Attachment of eggs by Lamellodiscus acanthopagri (Monogenea: Diplectanidae) to the gills of Acanthopagrus australis (Pisces: Sparidae), with evidence for auto-infection and postsettlement migration

1994 ◽  
Vol 72 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Frank R. Roubal
Keyword(s):  
Population Size ◽  
Water Column ◽  
Gill Filament ◽  
Infection Intensity ◽  
Middle Zone ◽  
Epithelial Hyperplasia ◽  
Basal Zone ◽  
Sparid Fish ◽  
In The Wild ◽  
Low Levels

The eggs of the diplectanid monogenean Lamellodiscus acanthopagri are T-shaped with a thornlike filament that is inserted into the epithelium between respiratory lamellae on the gills of the sparid fish Acanthopagrus australis. The resulting epithelial hyperplasia eventually sheds the egg. The most extensive hyperplasia is always associated with mature and hatched eggs. Few developing eggs are shed from the gills. Most eggs are attached in the basal third of the gill filament irrespective of infection intensity. Most adult and juvenile parasites are in this basal zone at low levels of infection, but predominate in the middle zone at higher infections. A ciliated oncomiracidium hatches from the egg and may attach nearby. As it develops, the parasite apparently moves distally on the gill filament. Only a few fish in the wild have high intensities of infection by L. acanthopagri compared with six other species of monogenean on, A. australis. Auto-infection occurs at all levels of infection but dispersal of larvae to the water column may limit population size on host individuals.

Gill Surface-Area and Its Components in the Yellowfin Bream, Acanthopagrus-Australis (Gunther) (Pisces, Sparidae)

1987 ◽  
Vol 35 (1) ◽  
pp. 25 ◽  
Author(s):  
FR Roubal
Keyword(s):  
Surface Area ◽  
Gill Filament ◽  
Weighting Factor ◽  
Head Length ◽  
Regression Equations ◽  
Middle Zone ◽  
Filament Length ◽  
Basal Zone ◽  
Gill Filaments ◽  
Gill Surface Area

As head length (HL) of Acanthopagrus australis increases, fewer gill filaments are added, total gill filament length (TFL) increases linearly, and total gill surface area (TSA) increases exponentially. Changes in surface area components [surface area per lamella (SA), distance between adjacent lamellae (DBT) and number of lamellae per zone on one side of the filament (NPZ)] with increasing HL were examined in the distal, middle and basal zones (relative lengths 3:10:1) of a corresponding filament on the external hemibranch of the four gill arches. SA was the smallest in the basal zone and largest in the middle zone; DBT was greatest in the distal zone and smallest in the basal zone; SA and DBT increased at similar rates in different gill arches within the distal and middle zones but at different rates in each zone within an arch; growth of NPZ in the middle zone differed among gill arches but did not in the distal zone. Surface area of lamellae in the middle zone contributed most to increasing TSA. Compared with other fish of intermediate activity, the estimate of TSA for A. australis was smaller than expected; although DBT and TFL were as expected, SA was smaller than expected; possible reasons include method of measurement in situ, shrinkage caused by fixation, and absence of a weighting factor. The method employed enables large numbers of lamellae and filaments in a large number of fish to be measured, and enables regression equations to be derived that relate surface area per filament zone to head length and filament length in order to estimate the loss of surface area caused by ectoparasites.

scholarly journals Introgression of the sesquiterpene biosynthesis from Solanum habrochaites to cultivated tomato offers insights into trichome morphology and arthropod resistance

Planta ◽  
2021 ◽  
Vol 254 (1) ◽  
Author(s):  
Rodrigo Therezan ◽  
Ruy Kortbeek ◽  
Eloisa Vendemiatti ◽  
Saioa Legarrea ◽  
Severino M. de Alencar ◽  
...  
Keyword(s):  
Glandular Trichomes ◽  
Pest Resistance ◽  
Chromosome 8 ◽  
Cavity Size ◽  
Solanum Habrochaites ◽  
Genetic Components ◽  
Internal Storage ◽  
In The Wild ◽  
Low Levels ◽  
Trichome Morphology

Abstract Main conclusion Cultivated tomatoes harboring the plastid-derived sesquiterpenes from S. habrochaites have altered type-VI trichome morphology and unveil additional genetic components necessary for piercing-sucking pest resistance. Abstract Arthropod resistance in the tomato wild relative Solanum habrochaites LA1777 is linked to specific sesquiterpene biosynthesis. The Sesquiterpene synthase 2 (SsT2) gene cluster on LA1777 chromosome 8 controls plastid-derived sesquiterpene synthesis. The main genes at SsT2 are Z-prenyltransferase (zFPS) and Santalene and Bergamotene Synthase (SBS), which produce α-santalene, β-bergamotene, and α-bergamotene in LA1777 round-shaped type-VI glandular trichomes. Cultivated tomatoes have mushroom-shaped type-VI trichomes with much smaller glands that contain low levels of monoterpenes and cytosolic-derived sesquiterpenes, not presenting the same pest resistance as in LA1777. We successfully transferred zFPS and SBS from LA1777 to cultivated tomato (cv. Micro-Tom, MT) by a backcrossing approach. The trichomes of the MT-Sst2 introgressed line produced high levels of the plastid-derived sesquiterpenes. The type-VI trichome internal storage-cavity size increased in MT-Sst2, probably as an effect of the increased amount of sesquiterpenes, although it was not enough to mimic the round-shaped LA1777 trichomes. The presence of high amounts of plastid-derived sesquiterpenes was also not sufficient to confer resistance to various tomato piercing-sucking pests, indicating that the effect of the sesquiterpenes found in the wild S. habrochaites can be insect specific. Our results provide for a better understanding of the morphology of S. habrochaites type-VI trichomes and paves the way to obtain insect-resistant tomatoes.

O6-methylguanine-DNA methyltransferase in wild-type and ada mutants of Escherichia coli

1982 ◽  
Vol 152 (1) ◽  
pp. 534-537
Author(s):  
S Mitra ◽  
B C Pal ◽  
R S Foote
Keyword(s):  
Escherichia Coli ◽  
Dna Methyltransferase ◽  
Wild Type ◽  
E Coli ◽  
Methylguanine Dna Methyltransferase ◽  
Synthetic Dna ◽  
In The Wild ◽  
Low Levels ◽  
Enzyme Molecules ◽  
Dna Substrate

O(6)-Methylguanine-DNA methyltransferase is induced in Escherichia coli during growth in low levels of N-methyl-N'-nitro-N-nitrosoguanidine. We have developed a sensitive assay for quantitating low levels of this activity with a synthetic DNA substrate containing 3H-labeled O(6)-methylguanine as the only modified base. Although both wild-type and adaptation-deficient (ada) mutants of E. coli contained low but comparable numbers (from 13 to 60) of the enzyme molecules per cell, adaptation treatment caused a significant increase of the enzyme in the wild type but not in the ada mutants, suggesting that the ada mutation is in a regulatory locus and not in the structural gene for the methyltransferase.

Assessing the status of a threatened island endemic, Ctenosaura oedirhina, on Roatán, Honduras

2020 ◽  
Vol 47 (2) ◽  
pp. 137
Author(s):  
A. B. C. Goode ◽  
S. A. Pasachnik ◽  
T. L. Maple
Keyword(s):  
Population Size ◽  
Distance Sampling ◽  
Adult Mortality ◽  
Isolated Populations ◽  
Cultural Traditions ◽  
Island Endemic ◽  
Wild Fauna ◽  
The Status ◽  
In The Wild ◽  
Study Sites

Abstract Context Organisms living in small, isolated populations with very restricted ranges are at high risk of extirpation due to various direct and indirect forces than mainland populations. Roatán spiny-tailed iguanas (Ctenosaura oedirhina) are endemic to the 146-km2 island of Roatán, Honduras. Harvesting for consumption, fragmentation of habitat and predation by domestic animals threaten the existence of this lizard. This species is federally protected in Honduras; however, enforcement is rare. These iguanas are also listed as Endangered by the International Union for Conservation of Nature (IUCN) and are on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This species is geographically and genetically isolated into small subpopulations that are declining in density. Aims To estimate the population size of Roatán spiny-tailed iguanas (Ctenosaura oedirhina) on the island of Roatán, Honduras. Methods Distance sampling surveys have been used to monitor this species since 2012, and have been used to determine population density at five study sites. Estimates of density at those sites and across the island were used to calculate the population size of this species. Key results The present study elucidates that the high-density populations remaining are declining. The current population size is estimated to be 3759 (95% CI=1406–12616) individuals within the study sites, with 730 additional iguanas potentially outside of the study sites. Conclusions If the current level of decline continues, this species may become extirpated from some locations on Roatán, and go extinct in the wild. Although Honduras does have laws protecting this species and other wildlife, enforcement must be enhanced. Implications Lack of enforced protection for this species allows poaching for consumption to continue, which has been shown to alter its distribution and cause increased adult mortality. Local customs value the consumption of this species, creating a delicate management situation. Recommendations include strategies that mitigate the threat posed by consumption and increase enforcement of the current laws, while acknowledging cultural traditions.

The relationship between IgA activity against 4th-stage larvae and density-dependent effects on the number of 4th-stage larvae ofTeladorsagia circumcinctain naturally infected sheep

Parasitology ◽  
2004 ◽  
Vol 129 (3) ◽  
pp. 363-369 ◽  
Author(s):  
M. J. STEAR ◽  
K. BAIRDEN ◽  
G. T. INNOCENT ◽  
S. MITCHELL ◽  
S. STRAIN ◽  
...  
Keyword(s):  
Negative Binomial Distribution ◽  
Binomial Distribution ◽  
Negative Binomial ◽  
Infection Intensity ◽  
Intensity Of Infection ◽  
Mean Intensity ◽  
Teladorsagia Circumcincta ◽  
The Mean ◽  
Low Levels ◽  
The Relationship

The number ofTeladorsagia circumcincta4th-stage larvae in naturally infected lambs from a single farm varied among lambs and among different years. Within each year the distribution of 4th-stage larvae among lambs was similar to that expected from a negative binomial distribution. The ratio of 4th-stage larvae to adultT. circumcinctawas low in two years with a low mean intensity of infection but high in two years with a higher mean intensity of infection. The negative binomial distribution is defined by the mean and byk, a parameter that measures dispersion;kwas low when mean infection intensity was low but higher when mean infection intensity was high. Askis an inverse index of overdispersion this indicated that the distribution of 4th-stage larvae was more overdispersed at low levels of infection. In a combined analysis, the number of adultT. circumcinctaand the plasma IgA activity against 4th-stage larvae were both associated with increased numbers of 4th-stage larvae. There was a statistical interaction between the number of adults and IgA activity that moderated their combined effect.

scholarly journals Effective population size and tests of neutrality at cytoplasmic genes in Arabidopsis

2008 ◽  
Vol 90 (1) ◽  
pp. 119-128 ◽  
Author(s):  
STEPHEN I. WRIGHT ◽  
NARDIN NANO ◽  
JOHN PAUL FOXE ◽  
VAQAAR-UN NISA DAR
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Likelihood Estimation ◽  
Composite Likelihood ◽  
Nuclear Genes ◽  
Nucleotide Polymorphism ◽  
Effective Population ◽  
Arabidopsis Lyrata ◽  
Tests Of Neutrality ◽  
Low Levels

SummaryCytoplasmic genomes typically lack recombination, implying that genetic hitch-hiking could be a predominant force structuring nucleotide polymorphism in the chloroplast and mitochondria. We test this hypothesis by analysing nucleotide polymorphism data at 28 loci across the chloroplast and mitochondria of the outcrossing plant Arabidopsis lyrata, and compare patterns with multiple nuclear loci, and the highly selfing Arabidopsis thaliana. The maximum likelihood estimate of the ratio of effective population size at cytoplasmic relative to nuclear genes in A. lyrata does not depart from the neutral expectation of 0·5. Similarly, the ratio of effective size in A. thaliana is close to unity, the neutral expectation for a highly selfing species. The results are thus consistent with neutral organelle polymorphism in these species or with comparable effects of hitch-hiking in both cytoplasmic and nuclear genes, in contrast to the results of recent studies on gynodioecious taxa. The four-gamete test and composite likelihood estimation provide evidence for very low levels of recombination in the organelles of A. lyrata, although permutation tests do not suggest that adjacent polymorphic sites are more closely linked than more distant sites across the two genomes, suggesting that mutation hotspots or very low rates of gene conversion could explain the data.

scholarly journals Differential turnover of the multiple processed transcripts of the Escherichia coli focA-pflB operon

Microbiology ◽  
2006 ◽  
Vol 152 (8) ◽  
pp. 2197-2205 ◽  
Author(s):  
R. Gary Sawers
Keyword(s):  
Escherichia Coli ◽  
Transcriptional Control ◽  
Positive Control ◽  
Exponential Phase ◽  
Anaerobic Growth ◽  
Rnase E ◽  
Coordinate Regulation ◽  
In The Wild ◽  
Low Levels ◽  
Post Transcriptional Regulation

Expression of the anaerobically inducible focA-pflB operon of Escherichia coli is subject to complex transcriptional and post-transcriptional control, which generates eight transcripts whose 5′ ends span ∼1.2 kb. All eight transcripts have the same 3′ end. The 5′ ends of three of the transcripts, termed 6, 6a and 7, are located upstream of the operon. The promoters generating transcripts 6 and 7 are anaerobically regulated by FNR and ArcA∼P, while promoter 6a is constitutively active. The 5′ ends of the other five transcripts are all located within the operon. Most of the 5′ ends of these operon-internal transcripts result from RNA polymerase-dependent processing of the three longer primary transcripts, 6, 6a and 7. Here, it is demonstrated that subsequent to, and distinct from, these processing events, post-transcriptional modification of these transcripts also occurs through the action of the endoribonuclease RNase E. Transcripts 6 and 7 exhibit differential stability with half-lives of 1 and 5 min, respectively. Transcript 7, which has the longer half-life, is the longest transcript of the operon and has a ∼340 base untranslated leader. Two of the operon-internal transcripts, 4 and 5, also have comparatively short half-lives in the wild-type, which are significantly increased in a mutant with impaired RNase E activity. A precursor-product relationship is observed between the longer transcripts 3–7 and transcripts 1 and 2. The 5′ ends of transcripts 1 and 2 are closest to the pflB gene and have half-lives of approximately 7–8 min. The consequence of this regulation is an accumulation of full-length pflB transcript and comparably low levels of dicistronic transcript. This ensures different levels of synthesis of the formate transporter FocA and pyruvate formate-lyase during anaerobic growth, while maintaining coordinate regulation. Transcript analysis throughout the growth phase revealed that maximal anaerobic expression of the focA-pflB operon was restricted to exponentially growing cells. Expression of transcript 7 peaked in early to mid-exponential phase, while the levels of transcript 6 steadily accumulated toward the late-exponential phase of growth. Taken together, these findings indicate that although subject to common positive control by ArcA∼P and FNR, the transcripts generated by promoters 6 and 7 are subject to differential temporal and post-transcriptional regulation.

THE IRRIGATION OF THE GILLS IN FISHES: II. EFFICIENCY OF OXYGEN UPTAKE IN RELATION TO RESPIRATORY FLOW ACTIVITY AND CONCENTRATIONS OF OXYGEN AND CARBON DIOXIDE

1962 ◽  
Vol 40 (5) ◽  
pp. 817-862 ◽  
Author(s):  
Richard L. Saunders
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Gill Filament ◽  
Saturated Water ◽  
Respiratory Flow ◽  
Ambient Oxygen ◽  
Low Levels ◽  
Flow Activity ◽  
Ambient Levels

Respiratory volumes, percentage utilizations of oxygen, and rates of oxygen consumption were measured in non-swimming and swimming white suckers, brown bullheads, and carp under various ambient levels of oxygen and carbon dioxide. Up to 85% of the oxygen in the inspired water is removed by quietly breathing fish. Generally, high respiratory volumes are associated with low percentage utilizations of oxygen and vice versa. At high respiratory volumes carp remove about twice as much oxygen from the inspired water as do suckers and bullheads. Respiratory volumes are increased by as much as 30 times over the volume for quiet respiration by low levels of oxygen or high levels of carbon dioxide. Respiratory volumes of swimming fish are greater than those of non-swimming, rested fish in air-saturated water but they are not as high as those of non-swimming fish exposed to low ambient oxygen levels.The effects of moderate increases in ambient carbon dioxide on non-swimming fish may be temporary only. If the rise in the pCO2 is slight to moderate, the percentage utilizations of oxygen at given respiratory volumes are at first depressed but may return, after 3 to 5 hours, to the levels they held before the pCO2 was raised. Actively swimming fish respond to any increase in the pCO2 by permanently increased breathing rates and decreased percentage utilizations of oxygen and rates of oxygen consumption.The number of respiratory units or lamellae per millimeter of gill filament in suckers, bullheads, and carp weighing 200 g are about 14, 10, and 20 respectively, but the total numbers and areas of lamellae are such that total gill areas are nearly identical among these three species.

scholarly journals Detection and phylogenetic analysis of adenoviruses occurring in a single anole species

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5521 ◽  
Author(s):  
Sofia R. Prado-Irwin ◽  
Martijn van de Schoot ◽  
Anthony J. Geneva
Keyword(s):  
Morbidity And Mortality ◽  
Island Population ◽  
Disease Dynamics ◽  
Cayman Islands ◽  
The Bahamas ◽  
Wide Range ◽  
In The Wild ◽  
Different Populations ◽  
Low Levels ◽  
Low Prevalence

Adenoviruses (AdVs) infect a wide range of hosts, and they have undergone recent and ancient host transfers multiple times. In reptiles, AdVs have been found in many captive individuals, and have been implicated in morbidity and mortality in several species. Yet the pathogenicity, transmission, phylogenetic distribution, and source of AdVs in the environment are still unknown. We therefore chose to opportunistically sample deceased captive Anolis sagrei individuals that were collected from different populations in the Bahamas and the Cayman Islands, as well as fecal samples from one island population, to explore the disease dynamics and diversity of adenovirus infecting A. sagrei populations. We found that adenovirus infection was present in our captive colony at low prevalence (26%), and was likely not the primary cause of observed morbidity and mortality. Among the 10 individuals (out of 38 sampled) which tested positive for adenovirus, we identified four adenovirus clades, several of which are distantly related, despite the close relationships of the A. sagrei host populations. These results suggest that while adenovirus may not be highly prevalent in the wild, it is present at low levels across much of the range of A. sagrei. It may undergo frequent host switching across both deep and shallow host divergences.

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