- Open Access
The effects of various temperature-salinity combinations on the body form of newly hatchedCyprinodon macularius (Teleostei)
© Biologischen Anstalt Helgoland 1964
1. Spawning groups of the teleostCyprinodon macularius kept at 28° C in air-saturated water of 35 ‰ salinity were allowed to spawn at intervals of 3 to 4 days. Their eggs were transferred 4 hours after fertilization into a variety of temperature-salinity combinations and the newly hatched young fixed within 60 minutes. The body form of these young was then examined by measuring 13 different length, depth and width dimensions.
2. All 13 dimensions vary as a function of the temperature and salinity conditions effective during incubation. The dimension versus temperature plot results in differently shaped curves in the three test salinities.
3. In fresh water, body length decreases above and below 32° to 33° C, while the various depth and width measurements increase. Maximum total length values are therefore correlated with minimum depth and width values; the body tends to become deeper and wider in the lowest and highest temperatures tested.
4. In 35 ‰ body length decreases progressively with increasing temperature, especially near the upper critical temperature (34°, 35° C). All depth and width dimensions measured tend to decrease more or less harmoniously; hence there is little change in body form (isometry).
5. In 70 ‰ body length decreases rapidly from 26° to 28° C but changes little in the next higher temperature level (31° C). All depth and width dimensions measured tend to change proportionally (often not quite as harmoniously as in 35 ‰).
6. It seems possible that the increasing degree of disharmony in the order 35 ‰ < 70 ‰ < fresh water is related to the fact that(a) all eggs tested were laid and fertilized in 35 ‰ and remained there for 4 hours before being transferred into the test salinities and(b) 35 ‰ affords near optimum conditions for growth and reproduction. It seems possible that the structural consequences of exposure to the different incubation media may be different if spawning took place in fresh water or 70 ‰ instead of in 35 ‰.
7. Body depth and width tend to increase with decreasing salinity, resulting in rounder fish in fresh water with less surface area per unit volume.
8. Body dimensions (length as well as depth and width) are significantly smaller in 70 ‰ than in fresh water or 35 ‰.
9. Changes in body dimensions of hatching fry may be related to the concomittant changes in the amounts of dissolved gases, especially O2, in the various temperature and salinity combinations employed.
10. Environmental effects during very early ontogeny are of paramount importance for the functional and structural properties of the individual and may modify its ecological capacities.
- Body Length
- Body Form
- Body Dimension
- Width Dimension
- Test Salinity