Eyespot

Abstract: 1. Lepidoptera belonging to several different families bear eyespot patterns on their wings, often with a very strong resemblance to the vertebrate eye. These have been derived from different morphological structures in different groups, and their evolution is therefore convergent within the order. 2. A study of two individual hand-reared Yellow Buntings has shown that the pursuit of flying insect prey is fully released at the bird's first encounter with a flying butterfly, but that the orientation of the attack is modified by experience. 3. Eyespot patterns are associated with displays which exhibit them. In the case of a Nymphalid butterfly, Nymphalis io, an experiment has shown that the display releases escape responses from Yellow Buntings, and that the major part of this effect is due to the four ocelli on the upper surface of the fore- and hind wings. Experiments with other species of insects suggest that other factors contributing include the bright field of colour surrounding the eyespots, the rhythmic movements of the display, and the rustling noise which accompanies it. The bird's responses to this display waned rapidly in the majority of individuals, but some birds became conditioned to avoid the butterflies altogether. 4. Experiments with models showed that circular patterns presented suddenly to feeding birds (Chaffinches, Yellow Buntings and Great Tits) release escape responses more effectively than do non-circular patterns of the same area and perimeter. An increase in the perimeter of the models, achieved by the use of three concentric circles of the same area as the single circle, increased its releasing value. A flat, eye-like pattern which was so shaded and distorted as to appear three-dimensional was more effective than a similar flat pattern which was not shaded, and hence was more bright. Large models were more effective than similar small ones. Waning was again rapid. The differential responsiveness to circular and non-circular patterns is inborn in the case of Great Tits and Chaffinches. 5. An experiment with mealworms artifically ornamented with small eye-like spots at their extremities has shown that such markings, placed on a prey-object, tend to direct to themselves the attack of Yellow Buntings. The waning of the element of disturbed orientation in the responses is slow, and may not be significant. 6. The deflection and intimidation effects are discussed. The origin of the predator's responses to deflection marks is not known, but it is suggested that intimidating eyespots act by mimicking the eyes of the large avian predators preying on the small insectivorous passerines which are among their natural enemies. It has been shown that many small passerines possess inborn responses to their predators, and it is probable that these are "parasitised" by the eyespot patterns of insects. Eyespot patterns must be regarded as wholly distinct from pseudaposematic colouration. The effect of experience on small passerines, either of the predator-model or of an ocellated imitator, is most usually the reverse of that sustained by a predator encountering the model or mimic in a true case of Batesian or Mullerian mimicry, and the restrictions on the population size of a pseudaposematic insect relative to its model do not apply to insects utilising the inborn responses of their predators.

Abstract: Sexual and natural selection pressures are thought to shape the characteristic wing patterns of butterfly species. Here we test whether sexual selection by female choice plays a role in the mainten...

Abstract: Although largely bilaterally symmetric, the two sides of the unicellular alga Chlamydomonas reinhardtii can be distinguished by the location of the single eyespot. When viewed from the anterior end, the eyespot is always closer to one flagellum than the other, and located at an angle of approximately 45 degrees clockwise of the flagellar plane. This location correlates with the position of one of four acetylated microtubule bundles connected to the flagellar apparatus. Each basal body is attached to two of these microtubule rootlets. The rootlet that positions the eyespot is always attached to the same basal body, which is the daughter of the parental/daughter basal body pair. At mitosis, the replicated basal body pairs segregate in a precise orientation that maintains the asymmetry of the cell and results in mitotic poles that have an invariant handedness. The fusion of gametic cells during mating is also asymmetric. As a result of asymmetric, but different, locations of the plus and minus mating structures, mating preferentially results in quadriflagellate dikaryons with parallel flagellar pairs and both eyespots on the same side of the cell. This asymmetric fusion, as well as all the other asymmetries described, may be necessary for the proper phototactic behavior of these cells. The invariant handedness of the spindle pole, eyespot position, and mating structure position appears to be based on the inherent asymmetry of the basal body pair, providing an example of how an intracellular pattern can be determined and maintained.

Abstract: Background Butterfly and moth eyespots can share a similar appearance, involving multiple concentric rings of colored scales, but usually occuring in non-homologous positions on the wing. Within the butterflies, on the other hand, spots that share the same homologous position may not share the concentric ring structure; and, in butterfly species that have eyespots with concentric rings, ectopic eyespots with a similar ring structure can be induced by means of a simple epidermal wound. The extent to which all these eyespots, natural or induced, share similar genes and developmental mechanisms is investigated here by means of protein in-situ localizations in selected butterfly and moth species. In addition to looking at some of the transcription factors previously identified as being involved in eyespot formation, we also tested the involvement of candidate genes from the Wingless and TGF-β signaling pathways as putative morphogens for eyespot development.