Katipō | Read 10 Min

Katipō

Female katipō
Conservation status
Declining (NZ TCS)
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Class:	Arachnida

Katipō (pronounced /kɑːtɪˈpɔː/ kah-tih-PAW or /ˈkɑːtəpoʊ/ KAH-tə-poh; Latrodectus katipo) is a species of cobweb spider found only in New Zealand. It is one of many species in the genus Latrodectus and is most closely related to the Australian redback (L. hasseltii). It is venomous to humans, its bite being capable of producing the toxic syndrome latrodectism; symptoms include extreme pain and, potentially, hypertension or seizure. Bites are rare and antivenom is available in some hospitals. The female is 8–10 millimetres (0.31–0.39 in) in length; the male is 4–5 millimetres (0.16–0.20 in). In the South Island and the lower half of the North Island, the female has a distinct red stripe bordered in white on its abdomen; 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 hourglass-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 the West Coast. It feeds mainly on ground-dwelling insects, caught in an irregular tangled web spun among dune plants or other debris. After mating, the female katipō produces five or six egg sacs in November or December. The juveniles hatch after 20–25 days, and 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 (to sting) and pō (the night). Due to habitat loss, colonisation of their natural habitat by invasive 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 New Zealand doctor Llewellyn Powell described it as Latrodectus katipo. Swedish arachnologist Tamerlan Thorell later placed it in Latrodectus scelio, a previous name for Latrodectus hasseltii (redback spider). Later, New Zealand arachnologist Arthur Urquhart unknowingly described it again as two species: Theridium melanozantha in 1887 and 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 American arachnologist Elizabeth Bryant and thus were synonymised. Several taxonomic studies 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 concluded that L. katipo, together with L. katipo var. atritus, are separate from L. hasseltii.

There was further confusion over whether L. katipo and L. katipo var. atritus should be considered separate species due to their very similar morphology but notably different distributions. Although they were designated as separate species for a time, this was clarified when the species was revised again in 2008. In this revision, L. atritus was 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 (black widow spider), Latrodectus geometricus (brown widow spider) and Latrodectus hasseltii (redback spider), to the latter of which the katipō is most closely related. It is a member of the family Theridiidae, which are commonly known as cobweb spiders or comb-footed spiders.

Etymology

The common name and specific name katipō (singular and plural), often spelt "katipo", is Māori for "night stinger", derived from the words kakati (to sting) and pō (the night). 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 the katipō are most closely related to the Australian Latrodectus hasseltii (redback spider). The katipō are so closely related to the redback that the katipō was thought to be a subspecies of the redback. Further research has shown that the katipō is genetically and morphologically 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 8–10 millimetres (0.31–0.39 in) or 35–41 millimetres (1.4–1.6 in) 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 appearance 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. The katipō can be distinguished from L. hasselti by the short setae (hair-like spines) of the abdomen, whereas on the abdomen of L. hasselti it is a mix of long and short setae. There are also minor differences 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". The katipō has a less shiny and more tapered abdomen, and the lateral eyes (eyes at the side of the head) 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 4–5 millimetres (0.16–0.20 in) in length, keeps 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, but 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, one study reporting that the red katipō is found in cooler areas with average temperatures of 11.24–13.85 °C (52.23–56.93 °F). In contrast, the black katipō is found in warmer areas with average temperatures of 13.64–16.23 °C (56.55–61.21 °F).

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 (Ficinia spiralis) or the introduced marram grass (Ammophila arenaria). The spider may also build its web under driftwood, stones, or other debris such as rubbish. This behaviour can be exploited by researchers and conservationists by placing plywood lids in katipō habitat, under which the spider hides, allowing its populations to be easily sampled. Webs are almost always constructed over open sand and near the ground so as to catch crawling insects for food. The katipō inhabiting dune grasses constructs its web in open spaces between the grass tufts; the katipō inhabiting areas of shrubbery does so on the underside of a plant overhanging open sand. It has been found that these patches of open sand are necessary for the katipō to build its web, as plants that envelop sand dunes in dense cover, such as invasive plants like kikuyu or buffalo grass, create an environment unsuitable for web construction. The katipō commonly spins its web among 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 are 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 with which to mate, 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, she becomes docile and allows him to approach. 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 (appendages modified for reproduction) into the female's reproductive tract 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 12 millimetres (0.47 in) 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 continue to develop within the egg sac where they remain until the second instar, at which stage they feed on the wall of the egg sac. After four to six weeks of incubation, during January and February, the juveniles chew their way out of the egg sac. The young spiders then disperse from the web. In one 24-hour study of juveniles, 28% dispersed from the web by ballooning—using air currents to carry themselves away from the nest on a single silk strand. The majority, 61%, used bridging, moving to nearby plants along silk threads, while 11% remained in the nest.