Primitive Spider Research Articles

Diversity of Mygalomorph Spiders (Aranae: Opisthothelae) in India

A checklist of mygalomorph spiders recorded upto August, 2020 from different states and union territories of India was prepared. A total of 118 species under 31 genera belonging to 8 families are observed to be distributed in 23 states and 4 union territories of India. These primitive spiders are yet to be discovered in Haryana, Madhya Pradesh, Nagaland, Rajasthan, Delhi, Ladakh, Lakshdweep, Daman and Diu. Maximum diversity of these primitive spiders was reported in Tamil Nadu followed by Maharashtra, Kerala and West Bengal. More than 80% of the species of mygalomorph spiders recorded in India were reported from coastal states and union territories. Among the families, more than half (55.5%) of the species diversity can be seen in Theraphosidae (65 species in 13 genera) which were recorded from 23 states and 3 union territories followed by Idiopidae which is distributed in 13 states. More than 90% of known mygalomorph spiders from India are endemic.

The ultrastructure of the book lungs of the Italian trap-door spider Cteniza sp. (Araneae, Mygalomorphae, Ctenizidae)

The fine structure of book lungs is not homogeneous across Arachnids and is considered phylogenetically informative, however few reports on the ultrastructural features of this organ have been published. In this study, we examined the general morphology and ultrastructure of adult spiders of the genus Cteniza. The respiratory system of Cteniza sp. consists of two pairs of well-developed book lungs, which is considered indicative of primitive spiders. The general organization of the book lungs is similar to that described for other arachnids and consists of leaves of alternating air and hemolymph channels. The air channels are lined with cuticle and open to an atrium that leads to a slit-like spiracle. The air channels are held open by cuticular trabeculae. The space holders in the hemolymph channels are pillar trabeculae formed by two cells from the opposed walls. The pillar cells have a complex ultrastructure that includes an interdigitating connection, gap junctions, microtubules and hemidesmosomes. These features apparently help strengthen the pillar cells and their interconnections with each other and the underlying cuticle. The cytoskeleton resembles that of arthropod tendon cells where substantial structural support is needed.

Appendage patterning in the South American bird spider Acanthoscurria geniculata (Araneae: Mygalomorphae)

Pattern formation by the genes dachshund (dac), Distal-less (Dll), extradenticle (exd) and homothorax (hth) in spider appendages has been studied previously only in members of the higher spiders (Araneomorphae). In order to study the diversity and conservation of pattern formation in spiders as a whole, we studied homologs of these genes in embryos of the bird spider Acanthoscurria geniculata, which belongs to the Mygalomorphae, a more primitive spider group. We show that the patterns of dac and Dll are largely conserved in all spiders studied so far. We find a duplication of hth and exd genes as previously identified in the higher spider Cupiennius salei. These data suggest that pattern formation shows little diversity in all spiders, including the duplication of hth and exd that likely occurred before the split of Mygalomorphae and Araneomorphae. We also find that the legs and pedipalps bear endites of which only the pedipalpal endite expresses Dll and is retained in the adult. Similarly, the limb buds of the posterior spinnerets express Dll and become segmented appendages in the adult, whereas the anterior spinnerets lack Dll expression and are absent in postembryonic stages. In both cases, the expression of Dll or the lack of it indicates structures which will be retained as adult traits or rudimentary structures that degenerate, respectively. The presence of embryonic rudiments of leg endites in Acanthoscurria and the leg-like pattern formation in the posterior spinnerets are interpreted as primitive traits that have been lost in the Araneomorphae.

Spermatozoa and spermiogenesis of Liphistius cf. phuketensis (Mesothelae, Araneae, Arachnida) with notes on phylogenetic implications

The present study deals with the spermatozoa and spermiogenesis of Liphistius cf. phuketensis, a representative of the most primitive and enigmatic spider group Mesothelae. The general organization of the spermatozoa is very similar to the condition known from Amblypygi supporting a sister-group relationship between Araneae and Amblypygi. Besides plesiomorphic characters such as, e.g., an elongated and corkscrew shaped nucleus, the sperm cells are characterized by several apomorphic characters, e.g., the giant body and conspicuous membranous areas which are formed at the end of spermiogenesis. As the transfer form, coenospermia are formed at the end of spermiogenesis, which strongly supports the idea that this type of sperm aggregation is the primitive transfer form within spiders. A very remarkable character of the spermatozoa of some groups of arachnids is the coiling of the main cell organelles at the end of spermiogenesis. Previously, the Mesothelae were believed to be the only spider group which does not show a complete coiling of the main cell organelles. With the present study the first evidence of a complete coiling of spermatozoa within this primitive spider group could be documented, indicating that this character is part of the ground pattern of spider spermatozoa. Consequently, the incomplete coiling seems to be a synapomorphy of certain species of Mesothelae, which sheds new light on the discussion of the phylogenetic relationships of this group.

The distribution of purse‐web Atypus spiders (Araneae: Mygalomorphae) in central Europe is constrained by microclimatic continentality and soil compactness

AbstractAim Three species of primitive spiders of the genus Atypus occur in European xerothermic habitats, where they live in burrows. The aim of this study is to explain their distribution by investigating environmental variables at sites where they occur in central Europe.Location Over 50 sites in central Europe, Czech Republic.Methods Data on climatic, edaphic and vegetational parameters were collected from more than 50 sites. Phytocenological data were processed using Ellenberg's indicator values.Results Atypus muralis was found to occur almost exclusively in dry grassland (Festucion valesiacae), exposed to a continental microclimate. Atypus affinis usually occurred in dry sparse forests (Genisto germanicae–Quercion) that provide an Atlantic microclimate. Atypus piceus occurred in dry grassland (Bromion erecti) or forest fringes (Geranion sanguinei) characterized by an intermediate microclimate. Atypus piceus and A. muralis were restricted to agglutinate calcareous soils.Main conclusions Our results show that Atypus species colonized sites with different continentality in central Europe. These differences correspond to differences among their probable glacial refugia. Atypus muralis and A. piceus occur in habitats with a markedly continental climate, and are restricted to calcareous agglutinate soils that more efficiently buffer temperature and humidity extremes. Habitats of A. muralis and A. piceus are threatened by overgrowth of vegetation after a recent decline in grazing and by the decalcification of the landscape. However, habitats of A. affinis are stable in the present central European climate.

HANGING ON BY A THREAD

![Figure][1] Some 225 million years ago, the first spider webs appeared on the scene. The cribellar threads that primitive spiders use to spin their webs are composed of looped fibrils tangled into a mass \`a bit like 3D Velcro' explains Brent Opell, an evolutionary biologist at Virginia

Tubuliform silk protein: A protein with unique molecular characteristics and mechanical properties in the spider silk fibroin family

Orb–web weavers can produce up to six different types of silk and a glue for various functions. Tubuliform silk is unique among them due to its distinct amino acid composition, specific time of production, and atypical mechanical properties. To study the protein composing this silk, tubuliform gland cDNA libraries were constructed from three orb–weaving spiders Argiope aurantia, Araneus gemmoides, and Nephila clavipes. Amino acid composition comparison between the predicted tubuliform silk protein sequence (TuSp1) and the corresponding gland protein confirms that TuSp1 is the major component in tubuliform gland in three spiders. Sequence analysis suggests that TuSp1 shares no significant similarity with its paralogues, while it has conserved sequence motifs with the most primitive spider, Euagrus chisoseus silk protein. The presence of large side-chain amino acids in TuSp1 sequence is consistent with the frustrated β-sheet crystalline structure of tubuliform silk observed in transmission electron microscopy. Repeat unit comparison within species as well as among three spiders exhibits high sequence conservation. Parsimony analysis based on carboxy terminal sequence shows that Argiope and Araneus are more closely related than either is to Nephila which is consistent with phylogenetic analysis based on morphological evidence.

Hemocyanin Subunits of a Whipscorpion, Typopeltis crucifer, and a Primitive Spider, Heptathela kimurai: Orthologous Hemocyanin Subunits in Arachnids

The presence of monomer and dimer subunits was revealed, by means of native polyacryl-amide gel electrophoresis (PAGE), in examined arachnid hemocyanins. We determined the N-terminal amino acid sequences of nine monomer subunits prepared from hemolymph of a whipscorpion, Typopeltis crucifer, and a primitive spider, Heptathela kimurai, and two constituent monomers of a dimer subunit from the whipscorpion. Based on a comparison of the sequences, we confirmed that the orthologous hemocyanin subunits are shared between the whipscorpion and the scorpion, Liocheles australasiae, between the primitive spider and the scorpion, and among the whipscorpion, the scorpion, and mygalomorph spiders. This study is the first to demonstrate the presence of orthologus hemocyanin subunits in different orders. Furthermore, it is evident that one of the constituent monomers of the hemocyanin dimer from the whipscorpion is orthologous to the constituent monomers (the group G subunits) of the hemocyanin dimers in mygalomorph spiders and to the subunit LA8 (a constituent monomer of a dimer subunit) of the scorpion, suggesting that these constituent monomers of arachnid hemocyanin dimers originated from a common ancestral gene which existed in a common ancestor of these arachnids.

The reproductive behaviour of the Tasmanian cave spider Hickmania troglodytes (Araneae: Austrochilidae)

Abstract Hickmania troglodytes, the Tasmanian cave spider, belongs to a relict group with a scattered world distribution, and is of both phylogenetic and zoogeographic interest. It belongs to the superfamily Austrochiloidea (infra‐order Araneomorphae) and shares characteristics with more advanced araneomorphs and primitive spiders in the infra‐orders Liphistiomorphae and Mygalomorphae. The reproductive behaviour of H. troglodytes (including courtship, mating, egg‐sac construction, brooding, emergence, and moulting behaviour) is described, providing the first such account for any member of the Austrochiloidea. Courtship in H. troglodytes is ritualized and involves distinct communicatory gestures (beating with the legs) by the male to identify and protect himself. Males use a pronounced curve in the metatarsus of the second leg to immobilize females during mating; this curve closely matches the contours of the female's cheliceral region. Both courtship and mating are protracted and each can last for over 5.5 h. The egg‐sac is large and unusual, with a rigid internal structure that separates the egg mass from the silk walls, while the silk itself seems to be exceptionally resistant to fungal degradation. The young emerge from the egg‐sac 8–10 months after laying, a period significantly longer than the typical emergence time of araneomorph spiders (4–8 weeks). It is suggested that the rigid internal structure and the silk of the egg‐sacs may help to buffer and protect the eggs and young from biotic and abiotic factors during this extended pre‐emergence period.

Insect Attraction to Ultraviolet‐Reflecting Spider Webs and Web Decorations

The foraging performance of any predator is dependent on its ability to locate prey. All spiders produce silks and many locate insects by producing silk traps. We measured the reflective properties of silk produced by primitive, non—web—weaving spiders and derived aerial web spinners. We found that primitive spiders produce silks that reflect ultraviolet (UV) light and primitive aerial web weavers spin UV—reflecting catching silks that attract Drosophila. Derived, web—spinning spiders in the genus Argiope, however, produce catching silks that exhibit low reflectivity in the UV and, in fact, reflect little light at all. Nevertheless, Argiope decorate their webs with bright, UV—reflecting bars and crosses that attract prey. We found that more insects were intercepted per hour by decorated webs with spiders than by undercorated webs from which the spider had been removed. In addition, within—web analyses showed that when only half of a web was decorated, more insects were intercepted by the decorated halves than the undecorated web halves. We propose that UV—reflecting decorative silks, together with the UV—reflecting body surfaces of A. argentata, act as a visual display that attracts prey.

Ultrastructural characterization of the sex chromosomes during spermatogenesis of spiders having holocentric chromosomes and a long diffuse stage.

An ultrastructural study has been made of spermatogenesis in two species of primitive spiders having holocentric chromosomes (Dysdera crocata, male X0 and Sergestria florentia X1X2O). Analysis of the meiotic prophase shows a scarcity or absence of typical leptotene to pachytene stages. Only in D. crocata have synaptonemal complex (SC) remnants been seen, and these occurred in nuclei with an extreme chromatin decondensation. In both species typical early prophase stages have been replaced by nuclei lacking SC and with their chromatin almost completely decondensed, constituting a long and well-defined diffuse stage. Only nucleoli and the condensed sex chromosomes can be identified. - In S. florentina paired non-homologous sex chromosomes lack a junction lamina and thus clearly differ from the sex chromosomes of more evolved spiders with an X1X20 male sex determination mechanism. In the same species, sex chromosomes can be recognized during metaphase I due to their special structural details, while in D. crocata the X chromosome is not distinguishable from the autosomes at this stage. - The diffuse stage and particularly the structural characteristics of the sex chromosomes during meiotic prophase are reviewed and discussed in relation to the meiotic process in other arachnid goups.

II popolamento di ragni nelle grotte tropicali (Araneae)

The so called “tropical” caves (most of which are also geographically “tropical”) are distinguished from the “temperate” caves by the much larger trophic resources. Spiders are common in both kinds of caves, but the groups present in one kind are mostly absent in the other (notwithstanding that many families are distributed over at least one temperate and one tropical region). As in all temperate caves more or less the same groups of spiders can be found, so the tropical caves have a typical spider fauna, composed of different groups (often also more than those present in the temperate caves). In the temperate caves the most typical groups are the Leptonetidae, the Dysderidae, many Araneoidea and some Agelenidae; these groups are either absent or rare in the tropical caves. In these the typical groups are some Orthognatha and many primitive spiders of the Haplogynae (Oonopidae, Tetrablemmidae, Ochyroceratidae, Scytodidae, Pholcidae, Telemidae) with a few Araneoidea (Theridiosomatidae and Symphytognathidae). From an ecological point of view, the detriticolous groups are not common in temperate caves, but are exceedingly common in tropical caves. In these live also often some groups which could be considered not strictly detriticolous, but more exactly “microcavernicolous” (i.e. living “normally” in more or less permanent crevices etc. of soil and rocks). In temperate caves are on the other hand more common groups living typically on vegetation, not very close to the soil. Ethologically, in tropical caves the existence of groups is possible which either ambush their prey or search for it actively whereas most spiders of temperate caves capture it with a web.

Notes on the Development of a Trap-door Spider, Ummidia fragaria (DOENITZ)

1. The embryonic and the early post-embryonic development of Ummidis fragaria (Ctenizidae) was studied on preserved and living materials.2. The embryonic development of Ummidia closely resembles that of other mygalomorphs.3. In about three weeks the eggs hatch and the prelarvae emerge. About two days after hatching they take the first molt and become the larvae. The larval stage lasts about four weeks and the larvae transform into the protonymphs. The early postembryonic development of Ummidia is very similar to that of Ischnothele (Dipluridae).4. In Ctenizidae, Dipluridae and Theraphosidae the larval stage consists of two phases: pL, L or L, pN, whereas in Atypidae only one phase, L. In the primitive spider, Heptathela also the larval stage is only one phase, L. From a point of view of comparative embryology, therefore, the Atypidae may be the most primitive among the mygalomorph spiders.

Control of Drag-Line Spinning in Certain Spiders

Synopsis. Araneomorph spiders from many different families show some regional differentiation of the duct which carries the drag-line silk, but only in the orb-web spiders is there a well-defined control valve. This valve, and its associated muscles, is described for Araneus diadematus (Argiopidae), an ecribellate spider, and is compared with that found in Uloborus octonarius (Uloboridae), a cribellate spider. It is suggested that the remarkable similarity between the valves in these two groups implies evolutionary convergence. Some evidence is presented which suggests that variations in body pressure are used to control the drag-line spinning, at least in the more primitive Araneomorphs. The drag-line plays a very important part in the life of a spider, ranging from a simple lifeline in the Salticids to a fundamental part of the complex web in the Argiopids. Its function is sometimes less clear in the more primitive spiders, for instance in the Gnaphosids and Clubionids which are typically nocturnal hunters, but even with these it may be a safety device. Spiders are a very varied group, and one might, therefore, expect to find equally varied uses for the drag-line in the different families, and even between the species