Department of Biology, Box 90338, Duke University, Durham, NC 27708, USA.
J Exp Biol. 2011 Sep 15;214(Pt 18):3055-61. doi: 10.1242/jeb.056861.
In crustaceans with compound eyes, the corneal lens of each facet is part of the exoskeleton and thus shed during molting. Here we used an optomotor assay to evaluate the impact of molting on visual acuity (as measured by the minimum resolvable angle, α(min)) in the female blue crab, Callinectes sapidus. We found that visual acuity decreases substantially in the days prior to molting and is gradually recovered after molting. Four days prior to molting, α(min) was 1.8 deg (N=5), a value approximating the best possible acuity in this species. In the 24 h before ecdysis occurred, α(min) increased to 15.0 deg (N=12), corresponding to an eightfold drop in visual acuity. Within 6 days after molting, α(min) returned to the pre-molting value. Micrographs of C. sapidus eyes showed that a gap between the corneal lens and the crystalline cone first appeared approximately 5 days prior to shedding and increased in width as the process progressed. This separation was likely responsible for the loss of visual acuity observed in behavioral tests. In blue crabs, mating is limited to the period of the female's pubertal molt, and a reduction in acuity during this time may have an effect on the sensory cues used in female mate choice. The results described here may be broadly applicable to all arthropods that molt and have particular importance for crustaceans that molt multiple times in their lifetime or have mating cycles that are paired with molting.
在复眼的甲壳动物中，每个小眼的角膜透镜是外骨骼的一部分，因此在蜕皮时会脱落。在这里，我们使用光觉反应测定法评估蜕皮对雌性蓝蟹 Callinectes sapidus 视力敏锐度（以最小分辨角α(min)来衡量）的影响。我们发现，在蜕皮前的几天里，视力明显下降，蜕皮后逐渐恢复。在蜕皮前 4 天，α(min)为 1.8 度（N=5），这一数值接近该物种的最佳视力。在蜕皮前 24 小时，α(min)增加到 15.0 度（N=12），这相当于视力敏锐度下降了 8 倍。蜕皮后 6 天内，α(min)恢复到蜕皮前的值。对蓝蟹眼睛的显微照片显示，角膜透镜和晶状锥体之间的间隙大约在蜕皮前 5 天出现，并且随着蜕皮过程的进行而变宽。这种分离可能是行为测试中观察到的视力丧失的原因。在蓝蟹中，交配仅限于雌性青春期蜕皮期间进行，而在此期间视力敏锐度的降低可能会对用于雌性配偶选择的感官线索产生影响。这里描述的结果可能广泛适用于所有蜕皮的节肢动物，并且对于一生中多次蜕皮或交配周期与蜕皮配对的甲壳动物具有特殊意义。
