Katipō
Katipō is a species of spider endemic to New Zealand. It's one of many species in the genus Latrodectus and is most closely related to the Australian redback. It is venomous to humans, capable of delivering a potentially dangerous bite. The bite produces the toxic syndrome latrodectism; symptoms include extreme pain and, potentially, hypertension, seizure, or coma. Bites are rare, an antivenom is available, and very few deaths have been reported. The female is in length whereas the male is. In the South Island and the lower half of the North Island the female has a distinct red stripe bordered in white on their abdomen whereas in more northern populations this stripe is absent, pale, yellow, or replaced with cream-coloured blotches. These two forms were previously thought to be separate species. The male is white with black stripes and red diamond-shaped markings.
The Katipō is mainly found living in sand dunes close to the seashore. It is found throughout most of coastal New Zealand except the far south and West Coast. It feeds mainly on ground dwelling insects, caught in an irregular tangled web spun amongst dune plants or other debris. After mating, the female katipō produces five or six egg sacs in November or December. The spiderlings hatch after 20–25 days and then during January and February they disperse into surrounding plants. The common name is from Māori for "night stinger", which is derived from the words kakati and pō . Due to habitat loss, colonisation of their natural habitat by exotic spiders and hybridisation with L. hasseltii, the katipō is listed as "in serious decline" by the New Zealand Threat Classification System.
Taxonomy
The katipō was reported as early as 1855 as the 'kātĕpo, but was not formally described in taxonomic literature until 1870 when Llewellyn Powell described it as Latrodectus katipo. However, Swedish arachnologist Tamerlan Thorell later placed it in Latrodectus scelio, a previous name for Latrodectus hasseltii. Later arachnologist Arthur Urquhart unknowingly described the species again, first as Theridium melanozantha in 1887, then as Theridium zebrinia in 1890. He also described Latrodectus katipo var. atritus, a subspecies of katipō that was fully black in colour. In 1933 Urquhart's two species were later recognised to be the same as L. katipo by arachnologist Elizabeth Bryant and thus were synonymised. There have been numerous taxonomic studies that have disagreed over whether to treat L. katipo as a separate species or as a synonym of L. hasseltii with L. atritus as a subspecies. Eventually, it was conceded that L. katipo and L. atritus were separate from L. hasseltii.The species was recently revised again in 2008. In this revision, L. atritus were formally recognised to be the same as L. katipo on the basis of genetic data and thus was synonymised. It was proposed that the colour variation seen between these two groups is a cline, or gradual continuous variation over latitude and is correlated with mean annual temperature.
The katipō is a member of the genus Latrodectus. This genus has a worldwide distribution with notable members such as Latrodectus mactans, Latrodectus geometricus and Latrodectus hasseltii '','' the latter of which the katipō is most closely related to. It is a member of the family Theridiidae, which are commonly known as cobweb spiders or comb-footed spiders.
Etymology
The common name katipō, often spelt "katipo", is from Māori for "night stinger", derived from the words kakati and pō. It is one of the few Māori words that refers to a specific species of spider. The fully black variant is referred to as black katipō.Phylogeny
A 2004 study examined the genetic relationships of Latrodectus spiders using sequences from part of the cytochrome c oxidase subunit I gene. The study found that katipō are most closely related to the Australian Latrodectus hasseltii ''.'' The katipō are so closely related to the redback that they were thought to be a subspecies. Further research has shown that the katipō are distinct from the redback, having slight structural differences and striking differences in habitat preference.''''Description
As an adult, the female has a body size of or if leg span is included. The red katipō, found in the South Island and the lower North Island, has a large black globular abdomen with a silky texture and a distinctive white-bordered orange or red stripe on its upper surface that runs from the beginning of the abdomen back to the spinnerets. The underside of the abdomen is black and has a red patch or partial red hourglass-shaped marking. For the black katipō, found in the upper North Island, the abdomen differs in not having the upper red/orange stripe and is overall somewhat lighter in colour. The hourglass pattern on the underside of the abdomen may also be less distinct, losing the middle section. Rare variations in black katipō also exist where the abdomen, cephalothorax, or entire body is brown, sometimes with a dull red or yellow stripe, or cream-coloured spots on its upper side.The katipō is most similar to its sister species Latrodectus hasselti. It can be distinguished from this species by the short setae of the abdomen, whereas on the abdomen of L. hasselti it is a mix of long and short setae. There are also minor difference in the shape of the female and male genitalia structures. It may also be confused for Steatoda species, which are often present in the same habitat. One of the species, Steatoda capensis is so similar that they are commonly referred to in New Zealand as "false katipō". Katipō has a less shiny abdomen, a more tapered abdomen and the lateral eyes are further apart.
Males and juveniles
As juveniles, the female and male are identical until their fourth instar, a developmental stage that occurs between moults. Before this, they are coloured whitish and have black markings running vertically down the abdomen. The abdomen also frequently has traces of red. The male, which is in length, keep this juvenile colour pattern as an adult.Distribution and habitat
The katipō is only found in New Zealand. In the North Island it is found throughout the West Coast from North Cape to Wellington. On the east coast of the North Island it occurs irregularly, however, it is abundant on Great Barrier Island. In the South Island it is found in coastal regions south to Dunedin on the east coast and south to Greymouth on the west coast. It has been proposed that this southern limit is due to the katipō needing warmer temperatures to allow for the development of their eggs.The red katipō is found south of the western tip of Taranaki on the west coast, and just north of Waipatiki Beach in Hawke's Bay on the east coast. The black katipō are found north of Aotea Harbour in the Waikato region on the west coast, and Waipiro Bay in the Gisbourne region on the east coast. Both forms are found in a transitionary area in between these aforementioned localities. These colour variants are strongly correlated with temperature, with one study reporting that red katipō is found in cooler areas with average temperatures of 11.24–13.85°C. In contrast black katipō is found in warmer areas with average temperatures of 13.64–16.23°C.
Habitat
The katipō is restricted to coastal sand dunes near the seashore. It generally resides on the landward side of dunes closest to the coast where it is most sheltered from storms and sand movement. It can sometimes be associated with dunes several kilometers from the sea when these dunes extend inland for long distances.Webs are typically established in low-growing dune plants and other vegetation such as the native pīngao or the introduced marram grass. It may also build its web under driftwood, stones, or other debris such as rubbish. This behaviour can be exploited by placing plywood lids in katipō habitat, which the spider hides under and can thereby have its populations easily sampled. Webs are almost always constructed over open sand and near the ground so as to catch crawling insects for food. Katipō inhabiting dune grasses constructs its web in open spaces between the grass tufts, while katipō inhabiting areas of shrubbery do so on the underside of a plant overhanging open sand. It has been found that these patches of open sand are necessary for katipō to build its web as plants that envelop sand dunes in dense cover, such as exotic plants like kikuyu or buffalo grass, create an environment unsuitable for web construction. The katipō commonly spins its web amongst pīngao as this plant's growth pattern leaves patches of sand between each plant. Marram grass has been extensively planted in New Zealand to help stabilise sand dunes and has largely replaced pīngao in many areas. Because marram grass grows in a very tight formation only leaving small gaps between tuffs, this makes it difficult for the katipō to construct a suitable web for capturing prey. Due to this, it has been demonstrated that the katipō is less abundant in dunes dominated by marram grass than they are in dunes dominated by pīngao.Life history
Reproduction
Once it becomes an adult, the male begins to search for a female to mate with, possibly being guided by pheromones in female's silk. The male enters the female's web and gently vibrates the silk as he approaches her. The female is usually aggressive at first and will chase the male from the web. The courtship process consists of the male bobbing, plucking and tweaking the web along with periods of cautious approach and being chased by the female. Eventually, when she becomes docile and allows him to approach, the male will approach the female as she hangs quietly upside down in the web. The male moves to the underside of her abdomen, tapping her rapidly until their abdomens are aligned in the same direction. He then inserts his palps into the female's reproductive tract one at a time one at a time. Copulation occurs over 10 to 30 minutes. After mating, the male retreats to groom, which is performed by running his palps and legs through his fangs and wiping them over his body. The male is not eaten by the female unlike some other widow spiders.The female lays its eggs in November or December. The eggs are round, about the size of a mustard seed, and are a transparent, purplish red. They are held together in a cream-coloured, round, ball shaped egg sac which is about in diameter. The female constructs five or six egg sacs over the next three to four weeks. Each egg sac contains about 70 to 90 fertilised eggs. The egg sacs are hung in the centre of the spider's web and the female spins more silk over them, which becomes covered in sand and conceals them somewhat.
The eggs hatch after 20–25 days and contain to develop within the eggsac where they remain until the second instar, at which stage they feed on the wall of the eggsac. After four to six weeks of incubation, during January and February, the juveniles chew their way out of the eggsac. The young spiders then disperse from the web. In one study, observing juveniles over 24 hours, 28% used a ballooning method, which is where the juveniles use air currents to carry themselves away from the nest suspended by a single web strand, while the majority, 61%, used a bridging method where the juveniles use their silk to move to nearby plants, and 11% still remained in the nest.
Due to their close relatedness, the katipō and redback are capable of interbreeding. A male redback is able to successfully mate with a female katipō producing hybrid offspring. However, a male katipō cannot mate with the female redback as the male katipō is heavier than the male redback, and when it approaches the web it triggers a predatory response in the female leading to the male usually being eaten before mating can occur. There is evidence of interbreeding between katipō and redbacks in the wild, with one specimen reported to have redback DNA in its maternal lineage.
Population demographics
The proportion of females, males and juveniles in a population varies somewhat depending on site. As adults, the female is generally more abundant than the male, probably because the male lives on average 77 days whereas thr female can live for two years. Along the Manawatu-Whanganui coastline, some sites that were surveyed had only the adult female detected whereas at other sites the juvenile was more common than the adult. It has been proposed that sites with few juveniles detected may be due to low reproductive output.Behaviour
Prey capture
Katipō prey varies depending upon location, but it typically catches wandering ground invertebrates such as beetles or amphipods, but it may occasionally catch moths, flies, and other spiders. Katipō can catch insects much larger than themselves. These larger insects often become entangled in the web and in the ensuing struggle, the web's ground anchor line breaks. The silk's elasticity causes the prey to become suspended a few centimetres off the ground. Whether the prey is suspended, and how high, depends on how heavy the prey is. Earwigs caught in the web aren't suspended at all whereas slaters, which are much lighter, can be suspended at varying heights. The katipō then moves to the prey, turns so that the spinnerets are facing the insect and spins silk over it. Like most theridiids, the tarsi of the hind legs have a row of strong curved bristles which are arranged as a comb. The katipō uses these to scoop sticky silk from its spinnerets and throws it over the insect with a series of rapid movements. After the insect is firmly immobilised, the spider bites it several times, usually at the joints, before spinning more silk to strengthen the web, and then administering a last long bite which ultimately kills the insect. The spider then moves the prey up into the web until it is ready to eat. If food is readily available then it is common to see five or six insects hanging in the web waiting to be ingested. The male's hunting behaviour is similar to the female's, although may not be as vigorous due to its smaller size.Web structure
Like other theridiid spiders, the web is a seemingly disorganised tangle of silk. The structure consists of a retreat for the katipō to hide in and a catching web for obtaining prey. The retreat is loosely tube shaped with an open end and is generally formed inside the base of coastal tussocks or other debris. The walls of the retreat are interwoven and are waterproof. The catching web extends out from the retreat and can be divided into three layers. The upper and middle layers are constructed horizontally. Of these, the upper layer is formed as a network of mesh that supports the middle layer, which forms a dense latticed sheet that extends in all directions. The lower layer is constructed vertically, with threads extending from the above layers to the ground. These threads have viscous droplets that can assist in capturing prey. The web is spun during the early morning and at night. If the web is destroyed it can be rebuilt overnight rather quickly.Predators
The eggs of katipō have been observed being eaten by a small, undescribed native wasp from the family Ichneumonidae. It has also been proposed that house mice, which are not native to New Zealand, may also prey upon katipō.Conservation status
Under the New Zealand Threat Classification System, the katipō is listed as "Declining", with the qualifiers of "Climate Impact", "Data Poor: Trend" and "Range Restricted". A number of factors have contributed to its decline; the major ones appear to be habitat loss and the declining quality of the remaining habitat. Human interference with their natural habitat has been occurring for over a century following European settlement. Coastal dune modification resulting from agriculture, forestry, or urban development, along with recreational activities like the use of beach buggies, off-road vehicles, beach horse riding and driftwood collection have destroyed or changed areas where the katipō lives. The introduction of many invasive exotic plants may have also contributed to the decline of suitable habitat. It has also been proposed that surfactants may pose a risk to the katipō.Much of the katipō habitat is also occupied by the exotic spider Steatoda capensis with both species being found sharing the same dune systems or even co-existing under the same piece of driftwood, suggesting that the two species can co-exist in similar habitats. However, there is evidence that displacement of the katipō is occurring due to the ability of S. capensis to quickly recolonise areas from which the katipō had been displaced after storms or other dune modifications. Furthermore, S. capensis breeds year-round, produces more offspring and lives in a greater range of habitats which leads to greater pressure on the katipō.
In 2010 the katipō was one of a dozen species of previously unprotected invertebrate given full protection under the 1953 Wildlife Act, noted as "iconic, vulnerable to harm, and in serious decline". Under the Act, killing an absolutely-protected species such as a katipō is punishable by a fine or even imprisonment. It has been proposed that restoration of sand dune habitat, including the replacing of marram grass with native dune plants, would provide more suitable habitat for the katipō to conserve their populations. Reducing activities that damage sand dunes, such as off-road driving and rubbish dumping may also protect the species.
Toxicology
The katipō has venom that is medically significant in humans, although bites are uncommon due to the rarity of the species. Antivenom is available in some hospitals to treat bites. The incidence of bites is low as it is a shy, non-aggressive spider. Their narrow range, diminishing population, and human awareness of where they live means humans rarely encounter katipō. The katipō will only bite defensively. However, if the female is with an egg sac it will remain close by it and be more aggressive. Bites from katipō produce a syndrome known as latrodectism. The venoms of all Latrodectus spiders are thought to contain similar components with the neurotoxin α-latrotoxin being the main agent responsible. It has been reported that only the female is capable of biting humans.Māori legends recall deaths due to bites. One legend states that an entire group of Māori camped out at the mouth of the Whanganui River were bitten overnight, with two dying. Bites are very rare, with 23 of the 37 known hospitalisations for spider bites between 1967 and 1976 in New Zealand being attributed to katipō bites. The most recent reported katipō bites were to a Canadian tourist in 2010 and a kayaker in 2012, both of which survived.