Buoyancy and hydrostatic balance in a West Indian Ocean coelacanth Latimeria chalumnae

Abstract

Background Buoyancy and balance are important parameters for slow-moving, low-metabolic, aquatic organisms. The extant coelacanths have among the lowest metabolic rates of any living vertebrate and can afford little energy to keep station. Previous observations on living coelacanths support the hypothesis that the coelacanth is neutrally buoyant and in close-to-perfect hydrostatic balance. However, precise measurements of buoyancy and balance at different depths have never been made. Results Here we show, using non-invasive imaging, that buoyancy of the coelacanth closely matches its depth distribution. We found that the lipid-filled fatty organ is well suited to support neutral buoyancy, and due to a close-to-perfect hydrostatic balance, simple maneuvers of fins can cause a considerable shift in torque around the pitch axis allowing the coelacanth to assume different body orientations with little physical effort. Conclusions Our results demonstrate a close match between tissue composition, depth range and behavior, and our collection-based approach could be used to predict depth range of less well-studied coelacanth life stages as well as of deep sea fishes in general.

Interactive three-dimensional atlas of the mineralized skeleton of the sand tiger shark Carcharias taurus

“…In more recent times, non-invasive imaging modalities such as X-ray computed tomography (CT) have become common methods for investigating internal anatomy in medical practices [6]. Similarly, CT can be applied to zoological specimens to rapidly generate three-dimensional representations of dense anatomical structures in detail that are able to rival that of more traditional anatomical illustrations based on dissection and allow for various quantitative measurements to be obtained [7][8][9].…”

Reconstructing an ancient fish: Three‐dimensional skeletal restoration of the head of Mawsonia (Sarcopterygii, Actinistia) using CT scan, and an adjusted model for body size estimation in fossil coelacanths

“…However, virtual imaging techniques have been barely used to study fossil coelacanths, featuring the recent description of the Triassic genus Foreyia from Switzerland (Cavin et al, 2017), some on-going studies involving the Mesozoic genera Whiteia and Libys (Gausden, 2022;Manuelli & Cavin, 2022) and a new unnamed Carboniferous genus (Mondéjar Fernández et al, 2022). By contrast, our knowledge of the anatomy and biomechanics of the living coelacanth Latimeria chalumnae has greatly benefited from virtual imaging techniques (e.g., Cloutier et al, 1988;Cupello et al, 2015;Cupello, Meunier, Herbin, Janvier, et al, 2017;Dutel et al, 2013Dutel et al, , 2014Dutel, Herbin, Clément, & Herrel, 2015;Johnston, 2022;Lauridsen et al, 2022;Mansuit et al, 2019Mansuit et al, , 2020Manuelli et al, 2023;Schulzte & Cloutier, 1991).…”