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Pan YK. Structure and function of the larval teleost fish gill. J Comp Physiol B 2024:10.1007/s00360-024-01550-8. [PMID: 38584182 DOI: 10.1007/s00360-024-01550-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 02/05/2024] [Accepted: 03/25/2024] [Indexed: 04/09/2024]
Abstract
The fish gill is a multifunctional organ that is important in multiple physiological processes such as gas transfer, ionoregulation, and chemoreception. This characteristic organ of fishes has received much attention, yet an often-overlooked point is that larval fishes in most cases do not have a fully developed gill, and thus larval gills do not function identically as adult gills. In addition, large changes associated with gas exchange and ionoregulation happen in gills during the larval phase, leading to the oxygen and ionoregulatory hypotheses examining the environmental constraint that resulted in the evolution of gills. This review thus focuses exclusively on the larval fish gill of teleosts, summarizing the development of teleost larval fish gills and its function in gas transfer, ionoregulation, and chemoreception, and comparing and contrasting it to adult gills where applicable, while providing some insight into the oxygen vs ionoregulatory hypotheses debate.
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Affiliation(s)
- Yihang Kevin Pan
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
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Downie AT, Lefevre S, Illing B, Harris J, Jarrold MD, McCormick MI, Nilsson GE, Rummer JL. Rapid physiological and transcriptomic changes associated with oxygen delivery in larval anemonefish suggest a role in adaptation to life on hypoxic coral reefs. PLoS Biol 2023; 21:e3002102. [PMID: 37167194 PMCID: PMC10174562 DOI: 10.1371/journal.pbio.3002102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 03/31/2023] [Indexed: 05/13/2023] Open
Abstract
Connectivity of coral reef fish populations relies on successful dispersal of a pelagic larval phase. Pelagic larvae must exhibit high swimming abilities to overcome ocean and reef currents, but once settling onto the reef, larvae transition to endure habitats that become hypoxic at night. Therefore, coral reef fish larvae must rapidly and dramatically shift their physiology over a short period of time. Taking an integrative, physiological approach, using swimming respirometry, and examining hypoxia tolerance and transcriptomics, we show that larvae of cinnamon anemonefish (Amphiprion melanopus) rapidly transition between "physiological extremes" at the end of their larval phase. Daily measurements of swimming larval anemonefish over their entire early development show that they initially have very high mass-specific oxygen uptake rates. However, oxygen uptake rates decrease midway through the larval phase. This occurs in conjunction with a switch in haemoglobin gene expression and increased expression of myoglobin, cytoglobin, and neuroglobin, which may all contribute to the observed increase in hypoxia tolerance. Our findings indicate that critical ontogenetic changes in the gene expression of oxygen-binding proteins may underpin the physiological mechanisms needed for successful larval recruitment to reefs.
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Affiliation(s)
- Adam T Downie
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
- School of Biological Sciences, University of Queensland, St. Lucia, Australia
| | - Sjannie Lefevre
- Section for Physiology and Cell Biology, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Björn Illing
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
- Thünen Institute of Fisheries Ecology, Bremerhaven, Germany
| | - Jessica Harris
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
| | - Michael D Jarrold
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
- College of Science and Engineering, James Cook University, Townsville, Australia
| | - Mark I McCormick
- Coastal Marine Field Station, School of Science, University of Waikato, Tauranga, New Zealand
| | - Göran E Nilsson
- Section for Physiology and Cell Biology, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Jodie L Rummer
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Australia
- College of Science and Engineering, James Cook University, Townsville, Australia
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Tunnah L, Wilson JM, Wright PA. Retention of larval skin traits in adult amphibious killifishes: a cross-species investigation. J Comp Physiol B 2022; 192:473-488. [PMID: 35441298 DOI: 10.1007/s00360-022-01436-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 03/11/2022] [Accepted: 03/24/2022] [Indexed: 11/26/2022]
Abstract
The gills are the primary site of exchange in fishes. However, during early life-stages or in amphibious fishes, ionoregulation and gas-exchange may be primarily cutaneous. Given the similarities between larval and amphibious fishes, we hypothesized that cutaneous larval traits are continuously expressed in amphibious fishes across all life-stages to enable the skin to be a major site of exchange on land. Alternatively, we hypothesized that cutaneous larval traits disappear in juvenile stages and are re-expressed in amphibious species in later life-stages. We surveyed six species spanning a range of amphibiousness and characterized cutaneous ionocytes and neuroepithelial cells (NECs) as representative larval skin traits at up to five stages of development. We found that skin ionocyte density remained lower and constant in exclusively water-breathing, relative to amphibious species across development, whereas in amphibious species ionocyte density generally increased. Additionally, adults of the most amphibious species had the highest cutaneous ionocyte densities. Surprisingly, cutaneous NECs were only identified in the skin of one amphibious species (Kryptolebias marmoratus), suggesting that cutaneous NECs are not a ubiquitous larval or amphibious skin trait, at least among the species we studied. Our data broadly supports the continuous-expression hypothesis, as three of four amphibious experimental species expressed cutaneous ionocytes in all examined life-stages. Further, the increasing density of cutaneous ionocytes across development in amphibious species probably facilitates the prolonged occupation of terrestrial habitats.
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Affiliation(s)
- Louise Tunnah
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Jonathan M Wilson
- Department of Biology, Wilfrid Laurier University, Waterloo, ON, N2L 3C5, Canada
| | - Patricia A Wright
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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