Progradungula otwayensis | |
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P. otwayensis immature male shown holding its catching ladder and assuming a hunting posture | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Subphylum: | Chelicerata |
Class: | Arachnida |
Order: | Araneae |
Infraorder: | Araneomorphae |
Family: | Gradungulidae |
Genus: | Progradungula |
Species: | P. otwayensis |
Binomial name | |
Progradungula otwayensis Milledge, 1997 | |
Distribution map of P. otwayensis in the Great Otway National Park of Victoria, Australia. Red marks indicate localities for Michalik et al. (2013); black circles indicate localities given by Milledge (1997). |
Progradungula otwayensis, commonly known as the Otway odd-clawed spider, is a species of cribellate spider endemic to the Great Otway National Park of Victoria, Australia. It is one of only three species in the gradungulid genus Progradungula .
Odd-clawed spiders are medium-sized to large spiders, with an approximate body length of 10 to 15 mm (0.39 to 0.59 in) and a leg span of 72 to 77 mm (2.8 to 3.0 in). They are lightly pigmented, from yellowish brown to light mauvish gray, with three chevron markings on the rear upper part of their abdomen. Like other gradungulids, their legs are tipped with three claws. These claws are particularly well-developed on the first and second leg pairs and are used for latching unto prey. They are ambush predators, building characteristic ladder-shaped snares close to the ground. They stand head-down on these webs waiting for prey which they then scoop up into these webs to trap them.
Odd-clawed spiders were first described by the Australian arachnologist Graham A. Milledge in 1997. They are named after the Great Otway National Park, from where the type specimens were recovered. [1] [2] Milledge's specimens comprised only one adult male and several juveniles. The female was unknown until 2013 when the arachnologists Peter Michalik, Luis Piacentini, Elisabeth Lipke, and Martin J. Ramírez described an adult female for the first time. [1]
Progradungula otwayensis is one of only two species classified under the genus Progradungula . The other species being the very similar Carrai cave spider ( Progradungula carraiensis ). They can be distinguished from the latter by the presence of a single jutting structure (process) on the syringe-like copulatory organ (embolus) of the bulb on the male pedipalps, in contrast to two in Carrai cave spiders. Female odd-clawed spiders also have eight sperm receptacles (spermathecae) on their genitals (epigyne), in contrast to six in the Carrai cave spiders. [1] [3]
Progradungula otwayensis belongs to the family Gradungulidae, superfamily Austrochiloidea, and suborder Araneomorphae. [1] [2] [4]
The carapace (upper part of the cephalothorax) of females is 6.92 mm (0.272 in) and 4.66 mm (0.183 in) wide. It is widest between the second and third leg pairs. The sternum (lower part of the cephalothorax) is elongated and shield-shaped with a pointed tip at the rear ending at the midpoint of the fourth leg pair. The abdomen (opisthosoma) is 8.51 mm (0.335 in) long and 7.18 mm (0.283 in) wide. The first pair of legs is the longest at 40.30 mm (1.587 in), while the third pair is the shortest at 27.14 mm (1.069 in). The second and fourth pair of legs are around the same lengths, at 30.86 mm (1.215 in) and 32.46 mm (1.278 in) respectively. [1]
The males are smaller than the females, with a carapace about 5.42 mm (0.213 in) long and 3.98 mm (0.157 in) wide. The abdomen is relatively shorter than the carapace unlike in the females. It is about 5.40 mm (0.213 in) long and 3.98 mm (0.157 in) wide. As with the females, the first pair of legs is the longest at 37.89 mm (1.492 in), and the third pair the shortest at 24.89 mm (0.980 in). The second and fourth leg pairs are both around 30 mm (1.2 in) in length. [2]
The last segments of the legs (tarsi) in both males and females have three claws on the tips. Longest on the first two pairs of legs, and shorter on the rest. The hook-like and raptorial upper two claws (the superior claws) on the ends of the first two leg pairs are dissimilar from each other. They are complemented by dense forward facing bristles (setae) on the underside of the tarsus, which are particularly strongly developed on the first and second leg pair. The legs also possess a slightly asymmetrical pattern of spines. A short row of fine comb-like bristles (the calamistrum) is found on the second quarter of the second-to-the-last leg segments (metatarsi) of the fourth leg pair. [1]
Odd-clawed spiders have eight eyes arranged in two rows of four. The front row curves slightly backward, while the back row curves slightly forward. The anterior and posterior lateral (left and right) eyes are clustered closely together, while the median eyes are spaced further from each other. In females, the anterior and posterior lateral eyes are the largest pairs, with a diameter of 0.35 mm (0.014 in). The anterior median eyes are the smallest with a diameter of 0.23 mm (0.0091 in). The posterior median eyes are slightly smaller than the lateral eyes, at a diameter of 0.32 mm (0.013 in). In males, the anterior lateral eyes are the largest pair, with a diameter of 0.29 mm (0.011 in). Their posterior median eyes and posterior lateral eyes are about the same size, with a diameter of 0.25 mm (0.0098 in). As with the female, the anterior median eyes are the smallest pair, with a diameter of only 0.15 mm (0.0059 in). All of the eyes are white in colour, except for the anterior median eyes which are black. [1] [2]
The fang appendages (chelicerae) are strong and vertically oriented. They possess large forward facing teeth on the cheliceral groove, three in females and four in males, evenly spaced from each other. Very small backward facing teeth (denticles) are also present in a row on the basal half of the cheliceral groove, five in females and three to four in males. A spine is present on the upper side of the tip. Sound-producing ridges on the chelicerae (stridulatory organs) are absent in females but present in males. The chewing appendages (maxillae) are located immediately behind the chelicerae. They are strongly curved on the outside edges and tapers into a blunt tip. They possess serrated edges (serrulae) used to cut up prey. The lower lip (labium) which covers the mouth opening has an indentation at the tip. It is 0.83 mm (0.033 in) long and 0.87 mm (0.034 in) wide in females. In males, it is 0.69 mm (0.027 in) long and 0.85 mm (0.033 in) wide. [1] [2]
In life, odd-clawed spiders have a yellowish brown carapace, darker around the eye regions. The mouthparts are reddish brown. The sternum is reddish brown at the sides, paler in the middle. The legs are also yellowish brown. The abdomen is fawn coloured in females with three dark-brown chevron shaped markings on the rear half. In males, the abdomen is a light mauvish grey, with a pale stripe in the middle of the upper surface of the front half. In the rear half, they have three paler chevron shaped markings. [1] [2]
Odd-clawed spiders are endemic to the Great Otway National Park of Victoria, Australia. [1] [2] [5] They seem to prefer to build their webs near or in the hollows of myrtle beech ( Nothofagus cunninghamii ), particularly in very old trees which usually have extensive hollows. Webs have also been found near hollows in mountain ash ( Eucalyptus regnans ), the bases of tree ferns (Cyatheales), and even under bridges. Though in areas where old myrtle trees are abundant, these other habitats are much less inhabited. This may indicate that they are dependent on the microclimate of the myrtle beech hollows. [1] [2]
Odd-clawed spiders are nocturnal. During the day, they rest inside their retreats in the tree hollows. An hour or so after sunset, they emerge to build their webs or to hunt. [1] [2]
Along with Progradungula carraiensis and Macrogradungula moonya , odd-clawed spiders are one of the only three species belonging to the family Gradungulidae that are cribellate. [1] Unlike other members of the family which are all cursorial (active roving hunters), these three species are ambush predators that construct snares. [3] The snares are made from silk spun from specialized spinnerets known as the cribellum, and combed with the row of bristles (the calamistrum) on their fourth leg pair. Unlike normal spinnerets, the cribellum produces extremely fine silk that can easily entangle prey without the need for glue. [6] [7] The snares of all three species are distinctively ladder-shaped, in contrast to the snares of other cribellate spiders from other families. [3]
The larger part of the odd-clawed spider's web is composed of a network of supporting threads built up to 2 m (6.6 ft) above the ground. Two lateral support threads extend from this network and are attached to vegetation or ground below. These threads are held more or less parallel to each other by several short bridge threads. The spider spins the catching ladder in between them, composed of a loose irregular zigzag of cribellate thread. The catching ladder and the supporting webs are usually built far from the retreat of the spider in the tree hollows, as far as 3 m (9.8 ft) away. The retreat and the webs are connected to each other by a single sturdy thread. [1] [2] [3]
The prey-catching behaviour of odd-clawed spiders is similar to that of Progradungula carraiensis and Macrogradungula moonya. [1] [2] [7] The spider takes position on its catching ladder with its head facing downwards toward the substrate. In this position, its fangs are at about the same level as the lowest "rung" of the catching ladder. The third and fourth pair of legs are used to stretch and hold the catching ladder behind the spider. The first and second pair of legs are held outstretched in front of the spider, just above the ground level. The second pair of legs may touch, or at least is very close to, the lateral support threads. Through these threads, the spider senses vibrations coming from the ground. These vibrations (in addition to air currents) warn the spider of approaching prey. [3] [8]
When a prey animal is detected within the range of the spider, it lunges with its clawed front legs and scoops it up into the catching ladder, also administering a bite in the process. The catching ladder detaches from the lateral support threads and entangles the prey. Due to its elasticity, the cribellate threads can stretch to comfortably envelop even large prey. The spider restrains the enmeshed prey while continuing to inject it with venom. When the prey stops moving, the spider relaxes its hold, turns around on the web and begins wrapping the prey in silk. The catching ladder is destroyed during the capture and the spider may rebuild it during or even before feeding on the caught prey. [3] [8]
Odd-clawed spiders also have similar defensive behaviour as Progradungula carraiensis. [2] During low-level disturbances, they retreat towards the upper support webs or dismount towards the nearest surface. In greater threat levels, however, they immediately drop from their webs to the ground and "play dead" (thanatosis), assuming an inert posture with their legs tightly held against their bodies. [3] [8]
In contrast to adults and immature individuals, all the juveniles were observed to build their catching ladders and support webs inside the tree hollows. No catching ladders of juveniles have been found in the open. This seems to indicate that early instars of odd-clawed spiders live exclusively within the tree hollows. [1]
Due to their apparent dependence on myrtle beech trees (which explains their extremely limited distribution range), their survival is closely tied to the preservation of habitats where myrtle beech also occurs. [2] [6]
Jumping spiders are a group of spiders that constitute the family Salticidae. As of 2019, this family contained over 600 described genera and over 6,000 described species, making it the largest family of spiders at 13% of all species. Jumping spiders have some of the best vision among arthropods and use it in courtship, hunting, and navigation. Although they normally move unobtrusively and fairly slowly, most species are capable of very agile jumps, notably when hunting, but sometimes in response to sudden threats or crossing long gaps. Both their book lungs and tracheal system are well-developed, and they use both systems. Jumping spiders are generally recognized by their eye pattern. All jumping spiders have four pairs of eyes, with the anterior median pair being particularly large.
Solifugae is an order of arachnids known variously as solifuges, sun spiders, camel spiders, and wind scorpions. The order includes more than 1,000 described species in about 147 genera. Despite the common names, they are neither true scorpions nor true spiders. Because of this, it's less ambiguous to call them "solifuges". Most species of solifuge live in dry climates and feed opportunistically on ground-dwelling arthropods and other small animals. The largest species grow to a length of 12–15 cm (5–6 in), including legs. A number of urban legends exaggerate the size and speed of solifuges, and their potential danger to humans, which is negligible.
Crevice weaver spiders (Filistatidae) comprise cribellate spiders with features that have been regarded as "primitive" for araneomorph spiders. They are weavers of funnel or tube webs. The family contains 18 genera and more than 120 described species worldwide.
Austracantha is a genus of spider with a single species, Austracantha minax, commonly known as the jewel spider or the Christmas spider. It is a member of the family Araneidae and is endemic to Australia. They are relatively small spiders, reaching a maximum total body length of only around 12 mm (0.47 in) for females, and 5 mm (0.20 in) for males. Their abdomen has six distinctive projections ("spines") that makes them easy to identify. They are predominantly a shiny black, with variable white, yellow, and orange patterns. Melanistic forms also occur during autumn. They are facultatively gregarious, and can be found in large aggregations of overlapping orb webs. They feed on small flying insects that get entangled in their webs. They are harmless to humans, though the webs can be a nuisance for bushwalkers. They are most abundant during the summer months.
The zebra spider is a common jumping spider of the Northern Hemisphere. Their common name refers to their vivid black-and-white colouration, whilst their scientific name derives from Salticus from the Latin for “jump”, and the Greek scenicus, translating to “theatrical” or “of a decorative place,” in reference to the flashy, zebra-like coloration of the species.
Phidippus audax, the Bold jumper or Daring jumping spider, is a common species of spider belonging to the genus Phidippus, a group of jumping spiders easily identified by their large eyes and their iridescent chelicerae. Like all jumping spiders, they have excellent stereoscopic vision that aids them in stalking prey and facilitates visual communication with potential mates during courting. Bold jumping spiders are native to North America and have been introduced to Hawaii, Nicobar Islands, Azores, and the Netherlands. They are typically black with a distinct white triangle on their abdomen.
Cribellum literally means "little sieve", and in biology the term generally applies to anatomical structures in the form of tiny perforated plates.
Gradungulidae, also known as large-clawed spiders, is a spider family endemic to Australia and New Zealand. They are medium to large-sized haplogyne spiders with three claws and two pairs of book-lungs similar to Mygalomorphae. Some species build extensive webs with an upper retreat tangle and connecting threads to scaffolding. This supports the ladder-like catching platform that is glued to the ground. Progradungula, a large spider with long legs like Hickmania, and Macrogradungula are the only cribellate genera of the family.
Misumena vatia is a species of crab spider with a holarctic distribution. In North America, it is called the goldenrod crab spider or flower (crab) spider, as it is commonly found hunting in goldenrod sprays and milkweed plants. They are called crab spiders because of their unique ability to walk sideways as well as forwards and backwards. Both males and females of this species progress through several molts before reaching their adult sizes, though females must molt more to reach their larger size. Females can grow up to 10 mm (0.39 in) while males are quite small, reaching 5 mm (0.20 in) at most. Misumena vatia are usually yellow or white or a pattern of these two colors. They may also present with pale green or pink instead of yellow, again, in a pattern with white. They have the ability to change between these colors based on their surroundings through the molting process. They have a complex visual system, with eight eyes, that they rely on for prey capture and for their color-changing abilities. Sometimes, if Misumena vatia consumes colored prey, the spider itself will take on that color.
Uloborus walckenaerius, also known as the feather-legged spider, is a cribellate spider in the family Uloboridae. Like all spiders in this family, they do not have venom glands and immobilize their prey with over 140 metres of thread. They are named in honor of Charles Athanase Walckenaer.
Hickmania is a monotypic genus of Australian cribellate araneomorph spiders in the family Gradungulidae, containing only the Tasmanian cave spider. The genus was first described by Willis J. Gertsch in 1958, and has been found only in Tasmania. It is the last of an old Gondwanan lineage, long since separated from its closest relatives in South America. It is an icon species for faunal conservation in Tasmania, and is named in honor of V. V. Hickman, a professor at the University of Tasmania, who specialized in spiders. The species name is derived from the Ancient Greek τρωγλοδύτης (troglodytes), meaning "cave-dweller".
Progradungula carraiensis, or the Carrai cave spider, is a cribellate spider found only in the moist forests and limestone caves of the Carrai Plateau in northern New South Wales. It is one of only two species in the gradungulid genus Progradungula.
Progradungula is a genus of Australian large-clawed spiders that was first described by Raymond Robert Forster and Michael R. Gray in 1979. As of May 2024 it contains only three species: P. barringtonensis, P. carraiensis and P. otwayensis.
Oecobius navus is a small cosmopolitan cribellate spider species found across the world.
The anatomy of spiders includes many characteristics shared with other arachnids. These characteristics include bodies divided into two tagmata, eight jointed legs, no wings or antennae, the presence of chelicerae and pedipalps, simple eyes, and an exoskeleton, which is periodically shed.
Titanoeca quadriguttata is a species of spider in the family Titanoecidae. It is widespread in Europe, though absent from Great Britain, and is found in Austria, Belgium, Bulgaria, Corsica, Croatia, Czech Republic, France, Germany, Greece, Hungary, Italy, Liechtenstein, Moldova, Russia, Slovakia, Spain, Switzerland, the Netherlands, Ukraine.
This glossary describes the terms used in formal descriptions of spiders; where applicable these terms are used in describing other arachnids.
Hyptiotes paradoxus, also known as the triangle spider, is a cribellate orbweaver in the family Uloboridae.
Urogelides is a genus of jumping spiders containing one described species, Urogelides daviesae, and other undescribed species. It was first described by Marek Michał Żabka in 2009, and is found in Queensland, Australia.
Tetragnatha versicolor is a species of long-jawed orb weaver in the spider family Tetragnathidae. It is found throughout North America, Canada, Central America, and Cuba, but are most common in the United States. T. versicolor is heavily concentrated in New England and the west coast in states like California and Washington. T. versicolor is considered a habitat generalist, and can thrive in many different environments. While they can be found in places like Grasslands, Wetlands, Forests, etc., they prefer dryer areas like normal trees and shrubs. Unlike other spiders in the genus Tetragnatha, T. versicolor will rarely reside near aquatic environments. T. versicolor will typically be colored dark yellow or pale orange and average around 5 mm for males and 6.5 mm for females in length, which is very small for a spider. They are much longer than they are wide, making them very distinct. In addition, T. versicolor can be distinguished from other spiders in Tetragnatha by the distinct separation of the anterior/posterior eyes and the appearance of their reproductive organs. As an orb weaver spider, T. versicolor creates a web to hunt for prey. It will wait at night for prey to stumble into its web and use vibrational signals throughout the web to sense trapped prey. In terms of mating behavior, T. versicolor lacks a distinct courting ritual and will mate with any others in the proximity. Mating behavior is heavily affected by female mating history. In terms of interactions with humans, the bite of T. versicolor is venomous, but not known to cause significant harm.