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Wlodkowic D, Bownik A, Leitner C, Stengel D, Braunbeck T. Beyond the behavioural phenotype: Uncovering mechanistic foundations in aquatic eco-neurotoxicology. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 829:154584. [PMID: 35306067 DOI: 10.1016/j.scitotenv.2022.154584] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Revised: 03/09/2022] [Accepted: 03/11/2022] [Indexed: 06/14/2023]
Abstract
During the last decade, there has been an increase in awareness of how anthropogenic pollution can alter behavioural traits of diverse aquatic organisms. Apart from understanding profound ecological implications, alterations in neuro-behavioural indices have emerged as sensitive and physiologically integrative endpoints in chemical risk assessment. Accordingly, behavioural ecotoxicology and broader eco-neurotoxicology are becoming increasingly popular fields of research that span a plethora of fundamental laboratory experimentations as well as applied field-based studies. Despite mounting interest in aquatic behavioural ecotoxicology studies, there is, however, a considerable paucity in deciphering the mechanistic foundations underlying behavioural alterations upon exposure to pollutants. The behavioural phenotype is indeed the highest-level integrative neurobiological phenomenon, but at its core lie myriads of intertwined biochemical, cellular, and physiological processes. Therefore, the mechanisms that underlie changes in behavioural phenotypes can stem among others from dysregulation of neurotransmitter pathways, electrical signalling, and cell death of discrete cell populations in the central and peripheral nervous systems. They can, however, also be a result of toxicity to sensory organs and even metabolic dysfunctions. In this critical review, we outline why behavioural phenotyping should be the starting point that leads to actual discovery of fundamental mechanisms underlying actions of neurotoxic and neuromodulating contaminants. We highlight potential applications of the currently existing and emerging neurobiology and neurophysiology analytical strategies that should be embraced and more broadly adopted in behavioural ecotoxicology. Such strategies can provide new mechanistic discoveries instead of only observing the end sum phenotypic effects.
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Affiliation(s)
- Donald Wlodkowic
- The Neurotox Laboratory, School of Science, RMIT University, Melbourne, Australia.
| | - Adam Bownik
- Department of Hydrobiology and Protection of Ecosystems, Faculty of Environmental Biology, University of Life Sciences, Lublin, Poland
| | - Carola Leitner
- Aquatic Ecology and Toxicology, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, D-69120 Heidelberg, Germany
| | - Daniel Stengel
- Aquatic Ecology and Toxicology, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, D-69120 Heidelberg, Germany
| | - Thomas Braunbeck
- Aquatic Ecology and Toxicology, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, D-69120 Heidelberg, Germany
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Stark G. Large and expensive brain comes with a short lifespan: The relationship between brain size and longevity among fish taxa. JOURNAL OF FISH BIOLOGY 2022; 101:92-99. [PMID: 35482011 PMCID: PMC9544989 DOI: 10.1111/jfb.15074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 04/22/2022] [Indexed: 06/14/2023]
Abstract
Vertebrates show substantial interspecific variation in brain size in relation to body mass. It has long been recognized that the evolution of large brains is associated with both costs and benefits, and it is their net benefit which should be favoured by natural selection. On one hand, the substantial energetic cost imposed by the maintenance of neural tissue is expected to compromise the energetic budget of organisms with large brains and their investment in other critical organs (expensive brain framework, EBF) or important physiological process, such as somatic maintenance and repair, thus accelerating ageing that shortens lifespan, as predicted by the disposable soma theory (DST). However, selection towards larger brain size can provide cognitive benefits (e.g., high behavioural flexibility) that may mitigate extrinsic mortality pressures, and thus may indirectly select for slower ageing that prolongs lifespan, as predicted by the cognitive buffer hypothesis (CBH). The relationship between longevity and brain size has been investigated to date only among terrestrial vertebrates, although the same selective forces acting on those species may also affect vertebrates living in aquatic habitats, such as fish. Thus, whether this evolutionary trade-off for brain size and longevity exists on a large scale among fish clades remains to be addressed. In this study, using a global dataset of 407 fish species, I undertook the first phylogenetic test of the brain size/longevity relationship in aquatic vertebrate species. The study revealed a negative relationship between brain size and longevity among cartilaginous fish confirming EBF and DST. However, no pattern emerged among bony fish species. Among sharks and rays, the high metabolic cost of producing neural tissue transcends the cognitive benefits of evolving a larger brain. Consequently, my findings suggest that the cost of maintaining brain tissue is relatively higher in ectothermic species than in endothermic ones.
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Affiliation(s)
- Gavin Stark
- School of Zoology, Faculty of Life SciencesTel Aviv UniversityTel AvivIsrael
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Tsuboi M. Exceptionally Steep Brain-Body Evolutionary Allometry Underlies the Unique Encephalization of Osteoglossiformes. BRAIN, BEHAVIOR AND EVOLUTION 2021; 96:49-63. [PMID: 34634787 DOI: 10.1159/000519067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 07/28/2021] [Indexed: 01/06/2023]
Abstract
Brain-body static allometry, which is the relationship between brain size and body size within species, is thought to reflect developmental and genetic constraints. Existing evidence suggests that the evolution of large brain size without accompanying changes in body size (that is, encephalization) may occur when this constraint is relaxed. Teleost fish species are generally characterized by having close-fitting brain-body static allometries, leading to strong allometric constraints and small relative brain sizes. However, one order of teleost, Osteoglossiformes, underwent extreme encephalization, and its mechanistic bases are unknown. Here, I used a dataset and phylogeny encompassing 859 teleost species to demonstrate that the encephalization of Osteoglossiformes occurred through an increase in the slope of evolutionary (among-species) brain-body allometry. The slope is virtually isometric (1.03 ± 0.09 SE), making it one of the steepest evolutionary brain-body allometric slopes reported to date, and it deviates significantly from the evolutionary brain-body allometric slopes of other clades of teleost. Examination of the relationship between static allometric parameters (intercepts and slopes) and evolutionary allometry revealed that the dramatic steepening of the evolutionary allometric slope in Osteoglossiformes was a combined result of evolution in the slopes and intercepts of static allometry. These results suggest that the evolution of static allometry, which likely has been driven by evolutionary changes in the rate and timing of brain development, has facilitated the unique encephalization of Osteoglossiformes.
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Affiliation(s)
- Masahito Tsuboi
- Department of Biology, Lund University, Lund, Sweden.,Department of Biosciences, University of Oslo, Oslo, Norway
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Senarat S, Kettratad J, Kaneko G, Kamnurdnin T, Sudtongkong C. The microanatomy of the central nervous system and brain of the Indo-Pacific seahorse, Hippocampus barbouri, during development. ZOOLOGIA 2020. [DOI: 10.3897/zoologia.37.e53734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The central nervous system (CNS) of Teleostei is a complex system of self-governance and its morphology is reflected in the physiological and reproductive behaviors. The Indo-Pacific seahorse, Hippocampus barbouri Jordan & Richardson, 1908, is a new candidate species for aquaculture in Thailand. In this study, we investigated the brain morphology of H. barbouri across various developmental windows. Light microscopic observations of adult brains revealed a large optic tectum in the mesencephalon, whereas the cerebral hemispheres and the cerebellum are of medium size. The detailed brain structures were generally similar to those of other teleosts; however, only five distinct layers were present in the optic tectum, including the stratum marginale, stratum opticum, stratum album central, stratum griseum central, and stratum periventriculae, versus six layers observed in other fish. One day after birth (1 DAB) the brain was a packed structure without any clear sub-structures. The number of capillaries in the optic tectum began to increase at 6 DAB, and at 14 DAB several features, including small blood vessels in the optic tectum and Purkinje cells, became noticeable. By 35 DAB, the optic tectum became highly vascularized and included five layers. Additionally, large Purkinje cells were developed in the cerebellum. Based on the brain development pattern, we speculate that the predatory ability of this fish starts to develop from 6 to 14 days after birth.
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Rouse J, McDowall L, Mitchell Z, Duncan EJ, Bretman A. Social competition stimulates cognitive performance in a sex-specific manner. Proc Biol Sci 2020; 287:20201424. [PMID: 32933446 DOI: 10.1098/rspb.2020.1424] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Social interactions are thought to be a critical driver in the evolution of cognitive ability. Cooperative interactions, such as pair bonding, rather than competitive interactions have been largely implicated in the evolution of increased cognition. This is despite competition traditionally being a very strong driver of trait evolution. Males of many species track changes in their social environment and alter their reproductive strategies in response to anticipated levels of competition. We predict this to be cognitively challenging. Using a Drosophila melanogaster model, we are able to distinguish between the effects of a competitive environment versus generic social contact by exposing flies to same-sex same-species competition versus different species partners, shown to present non-competitive contacts. Males increase olfactory learning/memory and visual memory after exposure to conspecific males only, a pattern echoed by increased expression of synaptic genes and an increased need for sleep. For females, largely not affected by mating competition, the opposite pattern was seen. The results indicate that specific social contacts dependent on sex, not simply generic social stimulation, may be an important evolutionary driver for cognitive ability in fruit flies.
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Affiliation(s)
- James Rouse
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Laurin McDowall
- Centre for Gene Regulation and Expression School of Life Sciences, Dow Street, Dundee DD1 5EH, UK
| | - Zak Mitchell
- Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK
| | - Elizabeth J Duncan
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Amanda Bretman
- School of Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
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Wilson AB, Wegmann A, Ahnesjö I, Gonçalves JMS. The evolution of ecological specialization across the range of a broadly distributed marine species. Evolution 2020; 74:629-643. [PMID: 31976557 DOI: 10.1111/evo.13930] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 01/16/2020] [Accepted: 01/19/2020] [Indexed: 01/01/2023]
Abstract
Ecological specialization is an important engine of evolutionary change and adaptive radiation, but empirical evidence of local adaptation in marine environments is rare, a pattern that has been attributed to the high dispersal ability of marine taxa and limited geographic barriers to gene flow. The broad-nosed pipefish, Syngnathus typhle, is one of the most broadly distributed syngnathid species and shows pronounced variation in cranial morphology across its range, a factor that may contribute to its success in colonizing new environments. We quantified variation in cranial morphology across the species range using geometric morphometrics, and tested for evidence of trophic specialization by comparing individual-level dietary composition with the community of prey available at each site. Although the diets of juvenile pipefish from each site were qualitatively similar, ontogenetic shifts in dietary composition resulted in adult populations with distinctive diets consistent with their divergent cranial morphology. Morphological differences found in nature are maintained under common garden conditions, indicating that trophic specialization in S. typhle is a heritable trait subject to selection. Our data highlight the potential for ecological specialization in response to spatially variable selection pressures in broadly distributed marine species.
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Affiliation(s)
- Anthony B Wilson
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, 8057, Zurich, Switzerland.,Department of Biology, Brooklyn College, City University of New York, Brooklyn, New York, 11210.,The Graduate Center, City University of New York, New York, New York, 10016
| | - Alexandra Wegmann
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, 8057, Zurich, Switzerland
| | - Ingrid Ahnesjö
- Department of Ecology and Genetics/Animal Ecology, Uppsala University, SE-75236, Uppsala, Sweden
| | - Jorge M S Gonçalves
- Centro de Ciencias do Mar (CCMAR), Coastal Fisheries Research Group, Universidade do Algarve, 8005-139, Faro, Portugal
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Tsuboi M. Biological interpretations of the biphasic model of ontogenetic brain–body allometry: a reply to Packard. Biol J Linn Soc Lond 2019. [DOI: 10.1093/biolinnean/blz149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Allometry is a description of organismal growth. Historically, a simple power law has been used most widely to describe the rate of growth in phenotypic traits relative to the rate of growth in overall size. However, the validity of this standard practice has repeatedly been criticized. In an accompanying opinion piece, Packard reanalysed data from a recent study on brain–body ontogenetic allometry and claimed that the biphasic growth model suggested in that study was an artefact of logarithmic transformation. Based on the model selection, Packard proposed alternative hypotheses for brain–body ontogenetic allometry. Here, I examine the validity of these models by comparing empirical data on body sizes at two critical neurodevelopmental events in mammals, i.e. at birth and at the time of the peak rate of brain growth, with statistically inferred body sizes that are supposed to characterize neurodevelopmental processes. These analyses support the existence of two distinct phases of brain growth and provide weak support for Packard's uniphasic model of brain growth. This study demonstrates the importance of considering alternative models in studies of allometry, but also highlights that such models need to respect the biological theoretical context of allometry.
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Affiliation(s)
- Masahito Tsuboi
- Department of Biology, Lund University, Lund, Sweden
- Department of Biology, University of Oslo, Oslo, Norway
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Ofelio C, Díaz AO, Radaelli G, Planas M. Histological development of the long-snouted seahorse Hippocampus guttulatus during ontogeny. JOURNAL OF FISH BIOLOGY 2018; 93:72-87. [PMID: 29882347 DOI: 10.1111/jfb.13668] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 04/22/2018] [Indexed: 06/08/2023]
Abstract
The objective of the present study was to describe histological development of the European long-snouted seahorse Hippocampus guttulatus, to increase understanding of the biology and physiology of the species. Most vital organs were present in juveniles by the time of their release from the male's pouch. Digestive tract specialization occurred at 89 effective day-degrees (D°eff ), corresponding to 15 days post partum (dpp), with development of the first intestinal loop and mucosal folding. At 118 D°eff (20 dpp), lipids were being mobilized from the liver and oocytes attained the perinuclear stage. The fovea emerged at 177 D°eff (30 dpp), contemporaneous with the shift from pelagic to benthic behaviour in juveniles. At this stage, the most interesting feature was the formation of the second intestinal loop. Male gonads were never observed during the study (from 0 to 354 D°eff ; 0-60 dpp), but the first oogonia were present at 30 D°eff (5 dpp). In 354 D°eff (60 dpp) juveniles, oocytes were observed in a cortical alveoli stage, indicating maturity. Low digestive efficiency was observed at early stages, which was due to a poorly developed gastrointestinal tract and an immature digestive tract prior to 89 D°eff . The present study demonstrates that approximately 89 and 177 D°eff represent two important transitional stages in the early development of H. guttulatus. At a temperature of approximately 19 ± 1°C and an age of 1 month (177 D°eff ), main organs were fully functional, suggesting that the adult phenotype was largely established by that age, with females becoming mature at the age of 2 months (354 D°eff ).
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Affiliation(s)
- Claudia Ofelio
- Departamento de Ecología y Recursos Marinos, Instituto de Investigaciones Marinas, Consejo Superior de Investigaciones Científicas (IIM-CSIC), Vigo, Spain
| | - Alcira Ofelia Díaz
- Departamento de Biología, Instituto de Investigaciones Marinas y Costeras (IIMyC), FCEyN, CONICET- Universidad Nacional de Mar del Plata, Buenos Aires, Argentina
| | - Giuseppe Radaelli
- Dipartimento di Biomedicina Comparata e Alimentazione, Universitá di Padova, Legnaro, Italy
| | - Miquel Planas
- Departamento de Ecología y Recursos Marinos, Instituto de Investigaciones Marinas, Consejo Superior de Investigaciones Científicas (IIM-CSIC), Vigo, Spain
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