Egg size determines fry size in substrate-spawning cichlid fishes.

1. EGG SIZE
DETERMINES FRY
SIZE IN SUBSTRATE-
SPAWNING CICHLID
FISHES
Faculty Advisor: Ronald M. Coleman, PhD
Dept. Of Biological Sciences
California State University, Sacramento
Hailey Donaldson

2. Special Thanks
Delisle Fund of the Department of Biological
Sciences
Campus Grant Award from UEI (CSUS)
IRA Grant from CSUS

3. Individuals Involved in this Project:

4. Egg Production and size
Something to consider when attempting to understand egg production, is
the energetic cost that it requires.
Egg poduction is highly
energetically costly, yet egg size
varies enormously.
Why does this variation in egg size
occur?

5. Cichlid Fishes
The reason we are studying fish from
the family, cichlidae, is because it is
an extremely diverse family.
1,700spp. (Nelson et al. 2016)
Egg size varies from 1mm > to 5mm
in diameter.
They are also very easy to care for
and spawn.

6. Within Species Variation in Egg Size
Egg size varies little within
a clutch (Coleman 1991).
Egg size is relatively fixed
within a species.

7. Across Species Variation in Egg Size
Egg size is independent of
female body size (Coleman
1991).
Regardless of the size of
the parents, fish of different
species lay eggs of
different sizes.
(1) Lionhead
Cichlid
(2) Jewel Cichlid

8. Hypothesis
Fry size is directly proportional to egg size in substrate-
spawning cichlids.
Egg size is a measure of parental investment.
Fry size is a measure of survivability.
Prediction:
Large eggs will become large fry.
Small eggs will become small fry.

9. Methods and Materials
We have bred 50 species of
cichlids across 23 genera so far.
Tanks are checked daily for
eggs or fry.
Behaviors are monitored.
Air Filter
Spawning Surfaces
Artificial
Plants
Heater

10. Egg and Fry Collection
Eggs are collected from the
substrate:
20-30 eggs are preserved in 70%
isopropyl alcohol.
Once Offspring is free-swimming:
20-30 fry are collected and preserved in
5% formalin.

11. Measuring Eggs and Fry
Using a disecting microscope with an ocular
micrometer:
Effective egg diameter (Copeia 1991) is measured
across Major (A) and Minor (B) Axes.
Diameter if reshaped into a perfect sphere.
Fry are measured for their total length.

12. Results
Click to add text
Regression analysis
of mean total fry
length (TL) as a
function of mean
effective egg diameter
of 50 species of
substrate-spawning
cichlids. (R = 0.93, df
= 49,
P < 0.001)
2

13. Results
Significant positive relationship between
fry length and effective egg diameter.
Range of Sizes:
Smallest: Mikrogeophagus ramirezi
Eggs (0.92mm); Fry (3.8mm)
Largest: Steatocranus casuarius &
Steatocranus tinanti
Eggs (2.8mm); Fry (9.2mm)

14. Discussion
Egg size plays a critical role in determining fry size for substrate-
spawning cichlids.

15. Discussion: Costs and Benefits of Egg Size
Female cichlids face a tradeoff:
Small fry: decreased swimming ability, fewer food options, and
more susceptible to predation.
Large fry: increased swimming ability, more food options, and less
susceptible to predation.
If It is more advantageous to lay large eggs, then why do some females
still lay small eggs?

16. Future Work
We will quantify the benefits of laying
small eggs by quantifying the fecundity
(number of eggs laid).
Hypothesis: The disadvantages of
laying small eggs are outweighed by
the greater number of potentially
surviving offspring.
Smaller
Eggs
Larger Eggs