Gerlach, G., & Lysiak, N. (2006). Kin recognition and inbreeding avoidance in zebrafish, Danio rerio, is based on phenotype matching. Animal Behaviour, 71: 1371-1377.

Gerlach & Lysiak investigated the type of kin recognition mechanism used by zebrafish in this paper. Kin recognition may be an important method of increasing inclusive fitness used by many species. In this investigation, the authors chose to work with zebrafish for multiple reasons: 1) they are easily bred in captivity, 2) it is possible to control the environment of developing eggs and larvae, and 3) the zebrafish genome has been completely sequenced. Although zebrafish are a common study specimen, little is known about their natural behavior, including their use of chemical cues.

To raise unfamiliar kin, the authors separated egg batches from the same parents in different tanks. To conduct odor choice tests, a flume was used so that it was possible to present two odors simultaneously, each in their own distinct parallel water column. A test fish was placed into the flume and was allowed to travel freely between odors. The authors recorded the fish’s preference for each odor by observing how much time it spent in each odor. Tests were conducted with juveniles, adult females, and adult males and with odors of unfamiliar kin, familiar kin, unrelated individuals, plain water and odors of other species (cichlids).

These tests revealed that juvenile zebrafish preferred conspecific odor to plain water or odor of another species, as well as familiar kin over unfamiliar kin. Adult females preferred the odor of nonkin males, and adult males showed no preference for nonkin or kin females. These results suggest that the mechanism of kin recognition in zebrafish is phenotype matching; juvenile zebrafish could recognize kin without any prior experience with any kin. However, juveniles also showed a preference for familiar kin over unfamiliar kin, suggesting that familiarity may also play a role in kin recognition.

Our lecture on social integration is most relevant to this paper. In class we discussed the four different mechanisms for recognition: 1) spatial location in which the probability of encountering a specific individual in a particular location is very high, 2) familiarity, in which recognition requires learning of an individual’s specific characteristics, 3) phenotype matching, in which genetic similarity is identified, often without any prior experience with kin, and 4) allele matching, which is a single hypervariable locus with many rare alleles is used to identify close kin through chemical recognition.

In this paper, the authors’ goal was to discriminate between the familiarity and phenotype matching methods of recognition in zebrafish. In lecture we learned that in order to test phenotype matching, it is important to be able to somehow separate kin early enough that familiarity does not occur. Separating egg batches from same parents allowed the authors to accomplish this isolation of siblings. It was previously shown that juvenile zebrafish can differentiate between familiar and unfamiliar nonkin independent of spatial location, so kin recognition through spatial location was ruled out. Results of the paper demonstrated that zebrafish probably use both phenotype matching and familiarity to identify kin. Phenotype matching is useful because it is relatively difficult to subvert and provides a method of kin recognition which does not require learning.