mgr Isabella Leonhard

@article{Legaki2024b,

title = {Dentex maroccanus Valenciennes, 1830 Otolith Morphology, Age, and Growth in the Aegean Sea (E. Mediterranean)},

author = {Aglaia Legaki and Isabella Leonhard and Chryssi Mytilineou and Aikaterini Anastasopoulou},

doi = {10.3390/ani14213151},

issn = {2076-2615},

year  = {2024},

date = {2024-11-00},

urldate = {2024-11-00},

journal = {Animals},

volume = {14},

number = {21},

publisher = {MDPI AG},

abstract = {<jats:p>Otoliths are important structures for balance and hearing of fish and constitute a useful tool in fisheries science. This study provides, for the first time in the Mediterranean, information on the otolith morphometrics of Dentex maroccanus, collected from the South Aegean Sea, and enriches the existing information on its age and growth by sex. The otolith shape variables examined showed a more circular to square otolith shape, related to the body size. Significant differences between sexes were detected for the otolith Area, Diameter, Perimeter, and Radius. Exponential regressions were used to examine the relationship of the otolith variables with total body length, from which five showed a strong correlation (Diameter, Width, Radius, Area, and Perimeter). The eviscerated weight–length relationship exhibited an isometric growth for both sexes, whereas when total weight was applied, a positive allometric growth was found for females. Sagittal otolith readings revealed four age groups for females and five for males. A Bhattacharya method was used for age validation. Von Bertalanffy growth parameters were as follows: L∞ = 23.08, k = 0.27, t0 = −1.93 for females and L∞ = 24.07, k = 0.24, t0 = −2.26 for males. This research offers valuable biological information for Dentex maroccanus useful in fisheries science.</jats:p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Shirley2024,

title = {Increasing control over biomineralization in conodont evolution},

author = {Bryan Shirley and Isabella Leonhard and Duncan J. E. Murdock and John Repetski and Przemysław Świś and Michel Bestmann and Pat Trimby and Markus Ohl and Oliver Plümper and Helen E. King and Emilia Jarochowska},

url = {https://www.nature.com/articles/s41467-024-49526-0},

doi = {10.1038/s41467-024-49526-0},

issn = {2041-1723},

year  = {2024},

date = {2024-06-20},

urldate = {2024-06-20},

journal = {Nature Communications},

volume = {15},

issue = {1},

pages = {1-13},

publisher = {Nature Publishing Group},

abstract = {Vertebrates use the phosphate mineral apatite in their skeletons, which allowed them to develop tissues such as enamel, characterized by an outstanding combination of hardness and elasticity. It has been hypothesized that the evolution of the earliest vertebrate skeletal tissues, found in the teeth of the extinct group of conodonts, was driven by adaptation to dental function. We test this hypothesis quantitatively and demonstrate that the crystallographic order increased throughout the early evolution of conodont teeth in parallel with morphological adaptation to food processing. With the c-axes of apatite crystals oriented perpendicular to the functional feeding surfaces, the strongest resistance to uniaxial compressional stress is conferred along the long axes of denticles. Our results support increasing control over biomineralization in the first skeletonized vertebrates and allow us to test models of functional morphology and material properties across conodont dental diversity. Conodonts, early vertebrates, are thought to have evolved complex tooth tissue as an adaptation for feeding. Here, the authors use Electron Backscatter Diffraction to show increasing dental crystallographic order through conodont evolution, in parallel with dietary adaptations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{leonhard2023addressing,

title = {Addressing challenges in marine conservation with fish otoliths and their death assemblages},

author = {Isabella Leonhard and Konstantina Agiadi},

url = {https://www.lyellcollection.org/doi/10.1144/SP529-2022-132},

doi = {10.1144/SP529-2022-132},

year  = {2023},

date = {2023-02-16},

urldate = {2023-02-16},

journal = {Geological Society, London, Special Publications},

volume = {529},

number = {1},

publisher = {The Geological Society of London},

abstract = {Otolith death assemblages provide a valuable source of biological and ecological information that can help address three main problems in marine conservation: a) the lack of pre-industrial, pre-human-impact baselines for evaluating change; b) the inefficiency of survey methods for recording small and cryptic fish species; and c) the absence of long-term data on environmental change impacts on marine ecosystems and fishes. We review here the current knowledge on the formation and preservation of otoliths and their death assemblages, and the methods to obtain, date and analyse them in order to detect changes in the species traits and ecology, the fish population structure and the palaeoceanographic shifts that drove them.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Leonhard2021,

title = {Growth and feeding ecology of coniform conodonts},

author = {Isabella Leonhard and Bryan Shirley and Duncan J E Murdock and John Repetski and Emilia Jarochowska},

doi = {10.7717/peerj.12505},

issn = {2167-8359},

year  = {2021},

date = {2021-12-15},

journal = {PeerJ},

volume = {9},

pages = {e12505},

abstract = {<p> Conodonts were the first vertebrates to develop mineralized dental tools, known as elements. Recent research suggests that conodonts were macrophagous predators and/or scavengers but we do not know how this feeding habit emerged in the earliest coniform conodonts, since most studies focus on the derived, ‘complex’ conodonts. Previous modelling of element position and mechanical properties indicate they were capable of food processing. A direct test would be provided through evidence of <italic>in vivo</italic> element crown tissue damage or through <italic>in vivo</italic> incorporated chemical proxies for a shift in their trophic position during ontogeny. Here we focus on coniform elements from two conodont taxa, the phylogenetically primitive <italic>Proconodontus muelleri</italic> Miller, 1969 from the late Cambrian and the more derived <italic>Panderodus equicostatus</italic> Rhodes, 1954 from the Silurian. Proposing that this extremely small sample is, however, representative for these taxa, we aim to describe in detail the growth of an element from each of these taxa in order to the test the following hypotheses: (1) <italic>Panderodus</italic> and <italic>Proconodontus</italic> processed hard food, which led to damage of their elements consistent with prey capture function; and (2) both genera shifted towards higher trophic levels during ontogeny. We employed backscatter electron (BSE) imaging, energy-dispersive X-ray spectroscopy (EDX) and synchrotron radiation X-ray tomographic microscopy (SRXTM) to identify growth increments, wear and damage surfaces, and the Sr/Ca ratio in bioapatite as a proxy for the trophic position. Using these data, we can identify whether they exhibit determinate or indeterminate growth and whether both species followed linear or allometric growth dynamics. Growth increments (27 in <italic>Pa. equicostatus</italic> and 58 in <italic>Pr. muelleri</italic> ) were formed in bundles of 4–7 increments in <italic>Pa. equicostatus</italic> and 7–9 in <italic>Pr. muelleri</italic> . We interpret the bundles as analogous to Retzius periodicity in vertebrate teeth. Based on applied optimal resource allocation models, internal periodicity might explain indeterminate growth in both species. They also allow us to interpret the almost linear growth of both individuals as an indicator that there was no size-dependent increase in mortality in the ecosystems where they lived <italic>e.g</italic> ., as would be the case in the presence of larger predators. Our findings show that periodic growth was present in early conodonts and preceded tissue repair in response to wear and damage. We found no microwear and the Sr/Ca ratio, and therefore the trophic position, did not change substantially during the lifetimes of either individual. Trophic ecology of coniform conodonts differed from the predatory and/or scavenger lifestyle documented for “complex” conodonts. We propose that conodonts adapted their life histories to top-down controlled ecosystems during the Nekton Revolution. </p>},

keywords = {},

pubstate = {published},

tppubtype = {article}

}