ERGEBNISSE DER BIOLOGIE HERAUSGEGEBEN VON H. AUTRUM . E. BaNNING· K. v. FRISCH E. HADORN . A. KaHN· E. MAYR . A. PIRSON J. STRAUB . H. STUBBE· W. WEIDEL REDIGIERT VON H. AUTRUM ZWANZIGSTER BAND MIT 34 ABBILDUNGEN SPRINGER-VERLAG BERLIN· GOTTINGEN· HEIDELBERG 1958 ISBN 978-3-540-02262-6 ISBN 978-3-642-51754-9 (eBook) DOI 10.1007/978-3-642-51754-9 Aile Reehte, insbesondere das der Obersetznng in fremde Spraehen, vorbehalten Ohne ausdruekliehe Genehmigung des Verlages ist es aueh nieht gestattet, dieses Bueh oder Teile daraus auf photomechanischem Wege (Photokopie, Mikrokopie) zu vervielfiiltigen © by Springer-Verlag oHG_ Berlin -G5ttingen -Heidelberg 1958 Die Wiedergabe von Gebrauehsnamen, Handelsnamen, Warenbezeichnungen usw_ in diesem Werk berechtigt aueh ohne besondere Kennzeichnung nieht zu der Annahme, daB solehe Namen im Sinn der Warenzeichen- uod Markensdmtz Gesetzgebung als frei zu betrachten waren und daber von jedermann benutzt werden durfen Briihlsche Universit!itsdruekerei GieSen Vorwort Wissenschaft schreitet durch Spezialisierung und deren Dberwindung fort. Es gehort daher zur Methode und zu den Aufgaben der Forschung, die gewonnenen Einzelergebnisse liberschaubar zusammenzufassen. Dberschaubar bedeutet erstens: Beschrankung auf das Gesicherte und das Wesentliche; zweitens: Verstandlichkeit auch fUr den auf verwandten Gebieten arbeitenden Wissenschaftler. Als im Jahr 1925 die "Ergebnisse der Biologie" von K. v. FRISCH, R. GOLDSCHMIDT, W. RUHLAND und H. 'WINTERSTEIN zum erstenmal herausgegeben wurden, sollten dem damals gerade abgeschlossenen "Handbuch der vergleichenden Physio logie" fortlaufend Artikel folgen, um das Handbuch nach dem jeweils neuesten Stand zu erganzen. Viele der Beitrage der Bande 1-19 hatten dementsprechend den Charakter von Handbuchartikeln, waren also beladen mit dem ganzen Ballast der Einzeltatsachen und der speziellen Literatur. Die neuen Bande verfolgen ein anderes Ziel: Sie wollen nicht ein Handbuch erganzen oder ersetzen, sondern vielmehr liber moderne Probleme berichten und sie libersichtlich zusammenfassen. Die Beitrage sollen im Umfang begrenzt sein; sie wollen das Erreichte kritisch dar stellen, offene Fragen herausarbeiten und damit als Grundlage fUr weitere Forschung und Synthese dienen. Herausgeber und Verlag hoffen, daB die "Ergebnisse der Biologie" dem Forscher die Einsicht in Nachbargebiete moglich machen, daB sie aber auch dem Studenten und dem Lehrer an Hochschule und Schule helfen werden, sich liber die Ergebnisse der modernen Biologie zu unter richten und sie unterrichtend weiterzugeben. Die Herausgeber danken dem Verlag, daB er das Wiedererscheinen der "Ergebnisse der Biologie" ermoglicht und ihre Arbeit in groBzligiger Weise unterstlitzt. H. AUTRUM Wlirzburg, im Januar 1958 Inhaltsverzeichnis RICHARDS, A. GLENN, Professor, St. PaulfMinnesota(USA). The Cuticle of Arthropods. With 3 Figures . . . . . . . . . . . . . . . . . . BURKHARDT, DIETRICH, Dr., Wiirzburg. Die Sinnesorgane des Skelet muskels und die nervose Steuerung der Muskeltatigkeit. Mit 12 Abbil- dungen. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 ARNOLD, CARL-GEROLD, Dr., Erlangen. Selektive Befruchtung. Mit 1 Ab- bildung. . . . . . . . . . . . . . . . . . . . . . . . . . . 67 BIER, KARLHEINZ, Priv.-Dozent Dr., Wiirzburg. Die Regulation der Sexualitat in den Insektenstaaten. Mit 4 Abbildungen . . . . . . . . 97 RENNER, MAX, Dr., Miinchen. Der Zeitsinn der Arthropoden. Mit 1 Ab- bildung. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 KRAUSE, GERHARD, Professor Dr., Tiibingen. Induktionssysteme in der Embryonalentwicklung von Insekten. Mit 13 Abbildungen . . .. 159 HERAN, HERBERT, Dr. Graz. Die Orientierung der Bienen im Flug 199 Namenverzeichnis. 240 Sachverzeichnis .. 247 The Cuticle of Arthropods* By A. GLENN RICHARDS, St. Paul/Minn. (USA) Department of Entomology and Economic Zoology, University of Minnesota With 3 Figures Contents Chitin Chemistry . . . • • • • 2 The Chemistry of Sclerotization • 6 The Chemistry of Other Components. 9 Structure of the Cuticle • . . • • 10 The Multiple Barriers of the Cuticle 14 Diversity within the Arthropods. 15 Ecological Aspects of the Cuticle 16 Literature . . • • • . • • . • 19 The present review is intended to cover the major advances that have taken place since the appearance of the author's monograph in 1951. But with the publication of the recent excellent review by WIGGLES WORTH [170], the treatment has been modified to make the present review supplementary in so far as possible. Frequent reference will be made to both of the above. In surveying the literature of the past decade one is impressed with the number of important advances that have been made, especially in cuticle chemistry. The work of HACKMAN is particularly important, partly because he is studying all of the various components found in cuticle. But these advances also show how extremely complex the story of cuticle chemistry and structure is going to become. The reports show that, while the bulk of the cuticle or the ground substance of the cuticle is composed of chitin plus a protein mixture called arthropodin, the impor tant properties are due more to compounds present in such small amounts that they would be classed as trace contaminants until their importance is discovered. This demonstrates the need for much more research on * Paper Number 943, Miscellaneous Journal Series, Minnesota Agricultural Experiment Station, St. Paul, 1, Minnesota, USA. Ergebnisse der Biologie XX 2 A. GLENN RICHARDS cuticle components. Fortunately, several competent chemists have interested themselves in these problems. Biologists should remember, however, that although some rigorous chemical determinations have been made, much of the data on arthropod cuticle are not so soundly based. For much of the work there is no good alternative to histochemistry. Descriptions of color reactions from histochemical tests are one matter, but many of the deductions from them are inconclusive. And histochemical studies sometime lead to the piling of one logical conclusion upon another, the last interpretation depending on a prior one which in turn depends on another which is itself uncertain. For instance, the now commonly stated idea that tyrosine in arthropodin can be oxidized in situ to produce reactive quinones is, as the cautious chemist MASON remarks, only an interesting working hypothesis lacking rigorous documentation. Conclusions today, even many that seem thoroughly satisfying, are largely tentative. The increasing complexity is not only apparent in the literature on chemical components but also in the field of cuticle permeability. Most authors still attempt to explain penetration in terms of static models that can be visualized. However, several recent studies [13, 36, 129J imply that we will soon have to think in terms of dynamic models expressable by mathematical equations but not satisfactorily shown by pictures. What then would I hope to find in the literature a decade hence? I hope for 1. More comparative analyses, especially treating structures not usually studied and species from special ecological niches; 2. More rigorous chemical determinations on components and their reactions by organic chemists and on the molecular architecture by physical chemists; and 3. A beginning of the development by biophysicists of dynamic models expressing penetration phenomena. Chitin Chemistry It is generally agreed that chitin is a linear polysaccharide composed of N -acetylglucosamine residues linked together by p-glycosidic bonds so that the minimal descriptive unit is chitobiose [124]. Current chemical terminology would describe chitin as a p-glycosidic linked polymer of N-acetyl-2-amino, 2-deoxy, D-glucose or even better as a polymer of 2-acetamido, 2-deoxy, IX,D-glucopyranose. These express the over-all picture but there really is no proof that the all units of the chain are of this type. There could well be a small percentage of non-acetylated residues (or even some glucose residues). An occasional non-acetylated residue would account for the trace of glucosamine found after enzymic decomposition by HACKMAN [48J and earlier authors. It would also account for the slight reaction of chitin to the periodic acid-Schiff The Cuticle of Arthropods 3 reaction (which should be blocked by acetylation), and, of more interest, would permit the direct linking of chitin chains to tanning quinones [100]. It is, then, highly desirable to know the degree of homogeneity of the repeating units in a chitin chain but, unfortunately, this is not readily proven because of the possibility of some deacetylation occurring during the chemical manipulations. Several authors have t:;ommented on the low nitrogen values given by KJELDAHL analysis of purified chitin [124] but this can hardly be interpreted as indicating the presence of some non amino residues in the chains when such have not been identified following enzymic decomposition. The chains are reported to have an average length of 31 residues [69 a]. At the supermolecular level, several types of chitin have been found. Two crystallographic types appear well documented. The at-chitin configuration [124] is the common one and the only one known for arthropods. A second type of chain association, .a-chitin, is found in some polychaetes and molluscs. In cephalopods, at-chitin is found in the radula, beak and lining of the gut, but .a-chitin in the skeletal pen '[134J. RUDALL remarks that .a-chitin is found associated with collagen whereas at-chitin occurs alone [103] or in association with a non-collagenous protein such as arthropodin. It seems certain that other types of chitin exist but we do not yet know whether these are all simply different crystallographic configurations. Thus, RUDALL reports that Coelenterate chitin gives a distinct x-ray diffraction pattern, RICHARDS reports a green instead of violet chitosan color test from a· Bry ozoan [124], and KRISHNAN reports an orange chitosan color test for what he considers to be chitin in the epicuticle of a scorpion [84]. The structure and properties of chitin are said to be most like those of metastable cellulose III [103]. Some surprizing discoveries have been made at this level of association of chitin chains. DARMON and RUDALL using polarized infra-red spectroscopy show that the chains are held together by hydrogen bonds that presumably occur between C = 0 and-NRgroupsof the side chains Fig.l. AspatiallydistorteddiagramiIJustra- ting the two principle type of hydrogen (and probably also between C = O· .. RO bonds between chitin chains groups) (Fig. 1). With progressive dea- cetylation, OR ... OR bonds are formed as in cellulose. But one half of the acetyl groups are more readily removed by alkali than the other half. 1* 4 A. GLENN RICHARDS This implies that there are two types of acetyl groups, and it has been suggested that the two types represent cis-and trans-bonding (Fig. 2), but the data do not prove this or show which is more readily deace~ylated. However the chitin chains are held together, they clearly aggregate into larger units called micelles [124J. With the increasing commonness of using electron microscopes, the cuticles from a considerable number of species of various orders have now been examined. Most but not all of the work has been with thin membranes that require no elaborate preparation (peritro phic membranes, gut and tracheal linings, ecdysial membrane). In general, micro fibers of about 100 A diameter are found though a range of 70-200 A is recorded [38, 39, 57, 90, 99, 101, 126, 127, 171J. RIEl, noting the commonness of this dia meter for microfibers of various substan ces, has suggested that this may well re present a general average length of cry , stallinity attainable perpendicular to the NH CO NH main axis in microfibers which are micellar ~'\//~ aggregates. Working with cellulose, FREY CO WYSSLING has subdivided microfibers into aggregates of micelles averaging cis-bonding trans-bcmding 30 x 70 A; this has the important effect Fig. 2. Diagram of the probable linkages, of assigning the amorphous or para related by a screw turn, between chitin crystalline material to a position outside chains. (after RUDALL, 133) the micelle yet inside the microfiber. So much of the data on cellulose is applicable to chitin that this may well be too. Apparently we have a hierarchy of chain associations: chitin chains aggregate into micelles which aggregate into microfibers which, in cuticle, aggregate into microscopically visible fibers known in the literature as "Balken". The suggestion by RICHARDS [124J that this is true has now been well documented by electron microscope and UV microscope examinations [39,90,117, 126J. ENIGK and PFAFF report seeing micro fibers in normal Hypoderma, the fibers decreasing in diameter on removal of the protein; the other authors have had to treat their preparations in a manner dissociating the chitin-protein complex before seeing micro fibers. ENIGK and PFAFF interpret their results as indicating a lipo protein sheath around a chitin core but I see no reason why the fibers might not equally well be of mixed composition. Evidence continues to support the idea that chitin is not a naturally occurring compound but a degenerative chemical product produced in The Cuticle of Arthropods 5 testtubes [124J. To be sure, K. H. MEYER says that the shield of the cephalopod Loligo is pure chitin but there are several conceivable explana tions of this unique case - too little is known about the development of the structure to warrant speCUlation now. In general, chitin is intimately associated with protein. In arthropods, chitin is associated with a group of proteins called arthropodins. Evidence increases that this association is somehow bonded together but we still have no clear idea of what the bonds are or even whether they are chemical or physical in nature. Whatever the nature of the bonds within this glycoprotein, they must be weak because they are readily disrupted by heat or a moderate change of PH' Once the unstable chitin-arthropodin bonding is broken, the highly stable chitin lattice is formed [133]. This is not readily altered. However, the unstable chitin-arthropodin lattice is rendered stable by the tanning process called sclerotization (the fragile erythrocyte is also greatly strengthened by treatment with tannic acid [31J). Supporting evidence for the ability of chitin to combine with proteins has been provided by HACKMAN [49J who first showed that N-acetyl glucosamine can react with arthropodin, peptides and amino acids, especially tyrosine. The union is unstable at acid PH but reasonably stable at higher PH'S. Then, second, HACKMAN [50J reported that purified chitin can adsorb up to 8 % of its weight in protein. The bonding is not affected by reasonable temperatures but is effected by salts and by PH' falling off rapidly above the isoelectric point of chitin and reaching zero at PH 9. He concludes that there is a weak chitin-arthropodin bond of some sort; its easy rupture by a mild PH change he interprets as implying that the bond is neither covalent nor H bonding. The fact that he succeeded in obtaining a maximum of only 8 % adsorbed is not inter pretable. Perhaps it only means that the micelles of his purified chitin were too tight for penetration and that hence adsorption was limited to their surfaces. Certainly the amount of protein adsorbed was far below that found in arthropod cuticle. Chitinases have now been found in a wide variety of organisms. Their properties have been studied in preparations from snails and their intestinal flora [48,70,74, 75J, fungi [158J, and the exuvial fluid of various insects [71, 72, 76, 112J. Destruction of chitin implying the presence of chitinase has been reported for various soil bacteria [11, 165J, various fungi, both free-living [40, 78, 143J and parasitic species that penetrate insect cuticles [64,93, 131, 150J, and, among animals, eelworms, earth worms and soil amebae [155-157J. The recorded PH optima are usually in the range 4.8-5.5 [48, 72, 75, 158J, and the products are acetyl glucosamine plus a trace of glucosamine for crustacean chitin [48J but only acetylglucosamine for Sepia chitin [158J. Thechitinasesfrominsect exuvial fluid have similar PH and temperature optima to the microbial 6 A. GLENN RICHARDS enzymes [71, 72, 76J. The activity of fungal chitinase is said to be augmented by the presence of extra protein [158J. It is also an adaptive enzyme [122 AJ. The use of chitinases is now under sufficient control that TRACEY [159J recommends their use for chitin detection. On the other hand, the museum pest Anthrenus eats insects, pulveri zing the chitin but not digesting it [73J. And the exuvial fluid of maggots which seems not to digest any en do cuticle at molting is reported to lack chitinase [173J. No important advances appear to have been made on the inter mediary metabolism of chitin or cuticle. However it does appear that the synthesis and assemblying of the components is under the control of the animal and independent of environmental conditions except as these affect the development of the whole animal. TSAO and RICHARDS report for Blatta, Tribolium, Tenebrio, Galleria and Phormia that the quantity of chitin and cuticle was little if any altered by variations in temperature, humidity, or nutrition when feeding was ad libitum (previous reports of an effect of feeding on quantity of cuticle relate to quantity of food; this study dealt with composition of the diet). In Tribolium and Phormia the amounts were not altered by diets lacking free carbohydrate but the casein used contained some glucosamine which may well have been utilized as chitin precursor. Within a single stage of a single species the amounts of chitin remained surprizingly constant when values are expressed as per cent of body weight - individual variations from the average seldom exceded 10%. However, as is well-known, the thickness and weight of cuticle does vary considerably from one region of the body to another. Additional quantitative determinations have been published for Periplaneta [25, 117J, Blatta [163J, and Bombyx [153J. The Chemistry of Sclerotization As indicated by TRIM'S work [124J, the proteins are heterogenous even in a single species. Electrophoretic separations of the water-soluble proteins (arthropodin) by HACKMAN [47J show that they are all fairly similar in physical and chemical properties in the seven species studied (Orthop., Coleopt., Hemipt.). Free oc-amino groups were found in four but free carboxyl groups in only one. The same amino acids that have free amino groups in the water-soluble fraction, also have free amino groups in the water-insoluble fraction. There are some differences in amino acid composition but we have yet no idea what this signifies. Thus the water insoluble, alkali-soluble (N NaOH at 50 fractions lack proline and 0) hydroxyproline; the alkali-insoluble fractions lack serine, threonine and lysine. The water-insoluble fraction also contains 3.3% carbohydrate.