Adaptations to the brood care paradigm in the shell-dwelling cichlid Lamprologus ocellatus

Parker, Ash (2025): Adaptations to the brood care paradigm in the shell-dwelling cichlid Lamprologus ocellatus. Dissertation, LMU München: Fakultät für Biologie

Abstract

The evolution of parental care in animals is influenced by ecological, evolutionary, and environmental factors. Birds and mammals are typically studied for their elaborate and prolonged care, but systems where parental care evolved independently, such as in cichlids, offer valuable insights into the diversity of these behaviours. Cichlids exhibit a wide range of parental strategies, making them an excellent model for studying the evolution of parental care. This thesis focuses on Lamprologus ocellatus, a small shell-dwelling cichlid with a unique brood care strategy where females lay eggs in abandoned snail shells, providing a protected environment until the larvae become free-swimming. I developed a laboratory paradigm to observe and analyse interactions between mother and larvae within 3D-printed 'window' shells. This approach enabled detailed monitoring of the spatial distribution of fry and mother, and continuous recording of parent-offspring interactions over an 11-day period, from fertilisation to late-larval stages. The mother actively cares for the offspring, leading up to their emergence from the shell at 9 days post-fertilisation. Remarkably, this emergence time coincides with a switch in phototaxis behaviour from dark preference to seeking light in the larvae. We were able to delay larvae emergence by using a foster mother whose biological offspring were younger, causing a conflict between the larvae’s natural emergence time and the foster mother’s intrinsic timer. This study shows that larval and maternal behaviours in L. ocellatus are governed by independent internal timing mechanisms, usually synchronised but can conflict through experimental manipulations. Comparing the brood care strategies of shell-dwellers like L. ocellatus to other parental care strategies in Lake Tanganyika—ancestral substrate brooding and derived mouthbrooding—I found shell-dwellers have adapted to a unique niche, exhibiting parallels with both groups. Convergent strategies shared with mouthbrooders, such as mating strategies and clutch size constraint, may arise from larvae growing up in confined spaces. Conversely, traits reminiscent of substrate brooders, such as smaller egg sizes, larval anatomy and behaviours, and maternal interactions highlight the influence of evolutionary history. In conclusion, this thesis provides the first comprehensive delineation of the brood care paradigm of shell-dwelling cichlids, shedding light on the behavioural adaptations and development of L. ocellatus. By introducing L. ocellatus as a novel model organism, this research offers valuable insights into the mechanisms of parent-offspring coordination during brood care, contributing to our understanding of the evolution of parental care in animals.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Shell-dwellers, parental care, cichlids, Lamprologus ocellatus, inside shell, adaptation
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie
• Fakultäten: Fakultät für Biologie
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 4. Februar 2025
• 1. Bericht­erstatter:in: Baier, Herwig