Michael Seiter

Functional anatomy of the pretarsus in whip spiders (Arachnida, Amblypygi).

Whip spiders (Amblypygi) are a small, cryptic order of arachnids mainly distributed in the tropics. Some basal lineages (families Charinidae and Charontidae) have adhesive pads on the tips of their six walking legs. The present study describes the macro- and ultrastructure of these pads and investigates their contact mechanics and adhesive strength on smooth and rough substrates. Furthermore, the structure of the pretarsus and its kinematics are compared in Charon cf. grayi (with an adhesive pad) and Phrynus longipes (without an adhesive pad). The adhesive pads exhibit an elaborate structure with a unique combination of structural features of smooth and hairy foot pads including a long transversal contact zone performing lateral detachment, a thick internally-branched cuticle with longitudinal ribs and hexagonal surface microstructures with spatulate keels. The contact area of the pads on smooth glass is discontinuous due to the spatulate microstructures with a discontinuous detachment, which could be observed in vivo by high speed videography at a rate of up to 10,000 fps. Adhesive strength was measured with vertical whole animal pull-off tests, obtaining mean values between 55 and 200 kPa. The occurrence of viscous lipid secretions between microstructures was occasionally observed, which, however, seems not to be a necessity for good foothold. The results are discussed in relation to the whip spiders ecology and evolution. Structure-function relationships of the adhesive pads are compared to those of insects and vertebrates.

A new species of the South East Asian genus Sarax Simon, 1892 (Arachnida: Amblypygi: Charinidae) and synonymization of Sarax mediterraneus Delle Cave, 1986

A new species of the whip spider genus Sarax Simon, 1892 from Cebu Island in the Philippines is described: Sarax huberi sp. nov. With the description of this species, the diversity of the genus is increased to three species in the Philippines. Some additional data on their natural environment and their specific habitat are presented and compared with sibling species. The synonymization of Sarax mediterraneus Delle Cave, 1986 with Sarax buxtoni (Gravely, 1915) is carried out.

Description of Sarax buxtoni (Gravely 1915) (Arachnida: Amblypygi: Charinidae) and a new case of parthenogenesis in Amblypygi from Singapore

Abstract The type material of Sarax buxtoni (Gravely 1915) cannot be located and has to be considered as lost. Therefore, a description compiled from a population in Singapore is provided, including morphological and taxonomical details presented for the first time. Comparisons with closely related species are supplied. Furthermore, we describe the occurrence of parthenogenesis in a population of S. buxtoni, representing the first case of asexual reproduction in a member of the genus Sarax Simon 1892.

Stygophrynus orientalis sp. nov. (Amblypygi: Charontidae) from Indonesia with the description of a remarkable spermatophore

Here Stygophrynus orientalis sp. nov. is described, a new charontid whip spider from Banggai Island, Indonesia, representing the most eastern record of the genus exceeding the formerly postulated restriction of its distribution western of the Wallace Line. In addition, the third known spermatophore of a Stygophrynus species is presented, which differs remarkably from those previously described from the genus. Finally, the cerotegument structure of the new species is depicted and compared with that of other Charontidae and Charinidae.

Description and First Record of Phrynus tessellatus (Pocock, 1894) (Arachnida: Amblypygi: Phrynidae) from Northwestern Trinidad, with the Description of Its Mating Behaviour

Abstract We illustrate Phrynus tessellatus in detail from northwestern Trinidad and present the first record of a population in South America. In addition, we describe the mating behaviour and spermatophore formation, which show no significant differences useful for taxonomic analysis within the genus, but among different genera and families. However, after deposition of the spermatophore on the substrate, the male modifies the anterior parts of the head with its chelicera. This behaviour differs markedly from related phrynid species. The purpose of this unexpected procedure is not clear and further research is necessary.

Whip spiders (Amblypygi, Arachnida) of the Western Palaearctic-a review.

All records of the two amblypygid species occurring in the Western Palaearctic are mapped and both species (Charinus ioanniticus and Musicodamon atlanteus) are discussed. Charinus ioanniticus is known from the Eastern Mediterranean (Greece, Turkey, Israel and Egypt) from 10 localities and Musicodamon atlanteus is known from the Maghreb (Morocco, Algeria) from three localities. All records are mapped.

Whip spiders (Amblypygi) become water-repellent by a colloidal secretion that self-assembles into hierarchical microstructures.

BackgroundAmong both plants and arthropods, super-hydrophobic surfaces have evolved that enable self-cleaning, locomotion on water surfaces, or plastron respiration. Super-hydrophobicity is achieved by a combination of non-polar substances and complex micro- and nano-structures, usually acquired by growing processes or the deposition of powder-like materials.ResultsHere we report on a multi-phasic secretion in whip spiders (Arachnida, Amblypygi), which externally forms durable, hierarchical microstructures on the basically smooth cuticle. The solidified secretion crust makes the previously highly wettable cuticle super-hydrophobic. We describe the ultrastructure of secretory cells, and the maturation and secretion of the different products involved.ConclusionWhip spiders represent intriguing objects of study for revealing the mechanisms of the formation of complex microstructures in non-living systems. Understanding the physical and chemical processes involved may, further, be of interest for bio-inspired design of functional surface coatings.

Numerical simulation of colloidal self-assembly of super-hydrophobic arachnid cerotegument structures

Certain arachnids exhibit complex coatings of their exoskeleton, consisting of globular structures with complex surface features. This, so-called, cerotegument is formed by a multi-component colloidal secretion that self-assembles and cures on the body surface, and leads to high water repellency. Previous ultrastructural studies revealed the involvement of different glandular cells that contribute different components to the secretion mixture, but the overall process of self-assembly into the complex regular structures observed remained highly unclear. Here we study this process from a theoretical point of view, starting from the so-called Tammes-problem. We show that slight changes of simple parameters lead to a variety of morphologies that are highly similar to the ones observed in the species specific cerotegument structures of whip-spiders. These results are not only important for our understanding of the formation of globular hierarchical structures in nature, but also for the fabrication of novel surface coatings by colloidal lithography.

The water-repellent cerotegument of whip-spiders (Arachnida: Amblypygi)

The cuticle of arthropods is usually composed of layers of a chitin-protein-microcomposite, a proteinaceous epicuticle and a thin lipid coating. However, in some instances a thick cement layer (cerotegument) covers the cuticle and may produce elaborate microstructures. This has previously been described for millipedes and mites. Here we report the previously unknown presence of a superhydrophobic cerotegument in whip-spiders (Ambypygi) and reveal its variation in ultrastructure and water-repellence between species. We discuss the relevance of found micro-morphological and physical characters for taxonomy and phylogenetics of this group, and the potential biological functions.

The South African scorpion Pseudolychas ochraceus (Hirst, 1911) (Scorpiones: Buthidae) can reproduce by parthenogenesis

Abstract Of all scorpion species described to date, only a small fraction are known to reproduce without fertilization by a male, instead producing offspring by parthenogenesis. Here we show that isolated females of the buthid Pseudolychas ochraceus (Hirst, 1911) are capable of parthenogenetic reproduction and we provide data on the postembryonic growth of this species.