PeerJ Preprints: Aquaculture, Fisheries and Fish Sciencehttps://peerj.com/preprints/index.atom?journal=peerj&subject=200Aquaculture, Fisheries and Fish Science articles published in PeerJ PreprintsFirst confirmation of the shell-boring oyster parasite Polydora websteri (Polychaeta: Spionidae) in Washington State, USAhttps://peerj.com/preprints/276212019-11-212019-11-21Julieta MartinelliHeather LopesLorenz HauserIsadora Jimenez-HidalgoTeri L KingJacqueline Padilla-GaminoPaul RawsonLaura SpencerJason WilliamsChelsea Wood
Invasions by the spionid polychaete Polydora websteri have resulted in the collapse of oyster aquaculture industries in Australia, New Zealand, and Hawaii. These worms burrow into the shells of bivalves, creating unsightly mud blisters that are unappealing to consumers and, when nicked during shucking, release mud and detritus that can foul oyster meats. Recent sightings of mud blisters on the shells of Pacific oysters (Crassostrea gigas) in Puget Sound, Washington, suggest a new spionid polychaete invasion. To determine the identity of the polychaete causing these mud blisters, we obtained Pacific oysters from two locations in Puget Sound and examined them for blisters and burrows associated with spionid infection. We then extracted polychaetes and sequenced mitochondrial (cytochrome c oxidase I [COI]) and nuclear (18S rRNA) genes to obtain species-level identifications for a subset of these worms. Our data confirm that P. websteri is present in mud blisters of Puget Sound oysters, constituting the first confirmed record of this species in Washington State. The presence of non-native P. websteri could threaten the sustainability of oyster aquaculture in Washington, which currently produces more shellfish than any other US state.
Invasions by the spionid polychaete Polydora websteri have resulted in the collapse of oyster aquaculture industries in Australia, New Zealand, and Hawaii. These worms burrow into the shells of bivalves, creating unsightly mud blisters that are unappealing to consumers and, when nicked during shucking, release mud and detritus that can foul oyster meats. Recent sightings of mud blisters on the shells of Pacific oysters (Crassostrea gigas) in Puget Sound, Washington, suggest a new spionid polychaete invasion. To determine the identity of the polychaete causing these mud blisters, we obtained Pacific oysters from two locations in Puget Sound and examined them for blisters and burrows associated with spionid infection. We then extracted polychaetes and sequenced mitochondrial (cytochrome c oxidase I [COI]) and nuclear (18S rRNA) genes to obtain species-level identifications for a subset of these worms. Our data confirm that P. websteri is present in mud blisters of Puget Sound oysters, constituting the first confirmed record of this species in Washington State. The presence of non-native P. websteri could threaten the sustainability of oyster aquaculture in Washington, which currently produces more shellfish than any other US state.Development and characterization of novel cross-species tetranucleotide microsatellite markers for sterlet (Acipenser ruthenus) from Chinese sturgeon (Acipenser sinensis)https://peerj.com/preprints/279642019-09-172019-09-17Yacheng HuJing YangXueqing LiuKan XiaoBinzhong WangHejun Du
Sterlet (Acipenser ruthenus) is an important economic fish because of its nourishing caviar, isinglass and flesh. In order to facilitate the recovery of this species, the full understanding of its population genetic structure is necessary for taking appropriate management actions. However, genetic data on the use of nuclear loci in sterlet is still quite poor because microsatellite markers in sterlet that had been developed appeared to be polyploidy which add difficulties in studying the genetic of the sterlet. In this study, 24 tetranucleotide microsatellite markers were developed in sterlet from 160 microsatellite markers of the endangered Chinese sturgeon (Acipenser sinensis). Ten (ZHX76, ZHX64, Z194, Z217, Z184, Z242, Z250, Z258, Z268 and Z269) of the 24 loci showed disomic patterns while the rest loci showed tetrasomic patterns. In this paper, 24 microsatellite markers were characterized in 16 sterlet individuals and all of them were polymorphic with 2 to 7 alleles per locus. The Hardy-Weinberg departure value (d), polymorphic information content (PIC), the observed heterozygosity (HO), the Shannon-Wiener Diversity Indices (H') and the mean expected heterozygosity (HE) of all 24 polymorphic loci ranged from -0.334 to 0.484, 0.367 to 0.725, 0.438 to 1, 0.659 to 1.695, from 0.466 to 0.777, respectively. The markers described here will help in addressing practical problems such as the study of population genetics, conservation genetics and evolution in the polyploidy derivative nature of sterlet.
Sterlet (Acipenser ruthenus) is an important economic fish because of its nourishing caviar, isinglass and flesh. In order to facilitate the recovery of this species, the full understanding of its population genetic structure is necessary for taking appropriate management actions. However, genetic data on the use of nuclear loci in sterlet is still quite poor because microsatellite markers in sterlet that had been developed appeared to be polyploidy which add difficulties in studying the genetic of the sterlet. In this study, 24 tetranucleotide microsatellite markers were developed in sterlet from 160 microsatellite markers of the endangered Chinese sturgeon (Acipenser sinensis). Ten (ZHX76, ZHX64, Z194, Z217, Z184, Z242, Z250, Z258, Z268 and Z269) of the 24 loci showed disomic patterns while the rest loci showed tetrasomic patterns. In this paper, 24 microsatellite markers were characterized in 16 sterlet individuals and all of them were polymorphic with 2 to 7 alleles per locus. The Hardy-Weinberg departure value (d), polymorphic information content (PIC), the observed heterozygosity (HO), the Shannon-Wiener Diversity Indices (H') and the mean expected heterozygosity (HE) of all 24 polymorphic loci ranged from -0.334 to 0.484, 0.367 to 0.725, 0.438 to 1, 0.659 to 1.695, from 0.466 to 0.777, respectively. The markers described here will help in addressing practical problems such as the study of population genetics, conservation genetics and evolution in the polyploidy derivative nature of sterlet.Spatio-temporal patterns of the oceanic conditions and nearshore marine community in the Mid-Atlantic Bight (New Jersey, USA)https://peerj.com/preprints/279202019-08-282019-08-28Juan C Levesque
Oceanic environmental conditions influence, shape, and control the geographical range, spatial distribution, abundance, and size composition of marine fauna. Water temperature, salinity, dissolved oxygen, depth, and sediment type influence select fish life-history characteristics and community structure. Marine communities are vulnerable to major changes in environmental conditions, but the response and severity depends on various biological or ecological factors, such as resilience to stress or adaptation. Researchers around the world have predicted and documented numerous alterations in fish communities caused by ongoing significant physicochemical shifts associated with natural and potentially unnatural sources, but published studies describing the historical conditions are lacking for most regions around the world, including the coastal waters off New Jersey. Given the need to understand these processes, a multifaceted investigation was undertaken to describe, evaluate, and compare the oceanic conditions and nearshore marine fauna community off New Jersey during 1988 through 2015. Findings showed the oceanic conditions varied over time and space. Mean surface water temperature increased significantly about 0.6°C per decade, mean salinity decreased about 1.3 psu per decade, and dissolved oxygen increased 0.09 mg/l per decade. Over 20.4 million fish and invertebrates (1,338.3 mt) representing 214 (water temperature preference classified) species (not including unidentified species) were collected within 15 strata (areas: 12−26) off the coast of New Jersey from 1988 to 2015. Three marine fauna water temperature preference groups (coldwater-adapted, warmwater-adapted, and subtropic-adapted) were identified in the study area. The main coldwater-adapted species collected were longfin squid (Loligo pealei) (n = 2,225,975), Atlantic herring (Clupea harengus) (n = 544,032), and little skate (Leucoraja erinacea) (n = 316,356), while Atlantic butterfish (Peprilus triacanthus) (n = 2,873,138), scup (Stenotomus chrysops) (n = 1,318,569), and northern searobin (Prionotus carolinus) (n = 503,230) represented the warmwater-adapted group. Bay anchovy (Anchoa mitchilli) (n = 9,227,960), striped anchovy (Anchoa hepsetus) (n = 245,214), and Atlantic moonfish (Vomer setapinnis) (n = 38,691) denoted the subtropic-adapted group. Subtropic-adapted species were the most abundant and coldwater-adapted were the least abundant water temperature preference group. The estimated abundance of coldwater-adapted species declined, warmwater-adapted species slightly increased, and subtropic-adapted species decreased with time, which suggest the environmental conditions are influencing and thereby shifting the marine community.
Oceanic environmental conditions influence, shape, and control the geographical range, spatial distribution, abundance, and size composition of marine fauna. Water temperature, salinity, dissolved oxygen, depth, and sediment type influence select fish life-history characteristics and community structure. Marine communities are vulnerable to major changes in environmental conditions, but the response and severity depends on various biological or ecological factors, such as resilience to stress or adaptation. Researchers around the world have predicted and documented numerous alterations in fish communities caused by ongoing significant physicochemical shifts associated with natural and potentially unnatural sources, but published studies describing the historical conditions are lacking for most regions around the world, including the coastal waters off New Jersey. Given the need to understand these processes, a multifaceted investigation was undertaken to describe, evaluate, and compare the oceanic conditions and nearshore marine fauna community off New Jersey during 1988 through 2015. Findings showed the oceanic conditions varied over time and space. Mean surface water temperature increased significantly about 0.6°C per decade, mean salinity decreased about 1.3 psu per decade, and dissolved oxygen increased 0.09 mg/l per decade. Over 20.4 million fish and invertebrates (1,338.3 mt) representing 214 (water temperature preference classified) species (not including unidentified species) were collected within 15 strata (areas: 12−26) off the coast of New Jersey from 1988 to 2015. Three marine fauna water temperature preference groups (coldwater-adapted, warmwater-adapted, and subtropic-adapted) were identified in the study area. The main coldwater-adapted species collected were longfin squid (Loligo pealei) (n = 2,225,975), Atlantic herring (Clupea harengus) (n = 544,032), and little skate (Leucoraja erinacea) (n = 316,356), while Atlantic butterfish (Peprilus triacanthus) (n = 2,873,138), scup (Stenotomus chrysops) (n = 1,318,569), and northern searobin (Prionotus carolinus) (n = 503,230) represented the warmwater-adapted group. Bay anchovy (Anchoa mitchilli) (n = 9,227,960), striped anchovy (Anchoa hepsetus) (n = 245,214), and Atlantic moonfish (Vomer setapinnis) (n = 38,691) denoted the subtropic-adapted group. Subtropic-adapted species were the most abundant and coldwater-adapted were the least abundant water temperature preference group. The estimated abundance of coldwater-adapted species declined, warmwater-adapted species slightly increased, and subtropic-adapted species decreased with time, which suggest the environmental conditions are influencing and thereby shifting the marine community.Reproductive biology of Hybopsis amblops, the Bigeye Chub, in the Flint River of Alabamahttps://peerj.com/preprints/267192019-07-042019-07-04Crissy L TarverBruce W Stallsmith
Background. The purpose of this study was to establish a reproductive schedule and examine reproductive traits that shape fecundity of the Bigeye Chub, Hybopsis amblops Cyprinidae, in the Flint River system of north Alabama.
Methods. Life history traits associated with reproduction, growth, and maturation were assessed. Fish collections were made monthly from August, 2013, through July, 2014.
Results. The Bigeye Chub in Alabama primarily spawns in April and May as indicated by gonadosomatic index (GSI), ovarian condition and clutch size. Average GSI values began to rise in February, peaked in April and May at over 13% for females and 1.6% for males, and showed a steep decline from May to June for both sexes. Average clutch size was highest in April at 812. Diameter of the most mature oocyte stage averaged 0.74 mm, relatively small compared to other cyprinids found in the Flint River.
Discussion. The Bigeye Chub’s relatively large clutch size as a measure of fecundity places the species intermediate between opportunistic and periodic in the trilateral life history scheme of Winemiller and Rose. The species is apparently responding to a flow regime with a defined seasonality as well as predictability of flow and resources.
Background. The purpose of this study was to establish a reproductive schedule and examine reproductive traits that shape fecundity of the Bigeye Chub, Hybopsis amblops Cyprinidae,in the Flint River system of north Alabama.Methods. Life history traits associated with reproduction, growth, and maturation were assessed. Fish collections were made monthly from August, 2013, through July, 2014.Results. The Bigeye Chub in Alabama primarily spawns in April and May as indicated by gonadosomatic index (GSI), ovarian condition and clutch size. Average GSI values began to rise in February, peaked in April and May at over 13% for females and 1.6% for males, and showed a steep decline from May to June for both sexes. Average clutch size was highest in April at 812. Diameter of the most mature oocyte stage averaged 0.74 mm, relatively small compared to other cyprinids found in the Flint River.Discussion. The Bigeye Chub’s relatively large clutch size as a measure of fecundity places the species intermediate between opportunistic and periodic in the trilateral life history scheme of Winemiller and Rose. The species is apparently responding to a flow regime with a defined seasonality as well as predictability of flow and resources.The status and trends of small cetacean landings at Dixcove artisanal fishing port, western Ghanahttps://peerj.com/preprints/277492019-05-212019-05-21Patrick K Ofori-DansonJoseph DebrahKoen Van Waerebeek
One of the largest documented takes of small cetaceans in western Africa occurs in Western regional coastal waters of Ghana. This temporally coincided with steadily decreasing catches of finfish, especially small pelagics (sardinellas, anchovies, mackerel) over the past decades, attributed to both climate change and indiscriminate exploitation methods. Dixcove, a key fishing port for cetacean landings was surveyed during 96 days between 12 September -17 December 2018. Our goal was to update insights from our earlier surveys, especially on catch rates, catch per unit effort and species composition. A total of 57 delphinids of 10 species were observed landed: Stenella attenuata (28.1%), Stenella clymene (17.5%), Lagenodelphis hosei (10.5%), Steno bredanensis (10.5%), unidentified stenellids (8.8%), Grampus griseus (3.5%), Delphinus sp. (3.5%), Pseudorca crassidens (3.5%) and single specimens of Tursiops truncatus, Stenella longirostris and Stenella frontalis. The observed cetacean catch per diem (cpd =0.59) at Dixcove was low compared to earlier rates for this port (e.g. cpd =2.82, in 2013-2014). However, fishing effort, measured as the number of canoes landing per diem (range 0-25; mean= 8.82 ± 6.05; n=22) was also reduced. Poor fish catches forced many canoes to remain in port. The prevalence in landings of common bottlenose dolphins and common dolphins has significantly decreased in the period 2000-2018. The prevalence of Fraser's dolphins and false killer whales increased. Indications are that a higher proportion of cetacean carcasses may be utilised offshore as shark bait. Hooks baited with cetacean parts are deployed in auxiliary longlines set longside large-mesh drift gillnets with a shark aggregating purpose, a first report in Africa. Shore-based incidental sightings of humpback whales suggest the potential for small scale whale-watching ecotourism in Ghanaian coastal waters, as pertains in the nearby waters of the Republic of Benin.
One of the largest documented takes of small cetaceans in western Africa occurs in Western regional coastal waters of Ghana. This temporally coincided with steadily decreasing catches of finfish, especially small pelagics (sardinellas, anchovies, mackerel) over the past decades, attributed to both climate change and indiscriminate exploitation methods. Dixcove, a key fishing port for cetacean landings was surveyed during 96 days between 12 September -17 December 2018. Our goal was to update insights from our earlier surveys, especially on catch rates, catch per unit effort and species composition. A total of 57 delphinids of 10 species were observed landed: Stenella attenuata (28.1%), Stenella clymene (17.5%), Lagenodelphis hosei (10.5%), Steno bredanensis (10.5%), unidentified stenellids (8.8%), Grampus griseus (3.5%), Delphinus sp. (3.5%), Pseudorca crassidens (3.5%) and single specimens of Tursiops truncatus, Stenella longirostris and Stenella frontalis. The observed cetacean catch per diem (cpd =0.59) at Dixcove was low compared to earlier rates for this port (e.g. cpd =2.82, in 2013-2014). However, fishing effort, measured as the number of canoes landing per diem (range 0-25; mean= 8.82 ± 6.05; n=22) was also reduced. Poor fish catches forced many canoes to remain in port. The prevalence in landings of common bottlenose dolphins and common dolphins has significantly decreased in the period 2000-2018. The prevalence of Fraser's dolphins and false killer whales increased. Indications are that a higher proportion of cetacean carcasses may be utilised offshore as shark bait. Hooks baited with cetacean parts are deployed in auxiliary longlines set longside large-mesh drift gillnets with a shark aggregating purpose, a first report in Africa. Shore-based incidental sightings of humpback whales suggest the potential for small scale whale-watching ecotourism in Ghanaian coastal waters, as pertains in the nearby waters of the Republic of Benin.Characterization of the karyotype and accumulation of repetitive sequences in Australian Darling hardyhead Craterocephalus amniculus (Atheriniformes, Teleostei)https://peerj.com/preprints/276882019-04-262019-04-26Zuzana MajtánováKarl G MoyPeter J UnmackPetr RábTariq Ezaz
Belonging to the order Atheriniformes, Craterocephalus is one of the most widespread genera of freshwater fishes in Australia, spanning along the northern coast from central Western Australia to central New South Wales and across the Murray-Darling and Lake Eyre basins. In this study, both conventional cytogenetic techniques (Giemsa, C-banding), CMA3/DAPI staining), and fluorescence in situ hybridization (FISH) with telomeric DNA and rDNA probes were used to examine, the karyotypes and other chromosomal characteristics of Darling hardyhead (Craterocephalus amniculus) from New South Wales, Australia. We identified diploid chromosome number 2n = 48 (NF = 58) in all studied individuals. FISH with rDNA probe showed a nonsyntenic pattern, with signals on one pair of subtelocentric chromosomes for 28S rDNA and one pair of submetacentric chromosomes for 5S rDNA. C-banding displayed the accumulation of constitutive heterochromatin in the centromeric regions of approximately 40 chromosomes. CMA3/DAPI fluorescence staining revealed extremely GC-rich signals in pericentromeric region of one submetacentric chromosomal pair with size polymorphism. We detected telomeric signals at the end of all chromosomes and no interstitial signals.
Belonging to the order Atheriniformes, Craterocephalus is one of the most widespread genera of freshwater fishes in Australia, spanning along the northern coast from central Western Australia to central New South Wales and across the Murray-Darling and Lake Eyre basins. In this study, both conventional cytogenetic techniques (Giemsa, C-banding), CMA3/DAPI staining), and fluorescence in situ hybridization (FISH) with telomeric DNA and rDNA probes were used to examine, the karyotypes and other chromosomal characteristics of Darling hardyhead (Craterocephalus amniculus) from New South Wales, Australia. We identified diploid chromosome number 2n = 48 (NF = 58) in all studied individuals. FISH with rDNA probe showed a nonsyntenic pattern, with signals on one pair of subtelocentric chromosomes for 28S rDNA and one pair of submetacentric chromosomes for 5S rDNA. C-banding displayed the accumulation of constitutive heterochromatin in the centromeric regions of approximately 40 chromosomes. CMA3/DAPI fluorescence staining revealed extremely GC-rich signals in pericentromeric region of one submetacentric chromosomal pair with size polymorphism. We detected telomeric signals at the end of all chromosomes and no interstitial signals.The phylogenetic origin and evolution of acellular bone in teleost fishes: insights into osteocyte function in bone metabolismhttps://peerj.com/preprints/274062019-02-132019-02-13Donald DavesneFrançois J. MeunierArmin D. SchmittMatt FriedmanOlga OteroRoger B. J. Benson
Vertebrate bone is composed of three main cell types: osteoblasts, osteoclasts and osteocytes, the latter being by far the most numerous. Osteocytes are thought to play a fundamental role in bone physiology and homeostasis, however they are entirely absent in most extant species of teleosts, a group that comprises the vast majority of bony ‘fishes’, and approximately half of vertebrates. Understanding how this acellular (anosteocytic) bone appeared and was maintained in such an important vertebrate group has important implications for our understanding of the function and evolution of osteocytes. Nevertheless, although it is clear that cellular bone is ancestral for teleosts, it has not been clear in which specific subgroup the osteocytes were lost. This review aims at clarifying the phylogenetic distribution of cellular and acellular bone in teleosts, to identify its precise origin, reversals to cellularity, and their implications. We surveyed the bone type for more than 600 fossil and extant ray-finned fish species and optimised the results on recent large-scale molecular phylogenetic trees, estimating ancestral states. We find that acellular bone is a probable synapomorphy of Euteleostei, a group uniting approximately two-thirds of teleost species. We also confirm homoplasy in these traits: acellular bone occurs in some non-euteleosts (although rarely), and cellular bone was reacquired several times independently within euteleosts, in salmons and relatives, tunas and the opah (Lampris sp.). The occurrence of peculiar ecological (e.g. anadromous migration) and physiological (e.g. red-muscle endothermy) strategies in these lineages might explain the reacquisition of osteocytes. Our review supports that the main contribution of osteocytes in teleost bone is to mineral homeostasis (via osteocytic osteolysis) and not to strain detection or bone remodelling, helping to clarify their role in bone physiology.
Vertebrate bone is composed of three main cell types: osteoblasts, osteoclasts and osteocytes, the latter being by far the most numerous. Osteocytes are thought to play a fundamental role in bone physiology and homeostasis, however they are entirely absent in most extant species of teleosts, a group that comprises the vast majority of bony ‘fishes’, and approximately half of vertebrates. Understanding how this acellular (anosteocytic) bone appeared and was maintained in such an important vertebrate group has important implications for our understanding of the function and evolution of osteocytes. Nevertheless, although it is clear that cellular bone is ancestral for teleosts, it has not been clear in which specific subgroup the osteocytes were lost. This review aims at clarifying the phylogenetic distribution of cellular and acellular bone in teleosts, to identify its precise origin, reversals to cellularity, and their implications. We surveyed the bone type for more than 600 fossil and extant ray-finned fish species and optimised the results on recent large-scale molecular phylogenetic trees, estimating ancestral states. We find that acellular bone is a probable synapomorphy of Euteleostei, a group uniting approximately two-thirds of teleost species. We also confirm homoplasy in these traits: acellular bone occurs in some non-euteleosts (although rarely), and cellular bone was reacquired several times independently within euteleosts, in salmons and relatives, tunas and the opah (Lampris sp.). The occurrence of peculiar ecological (e.g. anadromous migration) and physiological (e.g. red-muscle endothermy) strategies in these lineages might explain the reacquisition of osteocytes. Our review supports that the main contribution of osteocytes in teleost bone is to mineral homeostasis (via osteocytic osteolysis) and not to strain detection or bone remodelling, helping to clarify their role in bone physiology.Seaweed culture for nutrient abatement in Spermonde watershttps://peerj.com/preprints/275042019-01-292019-01-29Andriani NasirMuhammad Ikbal IllijasMirta TeichbergMuhammad Lukman
The coastal waters of the Strait of Makassar are classified as a productive coastal area, in which there are mangrove ecosystems, seagrass beds and Spermonde coral reefs that play a crucial role in sustaining the economic life of coastal communities and food security. Our previous results have calculated the outflow of nutrient land to sea with nitrate concentrations ranging from 0.01-0.44 mg/L and phosphate 0.04-0.35 mg/L. This condition has caused coastal waters of permonde to be eutrophicated with the occurrence of mass death of several species of fish and the emergence of dangerous microalgae species. This study aims to calculate the current nutrient value in the area of seaweed cultivation as a biological absorber. Based on the interim results, the decrease or absorption of nutrients by seaweed ranges from 0.08-1.55 mg/L-nitrate and 0.01-0.71 mg/L-phosphate.
The coastal waters of the Strait of Makassar are classified as a productive coastal area, in which there are mangrove ecosystems, seagrass beds and Spermonde coral reefs that play a crucial role in sustaining the economic life of coastal communities and food security. Our previous results have calculated the outflow of nutrient land to sea with nitrate concentrations ranging from 0.01-0.44 mg/L and phosphate 0.04-0.35 mg/L. This condition has caused coastal waters of permonde to be eutrophicated with the occurrence of mass death of several species of fish and the emergence of dangerous microalgae species. This study aims to calculate the current nutrient value in the area of seaweed cultivation as a biological absorber. Based on the interim results, the decrease or absorption of nutrients by seaweed ranges from 0.08-1.55 mg/L-nitrate and 0.01-0.71 mg/L-phosphate.Conservation and diversity in expression of candidate genes regulating socially-induced female-male sex change in wrasseshttps://peerj.com/preprints/274612019-01-022019-01-02Jodi T ThomasErica V ToddSimon MuncasterP Mark LokmanErin L DamsteegtHui LiuKiyoshi SoyanoFlorence GleonnecMelissa S LammJohn R GodwinNeil J Gemmell
Fishes exhibit remarkably diverse, and plastic, patterns of sexual development, most striking of which is sequential hermaphroditism, where individuals readily reverse sex in adulthood. How this stunning example of phenotypic plasticity is controlled at a genetic level remains poorly understood. Several genes have been implicated in regulating sex change, yet the degree to which a conserved genetic machinery orchestrates this process has not yet been addressed. Using captive and in-the-field social manipulations to initiate sex change, combined with a comparative qPCR approach, we compared expression patterns of four candidate regulatory genes among three species of wrasses (Labridae) - a large and diverse teleost family where female-to-male sex change is pervasive, socially-cued, and likely ancestral. Expression in brain and gonadal tissues were compared among the iconic tropical bluehead wrasse (Thalassoma bifasciatum) and the temperate spotty (Notolabrus celidotus) and kyusen (Parajulus poecilepterus) wrasses. In all three species, cyp19a1a (encoding gonadal aromatase that converts androgens to oestrogens) and amh (encoding anti-müllerian hormone that primarily regulates male germ cell development) were downregulated and upregulated, respectively, at the initiation of gonadal sex change, and may act concurrently to orchestrate ovary-testis transformation. In the brain, our data argue against a role for brain aromatase (cyp19a1b) in initiating behavioural sex change, as its expression trailed behavioural changes. However, we find that isotocin (it, that regulates teleost socio-sexual behaviours) expression correlated with dominant male-specific behaviours in the bluehead wrasse, suggesting it upregulation mediates the rapid behavioural sex change characteristic of blueheads and other tropical wrasses. However, it expression was not sex-biased in temperate spotty and kyusen wrasses, where sex change is more protracted and social groups may be less tightly-structured. Together, these findings suggest that while key components of the molecular machinery controlling gonadal sex change are phylogenetically conserved among wrasses, neural pathways governing behavioural sex change may be more variable.
Fishes exhibit remarkably diverse, and plastic, patterns of sexual development, most striking of which is sequential hermaphroditism, where individuals readily reverse sex in adulthood. How this stunning example of phenotypic plasticity is controlled at a genetic level remains poorly understood. Several genes have been implicated in regulating sex change, yet the degree to which a conserved genetic machinery orchestrates this process has not yet been addressed. Using captive and in-the-field social manipulations to initiate sex change, combined with a comparative qPCR approach, we compared expression patterns of four candidate regulatory genes among three species of wrasses (Labridae) - a large and diverse teleost family where female-to-male sex change is pervasive, socially-cued, and likely ancestral. Expression in brain and gonadal tissues were compared among the iconic tropical bluehead wrasse (Thalassoma bifasciatum) and the temperate spotty (Notolabrus celidotus) and kyusen (Parajulus poecilepterus) wrasses. In all three species, cyp19a1a (encoding gonadal aromatase that converts androgens to oestrogens) and amh (encoding anti-müllerian hormone that primarily regulates male germ cell development) were downregulated and upregulated, respectively, at the initiation of gonadal sex change, and may act concurrently to orchestrate ovary-testis transformation. In the brain, our data argue against a role for brain aromatase (cyp19a1b)in initiating behavioural sex change, as its expression trailed behavioural changes. However, we find that isotocin (it, that regulates teleost socio-sexual behaviours)expression correlated with dominant male-specific behaviours in the bluehead wrasse, suggesting it upregulation mediates the rapid behavioural sex change characteristic of blueheads and other tropical wrasses. However, it expressionwas not sex-biased in temperate spotty and kyusen wrasses, where sex change is more protracted and social groups may be less tightly-structured. Together, these findings suggest that while key components of the molecular machinery controlling gonadal sex change are phylogenetically conserved among wrasses, neural pathways governing behavioural sex change may be more variable.Adult zebrafish euthanasia: efficacy of anaesthesia overdose versus rapid coolinghttps://peerj.com/preprints/274322018-12-172018-12-17Jorge M FerreiraI Anna S OlssonAna M Valentim
The rapid increase in zebrafish use needs to be accompanied by research into refinement of procedures, such as euthanasia. The EU directive lists three possible euthanasia methods for fish: anaesthetic overdose, electrical stunning and concussion. However, for a small fish like zebrafish, concussion and electrical stunning are difficult to perform, leaving anaesthetic overdose as the only realistic option. Thus, more tailored solutions need to be found for this small tropical water species. Our aim was to test the efficacy of different anaesthetics overdose and of the rapid cooling method to kill adult zebrafish. Adult mixed-sex AB zebrafish (n= 12) were randomly assigned to: 250mg/L MS222; 20 mg/L propofol + 100 mg/L lidocaine; 6 mg/L etomidate; 50 mg/L clove oil; rapid cooling (water at 2-4º C). Two minutes after opercular movement ceased, the animals were transferred to clean water to assess if they could recover. Zebrafish euthanized with rapid cooling ceased the opercular movements significantly quicker compared with the other groups, and etomidate-treated animals took longer to die. No zebrafish recovered after being placed in clean water. All protocols used were efficacious to achieve euthanasia, but rapid cooling was consistently the fastest and so more efficient. Further studies evaluating animal welfare and the quality of the biological samples are needed to refine the rapid cooling protocol before recommendations can be made to change legislation to include this as a method for euthanasia for small tropical fish.
The rapid increase in zebrafish use needs to be accompanied by research into refinement of procedures, such as euthanasia. The EU directive lists three possible euthanasia methods for fish: anaesthetic overdose, electrical stunning and concussion. However, for a small fish like zebrafish, concussion and electrical stunning are difficult to perform, leaving anaesthetic overdose as the only realistic option. Thus, more tailored solutions need to be found for this small tropical water species. Our aim was to test the efficacy of different anaesthetics overdose and of the rapid cooling method to kill adult zebrafish. Adult mixed-sex AB zebrafish (n= 12) were randomly assigned to: 250mg/L MS222; 20 mg/L propofol + 100 mg/L lidocaine; 6 mg/L etomidate; 50 mg/L clove oil; rapid cooling (water at 2-4º C). Two minutes after opercular movement ceased, the animals were transferred to clean water to assess if they could recover. Zebrafish euthanized with rapid cooling ceased the opercular movements significantly quicker compared with the other groups, and etomidate-treated animals took longer to die. No zebrafish recovered after being placed in clean water. All protocols used were efficacious to achieve euthanasia, but rapid cooling was consistently the fastest and so more efficient. Further studies evaluating animal welfare and the quality of the biological samples are needed to refine the rapid cooling protocol before recommendations can be made to change legislation to include this as a method for euthanasia for small tropical fish.