Colobopsis Schmitzi

''Colobopsis schmitzi'', synonym ''Camponotus schmitzi'', is a species of ant native to Borneo, Schuitemaker, J.P. & A. Stärcke 1933. ''Overdruk uit het Natuurhistorisch Maandblad'' 22(3): 29–31. which is commonly known as the diving ant, swimming ant or pitcher-plant ant, due to their habit of diving into the digestive fluids of their plant host ''Nepenthes bicalcarata''. They are endemic to the island of Borneo.

Description

''C. schmitzi'' closely resemble '' Colobopsis ceylonicus'' but are slightly larger. They have rectangular heads about one and a half times as long as they are wide. The mandibles have five teeth each (except for the minor workers which have four). The eyes are widely separated and located laterally, slightly behind the anterior bulge of the head. The antennae are short, with a scape at in length. The funicules are longer than they are wide proximally and become shorter and wider towards the tip. The body is smooth and shiny. The gaster is small. The legs are relatively large, especially the femurs, and very compressed laterally. Spines are present near the distal tip of the femurs and absent in the tibiae. The tarsi are longer than the tibiae.

''C. schmitzi'' exhibit polymorphism, with three physical castes - minor, median, and major ("soldier") workers. The queen averages at a length of with wings measuring long. The major and median workers are both in length, while the minor workers are long. They are brownish-yellow to reddish-orange in color; the head and gaster are darker than the rest of the body.

The larvae are typical of ''Camponotus'' larvae - cylindrical in shape with the head and mouthparts bent at a 90 degree angle from the body.

Distribution and habitat

''Colobopsis schmitzi'' inhabits the hollow tendrils of the plant ''Nepenthes bicalcarata''. It is only found in association with ''N. bicalcarata'', which is endemic to the island of Borneo.

Taxonomy

''Camponotus schmitzi'' is classified in the genus ''Colobopsis'', which was formerly treated as a subgenus of ''Camponotus'', tribe Camponotini, and subfamily Formicinae of the ant family Formicidae. It was first collected by the botanist Jan Pieter Schuitemaker and described by the myrmecologist August Stärcke in 1933 as ''Camponotus schmitzi''.

Myrmecotrophic mutualism

The ant makes its nest in the hollow tendrils of the pitcher plant ''Nepenthes bicalcarata''. This unique animal-plant interaction was noted by Frederick William Burbidge as early as 1880. In 1904, Odoardo Beccari suggested that the ants feed on insects found on and around the plant, but may fall prey to it themselves. In 1990, B. Hölldobler and E. O. Wilson proposed that ''N. bicalcarata'' and ''C. schmitzi'' form a mutually beneficial association. At the time, however, no experimental data existed to support such a hypothesis. A series of observations and experiments carried out in Brunei by Charles Clarke in 1992 and 1998, and by Clarke and Kitching in 1993 and 1995, strongly support the mutualism theory.

The ants feed by descending into the pitcher fluid and retrieving arthropods caught by the plant. The ants seem to ignore smaller insects and only target larger prey items. Hauling food from the pitcher fluid to the peristome, a distance of no more than , may take up to 12 hours. In this way the contents of ''N. bicalcarata'' pitchers is controlled such that organic matter does not accumulate to the point of putrefaction, which can lead to the demise of pitcher infauna (which also appear to benefit the plant) and sometimes the pitcher itself.

The ants seem to favour upper pitchers and rarely colonise lower pitchers. This is likely because terrestrial traps are periodically submerged in water during heavy rains. Flooding of the ants' nest chamber could result in the death of the developing eggs, larvae, and pupae.Clarke, C.M. & C.C. Lee 2004. ''Pitcher Plants of Sarawak''. Natural History Publications (Borneo), Kota Kinabalu.

''C. schmitzi'' nests solely in the tendrils of ''N. bicalcarata'' and rarely ventures onto other plants. The species is completely dependent on ''N. bicalcarata'' for food and domicile.Clarke, C.M. 1997. ''Nepenthes of Borneo''. Natural History Publications (Borneo), Kota Kinabalu. ''N. bicalcarata'', on the other hand, is able to survive and reproduce without the presence of the ants; it is a facultative mutualist. This being the case, there appear to be few mature plants over in height not colonised by ''C. schmitzi''.

John Thompson suggests that ''N. bicalcarata'' may be the only plant species that obtains nutrients through both insect capture and ant-hosting habits.

In addition to Clarke & Kitching (1995), three more theories have been investigated so far to explain the symbiotic relationship between ant and plant. In an exclusion experiment it was shown that plants without ''C. schmitzi'' receive greater herbivory damage, and the ants seem to specifically attack a certain weevil ('' Alcidodes'' sp.) that feeds on pitcher plants. Furthermore, data has been collected that hints to an aggressiveness of ''C. schmitzi'' against prey animals that try to escape from the pitchers, thus enhancing the retention rate. Another mechanism appears to be a host-cleaning behaviour of ''C. schmitzi'': the ants remove debris and mold from the peristome, which thus remains smooth and slippery and has a longer operational lifespan.Thornham, D. G.; Smith, J. M.; Ulmar Grafe, T. & Federle, W. (2012). Setting the trap: cleaning behaviour of ''Colobopsis schmitzi'' ants increases long-term capture efficiency of their pitcher plant host, ''Nepenthes bicalcarata''. ''Functional Ecology'' 26, 11–19.

See also

* ''Nepenthes'' infauna
*Myrmecophyte
*Mutualism (biology)

References

External links

''Camponotus schmitzi''antbase.net"Setting the trap"
- video by Thornham ''et al.'' of the myrmecotrophic mutualism exhibited by ''C. schmitzi'' from YouTube

{{Taxonbar, from=Q1153724

schmitzi
Hymenoptera of Asia
Insects of Borneo
Nepenthes infauna
Insects described in 1933
Endemic fauna of Borneo