Cupiennius salei and Achaearanea tepidariorum: Spider models for investigating evolution and development

The spiders Cupiennius salei and Achaearanea tepidariorum are firmly established laboratory models that have already contributed greatly to answering evolutionary developmental questions. Here we appraise why these animals are such useful models from phylogeny, natural history and embryogenesis to the tools available for their manipulation. We then review recent studies of axis formation, segmentation, appendage development and neurogenesis in these spiders and how this has contributed to understanding the evolution of these processes. Furthermore, we discuss the potential of comparisons of silk production between Cupiennius and Achaearanea to investigate the origins and diversification of this evolutionary innovation. We suggest that further comparisons between these two spiders and other chelicerates will prove useful for understanding the evolution of development in metazoans.     

Evolutionary crossroads in developmental biology: the spider Parasteatoda tepidariorum

Spiders belong to the chelicerates, which is an arthropod group that branches basally from myriapods, crustaceans and insects. Spiders are thus useful models with which to investigate whether aspects of development are ancestral or derived with respect to the arthropod common ancestor. Moreover, they serve as an important reference point for comparison with the development of other metazoans. Therefore, studies of spider development have made a major contribution to advancing our understanding of the evolution of development. Much of this knowledge has come from studies of the common house spider, Parasteatoda tepidariorum. Here, we describe how the growing number of experimental tools and resources available to study Parasteatoda development have provided novel insights into the evolution of developmental regulation and have furthered our understanding of metazoan body plan evolution.     

The T-box genes H15 and optomotor-blind in the spiders Cupiennius salei, Tegenaria atrica and Achaearanea tepidariorum and the dorsoventral axis of arthropod appendages

SUMMARY Dorsoventral axis formation in the legs of the fly Drosophila melanogaster requires the T-box genes optomotor-blind ( omb ) and H15 . Evolutionary conservation of the patterning functions of these genes is unclear, because data on H15 expression in the spider Cupiennius salei did not support a general role of H15 in ventral fate specification. However, H15 has a paralogous gene, midline ( mid ) in Drosophila and H15 duplicates are also present in Cupiennius and the millipede Glomeris marginata . H15 therefore seems to have been subject to gene duplication opening the possibility that the previous account on Cupiennius has overlooked one or several paralogs. We have studied omb - and H15 -related genes in two additional spider species, Tegenaria atrica and Achearanea tepidariorum and show that in both species one of the H15 genes belongs to a third group of spider H15 genes that has an expression pattern very similar to the H15 pattern in Drosophila . The expression patterns of all omb -related genes are also very similar to the omb expression pattern in Drosophila . These data suggest that the dorsoventral patterning functions of omb and H15 are conserved in the arthropods and that the previous conclusions were based on an incomplete data set in Cupiennius . Our results emphasize the importance of a broad taxon sampling in comparative studies.     

温室希蛛的生物学特性观察

温室希蛛Achaearanea tepidariorum在鲁东南沿海地区1年发生2代,但第2代不完整.越冬蜘蛛4月下旬出蜇,5月上旬开始产卵.卵期10 d,幼蛛期320 d,成蛛期76 d,越冬代成蛛寿命更长,雌雄性比为3∶1.成蛛日均食麦蛾4.9 头,是多种害虫的重要天敌.     

The effects of temperature on the web-building behaviour of the common house spider, Achaearanea tepidariorum

1. Because spiders are ectothermic animals, the temperature regime of the microhabitat in which an individual finds itself may affect important performance traits of that individual. The present study examined the effects of temperature on attributes of webs spun by Achaearanea tepidariorum (C. L. Koch), as well as testing temperature preference in this species. The effects of temperature on the amount of silk per web produced by Achaearanea tepidariorum and the prey-capture efficiency of webs produced at different temperatures were determined by using webs constructed at 5, 10, 15, 20, 25 and 30°C. The temperature preferences of A. tepidariorum within a thermal gradient were also determined.
2. Web mass was related to temperature, exhibiting a quadratic relation with a maximum web mass occurring at approximately 20°C.
3. Number of strands per cm³ of webs varied directly with web mass; webs with greater strand densities were more efficient at capturing flies.
4. The number of spiders observed in each temperature range in the thermal gradient indicated a non-uniform distribution, with the spiders avoiding temperatures in the highest range (27·3±2·0°C).
5. These data suggest an optimal temperature for web construction at which webs produced are more efficient at capturing prey. The data also suggest that this species may avoid sites that do not provide an adequate thermal environment.     

Fine Structural Analysis of the Central Nervous System in the Spider, Achaearanea tepidariorum (Theridiidae: Araneae)

ABSTRACT Central nervous system (CNS) of arachnids is still mysterious and has a rich unexplored field compare to what is known in insects or crustaceans. The CNS of the spider, Achaearanea tepidariorum, consists of a dorsal brain or supraesophageal ganglion and circumesophageal connectives joining it to the subesophageal mass. As the segmentation of the arachnid brain is still under discussion, we classify the brain as a protocerebral and tritocerebral ganglion depending on the evidences which generally accepted. The subesophageal nerve mass underneath the brain is the foremost part of the ventral nerve cord. All of this nerve mass is totally fused together, and forming subesophageal ganglia in this spider. In the brain, the nerve cells are packed in the frontal, dorsal and lateral areas, but are not absent from the posterior and ventral regions. In addition, the nerve cells of the subesophageal and abdominal ganglia are only restricted to the ventral and ventolateral regions. The CNS of the spider, Achaearanea tepidariorum is similar in feature to the Family Araneidae.     

Post-embryonic development of sheepshead minnow <Emphasis Type="Italic">Cyprinodon variegatus</Emphasis>: a staging tool based on externally visible anatomical traits

The sheepshead minnow Cyprinodon variegatus has become a favoured model for laboratory studies because of their small size, rapid development, and tolerance of laboratory conditions. Here, we analyse sheepshead minnow post-embryonic development with the goal of providing a generally useful method for staging fish after embryogenesis. Groups of three females and two males were placed in breeding chambers designed for this experiment. More than 100 eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope and placed in incubation dishes (50 per dish) at 26 °C. On day six, embryos hatched and larvae were transferred to 1 L beakers. To define a simplified normalization table for sheepshead minnow development, we measured each fish for its standard length and examined the fish for four externally evident traits: pigmentation pattern, caudal fin morphology, anal fin morphology, and dorsal fin morphology. The four traits were chosen, because they are easily visualized with standard laboratory equipment such as the stereomicroscope and camera. We have provided criteria for staging sheepshead minnows in studies of post-embryonic development. Our data suggest that dorsal and anal fin morphology may serve as a useful phenotype for defining metamorphic climax stages throughout post-embryonic development in C. variegatus. The staging systems we propose should facilitate detailed anatomical and developmental analyses in relation to ecotoxicological studies on potential disruption of the thyroid axis by xenobiotics and endocrine-disrupting compounds.     

Seasonal life cycle of Zatypota albicoxa (Hymenoptera: Ichneumonidae), an ectoparasitoid of Achaearanea tepidariorum (Araneae: Theridiidae), in northern Japan

The seasonal life cycle of Zatypota albicoxa (Walker, 1874), a koinobiont ectoparasitoid of the house spider, Achaearanea tepidariorum, was examined at Hirosaki (40°36′N), Japan. In winter, larvae were found on the abdomen of host spiders. They grew rapidly, emerged as adults in mid‐May, and reproduced shortly after emergence. The seasonal occurrence of the developmental stages in the field indicated that this parasitoid is multivoltine in Aomori Prefecture.     

Diapause and seasonal life cycle strategy in the house spider, Achaearanea tepidariorum (Araneae, Theridiidae)

Abstract In order to elucidate the mechanism regulating its seasonal life cycle, the photoperiodic response of Achaearanea tepidariorum has been analysed. Nymphal development was faster in long-day and slower in short-day photoperiods. The combined action of low temperature, poor food supply and short daylength induced diapause at an earlier developmental stage than short days alone. Thus, photoperiod is a primary factor inducing nymphal diapause, but the diapausing instar is influenced by both temperature and food supply. Hibernating nymphs became unresponsive to photoperiod in late December. After hibernation, however, sensitivity was restored and the nymphs remained sensitive to photoperiod throughout their life. This spider could also enter an imaginal or reproductive diapause. Photoperiod was again a primary inducing factor and temperature modified the photoperiodic response to some extent. The induction of the reproductive diapause was almost temperature-compensated whereas development was not. So the involvement of a photoperiodic counter system was suggested. Irrespective of whether the nymph had experienced diapause or not, the imaginal diapause was induced in response to a short-day photoperiod after adult moult. Based on these observations, the seasonal life cycle and the adaptive significance of nymphal and imaginal diapause are discussed.     

Real‐time imaging and genetic dissection of host–microbe interactions in zebrafish

Many aspects of host interactions with microbes can only be studied in the context of a whole organism. The zebrafish as a model organism has shown to be highly successful for studies of infection biology and the interactions of commensal microbiota with their hosts. Zebrafish are transparent during embryo and larval development and these early life stages are optimally suited for high‐resolution imaging of host–microbe interactions in a vertebrate organism. This is facilitated by the development of a variety of fluorescent reporter lines that mark different immune cell types or subcellular compartments where pathogens reside. The zebrafish is an excellent vertebrate model for forward genetic screening and efficient tools for gene knock‐down and targeted mutagenesis add further to the strength of this model organism. The use of zebrafish larvae for studying microbial infections has recently led to important new insights in host defence mechanisms, which are highlighted in this review focused on bacterial pathogens. Considering the highly conserved nature of the processes involved, including innate immune recognition, immunometabolism and autophagy, it is to be expected that these recent findings in zebrafish will have great translational value for biomedical applications.     

Embryonic and larval staging of summer flounder (Paralichthys dentatus)

Early development of flatfishes such as the summer flounder Paralichthys dentatus (Pleuronectiformes) has not been extensively documented, largely because of a dearth of material; however, the recent expansion of flatfish aquaculture has made embryos of P. dentatus readily available for developmental studies. We divide development of P. dentatus embryos and larvae into two main periods, pre- and posthatching, and assign stages within each of those primary divisions. Stages from fertilization to hatching loosely follow the general teleost staging scheme suggested by Shardo ([1995] J Morphol 225:125-167); stages from hatching through metamorphosis are aligned with the series used for Japanese flounder, P. olivaceus (Minami [1982] Nippon Suisan Gakkaishi 48:1581-1588; Fukuhara [1986] Nippon Suisan Gakkaishi 52:81-91). Although length, width, and age may serve as approximate indicators of developmental progression in summer flounder, these characteristics are too variable to form the sole basis of a staging table. Therefore, we define stages by morphological criteria drawn from the development of the jaw apparatus and digestive system, eye migration, and notochord tip flexion. Examination of these morphological features in hatched larvae allows accurate and consistent assessment of developmental stage despite variation in timing and size. The staging scheme for flounder embryonic and larval development presented here should facilitate both experimental and comparative research on summer flounder and other flatfish species.     

Embryogenic staging of fugu, Takifugu rubripes, and expression profiles of aldh1a2, aldh1a3 and cyp26a1

Fugu (Takifugu rubripes) has contributed as an ideal model organism for understanding the structure and evolution of vertebrate genomes, but also has potential as a good model organism for developmental biology because of the availability of the genome information. However, there is no comprehensive report describing the developmental stages, which is fundamental data for developmental biology. Here we describe a series of stages of the embryonic development of fugu during the first 8 days after fertilization, i.e. from fertilization to hatching. We define seven periods of embryogenesis – the zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and hatching periods. Stages subdividing these periods are defined based on morphological characteristics. In addition, as a model experiment of gene expression analysis using this staging series, we performed in situ hybridization of aldh1a2, aldh1a3 and cyp26a1 that play regulatory roles in retinoic acid (RA) metabolism essential for embryogenesis. This report provides fundamental information on fugu embryogenesis, which is anticipated to facilitate the use of fugu as a model organism for developmental studies.     

Phylogeny of the nematode genus <Emphasis Type="Italic">Pristionchus</Emphasis> and implications for biodiversity,biogeography and the evolution of hermaphroditism

Background  

The nematode Pristionchus pacificus has originally been developed as a satellite organism for comparison to Caenorhabditis elegans. A 10X coverage of the whole genome of P. pacificus is available, making P. pacificus the first non- Caenorhabditis nematode with a fully sequenced genome. The macroevolutionary comparison between P. pacificus and C. elegans has been complemented by microevolutionary studies of closely related strains and species within the genus Pristionchus. In addition, new understanding of the biology of Pristionchus from field studies, demonstrating a close association with various scarab beetles and the Colorado potato beetle, supports consideration of this nematode in studies of ecosystems. In the course of field studies on four continents more than 1,200 isolates were established from 15,000 beetle specimens representing 18 Pristionchus species. Two remarkable features of the Pristionchus – beetle association are the high species specificity of the interaction and the interception of the beetle's sex communication system for host recognition by the nematodes, as suggested by chemotaxis studies. Evolutionary interpretations of differences in developmental, behavioral and ecological patterns require a phylogenetic framework of the genus Pristionchus.     

Evolutionary Relationship between Diapause and Cold Hardiness in the House Spider,Achaearanea tepidariorum (Araneae: Theridiidae)

The relationship between diapause and cold hardiness of the house spider, Achaearanea tepidariorum, differed geographically. In a cool-temperate population, enhanced chilling tolerance and supercooling ability were observed in diapause individuals, whereas a subtropical population showed only chilling tolerance. Because this spider is considered to be of tropical origin, it would follow that the ancestral diapause of this spider was equipped with chilling tolerance, but not with an increased supercooling ability. It seems that the ability to lower the supercooling point evolved through natural selection in the course of expansion of this species to the northern climates. Copyright 1997 Elsevier Science Ltd. All rights reserved     

Worm Phenotype Ontology: Integrating phenotype data within and beyond the <Emphasis Type="Italic">C. elegans</Emphasis> community

Background  

Caenorhabditis elegans gene-based phenotype information dates back to the 1970's, beginning with Sydney Brenner and the characterization of behavioral and morphological mutant alleles via classical genetics in order to understand nervous system function. Since then C. elegans has become an important genetic model system for the study of basic biological and biomedical principles, largely through the use of phenotype analysis. Because of the growth of C. elegans as a genetically tractable model organism and the development of large-scale analyses, there has been a significant increase of phenotype data that needs to be managed and made accessible to the research community. To do so, a standardized vocabulary is necessary to integrate phenotype data from diverse sources, permit integration with other data types and render the data in a computable form.