Supported by the Pacific Coast Cichlid Association, the American Cichlid Association, the Apistogramma Study Group, the San Francisco Aquarium Society and the Minnesota Aquarium Society

Overview

The Cichlid Egg Project is an attempt to catalog the diversity of egg sizes found in the family Cichlidae by collecting eggs from as many species as possible and measuring them in a common way. The project continues to be greatly aided by donations of fish eggs from cichlid aquarists.

Introduction

Three things stand out to make cichlids such a fascinating group for both aquarists and scientists: they can be kept and bred in aquaria; they are incredibly diverse; and they provide some of the finest displays of parental care.

In my research, I am particularly interested in understanding the diversity of parental care seen in this family. There is variation in which parent provides care, the form of care (mouthbrooding, guarding) and even the amount that a parent is willing to invest. At the root of this diversity are the eggs.

The eggs are one reflection of how much a female is willing to put into each offspring. If you've spawned more than one species of cichlid, you may have noticed that not all fish eggs are the same.

Egg size in fish is the result of a spectrum of selection pressures operating on parents laying and caring for eggs, the eggs, and the resulting fry. The parent, for example, faces a tradeoff between egg size and egg number (the more eggs you make, the smaller each must be). The size of the egg influences the time it takes to hatch, an important consideration for an egg in risk of predation or falling water levels. Because the parents are committed to parental care at least until the eggs hatch, the longer the eggs take to develop, the greater the cost of parental care in terms of time and energy. Finally, the size of an egg might determine the size, health and capabilities of the fry that emerges from it.

To understand these factors, we need a good understanding of the variation present in cichlid eggs. In practical terms, I need to determine the egg size for as many species of cichlids as possible.

The hardest problem in doing this research is spawning the fish. A single researcher would take a lifetime to spawn even a modest number of species. However, cichlid aquarists spawn dozens of species all the time. Cumulatively, there are several hundred species of cichlids, including many very rare and even endangered species, that are spawned on a regular basis by cichlid aquarists. Cichlid aquarists can provide a valuable service to science by helping out with the cichlid egg project!

How you can help

I have come up with a simple, standardized way of measuring and preserving cichlid eggs so that the data from each sample is comparable to another. What I need are samples of cichlid eggs. Currently I have data from 230 species, but there are still many entire groups of cichlids for which I have no data at all. Also, even for species for which I have a sample, additional samples are extremely helpful to determine the extent of variation within a species. So, in essence, I can use egg samples from absolutely ANY cichlid species you might spawn (the one exception being convict cichlids -- I have over 170 different spawnings of these from my own work!).

How to donate eggs

To help out, all you need are three things. The first is the fish! The second is a little jar or vial which I would be happy to send you. The third is a little bit of 70% isopropyl alcohol, often called rubbing alcohol. This is inexpensive and available pretty much everywhere in the world at drugstores or grocery stores. Since you'll need only a few drops for a batch of eggs, a small bottle of rubbing alcohol will last a life-time.

After your fish breed, the next step is to get a sample of eggs away from the parents. Twenty eggs from any given spawn would be ideal, but even 1 egg is great if that's all you can get, particularly for the larger mouthbrooders. These can be taken any time after laying and before hatching.

For substrate brooders, the eggs are attached to the substrate by invisible threads. Scrape the eggs off with a fine, dull implement such as a butter knife. Fish eggs are kind of rubbery and they survive being scraped off just fine. Avoid using a sharp knife or a razor blade because that may slice into the actual egg. Incidentally, if the eggs are laid on a flowerpot or other removeable object, you can take the pot right out of the water, scrape the eggs off the pot and put the pot with the rest of the eggs back in the aquarium. The remaining eggs will hatch as if nothing had happened -- I do this all the time and you can keep cichlid eggs out of the water for at least 3 or 4 minutes. Fish truly are amazing!

There are different techniques for stripping mouthbrooders. One way is to hold the fish in a net, mouth down and dribble a little water along its side into its gills. The fish will often cough up the eggs into the net.

Once you have the eggs, put them in the vial, and add enough rubbing alcohol to completely cover them. The alcohol kills the eggs instantly but also preserves them so they don't change size. Most importantly, seal the vial tightly. Please write on the vial which species the eggs are, your name and the date. You can mail the vial to me or arrange for me to get it if you live near the Bay Area of San Francisco.

Mailing address: Ron Coleman, Department of Biological Sciences, 6000 J Street, California State University, Sacramento, Sacramento, CA 95819-6077

Phone: 916-278-5836
Email: rcoleman@cichlidresearch.com