Adult stemmata of the butterfly Vanessa cardui express UV and green opsin mRNAs

Department of Ecology and Evolutionary Biology, Comparative and Evolutionary Physiology Group, University of California, 321 Steinhaus Hall, Irvine, CA 92697, USA.
Cell and Tissue Research (Impact Factor: 3.57). 02/2005; 319(1):175-9. DOI: 10.1007/s00441-004-0994-3
Source: PubMed


Adult stemmata are distinctive insect photoreceptors located on the posterior surfaces of the optic lobes. They originate as larval eyes that migrate inward during metamorphosis. We used a combination of light microscopy and in situ hybridization to examine their anatomical organization in the butterfly Vanessa cardui and to test for the presence of visual pigments, the light sensitive components of the visual transduction pathway. The bilateral cluster of six internal stemmata is located near the ventral edge of the lamina. They retain the dark screening pigment and overlying crystalline cones of the larval stemmata. We found two opsin mRNAs expressed in the stemmata that are also expressed, respectively, in UV-sensitive and green-sensitive photoreceptor cells in the compound eye. A third mRNA that is expressed in blue-sensitive photoreceptor cells of the compound eye was not expressed in the stemmata. Our results reinforce the idea that the adult stemmata are not merely developmental remnants of larval eyes, but remain functional, possibly as components of the circadian input channel.

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    • "The role of the stemmata in photoperiodism has been examined in many lepidopterans (Tanaka, 1950; Geispits, 1957; Claret, 1966; Kono, 1970; Hayes, 1971; Seugé and Veith, 1976; Shimizu, 1982; Shimizu and Hasegawa, 1988), but a subordinate role was shown only in the large white butterfly Pieris brassicae (Seugé and Veith, 1976). After metamorphosis, the stemmata remain as the stemmata-derived organs that contain visual pigments and remain photosensitive during the pupal or adult stages (Ichikawa, 1991; Briscoe and White, 2005). "
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    • "As bees possess both insectlike and vertebrate-like opsins (Velarde et al. 2005), whereas Drosophila possess only insect-like opsins, it is possible that bees rely exclusively on an opsin-based photoreceptor system (both retinal and extraretinal) to entrain their circadian clocks. Importantly, a novel putative lightsensitive organ was recently discovered in the third layer of the optic lamina of bumblebees, the ''lamina organ'' which expresses a UV and potentially other opsins (Spaethe and Briscoe 2005). The lamina organ may thus be a key extraretinal light input channel to the bee circadian clock. "
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    • "The same rhodopsin visual pigment gene family paralogs are expressed in Bolwig organ and adult compound eye photoreceptors [Rh5 and Rh6], whereas a different paralog, Rh2, is expressed in the ocelli, the prominent single lens accessory visual organs of the adult (Helfrich-Forster et al., 2002; Malpel et al., 2002; Pichaud and Deplan, 2001; Pollock and Benzer, 1988; Yasuyama and Meinertzhagen, 1999). The expression of Rh5 and Rh6 orthologs in the stemmata and adult ommatidia of lepidopteran species suggests that this aspect of the Drosophila visual system is ancestral (Briscoe and White, 2005). As will be discussed in detail, there is also a significant overlap between the gene network regulating Drosophila Bolwig organ specification and that coordinating adult compound eye specification (Daniel et al., 1999; Suzuki and Saigo, 2000). "
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