by sampling just the upper 10 cm of water.
Afterwards, they’re washed by formalin to preserve the eggs.
What is extrusion?
Loss of organisms after capture
How may collectors limit the amount of extrusion occuring?
By considering the mesh size and speed of the two
How is avoidance of sampling gear possible by larvae?
Larvae may avoid collection by their size and speed to travel away from the negs, and the size and speed of the net being used to collect them
Describe the early development stage of fish eggs
fertilization to blastopore closure
Describe the middle development stage of fish eggs
blastopore closure to embryo tail bud free of yolk
Describe the late development stage of fish eggs
embryo tail bud free of yolk to hatching
What occurs during the pre flexion development of the larvae?
absorption of yolk sac to start of notochord flexion
What occurs during the flexion development of larvae?
start of notochord flexion to completion of notochord flexion
What occurs during the post flexion of the development of larvae?
completion of notochord flexion to start of metamorphosis
What are characteristics used to describe fish eggs? (6)
- Shape
- Size
- Chorion texture
- Size and shape of oil globules
- Perivitelline space
- Embryonic charac (late stage only)
What is the chorion texture?
embryonic tissue layer
What are five catergories used to identify fish larvae?
- morphology: length and shape of gut
- Meristics (things you can count on fin spines and rays, myomeres
- Specialized larval charac: elaborated spines on the head, stalked eyes, trailing guts, enlarged fin folds
- osteology: timing of bone and cartilage development
- Genetics: DNA of unknown larvae matched to DNA of known adults
Define meristics
things you may count
what is myomeres?
muscle bands that run along the length of the fish
What are two main approaches to identifying unknown eggs and larvae?
- serial method
2. aquaculture methods
What is the serial method?
This method uses adult charac to identify juveniles and progressively link them to smaller specimens through a continuous sequence of shared/ similar traist
What is the aquaculture method?
Raise colected specimens of unknown eggs/larvae till they can be identified, or to spawn adults of a species for which the eggs/larvae are unknown and raise the offspring.
Another third method to identify fishes is through DNA testing, but why may it be bad?
Can be expensive, difficult to do and ruin the fish.
How may ontogeny be used to determine phylogenetic relationships?
the characteristics used to identify larvae can potentially be used to construct phylogenetic trees
An example is the leptocephalus larvae of the anguilliformes orders
How is avoidance of sampling gear possible by larvae?
Larvae may avoid collection by their size and speed to travel away from the negs, and the size and speed of the net being used to collect them
Describe the early development stage of fish eggs
fertilization to blastopore closure
Describe the middle development stage of fish eggs
blastopore closure to embryo tail bud free of yolk
Describe the late development stage of fish eggs
embryo tail bud free of yolk to hatching
What occurs during the pre flexion development of the larvae?
absorption of yolk sac to start of notochord flexion
What occurs during the flexion development of larvae?
start of notochord flexion to completion of notochord flexion
What occurs during the post flexion of the development of larvae?
completion of notochord flexion to start of metamorphosis
What are characteristics used to describe fish eggs? (6)
- Shape
- Size
- Chorion texture
- Size and shape of oil globules
- Perivitelline space
- Embryonic charac (late stage only)
What is the chorion texture?
embryonic tissue layer
What are five catergories used to identify fish larvae?
- morphology: length and shape of gut
- Meristics (things you can count on fin spines and rays, myomeres
- Specialized larval charac: elaborated spines on the head, stalked eyes, trailing guts, enlarged fin folds
- osteology: timing of bone and cartilage development
- Genetics: DNA of unknown larvae matched to DNA of known adults
Define meristics
things you may count
what is myomeres?
muscle bands that run along the length of the fish
What is the serial method?
This method uses adult charac to identify juveniles and progressively link them to smaller specimens through a continuous sequence of shared/ similar traist
What is the aquaculture method?
Raise colected specimens of unknown eggs/larvae till they can be identified, or to spawn adults of a species for which the eggs/larvae are unknown and raise the offspring.
Another third method to identify fishes is through DNA testing, but why may it be bad?
Can be expensive, difficult to do and ruin the fish.
How may ontogeny be used to determine phylogenetic relationships?
the characteristics used to identify larvae can potentially be used to construct phylogenetic trees
An example is the leptocephalus larvae of the anguilliformes orders
The family Myctophidae is divided in two tribes, How may they be distinguished?
By shape of eye. One has round eyes, other has narrow elliptical eyes.
What is the layman term for myctophidae?
lanternfishes
The superfamily of argentinoidea is composed of four families, but do not look similar. What are the ontogenetic characteristics that define this group then?
- The chorion has distinctive pustules on the inner surface
- dorsal and anal fins form in the fin fold away from the body, connected to the trunk by what are called hyaline strands
Although a good way to recognize common descents of argentinoidea, it is also an ex of convergent evolution
