Morphological and physiological characteristics of dermal photoreceptors in Lymnaea stagnalis

Localization of Cholecystokinin/Sulfakinin Neuropeptides in Biomphalaria glabrata, an Intermediate Host for Schistosomiasis

Snails belonging to the genus Biomphalaria serve as obligatory intermediate hosts for the trematode Schistosoma mansoni, the causative agent for the most widespread form of schistosomiasis. The simpler nervous systems of gastropod molluscs, such as Biomphalaria, provide advantageous models for investigating neural responses to infection at the cellular and network levels. The present study examined neuropeptides related to cholecystokinin (CCK), a major multifunctional regulator of central nervous system (CNS) function in mammals. A neural transcriptome generated from the CNS of Biomphalaria alexandrina included a transcript encoding two CCK-related peptides, designated Balex-CCK1 (pEGEWSYDY(SO 3 H)GLGGGRF-NH2) and Balex-CCK2 (NYGDY(SO 3 H)GIGGGRF-NH2). Peptide expression was examined in Biomphalaria glabrata at the mRNA level using the hybridization chain reaction (HCR) protocol and at the protein level using an antibody against Balex-CCK1. Expression was detected in 60-70 neurons distributed throughout the CNS, as well as in profuse fiber systems connecting the ganglia and projecting to the periphery. CCK-like immunoreactive (CCKli) fibers were also observed on organs associated with the cardiorespiratory (nephridium, mantle, gill) and male reproductive systems. A comparison of mRNA and peptide localization suggested that CCK expression could be regulated at the level of translation. A potential role of these peptides in mediating responses to infection by larval schistosomes is discussed.

Functional characterization of optic photoreception in Lymnaea stagnalis

Optic photoreception is a critical function for animal survival. Across the evolutionary spectrum, diverse animal models have been used to investigate visual system function and potential mechanisms under physiological or pathophysiological states. However less is known on photoreceptive behaviors and retinal processing in invertebrates, especially molluscs. This study focuses on the freshwater pond snail, Lymnaea stagnalis (L. stagnalis), to explore its visual function and underlying mechanisms. Using anatomical and histological approaches we characterized the L. stagnalis eye structure and demonstrated structural connections and retinal rhodopsin-positive sensory cells potentially critical for phototransduction. To assess the snail phototactic responses, we developed a new neurobehavioral protocol and employed DeepLabCut to track and quantify animal locomotion. We demonstrated that L. stagnalis exhibits a positive locomotory response to intense focal light and has diverse photo-locomotory responses. Further, we conducted phylogenetic and protein structure analyses and demonstrated that L. stagnalis has a unique repertoire of both vertebrate and invertebrate phototransduction genes. Further characterization of a rhodopsin-like gene identified unique characteristics compared to other mollusks and vertebrates, suggesting different mechanisms of phototransduction. Taken together, our work establishes L. stagnalis as a model organism for studying optic photoreception, offering new insights into the evolution and diversity of visual function across animal species.

Slowly seeing the light: an integrative review on ecological light pollution as a potential threat for mollusks

Seasonal changes in the natural light condition play a pivotal role in the regulation of many biological processes in organisms. Disruption of this natural condition via the growing loss of darkness as a result of anthropogenic light pollution has been linked to species-wide shifts in behavioral and physiological traits. This review starts with a brief overview of the definition of light pollution and the most recent insights into the perception of light. We then go on to review the evidence for some adverse effects of ecological light pollution on different groups of animals and will focus on mollusks. Taken together, the available evidence suggests a critical role for light pollution as a recent, growing threat to the regulation of various biological processes in these animals, with the potential to disrupt ecosystem stability. The latter indicates that ecological light pollution is an environmental threat that needs to be taken seriously and requires further research attention.

Report on the First Symposium on Invertebrate Neuroscience held on 13-17th August 2019 at the Balaton Limnological Institute, MTA Centre for Ecological Research, Tihany, Hungary

This meeting report provides an overview of the oral and poster presentations at the first international symposium for invertebrate neuroscience. The contents reflect the contributions of invertebrate neuroscience in addressing fundamental and fascinating challenges in understanding the neural substrates of animal behaviour.

The expression of opsins in the human skin and its implications for photobiomodulation: A Systematic Review

BACKGROUND

Skin is the organ most extensively exposed to light of a broad range of wavelengths. Several studies have reported that skin expresses photoreceptive molecules called opsins. However, the identity and functional role of opsins in the human skin remain elusive. We aim to summarize current scientific evidence on the types of opsins expressed in the skin and their biological functions.

METHODS

A primary literature search was conducted using PubMed to identify articles on dermal opsins found in nonhuman animals and humans.

RESULTS

Twenty-two articles, representing, however, a non-exhaustive selection of the scientific papers published in this specific field, met the inclusion criteria. In nonhuman animals, opsins and opsin-like structures have been detected in the skin of fruit fly, zebrafish, frog, octopus, sea urchin, hogfish, and mouse, and they mediate skin color change, light avoidance, shadow reflex, and circadian photoentrainment. In humans, opsins are present in various skin cell types, including keratinocytes, melanocytes, dermal fibroblasts, and hair follicle cells. They have been shown to mediate wound healing, melanogenesis, hair growth, and skin photoaging.

CONCLUSION

Dermal opsins have been identified across many nonhuman animals and humans. Current evidence suggests that opsins have biological significance beyond light reception. In nonhuman animals, opsins are involved in behaviors that are critical for survival. In humans, opsins are involved in various functions of the skin although the underlying molecular mechanisms remain unclear. Future investigation on elucidating the mechanism of dermal opsins will be crucial to expand the therapeutic benefits of photobiomodulation for various skin disorders.