Number Of Mature Females Research Articles

Impact of Ecological Friendly Treatments on Meloidogyne incognita Infected Ground Cherry

The main efforts of scientists to reduce appliance of nematicides that are commonly found in the markets, led to an increase in the demand safety, effective and environment friendly alternatives. Hence, the present ​​research aims to test three safety and effective substances (Potassium silicate; Furfural and Albendazole) single or in combination in the control of root-knot nematode,Meloidogyne incognita infecting ground cherry plants (Physalis pruinosa L.) under field conditions. The obtained results revealed that all tested materials decreased M. incognita J2 population density. Individual treatments gave average reduction percentages of M. incognita J2 as: Potassium silicate 39.4%; Furfural 55.9% and Albendazole 52.1%. The triple treatment (Potassium silicate + Furfural + Albendazole) gave the best results, as it led to decrease in the number of M. incognita J2 by 72.3% more than that occurred by the chemical nematicide (Oxamyl 24%), which gave a reduction percentage of 65.6%. The triple treatment also led to decrease in the numbers of mature females; egg masses and root gall index by 96.5, 95.4 and 83.3%, respectively, while the Oxamyl 24% gave 86.9, 90.5 and 83.3 %, respectively. In addition, the triple treatment caused improvement in the vegetative and fruiting characteristics of treated plants. Thus, triple treatments can be recommended as a safety alternative for plants and humans instead of chemical nematicides in integrated nematode control programs.

Analysis of temporal fluctuations in numbers of sexually mature Anastrepha ludens females over an extensive citrus area in northeastern Mexico

AbstractThe Mexican fruit fly, Anastrepha ludens Loew (Diptera: Tephritidae), is one of the most important pests in citrus‐growing areas in Mexico. In this study, we analyzed the temporal fluctuation of sexually mature females of A. ludens populations with respect to the availability of commercial hosts and climatic factors, as well as population data of females over an extensive citrus area in northeastern Mexico. The numbers of mature females were treated as proportions and analyzed with generalized linear mixed models with a binomial error distribution. Results revealed positive effects on proportions of mature females when commercial hosts (Valencia orange and grapefruit) were available at both medium and high levels, whereas negative effects on proportions were observed when commercial hosts were scarcely available. Monthly analyses indicated positive trends on proportion in March, April, October, and November, whereas negative trends were seen in January and June. A low capture of mature females during the late summer and the onset of winter suggests transitional phenological processes across the year. Overall, no relationships were observed between proportions with temperature and the total number of females; however, a positive relationship was observed between proportion and rainfall. These findings provide insight into the reproductive phenology of A. ludens with practical implications for fruit sampling, as well as for the autocidal or chemical control in an areawide integrated pest management (AW‐IPM) approach in citrus‐growing areas of northeastern Mexico.

The influence of metrics for spawning output on stock assessment results and evaluation of reference points: An illustration with yellowfin tuna in the eastern Pacific Ocean

Reference points are used to determine whether overfishing is occurring, a stock is overfished, or the abundance of the stock is approaching an undesirable level. Reference points are often classified as limit reference points, which indicate an undesirable state, or target reference points, which specify a desirable one. Limit reference points frequently indicate a state for which the reproductive potential of the stock is impacted, and are thus based on spawning output. Spawning output is also used in the stock-recruitment curve, which is a key component of stock-assessment models. We investigated the effect on stock assessment results of metrics of spawning output that are used either in the stock-recruitment relationship or to evaluate reference points. We use yellowfin tuna (Thunnus albacares) in the eastern Pacific Ocean as an example. The metrics biomass of mature females and fecundity attribute higher reproductive potential to the older ages, while numbers of mature females and summary biomass attribute more to the younger ages. Both the stock assessment results and the evaluation of reference points are sensitive to the metric used. The most optimistic perceptions of stock status are obtained when using numbers of mature females, female summary biomass or summary biomass to evaluate the reference points. The choice of metric may be as important as the uncertainty about steepness of the stock-recruitment curve. Given the difficulty in determining the appropriate measure of spawning output and the fact that populations fluctuate naturally, it is recommended that fishing mortality-based reference points are given more consideration for management advice aiming to maintain stocks at desirable states (target reference points) and that harvest control rules based on both types of reference points be compared for their relative effectiveness in avoiding recruitment overfishing and achieving other fisheries objectives using Management Strategy Evaluation.

The host specificity of Anomalococcus indicus Ayyar (Hemiptera: Lecanodiaspididae), a potential biological control agent for prickly acacia (Vachellia nilotica ssp. indica) in Australia

ABSTRACTPrickly acacia, Vachellia nilotica ssp. indica (Benth.) Kyal. & Boatwr, is a significant weed of northern Australia and has been a target of weed biological control in Australia since the 1980s. Following native range surveys in India, the scale insect Anomalococcus indicus Ayyar was identified as the most promising agent and was imported into Australia for further research. A. indicus is a major pest of prickly acacia on the Indian subcontinent, where it causes shoot tip dieback and plant death. Despite field observations suggesting the species was specific to V. nilotica, A. indicus completed development on 17 of the 84 non-target plant species tested during no-choice host specificity trials under quarantine conditions. Of these, Acacia falcata, V. bidwillii, V. sutherlandii and Neptunia major supported high numbers of mature females in all replicates. All of these species were utilised in choice trials. Combined risk scores indicate that V. sutherlandii, N. major and A. falcata may be attacked in the field. Due to the limited ability of scale insects to disperse, only those non-target species that occur on the Mitchell grass downs (i.e. V. sutherlandii) are considered to be at risk. Nevertheless, in view of the disparity between quarantine test results and the observed field host specificity of A. indicus in India, field trials are currently being conducted in India using Australian native species on which complete development has occurred. The future of A. indicus as a biological control agent for prickly acacia in Australia will be determined once results from these field trials are known.

Geographic Variation in the Reproductive Ecology of the Panamic Grunt in the Southeastern Gulf of California

AbstractBiological parameters pertaining to the reproductive ecology of the Panamic Grunt Pomadasys panamensis were investigated in 788 individuals sampled from the southeastern Gulf of California between November 2009 and October 2010. Length frequency distributions and mean TLs differed between sampling areas, with organisms from the coastal population exhibiting two clear modes that included most of the organisms (mostly adults; mean TL = 25.7 cm), while the open‐sea population appeared to consist of several cohorts (mean TL = 19.5 cm). Significant differences were recorded in spawning activity, gonadosomatic index (GSI), gonad weight, and size at maturity between fish from the coastal area and specimens from the open sea. The highest gonad weights and GSI values were recorded in the coastal zone during spring, coinciding with a peak in the number of mature females. In the open sea, the mature individuals were reproductively inactive throughout most of the yearlong study period, as individuals in late maturity stages represented a small portion of the sample. Female TL at 50% maturity (i.e., L50) was significantly lower in the coastal zone than in the open sea. The results suggest a differential use of available habitats by Panamic Grunts and highlight a need to consider temporal and geographic differences in reproductive ecology when formulating an adequate management program for this species.

Reproductive strategy of milk shark, Rhizoprionodon acutus (Ruppell 1837), along north-eastern Arabian Sea

The reproductive characteristic of Rhizoprionodon acutus were investigated using 684 specimens collected along Gujarat coast (India) of the north-eastern Arabian Sea. The sex ratio between male and female (1:1.13) was not found to be significantly different. Male and female sharks were found to mature at total lengths of 61.5 cm and 61.3 cm, respectively. Large and ripe follicles were observed throughout the year, which indicates that the breeding season extends all through the year. However, a significant increase in maximum follicle diameter was observed during February and March in the first quarter and during October and November in the last quarter of the year, which indicates that a portion of the population shows temporal preferences for breeding. This is also corroborated by the increase in the number of mature females with visible eggs in their ovary. Increase in the number of ready to spawn pregnant females was observed during March to May, followed by an increase in the number of postpartum females during May to June. The larger mean size of embryos was also recorded during May and, therefore, it can be presumed that a major parturition event happens during May. The uterine fecundity was found to be significantly influenced by maternal body size and varied from three to seven embryos per litter. Unlike male sharks, the female sharks showed significant variation in the monthly hepato-somatic index (HSI) which was significantly higher in January, after which it showed a gradual decreasing trend probably due to maternal nutrient investment during gestation.

A root-knot nematode small glycine and cysteine-rich secreted effector, MiSGCR1, is involved in plant parasitism.

Root-knot nematodes, Meloidogyne spp., are obligate endoparasites that maintain a biotrophic relationship with their hosts. They infect roots as microscopic vermiform second-stage juveniles, and establish specialized feeding structures called 'giant-cells', from which they withdraw water and nutrients. The nematode effector proteins secreted in planta are key elements in the molecular dialogue of parasitism. Here, we compared Illumina RNA-seq transcriptomes for M.incognita obtained at various points in the lifecycle, and identified 31 genes more strongly expressed in parasitic stages than in preparasitic juveniles. We then selected candidate effectors for functional characterization. Quantitative real-time PCR and insitu hybridizations showed that the validated differentially expressed genes are predominantly specifically expressed in oesophageal glands of the nematode. We also soaked the nematodes in siRNA to silence these genes and to determine their role in pathogenicity. The silencing of the dorsal gland specific-Minc18876 and its paralogues resulted in a significant, reproducible decrease in the number of mature females with egg masses, demonstrating a potentially important role for the small glycine- and cysteine-rich effector MiSGCR1 in early stages of plant-nematode interaction. Finally, we report that MiSGCR1 suppresses plant cell death induced by bacterial or oomycete triggers of plant defense.

On the population genetic portrait of kaluga, Acipenser dauricus georgi, 1775: Analysis of sequence variation in the mitochondrial dna control region

The variability of the mtDNA D-loop was examined in kaluga endemic to the Amur River, which is classified as critically endangered by the IUCN Red List of Threatened species. Sequencing of the D-loop fragment (819 bp) in 122 kaluga specimens collected in Lower Amur revealed 27 unique genotypes. The sample was characterized by a relatively low level of haplotypic (0.927) and nucleotide (0.0044) diversity. No considerable deviations from the neutral mutation model of DNA polymorphism were observed. Overall, the mismatch distribution patterns and the results of testing of simple demographic models (sudden demographic expansion and exponential population growth) pointed to a past increase in the number of kaluga sturgeons. According to the Bayesian skyline, the kaluga population doubled over the last two to three thousand years. The number of mature females in the modern kaluga population and the assessment of their long-term effective population size (Nef) are roughly at the same level (about three thousand individuals), which confirms the validity of assigning kaluga to the category of species on the brink of extinction.

Half-sib family effects on cultured pearl quality traits in the black-lipped pearl oyster Pinctada margaritifera: testing for indirect benefits of polyandry and polygyny

Breeding strategies and parental effects play a major role in genetic selection programmes for quality trait improvement. The black-lip pearl oyster, Pinctada margaritifera, is a protandrous hermaphrodite species in which the number of mature females is low, and these only appear after 4 years of culture. This difference underlines the importance of studying the contributions of dams and sires in the production and selection of donor pearl oyster families to choose the most appropriate breeding strategies for cultured pearl quality trait improvement. Laboratory crosses were made using wild dams and sires to produce half-sib families from polyandry and polygyny mating designs. The resulting half-sib families were used as donor oysters in a large grafting experiment of 900 grafts with random recipient oysters, using nuclei of the same size and brand, the same operating technician and the same grow-out site. After 18 months of culture, 497 cultured pearls were harvested. Comparison between half-sib pairs revealed that for nacre thickness, weight and shape, a polygyny effect exists, whereas no significant effect was observed for the polyandry mating. By contrast, no evidence of dam- or sire-related benefits was found for the presence/absence of circles, darkness level and colour categories or grade and its components: lustre and surface defects. These results should have important implications for the selective breeding of donor pearl oysters for hatchery management.

Post-transcriptional gene silencing of the gene encoding aldolase from soybean cyst nematode by transformed soybean roots

Plant parasitic nematodes cause approximately 157 billion US dollars in losses worldwide annually. The soybean cyst nematode (SCN), Heterodera glycines, is responsible for an estimated one billion dollars in losses to the US farmer each year. A promising new approach for control of plant parasitic nematode control is gene silencing. We tested this approach by silencing the SCN gene HgALD, encoding fructose-1,6-diphosphate aldolase. This enzyme is important in the conversion of glucose into energy and may be especially important in actin-based motility during parasite invasion of its host. An RNAi construct targeted to silence HgALD was transformed into soybean roots of composite plants to examine its efficacy to reduce the development of females formed by SCN. The number of mature females on roots transformed with the RNAi construct designed to silence the HgALD gene was reduced by 58%. These results indicate that silencing the aldolase gene of SCN +can greatly decrease the number of female SCN reaching maturity, and it is a promising step towards broadening resistance of plants against plant-parasitic nematodes.

Age and reproductive investment in grass goby females in the Venice lagoon

The present work describes the relationship between age and reproductive investment in the grass goby females in the Venice Lagoon. Age was estimated by otoliths reading, while reproductive investment was assessed by either the relative number of mature females across the breeding season and their gonadosomatic index. Females from different size/age classes differed in the timing and level of reproductive investment. The oldest females (3+ years old) appeared earlier in the spawning habitat, investing more at the beginning of the breeding season. In turn a later arrival in the spawning habitats has been observed for younger females (0+) and smaller individuals of 1+ and 2+ age classes. Present results gave evidence of an earlier age/size at sexual maturity of the grass goby in the Venice Lagoon compared to previous information on the species from the same lagoon and from other Mediterranean areas. Results were discussed in the light of previous data on reproductive strategy of nesting males and of the relationship between fishing pressure and life history traits in the Venice lagoon.

Sex ratio and maturity indicate the local dispersal and mortality of adult stoneflies

Summary1. Despite a recent upsurge in interest, there remains remarkably little information about the dispersal and survival of the adults of most stream‐dwelling insects, although this is a basic requirement for understanding their long‐term population dynamics.2. Using Malaise traps for a whole annual flight period, we captured adult stoneflies (Leuctra nigra) along transects perpendicular to three upland Welsh streams. We assessed spatial and temporal patterns in sex ratio to infer local dispersal and, using maturity as an age marker, estimated the mortality of adult females.3. Nearly all adult stoneflies (99%) were taken in the period 26 April–23 July, and the onset of the male and female flight periods was the same. Most males (90%) had been caught by late June. Females were classified as immature (without ripe eggs) or mature, and 90% of immature females had been caught by mid‐late June (depending on catchment). As immature females declined in the catch, mature females increased, 10% having been caught by late‐May to early June and 90% by early to mid‐July. The median catches of immature and mature females were separated by 32 days in all three catchments.4. There was a female bias in the sex ratio overall, which increased as time passed and was attributable partially to the greater longevity of females. Late in the flight period, however, female bias was also greater near the stream channel implying a return of mature females (but not males) from the riparian vegetation, presumably to oviposit.5. The number of mature females was less than the number of immatures in two of the three channels. Over all three catchments, the overall mortality of females over the 32 days taken to mature was estimated at 29%, equivalent to an exponential daily rate of 1.1% day−1. The apparently negative mortality rate in one catchment (i.e. more matures than immatures being caught) could be due to an influx of adult females from elsewhere along the channel to oviposit.6. Natural markers of age and population structure, such as sex ratio and female maturity, thus enabled us to detect a return of females to the stream to oviposit, after prior limited dispersal into the riparian zone, and to infer longitudinal movements in search of suitable sites. We were also able to estimate mortality in the field. Such natural markers seem to have been underexploited in the study of adult aquatic insects.

Effect of the rhg1 gene on penetration, development and reproduction of Heterodera glycines race 3

AbstractPenetration, development, and reproduction of Heterodera glycines (soybean cyst nematode, SCN) were compared in the roots of near-isogenic lines (NIL) differing at the rhg1 locus. Soybean seedlings were inoculated with newly hatched second-stage juveniles (J2) of an SCN race 3 inbred population. At an inoculum level of 2500 J2 per plant, similar numbers of J2 were detected in both NIL sampled daily up to 4 days after inoculation (DAI), although juvenile numbers in roots varied among experiments and over the sampling points. Samples were collected at 1, 4, 8, 12, 16 and 21 DAI to observe nematode development. All life stages of the nematode were detected in both NIL. No significant differences were observed between the NIL in the number of nematodes at juvenile stages or the adult male stage in the roots. By contrast, significant differences were detected in the number of mature females. Adult females were first seen at 12 DAI. A significantly lower number of females was consistently detected on the NIL-R line than on the NIL-S line at both 16 and 21 DAI. The number of females per plant on the NIL-R line was about 31 and 23% of those on the NIL-S line at 16 and 21 DAI, respectively. On average, the number of females at 21 DAI represented 7% of the number of J2 at 1 DAI on the NIL-R line, compared to 28% on the NIL-S line. Significantly fewer eggs were produced per female from the NIL-R line than from the NIL-S line at 21 DAI. At 28 DAI, the females on the NIL-R line were also significantly smaller than those from the NIL-S line. This study demonstrated that the presence of the rhg1 gene did not stop the nematode from penetrating. Instead, the effect of the rhg1 gene was to slowly suppress SCN growth, development and fecundity of females.

Associations between oil- and gas-well sites, processing facilities, flaring, and beef cattle reproduction and calf mortality in western Canada

From the fall of 1992 through calving 1996, detailed cow breeding outcome records were maintained actively for seven large cow–calf herds in western Canada. The numbers of mature females in the study for the breeding seasons beginning in 1992, 1993, 1994, and 1995 were 1122, 1177, 1251, and 1236, respectively. Outcomes included pregnancy status, calving interval, and the occurrence of twins, abortions, stillbirths, and neonatal mortality. Information also was collected on other risk factors known to influence beef-herd health and productivity. Detailed maps of active and inactive oil and natural-gas sites, batteries, compressor stations and processing plants were verified. Records of flaring activity at each facility were obtained from the government regulatory agency. Each flaring site then was classified as sour or sweet based on the presence or absence of hydrogen sulfide in the flared gas. A detailed inventory was prepared itemizing the type and number of facilities within 1.6 km (1 mile) of the center of each quarter section used for pasture. The total volume of gas flared within 1.6 km of the center of each pasture was determined for each month of the study. Appropriate risk periods where specified for each outcome and a cumulative exposure calculated for each breeding female (using detailed individual-animal records of cow movements between pastures and herd-management groups). Generalized estimating equations were used to evaluate the association between exposure and outcome and to adjust for potential confounders and clustering of binomial outcomes within herd. Increased risk of non-pregnancy was sometimes associated with exposure to one or more of the following facility types: sour-gas flaring battery facilities, all battery-flaring sites, active gas wells, and larger field facilities. The associations were not, however, consistent among years or even among risk periods for the same year. Facility proximity and flaring were not associated with increased abortion risk. Volume of flared sour gas from battery sites was associated with increased risk of stillbirth. Finally, sour-gas flaring was associated with increased calf-mortality risk for the 1992–1993 calf crop. Several examples of associations between exposure and increased productivity also were found (most of which involved either oil wells or all well sites).

Reproduction of anglerfish ( Lophius budegassa Spinola and Lophius piscatorius Linnaeus) from the Atlantic Iberian coast

The reproduction of black anglerfish ( Lophius budegassa Spinola) and white anglerfish ( Lophius piscatorius Linnaeus) has been studied from data collected between July 1996 and June 1997 off the Portuguese and Spanish Atlantic coasts at depths between 50 and 800 m. A total of 1301 black anglerfish (5–89 cm) and 1297 white anglerfish (11–129 cm) were sampled. The sex ratio, the spawning period and the maturity ogives by length and age were studied. The overall sex ratio was close to one for both species and the observed length related differences in sex ratio were explained by the different growth rate between sexes. The spawning period for black anglerfish was between November and February and for white anglerfish between January and June. The lengths and ages at first maturity for black anglerfish were 53.6 cm and 9–10 years for females, 38.6 cm and 7 years for males and 44.7 cm and 8 years for combined sexes. The lengths and ages at first maturity of white anglerfish were 93.9 cm and 14 years for females and 50.3 cm and 6 years for males. In this study no spawning white anglerfish females were sampled and the number of mature females was low for both species, suggesting a reproductive migration to other areas or depths.

The response of cassava cultivars to root-knot nematode infestation: An in vitro method

The aim of this study was to obtain information on the response of cassava(Manihot esculenta Crantz) to root-knot nematode infestation. To achieve this aim, a novel in vitro dual root/nematode culture method was used, where root cultures of several cassava cultivars were inoculated with axenic Meloidogyne javanica eggs. Following an incubation period,cassava roots were stained, weighed and dissected to determine the number of galls produced on the roots, as well as the number of mature females embedded in the galls. The number of eggs and larvae produced during this time were also determined. Results indicated that the modified in vitro nematode culture medium used was suitable for most root cultures of cassava cultivars. It was found that some cassava cultivars were highly susceptible to root-knot nematode infestation, with some cultivars showing very high numbers of galls and up to 50 mature females inside each gall. Some cassava cultivars screened, however, showed low numbers of galls and mature females, even though the presence of larvae was high. Some of these cultivars formed callus-like structures instead of galls, and this may be a resistance mechanism. This method may be useful as a screening tool, to determine the response and resistance or susceptibility of cassava cultivars to root-knot nematode infestation.

Group fission in Moor macaques (Macaca maurus)

This is the first report of group fission in a wild group of Moor macaques (Macaca maurus) in South Sulawesi, Indonesia. The subject group, which has been observed on the basis of individual identification since 1988, showed no sign of fission in April 1999. In August 1999, the group had split in two, with the same number of mature females in each new group. For the most part, mothers and their offspring joined the same groups. Dominance relations and association patterns established during the previous year among adult females did not strongly affect new group membership. The difference in female reproductive state between the two branch groups was a prominent characteristic. The α-male of the original group visited both groups at the first stage of group fission, even though otherwise the compositions of the new groups were stable. After the division, six adult males from outside the original group immigrated exclusively into the group that did not contain the α-male of the original group. Severe intergroup encounters occurred between the two groups. We discuss the process of the fission and the resultant pattern in relation to the egalitarian dominance style among females, lack of seasonality in reproduction, and resemblance to one-male type social organization.

Response of Root-Knot Resistant Tobacco to Concomitant Populations ofMeloidogyneSpecies

Ng'ambi, T. B. S., Rufty, R. C., and Barker, K. R. 1995. Response of root-knot resistant tobacco to concomitant populations of Meloidogyne species. Plant Dis. 79:1008-1013. Mixed populations of Meloidogyne species commonly occur in most flue-cured tobacco (Nicotiana tabacum L.) fields in the southeastern United States. The interaction of Meloidogyne arenaria race 2 (Ma) and M. incognita race 3 (Mi) on the Mi-resistant flue-cured tobacco cv. Speight G-28 and on a root-knot susceptible flue-cured tobacco cv. NC 2326 (control) was evaluated under greenhouse conditions. Plants of both cultivars were inoculated with 1,500 or 3,000 eggs of Ma or Mi alone, or with a combination of 1,500 eggs of each species. Root penetration (number of juveniles per g of root) with the mixed population assessed 10 days after inoculation (DAI) was comparable to that of Ma alone on the Mi-resistant tobacco cultivar, and of either nematode species alone on the susceptible cultivar. Also, nematode population density (number of nematodes per g of root, all stages except eggs), numbers of mature females per g of root, root damage (percent root area galled), and nematode reproduction (number of eggs per g of root) on Speight G-28 30 and/or 48 DAI with mixed population were not greater than those attributable to Ma alone. Indeed, inoculation with the mixed population resulted in slightly lower nematode population density (except at 48 DAI), root damage, and nematode reproduction on Mi-resistant cultivar than with Ma alone at the 1,500 egg inoculum level. The concomitant inoculation of Ma and Mi on NC 2326 did not differ from single inoculation with Ma for all variables measured, except reproduction at 48 DAI. These data indicate that Speight G-28 resistance to Mi was not reduced with concomitant infections of Ma and Mi. Fewer Mi than Ma mature females were recovered from the susceptible cultivar in the mixed population, indicating that Ma was more competitive than Mi.

Reproduction of Meloidogyne Javanica On Legume Crops and Some Weed Species Associated With Their Cultivation in Malawi

Seven legume crops and 18 associated weed species in maize-based, mixed crop small-holdings in Malawi were evaluated as hosts for Meloidogyne javanica in pot experiments. Plants were inoculated with the nematode by applying a water suspension of 2000 (for crops) or 3000 (for weeds) juveniles around the seedling roots. Host suitability was assessed, relative to a susceptible tomato variety, on the basis of severity of galling, number of mature females per g of root and number of eggs per egg sac. With the exception of groundnut (Arachis hypogaea), all the legume crops tested were able to support nematode reproduction to some extent. Bambara (Voandzeia subterranea) was the most susceptible host. French bean (Phaseolus vulgaris) was also susceptible, while chickpea (Cicer arietinum), cowpea (Vigna unguiculata) and soya (Glycine max) were moderately good. Pigeonpea (Cajanus cajan) was a poor host. Several of the weed species were able to support the nematode and two of these, Ageratum conyzoides and Nicandra physaloides, could be considered to be good hosts.

Estimation of the stock size of adultNephrops norvegicus(L.) from larvae surveys in the western Irish Sea in 1982

This paper describes the results of Nephrops larvae surveys in the western Irish Sea from April to June 1982. Total production of Stage I zoea obtained from the seasonal production curve is used, together with an estimate of effective fecundity, to assess the number of mature females contributing to the season's hatch. Total production of Stage I zoea was also obtained from the intercept at zero time of the stage to stage mortality regression. Length and weight data from the fishery allow an estimate of the biomass of the mature female stock to be made.