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Leonard EM, Porteus CS, Brink D, Milsom WK. Fish gill chemosensing: knowledge gaps and inconsistencies. J Comp Physiol B 2024:10.1007/s00360-024-01553-5. [PMID: 38758303 DOI: 10.1007/s00360-024-01553-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 04/04/2024] [Indexed: 05/18/2024]
Abstract
In this review, we explore the inconsistencies in the data and gaps in our knowledge that exist in what is currently known regarding gill chemosensors which drive the cardiorespiratory reflexes in fish. Although putative serotonergic neuroepithelial cells (NEC) dominate the literature, it is clear that other neurotransmitters are involved (adrenaline, noradrenaline, acetylcholine, purines, and dopamine). And although we assume that these agents act on neurons synapsing with the NECs or in the afferent or efferent limbs of the paths between chemosensors and central integration sites, this process remains elusive and may explain current discrepancies or species differences in the literature. To date it has been impossible to link the distribution of NECs to species sensitivity to different stimuli or fish lifestyles and while the gills have been shown to be the primary sensing site for respiratory gases, the location (gills, oro-branchial cavity or elsewhere) and orientation (external/water or internal/blood sensing) of the NECs are highly variable between species of water and air breathing fish. Much of what has been described so far comes from studies of hypoxic responses in fish, however, changes in CO2, ammonia and lactate have all been shown to elicit cardio-respiratory responses and all have been suggested to arise from stimulation of gill NECs. Our view of the role of NECs is broadening as we begin to understand the polymodal nature of these cells. We begin by presenting the fundamental picture of gill chemosensing that has developed, followed by some key unanswered questions about gill chemosensing in general.
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Affiliation(s)
- Erin M Leonard
- Department of Biology, Wilfrid Laurier University, Waterloo, ON, Canada
| | - Cosima S Porteus
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada.
| | - Deidre Brink
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
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Wang W, Huang J, Hu Y, Feng J, Gao D, Fang W, Xu M, Ma C, Fu Z, Chen Q, Liang X, Lu J. Seascapes Shaped the Local Adaptation and Population Structure of South China Coast Yellowfin Seabream (Acanthopagrus latus). MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2024; 26:60-73. [PMID: 38147145 DOI: 10.1007/s10126-023-10277-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 12/14/2023] [Indexed: 12/27/2023]
Abstract
Understanding the genetic composition and regional adaptation of marine species under environmental heterogeneity and fishing pressure is crucial for responsible management. In order to understand the genetic diversity and adaptability of yellowfin seabream (Acanthopagrus latus) along southern China coast, this study was conducted a seascape genome analysis on yellowfin seabream from the ecologically diverse coast, spanning over 1600 km. A total of 92 yellowfin seabream individuals from 15 sites were performed whole-genome resequencing, and 4,383,564 high-quality single nucleotide polymorphisms (SNPs) were called. By conducting a genotype-environment association analysis, 29,951 adaptive and 4,328,299 neutral SNPs were identified. The yellowfin seabream exhibited two distinct population structures, despite high gene flow between sites. The seascape genome analysis revealed that genetic structure was influenced by a variety of factors including salinity gradients, habitat distance, and ocean currents. The frequency of allelic variation at the candidate loci changed with the salinity gradient. Annotation of these loci revealed that most of the genes are associated with osmoregulation, such as kcnab2a, kcnk5a, and slc47a1. These genes are significantly enriched in pathways associated with ion transport including G protein-coupled receptor activity, transmembrane signaling receptor activity, and transporter activity. Overall, our findings provide insights into how seascape heterogeneity affects adaptive evolution, while providing important information for regional management in yellowfin seabream populations.
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Affiliation(s)
- Wenhao Wang
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Junrou Huang
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Yan Hu
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Jianxiang Feng
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | - Dong Gao
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Wenyu Fang
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Meng Xu
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Chunlei Ma
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Zhenqiang Fu
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Qinglong Chen
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Xuanguang Liang
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China
| | - Jianguo Lu
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China.
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China.
- Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering, Guangzhou, Guangdong, China.
- Pearl River Estuary Marine Ecosystem Research Station, Ministry of Education, Zhuhai, China.
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Pan YK, Perry SF. The control of breathing in fishes - historical perspectives and the path ahead. J Exp Biol 2023; 226:307288. [PMID: 37097020 DOI: 10.1242/jeb.245529] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2023]
Abstract
The study of breathing in fishes has featured prominently in Journal of Experimental Biology (JEB), particularly during the latter half of the past century. Indeed, many of the seminal discoveries in this important sub-field of comparative respiratory physiology were reported first in JEB. The period spanning 1960-1990 (the 'golden age of comparative respiratory physiology') witnessed intense innovation in the development of methods to study the control of breathing. Many of the guiding principles of piscine ventilatory control originated during this period, including our understanding of the dominance of O2 as the driver of ventilation in fish. However, a critical issue - the identity of the peripheral O2 chemoreceptors - remained unanswered until methods for cell isolation, culture and patch-clamp recording established that gill neuroepithelial cells (NECs) respond to hypoxia in vitro. Yet, the role of the NECs and other putative peripheral or central chemoreceptors in the control of ventilation in vivo remains poorly understood. Further progress will be driven by the implementation of genetic tools, most of which can be used in zebrafish (Danio rerio). These tools include CRISPR/Cas9 for selective gene knockout, and Tol2 systems for transgenesis, the latter of which enables optogenetic stimulation of cellular pathways, cellular ablation and in vivo cell-specific biosensing. Using these methods, the next period of discovery will see the identification of the peripheral sensory pathways that initiate ventilatory responses, and will elucidate the nature of their integration within the central nervous system and their link to the efferent motor neurons that control breathing.
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Affiliation(s)
- Yihang Kevin Pan
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5
| | - Steve F Perry
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5
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Perry SF, Pan YK, Gilmour KM. Insights into the control and consequences of breathing adjustments in fishes-from larvae to adults. Front Physiol 2023; 14:1065573. [PMID: 36793421 PMCID: PMC9923008 DOI: 10.3389/fphys.2023.1065573] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Accepted: 01/11/2023] [Indexed: 01/31/2023] Open
Abstract
Adjustments of ventilation in fishes to regulate the volume of water flowing over the gills are critically important responses to match branchial gas transfer with metabolic needs and to defend homeostasis during environmental fluctuations in O2 and/or CO2 levels. In this focused review, we discuss the control and consequences of ventilatory adjustments in fish, briefly summarizing ventilatory responses to hypoxia and hypercapnia before describing the current state of knowledge of the chemoreceptor cells and molecular mechanisms involved in sensing O2 and CO2. We emphasize, where possible, insights gained from studies on early developmental stages. In particular, zebrafish (Danio rerio) larvae have emerged as an important model for investigating the molecular mechanisms of O2 and CO2 chemosensing as well as the central integration of chemosensory information. Their value stems, in part, from their amenability to genetic manipulation, which enables the creation of loss-of-function mutants, optogenetic manipulation, and the production of transgenic fish with specific genes linked to fluorescent reporters or biosensors.
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Hughes MC, Perry SF. Does blood flow limit acute hypoxia performance in larval zebrafish (Danio rerio)? J Comp Physiol B 2021; 191:469-478. [PMID: 33580284 DOI: 10.1007/s00360-020-01331-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 10/22/2020] [Accepted: 11/18/2020] [Indexed: 01/21/2023]
Abstract
Oxygen uptake (ṀO2) in larval zebrafish prior to maturation of the gill relies on cutaneous O2 transfer. Under normoxic conditions, rates of cutaneous O2 transfer are unaffected by haemoglobin availability but are diminished in fish lacking a functional circulatory system, suggesting that internal convection is critically involved in setting the resting ṀO2 in zebrafish larvae, even when relying on cutaneous O2 transfer. The reliance of ṀO2 on blood circulation led to the first objective of the current study, to determine whether loss of internal convection would reduce acute hypoxia performance (as determined by measuring critical PO2; Pcrit) in larval zebrafish under conditions of moderate hypoxia (PO2 = 55 mmHg) at 28.5 and 34 °C. Internal convection was eliminated by preventing development of blood vessels using morpholino knockdown of vascular endothelial growth factor (VEGF); these fish are termed VEGF morphants. Breathing frequency (fV) and heart rate (fH) also were measured (at 28.5 °C) to determine whether any detriment in performance might be linked to cardiorespiratory dysfunction. Although ṀO2 was reduced in the VEGF morphants, there was no significant effect on Pcrit at 28.5 °C. Raising temperature to 34 °C resulted in the VEGF morphants exhibiting a higher Pcrit than the shams, suggesting an impairment of hypoxia tolerance in the morphants at the higher temperature. The usual robust increase in fV during hypoxia was absent or attenuated in VEGF morphants at 4 and 5 days post fertilization (dpf), respectively. Resting fH was reduced in the VEGF morphants and unlike the sham fish, the morphants did not exhibit hypoxic tachycardia at 4 or 5 dpf. The number of cutaneous neuroepithelial cells (presumptive O2 chemoreceptors) was significantly higher in the VEGF morphants and thus the cardiorespiratory impairment in the morphants during hypoxia was unlikely related to inadequate peripheral O2 sensing.
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Affiliation(s)
- M C Hughes
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, K1N6N5, Canada
| | - S F Perry
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, K1N6N5, Canada.
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