Wasserman G S, Cheng Z
Department of Psychological Sciences, Purdue University, West Lafayette, Ind 47907-1364, USA.
Biol Signals. 1996 Sep-Oct;5(5):247-62. doi: 10.1159/000109198.
The carapace characteristics of horseshoe crabs (Limulus polyphemus) have been correlated by others with male mating performance and it has also been suggested that such mating differences might depend on visual differences. The effect of carapace character on horseshoe crab vision was therefore noninvasively investigated using the electroretinogram (ERG) of the lateral compound eye as a measure. Male Limulus were dichotomized on three carapace dimensions: clear versus dark eyes, light versus dark carapaces, and presence versus absence of barnacles. All dichotomizations gave similar results: No crab was ERG-blind. Analyses based on ERG magnitude yielded trivial sensitivity differences between these groups. However, analyses based on ERG latency indicated that response speeds exhibited reliably different trends between groups: Although responses to dim flashes were similar for all animals, increasing flash intensity produced significantly greater changes in the latencies of the ERGs in uniform males than in variegated males. This interactive dependence of ERG speed differences on flash energy cannot be the result of greater light absorption by the variegated specimens' darkened corneas. The visual capacities of variegated specimens are therefore somewhat altered, but certainly not absent. Equalizing animal size between groups did not measurably affect these results, implying that age was not a factor. The previously reported correlation of an individual male's appearance with its performance in mating competitions is extended by these data to include its sensory functioning as well.
其他人已将鲎（美洲鲎）的背甲特征与雄性交配表现联系起来，并且有人提出这种交配差异可能取决于视觉差异。因此，以外侧复眼的视网膜电图（ERG）作为衡量指标，对背甲特征对鲎视觉的影响进行了非侵入性研究。将雄性美洲鲎在三个背甲维度上进行二分：眼睛清晰与昏暗、背甲浅色与深色、有无藤壶附着。所有二分法都得出了相似的结果：没有一只鲎的ERG是失明的。基于ERG幅度的分析在这些组之间产生了微不足道的敏感性差异。然而，基于ERG潜伏期的分析表明，各组之间反应速度呈现出可靠的不同趋势：尽管所有动物对暗光闪烁的反应相似，但随着闪光强度增加，纯色雄性鲎的ERG潜伏期变化比杂色雄性鲎的显著更大。ERG速度差异对闪光能量的这种交互依赖性不可能是杂色标本深色角膜吸收更多光线的结果。因此，杂色标本的视觉能力有所改变，但肯定不是没有视觉能力。使各组动物大小相等并没有明显影响这些结果，这意味着年龄不是一个因素。这些数据扩展了先前报道的个体雄性外观与其在交配竞争中的表现之间的相关性，使其也包括了其感觉功能。
