Segmentation,neurogenesis and formation of early axonal pathways in the centipede,Ethmostigmus rubripes (Brandt)

Summary We have examined the embryo of the centipedeEthmostigmus rubripes to determine the degree of evolutionary conservatism in the developmental processes of segmentation, neurogenesis and axon formation between the insects and the myriapods. A conspicuous feature of centipede embryogenesis is the early separation of the left and right sides of the ganglionic primordia by extra-embryonic ectoderm. An antibody to the protein encoded by theDrosophila segmentation geneengrailed binds to cells in the posterior margin of the limb buds in the centipede embryo, in common with insect and crustacean embryos. However, whereas in insects and crustaceans this protein is also expressed in a subset of cells in the neuroectoderm, the anti-engrailed antibody did not bind to cells in the ganglionic primordia of the centipede embryo. Use of the BrdU labelling technique to mark mitotically active cells revealed that neuroblasts, the ubiquitous neuron stem cell type in insects, are not present in the centipede. The earliest central axon pathways in the centipede embryo do not arise from segmentally repeated neurons, as is the case in insects, but rather by the posteriorly directed growth of axons originating from neurons located in the brain. Axonogenesis by segmental neurons begins later in development; the pattern of neurons involved is not obviously homologous to the conservative set of central pioneering neurons found in insects. Our observations point to considerable differences between the insects and the myriapods in mechanisms for neurogenesis and the formation of central axon pathways, suggesting that these developmental processes have not been strongly conserved during arthropod evolution.     

Taxonomy of the centipede Scolopendra laeta Haase (Chilopoda: Scolopendridae) in Australia

Scolopendra laeta Haase, 1887, which is widespread in the western and southern parts of Australia, is redescribed from the large number of available specimens. Five intraspecific forms are distinguished by their colour patterns, and their distributions are mapped.     

On the function of the ultimate legs of some Scolopendridae (Chilopoda,Scolopendromorpha)

The function of the variously shaped ultimate legs of Scolopendridae is briefly reviewed. Their function in Scolopendra heros Girard, 1853, Scolopendra subspinipes Leach, 1815, Scolopendra morsitans (Linnaeus, 1758), Scolopendra galapagoensis Bollman, 1889, Scolopendra hainanum Kronmüller, 2012, Scolopendra spinosissima Kraepelin, 1903 Cormocephalus aurantiipes (Newport, 1844) and Ethmostigmus trigonopodus (Leach, 1817), in which they are least specialised has been investigated. Specimens were tapped with forceps on different parts of the trunk to simulate the attack of a predator. When tapped on the first third of the trunk (near the head), the centipedes attacked the forceps with their forcipules. When tapped on the last third or the ultimate legs, they adopted a warning position, raising the ultimate legs to display the ventral and medial prefemoral spines as well as the spined coxopleural processes. In some cases the centipedes attacked the forceps with the claws of the ultimate legs by chopping down on them after lifting the legs high into the warning position. When tapped in the mid part of the trunk, the centipedes curled sideways to reach the forceps with their forcipules and ultimate legs simultaneously. Scolopendra galapagoensis not only lifted the ultimate legs into the warning position but also the last 3-4 pairs of locomotory legs, presenting their distodorsal prefemoral spines. This resembles the warning posture of some spiders. In addition to their function in warning behaviour, defensive stabbing, ritualised meeting reactions and during courtship behaviour, the ultimate legs may in addition act as hooks and perhaps be involved in species recognition. No evidence was found that the ultimate legs are used to catch prey, nor of prey or predators being held between the prefemora.     

The fine structure of the midgut epithelium in a centipede,Scolopendra cingulata (Chilopoda,Scolopendridae), with the special emphasis on epithelial regeneration

Scolopendra cingulata has a tube-shaped digestive system that is divided into three distinct regions: fore-, mid- and hindgut. The midgut is lined with a pseudostratified columnar epithelium which is composed of digestive, secretory and regenerative cells. Hemocytes also appear between the digestive cells of the midgut epithelium. The ultrastructure of three types of epithelial cells and hemocytes of the midgut has been described with the special emphasis on the role of regenerative cells in the protection of midgut epithelium. The process of midgut epithelium regeneration proceeds due to the ability of regenerative cells to proliferate and differentiate according to a circadian rhythm. The regenerative cells serve as unipotent stem cells that divide in an asymmetric manner.Additionally, two types of hemocytes have been distinguished among midgut epithelial cells. They enter the midgut epithelium from the body cavity. Because of the fact that numerous microorganisms occur in the cytoplasm of midgut epithelial cells, we discuss the role of hemocytes in elimination of pathogens from the midgut epithelium. The studies were conducted with the use of transmission electron microscope and immunofluorescent methods.     

The life histories and distribution of the centipedes Rhysida nuda togoensis and Ethmostigmus trigonopodus (Scolopendromorpha: Scolopendridae) in Nigeria

Observations on populations of Rhysida nuda togoensis and Ethmostigmus trigonopodus in Zaria, Nigeria, show that growth rates are very rapid and life cycles shorter than in centipedes from temperate regions. R. nuda togoensis reproduces when one year old and, in all probability, E. trigonopodus does so as well.
It is suggested that both species are enabled to continue feeding in damp areas after the rains have ended by virtue of their mobility and large size (with consequent greater resistance to desiccation). Increasing aridity drives them into crevices in the soil where a relatively rich fauna may persist through the dry season. The young appear at the beginning of the rains, thereby having the entire rainy season available for feeding.
The taxonomy of R. nuda togoensis is discussed and the distribution of both species in Nigeria is described. They are virtually absent from the dry sudan savanna vegetation belt.     

On the true identity of Schendylurus (Schendylotyn) integer Chamberlin, 1926, a termitophilous ballophilid centipede (Chilopoda: Geophilomorpha)

Schendylurus (Schendylotyn) integer Chamberlin, 1926, originally described as a member of the Schendylidae, is transferred here to the Ballophilidae as Taeniolinum integer n. comb. and redescribed after the type specimen. Taeniolinum setosum guadeloupensis Demange and Pereira, 1985 is elevated to specific rank.     

Effect of urbanization on centipede (Chilopoda) diversity in the Wielkopolska-Kujawy Lowlands of western Poland

Over fifty years of research data from various sources were compiled and analyzed in order to determine the effect of urbanization on centipede diversity in the Wielkopolska-Kujawy Lowlands of western Poland. Urbanization has had a significant effect on species composition and community structures. However, it has not reduced overall species richness and diversity in the centipede fauna. The centipede fauna from built-up areas was found to be rich and varied. The habitats with the highest levels of species richness were the city of Poznań and the beech forests in the surrounding region.     

Organization of deutocerebral neuropils and olfactory behavior in the centipede Scutigera coleoptrata (Linnaeus, 1758) (Myriapoda: Chilopoda)

Myriapods represent an arthropod lineage, that originating from a marine arthropod ancestor most likely conquered land independently from hexapods and crustaceans. Establishing aerial olfaction during a transition from the ocean to land requires molecules to be detected in gas phase instead of in water solution. Considering that the olfactory sense of myriapods has evolved independently from that in hexapods and crustaceans, the question arises if and how myriapods have solved the tasks of odor detection and odor information processing in air. Comparative studies between arthropod taxa that independently have established a terrestrial life style provide a powerful means of investigating the evolution of chemosensory adaptations in this environment and to understand how the arthropod nervous system evolved in response to new environmental and ecological challenges. In general, the neuroethology of myriapods and the architecture of their central nervous systems are insufficiently understood. In a set of experiments with the centipede Scutigera coleoptrata, we analyzed the central olfactory pathway with serial semi-thin sectioning combined with 3-dimensional reconstruction, antennal backfilling with neuronal tracers, and immunofluorescence combined with confocal laser-scanning microscopy. Furthermore, we conducted behavioral experiments to find out if these animals react to airborne stimuli. Our results show that the primary olfactory and mechanosensory centers are well developed in these organisms but that the shape of the olfactory neuropils in S. coleoptrata is strikingly different when compared with those of hexapods and malacostracan crustaceans. Nevertheless, the presence of distinct neuropils for chemosensory and mechanosensory qualities in S. coleoptrata, malacostracan Crustacea, and Hexapoda could indicate a common architectural principle within the Mandibulata. Furthermore, behavioral experiments indicate that S. coleoptrata is able to perceive airborne stimuli, both from live prey and from a chemical extract of the prey. These results are in line with the morphological findings concerning the well-developed olfactory centers in the deutocerebrum of this species.     

Morphometric and meristic diversity of the species Scolopendra cingulata Latreille, 1829 (Chilopoda: Scolopendridae) in the Mediterranean region

Scolopendra cingulata Latreille, 1829 is the commonest scolopendromorph species in the Mediterranean area. However, its morphological and geographic variation has not been examined so far, and therefore robust hypotheses about the factors that have shaped that variability are lacking. We examined, using multivariate methods for 19 morphometric and meristic characters, the morphological variation of that species using a comprehensive sample of 503 adult specimens from 130 restricted geographic localities. The localities were distributed in three major geographic areas (Balkans, Asia Minor-Middle East, and Italy) in order to discern biological entities and to estimate the morphological relationships between populations and geographic regions. Results showed significant differences between the three geographic groups. Characters such as the distance between the paramedian sulci of the 7th and 8th tergite, the number of antennal segments, the number of spines on the dorsal side of 21st prefemur and number of spines on the 21st prefemoral process significantly discriminated populations of S. cingulata along a west-east geographic gradient. Both eastern (Balkan) and easternmost populations (Asia Minor-Middle East) showed higher mean values of antennal articles and spines of 21st prefemur than the Italian populations. No significant morphological variation was discovered between the sexes of S. cingulata apart from cephalic width and distance between the two paramedian sulci of the 7th and 8th tergite. Based on certain morphometric differences among the three major geographic regions, we suggest that S. cingulata originated in the east and colonized south European area from two different geographic routes. It is suggested that west-east morphological trend of S. cingulata is related either to the prominent palaeogeographic events of the area or to the competition with S. oraniensis Lucas, 1846 in the western Mediterranean.     

Hemocytes of the centipede Scutigera coleoptrata (Chilopoda,Notostigmophora) with notes on their interactions with the tracheae

The hemocytes of Scutigera coleoptrata were investigated by light and electron microscopy. Four types of hemocytes were identified: prohemocytes, plasmatocytes, granulocytes, and spherulocytes. Only granulocytes could be distinguished from the three other types by May-Grünwald staining, as this is the only hemocyte type demonstrating an eosinophilic reaction. Shape and size give further indications for distinguishing the cell types. In addition, differentiation is possible on the basis of their ultrastructure. However, only a combination of all three methods (staining and light and electron microscopy) allows clear separation of the cell types. As transitional stages between the cell types occur in S. coleoptrata, it is likely that prohemocytes, plasmatocytes, and granulocytes are ontogenetic stages of a single cell lineage. Special cell components and their possible functions are described. Plasmatocytes exocytose tubular structures that probably play a role in coagulation processes. These tubular structures develop in the grana of plasmatocytes. Also, a special arrangement of microtubules and microfilaments was demonstrated. For the first time interactions between hemocytes and tracheae are documented within the Chilopoda. It is assumed that the hemocytes meet their oxygen requirements directly from the tracheae. Phylogenetic implications of the results are discussed.     

Lithobius (Monotarsobius) monoforaminis sp. n., a new species of lithobiid centipede from central China (Chilopoda, Lithobiomorpha, Lithobiidae)

The present paper describes a new species Lithobius (Monotarsobius) monoforaminissp. n. (Lithobiomorpha: Lithobiidae) recently discovered from Shaanxi and Shanxi provinces, Central China. Morphologically it resembles Lithobius (Monotarsobius) minimus Farzalieva, 2006 from Eastern Kazakhstan, but could be well distinguished from the latter having only one pore on the coxae of legs 12-15 and different plectrotaxy, and by lacking a wart on the male tibia 15. A key to the Chinese Lithobius (Monotarsobius) species is presented.     

Prey orientation and the role of venom availability in the predatory behaviour of the centipede Scolopendra subspinipes mutilans (Arthropoda: Chilopoda)

Many animal phyla contain clades in which most or all species are venom-injecting predators. An example, in the arthropods, is the class Chilopoda, containing the approximately 3500 species of centipedes. Very little ecological or behavioural work yielding quantitative data has been conducted on centipede predation. Here, we describe a study of this kind. Our experiments employed one centipede species - a large tropical one, Scolopendra subspinipes mutilans - and two species of prey - a cricket, Gryllus assimilis, and a locust, Schistocerca gregaria. We conducted two experiments. The first was aimed at investigating the extent to which the centipedes attacked prey in particular tagmata as opposed to at random over the whole body surface. The results showed that the centipedes were highly selective, preferring to attack the head or thorax rather than the abdomen; indeed, they often reoriented the prey in order to achieve this. A possible explanation of this behaviour is to maximize the speed with which the neurotoxins in the venom reach either the brain or the thoracic ganglia that control limb movement. The second experiment was aimed at investigating the effect of venom-extraction on the attack rate, and specifically at testing if the magnitude of any such effect differed between the two types of prey, which differ considerably in size. The results showed a major effect of venom extraction in relation to both types of prey, but with the time taken to return to a 'normal' attack rate being longer in the case of the larger prey-type, namely the locust. We discuss these results in relation to the 'venom optimization hypothesis' and, more generally, to the principle of minimizing the production/use of venom, which is an energetically expensive resource.     

Ultrastructural investigation of a salivary gland in a centipede: structure and origin of the maxilla I-gland of Scutigera coleoptrata (Chilopoda, Notostigmophora)

The maxilla I-gland of Scutigera coleoptrata was investigated using light and electron microscopy methods. This is the first ultrastructural investigation of a salivary gland in Chilopoda. The paired gland opens via the hypopharynx into the foregut and extends up to the third trunk segment. The gland is of irregular shape and consists of numerous acini consisting of several gland units. The secretion is released into an arborescent duct system. Each acinus consists of multiple of glandular units. The units are composed of three cell types: secretory cells, a single intermediary cell, and canal cells. The pear-shaped secretory cell is invaginated distally, forming an extracellular reservoir lined with microvilli, into which the secretion is released. The intermediary cell forms a conducting canal and connects the secretory cell with the canal cell. Proximally, the intermediary cell bears microvilli, whereas the distal part is covered with a distinct cuticle. The cuticle is a continuation of the cuticle of the canal cells. This investigation shows that the structure of the glandular units of the salivary maxilla I-gland is comparable to that of the glandular units of epidermal glands. Thus, it is likely that in Chilopoda salivary glands and epidermal glands share the same ground pattern. It is likely that in compound acinar glands a multiplication of secretory and duct cells has taken place, whereas the number of intermediary cells remains constant. The increase in the number of salivary acini leads to a shifting of the secretory elements away from the epidermis, deep into the head. Comparative investigations of the different head glands provide important characters for the reconstruction of myriapod phylogeny and the relationships of Myriapoda and Hexapoda.     

The hemocytes of the centipedeLithobius forficatus (Chilopoda,Lithobiomorpha)

Summary Five different types of hemocytes are found within the hemolymph ofLithobius forficatus: (1) small prohemocytes, (2) very actively spreading plasmatocytes, (3) granulocytes which have a lower spreading ability but tend to agglutinate, (4) spherulocytes which are filled with spherules, and (5) presumably, a coagulocyte, characterized by instant disintegration. Cystocytes as described forL. forficatus in the literature are preparation artifacts. Cell types are characterized by electron microscopy and in vitro and vital staining techniques at the light microscopic level. Results are discussed with reference to different nomenclatures and functions of hemocytes in other arthropods.     

Comparative toxicity of lead shot in black ducks (Anas rubripes) and mallards (Anas platyrhynchos)

In winter, pen-reared and wild black ducks (Anas rubripes), and game farm and wild mallards (Anas platyrhynchos), maintained on pelleted feed, were sham-dosed or given one number 4 lead shot. After 14 days, dosed birds were redosed with two or four additional lead shot. This dosing regimen also was repeated in summer using pen-reared black ducks and game farm mallards. Based upon mortality, overt intoxication, weight change, delta-aminolevulinic acid dehydratase activity and protoporphyrin concentration, black ducks and mallards were found to be equally tolerant to lead shot. However, captive wild ducks were more sensitive than their domesticated counterparts, as evidenced by greater mortality and weight loss following lead shot administration. This difference may be related to stress associated with captivity and unnatural diet.     

Chromosome study of Lithobius forficatus (Lithobiomorpha, Chilopoda)

The diploid number 2n = 46 and the chromosome arm number NF = 74 are described in Lithobius forficatus from Olsztyn (Poland). Analyses of silver and CMA3-stained mitotic chromosomes suggest that a single chromosome pair has active NORs which correspond to G-C-rich (CMA3-positive) chromatin. Heteromorphism of the largest metacentric chromosome pair was observed. The sex chromosomes were not identified. Size polymorphism of the first chromosome pair was found.     

Biogeography in a continental island: population structure of the relict endemic centipede Craterostigmus tasmanianus (Chilopoda, Craterostigmomorpha) in Tasmania using 16S rRNA and COI

We used 16S ribosomal RNA (rRNA) and cytochrome c oxidase subunit I (COI) sequence data to investigate the population structure in the centipede Craterostigmus tasmanianus Pocock, 1902 (Chilopoda: Craterostigmomorpha: Craterostigmidae) and to look for possible barriers to gene flow on the island of Tasmania, where C. tasmanianus is a widespread endemic. We first confirmed a molecular diagnostic character in 28S rRNA separating Tasmanian Craterostigmus from its sister species Craterostigmus crabilli (Edgecombe and Giribet 2008) in New Zealand and found no shared polymorphism in this marker for the 2 species. In Tasmania, analysis of molecular variance analysis showed little variation at the 16S rRNA and COI loci within populations (6% and 13%, respectively), but substantial variation (56% and 48%, respectively) among populations divided geographically into groups. We found no clear evidence of isolation by distance using a Mantel test. Bayesian clustering and gene network analysis both group the C. tasmanianus populations in patterns which are broadly concordant with previously known biogeographical divisions within Tasmania, but we did not find that genetic distance varied in a simple way across cluster boundaries. The coarse-scale geographical sampling on which this study was based should be followed in the future by sampling at a finer spatial scale and to investigate genetic structure within clusters and across cluster boundaries.     

Gene expression during postembryonic segmentation in the centipede <Emphasis Type="Italic">Lithobius peregrinus</Emphasis> (Chilopoda,Lithobiomorpha)

Postembryonic segmentation (anamorphosis) is widespread among arthropods, but only partially known as for its developmental mechanics and control. Studies on developmental genetics of segmentation in anamorphic arthropods are mostly limited to the germ band stage, during early phases of embryonic development. This work presents the first data on the postembryonic expression of a segmentation gene in a myriapod. Using real-time PCR, we analyzed engrailed expression patterns during the anamorphic stages of the centipede Lithobius peregrinus. A variation pattern in en RNA level during anamorphosis suggests that gene expression is precisely modulated during this period of development and that engrailed is mainly expressed in the posterior part of the body, in the newly differentiating segments of each stage. As anamorphosis is possibly the primitive segmentation mode in arthropods, the postembryonic en expression pattern documented here provides evidence for a conservation of en role in ontogeny, across the embryonic/postembryonic boundary, as well as in phylogeny, across the same boundary, but in the opposite direction, from primitive postembryonic expression to the more derived expression in clades with exclusively embryonic segmentation.     

Morphology and diversity of the forcipules in Strigamia centipedes (Chilopoda,Geophilomorpha)

The morphology of the venomous limbs (forcipules) of 13 species of Strigamia and of six other geophilomorphs was studied with light microscopy, scanning electron microscopy, and, for a subsample, with confocal laser scanning microscopy. In all Strigamia species a well-distinct denticle is present invariantly on the inner side of the terminal article (tarsungulum), in sub-basal position, just proximal to a faint transverse sulcus and a cuticular introflexion that corresponds to the insertion point of a tendon. Strigamia species differ mainly in size and shape of the denticle and thickness of the distal part of the tarsungulum, suggesting some functional diversity in piercing and handling prey. Anatomical evidence supports the hypothesis that the tarsungulum corresponds to two ancestral articles and a denticle at the basis of the tarsungulum originated multiple times within geophilomorphs, however in different positions corresponding to either the ancestral sub-terminal article (in Strigamia, other Geophiloidea and some Schendylidae) or the ancestral terminal article (in the himantariid Thracophilus).