Bianka Bommarito

Does egg size influence spawning temperature preference in substrate spawning cichlid fishes?

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ABSTRACT

Researchers have documented that fishes breed in many different places and times, however, fishes are known to be particular when choosing a spawning site and no theory has been developed to predict when and where a particular species should spawn. Egg size has been proposed to be a key component in this decision. Temperature is also likely important because it affects growth rates, the efficiency of utilizing food energy, and the amount of dissolved oxygen in water.

The purpose of my research is to determine how and why breeding fish chose a temperature at which to spawn. The Cichlidae is the third largest family of teleost fishes, and all members of the cichlid family exhibit some form of parental care. Substrate guarding is one of the most common forms of parental care, and because the eggs are adhesive, once they are laid, they will be committed to developing in that particular physical environment, i.e., water temperature, water velocity, etc; therefore spawning site choice is extremely important to the survival of the eggs and fry.

Because larger eggs need more oxygen than smaller eggs, due to a higher surface to volume ratio, I hypothesize d that when given a choice, a parent fish will chose its spawning temperature based on the oxygen needs of its size of egg, i.e., larger eggs will be laid in cooler water than smaller eggs. Egg size is typically fixed within a species, therefore all individuals within a species should make the same consistent spawning temperature choice. Prior to testing the main hypothesis, I tested an important assumption, namely that because of the importance of spawning temperature, choice of spawning temperature will not be influenced by prior exposure to different temperatures. In other words, fish will not be acclimated to spawn at a temperature different then their preferred spawning temperature, simply because they previously experienced warmer or cooler water.

To test these hypotheses, I will conduct ed two experiments using a temperature choice apparatus which allow ed s a pair of spawning fish to have four distinct temperatures at a time to choose from. I will use d substrate spawning cichlids because the location of the eggs, once laid, indicate d s the exact temperature at which the spawning took place. Temperature data loggers were placed in each compartment will therefore indicate the to record the temperature that was chosen.

In Experiment 1, I will conduct ed a set of trials to eliminate prior habitat temperature experience as a factor biasing future spawning temperature preference. To do this, I will use d eigh t p ten pairs of convict cichlids subjected to two different temperature treatments. F ive our of the pairs used w ere ill be housed in a tank set at 22ºC, and f ive our of the pairs used w er ill be housed in a tank set at 32ºC, for two weeks prior to being put into the spawning temperature choice apparatus to allow for acclimation to that particular temperature. I predict ed that these treatments w ould ill not affect future spawning temperature preference. The data w as i ll be analyzed using a t-test, and no significant difference was found between the preferred spawning temperatures of the two treatments . This means that prior temperature exposure does not effect future spawning temperature preferences. .

Experiment 2 will examine d the effect of egg size on spawning temperature preference and will consist ed of collecting spawnings from five other substrate spawning species, namely . I will collect at least eight spawnings each from five substrate spawning cichlid species; Archocentrus nigrofasciatus, Archocentrus spinosissimus, Microgeophagus altispinosa, Neetroplus nematopus, Hemichromis lifalili, T il apia snyderae, Steatocranus casuarius, and Herichthys cyanoguttatum Hypsophrys nicaraguense , . and do an interspecies comparison of egg size and average preferred spawning temperature (within a species). The six species used (including A. nigrofasciatus) encompass a large range of the egg sizes found in the cichlid family.

The results revealed that even with a spread of possible spawning temperature as great as 12.8°C, no species showed more than a 2.6°C variation from their particular mean preferred spawning temperature. This shows that each species tested had a consistent preferred spawning temperature. Comparing the average spawning temperature chosen by each species against one another, only T. snyderae against A. nigrofasciatus, and T. snyderae against H. lifalili showed a significant difference.

An interspecies comparison of egg size and average preferred spawning temperature within a species was also conducted, and a linear regression showed no relationship between chosen spawning temperature and egg size. This demonstrates that the cichlids tested do not base their spawning temperature choices on egg size.

 

Academic History

Associate of Arts degree, General Education- Monterey Peninsula College September 2000-July 2002

Bachelor of Science degree, Biology- California State University , Sacramento August 2002-May 2005

Master of Science degree, Biological Conservation- California State University , Sacramento August 2005-May 2011.

 

Research

 Bio 199 Independent Research in Coleman’s lab. “Growth Rate vs. Temperature of Convict Cichlid, Archocentrus nigrofasciatus, fry” 2003-2004

We know that fish grow at different rates depending upon temperature but the exact growth rates is unknown for most fishes. In this experiment I ran two experiments raising cichlid fry of Archocentrus nigrofasciatus (substrate spawners) and Geophagus steindachneri (mouth brooders) of one brood at four different temperatures. I measured a sample (5) fry from each temperature every four days and recorded growth rates and plotted them out on graphs. With each species the optimal growth rates were either found or surpassed even though the difference in temperature between the tanks were only 2°!

 

Bio 198A and 198B Undergraduate Honors Thesis in Coleman’s lab. “Temperature Preference of Reproducing Substrate Spawning Cichlids.” 2004-2005 although I am currently continuing to collect data.

It is known that larger eggs need more oxygen than smaller eggs due to a higher surface to volume ratio. The question is: “Do spawning fish recognize this difference in oxygen demand?” To solve this question, I designed and had built two temperature preference apparatus’. Each tank allowed for a choice of four different spawning temperatures to choose from. Pairs of fish were added, allowed to spawn, and the eggs and parents were removed. Eggs were measured and the sizes were plotted against spawning temperatures chosen and a curvelinear trend was found. Cichlids worked with were: Archocentrus nigrofasciatus, Archocentrus sajica, Microgeophagus altispinossa, and Archocentrus spinosissimus.

 

Photo by Bianka Bommarito. Temperature choice apparatus

 

Master’s Thesis in Coleman’s lab.

Does Egg Size Influence Spawning Temperature Preference in Substrate Spawning Cichlid Fishes?

Oral Presentations

 

American Society of Ichthyologists and Herpetologists Conference, Student Competition, Tampa , FL ( July 8, 2005 )
“Temperature Preference of Reproducing Substrate Spawning Cichlids"

CSU Student Research Competition, at CSU Sacramento , CA ( April 29, 2005 )
“Temperature Preference of Reproducing Substrate Spawning Neotropical Cichlids”

CSUS Student Research Competition, Sacramento , CA ( March 15, 2005 )
“Temperature Preference of Reproducing Substrate Spawning Neotropical Cichlids”

Cichlids I have worked with :

Archocentrus sajica

Archocentrus nigrofasciatus

 

Archocentrus spinosissimus

Microgeophagus altispinosa

Not pictured:

Cichlasoma amazonarum

Geophagus steindachneri

 

CSUS BIO SCI