MYGALOMORPH SPIDERS (ARANEAE: DIPLURIDAE) FROM THE LOWER CRETACEOUS CRATO LAGERSTÄTTE, ARARIPE BASIN, NORTH-EAST BRAZIL

Abstract:  The first mygalomorph spiders from the Lower Cretaceous Crato Lagerstätte of Cearà Province, north-east Brazil, are described, from adult males and females, in two new genera and species: Cretadiplura ceara Selden, gen. et sp. nov. and Dinodiplura ambulacra Selden, gen. et sp. nov. They belong to the extant family Dipluridae, hitherto known as fossils only from Tertiary strata; thus this occurrence extends the family record by some 90 myr.     

The affinities of mites and ticks: a review

Mites and ticks can be divided into two well-defined clades, Anactinotrichida and Actinotrichida, for which a recent work formalized a suite of putative autapomorphies and reciprocal differences. Whether they are sister-taxa – forming a monophyletic Acari – is more controversial. Earlier supporters of two independent origins for mites largely failed to demonstrate convincing synapomorphies between either of the two lineages and other arachnid orders; although recent work on reproductive biology revealed explicit characters of this nature. Furthermore, some of the characters proposed in support of a monophyletic Acari do not stand up to detailed scrutiny when compared with Arachnida in general. Effective morphological comparisons between mites and other arachnids are hindered by incompatible nomenclature and long-standing, mite-specific characters which are difficult to score for other arachnids. Furthermore, taxon-specific characters restricted to individual mite groups have sometimes been treated erroneously as 'typical' for all Acari. Here, previous hypotheses of mite affinities are reviewed. Historically, authors have debated whether mites are basal arachnids or highly derived. Excluding weakly supported early hypotheses, mites have been resolved – in whole or in part – as sister-group of all other Arachnida (based on tagmosis), closely related to Opiliones (based mostly on genital morphology), Palpigradi (based on controversial interpretations of limb morphology), Solifugae (based mostly on the mouthparts, but now perhaps also reproductive characters) and Ricinulei (based on hexapodal larvae and perhaps mouthparts). We cannot provide a final resolution here, but we aim to highlight important character sets which should be included in subsequent phylogenetic analyses, as well as useful areas for future investigations: particularly tagmosis and the nature of the gnathosoma.     

First British Mesozoic Spider, From Cretaceous Amber Of The Isle Of Wight, Southern England

Cretamygale chasei , a new genus and species of spider, is described from a single specimen preserved in amber of early Barremian age from the Isle of Wight. This is the oldest (and second Cretaceous) amber spider to be described, and the first record of a Mesozoic spider from Britain. It belongs to the group Bipectina of the infraorder Mygalomorphae, and is tentatively referred to the family Nemesiidae. It is the oldest bipectinate, extending the record by around 90 myr, the only known fossil nemesiid, and the second oldest fossil mygalomorph.     

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.     

Amblypygid-fungal interactions: The whip spider exoskeleton as a substrate for fungal growth

Fungi and arthropods represent some of the most diverse organisms on our planet, yet the ecological relationships between them remain largely unknown. In animals, fungal growth on body surfaces is often hazardous and is known to cause mortality. In contrast, here we report the presence of an apparently non-harmful mycobiome on the cuticle of whip spiders (Arachnida: Amblypygi). The associations are not species-specific and involve a diversity of fungal species, including cosmopolitan and local decomposers as well as entomopathogens. We discuss the ecology of the detected fungal species and hypothesize that the thick epicuticular secretion coat of whip spiders (the cerotegument) promotes fungal growth. It is possible that this relationship is beneficial towards the host if it leads to parasite control or chemical camouflage. Our findings, which are the first from this arthropod lineage, indicate that non-pathogenic interactions between arthropods and fungi may be much more widespread than predicted and call for more studies in this area.     

Identification key to the species of Amblyolpium Simon (Pseudoscorpiones: Garypinidae), with first record of Amblyolpium bellum Chamberlin from Iran

A key based on bibliographic sources is given for identifying the 15 extant known pseudoscorpion species of the genus Amblyolpium recorded from different localities throughout the world. Species of Amblyolpium mostly occur in the Mediterranean basin, the Near to Far East, and the genus is only recorded with one species from South America. Amblyolpium bellum is redescribed and illustrated based on four males and two females collected for the first time from southern Iran.     

Spermatozoa of an Old World Ricinulei (Ricinoides karschii, Ricinoidae) with notes about the relationships of Ricinulei within the Arachnida

The ultrastructure of spermatozoa is a valuable tool for phylogenetic and systematic studies. Ricinulei are enigmatic and poorly studied arachnids. So far, spermatozoa are only known from New World ricinuleids. The goals were to study, by means of light and transmission electron microcopy, the spermatozoa of an Old World species with regard to their phylogenetic implications, e.g., does the sperm structure contribute to the debated sister-group relationship of Acari and Ricinulei. The spermatozoa are coiled-flagellate and characterized by a cap-like acrosomal vacuole covered by electron-dense material, an elongated nucleus covered by a manchette of microtubules during spermiogenesis, an axoneme with a 9+2 microtubular pattern, a nuclear tube and axonemal basis which both originate underneath the acrosomal vacuole and cleistospermia as transfer form equipped with three intracellular plates. The data of the present study did not support a close relationship of Ricinulei and Acari which have aflagellate sperm with various synapomorphies as e.g., lacking nuclear envelopes/membranes in Actinotrichida (very similar to Solifugae) or vacuolated spermatozoa in Anactinotrichida. Affinities of Ricinulei are discussed in the light of the ultrastructure of arachnid spermatozoa.     

Hair regeneration in a solfugid chemotactile sensillum during moulting (Arachnida: Solifugae)

Summary The hair regeneration of a chemotactile sensillum was studied in the sunspiderGluvia during moulting. The sensilla in the old cuticle remain connected to the epidermis by dendrites which extend outwards during apolysis. The trichogen cells forming the new hairshaft in the exuvial space grow along the chemoreceptive dendrites, while the mechanoreceptive dendrites run separately. Morphogenetic aspects are discussed in comparison to results from other arthropods.     

Vouchering DNA‐barcoded specimens: test of a nondestructive extraction protocol for terrestrial arthropods

Morphology‐based keys support accurate identification of many taxa. However, identification can be difficult for taxa that are either not well studied, very small, members of cryptic species complexes, or represented by immature stages. For such cases, DNA barcodes may provide diagnostic characters. Ecologists and evolutionary biologists deposit museum vouchers to document the species studied in their research. If DNA barcodes are to be used for identification, then both the DNA and the specimen from which it was extracted should be vouchered. We describe a protocol for the nondestructive extraction of DNA from terrestrial arthropods, using as examples members of the orders Acarina, Araneae, Coleoptera, Diptera, and Hymenoptera chosen to represent the ranges in size, overall sclerotization, and delicacy of key morphological characters in the group. We successfully extracted sequenceable DNA from all species after 1–4 h of immersion in extraction buffer. The extracted carcasses, processed and imaged using protocols standard for the taxon, were distinguishable from closely related species, and adequate as morphological vouchers. We provide links from the carcasses and DNA vouchers to image (MorphBank) and sequence (GenBank) databases.     

When Thailand was an island – the phylogeny and biogeography of mite harvestmen (Opiliones,Cyphophthalmi, Stylocellidae) in Southeast Asia

Aim To develop a comprehensive explanation for the biological diversity of Southeast Asia, especially in the Wallacea and Sundaland regions. This study focuses on a group of arachnids, mite harvestmen, which are thought to be an extremely old group of endemic animals that have been present in the region since most of its land supposedly formed part of the northern rim of the supercontinent Gondwana. Location Eastern Himalayas, Thai‐Malay Peninsula, Sumatra, Borneo, Java, Sulawesi, and New Guinea. Methods  Approximately 5.6 kb of sequence data were obtained from 110 South‐east Asian Cyphophthalmi specimens. Phylogenetic analyses were conducted under a variety of methods and analytical parameters, and the optimal tree was dated using calibration points derived from fossil data. Event based and paralogy‐free subtree biogeographical analyses were conducted. Results The Southeast Asian family Stylocellidae was recovered as monophyletic, arising on what is now the Thai‐Malay Peninsula and diversifying into three main clades. One clade (Meghalaya, here formally placed in Stylocellidae) expanded north as far as the eastern Himalayas, a second clade entered Borneo and later expanded back across the Sundaland Peninsula to Sumatra, and a third clade expanded out of Borneo into the entire lower part of Sundaland. Molecular dating suggested that Stylocellidae separated from other Cyphophthalmi 295 Ma and began diversifying 258 Ma, and the lineage that inhabits mostly Borneo today began diversifying between 175 and 150 Ma. Main conclusions The topology and molecular dating of our phylogenetic hypothesis suggest that Stylocellidae originated on Gondwana, arrived in Southeast Asia via the Cimmerian palaeocontinent, and subsequently diversified north, then south. Their present distribution in the Indo‐Malay Archipelago is explained largely by a diversification over the Sundaland Peninsula before western Sulawesi departed and the peninsula was extensively inundated.