Razowski, Józef

Wojtusiak, Janusz

Folia Biologica

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Jagiellonian Univeristy Repository

Folia biologica (Kraków), vol. 54 (2006), No 1-2Cornea of Ommatidia in Lepidoptera (Insecta) – a Scanning ElectronMicroscope StudyJózef RAZOWSKI and Janusz WOJTUSIAKAccepted January 25, 2006RAZOWSKI J., WOJTUSIAK J. 2006. Cornea of ommatidia in Lepidoptera (Insecta) – ascanning electron microscope study. Folia biol. (Kraków) 54: 49-53.The external surface of facets of representatives of 19 families of Lepidoptera is discussedand illustrated. Two types of structures are recognized, this with nipples predominate. Theother structures (pleats) developed probably in the course of a reduction. The ultrastructure ofsurface in the form of granulation is described.Key words: Lepidoptera, ommatidium, cornea, scanning electron microscopy.Józef RAZOWSKI, Department of Invertebrate Zoology, Institute of Systematics and Evolutionof Animals, Polish Academy of Sciences, S³awkowska 17, 31-016 Kraków, Poland.E-mail: razowski@isez.pan.krakow.plJanusz WOJTUSIAK, Zoological Museum, Jagiellonian University, R. Ingardena 6, 30-060Kraków, Poland.E-mail: wojt@zuk.iz.uj.edu.plThe outer surface of ommatidia in insects haslong been treated as being smooth (e.g. by YAGI &KOYAMA 1963). BERNHARD and MILLER (1962)in some Lepidoptera and later (RAZOWSKI &WOJTUSIAK 2004) in some Tortricidae e.g. inCnephasia incertana and Archips crataeganus,were the first to discover their complicated struc-ture. Under the higher magnification (cf. illustra-tions) of the scanning electron microscope it isseen as a dense agglomeration of processes (ap-proximately 25 per one square micrometer in Ar-chips crataeganus), arranged in more or less longrows, forming altogether a kind of a brush. Theseprocesses are referred to as nipples.The function of this structure was then hypothe-sized and explained by BERHARD (1967) andBERHARD and MILLER (1968).Among the examined taxa there is another typeof the outer surface of ommatidium devoid of anynipples but consisting of numerous irregularpleats. This type of surface, unknown to date inLepidoptera, was already found in Musca domes-tica, Muscidae, Diptera by BERNHARD (1967).Material and MethodsMaterialIn course of the present study 23 species of Lepi-doptera belonging to 21 families were examined,from the most primitive among the European taxato highly specialized ones.List of studied taxa:Micropterigidae: Micropterix calthella (Linnaeus)Nepticulidae: Fomoria septembrella (Stainton)Adelidae: Nemophora metallica (Poda)Incurvariidae: Incurvaria muscalella ([Denis &Schiffermüller])Yponomeutidae: Yponomeutinae: Yponomeutaplumbella ([Denis & Schiffermüller]), Swammer-damia caesiella (Hübner)Argyresthinae: Argyresthia spinosella StaintonPlutellidae: Plutella xylostella (Linnaeus)Zygaenidae: Zygaena filipendulae (Linnaeus)Sesiidae: Synanthedon tipuliformis (Clerck)Cossidae: Cossus cossus (Linnaeus)Tortricidae: Cnephasia incertana (Treitschke),Archips crataeganus (Scopoli)Pterophoridae: Pterophorus pentadactyla (Linnaeus)Pyralidae: Pleuroptyla ruralis (Scopoli)Lasiocampidae: Dendrolimus pini (Linnaeus)Saturniidae: Saturnia pavonia (Linnaeus)Sphingidae: Deilephila elpenor (Linnaeus)Lycaenidae: Maculinea teleius (Bergsträsser)Nymphalidae:Nymphalinae:Vanessaatalanta(Linnaeus)Satyrinae: Cheimas opalinus (Staudinger)Notodontidae: Notodonta dromedarius (Linnaeus)Noctuidae: Noctua pronuba (Linnaeus)MethodsDry specimens were used; the eyes were dustedwith gold in a vacuum chamber and their structureswere observed and photographed by means of aField Emission Scanning Electron Microscope Hi-tachi S-4700 by courtesy of Scanning Electron Mi-croscopy Unit of the Faculty of BiologicalSciences, Jagiellonian University, Kraków.ResultsThere are two types of outer structure of the cor-nea in Lepidoptera. Type one with nipples presentand type two with pleats.Type one appears in Micropterix calthella (Figs1, 2) and Plutella xylostella (Figs 3, 4). The nipplesare slender, circular in transverse section, equallydistanced from one another, forming regular rowson the outer surface of facets. This regularity isweaker in the intervenal spaces (Figs 4, 5). In theformer species the number of nipples is muchhigher than in P. xylostella. The localization ofnipples in P. xylostella is illustrated in a longitudi-nal section of cornea by WANG & HSU (1982). Thedensity of nipples on facets is probably species-specific but not characteristic of the families. InNotodonta dromedarius (Fig. 6) these distancesare at average as large as the diameters of nipples,however, in Zygaena filipendulae (Fig. 7) the ar-rangement of the nipples is very dense. In the latterthe transverse section of nipples is analogical tothat of the facets as they become hexagonal, moreor less regular. In all other species examined, ex-cept for those mentioned as type two, the shapesand arrangements of nipples are rather uniform.Intermediate forms. The surface of the omma-tidium of Notodonta dromedarius (Fig. 6) is cer-tainly of the type one, e.g. with distinct but shortnipples. They are irregularly arranged, roundedapically or somewhat elongate. Some elongateones show distinct fusions of two neighboringsimple nipples. The distances between the nipplesare large. The irregularity of the arrangement ofnipples and a diminution of spaces between themare found in Zygaena filipendulae (Fig. 7).Type two – pleats. They are found in Yponomeu-tidae in two species, viz., Yponomeuta plumbella(Figs 8-10) and Swammerdamia caesiella ( Fig. 11).The pleats cover the entire outer surfaces of eachfacet and their density in median parts and the mar-gins is the same. They were not found in the inter-facetal spaces. They are irregularly high, beingslightly depressed between rounded convexities.Some parts of these structures are very short andare reminiscent of solitary nipples of type one. Thesingle convexities are innumerous, entirely or inpart isolated from the pleats. The concavities arevariably sized and deep.An intermediate structure of the outer surface offacets is found in Saturnia pavonia, Saturniidae(Fig. 12). Pleats are short or represented by sepa-rate convexities, two or three in a series and thespaces between them are rather irregular and shal-low, diffusely edged. In Cossus cossus, Cossidae(Fig. 13) the nipples are still preserved, separatebut irregularly arranged and the spaces betweenthem are narrow.Ultrastructure of corneaIn all examined species small, rounded or ellipticconvexities occur referred to here as granules. Onthe top parts of the nipples they are dense and ar-ranged rather irregularly e.g. in Micropterix cal-thella (Figs 13, 14) and in Cheimas opalinus (Fig.15) or form indistinct rows (e.g. in Deilephila elpe-nor). Their size is not species-specific (e.g. theyare much larger in Noctua pronuba than in Ptero-phorus pentadactylus). They certainly occur alsoon the lateral surfaces (not examined but somegranules are seen in Fig. 15 in Cheimas), betweennipples (in Cossus cossus, Fig. 13), and in betweenthe pleats (Fig. 10, Yponomeuta plumbella). Therole of granules is not known but they are probablyof optical importance. Judging from their distribu-tion they develop before the formation of nipples.DiscussionType one structure (nipples) is found in the ma-jority of families, type two (pleats ) is found onlyin one examined family (Yponomeutidae). How-ever, there is one exception in the subfamilyArgyresthiinae (Argyresthia spinosella) in whichthe nipples are fully developed. Intermediateforms were found in Cossus cossus and Saturniapavonia.Type one is more generalized as nipples arefound in the primitive family of Micropterigidae.Type two was probably developed by a reductionof spaces between nipples and fusion of some ofthem. The presence of these two types is not corre-lated systematically nor with the mode of activityof the moths.J. RAZOWSKI, J. WOJTUSIAK50Cornea in Lepidoptera 51Figs 1-8. Fig. 1. Arrangement of nipples in Micropterix calthella, Fig. 2. Micropterix calthella, fragment of cornea, Fig. 3.Facet of Plutella xylostella, Fig. 4. Intervenal space of Plutella xylostella, Fig. 5. Intervenal space of Micropterix calthella,Fig. 6. Arrangement of nipples of Notodonta dromedaries, Fig. 7. Arrangement of nipples of Zygena filipendulae, Fig. 8.Facets of Yponomeuta plumbella.Figs 9-16. Fig. 9. Pleats of Yponomeuta plumbella, Fig. 10. Pleats of Yponomeuta plumbella with granulations seen, Fig. 11.Pleats of Swammerdania caesiella, Fig. 12. Intermediate structure of cornea in Saturnia pavonia, Fig. 13. Intermediatestructure of cornea in Cossus cossus, Fig. 14. Granules of nipples in Micropterix calthella, Fig. 15. Granules of nipples inCheimas opalinus, Fig 16. Transverse section through interfacetal hairs of Vanessa atalanta.J. RAZOWSKI, J. WOJTUSIAK52Thenipplesoccuron thewhole surfaceof thecorneabutare lessabundant in the intervenalareas (Figs1,5).Additional microstructure, granulation, was dis-covered on the cornea. The granules occur both onthe outer surfaces of the pleats, nipples and be-tween them (as seen in Figs 10, 13).AppendixInterfacetal hair. The shapes of hairs are ratherwell known. The only case presented here is thetransverse section of the hair in Vanessa atalanta(Fig. 16) with a distinct inner channel.AcknowledgementsThe authors are much indebted to Mrs JadwigaFABER and Mrs Zuzanna BANACH for their help inmaking SEM photographs and to Mr Artur CZEKAJfor arrangement of illustrations.ReferencesBERNHARD C. G. 1967. Structural and functional adaptationin a visual system. Endevour 26: 79-84.BERNHARD C. G., MILLER W. H. 1962. A corneal nipple pat-tern in insect compound eyes. Acta physiol. Scand. 56:385-386.BERNHARD C. G., MILLER W. H. 1968. Evidence for visualfunction of corneal interference filters. J. Insect Physiol. 17:2287-300.RAZOWSKI J., WOJTUSIAK J. 2004. A few characters of theadult compound eye and its peripheral area in some Tortrici-dae (Insecta: Lepidoptera). Genus 15: 267-274.WANG C-H., HSU S.-J. 1982. The compound eye of diamond-back moth, Plutella xylostella (L.) and its pigment migra-tion. Bull. Inst. Zool. Acad. Sinica 21: 75-92.YAGI N., KOYAMA, N. 1963. The compound eye of the Lepi-doptera. Approach from organic evolution. Shinkyo-Press,Tokyo. 319 pp.Cornea in Lepidoptera 53

Cornea of ommatidia in Lepidoptera (Insecta) : a scanning electron microscope study

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Cornea of ommatidia in Lepidoptera (Insecta) : a scanning electron microscope study

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