Does the size of a predator influence the willingness of a parent cichlid to defend its offspring? Esther Tracy Supervisor : Dr. Ron Coleman Department of Biological Sciences California State University, Sacramento Abstract The extent of parental investment is partly based on maximizing lifetime reproductive success. When confronted with a predator, a female cichlid must make a choice to protect her current offspring or to call it a loss and survive until her next chance at reproduction. In this study, I tested the aggressive behavior of a female convict cichlid (Archocentrus nigrofasciatus) toward models of a predator of two different sizes to determine if the predator size affects her willingness to defend her offspring. Background Convict cichlids (Archocentrus nigrofasciatus) show significant parental investment by protecting their offspring. Convict cichlids have been shown to change their aggressive response due to temperature, prior residence, conspecific density, risk of predation, and even time elapsed since last mating (Fitzgerald and Keenleyside, 1978; Cole et al., 1980; Ratnasabapathi et al., 1992; Wisenden and Sargent, 1997; Kim et al., 2004). The extent and kind of care-giving a cichlid gives may interfere with future mating opportunities (Kuwamura, 1986). Because the goal of any animal is to maximize its lifetime reproductive success, the female convict has to make a decision whether to continue attacking a predator or abandon her offspring and have an opportunity for future reproduction. In nature, predators come in all different sizes, the larger the predator the greater the threat to the wrigglers and to the cichlid providing the care. Hypothesis I hypothesize that a female convict cichlid will increase her attacks on a larger model versus a smaller model in order to protect her offspring. Methods Each pair of convict cichlids was placed in a 76 liter tank with two terra cotta pots and two plastic plants to provide shelter. Tanks were filtered using a sponge filter and heated using a 150 watt heater set to 27 degree Celsius. The bottom was covered with medium sized gravel. A pair of cichlids was placed in these tanks until the eggs were laid, at which point the male was removed from the tank so the female was the only one providing the parental care. Various sized female convict cichlids were used in order to test if parental size affected the aggressiveness of the female. To test parental investment in convict cichlids, female convict cichlids were presented with two different sized models of Amphilophus hogaboomoruma, a species of cichlid found naturally with convict cichlids. The small model measured 5.5 cm while the large model measured 7.2 cm in length. The model predator was placed in front of the three day old hatchlings, and moved in a figure eight pattern in rhythm to a metronome set at 80 beats per minute. Aggressive behavior was measured using a clicker counter recording the number of bites that the female delivered onto the models for a 30 second period. Each female was observed for 10 days after the eggs had hatched. Preliminary Results Preliminary data shows a bell shaped curve pattern in the number of bites a female delivers during the development of her offspring. The highest peak in aggressiveness from the female comes at about day five or six. The days prior and after the peak taper off. A one-tailed paired t-test on the data points collected so far show a p-value of with the degrees of freedom being 3 This does not show that there is a significant statistical difference between the attacks on a large versus small predator model. Figure 3 Presenting a female cichlid with a model of the predator Figure 2 Experimental tank set up Figure 1 Different sized models of Amphilophus hogaboomorum representing the predators 6 We thank the Summer Undergraduate Research Experience Award of the College of Natural Sciences and the Department of Biological Science, CSUS, for support. Fig 4. The number of bites delivered by the female convict cichlids on the small versus large models Discussion With a p-value> 0.05, preliminary statistical analysis shows that there is no statistical difference in the number of bites exerted onto a certain sized model. This suggests that female convict cichlids don’t assess one of the models as more of a threat than the other. It has been hard to gather data because four of the females have spawned but have not attacked the models. One reason could be that the models are not realistic enough and the fish don’t feel threatened. The difference between the two models could not be large enough to merit more aggressive behaviors. Another reason could be that the females have not spawned previously and still are trying to figure out how to be mothers, or it could be due to the fact that the females have bred before and feel like their reproductive success is sufficient.