http://www.collembola.org/publicat/tripod.htm - Last updated on 2017.02.08 by Frans Janssens
Checklist of the Collembola: Note on a tripod grooming activity in Entomobryomorpha and Symphypleona

Frans Janssens, Department of Biology, University of Antwerp, Antwerp, B-2020, Belgium
Marie Louise Huskens, Opitterkiezel 223 bus 0.1, B-3960, Opitter, Belgium

Abstract

In Entomobryomorpha and Symphypleona, it was observed that specimens used the 3 legs at the same side of the body to form a stable tripod, while using the 3 legs of the other side in a grooming activity.

Introduction

In the long legged Entomobryomorpha and Symphypleona, grooming usually involves using all legs, the everted collophore vesicles and a drop of secretion produced by the mouth or collophore. It was noticed that specimens, while grooming, suddenly lifted all legs of one side of the body. They remained stable on the 3 legs of the other side of the body.

Material and methods

Specimens were collected from the garden of the second author in Opitter, Limburg, Belgium. The specimens were collected with their habitat material. Observations were performed indoors on a staged set-up. Photographs were made using a digital reflex camera Canon EOS 80D. A Canon MP-E 65mm lens was mounted on the camera using a set of Kenko extension tubes (12mm + 20mm + 36mm). Illumination was provided by a Canon Macro Ring Lite MR-14EX and a Falcon Eyes SLP-120LTV LED lamp.

Results

The indoors stage was set-up and after a short period of time the specimens started their grooming activities. Observations of grooming on 3 legs was done in Entomobryidae, Sminthurididae, Katiannidae and Dicyrtomidae.

Entomobryidae
Fig.Em. Entomobrya multifasciata grooming on 3 right legs.
Huskens, M.L. © 2016.12.23

Entomobrya multifasciata grooming on 3 right legs (fig.Em).

Sminthurididae
Fig.Sa1. Sminthurides aquaticus ♀ standing on 6 legs.
Huskens, M.L. © 2016.10.27
Fig.Sa2. Sminthurides aquaticus ♀ standing on 4 legs.
Huskens, M.L. © 2016.10.27
Fig.Sa3. Sminthurides aquaticus ♀ standing on 3 legs.
Huskens, M.L. © 2016.10.27

Sminthurides aquaticus female on 6 to 3 right legs. (fig.Sa1, Sa2, Sa3). In the start position, the specimen is standing still on 6 legs (fig.Sa1). The right proleg and metaleg are placed under the body while the left proleg and mesoleg are lifted from the substrate to clean the left antenna. The left metaleg is still used to stand on (fig.Sa2). Eventually, also the left metaleg is lifted from the substrate (fig.Sa3). All left legs are now involved in cleaning the furca.

Katiannidae

Fig.Sao. Sminthurinus aureus forma ochropus grooming on 3 legs.
Huskens, M.L. © 2016.12.18
Sminthurinus aureus forma ochropus on 3 right legs, handling a drop of saliva using its 3 left legs (fig.Sao).
Fig.St. Sminthurinus trinotatus passing drop of saliva to the metaleg.
Huskens, M.L. © 2016.11.22
Sminthurinus trinotatus on 3 right legs. The body is cleaned using a drop of saliva, that is held at the tip of a leg by the hydrophil outer claw and tenent setae of the footcomplex. The drop of saliva originally is collected by the footcomplex of the left proleg. It is then passed from one leg to the other (fig.St).
Fig.Sr. Sminthurinus reticulatus cleaning the lateral bothriotricha.
Huskens, M.L. © 2016.12.02
Sminthurinus retculatus on 3 right legs. The drop of saliva has been passed to the metaleg, with which the lateral bothriotricha A, B and C are cleaned (fig.Sr).
Fig.K. Gen.1 nov. sp. nov. 0.4mm juvenile, grooming.
David W. © 2017.02.02
Gen.1 nov. sp. nov. juvenile instar of 0.4mm on 3 right legs (fig.K).

Dicyrtomidae

Fig.Dfr. Dicyrtoma fusca var. rufescens cleaning the mucro of the furca.
Huskens, M.L. © 2016.12.14
Dicyrtoma fusca var. rufescens on 3 right legs. The mucro of the furca is cleaned while passing a drop of saliva from the left proleg to the left mesoleg (fig.Dfr). The right proleg, and metaleg, are placed underneath the body, while the body itself is tilted to the right to stay in balance on the 3 right legs.
Fig.Dfv1. Dicyrtoma fusca undescr. var.1 grooming.
Huskens, M.L. © 2017.01.10
Dicyrtoma fusca undescribed var.1 on 3 right legs. The 3 left legs are engaged in a grooming activity (fig.Dfv1). The right proleg and metaleg, are placed underneath the body, while the right mesoleg is placed outside the body. The right legs form as such a stable tripod while the body itself is tilted to the right to stay in balance on the 3 right legs.
Fig.Do. Dicyrtomina ornata juvenile cleaning the furca.
Huskens, M.L. © 2016.11.20
Fig.Do2. Dicyrtomina ornata cleaning the furca.
Huskens, M.L. © 2016.12.20
Dicyrtomina ornata on 3 right legs. The juvenile specimen cleans the furca using the 3 left legs (fig.Do). The right proleg is placed underneath the body, and the body itself is tilted to the right (fig.Do2). The unguis of the right proleg is held in 'knuckle-walking' position. The left proleg and mesoleg interact with a drop of saliva, while the left metaleg is used to keep the body in balance (fig.Do2).
Fig.Cns. Calvatomina nr superba ♂ cleaning the furca.
Huskens, M.L. © 2016.12.16
Calvatomina sp. nov. nr superba male on 3 right legs. The relatively large drop of saliva is handled by all left legs together to clean the furca (fig.Cns).

Discussion

Apparently, the tripod grooming activity is triggered by intense light conditions. Initially, specimens show normal grooming activity at the indoors set-up. Whenever the Falcon Eyes LED Lamp is switched on, specimens suddenly and often show the tripod grooming activity. The Falcon Eyes LED Lamp has a colour temperature of 6500 ° Kelvin, and has a light intensity of 2200 lux at 0.5m (640 lux at 1m; 160 lux at 2m). Given the LED lamp is placed at a distance of 0.25m, the light intensity is about 5000 lux. The Canon flash light has a colour temperature of 5500-6000 ° Kelvin.

Given 6500 ° K corresponds to the colour temperature of daylight, overcast condition (clouds obscuring the sky at least 95%), apparantly the tripod grooming is typically triggered by an increase in light intensity due to changed wheather conditions : such as a change from a cloudy overcast day to a sunny clear sky day.

The tripod grooming was observed only in surface active species that show a positive phototaxis (are attracted to light) : such as species of Entomobryidae, Sminthurididae, Katiannidae and Dicyrtomidae. Tbc.

Conclusion

Tba.

Acknowledgements

We would like to thank David W. for granting us permission to use his image as illustration.

Bibliography