SeaCACHE - Seawater Chemistry And CHondrichthyan Evolution

Lead Research Organisation: The Natural History Museum
Department Name: Earth Sciences

Abstract

Chondrichthyans (sharks, rays and holocephalans) have an extremely rich and long fossil record dominated by teeth and dental plates. These mineralized structures provide a deep-time, evolutionary, perspective of the group. Recently, a hypermineralized tissue called whitlockin, containing a biomineral rich in magnesium (whitlockite), has been discovered in holocephalan dental plates and in living shark body-denticles and teeth. This unusual tissue potentially provides a strengthening function, but when did whitlockin first appear in the evolutionary history of chondrichthyans? It is known that the ratio of magnesium:calcium (Mg/Ca) in seawater has shifted through Earth history, creating intervals of 'calcite' seas and 'aragonite' seas (lower and higher Mg/Ca ratios respectively). These changes, along with temperature, apparently influenced the uptake of particular elements and minerals into the carbonate skeletons of invertebrate animals. Have marine vertebrate skeletons been shaped in a similar way? Or is their skeletal mineralization independent of the surrounding environment?

The SeaCACHE project will test these possibilities in this critical group of marine animals. There are three main aims: (1) to analyze the dentitions of a broad range of living and, for the first time, fossil chondrichthyans from the Devonian to the present day, to test for the presence of whitlockin via a combination of histological and chemical analysis; (2) to examine the relationship between the Mg/Ca content of seawater, seawater temperature, and the presence of whitlockite in chondrichthyans in modern and ancient ecosystems; and (3) to update the phylogeny of chondrichthyans as a whole to elucidate rates of evolution of whitlockite. During this project, the research fellow will gain experience in chemical, palaeonvironmental and phylogenetic analyses, in open science practices, in natural history collection management, and in other transferable skills that will substantially improve their future career as an independent researcher.
 
Description We have found the first evidence of the mineral whitlockite in fossil holocephalan dental plates
Exploitation Route It's too early to say as the award is still active
Sectors Environment

Culture

Heritage

Museums and Collections

 
Description Christmas at the Museum: Santa Jaws 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact An afterhours event during Christmas at the museum, I had a selection of the different dentitions from extant and extinct representatives of the most important chondrichthyan groups (sharks, rays and chimeras) from the Devonian until recent times. This allowed to show to the general public the great variability and adaptability of this group of marine organisms have shown, and also to introduce some biological concepts such as convergent evolution, mass extinction and heterodoncy.
Year(s) Of Engagement Activity 2024
 
Description Postdoc Celebration Days at the museum 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact In conjunction with the meeting of the Museum's Science Advisory Committee on 29 January 2025, we would like to celebrate and profile the amazing research undertaken and often led by early career post-doctoral researchers. The purpose is three-fold: (i) to reveal more about NHM science, (ii) to provide an opportunity for postdocs to interact with senior external scientists keen to support and develop NHM science, and (iii) for postdocs to have a forum around which to team up.
Year(s) Of Engagement Activity 2024