Biology subjects

Morino, Y.

Publications and source records attributed to Morino, Y..

3 recordsLinked to original sources

bioRxiv2024

Early development of the mineralized external skeleton of the polyplacophoran mollusk, with insight into the evolutionary history of shell plates and spicules.

Recent molecular phylogenetic studies have raised two questions about the evolutionary history of the calcified exoskeleton of mollusks. The first question concerns the homology of the two types of skeleton; whether spicules and shell plates share an evolutionary origin. The second question is the homology of the shell plates between chitons and other mollusks, including gastropods and bivalves. To gain insight into these questions, we examined the early development of shell plates and spicules in chitons. We identified several developmental genes that are involved in both shell plates and spicules, suggesting that spicules and shell plates share a common evolutionary origin. We also found that subpopulations of the dorsal shell field (the ridge and the plate field) have specific gene expression profiles. The differential gene expression of the ridge and plate field is not identical to the profiles of the zones of the gastropod shell field. This observation may suggest an independent evolutionary origin of the shell plates in chitons and gastropods.

evolutionary biology↗

bioRxiv2024

Development of shell field populations in gastropods

The embryonic shell field of mollusks first appears during gastrulation of the dorsal ectoderm and subsequently develops into the shell-secreting mantle in adult animals. Although several lines of evidence have revealed that this shell field lineage is exclusively derived from the second quartet (2q) of the 16-cell embryos, it is generally believed that the establishment of the shell field fate would be accomplished only after receiving inductive signals from the invaginated endoderm. Despite being accepted as a comprehensive model for molluskan shell field specification, the validity of this induction hypothesis remains questionable owing to the lack of clear experimental evidence and contradictory results. Here, we attempted to re-investigate the inductive role of the endoderm in shell field fate establishment in the limpet Nipponacmea fuscoviridis by experimentally disrupting cell-cell contacts between cell lineages after the 16-cell stage. First, we characterized the shell field cell population by performing two-color in situ hybridization. We characterized at least three cell populations in the developing shell field. Using single-cell transcriptome analysis, we identified several specific effector genes for each population, as well as transcription factor genes. Differentiation of each shell field population was inspected in 2q blastomeres isolated from other cells of the 16-cell embryos. Despite the absence of any interlineage interactions (including ectoderm-endoderm contacts), the expression of marker genes for each shell field population was observed in the isolated 2q fragments. In addition, the expression of several shell field genes was detected in embryos in which cytokinesis was blocked at the 16-cell stage. We concluded that the early process of shell field differentiation in the 2q lineage occurs mostly independently of the interactions with other lineages.

developmental biology↗

bioRxiv2023

Millisecond-scale behaviours of plankton quantified in situ and in vitro using the Event-based Vision Sensor (EVS)

The Event-based Vision Sensor (EVS) is a bio-inspired sensor that captures detailed motions of objects, developed with the applicability to become the eyes of machines and especially self-driving cars. Compared to conventional frame-based image sensors as employed in video cameras, EVS has an extremely fast motion capture equivalent to 10,000-fps even with standard optical settings and additionally has high dynamic ranges for brightness and also lower consumption of memory and energy. These features make the EVS an ideal method to tackle questions in biology, such as the fine-scale behavioural ecology. Here, we developed 22 characteristic features for analysing the motions of aquatic particles from the raw data of the EVS, and deployed the EVS system in both natural environments and laboratory aquariums to test its applicability to filming and analysing plankton behaviour. Our EVS monitoring in turbid water at the bottom of Lake Biwa, Japan identified several particles exhibiting distinct cumulative trajectory with periodicities in their motion (up to 16 Hz), suggesting that they were living organisms with rhythmic behaviour. We also carried out EVS monitoring in the deep sea aided by infrared lighting to minimise influence on behaviour, and observed particles with active motion and periodicities over 40 Hz. Furthermore, we used the EVS to observe laboratory cultures of six species of zooplankton and phytoplankton, confirming that they have species-specific motion periodicities of up to 41 Hz. We applied machine learning to automatically classify particles into five categories (four categories of zooplankton plus passive particles), which achieved an accuracy up to 86%. Our attempts to use the EVS for biological observations, especially focusing on its millisecond-scale temporal resolution and wide dynamic range provide a new avenue to investigate rapid and periodical motion and behaviour in small organisms. Given its compact size with low consumption of battery and memory, the EVS will likely be applicable in the near future for the automated monitoring of the behaviour of plankton by edge computing on autonomous floats, as well as quantifying rapid cellular-level activities under microscopy.

animal behavior and cognition↗