Proceedings of the 4th ECE/XIIJ. SIEEC, Godo/lo 1991 into a numerical phenetic species. For this operation a personal computer. The Prothoracic Gland of the (Neuropteroidea: Planipennia)

The prothoracic gland J three suprageneric taxa she R. Giisten and K. Dettner most significant of these w two lobes in all 18 species , Italochrysa (Belonopterygi Another difference shown Key words: green lacewings, defensive secretions, SEM, GC/MS, evolution, phylogeny partly concealed by the pro sa and much more ventrall; Introduction The reservoirs of the ir shape, differ considerably i Some species of green lacewings (Planipennia: Chrysopidae) produce a distinc- of Chrysopa, they nearly J tive scent during molestation, usually described as allylic or faecal-like. As the smaller (relative to body source of the secretion causing the odour, paired prothoracic glands were deter- Cunctochrysa and Chrysopa mined (McDunnough 1909), but later investigations were restricted to a detailed morphological and anatomical description of the glands in Chrysopa per/a by Sulc (1914). An analysis of secretion chemistry in Chrysopa oculata by Blum et al. (1973) revealed the presence of skatole (3-methylindole) as a gland content, which is responsible for the odour. Up to now, all references to the prothoracic glands assume their existence in the strong-smelling species only; a statement by Sulc (1914, p. 3) that they also occur in Chrysoperla carnea, which is inodorous, was obviously overlooked. In order to record the actual distribution of these glands within the family, we examined 20 European chrysopid species for the occurrence of these organs. Besides 18 species of the tribe Chrysopini (Chrysopinae), Italochrysa italica (Chry- sopinae: Belonopterygini) and Nothochrysa fulviceps (Nothochrysinae) were also included in the study. We present the results of investigations of gland morphology and secretion chemistry, and we discuss the probable function of the prothoracic secretion, the morphological, chemical and functional evolution of the gland, and its possible significance for phylogeny and systematics of the family.

Methods Fig. 1. Position of gland open Nothochrysa fulviceps (top), ltt Morphological investigations of the prothoracic gland were carried out by species are not drawn to scale. 1 scanning electron microscopy (SEM) of macerated halves of prothoraces, showing - pleural sclerites the gland reservoir as well as properties of the reservoir opening and fine structure of glandular units. For chemical analysis, we used a gas chromatography/mass spectrometry coup- ling (GC/MS), which provides separation of secretion compounds and gives spe- cific mass spectra which help identify individual substances. Morphological and chemical characters of the prothoracic gland evaluated in this study were entered

60 th ECE/XIJL SIEEC, Godol/o 1991 into a numerical phenetic analysis, creating a phenetic tree of the investigated species. For this operation, we used the program NTSYS-pc 1.50 (Rohlf 1988) on a personal computer. e Chrysopidae ipennia) Results The prothoracic gland proved to be present in all the 20 species studied. The three suprageneric taxa showed a number of differences in gland morphology. The tner most significant of these was the shape of the reservoir (Fig. 1): it is divided into two lobes in all 18 species of Chrysopini, into three less clearly separated lobes in Italochrysa (Belonopterygini), but undivided in Nothochrysa (Nothochrysinae). Another difference shown in Fig. 1 is the position of the gland opening, which is GC/MS, evolution, phylogeny partly concealed by the pronotum in Chrysopini, situated just below it in Jtalochry- sa and much more ventrally so in Nothochrysa. The reservoirs of the investigated species of Chrysopini, while very similar in shape, differ considerably in size. In Peyerimhoffina, Chrysoperla and most species '.hrysopidae) produce a distinc- of Chrysopa, they nearly fill out the prothorax, while they are nearly 4 times allylic or faecal-like. As the smaller (relative to body size) in the species of Nineta. Chrysopidia, Mallada, >rothoracic glands were deter- Cunctochrysa and Chrysopa viridana are intermediate. 1s were restricted to a detailed ands in Chrysopa per/a by Sulc 'a oculata by Blum et al. (1973) as a gland content, which is

Is assume their existence in the 1 14, p. 3) that they also occur in ly overlooked. ;e glands within the family, we occurrence of these organs. nae), Italochrysa italica (Chry- 1s (Nothochrysinae) were also tigations of gland morphology le function of the prothoracic 1al evolution of the gland, and cs of the family.

Fig. I. Position of gland opening slit and reservoir shape in three species of Chrysopidae: Nothochrysa fulviceps (top), Italochrysa ita/ica (middle), Chrysopa per/a (bottom). (The three :c gland were carried out by species are not drawn to scale. Abbreviations: gr - glandular reservoir; go - gland opening; ps 1alves of prothoraces, showing - pleural sclerites · oir opening and fine structure

1phy/mass spectrometry coup- on compounds and gives spe- 1bstances. Morphological and ted in this study were entered

61 The chitinous elements of the glandular units - functional units of a gland cell substances from an exocrim and accessory cells, which create a cuticular ductule - are observable in macerated already been shown in Opilic SEM-preparations (for detailed discussion of glandular units, see Noirot and substances are contained in ti Quennedey 1974). We found that in Chrysopidae, glandular units associated with for defence is found in Nineta the prothoracic gland reservoir are extremely similar to dermal glandular units that gut contents are nearly a distributed over the integument. Interspecific differences concerning shape and tion by all inodorous specie fine structure of glandular units could be shown only in the length of the cuticular Alkenes represent ideal solv duct. In this trait, species of Chrysopa (except Ch. viridana) are most divergent, have little or no repellent or t having ducts of about 80 µm length, compared with 10-30 µm in other species. this hypothetical initial stage Secretion chemistry was analyzed in 13 species from 5 genera of the tribe more and more enhanced du Chrysopini. The 30 substances found can be arranged in 7 groups according to their corresponding with a stepwii chemical structure. A fraction of alkenes is found in all species and, remarkably, its kinds of multicomponent sec composition is very similar in all. The main compound of this fraction is (Z)-4-tri- predators as target organism decene. The other compound groups show various chemical compositions and rected against bats. As the pr< might be derived from quite different biogenetic pathways. They are usually spe- Chrysopidae, it can be used : cific for certain genera, e.g. terpenoids (Chrysopidia), octanoic acid (Chrysoperla), this can be done on different long-chain hydrocarbons (Chrysoperla and Mallada), amides (Chrysopa) apd ska- The subfamilies Nothoch tole (all Chrysopa except Ch. viridana). A special case is observed in Nineta, where gated tribes of Chrysopinae ( no substances other than the alkene fraction are present. ral differences in overall gli examination of this charact( generic taxa within the famil' Discussion sing for the Ankylopterygini, · ni (which are probably not rr The idea that the strong-smelling secretion of Chrysopa species has defensive after the extensive investigati function is· quite straightforward and was first proposed by Melander and Brues (1906) and adopted by most later authors. In view of the great olfactory sensitivity of mammals to skatole (Laffort 1963), bats (Chiroptera) seem to be likely target organisms for the defence secretion, as they are potentially important predators of the night-flying Chrysopidae. Blum et al. (1973), however, found evidence for a repellent effect not only against mammals (mice) but also against (ants). For a number of reasons, we believe that the prothoracic secretion in the inodorous species serves as a defensive allomone as well, rather than representing some kind of pheromone. Firstly, it appears that these species, just as the odorous ones, discharge their gland contents when molested, even though this is difficult to observe in most cases. Also, it is unlikely that this secretion represents a phero- mone playing a role in sexual interactions, as there is no sexual dimorphism and as there are already other pheromone glands known in these (male abdominal glands; Wattebled and Canard 1981 ). Aggregation or alarm pheromones are not to be expected in the solitary green lacewings. The glands of Nineta show the most primitive situation among Chrysopini chemically as well as morphologically. If they are regarded as a model for the initial stage in the evolution of the pro thoracic gland, it must be asked which could be the defensive value of the alkene-containing secretion. A possible hypothesis is that these hydrocarbons act as a solvent and spreading agent for gut contents which are exuded in defence. Discharging faeces or gut contents is the simplest way of chemi- Fig. 2. Dendrograms showing phe cal defence in arthropods (Dettner 1989). The effect of repellent substances con- side: based on multilocus electro tained in gut contents can be both more potent and more prolonged if solvent based on chemical and morpholog 62 :::tional units of a gland cell substances from an exocrine gland are added. A comparable phenomenon has re observable in macerated already been shown in Opiliones (Eisner et al. 1978); in these, however, the active lar units, see Noirot and substances are contained in the glandular secretion. The idea that a mixing of fluids iular units associated with for defence is found in Nineta and other chrysopids is supported by the observation to dermal glandular units that gut contents are nearly always discharged together with the prothoracic secre- ces concerning shape and tion by all inodorous species, and also, less obviously, by the odorous species. the length of the cuticular Alkenes represent ideal solvents for active substances in defensive mixtures, but dana) are most divergent, have little or no repellent or toxic effect on their own (Dettner 1991 ). Derived from 10 µm in other species. this hypothetical initial stage, the defensive value of the secretion could have been om 5 genera of the tribe more and more enhanced during evolution by adding different active substances, 7 groups according to their corresponding with a stepwise enlargement of the gland reservoir. The different .pecies and, remarkably, its kinds of multicomponent secretions might also reflect an adaptation to different )f this fraction is (Z)-4-tri- predators as target organisms, like the skatole-containing secretion possibly di- iemical compositions and rected against bats. As the prothoracic gland is obviously a groundplan character in {ays. They are usually spe- Chrysopidae, it can be used as a valuable tool in phylogeny and systematics, and ctanoic acid (Chrysoperla), this can be done on different taxonomic levels. mides (Chrysopa) a9d ska- The subfamilies Nothochrysinae and Chrysopinae, and also the two investi- observed in Nineta, where gated tribes of Chrysopinae (Belonopterygini, Chrysopini) clearly showed structu- t. ral differences in overall gland morphology, indicating that even a superficial examination of this character might help clarifying the relationships of supra- generic taxa within the family. For future studies, this could especially be promi- sing for the Ankylopterygini, Leucochrysini and the different lineages of Chrysopi- ni (which are probably not monophyletic), whose affinities still remain uncertain wpa species has defensive after the extensive investigation by Brooks and Barnard (1990). :d by Melander and Brues olfactory sensitivity Chrysopidia ciliata a) seem to be likely target Nineta pallida illy important predators of ----Mallada flavifrons found evidence for a ..------1.__ ___ Mallada picteti .t also against arthropods Mallada prasinus Mallada marianus Hhoracic secretion in the M al/ada zelleri 1, rather than representing Mallada ventrulis .pecies, just as the odorous '----Mallada clathratus n though this is difficult to retion represents a phero------Chrysoperla camea ' sexual dimorphism and as ------Cunctochrysa baelica se insects (male abdominal Chrysopa per/a 1rm pheromones are not to Chrysopa walkeri Chrysopa f onnosa uation among Chrysopini Chrysopa dorsalis as a model for the initial ,______Clzrysopa pa/lens e asked which could be the Chrysopa abbreviata possible hypothesis is that '------Clzrysopa viridana for gut contents which are the simplest way of chem i- Fig. 2. Dendrograms showing phenetic relationships of 18 species of Chrysopidae. Left hand side: based on multilocus electrophoresis (from Bullini and Cianchi 1984), right hand side: f repellent substances con- based on chemical and morphological characters of the prothoracic gland more prolonged if solvent 63 It is notable that our results confirmed the well-known archaic nature of the Noirot, Ch. and Quennedev, A subfamily Nothochrysinae, whose prothoracic gland displayed many primitive fea- Entomol. 19, 61-80. · tures (e.g. undivided reservoir, few glandular units). Unfortunately, the chemical Rohlf, F. J. (1988): NTSYS-pc composition of the secretion could not be examined in Nothochrysa. Exeter (N. Y.). The observed differences of the prothoracic gland among the species of Chry- Sulc, K. (1914): Uber die Stinl sopini were less evident and included a few morphological and numerous chemical Ges. Wiss. 11, 1-50. characters. To evaluate the suitability of these characters for phylogenetic investi- Wattebled, S. and Canard, M. gations within this group, a numerical phenetic analysis was carried out, covering perla (L.) (Insecta, Neur the 13 species for which chemical data were available. In Fig. 2 the resulting tree is variations de la parade en compared with the phenogram obtained by Bullini and Cianchi (1984) in a similar Biol. anim. Ser. 13(3), 12' array of species, using multilocus electrophoresis. While our results are based on few and partly incomplete data, and should be viewed carefully concerning actual Au tho branchings, the similarity of both trees (particularly within Chrysopa) is remark- able. It seems that the substances of the prothoracic secretion could be used as chemical markers in a similar way as allozymes and that valuable information for systematics could be obtained, especially if more taxa become known. Finally, it should be mentioned that the prothoracic gland could also prove important for evaluating relationships of families within the order Planipen- nia, whose phylogeny is still under discussion. A prothoracic gland occurs, as far as known, in one other family, the Osmylidae. In these insects, the gland is extrusible, but preliminary investigation on Osmylus fulvicephalus showed some evidence for homology with the prothoracic gland in Chrysopidae; there seem to be some shared characters with Nothochrysa in particular. It is, however, not known, if this gland is a groundplan character of Osmylidae as well. If the prothoracic gland is indeed homologous in the two families, either a sister-group relationship between them or reduction of the gland in other, related families must be assumed.

References

Blum, M. S., Wallace, J.B. and Fales, H. M. (1973): Skatole and tridecene: Identification and possible role in a chrysopid secretion. - Biochem. 3, 353-357. Brooks, S. J. and Barnard, P. C. (1990): The green lacewings of the world: a generic review (: Chrysopidae). -Bull. Br. Mus. nat. Hist. (Ent.) 59, 117-286. Bullini, L. and Cianchi, R. ( 1984): Electrophoretic studies on gene-enzyme systems in chrysopid lacewings. - In: Canard, M., Semeria, Y. and New, T. R. (eds): Biology ofChrysopidae. Den Haag. pp. 48-56. Dettner, K. (1989): Insektenabwehrstoffe - Produktion, Speicherung, Abgabe und Anwen- dung im biologischen Pflanzenschutz. - Z. Umweltchem. Okotox 3, 46-53. Dettner, K. (1991): Solvent-dependent variability of effectiveness of Quinone-defensive sys- tems of Oxytelinae beetles (Coleoptera: Staphylinidae). -Entomol. Gener. 15, 275-292. Eisner, T., Alsop, D. and Meinwald, J. (1978): Secretions of Opilionids, Whip scorpions and Pseudoscorpions. - In: Bettini, S. (ed.): venoms. Berlin pp. 87-99. Laffort, P. ( 1963 ): Essai de standardisation des seuils olfactifs humains pour 192 corps purs. - Archs. Sci.physiol.17, 75-105. McDunnough, J. (1909): Uber den Bau des Darms und seiner Anhange van Chrysopa perla L. -Arch. Naturgesch. 75, 313-360. Melander, A. L: and Brues, C. T. ( 1906): The chemical of some insect secretions. - Bull. Wis. nat. Hist. Soc. 4, 22-36.

64 nown archaic nature of the Noirot, Ch. and Quennedey, A. (1974): Fine structure of insect epidermal glands. -Ann. Rev. splayed many primitive fea- Entomol. 19, 61-80. Jnfortunately, the chemical Rohlf, F. J. (1988): NTSYS-pc: numerical and analysis system (computer software), Nothochrysa. Exeter (N. Y.). among the species of Chry- Sulc, K. (1914): Uber die Stinkdriisen und Speicheldriisen der Chrysopen. - SBer. K biihm. ical and numerous chemical Ges. Wiss. 11, 1-50. !rs for phylogenetic investi- Wattebled, S. and Canard, M. (1981): La parade nuptiale et l'accouplement chez Chrysopa is was carried out, covering perla (L.) (lnsecta, Neuroptera, Chrysopidae). Role des exsertiles du male et n Fig. 2 the resulting tree is variations de la parade en fonction de la receptivite de la femelle. -Annis Sci. nat., Zoo/. Cianchi (1984) in a similar Biol. anim. Ser. 13(3), 129-140. ile our results are based on carefully concerning actual Authors' addres.s: rithin Chrysopa) is remark- R. Giisten and K. Dettner secretion could be used as Department of Ecology II at valuable information for University of Bayreuth ecome known. DW-8580 Bayreuth Germany gland could also ; within the order Planipen- 1racic gland occurs, as far as ects, the gland is extrusible, showed some evidence for e; there seem to be some however, not known, if this If the prothoracic gland is relationship between s must be assumed.

1d tridecene: Identification and 353-357. of the world: a generic review nt.) 59, 117-286. ne-enzyme systems in chrysopid . (eds): Biology of Chrysopidae. icherung, Abgabe und Anwen- Okotox 3, 46-53. 1es.s of Quinone-defensive sys- . Entomol. Gener. 15, 275-292. )pilionids, Whip scorpions and IS. Berlin pp. 87-99. umains pour 192 corps purs. -

\nh:inge von Chrysopa perla L. e of some insect secretions. -

65 Bibliography of the Neuropterida

Bibliography of the Neuropterida Reference number (r#): 8244

Reference Citation: Güsten, R.; Dettner, K. 1991 [1991.??.??]. The prothoracic gland of the Chrysopidae (Neuropteroidea: Planipennia). Pp. 60-65 in Zombori, L.; Peregovits, L. (eds.). Proceedings of the 4th European Congress of Entomology and the XIII Internationale Symposium für die Entomofaunistik Mitteleuropas. Vol. 1. [held 1-6 September 1991, Gödöllö, Hungary]. 2 figures. [BotN ref#8244]

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