Acta Ichthyologica et Piscatoria 41(3): 223-227, doi: 10.3750/AIP2011.41.3.10
The structure and the embryogenetic role of eggs and egg membranes of Ancistrus dolichopterus (Actinopterygii: Siluriformes: Loricariidae)
expand article infoA. Brysiewicz, J. Szulc, K. Formicki, A. Tański, A. Korzelecka Orkisz
Open Access
Background. Bushymouth catfish, Ancistrus dolichopterus Kner, 1854 has raised interest among ornamental fish keepers. Its natural populations are seriously threatened by fishing pressure. The reproduction of this species is difficult to perform (in captivity) and to observe because it occurs at night in shaded areas—most frequently in hiding spots. This study was intended to describe the eggs and their membranes of bushymouth catfish known to provide a parental care during egg development. A special focus of this study was directed towards the microstructure of membranes protecting life cells, and known to be impacted by the environmental conditions the egg morphometric analysis, as well as embryonic development. Materials and methods. The material for the study consisted of the eggs of 3 pairs of bushymouth catfish obtained as a result of their spawning in an aquarium culture. The fertilised eggs were incubated at a constant temperature of 24 ± 0.2°C in water of hardness 17°n, pH 6.5. The utrastructural details of egg membranes were viewed under scanning electron microscope (SEM). Also egg membrane resistance and egg diameters were determined. Images of eggs and newly hatched larvae were measured and analysed. Results. Average egg diameter was 2.98 mm and surface-to-volume ratio (S/V) was 2.01. Internal and external layers of egg membranes showed various structure peculiarities in the surface microstructure of studied eggs. We found that in comparison to other fish the thickness of egg membrane in the bushymouth catfish was high (26.05 µm). External layer had no pores leading to external radial zone (zona radiata externa), however, some specific honeycomb-like formations were visible. The resistance of the egg membrane was 54 ± 1.7 g and the egg mass was 0.017 ± 0.0001 g. The correlation between the resistance and the thickness of the egg membranes was not high, but the correlation between the mass and the resistance  was significant. Conclusion. The presently reported study constitutes a contribution to the knowledge of the eggs and embryonic development of bushymouth catfish, and its biological sense, emphasizing the morphophysiological differences between this species—living under, specific, diversified ecological conditions. Such knowledge on early developmental stages may be prove helpful in the fish culturist’s practice of this threatened and interesting species.
Ancistrus, egg membranes, eggs, aquarium