Development and growth of the pelvic fin in the extant coelacanthLatimeria chalumnae

Abstract

The ontogeny of the paired appendages has been extensively studied in lungfishes and tetrapods, but remains poorly known in coelacanths. Recent work has shed light on the anatomy and development of the pectoral fin in Latimeria chalumnae. Yet, information on the development of the pelvic fin and girdle is still lacking. Here, we described the development of the pelvic fin and girdle in Latimeria chalumnae based on 3D reconstructions generated from conventional and X‐ray synchrotron microtomography, as well as MRI acquisitions. As in other jawed vertebrates, the development of the pelvic fin occurs later than that of the pectoral fin in Latimeria. Many elements of the endoskeleton are not yet formed at the earliest stage sampled. The four mesomeres are already formed in the fetus, but only the most proximal radial elements (preaxial radial 0–1) are formed and individualized at this stage. We suggest that all the preaxial radial elements in the pelvic and pectoral fin of Latimeria are formed through the fragmentation of the mesomeres. We document the progressive ossification of the pelvic girdle, and the presence of a trabecular system in the adult. This trabecular system likely reinforces the cartilaginous girdle to resist the muscle forces exerted during locomotion. Finally, the presence of a preaxial element in contact with the pelvic girdle from the earliest stage of development onward questions the mono‐basal condition of the pelvic fin in Latimeria. However, the particular shape of the mesomeres may explain the presence of this element in contact with the girdle.

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

“…It remains unresolved where gravid females give birth and at which depth neonatal coelacanths reside, although based on a record dive unusually performed at daytime of a pregnant female tracked with acoustic telemetry to 698 m [4], it has been speculated that coelacanths may be born deeper than their usual habitat [31]. Late-term (CCC 162.1-26) and a juvenile coelacanth (CCC 94) are represented in museum collections [43], and some have undergone non-invasive imaging for morphometric and ontogenetic purposes [18,79]. It would be of interest to employ quantitative procedures as described here and use bone mineral calibrated micro-CT and lipid calibrated micro-MRI data to model buoyancy at different depths for these smaller specimens.…”

Life history and ossification patterns inMiguashaia bureauireveal the early evolution of osteogenesis in coelacanths

“…The retention of calcified cartilage in adult individuals of Miguashaia bureaui suggests a relatively modest endochondral ossification and slow epiphyseal growth. A poor endochondral ossification also occurs in the mainly cartilaginous paired fins of Latimeria chalumnae ( Francillon et al, 1975 ; Mansuit et al, 2019 , 2021 ), where the thin bony trabeculae show evidence of spheritic mineralized cartilage as well ( Figs. 5I – 5K ).…”

“…In the extant Latimeria chalumnae , the endoskeleton shows a reduced ossification rate, especially in the neurocranium ( Millot & Anthony, 1958 ; Forey, 1998 ; Dutel et al, 2019 ). Similarly, the paired (pectoral and pelvic) and median (anterior and posterior dorsal, anal, and caudal) fins are essentially made of cartilage with a limited contribution of endochondral ossification ( Francillon et al, 1975 ; Mansuit et al, 2019 , 2021 ). Other bony tissues have been histologically surveyed, such as the mineralized plates surrounding the lung in extinct ( Brito et al, 2010 ) and extant taxa ( Cupello et al, 2017a , 2017b ; Meunier et al, 2021 ).…”

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).…”