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Lynelle Staudt
Pseudoscorpions are generally beneficial to humans since they prey on clothes moth larvae, carpet beetle larvae, booklice, ants, mites, and small flies. They are tiny, and are rarely noticed due to their small size, despite being common in many environments. When people do see pseudoscorpions, especially indoors, they are often mistaken for ticks or small spiders.[citation needed] Pseudoscorpions often carry out phoresis, a form of commensalism in which one organism uses another for the purpose of transport.
A pseudoscorpion has eight legs with five to seven segments each; the number of fused segments is used to distinguish families and genera. They have two very long pedipalps with palpal chelae (pincers), which strongly resemble the pincers found on a scorpion.
The pedipalps generally consist of an immobile "hand" and mobile "finger", the latter controlled by an adductor muscle. Members of the clade Iocheirata, which contains the majority of pseudoscorpions, are venomous, with a venom gland and duct usually located in the mobile finger; the venom is used to immobilize the pseudoscorpion's prey. During digestion, pseudoscorpions exude a mildly corrosive fluid over the prey, then ingest the liquefied remains.
More than 3,300 species of pseudoscorpions are recorded in more than 430 genera, with more being discovered on a regular basis. They range worldwide, even in temperate to cold regions such as Northern Ontario and above the timberline in Wyoming's Rocky Mountains in the United States and the Jenolan Caves of Australia, but have their most dense and diverse populations in the tropics and subtropics, where they spread even to island territories such as the Canary Islands, where around 25 endemic species have been found.[21] There are also two endemic species on the Maltese Islands.[2] Species have been found under tree bark, in leaf and pine litter, in soil, in tree hollows, under stones, in caves such as the Movile Cave, at the seashore in the intertidal zone, and within fractured rocks.[3][22]
The oldest known fossil pseudoscorpion, Dracochela deprehendor is known from cuticle fragments of nymphs found in the Panther Mountain Formation near Gilboa in New York, dating to the mid-Devonian, around 383 million years ago.[23] It has all of the traits of a modern pseudoscorpion, indicating that the order evolved very early in the history of land animals.[24] Its morphology suggests that it is more primitive than any living pseudoscorpion.[25] As with most other arachnid orders, the pseudoscorpions have changed very little since they first appeared, retaining almost all the features of their original form. After the Devonian fossils, almost no other fossils of pseudoscorpions are known for over 250 million years until Cretaceous fossils in amber, all belonging to modern families, suggesting that the major diversification of pseudoscorpions had already taken place by this time.[26] The only fossil from this time gap is Archaeofeaella from the Triassic of Ukraine, approximately 227 million years ago, which is suggested to be an early relative of the family Feaellidae.[27]
The house pseudoscorpion adult is 3 to 4 millimeters in length and has a rich mahogany color. Its four pairs of legs increase sequentially in length. It has one eye on each side of its cephalothorax (head plus thorax) and a 12-segment abdomen (only ten are easily visible). Overall, the body resembles a teardrop. The pedipalps, located in front of the first pair of legs, are more than twice as long as the legs. When extended, crab-like, they measure 7 to 9 millimeters across.
The female produces 20 to 40 eggs that she carries beneath her abdomen. After the young house pseudoscorpions, which look like small adults, emerge, they stay with the female for several days, sometimes riding on her back. The entire brood then disperses. This process, from egg deposit to brood dispersal, can take 3 weeks.
The young house pseudoscorpions molt three times before adulthood; these stages are protonymph, deutonymph, and tritonymph. The developmental period is temperature dependent and takes 10 to 24 months. Adults do not molt and can live for 3 or 4 years.
Older house pseudoscorpions are less agile. They often have difficulty climbing smooth surfaces and are less likely to right themselves after flipping onto their backs. These factors, plus their increased visibility due to their large size, may explain why only adult specimens are submitted for identification.
Peudoscorpions pose no hazards for homeowners. Their presence may diagnose a high level of atmospheric humidity and/or a population of other arthropods, on which the pseudoscorpions are feeding. Using pesticides to control these animals is not recommended.
The Yosemite Cave Pseudoscorpion is blind, possessing no posterior eyes and lacking the typical tapetum, the layer of reflective tissue that is present on the back of the eye. The new species also presents an atypical color, which is a tan/amber with reddish-brown legs. The cave-adapted Yosemite Cave Pseudoscorpion differs from other pseudoscorpions due to its loss of eyes and its elongated palp, the pincer like feature on the front two legs of scorpions and pseudoscorpions.
"We are thrilled about the new discovery of this fascinating species. Yosemite National Park is one of the great laboratories of the natural world and finds like this are incredibly exciting," said Niki Nicholas, former chief of Resources Management and Science at Yosemite. "We will continue to study the pseudoscorpion, as well as look for other new species of flora and fauna."
The pseudoscorpion is known as a troglobite, a small cave-dwelling animal that has adapted to a dark environment. Such species typically include spiders, insects, and fish. Most troglobites live permanently underground and cannot survive outside of their cave environment. Sixteen other pseudoscorpion species of the genus Parobisium exist, all from the Northern hemisphere--including the United States, China, Japan, and South Korea. The Yosemite Cave Pseudoscorpion is believed to be only the second troglobite (first was in central Texas) connected to granite talus caves in North America.
This discovery will further inspire biologists to explore regions of the park not traditionally sampled for new fauna. For example, biologists typically investigate limestone and marble caves for new species, rather than talus caves. Additionally, biologists in Yosemite have made it a top priority to continue further research into the park's talus cave ecosystem to learn more about these relatively unexplored areas thought to house additional pseudoscorpion species.
The Tooth Cave pseudoscorpion (Tartarocreagris texana) resembles a tiny, tailless scorpion. Pseudoscorpions lack a stinger and are harmless to humans. They use their pincers to prey on small insects and other arthropods. The Tooth Cave pseudoscorpion is eyeless and troglobitic, meaning that they are adapted to and only live underground. Its habitat includes caves and other small openings in karst limestone, which are landforms and subsurface features like sinkholes and caves, that are produced by dissolution of bedrock. Although it lives underground, Tooth Cave pseudoscorpion are dependent on the quality of the water and nutrients from surface-level habitats.
Known to live in only a handful of caves or karst features in western Travis County, Texas, this species is endangered due to habitat destruction, degradation and fragmentation that result from urban development. The karst habitats inhabited by this species, and the ecosystems on which it depends, have evolved slowly over millions of years and cannot be recreated once they have been destroyed. Thus, the conservation and recovery of the Tooth Cave pseudoscorpion depends upon the long-term management and protection of the surface and subsurface habitat where it lives. We are working with private landowners and local, city and county governments to identify, preserve and manage these areas.
A large clade of pseudoscorpions (Iocheirata) possess one or two venom glands within the pedipalpal fingers (used to immobilize their prey); venom glands are missing in the less diverse superfamilies Feaelloidea and Chthonioidea [2,10]. They therefore represent one of the four venomous arachnid orders (together with Acari [ticks], Araneae [spiders], and Scorpiones [scorpions]). Surprisingly, and in contrast to the remaining venomous arachnid groups, the composition of pseudoscorpion venom remains unknown. Santos et al. [11] studied the effect of the crude venom from Paratemnoides elongatus on a rat cerebral cortex. Their findings were suggestive of the presence of selective compounds (e.g., neurotoxins) acting in l-glu and GABA dynamics, but no specific compounds were reported.
(a) Habitat of Synsphyronus apimelus in the Stirling Range National Park, Western Australia (photo by A.Z.O.). (b) Live habitus of adult Synsphyronus apimelus (photograph by G. Giribet, MCZ Database at ). (c) Schematic drawings showing the position of the venom glands in the pedipalpal chela of selected families of Iocheirata (the venomous pseudoscorpions), after References [22,23].
(a) Distribution of the annotated transcripts from the venom gland transcriptome of S. apimelus according to protein families and subfamilies. (b) Ortholog hit ratio (OHR) analysis showing the median (white line), and quartiles for three pseudoscorpion species. (c) Comparative distribution of the annotated transcripts from the transcriptomes of S. apimelus, H. kraepelini, and Hesperochernes sp.
Low molecular mass spider toxins were poorly represented (in terms of diversity) in the three transcriptome libraries. Our phylogenetic analyses of U8-agatoxin-like peptides (ML and BI; Figure 4a) show the presence of three orthogroups, consisting of sequences from the three pseudoscorpion species. From these, one pseudoscorpion orthogroup was recovered with a U8-agatoxin-like homolog peptide, originally reported from the genomic analysis of P. tepidariorum with low nodal support (green clade in Figure 4b). The other two groups were pseudoscorpion-specific (orange and gray clades in Figure 4b). Finally, five transcripts from S. apimelus (representing one gene and five isoforms) clustered with the U8-agatoxin-like peptide from C. sculpturatus and another sequence reported from Hemiscorpius lepturus. No specific transcripts from any of the pseudoscorpion libraries clustered with peptides reported from tick venom (light blue clade in Figure 4b).
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