Ancyronyx

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Spider water beetles
Ancyronyx schillhammeri adult
Ancyronyx patrolus larva
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera
Family: Elmidae
Subfamily: Elminae
Tribe: Ancyronychini
Ganglbauer, 1904
Genus: Ancyronyx
Erichson, 1847
Type species
Macronychus variegatus
Germar, 1824
Species

See text

Ancyronyx, commonly known as spider water beetles or spider riffle beetles, is a

riffle beetles from North America, South Asia, China, and Southeast Asia. They are small beetles with extremely long legs ending in strong claws. Both the adults and the larvae are found underwater in the shallow riffles of streams and rivers, clinging to rocks or submerged wood. They feed on algae and decaying wood tissue. The genus contains twenty-one species, eleven of which are endemic to the Philippines
.

Taxonomy

The genus Ancyronyx was established in 1847 by the German

entomologist Antoine Henri Grouvelle described the second species, A. acaroides in 1896.[2][3] It is the sole member of the tribe Ancyronychini, and is classified under the subfamily Elminae of the riffle beetle family, Elmidae.[3]

Description

Members of Ancyronyx superficially resemble

pronotum possesses a transverse groove and a more or less straight front margin, with pronotal carinae absent or weakly present.[5]

Spider water beetles can be divided into two

species groups, based on morphological and ecological adaptation patterns.[8]

  • The
    prosternal process. Their larvae are also larger, depressed in cross-section, and possess large side-pointing projections on the sides of the abdomen.[3][5][8]
  • The Ancyronyx patrolus species group have small and slender bodies, with comparatively shorter legs, long and slender coxites on the ovipositor, and a squarish prosternal process. Their larvae are smaller, with a more vaulted cross-section, and backwards pointing projections from the sides of the abdomen.[3][5][8]

Ancyronyx is closely related to the genus Podelmis, but can be distinguished from the latter by the more or less straight and slender last segment of the ovipositor (versus the conical sideways-bent terminal segment of the ovipositor of Podelmis), and the absence of an anterior process on the prosternum.[3]

Ecology

type locality of Ancyronyx montanus

Like almost all riffle beetles, spider water beetles are aquatic, feeding on

lotic riffles of streams and rivers.[2]

The larvae are exclusively aquatic. They breathe by means of

setae) on their body. As the insect breathes, the oxygen concentration in the gas film drops in comparison to the surrounding water, causing new oxygen to diffuse again into the plastron.[10][11][12]

Because of their reliance on the plastron for breathing, spider water beetles are restricted to the highly

oxygenated environments in moderate to fast-moving permanent running water.[5] They are therefore extremely sensitive to water pollution and are potentially valuable bioindicators for measuring the health of river ecosystems.[4][13]

Members of the Ancyronyx variegatus species group are mostly found in slightly to moderately polluted (mesosaprobic) rivers, almost always found on submerged wood (with the exception of Ancyronyx yunju which were collected from sand and grass roots). Members of the Ancyronyx patrolus species group, meanwhile, are only found in clean permanent streams, usually among rocks.[3][5][8]

Ancyronyx malickyi have been caught using light traps, which might indicate phototaxis.[2]

Distribution

The genus was previously only known from two species from highly disjunct localities – Ancyronyx variegatus from North America (described in 1824) and

Austrian coleopterologists Manfred A. Jäch and S. Schödl, confirming its type locality. In addition they also discovered the species in Southeast Asia, including West Malaysia, Sarawak and Bali during 1992 and 1993. The species was also subsequently found in Thailand, Indonesia and the Philippines.[2] Since then, nineteen new species of the genus have been described from Southeast Asia and China.[3][5][14][15]

Species

3 Ancyronyx minerva larva, 4 Ancyronyx punkti larva, 5 Ancyronyx pseudopatrolus larva, 6 Ancyronyx patrolus larva, 7 Ancyronyx montanus adult, 8 Ancyronyx montanus larva, 9 Ancyronyx procerus larva, 10 Ancyronyx helgeschneideri larva
2 Ancyronyx minerva adult, 3 Ancyronyx tamaraw adult, 4 Ancyronyx buhid adult, 5 Ancyronyx minerva larva, 6 Ancyronyx tamaraw larva, 7 Ancyronyx buhid larva, 8 Ancyronyx schillhammeri adult, 9 Ancyronyx schillhammeri larva

There are twenty-one species currently classified under Ancyronyx.

center of diversity for the genus.[7][12] Most of the species have highly restricted distributions, often being found in only one island.[16][17]

References

  1. ^ Harley P. Brown (1983). A Catalog of the Coleoptera of America North of Mexico, Family: Elmidae (PDF). Agriculture Handbook Number 529-50. Agricultural Research Service, United States Department of Agriculture. p. 3.
  2. ^
    doi:10.5962/bhl.part.79919
    .
  3. ^
    PMID 23950689
    .
  4. ^
    PMID 22140348
    .
  5. ^
    doi:10.11646/zootaxa.3382.1.6
    .
  6. ISBN 978-1-4200-4123-1
    .
  7. ^ a b Pensoft Publishers (October 18, 2011). "Unknown Species And Larval Stages of Extremely Long-legged Beetles Discovered by DNA Test". ScienceNewsline. Archived from the original on September 28, 2013. Retrieved August 21, 2013.
  8. ^
    doi:10.11646/zootaxa.1590.1.2. biostor
  9. JSTOR 1942455. Archived from the original
    (PDF) on 2013-09-27. Retrieved 2013-09-15.
  10. ^ a b "Elmidae". Identification and Ecology of Australian Freshwater Invertebrates, Murray Darling Freshwater Research Centre. Retrieved August 22, 2013.
  11. ^ a b Pensoft Publishers (August 6, 2013). "'Beetle in Spider's Clothing' – Quaint New Species from Philippine Rainforest Creeks". ScienceNewsline. Archived from the original on September 28, 2013. Retrieved August 21, 2013.
  12. ^ a b "Unknown species and larval stages of extremely long-legged beetles discovered by DNA test". Science Codex. October 18, 2011. Retrieved August 22, 2013.
  13. ^ K.D. Suarez (August 7, 2013). "New beetle species discovered in Mindoro". Rappler. Retrieved August 21, 2013.
  14. doi:10.11646/zootaxa.3255.1.4
    .
  15. ^ Gilliann S. Ebreo (November 27, 2012). "Ateneo prof discovers new beetle species". The GUIDON, Ateneo de Manila University. Archived from the original on September 6, 2013. Retrieved August 22, 2013.
  16. ^ a b Manfred A. Jäch; Ján Kodada (2010). "Family Elmidae". In Joel Hallan (ed.). Synopsis of the described Coleoptera of the World.
  17. ^ Manfred A. Jäch (April 2004). "Descriptions of two new species of Ancyronyx Erichson (Insecta: Coleoptera: Elmidae)" (PDF). Annalen des Naturhistorischen Museums in Wien. 105: 389–395.

External links

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