Morphology of the granular hemocytes of the Japanese horseshoe crabTachypleus tridentatus and immunocytochemical localization of clotting factors and antimicrobial substances

Summary The structure of hemocytes in the normal state and during blood coagulation, and the intracellular localization of three clotting factors and two antimicrobial factors were examined in the Japanese horseshoe crabTachypleus tridentatus. Two types of hemocytes were found in the circulating blood: non-granular and granular hemocytes. The latter contained numerous dense granules classed into two major types: L- and D-granules. The L-granules were larger (up to 1.5 m in diameter) and less electron-dense than the D-granules (less than 0.6 m in diameter). The L-granules contained three clotting factors and one antimicrobial factor, whereas the D-granules exclusively contained the other antimicrobial factor. After treatment with endotoxin, the L-granules were released more rapidly than the D-granules, although almost all granules were finally exocytosed. The granular hemocyte possessed a single Golgi complex; possible precursor granules of L-granules and D-granules contained tubular and condensed dense material, respectively. These data are discussed in relation to the self-defense mechanisms of the horseshoe crab.     

The invertebrate fauna of the sandstone caves of the Cape Peninsula (South Africa): patterns of endemism and conservation priorities

The temperate sandstone caves of the Cape Peninsula, South Africa, support 85 cavernicolous invertebrate species across six phyla. Six of these, including two blind and depigmented species of insects (Dermaptera) and spiders (Araneae: Hahniidae) were previously unknown. Twenty-one species are endemic to the Peninsula. Thirteen of these are presumed troglobitic Gondwanan relicts, including highly specialized, phylogenetically unique, rare species with restricted distributions and specialized habitat requirements. According to the criteria listed in the IUCN Red List Categories (1994), the onychophoran Peripatopsis alba and crustacean Spelaeogriphus lepidops should be considered Critically Endangered, their extents of occurrence being less than 100km². Furthermore, Data Deficient species, such as the freshwater shrimps Protojanira leleupi and Paramelita barnardi, the spider Hahnia sp.nov., the earwig Dermaptera sp.nov. and the centipede Cryptops stupendus, are likely to be additional Critically Endangered species on account of their exceptional rarity or restricted distributions. The remaining endemic cavernicoles are considered Endangered on account of their limited distributions (extent of occurrence <5000km²). Therefore, conservation considerations are clearly an urgent priority and appropriate recommendations are provided. Management-orientated research, long-term population monitoring and the conservation of pseudokarst areas, are urgent requirements for the conservation of these rare and threatened evolutionary relicts in their isolated island-like habitats.     

Muscular anatomy of a whipspider, Phrynus longipes (Pocock) (Arachnida: Amblypygi), and its evolutionary significance

Skeletal muscles in the whipspider Phrynus longipes are surveyed and compared with those of other chelicerates to clarify the evolutionary morphology and phylogenetic relationships of the arachnids. Representatives of 115 muscle groups are described and illustrated, and their possible functions are proposed. Principal results of this analysis include new functional models for the operation of the pharyngeal and sternocoxal mechanisms in Amblypygi and a greatly expanded list of apparently unique synapomorphies supporting the monophyly of Pedipalpi (= Amblypygi, Schizomida, Thelyphonida).     

Lower Jurassic Arthropod Resting Trace from the Hartford Basin of Massachusetts,USA

Cheliceratichnus lockleyi ichnogen. nov. et ichnosp. nov. is a new ichnotaxon of arthropod resting trace (cubichnium) from the Lower Jurassic (Hettangian) East Berlin Formation in Holyoke, Massachusetts, USA. The trace fossil is preserved as showing many of the external anatomical features of the exoskeleton, which resemble those of some chelicerates, notably sun spiders (Solifugae). The resting trace is directly associated with a trackway of the ichnospecies Acanthichnus cursorius Hitchcock. This is the first described fossil resting trace of a solifugan-like arthropod, and the first direct evidence of a trackmaker of A. cursorius.     

Characters in the book lungs of Scorpiones (Chelicerata,Arachnida) revealed by scanning electron microscopy

The fine structure of the book lungs in 29 species representing ten monophyletic taxa of the Scorpiones (Arachnida) was investigated using scanning electron microscopy (SEM). Scorpion lungs are not homogeneous across the group. Here we describe and score three sets of phylogenetically informative characters: (1) the surface ornament of the lung lamellae, (2) the distal margins of the lamellae and (3) the fine structure of the spiracle margin. Provisional results suggest that reticulation on the surface of the lung lamellae is characteristic of the Buthidae. By contrast, non-buthid scorpions maintain the air space between adjacent lamellae using projecting trabeculae. Typically they are simple struts, but the trabeculae are distally branched in all investigated Scorpionidae, plus at least one species belonging to the Liochelidae. Simple thorns on the lamellar margins probably represent the plesiomorphic condition, while more complex, branched, arcuate morphologies appear to be homoplastic, occurring sporadically in numerous scorpion sub-groups. The tightly packed, hexagonal pillars around the posterior margin of the spiracle support a close relationship between Scorpionidae and Liochelidae, to the exclusion of the Urodacidae.     

Hox genes in sea spiders (Pycnogonida) and the homology of arthropod head segments

The pycnogonids (or sea spiders) are an enigmatic group of arthropods, classified in recent phylogenies as a sister-group of either euchelicerates (horseshoe crabs and arachnids), or all other extant arthropods. Because of their bizarre morpho-anatomy, homologies with other arthropod taxa have been difficult to assess. We review the main morphology-based hypotheses of correspondence between anterior segments of pycnogonids, arachnids and mandibulates. In an attempt to provide new relevant data to these controversial issues, we performed a PCR survey of Hox genes in two pycnogonid species, Endeis spinosa and Nymphon gracile, from which we could recover nine and six Hox genes, respectively. Phylogenetic analyses allowed to identify their orthology relationships. The Deformed gene from E. spinosa and the abdominal-A gene from N. gracile exhibit unusual sequence divergence in their homeodomains, which, in the latter case, may be correlated with the extreme reduction of the posterior region in pycnogonids. Expression patterns of two Hox genes (labial and Deformed) in the E. spinosa protonymphon larva are discussed. The anterior boundaries of their expression domains favour homology between sea spider chelifores, euchelicerates chelicerae and mandibulate (first) antennae, in contradistinction with previously proposed alternative schemes such as the protocerebral identity of sea spider chelifores or the absence of a deutocerebrum in chelicerates. In addition, while anatomical and embryological evidences suggest the possibility that the ovigers of sea spiders could be a duplicated pair of pedipalps, the Hox data support them as modified anterior walking legs, consistent with the classical views.Supplementary material is available for this article at and is accessible for authorized users.Guest editors Jean Deutsch and Gerhard Scholtz     

First divergence time estimate of spiders,scorpions, mites and ticks (subphylum: Chelicerata) inferred from mitochondrial phylogeny

Spiders, scorpions, mites and ticks (chelicerates) form one of the most diverse groups of arthropods on land, but their origin and times of diversification are not yet established. We estimated, for the first time, the molecular divergence times for these chelicerates using complete mitochondrial sequences from 25 taxa. All mitochondrial genes were evaluated individually or after concatenation. Sequences belonging to three missing genes (ND3, 6, and tRNA-Asp) from three taxa, as well as the faster-evolving ribosomal RNAs (12S and 16S), tRNAs, and the third base of each codon from 11 protein-coding genes (PCGs) (COI-III, CYTB, ATP8, 6, ND1-2, 4L, and 4-5), were identified and removed. The remaining concatenated sequences from 11 PCGs produced a completely resolved phylogenetic tree and confirmed that all chelicerates are monophyletic. Removing the third base from each codon was essential to resolve the phylogeny, which allowed deep divergence times to be calculated using three nodes calibrated with upper and lower priors. Our estimates indicate that the orders and classes of spiders, scorpions, mites, and ticks diversified in the late Paleozoic, much earlier than previously reported from fossil date estimates. The divergence time estimated for ticks suggests that their first land hosts could have been amphibians rather than reptiles. Using molecular data, we separated the spider-scorpion clades and estimated their divergence times at 397 ± 23 million years ago. Algae, fungi, plants, and animals, including insects, were well established on land when these chelicerates diversified. Future analyses, involving mitochondrial sequences from additional chelicerate taxa and the inclusion of nuclear genes (or entire genomes) will provide a more complete picture of the evolution of the Chelicerata, the second most abundant group of animals on earth. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Common general morphological pattern of peptidergic neurons in the arachnid brain: crustacean cardioactive peptide-immunoreactive neurons in the protocerebrum of seven arachnid species

A polyclonal antiserum raised against crustacean cardioactive peptide labels 14 clusters of immunoreactive neurons in the protocerebrum of the spiders Tegenaria atrica and Nephila clavipes, and the harvestman (opilionid) Rilaena triangularis. In all species, these clusters possess the same number of neurons, and share similar structural and topological characteristics. Two sets of bilateral symmetrical neurons associated with the optic lobes and the arachnid central body were analysed in detail, comparing the harvestman R. triangularis and the spiders Brachypelma albopilosa (Theraphosidae), Cupiennius salei (Lycosidae), Tegenaria atrica (Agelenidae), Meta segmentata (Metidae) and Nephila clavipes (Araneidae). Sixteen neurons have been identified that display markedly similar axonal pathways and arborization patterns in all species. These neurons are considered homologues in the opilionid and the araneid brains. We presume that these putative phylogenetically persisting neurons represent part of the general morphological pattern of the arachmid brain.     

Opisthosomal fusion and phylogeny of Palaeozoic Xiphosura

Fusion of opisthosomal tergites to form a thoracetron has previously been considered a characteristic of the xiphosuran superfamilies Euproopoidea Eller, 1938, and Limuloidea Zittel, 1885. Evidence is presented here that fusion also occurs in Bellinuroidea Zittel & Eastman, 1913. Results of a cladistic analysis of Palaeozoic xiphosuran genera indicate that Synziphosurina Packard, 1886, is a paraphyletic assemblage of stem-group Xiphosura. Superfamily Paleolimulidae superfam. nov. is erected for families Paleolimulidae Raymond, 1944, and Moravuridae P&íbyl, 1967.     

Central nervous projections of mechanoreceptors in the spider Cupiennius salei Keys.

Summary The basic organization of sensory projections in the suboesophageal central nervous system of a spider (Cupiennius salei Keys.) was analyzed with anterograde cobalt fills and a modified Golgi rapid method. The projections of three lyriform slit sense organs and of tactile hairs located proximally on the legs are described and related to central nerve tracts. There are five main longitudinal sensory tracts in the central region of the suboesophageal nervous mass arranged one above the other. Whereas the three dorsal ones contain fibers from the lyriform organs, the two ventral ones contain axons from the hair receptors. Axons from all three lyriform organs have typical shapes and widely arborizing ipsilateral intersegmental branches and a few contralateral ones. The terminal branches of the afferent projections from identical lyriform organs on each leg form characteristic longitudinal pathways, typical of each organ: U-shaped, O-shaped, or two parallel bundles. The terminations of the hair sensilla are ipsilateral and intersegmental. Two large bilaterally arranged longitudinal sensory association tracts receive inputs from all legs including the dense arborizations from tactile hairs, lyriform organs, and other sense organs. These tracts may serve as important integrating neuropils of the suboesophageal central nervous system.