Vision in the grass goby, Zosterisessor ophiocephalus (Teleostei, Gobiidae): A morphological and behavioural study

Abstract

The visual abilities of Zosterisessor ophiocephalus, an ambushing predator inhabiting the intertidal seagrass meadows of lagoons, were studied by morphological and behavioural methods. In its retina, a high number of rods, double and single cones packed in a square mosaic were found, together with the retinomotor response involving the pigment granules and both kinds of photoreceptors. The retinal topography was made by analysing the cone density and density of cells in the ganglion cell layer, and it revealed the area centralis in the dorso‐temporal region of the retina. No influence of different light intensities (2.4 pimol m^‐2 s^‐1, 0.7 μmol m^‐2 s^‐1 and 0.1 μmol m^‐2 s^‐1) on its visual abilities for prey detection was found by comparing the detection and capture efficiencies and the detection and capture distance. A preference for larger food targets was observed. Two capture strategies are described: fast direct and slower hopping capture, the latter exhibited with higher frequency under dim light. Histo‐logical visual acuity was 7’ and behavioural visual acuity was 15’. The morphological and behavioural studies showed that Z. ophiocephalus can use vision for feeding in bright and dim light conditions, but it probably feeds more at dusk to avoid predators.

Keywords:

• Retina
• Retinal topography
• Light intensity and behaviour
• Visual acuity
• Lagoon

Notes

Riserva Naturale Marina di Miramare ‐ Centro di Eto‐ecologia ‘ Viale Miramare 349, 1–34100 Trieste (Italy)