Biology subjects

Heath-Heckman, E. A. C.

Publications and source records attributed to Heath-Heckman, E. A. C..

3 recordsLinked to original sources

bioRxiv2026

The Neuroanatomy of the Hawaiian Bobtail Squid Juvenile Bacterial Light Organ

BackgroundRecent studies have shown that symbiotic bacteria can have drastic effects on host neurobiology, but few simple, accessible models currently exist in which to study these interactions. Hawaiian bobtail squid (Euprymna scolopes) participate in a binary symbiosis with the bacterium Vibrio fischeri, a population of which resides in a specialized hindgut-derived organ called the light organ. Upon colonization by V. fischeri, the light organ undergoes transcriptional changes that suggest neurons are among the cell types impacted by the initiation of symbiosis, but the nascent light organs innervation has remained uncharacterized. ResultsThe light organ-associated nervous system (LONS) in hatchling E. scolopes is a remarkably complex segment of the peripheral nervous system. The LONS is largely plexiform and originates from two primary nerves connected by a local commissure. The abundance of synapsin-like immunoreactivity indicates that the lobe plexus is highly interconnected. We also highlight a small number of serotonin-like immunoreactive neurites innervating the anterior appendages that are poised to be directly impacted by symbiont-driven post-embryonic development. Finally, we present evidence that a limited but morphologically diverse population of neurons reside within the light organ and are often located near internal symbiont-interacting structures. ConclusionOur results show that the LONS is structurally and molecularly complex and exhibits traits characteristic of an immature nervous system, suggesting that it may undergo substantial post-embryonic refinement. This initial characterization of the LONS provides a foundation from which to investigate how beneficial bacterial symbionts affect host peripheral neurobiology in a tractable model system.

neuroscience↗

bioRxiv2024

Acceleration of genome rearrangement in clitellate annelids

Comparisons of multiple metazoan genomes have revealed the existence of ancestral linkage groups (ALGs), genomic scaffolds sharing sets of orthologous genes that have been inherited from ancestral animals for hundreds of millions of years (Simakov et al. 2022; Schultz et al. 2023) These ALGs have persisted across major animal taxa including Cnidaria, Deuterostomia, Ecdysozoa and Spiralia. Notwithstanding this general trend of chromosome-scale conservation, ALGs have been obliterated by extensive genome rearrangements in certain groups, most notably including Clitellata (oligochaetes and leeches), a group of easily overlooked invertebrates that is of tremendous ecological, agricultural and economic importance (Charles 2019; Barrett 2016). To further investigate these rearrangements, we have undertaken a comparison of 12 clitellate genomes (including four newly sequenced species) and 11 outgroup representatives. We show that these rearrangements began at the base of the Clitellata (rather than progressing gradually throughout polychaete annelids), that the inter-chromosomal rearrangements continue in several clitellate lineages and that these events have substantially shaped the evolution of the otherwise highly conserved Hox cluster.

evolutionary biology↗

bioRxiv2018

Behavioral Analysis of Substrate Texture Preference in a Leech, Helobdella austinensis

Leeches in the wild are often found on smooth surfaces, such as vegetation, smooth rocks or human artifacts such as bottles and cans, thus exhibiting what appears to be a \"substrate texture preference behavior\". Here, we have reproduced this behavior under controlled circumstances, by allowing leeches to step about freely on a range of silicon carbide sandpaper substrates. To begin to understand the neural mechanisms underlying this texture preference behavior, we have determined relevant parameters of leech behavior both on uniform substrates of varying textures, and in a behavior choice paradigm in which the leech is confronted with a choice between rougher and smoother substrate textures at each step. We tested two non-exclusive mechanisms which could produce substrate texture preference: 1) a Diffusion Trap mechanism, in which a leech is more likely to stop moving on a smooth surface than on a rough one, and; 2) an Anterior Choice mechanism, in which a leech is more likely to attach its front sucker (prerequisite for taking a step) to a smooth surface than to a rough one. We propose that both mechanisms contribute to the texture preference exhibited by leeches.

animal behavior and cognition↗