254-2 Middle Jurassic Hydroid-Serpulid Symbiosis in the light of Computed Microtomography

Session: Recent Advances in Fossil Imaging

Presenting Author:

Authors:

Abstract:

The study of the Middle Jurassic Protulophila gestroi bioclaustrated within Propomatoceros lumbricalis tubes provides a rare and valuable insight into the nature of syn vivo interaction and the paleoecological conditions that shaped this symbiosis. Fossils spanning the Bajocian-Callovian were derived from four localities representing different paleoenvironments of the Polish Basin. The hydroids are preserved within the external part of the serpulid tubes in the process of bioclaustration as a result of syn vivo incorporation due to the worm’s skeletal overgrowth – their external appearance is manifested by small apertures and surrounding bulges scattered over the serpulid tube. The virtual sections made using computed microtomography (micro-CT) and volumetrically rendered images supplied significant results about the hydroid internal morphology. The traces left by the decomposed soft-bodied colonies are represented by networks of thin, branching, and anastomosing stolons and elongated cavities after polyp chambers, reflecting casts of zooids.

The morphometric comparative analyses were accomplished in terms of hydroid individuals’ variability within the same serpulid specimens, and across paleoenvironments. Comparisons of the external and internal morphology of Protulophila gestroi within the same serpulid specimens allowed for the recognition of the strong reciprocal dependence. The morphological disparity of the apertures correlated with different depths of the colonies’ incorporation, suggesting a significant impact of host biomineralization on the final external appearance of the fossil. In turn, the diversity of Protulophila gestroi among different hosts indicates that, in addition to host-symbiont dynamics, these relationships were also shaped involving other behavioral and environmental variables, such as e.g., nutrient availability or water dynamics.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7998

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