[New substances from the defense secretion of the diplopod genus Glomeris. On arthropod defense substances. XXIV]

The Chemistry of the Defensive Secretions of Three Species of Millipedes in the Genus Brachycybe

Millipedes have long been known to produce a diverse array of chemical defense agents that deter predation. These compounds, or their precursors, are stored in high concentration within glands (ozadenes) and are released upon disturbance. The subterclass Colobognatha contains four orders of millipedes, all of which are known to produce terpenoid alkaloids-spare the Siphonophorida that produce terpenes. Although these compounds represent some of the most structurally-intriguing millipede-derived natural products, they are the least studied class of millipede defensive secretions. Here, we describe the chemistry of millipede defensive secretions from three species of Brachycybe: Brachycybe producta, Brachycybe petasata, and Brachycybe rosea. Chemical investigations using mass spectrometry-based metabolomics, chemical synthesis, and 2D NMR led to the identification of five alkaloids, three of which are new to the literature. All identified compounds are monoterpene alkaloids with the new compounds representing indolizidine (i.e. hydrogosodesmine) and quinolizidine alkaloids (i.e. homogosodesmine and homo-hydrogosodesmine). The chemical diversity of these compounds tracks the known species phylogeny of this genus, rather than the geographical proximity of the species. The indolizidines and quinolizidines are produced by non-sympatric sister species, B. producta and B. petasata, while deoxybuzonamine is produced by another set of non-sympatric sister species, B. rosea and Brachycybe lecontii. The fidelity between the chemical diversity and phylogeny strongly suggests that millipedes generate these complex defensive agents de novo and begins to provide insights into the evolution of their biochemical pathways.

Intraspecific variation and phylogeography of the millipede model organism, the Black Pill Millipede Glomerismarginata (Villers, 1789) (Diplopoda, Glomerida, Glomeridae)

The Black Pill Millipede, Glomerismarginata, is the best studied millipede species and a model organism for Diplopoda. Glomerismarginata is widespread, with numerous colour morphs occurring across its range, especially in the south. This study investigates whether colour morphs might represent cryptic species as well as the haplotype diversity and biogeography of G.marginata. The results of the COI barcoding fragment analysis include 97 G.marginata, as well as 21 specimens from seven potentially related species: G.intermedia Latzel, 1884, G.klugii Brandt, 1833 (G.undulata C.L. Koch, 1844), G.connexa Koch, 1847, G.hexasticha Brandt, 1833, G.maerens Attems, 1927, G.annulata Brandt, 1833 and G.apuana Verhoeff, 1911. The majority of the barcoding data was obtained through the German Barcode of Life project (GBOL). Interspecifically, G.marginata is separated from its congeners by a minimum uncorrected genetic distance of 12.9 %, confirming its monophyly. Uncorrected intraspecific distances of G.marginata are comparable to those of other widespread Glomeris species, varying between 0–4.7%, with the largest genetic distances (>2.5 %) found at the Mediterranean coast. 97 sampled specimens of G.marginata yielded 47 different haplotypes, with identical haplotypes occurring at large distances from one another, and different haplotypes being present in populations occurring in close proximity. The highest number of haplotypes was found in the best-sampled area, western Germany. The English haplotype is identical to northern Spain; specimens from southern Spain are closer to French Mediterranean specimens. Analyses (CHAO1) show that approximately 400 different haplotypes can be expected in G.marginata. To cover all haplotypes, it is projected that up to 6,000 specimens would need to be sequenced, highlighting the impossibility of covering the whole genetic diversity in barcoding attempts of immobile soil arthropod species.

"Quinone Millipedes" Reconsidered: Evidence for a Mosaic-Like Taxonomic Distribution of Phenol-Based Secretions across the Julidae

The defensive chemistry of juliformian millipedes is characterized mainly by benzoquinones ("quinone millipedes"), whereas the secretions of the putative close outgroup Callipodida are considered to be exclusively phenolic. We conducted a chemical screening of julid secretions for phenolic content. Most species from tribes Cylindroiulini (15 species examined), Brachyiulini (5 species examined), Leptoiulini (15 species examined), Uncigerini (2 species examined), Pachyiulini (3 species examined), and Ommatoiulini (2 species examined) had non-phenolic, in most cases exclusively benzoquinonic secretions. In contrast, tribes Cylindroiulini, Brachyiulini, and Leptoiulini also contained representatives with predominantly phenol-based exudates. In detail, p-cresol was a major compound in the secretions of the cylindroiulines Styrioiulus pelidnus and S. styricus (p-cresol content 93 %) and an undetermined Cylindroiulus species (p-cresol content 51 %), in the brachyiulines Brachyiulus lusitanus (p-cresol content 21 %) and Megaphyllum fagorum (p-cresol content 92 %), as well as in an undescribed Typhloiulus species (p-cresol content 32 %, Leptoiulini). In all species, p-cresol was accompanied by small amounts of phenol. The secretion of M. fagorum was exclusively phenolic, whereas phenols were accompanied by benzoquinones in all other species. This is the first incidence of clearly phenol-dominated secretions in the Julidae. We hypothesize a shared biosynthetic route to phenols and benzoquinones, with benzoquinones being produced from phenolic precursors. The patchy taxonomic distribution of phenols documented herein supports multiple independent regression events in a common pathway of benzoquinone synthesis rather than multiple independent incidences of phenol biosynthesis.

Chemistry of the sternal gland secretion of the Mediterranean centipede Himantarium gabrielis (Linnaeus, 1767) (Chilopoda: Geophilomorpha: Himantariidae)

The geophilomorph centipede, Himantarium gabrielis, when disturbed, discharges a viscous and proteinaceous secretion from the sternal glands. This exudate was found by gas chromatography-mass spectrometry, liquid chromatography-high resolution mass spectrometry, liquid chromatography-mass spectrometry-mass spectrometry and NMR analyses to be composed of hydrogen cyanide, benzaldehyde, benzoyl nitrile, benzyl nitrile, mandelonitrile, mandelonitrile benzoate, 3,7,6O-trimethylguanine (himantarine), farnesyl 2,3-dihydrofarnesoate and farnesyl farnesoate. This is the first report on the presence of benzyl nitrile and mandelonitrile benzoate in secreted substances from centipedes. Farnesyl 2,3-dihydrofarnesoate is a new compound, while himantarine and farnesyl farnesoate were not known as natural products. A post-secretion release of hydrogen cyanide by reaction of mandelonitrile and benzoyl nitrile was observed by NMR, and hydrogen cyanide signals were completely assigned. In addition, a protein component of the secretion was analysed by electrophoresis which revealed the presence of a major 55 kDa protein. Analyses of the defensive exudates of other geophilomorph families should produce further chemical surprises.

Spider sedation induced by defensive chemicals of milliped prey

Wolf spiders (Lycosa spp.) show delayed induced sedation (total immobilization) of prolonged duration (in the order of days) after attacks upon millipeds (Glomeris marginata). The sedation is specifically attributable to glomerin and homoglomerin, two previously characterized quinazolinones present in the defensive secretion of Glomeris. Median sedative doses for the quinazolinones are in the range of 1-7 mug per spider, a fraction of the total (60-90 mug) present in the secretion of medium to full-grown millipeds. A sedative effect upon an invertebrate predator has not previously been demonstrated for an animal defense. Quinazolinones include the synthetic drug methaqualone (Quaalude), a potent human sedative.

Current status of the Myriapod class diplopoda (millipedes): taxonomic diversity and phylogeny

The arthropod class Diplopoda, the millipedes, ranks among the most diverse groups of terrestrial organisms, with over 12,000 species described. Although they play an important ecological role in most terrestrial ecosystems, little is known about the group's diversity, morphology, and phylogeny compared with other arthropod groups. We review diplopod natural history and discuss the historical and current literature pertaining to millipede morphology, ecology, chemical defenses, and the paleontological record of the group's ancient history. Diplopod systematics, past and present, are reviewed with a focus on taxonomy, collections, and biogeography. The phylogenetics of the class is reviewed, with particular attention on diplopod placement within the Myriapoda and emphasis on recent advances using molecular approaches to phylogenetic reconstruction. We present (a) the first combined morphological and molecular analysis of the millipede orders, and (b) a list of critically evaluated characteristics of nominal clades identifying putative apomorphies.

Convergent evolution of chemical defense in poison frogs and arthropod prey between Madagascar and the Neotropics

With few exceptions, aposematically colored poison frogs sequester defensive alkaloids, unchanged, from dietary arthropods. In the Neotropics, myrmicine and formicine ants and the siphonotid millipede Rhinotus purpureus are dietary sources for alkaloids in dendrobatid poison frogs, yet the arthropod sources for Mantella poison frogs in Madagascar remained unknown. We report GC-MS analyses of extracts of arthropods and microsympatric Malagasy poison frogs (Mantella) collected from Ranomafana, Madagascar. Arthropod sources for 11 "poison frog" alkaloids were discovered, 7 of which were also detected in microsympatric Mantella. These arthropod sources include three endemic Malagasy ants, Tetramorium electrum, Anochetus grandidieri, and Paratrechina amblyops (subfamilies Myrmicinae, Ponerinae, and Formicinae, respectively), and the pantropical tramp millipede R. purpureus. Two of these ant species, A. grandidieri and T. electrum, were also found in Mantella stomachs, and ants represented the dominant prey type (67.3% of 609 identified stomach arthropods). To our knowledge, detection of 5,8-disubstituted (ds) indolizidine iso-217B in T. electrum represents the first izidine having a branch point in its carbon skeleton to be identified from ants, and detection of 3,5-ds pyrrolizidine 251O in A. grandidieri represents the first ponerine ant proposed as a dietary source of poison frog alkaloids. Endemic Malagasy ants with defensive alkaloids (with the exception of Paratrechina) are not closely related to any Neotropical species sharing similar chemical defenses. Our results suggest convergent evolution for the acquisition of defensive alkaloids in these dietary ants, which may have been the critical prerequisite for subsequent convergence in poison frogs between Madagascar and the Neotropics.

A siphonotid millipede (Rhinotus) as the source of spiropyrrolizidine oximes of dendrobatid frogs

Poison frogs of the neotropical family Dendrobatidae contain a wide variety of lipophilic alkaloids, which are accumulated from alkaloid-containing arthropods. A small millipede, Rhinotus purpureus (Siphonotidae), occurs microsympatrically with the dendrobatid frog Dendrobates pumilio on Isla Bastimentos, Bocas del Toro Province, Panamá. Methanol extracts of this millipede contain the spiropyrrolizidine O-methyloxime 236, an alkaloid previously known only from skin extracts of poison frogs, including populations of D. pumilio. Thus, R. purpureus represents a likely dietary source of such alkaloids in dendrobatid frogs.

The role of adhesion in prey capture and predator defence in arthropods

Adhesive devices are used by arthropods not only in terrestrial locomotion but also in prey capture and predator defence. We argue that the physical mechanisms involved in both these contexts must mainly be capillarity and the viscosity of an adhesive secretion, whereas other mechanisms, such as friction or intermolecular forces, are of minor importance. Adhesive prey-capture devices might function as passive devices or might be actively extended toward the prey, sometimes in a very rapid manner. Adhesive mechanisms used for predator defence might involve firm adhesion to the substratum or the discharge of a sticky secretion to immobilize the appendages of the opponent. We review the occurrence of adhesive devices as employed in both functional contexts across the Arthropoda and argue that these mechanisms are of particular importance for slow-moving and relatively clumsy life forms. We discuss three case studies in more detail. (1) Loricera larvae (Carabidae) use galeae with an extremely flexible cuticle in combination with an adhesive secretion. (2) Adult Stenus species (Staphylinidae) employ two highly flexible paraglossae that are covered by an adhesive emulsion of lipid droplets dispersed in an aqueous proteinaceous liquid. (3) Springtails often adhere to the mouthparts, the antennae, the legs, or other parts of the integument of Stenus larvae before being captured with the mandibles.

Evolutionary aspects of cellular communication in the vertebrate hypothalamo-hypophysio-gonadal axis

This review emphasizes the comparative approach for developing insight into knowledge related to cellular communications occurring in the hypothalamus-pituitary-gonadal axis. Indeed, research on adaptive phenomena leads to evolutionary tracks. Thus, going through recent results, we suggest that pheromonal communication precedes local communication which, in turn, precedes communication via the blood stream. Furthermore, the use of different routes of communication by a certain mediator leads to a conceptual change related to what hormones are. Nevertheless, endocrine communication should leave out of consideration the source (glandular or not) of mediator. Finally, we point out that the use of lower vertebrate animal models is fundamental to understanding general physiological mechanisms. In fact, different anatomical organization permits access to tissues not readily approachable in mammals.