Miniaturisation in fishes: evolutionary and ecological perspectives

Christopher Goatley, Nic Bury, Phillip Fenberg, OES; James Maclaine, NHM

Bony fishes are the most diverse group of vertebrates in terms of both species richness and body sizes, with over 30,000 species ranging from 8mm to 10m long and from <0.001g to 2,300kg. Large fishes may seem charismatic, but the smallest fishes in ecosystems may be the most important from ecological and biodiversity perspectives. For example, on coral reefs, the average size of adult fishes is just 45mm long, yet these small fishes form the foundations of critical food webs which support ecosystem functions [1]. These “miniaturised” fish species are found worldwide, among numerous phylogenetic lineages and ecosystems, from tropical river systems to the deep sea. Although widespread among fishes, the evolution of miniaturisation appears to be a relatively demanding and recent process [1,2]. This project will explore the benefits and costs of miniaturisation by using 2D and 3D micro-CT data to compare the functional morphologies of miniature fishes with their larger relatives. By collaborating with the Natural History Museum and using their collections, it will be possible to apply this technique across multiple extant and fossil lineages, allowing us to reveal how miniaturisation has affected the ecological roles of fishes and how it may have shaped their evolution.



This project will use multiple techniques and technologies to explore the functional implications of miniaturisation in fishes. First, the benefits, costs and potential limits of miniaturisation will be evaluated using a comparative morphological framework. Within broad taxonomic groups, several key morphological traits associated with feeding, sensory systems and locomotion will be compared using 3D models, linear measurements and geometric morphometrics. 3D models of fishes will be sourced from online repositories (e.g. Morphosource) and by conducting scans of specimens from the Natural History Museum and other international museums using the University of Southampton’s µ-VIS X-ray Imaging Centre. Morphological analyses will be conducted using new, open-source software [3], which allows rapid collection and analysis of data from large samples. The project will then source comparable data from fossil fish assemblages, including Eocene (~50 million year old) reef fish faunas from Monte Bolca, Italy [2]. The morphology of the fossil fishes will be analysed and placed within a comparative phylogenetic framework to provide information on the evolution of morphological traits associated with miniaturisation in fishes.



The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the School of Ocean and Earth Sciences. Specific training will


- conducting micro-CT scans at the University of Southampton’s µ-VIS X-ray Imaging Centre.

- reconstructing and segmenting 3D models from micro-CT data.

- collecting and analysing morphological data using multivariate linear and geometric morphometric analyses.

- handling preserved and fresh vertebrate specimens from museums and/or field collections.

- identification of broad fish taxa and the morphological traits that characterise them.

- creating and interpreting phylogenies and mapping fossil and extant traits onto phylogenetic frameworks to investigate evolutionary processes.

- science communication to the public through presentations, outreach and media releases, and to the scientific community through conference presentations and preparation of scientific manuscripts.

Eligibility & Funding Details: 

Please see for details.


Background Reading: 

[1] Brandl SJ, Goatley CHR, Bellwood DR, Tornabene L (2018) The hidden half: ecology and evolution of cryptobenthic fishes on coral reefs. Biological Reviews 93:1846-1873

[2] Bellwood DR, Goatley CHR, Bellwood O (2016) The evolution of fishes and corals on reefs: form, function and interdependence. Biological Reviews 92:878-901

[3] Rolfe S, Pieper S, Porto A, Diamond K, Winchester J, Shan S, Kirveslahti H, Boyer D, Summers A, Maga AM (2021) SlicerMorph: An open and extensible platform to retrieve, visualize and analyse 3D morphology. Methods in Ecology and Evolution 12:1816-1826