Laboratory of Neuroethology, Sokendai (The Graduate University for Advanced Studies), Shonan Village, Hayama 240-0193, Japan.
J Exp Biol. 2010 Dec 1;213(Pt 23):4023-9. doi: 10.1242/jeb.048678.
Recent studies on butterflies have indicated that their colour vision system is almost species specific. To address the question of how this remarkable diversity evolved, we investigated the eyes of the glacial Apollo, Parnassius glacialis, a living fossil species belonging to the family Papilionidae. We identified four opsins in the Parnassius eyes--an ultraviolet- (PgUV), a blue- (PgB), and two long wavelength (PgL2, PgL3)-absorbing types--and localized their mRNAs within the retina. We thus found ommatidial heterogeneity and a clear dorso-ventral regionalization of the eye. The dorsal region consists of three basic types of ommatidia that are similar to those found in other insects, indicating that this dorsal region retains the ancestral state. In the ventral region, we identified two novel phenomena: co-expression of the opsins of the UV- and B-absorbing type in a subset of photoreceptors, and subfunctionalization of long-wavelength receptors in the distal tier as a result of differential expression of the PgL2 and PgL3 mRNAs. Interestingly, butterflies from the closely related genus Papilio (Papilionidae) have at least three long-wavelength opsins, L1-L3. The present study indicates that the duplication of L2 and L3 occurred before the Papilio lineage diverged from the rest, whereas L1 was produced from L3 in the Papilio lineage.
最近对蝴蝶的研究表明，它们的色觉系统几乎是特定于物种的。为了解决这个显著多样性是如何进化的问题，我们研究了冰川阿波罗蝴蝶（Parnassius glacialis）的眼睛，它是一种属于凤蝶科的活化石物种。我们在 Parnassius 眼睛中鉴定出了四种视蛋白——一种紫外线（PgUV）、一种蓝色（PgB）和两种长波长（PgL2、PgL3）吸收型——并在视网膜内定位了它们的 mRNA。因此，我们发现了小眼的异质性和眼睛明显的背腹区域化。背部区域由三种与其他昆虫相似的基本类型小眼组成，表明这个背部区域保留了祖先状态。在腹侧区域，我们发现了两个新现象：UV 和 B 吸收型视蛋白在一部分光感受器中的共表达，以及长波长受体在远端层次的亚功能化，这是由于 PgL2 和 PgL3 mRNA 的差异表达所致。有趣的是，来自亲缘关系密切的凤蝶属（Papilio）的蝴蝶至少有三种长波长视蛋白，L1-L3。本研究表明，L2 和 L3 的复制发生在凤蝶谱系与其他谱系分化之前，而 L1 是在凤蝶谱系中从 L3 产生的。
