Pair-bonding influences affective state in a monogamous fish species

Abstract

In humans, affective states are a key component in pair-bonding, particularly in the early stage of a relationship. Pairing with a high-quality partner elicits positive affective states which, in turn, validate and reinforce the mate choice. Affective states thus strongly affect pair stability and future reproductive success. We propose generalizing the link between affective states and pair-bonding to encompass other monogamous species exhibiting biparental care, chiefly where the reproductive success of the pair critically depends on the coordination between partners. The convict cichlid Amatitlania siquia is a monogamous fish species that forms long-lasting pairs with strong cooperation between parents for parental care. In this species, we showed that females paired with their non-preferred male had lower reproductive success than those paired with their preferred male. We then transposed the judgement bias paradigm, previously used in other animal species, to assess objectively affective states in fishes. Females that were assigned their non-preferred partner exhibited pessimistic bias, which indicates a negative affective state. By contrast, females that were assigned their preferred partner did not exhibit changes in their affective state. Our results highlight that the influence of pair-bonding on affective states is not human-specific and can also be observed in non-human species.

Keywords: convict cichlid Amatitlania siquia; emotion; judgement bias test; mate choice; optimistic–pessimistic bias; partner attachment.

Figure 1.

(a) The same set-up was used for experiments 1 and 2. The box in the front of the tank was only introduced in experiment 2. (b,c) Experiment 2: the female in the focal compartment was trained to remove the lid of a cylindrical box located in the front of her compartment, 2 cm from the glass. Each fish succeeded in performing this task either by pulling (b) or pushing (c) the lid (see example in the electronic supplementary material, video S1). The female was first trained to discriminate between sequentially presented positive (rewarded) and negative (unrewarded) signals based on a combination of randomly allocated spatial (left or right side of the compartment) and visual (black or white lid) cues. The judgement bias test evaluated her response to an ambiguous signal (intermediate position and colour).

Figure 2.

Evaluation of females' affective state based on the judgement bias paradigm (experiment 2). The latencies to the opening of the boxes associated with the positive, ambiguous and negative signals were measured repeatedly in three contexts: before mate choice, during mate choice and with one assigned male. Females were randomly divided into two treatment groups; they were assigned their preferred (a) or non-preferred (b) male (n = 17 and n = 18, respectively). The error bars denote the standard error. Asterisks indicate significant differences (p < 0.01) of the mixed-effects Cox regression. (Online version in colour.)