Deinacrida tibiospina

Sparse (NZ TCS)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Orthoptera
Suborder: Ensifera
Family: Anostostomatidae
Genus: Deinacrida
Species:
D. tibiospina
Binomial name
Deinacrida tibiospina
Salmon, 1950

Deinacrida tibiospina, also known as the Mt Arthur giant wētā[1] or the Nelson alpine giant wētā,[2] is a species of wētā in the family Anostostomatidae. It is endemic to the South Island of New Zealand.[2] The wētā is only found in some alpine zones of Kahurangi National Park.[2] Compared with natural densities of other wētā, D. tibiospina is fairly rare.[3] Little conservation effort has been made for this species because, despite its elusiveness, populations on the mainland have been maintained without human intervention.[2]

Description

As one of the smallest known species of giant wētā, Deinacrida tibiospina grows to only around 30-40mm long, and weigh just 7 grams.[1][2][4] Like many other giant wētā, such as Deinacrida rugosa, the overlapping armoured plates on their back are wrinkled.[5] Adults of the species can be varying shades of brown, sometimes with a reddish hue.[3] Their bodies have a compressed appearance and dense spines on the upper side of their hind femurs.[3] As with almost all wētā, D. tibiospina are wingless.[6]

There is sexual dimorphism in this species.[7] Female D. tibiospina are larger than males, a common trait in many Orthoptera.[7][8][6] Males of the species also have fewer hind femoral spines than females.[7]

Distribution and habitat

Deinacrida tibiospina live in alpine areas of Kahurangi National Park, located at the North-Western corner of New Zealand's South Island.[2] The wētā dwell above the tree line in sub-alpine tussock and herbfield zones of mountains,[9] observed at altitudes between 900 and 1500 meters.[1][7] Populations of D. tibiospina occur at very low densities at scattered localities within the central and eastern areas of what was North-West Nelson Forest Park.[3]

Biology

Throughout the day, Deinacrida tibiospina often shelter at the base of tussocks, Astelia, flax and other alpine plants.[3][7][9] Their lifespan may be 2–3 years as wild populations have been observed with 3 distinct age classes in February and March.[3][4] Like other wētā, D. tibiospina are nocturnal,[3] but they may be comparatively inactive because of the cold temperatures in their alpine habitat.[1]

Little research has been completed on the diet of D. tibiospina but they do not seem to like peanut butter, used as a lure for monitoring methods, as much as other wētā.[1]

Taxonomy

Deinacrida tibiospina was first described in 1950 by New Zealand scientist John Salmon.[6] The species name tibiospina translates to tibia spine, or shin spine. This is likely a reference to the species' densely spined hind legs.[2][3] Why the species is not called femoraspina because most of its spines are on the femurs, not the tibia, is a mystery.[2]

Current phylogenetic and systematic research suggests Deinacrida tibiospina is a sister species of the lowland species D. carinata.[10][11]

Threats

The low density of Deinacrida tibiospina may be natural or it could be a result of human impacts.[1] If the latter is true, human-introduced mammalian predators such as rodents may threaten D. tibiospina populations, as other giant wētā species have been significantly impacted where these predators exist.[2] It is not certain, though, if D. tibiospina are as at risk to mammalian predation as rodents may not be abundant at high elevation.[2][12] A 2010 study using footprint tracking tunnels found that mouse populations did overlap D. tibiospina habitat, however, wētā density was the highest at locations with the fewest mouse observations.[1] These findings may imply that D. tibiospina are indeed negatively impacted by mice.[1]

Conservation

In comparison with its close relatives, Deinacrida tibiospina has not received a great amount of conservation work. In 1989, a Department of Conservation report listed Deinacrida tibiospina as needing urgent research to prevent extinction,[12] but by 1998 the Department of Conservation Threatened Weta Recovery Plan listed D. tibiospina as low priority for conservation management.[2]

A University of Otago study found tracking tunnels were not reliable for monitoring the species because their scarcity and lack of attraction to peanut butter lures results in low counts.[1] One generation of Deinacrida tibiospina has, however, been successfully bred in captivity, generating hope for conservation efforts should the species need them.[2][3]

References

  1. 1 2 3 4 5 6 7 8 9 Anker, Alison. (2010). The use of tracking tunnels to monitor the Mt Arthur giant weta (Deinacrida tibiospina). Wildlife Management Report: 236. University of Otago: Dunedin
  2. 1 2 3 4 5 6 7 8 9 10 11 12 Sherley, Greg (1998). "Threatened Weta Recovery Plan" (PDF). New Zealand Threatened Species Recovery Plans. Biodiversity Recovery Unit, Department of Conservation, Wellington (25). ISSN 1170-3806.
  3. 1 2 3 4 5 6 7 8 9 Meads, Mike. (1989). The conservation status of the giant weta Deinacrida tibiospina in Northwest Nelson: report of a field visit and notes on other invertebrates. Ecology Division Report 21. N.Z. Dept. Scientific and Industrial Research (DSIR), Wellington.
  4. 1 2 Laurence, Field (2000). The Biology of Wetas, King Crickets and their Allies. Wallingford, UK: CABI Publishing. p. 47. ISBN 0-85199-408-3.
  5. ↑ Gibbs, George W. (1999). "Four new species of giant weta, Deinacrida (Orthoptera: Anostostomatidae: Deinacridinae) from New Zealand". Journal of the Royal Society of New Zealand. 29 (4): 307–324. doi:10.1080/03014223.1999.9517600.
  6. 1 2 3 Salmon, John Tenison (1950). "Revision of the New Zealand wetas – Anostostominae (Orthoptera: Stenopelmatidae)". Dominion Museum Records in Entomology. 1: 121–177.
  7. 1 2 3 4 5 Salmon, J. T. (1956). "A male specimen of Deinacrida tibiospina Salmon". New Zealand Entomologist. 2 (1): 8–10. doi:10.1080/00779962.1956.9722747. ISSN 0077-9962.
  8. ↑ Hochkirch, Axel & Julia, Gröning. (2008). Sexual size dimorphism in Orthoptera - a review. Journal of Orthoptera Research, 17. 189–196.
  9. 1 2 Meads, Mike. (1990). The weta book : a guide to the identification of wetas. DSIR Land Resources (N.Z.). Lower Hutt, N.Z.: DSIR Land Resources. ISBN 0-477-02585-4. OCLC 32648051.
  10. ↑ Morgan-Richards, Mary; Gibbs, George W. (2001). "A phylogenetic analysis of New Zealand giant and tree weta (Orthoptera : Anostostomatidae : Deinacrida and Hemideina) using morphological and genetic characters". Invertebrate Systematics. 15 (1): 1. doi:10.1071/IT99022. ISSN 1445-5226.
  11. ↑ Twort, Victoria G; Newcomb, Richard D; Buckley, Thomas R (2019). Bryant, David (ed.). "New Zealand Tree and Giant Wētā (Orthoptera) Transcriptomics Reveal Divergent Selection Patterns in Metabolic Loci". Genome Biology and Evolution. 11 (4): 1293–1306. doi:10.1093/gbe/evz070. ISSN 1759-6653. PMC 6486805. PMID 30957857.
  12. 1 2 Sherley, Greg (1989). New Zealand. Department of Conservation. Science and Research Directorate. "Important conservation research topics on terrestrial arthropod species in New Zealand" (PDF). Science and Research Internal Report. Wellington, N.Z.: Head Office, Dept. of Conservation (53): 3. ISBN 0-478-01126-6. ISSN 0114-2798. OCLC 154276184.{{cite journal}}: CS1 maint: ignored ISBN errors (link)
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