Biology:Deinacrida connectens

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Short description: Species of orthopteran insect

Alpine scree wētā
Adult male Deinacrida connectens with relatively long hind legs and narrow body
Invalid status (NZ TCS)
Scientific classification edit
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Orthoptera
Suborder: Ensifera
Family: Anostostomatidae
Genus: Deinacrida
Species:
D. connectens
Binomial name
Deinacrida connectens
(Ander, 1939)
Distribution map
Synonyms
  • Deinacridopsis connectens Ander, 1939
  • Deinacrida sonitospina Salmon, 1950

Deinacrida connectens, often referred to as the alpine scree wētā, is one of New Zealand's largest alpine invertebrates and is a member of the Anostostomatidae family. Deinacrida connectens is a flightless nocturnal insect that lives under rocks at high elevation. Mountain populations vary in colour. This species is the most widespread of the eleven species of giant wētā (Deinacrida).

Taxonomy

Deinacrida connectens, commonly referred to as the alpine scree wētā, was first described scientific literature in 1939 by Swedish entomologist Kjell Ernst Viktor Ander as Deinacridopsis connectens, which was the only species of Deinacridopsis.[1] However, Deinacridopsis was later recognized to be the same as the genus Deinacrida by New Zealand entomologist Graeme William Ramsay in 1961 and the species was transferred.[2] In the same paper, Ramsay also recognized Deinacrida sonitospina as a synonym of D. connectens, which was previously described by New Zealand entomologist John Salmon in 1950 from specimens found at Mount Peel and Mount Arthur.[2][3] The type specimens (the specimens the species description is based on) are stored in the Museum für Naturkunde Berlin.[4]

Description

Male Deinacrida connectens (top) are smaller than females (bottom)

Like other Deinacrida, the male is smaller than the female, with the male being about 3.5 cm (1.4 in) in length whereas the adult female is about 4.5 cm (1.8 in) in length, although the female can reach up 7.2 cm (2.8 in).[3][5][6] The adult can reach almost 10 g (0.35 oz) in weight.[7] Throughout its distribution, body colour is extremely variable. In some populations, individuals may have mostly black bodies (for example, those in a population located at Spence Peak in Southland) whereas others may have a mix of red, grey and olive colours.[8] The hind legs possess tiny "peg" like structures, referred to as stridulatory pegs which are used to produce sound by rubbing their abdominal tergites with the hind legs.[9] When alive, the species has a musky odour.[5]

Distribution and habitat

Deinacrida connectens is restricted to the South Island of New Zealand, where its distribution extends from the Wharepapa / Arthur Range in the Tasman region to Takitimu Range in the Southland region.[8] The range of D. connectens is known to overlap with those of other giant wētā, such as Deinacrida pluvialis in the western Otago mountains, and Deinacrida parva and Deinacrida elegans in the Kaikoura region.[10] This relatively widespread species distribution is unusual for Deinacrida, where species usually have a restricted distribution.[8] D. connectens generally inhabits scree slopes in alpine zones at elevations between 1,200 m (3,900 ft) and 3,600 m (11,800 ft) above sea level, but juveniles have also been found at 990 m (3,250 ft) above sea level.[3][8] It is not known what factor restricts them to this zone. The lower limit for their elevation range isolates populations on each mountain range.[11] D. connectens has been alleged to be the most abundant species of Deinacrida.[12]

Conservation

Under the New Zealand Threat Classification System as of 2022, Deinacrida connectens is listed as a "Not Threatened" species with the qualifier of "Data Poor: Trend".[13] Due to being restricted to high elevation, it is thought that introduced mammalian predators are not a threat to D. connectens populations, since these predators are uncommon in these regions. This is in contrast to other Deinacrida species, which are generally at lower elevation and are more frequently preyed upon by introduced predators, causes a decline in giant wētā species abundance.[14]

Ecology

Gaultheria depressa, one of the food sources of D. connectens

Deinacrida connectens is adapted to be moderately freeze tolerant and is adapted to high elevation zones.[15][16] It is known to be omnivorous, but in the wild is generally observed feeding on plants.[5] D. connectens has been observed in the wild browsing lichens, herbs and shrubs such as Aciphylla and Gaultheria depressa.[5][7] In captivity D. connectens would eat vegetables, fruit, raw beef, cheese and insects such as cicadas and beetles. Feeding generally occurs early at night, after D. connectens has emerged from their daytime cover.[5]

It is known to be capable of dispersing some fleshy fruit seeds by endozoochory. In an experiment, D. connectens' ability to disperse seeds of Gaultheria depressa by feeding was found to be dependent on the size of the wētā. At smaller sizes, fewer seeds were eaten and the wētā could be considered seed predators, (almost no seeds made it intact through the guts of individuals measuring 2 cm or less). With larger sized wētā however, thousands of seeds were consumed, some of which were presumably capable of being dispersed large distances, suggesting D. connectens can act as a seed disperser. One captive individual D. connectens was recorded successfully passing 686 intact seeds.[7]

Behaviour

During the day, Deinacrida connectens remains under rocks and in crevices of scree slopes. It may nestle with other conspecifics during this time. At night, it comes out of cover to feed.[5] When disturbed, D connectens will either remain motionless or attempt to run away and if they need to defend themselves, they will raise their legs in a threatening posture and produce soft sounds.[3] The sounds produced are soft and sound like when palms are rubbed together.[5] D. connectens has been described as an aggressive species, and will bite if provoked (although they do not appear to be strong enough to break skin).[3] In laboratory conditions (at temperatures higher than they normally experience), D. connectens have been known to travel nearly 4 metres per minute.[7]

After feeding, D. connectens will engage in "perching" behaviour, where it stands at the peak of a rock for extended periods of time during the night. In experimental conditions, individuals appeared to maintain an "individual distance" from one another while out at night. This boundary was maintained by producing sound and using their hind legs to push and kick away other individuals that got too close. However, this boundary does not seem to be maintained during the day, when individuals may huddle together under rocks and in crevices.[5]

Mating

Female Deinacrida connectens from near St Arnaud, North-West Nelson, NZ.

The long legs of males compared to females suggest that like other members of this genus the scree wētā has a scramble competition mating system, in which adult females signal and males search for mates. However, males of D. connectens appear to invest little energy into reproductive behaviours, and provide small spermatophores.[17] During mating in experimental conditions, males remain beneath the female, with the pair facing the same direction and with their bodies creating an angle of 30°. Copulation has been observed to last around 35 minutes. Mating would be concluded once the male walked away. There is a single observation in experimental conditions of a male scree wētā attempting to separate a mating pair.[5]

Genetics

Genetic diversity within Deinacrida connectens is high, being much greater than normal for insects.[18][11] In a phylogeography study of D. connectens, research found seven genetic lineages from mtDNA haplotypes, where each occupied a discrete geographic region. The average genetic difference between haplotypes was 4.8%.[12] This phylogeographical structure combined with lineage age estimations suggests D. connectens radiated during the Pliocene mountain building that created the Southern Alps 5 million years ago.[12][11] It was also suggested that subsequent glaciation may have helped foster isolation between population of D. connectens.[12]

Cytogenetics

Sex determination of most wētā species is by the number of large metacentric X-chromosomes; females have two X-chromosomes (XX) and males have one (X0).[19] The scree wētā is diploid with an even number of chromosomes in females, and an odd number in males, but populations within this species have different numbers of chromosomes. There are seven known karyotypes within D. connectens. These karyotypes vary in number of chromosomes from 2n = 17(X0) to 2n = 22(XX). Known locations of these karyotype races are listed below.[8]

References

  1. ↑ Ander, K (1939). "Vergleichend anatomische und phylogenetische studien. Ueber die Ensifera (Saltatoria)". Opuscula Entomologica: Supplementum 2: 293. https://bugz.ento.org.nz/detail/8583b465-d048-4c7d-9f26-0dd090a337c8. 
  2. ↑ 2.0 2.1 Ramsay, G W (1961). "The synonymy and systematics of a genus and two species of New Zealand weta (Orthoptera: Stenopelmatidae: Henicinae)" (in en). Proceedings of the Royal Entomological Society of London. Series B, Taxonomy 30 (7-8): 85–89. doi:10.1111/j.1365-3113.1961.tb00169.x. ISSN 0375-0434. https://resjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-3113.1961.tb00169.x. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Salmon, J T (1950). "A revision of the New Zealand wetas Anostostominae (Orthoptera: Stenopelmatidae)". Dominion Museum Records in Entomology (Wellington) 1: 10–13. https://bugz.ento.org.nz/detail/e3878a90-ce05-401a-a30a-d75d1b60d9ad. 
  4. ↑ "Deinacrida connectens (Ander, 1939)" (in en). https://www.gbif.org/species/100564069/verbatim. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Field, L H (1980). "Observations on the biology of Deinacrida connectens (Orthoptera: Stenopelmatidae), an alpine weta" (in en). New Zealand Journal of Zoology 7 (2): 211–220. doi:10.1080/03014223.1980.10423778. ISSN 0301-4223. https://rsnz.onlinelibrary.wiley.com/doi/10.1080/03014223.1980.10423778. 
  6. ↑ Patrick, B H (1991). "Insects of the Dansey Ecological District". https://www.doc.govt.nz/documents/science-and-technical/sr32.pdf. 
  7. ↑ 7.0 7.1 7.2 7.3 Larsen, H; Burns, K C (2012). "Seed dispersal effectiveness increases with body size in New Zealand alpine scree weta (Deinacrida connectens)" (in en). Austral Ecology 37 (7): 800–806. doi:10.1111/j.1442-9993.2011.02340.x. ISSN 1442-9985. https://onlinelibrary.wiley.com/doi/10.1111/j.1442-9993.2011.02340.x. 
  8. ↑ 8.0 8.1 8.2 8.3 8.4 Morgan-Richards, M; Gibbs, G W (2004). "Colour, allozyme and karyotype variation show little concordance in the New Zealand giant scree weta Deinacrida connectens (Orthoptera: Stenopelmatidae)" (in en). Hereditas 125 (2-3): 265–276. doi:10.1111/j.1601-5223.1996.00265.x. http://doi.wiley.com/10.1111/j.1601-5223.1996.00265.x. 
  9. ↑ Morgan-Richards, M; Gibbs, G W (2001). "A phylogenetic analysis of New Zealand giant and tree weta (Orthoptera : Anostostomatidae : Deinacrida and Hemideina) using morphological and genetic characters" (in en). Invertebrate Taxonomy 15 (1): 1–12. doi:10.1071/IT99022. ISSN 0818-0164. https://connectsci.au/is/article/15/1/1/67510/A-phylogenetic-analysis-of-New-Zealand-giant-and. 
  10. ↑ Gibbs, G W (2001). "Habitats and biogeography of New Zealand's Deinacridine and tusked weta species". in Field, L. H.. The biology of wetas, king crickets and their allies. CABI Books. Wallingford: CABI. pp. 35–55. doi:10.1079/9780851994086.0035. ISBN 978-0-85199-408-6. https://www.cabidigitallibrary.org/doi/10.1079/9780851994086.0035. 
  11. ↑ 11.0 11.1 11.2 Trewick, S A; Wallis, G P; Morgan‐Richards, M (2000). "Phylogeographical pattern correlates with Pliocene mountain building in the alpine scree weta (Orthoptera, Anostostomatidae)" (in en). Molecular Ecology 9 (6): 657–666. doi:10.1046/j.1365-294x.2000.00905.x. ISSN 0962-1083. https://onlinelibrary.wiley.com/doi/10.1046/j.1365-294x.2000.00905.x. 
  12. ↑ 12.0 12.1 12.2 12.3 Trewick, S A (2001). "Scree weta phylogeography: Surviving glaciation and implications for Pleistocene biogeography in New Zealand" (in en). New Zealand Journal of Zoology 28 (3): 291–298. doi:10.1080/03014223.2001.9518271. ISSN 0301-4223. https://rsnz.onlinelibrary.wiley.com/doi/10.1080/03014223.2001.9518271. 
  13. ↑ "NZTCS". https://nztcs.org.nz/assessments/159800. 
  14. ↑ Gibbs, G W (1998). "Why are some weta (Orthoptera: Stenopelmatidae) vulnerable yet others are common?" (in en). Journal of Insect Conservation 2 (3): 161–166. doi:10.1023/A:1009660200402. ISSN 1572-9753. https://doi.org/10.1023/A:1009660200402. 
  15. ↑ Sinclair, B J (1999). "Insect cold tolerance: How many kinds of frozen?". European Journal of Entomology 96: 157–164. https://www.eje.cz/pdfs/eje/1999/02/09.pdf. 
  16. ↑ Wharton, D A (2011). "Cold tolerance of New Zealand alpine insects". Journal of Insect Physiology. "Cold and Desiccation Tolerance" honoring Karl Erik Zachariassen 57 (8): 1090–1095. doi:10.1016/j.jinsphys.2011.03.004. ISSN 0022-1910. https://www.sciencedirect.com/science/article/pii/S0022191011000709. 
  17. ↑ Kelly, C D; Bussière, L F; Gwynne, D T (2008). "Sexual selection for male mobility in a giant insect with female‐biased size dimorphism" (in en). The American Naturalist 172 (3): 417–423. doi:10.1086/589894. ISSN 0003-0147. https://www.journals.uchicago.edu/doi/10.1086/589894. 
  18. ↑ Morgan-Richards, M; Wallis, G P; Trewick, S A (2011). "The invertebrate life of New Zealand: A phylogeographic approach" (in en). Insects 2 (3): 297–325. doi:10.3390/insects2030297. PMID 26467729. 
  19. ↑ McKean, N E; Trewick, S A; Morgan‐Richards, M (2015). "Comparative cytogenetics of North Island tree wētā in sympatry" (in en). New Zealand Journal of Zoology 42 (2): 73–84. doi:10.1080/03014223.2015.1032984. ISSN 0301-4223. https://rsnz.onlinelibrary.wiley.com/doi/10.1080/03014223.2015.1032984. 

Wikidata ☰ Q5252453 entry



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