DOI: 10.5061/dryad.tb2rbp03x
title: A key evolutionary step determining osmoregulatory ability for freshwater colonisation in early life stages of fish

description: Colonisation of freshwater habitats by marine animals is a remarkable
 evolutionary event that has enriched biodiversity in freshwater
 ecosystems. The acquisition of tolerance to hypotonic stress during early
 life stages is presumed to be essential for their successful freshwater
 colonisation, but very little empirical evidence has been obtained to
 support this idea. This study aimed to comprehend the evolutionary changes
 in osmoregulatory mechanisms that enhance larval freshwater tolerance in
 amphidromous fishes, which typically spend their larval period in marine
 (ancestral) habitats and the rest of their life history stages in
 freshwater (derived) habitats. We compared the life history patterns and
 changes in larval survivorship and gene expression depending on salinity
 among three congeneric marine-originated amphidromous goby species
 (Gymnogobius), which had been suggested to differ in their larval
 dependence on freshwater habitats. An otolith microchemical analysis and
 laboratory-rearing experiment confirmed the presence of freshwater
 residents only in G. urotaenia and higher larval survivorship of this
 species in the freshwater condition than in the obligate amphidromous G.
 petschiliensis and G. opperiens. Larval whole-body transcriptome analysis
 revealed that G. urotaenia from both amphidromous and freshwater-resident
 populations exhibited the greatest differences in expression levels of
 several osmoregulatory genes, including aqp3, which is critical for water
 discharge from their body during early fish development. The present
 results consistently support the importance of enhanced freshwater
 tolerance and osmoregulatory plasticity in larval fish to establish
 freshwater forms, and further identify key candidate genes for larval
 freshwater adaptation and colonisation in the goby group.
description: A) Person-Period data for survival analysis.xlsx<br>This
 dataset was used for a survival time analysis to evaluate larval tolerance
 to freshwater in the three <em>Gymnogobius</em> species, one
 of which has freshwater resident populations. In this analysis, to compare
 the survivorship between the freshwater and seawater groups, Cox
 proportional hazard models were established for each species using the
 coxph function in the survival R package version 3.2-13. In addition, to
 directly illustrate interspecific variations in the freshwater tolerance
 and test whether freshwater tolerant species also exhibit high survival in
 seawater (i.e. exhibit physiological plasticity), the survival in each
 salinity group was compared among the species by establishing the Cox
 proportional hazard models with the explanatory variable being
 species. B) Data for osmoregulatory gene expression
 analysis.xlsx<br>This dataset was used to compare the magnitude of
 expression changes of important osmoregulatory genes in larval fish
 between the <em>Gymnogobius</em> species with and without
 freshwater resident populations. The target genes for this analysis were
 selected by identifying differentially expressed genes (DEGs) between
 freshwater and seawater conditions, identifying osmoregulatory DEGs using
 the Gene Ontology (GO) term lists, and further extracting those which have
 been demonstrated to be responsible for osmoregulation in teleosts through
 an exhaustive review of published researches. The differences in the
 magnitude were tested by investigating the significance of the interaction
 effect between the salinity and presence of freshwater forms in the
 species in LMMs using the lmer function.
description: This README file was generated on 2023-10-24 by Yumeki Oto. GENERAL
 INFORMATION 1. Title of Dataset: A key evolutionary step determining
 osmoregulatory ability for freshwater colonisation in early life stages of
 fish 2. Author Information A. Principal Investigator Contact Information
 Name: Yumeki Oto Institution: National Fisheries University Address:
 Shimonoseki City, Yamaguchi Prefecture, Japan Email:
 angler\_yumeki@yahoo.co.jp <br> B. Associate or Co-investigator
 Contact Information Name: Katsutoshi Watanabe Institution: Kyoto
 University Address: Kyoto City, Kyoto Prefecture, Japan Email:
 watanak@terra.zool.kyoto-u.ac.jp 3. Date of data collection (single date,
 range, approximate date): 2018-2021 4. Geographic location of data
 collection: Hokkaido, Niigata, Tokyo, Fukui, Shiga, Mie, and Kyoto
 Prefectures, Japan 5. Information about funding sources that supported the
 collection of the data: Japan Society for the Promotion of Science, Award:
 17H03720 Japan Society for the Promotion of Science, Award: 18J21793
 SHARING/ACCESS INFORMATION 1. Licenses/restrictions placed on the data:
 CC0 1.0 Universal (CC0 1.0) Public Domain 2. Links to publications that
 cite or use the data: Oto, Y., Kuroki, M., Iida, M., Ito, R., Nomura, S.,
 & Watanabe, K. (in press). A key evolutionary step determining
 osmoregulatory ability for freshwater colonisation in early life stage of
 fish. Journal of Experimental Biology. 3. Links to other publicly
 accessible locations of the data: None 4. Links/relationships to ancillary
 data sets: None 5. Was data derived from another source? No A. If yes,
 list source(s): NA 6. Recommended citation for this dataset: Oto, Y.,
 Kuroki, M., Iida, M., Ito, R., Nomura, S., & Watanabe, K. (2023).
 Data from: A key evolutionary step determining osmoregulatory ability for
 freshwater colonisation in early life stages of fish. Dryad Digital
 Repository. https://doi.org/10.5061/dryad.tb2rbp03x DATA & FILE
 OVERVIEW 1. File List: A) Person-Period data for survival analysis.xlsx B)
 Data for osmoregulatory gene expression analysis.xlsx 2. Relationship
 between files, if important: None 3. Additional related data collected
 that was not included in the current data package: None 4. Are there
 multiple versions of the dataset? No A. If yes, name of file(s) that was
 updated: NA i. Why was the file updated? NA ii. When was the file updated?
 NA
 #########################################################################
 DATA-SPECIFIC INFORMATION FOR: Person-Period data for survival
 analysis.xlsx 1. Number of variables: 5 2. Number of cases/rows: There are
 three sheets for each fish species, each with a different number of
 columns as follows; 　　　G. petschiliensis: 1796 　　　G. opperiens: 1982 　　　G.
 urotaenia: 3705 3. Variable List: * Larval ID: The same ID means the same
 individual. * Day: Number of days after hatching (i.e. day-old). *
 Salinity: Rearing salinity condition of larval fish: freshwater (FW) or
 seawater (SW) treatment. * Event: Whether or not larval mortality occurred
 on each observation date. The numbers '0' and '1'
 indicate 'dead' and 'alive', respectively. * Clutch:
 ID of the egg clutch (parent) from which the newly hatched larvae were
 derived. 4. Missing data codes: None 5. Specialized formats or other
 abbreviations used: None
 #########################################################################
 DATA-SPECIFIC INFORMATION FOR: Data for osmoregulatory gene expression
 analysis.xlsx 1. Number of variables: 5 2. Number of cases/rows: 31 3.
 Variable List: * PFF: Presence of freshwater forms in each species. The
 numbers '0' and '1' indicate 'absence' and
 'presence' of freshwater forms, respectively. * Salinity:
 Rearing salinity condition of larval fish: freshwater (0) or seawater (1)
 treatment. * Population: Population from which the newly hatched larvae
 were derived. * Parent: ID of the parent (egg clutch) from which the newly
 hatched larvae were derived. * aqp3, slc13, slc22a16, sgk1, slc12a, cldne:
 Expression level of each osmoregulatory gene. 4. Missing data codes: None
 5. Specialized formats or other abbreviations used: None