Adaptations for nocturnal vision in insect apposition eyes

Research output: ThesisDoctoral Thesis (compilation)

Abstract

Due to our own preference for bright light, we tend to forget that many insects are active in very dim light. The reasons for nocturnal activity are most easily seen in tropical areas of the world, where animals face severe competition for food and nocturnal insects are able to forage in a climate of reduced competition and predation.

Generally nocturnal insects possess superposition compound eyes. This eye design is truly optimized for dim light as photons can be gathered through large apertures comprised of hundreds of lenses. In apposition eyes, on the other hand, the aperture consists of a single lens resulting in a poor photon catch and unreliable vision in dim light. Apposition eyes are therefore typically found in day-active insects and according to theoretical calculations should render bees blind by mid dusk.

Nevertheless, the tropical bee Megalopta genalis and the wasp Apoica pallens have managed the transition to a nocturnal lifestyle while retaining their highly unsuitable apposition eye design. Far from being blind, these bees and wasps forage at extremely low light intensities. Moreover, M. genalis is the first insect shown to use landmark navigation at light intensities less than starlight. How do their apposition eyes permit such complex visual behaviour in so little light?

Optical adaptations can significantly enhance sensitivity in apposition eyes. In bees and wasps, the major effect comes from their extremely wide photoreceptors, which are able to trap light reaching the eye from a large visual angle. These optical adaptations lead to a 30-fold increase in sensitivity compared to diurnal bees and wasps. This however is not sufficient for the 8 log units difference in light intensity between day and night.

Our hypothesis is that neural adaptations in the form of spatial and temporal summation must be involved. By means of spatial summation the eyes could sum signals from large groups of visual units (ommatidia), in order to improve sensitivity at the cost of coarser spatial resolution. In nocturnal bees, spatial summation could be mediated via their wide laterally-spreading first-order interneurons (L-fibres) present in the first optic ganglion (lamina). These L-fibres have significantly larger dendritic fields than equivalent neurons in diurnal bees and the potential to sum photons from up to 18 visual units. Theoretical modelling further supports this hypothesis, as the optimal dendritic field size predicted by the model agrees well with the anatomical data.

Details

Authors
  • Birgit Greiner
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Zoology

Keywords

  • temporal and spatial summation, optical and neural adaptations, theoretical modelling., Djurs anatomi och morfologi, Zoologi, dim light, vision, landmark navigation, nocturnal bees and wasps, Zoology, Animal anatomy, animal morphology
Original languageEnglish
QualificationDoctor
Awarding Institution
Supervisors/Assistant supervisor
  • Warrant, Eric J., Supervisor, External person
Award date2005 Dec 16
Publisher
  • Lund Unversity, Department of Cell and Organism Biology
Print ISBNs91-85067-22-9
Publication statusPublished - 2005
Publication categoryResearch

Bibliographic note

Defence details Date: 2005-12-16 Time: 10:00 Place: Högtidssalen, Zoologihuset, Helgonav. 3, Lund External reviewer(s) Name: Meinertzhagen, Ian A. Title: Prof. Affiliation: Life Sciences Centre, Dalhousie University, Halifax, Canada. --- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Zoology (Closed 2011) (011012000)

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Related research output

Greiner, B., Ribi, WA., Wcislo, WT. & Eric Warrant, 2004, In : Cell and Tissue Research. 318, 2, p. 429-437

Research output: Contribution to journalArticle

Greiner, B., Ribi, WA. & Eric Warrant, 2004, In : Cell and Tissue Research. 316, 3, p. 377-390

Research output: Contribution to journalArticle

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