Schumacher Sarah, Burt de Perera Theresa, von der Emde Gerhard
Institut für Zoologie, Universität Bonn, Endenicher Allee 11-13, 53115 Bonn, Germany.
Department of Zoology, University of Oxford, South Parks Road, OX1 3PS Oxford, United Kingdom.
J Physiol Paris. 2016 Oct;110(3 Pt B):151-163. doi: 10.1016/j.jphysparis.2016.11.008. Epub 2016 Dec 12.
The weakly electric fish Gnathonemus petersii can recognise objects using active electrolocation. Here, we tested two aspects of object recognition; first whether shape recognition might be influenced by movement of the fish, and second whether object discrimination is affected by the presence of electrical noise from conspecifics. (i) Unlike other object features, such as size or volume, no parameter within a single electrical image has been found that encodes object shape. We investigated whether shape recognition might be facilitated by movement-induced modulations (MIM) of the set of electrical images that are created as a fish swims past an object. Fish were trained to discriminate between pairs of objects that either created similar or dissimilar levels of MIM of the electrical images. As predicted, the fish were able to discriminate between objects up to a longer distance if there was a large difference in MIM between the objects than if there was a small difference. This supports an involvement of MIMs in shape recognition but the use of other cues cannot be excluded. (ii) Electrical noise might impair object recognition if the noise signals overlap with the EODs of an electrolocating fish. To avoid jamming, we predicted that fish might employ pulsing strategies to prevent overlaps. To investigate the influence of electrical noise on discrimination performance, two fish were tested either in the presence of a conspecific or of playback signals and the electric signals were recorded during the experiments. The fish were surprisingly immune to jamming by conspecifics: While the discrimination performance of one fish dropped to chance level when more than 22% of its EODs overlapped with the noise signals, the performance of the other fish was not impaired even when all its EODs overlapped. Neither of the fish changed their pulsing behaviour, suggesting that they did not use any kind of jamming avoidance strategy.
弱电鱼彼得氏裸臀鱼能够利用主动电定位识别物体。在此，我们测试了物体识别的两个方面：第一，形状识别是否可能受鱼的运动影响；第二，物体辨别是否受同种个体电噪声的影响。（i）与其他物体特征（如大小或体积）不同，尚未在单个电图像中发现编码物体形状的参数。我们研究了鱼游过物体时产生的一组电图像的运动诱导调制（MIM）是否有助于形状识别。训练鱼区分成对的物体，这些物体产生的电图像的MIM水平相似或不同。正如预测的那样，如果物体之间的MIM差异大，鱼能够在更远的距离区分物体；如果差异小，则不能。这支持了MIM参与形状识别，但不能排除使用其他线索。（ii）如果噪声信号与电定位鱼的放电（EOD）重叠，电噪声可能会损害物体识别。为避免干扰，我们预测鱼可能会采用脉冲策略来防止重叠。为了研究电噪声对辨别性能的影响，在有同种个体或回放信号的情况下测试了两条鱼，并在实验过程中记录电信号。令人惊讶的是，鱼对同种个体的干扰具有免疫力：当一条鱼超过22%的EOD与噪声信号重叠时，其辨别性能降至随机水平，而另一条鱼即使所有EOD都重叠，其性能也未受损。两条鱼都没有改变它们的脉冲行为，这表明它们没有使用任何一种干扰避免策略。
