2-year Life Cycle Research Articles

Proteins journey-from marine to freshwater ecosystem: blood plasma proteomic profiles of pink salmon Oncorhynchus gorbuscha Walbaum, 1792 during spawning migration.

The pink salmon (Oncorhynchus gorbuscha) is a commercial anadromous fish species of the family Salmonidae. This species has a 2-year life cycle that distinguishes it from other salmonids. It includes the spawning migration from marine to freshwater environments, accompanied by significant physiological and biochemical adaptive changes in the body. This study reveals and describes variability in the blood plasma proteomes of female and male pink salmon collected from three biotopes-marine, estuarine and riverine-that the fish pass through in spawning migration. Identification and comparative analysis of blood plasma protein profiles were performed using proteomics and bioinformatic approaches. The blood proteomes of female and male spawners collected from different biotopes were qualitatively and quantitatively distinguished. Females differed primarily in proteins associated with reproductive system development (certain vitellogenin and choriogenin), lipid transport (fatty acid binding protein) and energy production (fructose 1,6-bisphosphatase), and males in proteins involved in blood coagulation (fibrinogen), immune response (lectins) and reproductive processes (vitellogenin). Differentially expressed sex-specific proteins were implicated in proteolysis (aminopeptidases), platelet activation (β- and γ-chain fibrinogen), cell growth and differentiation (a protein containing the TGF_BETA_2 domain) and lipid transport processes (vitellogenin and apolipoprotein). The results are of both fundamental and practical importance, adding to existing knowledge of the biochemical adaptations to spawning of pink salmon, a representative of economically important migratory fish species.

Contrasting Life Traits of Sympatric Calanus glacialis and C. finmarchicus in a Warming Arctic Revealed by a Year-Round Study in Isfjorden, Svalbard

The calanoid copepod Calanus glacialis dominates the mesozooplankton biomass in the Arctic shelf seas, but its smaller North Atlantic sibling Calanus finmarchicus is expanding northwards and may potentially replace it if the climate continues to warm. Here we studied the population structure, overwintering strategies, gonad maturation and egg production of C. glacialis and C. finmarchicus over a period of 15 consecutive months in a high-Arctic fjord with sub-Arctic ocean climate and no sea ice formation in winter. The relative proportions of C. glacialis and C. finmarchicus varied throughout the study period, but with an overall dominance of C. glacialis. The overwintering population of C. glacialis was dominated by copepodite stage CIV (74%) while C. finmarchicus overwintered mainly as CV (65%), reflecting a primarily two- and one-year life cycle, respectively. Adult males and females of C. glacialis appeared as early as October with a peak during December-January, two months earlier than in C. finmarchicus, with a corresponding one-month earlier peak in recruitment for C. glacialis. While C. glacialis reproduced prior to the bloom with egg production peaking during the bloom, C. finmarchicus started egg laying during the bloom and continued to reproduce throughout the summer. Seasonal changes in the population structure suggest that C. finmarchicus born early in spring are able to develop to CV during summer and overwinter successfully, while offspring born later in the season do most likely not reach the CV overwintering stage. The ability to reproduce early and the flexibility to alter between 1- and 2-year life cycles give C. glacialis an advantage over C. finmarchicus in high-Arctic unpredictable environments with short-pulsed primary production regimes. Our data indicate that C. glacialis and C. finmarchicus occupy similar environmental niches, but different timing in reproduction reduces the competition. If sea temperatures remain within their temperature-tolerance ranges, both C. glacialis and C. finmarchicus seem to benefit from warming due to accelerating growth and higher survival of the recruits as long as C. glacialis has access to a colder refuge by descending to deeper depths.

First observations of ovary regeneration in an amphipod, Ampelisca eschrichtii Krøyer, 1842.

BackgroundFemales of the gammaridean amphipod Ampelisca eschrichtii with signs of regenerating, previously atrophied ovaries were recovered from the northeastern shelf of Sakhalin Island (Okhotsk Sea, Russia). Ovarian regeneration was previously unknown for any amphipod species. A. eschrichtii have a predominantly 2-year life cycle (from embryo to adult death) and reproduce once between late winter or early spring at the age of 2 years. Occasionally, females survive to a third year. An adaptive value of extended survival among these females is likely to require that they are also reproductive.MethodsHistological sections from a second-year female with ovarian atrophy, a female with normal ovaries, a third-year female with ovarian regeneration, as well as testes of an immature and a sexually mature male were compared to determine the sources of cells of the germinal and somatic lines necessary for ovarian regeneration.ResultsOvarian regeneration in the third-year female began with the formation of a new germinal zone from germ cells preserved in the atrophied ovaries and eosinophilic cells of the previously starving second-year female. Eosinophilic cells form the mesodermal component of the germinal zone. A mass of these cells appeared in the second-year female that had atrophied ovaries and in large numbers on the intestine wall of the third-year female with regenerating ovaries. These eosinophilic cells appear to migrate into the regenerating ovaries.ConclusionsAll germ cells of the second-year female are not lost during ovarian atrophy and can be involved in subsequent ovarian regeneration. Eosinophilic cells involved in ovarian regeneration are of mesodermal origin. The eosinophilic cell morphologies are similar to those of quiescence cells (cells in a reversible state that do not divide but retain the ability to re-enter cell division and participate in regeneration). These histological data thus indicate that eosinophilic and germ cells of third-year females can participate in the regeneration of the ovaries to reproduce a second brood. The precursors of these third-year females (a small number the second-year females with an asynchronous [summer] breeding period and ovaries that have atrophied due to seasonal starvation) appear to possess sources of somatic and germ cells that are sufficient for ovarian regeneration and that may be adaptations to starvation stress.

Integrated modelling of insect population dynamics at two temporal scales

Population size of species with birth-pulse life-cycles varies both within and between seasons, but most population dynamics models assume that a population can be characterised adequately by a single number within a season. However, within-season dynamics can sometimes be too substantial to be ignored when modelling dynamics between seasons. Typical examples are insect populations or migratory animals. Numerous models for only between-season dynamics exist, but very few have combined dynamics at both temporal scales.In a new approach, we extend appreciably the models of Dennis et al. (2016b): we show how to adapt them for a generation time >1 year and fit an integrated population model for multiple data types, by maximising a joint likelihood for population counts of unmarked individuals and capture–recapture data from a study with marked individuals. We illustrate the approach using annual monitoring data for the endangered flightless beetle Iberodorcadion fuliginator from 18 populations in the Upper Rhine Valley for 1998–2016, with a 2-year life cycle. Standard likelihood methods are used for model fitting and comparison, and a concentrated (profile) likelihood approach provides computational efficiency.Additional information from the capture–recapture data makes the population model more robust and, importantly, enables true, rather than relative, abundance to be estimated. A dynamic stopover model provides estimates of both survival and phenology parameters within a season, and also of productivity between seasons. For I. fuliginator, we demonstrate a population decline since 1998 and how this links with productivity, which is affected by temperature. A delayed mean emergence date in recent years is also shown.A main point of interest is the focus on the two temporal scales at which perhaps most animal populations vary: in the short-term, a population is seldom truly closed within a single season, and in the long-term (between seasons) it never is. Hence our models may serve as a template for a general description of population dynamics in many species. This includes rare species with limited data sets, for which there is a general lack of population dynamic models, yet conservation actions may greatly benefit from this kind of models.

Two-Year Bee, or Not Two-Year Bee? How Voltinism Is Affected by Temperature and Season Length in a High-Elevation Solitary Bee.

Organisms must often make developmental decisions without complete information about future conditions. This uncertainty-for example, about the duration of conditions favorable for growth-can favor bet-hedging strategies. Here, we investigated the causes of life cycle variation in Osmia iridis, a bee exhibiting a possible bet-hedging strategy with co-occurring 1- and 2-year life cycles. One-year bees reach adulthood quickly but die if they fail to complete pupation before winter; 2-year bees adopt a low-risk, low-reward strategy of postponing pupation until the second summer. We reared larval bees in incubators in various experimental conditions and found that warmer-but not longer-summers and early birthdates increased the frequency of 1-year life cycles. Using in situ temperature measurements and developmental trajectories of laboratory- and field-reared bees, we estimated degree-days required to reach adulthood in a single year. Local long-term (1950-2015) climate records reveal that this heat requirement is met in only ∼7% of summers, suggesting that the observed distribution of life cycles is adaptive. Warming summers will likely decrease average generation times in these populations. Nevertheless, survival of bees attempting 1-year life cycles-particularly those developing from late-laid eggs-will be <100%; consequently, we expect the life cycle polymorphism to persist.

Pest categorisation of Chrysomyxaarctostaphyli.

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Chrysomyxa arctostaphyli, a well‐defined and distinguishable fungal species of the family Coleosporiaceae. The pathogen is regulated in Council Directive 2000/29/EC (Annex IAI) as a harmful organism whose introduction into the EU is banned. C. arctostaphyli is native to North America and is the causal agent of spruce broom rust. C. arctostaphyli is a heteroecious rust with a 2‐year life cycle alternating between the aecial host Picea spp. and the telial host Arctostaphylos spp. The main reported aecial host is P. engelmannii, but also P. abies, P. pungens, P. sitchensis, P. glauca, P. mariana and P. rubens (as well as Picea as a genus) are reported as hosts. The fungus is not known to occur in the EU but could enter via host plants for planting and cut branches. It could establish in the EU, as hosts are present and climatic conditions are favourable. The extent of overlap between the ranges of the telial and aecial hosts is greater in the EU than in North America. The pathogen would be able to spread following establishment by dissemination of spores and human movement of infected host plants. Should the pathogen be introduced in the EU, impacts can be expected in spruce woodland, plantations and on ornamental spruce trees, leading to reduced tree growth and associated ecosystem service provision. The main uncertainty concerns the level of susceptibility of P. abies and P. sitchensis under European conditions. The criteria assessed by the Panel for consideration as a potential quarantine pest are met. As the pest is not present in the EU, not all criteria for consideration as a regulated non‐quarantine pest are met.

Single-nucleotide polymorphism data describe contemporary population structure and diversity in allochronic lineages of pink salmon (Oncorhynchus gorbuscha)

Pink salmon, the most abundant Pacific salmon, have an obligate 2-year life cycle that leads to reproductively isolated even- and odd-year lineages. Using new and existing data, we examined the genetic structure of both lineages across their distributional range by genotyping 16 681 single-nucleotide polymorphisms for 383 individuals originating from seven pairs of even- and odd-year populations. Distinct differences in standing pools of genetic variation were identified between the lineages; we observed higher levels of heterozygosity, allelic richness, and significantly more private alleles in the odd-year lineage. However, the patterns of population structure were concordant between lineages: the Asian and northern Alaska populations displayed little differentiation but differed significantly from populations in southcentral Alaska and the Pacific Northwest. Our population structure results, in the context of known paleoecological information, suggest that both lineages occupied a northern Beringial refugium as well as a Cascadian refugium in North America during the Last Glacial Maximum. These results highlight the influence of historical patterns of habitat availability on contemporary population structure and support the hypothesis of a pre-glacial origin of the lineages.

Trends in Mysis diluviana abundance in the Great Lakes, 2006–2016

Abstract With the large Diporeia declines in lakes Michigan, Huron, and Ontario, there is concern that a similar decline of Mysis diluviana related to oligotrophication and increased fish predation may occur. Mysis density and biomass were assessed from 2006 to 2016 using samples collected by the Great Lakes National Program Office's biomonitoring program in April and August in all five Great Lakes. Summer densities and biomasses were generally greater than spring values and both increased with bottom depth. There were no significant time trends during these 10–11 years in lakes Ontario, Michigan, or Huron, but there was a significant increase in Lake Superior. Density and biomass were highest in lakes Ontario and Superior, somewhat lower in Lake Michigan, and substantially lower in Lake Huron. A few Mysis were collected in eastern Lake Erie, indicating a small population in the deep basin of that lake. On average, mysids contributed 12–18% (spring-summer, Michigan), 18–14% (spring-summer, Superior), 30–13% (spring-summer, Ontario), and 3% (Huron) of the total open-water crustacean biomass. Size distributions consisted of two peaks, indicating a 2-year life cycle in all four of the deep lakes. Mysis were larger in Lake Ontario than in lakes Michigan, Superior, and Huron. Comparisons with available historic data indicated that mysid densities were higher in the 1960s–1990s (5 times higher in Huron, 2 times higher in Ontario, and around 40% higher in Michigan and Superior) than in 2006–2016.

Eastern filbert blight disease resistance from Corylus americana ‘Rush’ and selection ‘Yoder #5’ maps to linkage group 7

Eastern filbert blight (EFB), caused by the pyrenomycete Anisogramma anomala, is a serious threat to the hazelnut industry in the Pacific Northwest. EFB is endemic in eastern North America where it occasionally produces small cankers on the wild American hazelnut (Corylus americana). In contrast, most cultivars of European hazelnut (Corylus avellana) are susceptible. Genetic resistance is the most promising disease control method and is an objective of the Oregon State University hazelnut breeding program. ‘Gasaway’ resistance, which is governed by a dominant allele at a single locus, has been extensively used in the program. However, ‘Gasaway’ and some of its offspring have been infected by EFB isolates from New Jersey, Minnesota, and Michigan. Efforts to create new cultivars with durable EFB resistance include identifying and studying new resistance sources. In this study, resistant accessions C. americana ‘Rush’ and interspecific hybrid selection ‘Yoder #5’ were crossed with susceptible C. avellana selections and the resulting segregating seedling populations were inoculated by either exposure of potted trees under a structure topped with diseased branches or field exposure supplemented by tying diseased branches to each tree. Disease response was scored when cankers were visible 20 months after inoculation. Resistance from both sources segregated in a 1:1 ratio, indicating control by a single locus and a dominant allele for resistance. DNA extracted from the seedlings was amplified with previously mapped microsatellite markers. Resistance from both C. americana ‘Rush’ and ‘Yoder #5’ was placed on linkage group 7 in the same position as resistance from C. avellana ‘Ratoli.’ Linked microsatellite markers B753, GB372, and B509 will be useful for marker-assisted selection and the pyramiding of genes for durable EFB resistance. Assessing response to EFB is challenging, whether the plants are inoculated under a structure topped with diseased wood or in a humidity chamber in the greenhouse, or by exposure in the field. The pathogen has a 2-year life cycle, and there is a 15-month wait between inoculation and symptom expression. A small number of escapes is commonly encountered, and resistant plants occasionally develop small cankers. Our approach of studying segregation ratios and then mapping with microsatellite markers should be a useful approach for disease resistance studies in many tree crops.

Stock structure of the English Channel common cuttlefish Sepia officinalis (Linnaeus, 1758) during the reproduction period

Within the English Channel, the common cuttlefish Sepia officinalis is a semelparous species for which a 2-year life cycle was exclusively described in the 1980s. In the 1990s, new research indicated that whilst a 2-year life cycle was still evident for females and the large majority of males, a small proportion of males were actually maturing at only 1 year of age. Since 1980, the interest of French and UK fishers for this resource has increased and it is nowadays one of the most important demersal species of the area and is considered to be fully exploited. From the start of the 20th century, fishing effort and sea surface temperatures have increased in the English Channel and have probably impacted the life history traits of S. officinalis. A 2-year sampling programme was undertaken at French landing sites of the English Channel during the reproduction season in 2010 and 2011 to estimate if the proportion of 1-year-old mature animals has changed. Age determination was carried out by coupling polymodal decomposition and lipofuscin measurement. Size-at-maturity for each year and each sex was estimated by fitting a binomial error GLM. Results highlight that a variable percentage of males and females belonging to the first cohort are mature and that size-at-maturity was lower than that observed in the 1990s. Finally, different parameters, such as temperature and fishing pressure are explored to discuss changes in life history traits suggesting that cuttlefish could be an indicator of the temperature regime shift in the English Channel.

Ambient temperature influences adult size and life span in jumbo squid (Dosidicus gigas)

The eastern Pacific jumbo squid (Dosidicus gigas) is one of the largest and most abundant squid of the world ocean. To reveal possible interannual variability in the life span, statoliths were used to determine the age of mature females belonging to two modal size groups (&lt;490 and &gt;500 mm mantle length) collected before (1991–1996), during (1997–1998), and after (1999–2011) a strong El Niño event in Peruvian waters. We found that water temperatures encountered between the third and sixth months of ontogenesis had the strongest negative effect on age. Together with a weaker but significant negative effect of temperatures encountered during early life (first to third months) and later ontogenesis (seventh and eighth months), these temperature parameters (along with other environmental factors) were important in determining whether a given animal had a 1-year life cycle (early maturation and small size) or a 1.5- to 2-year life cycle (delayed maturation and large size). The possible cause of a sudden increase in abundance of large D. gigas in 2000–2001 is discussed.

Possible altitude and temperature limits on pine wilt disease: the reproduction of vector sawyer beetles (Monochamus alternatus), survival of causal nematode (Bursaphelenchus xylophilus), and occurrence of damage caused by the disease

Pine wilt disease is caused by the pine wood nematode [Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle]. In East Asia, an important vector of the nematode is Monochamusalternatus Hope. We determined the tolerance and reproductive ability of sawyer beetles and the nematode to altitude and temperature at elevations between 850 and 1,450 m on Mt. Fuji in Japan. The number of emergent adults decreased markedly along the altitudinal gradient, but the beetle could still reproduce at 1,050 m (8.2 °C annual mean temperature). Beetles with a 2-year life cycle increased rapidly in number with increasing altitude. The pine wood nematode survived through winter at all altitudes tested (850–1,450 m). The beetle population decreased between 950 (9.1 °C) and 1,150 m (8.3 °C). Therefore, the beetle population seems to be stable at 850 m (10.2 °C) and lower altitudes (higher temperatures) but cannot be maintained from 950 (9.1 °C) to 1,150 m (8.3 °C) without constant immigration of beetles from lower altitudes. The beetles could not reproduce at altitudes above 1,150 m (lower than 8.2 °C). From the mean and effective cumulative temperatures, we concluded that the beetle (and its population) can endure temperatures lower than those previously reported. Pine wilt disease also occurred at lower temperatures and higher altitudes than expected. We have summarized the principal strategies for controlling the disease at high altitudes based on these results.

Cohort-splitting in the millipede Polydesmus angustus (Diplopoda: Polydesmidae): No evidence for maternal effects on life-cycle duration

Under seasonal conditions, Polydesmus angustus individuals born in the first part of the breeding season have a 1-year life cycle and those born later have a 2-year life cycle (cohort-splitting). In this study, 249 juveniles from four early broods (born in mid- July) and four late broods (born in September) were reared under similar laboratory conditions, to test for possible maternal influ- ences on life-cycle duration. Development times of early- and late-born individuals were compared under four combinations of day length and temperature (16 h - 18°C, 16 h - 16°C, 12 h - 18°C and 12 h - 16°C). The results showed that development time varied significantly in response to day length, temperature and sex, but that of individuals in the early and late broods did not differ signifi- cantly (mean development times ± SE: 180 ± 6 and 183 ± 8 days, respectively). There were no significant interactions between birth period and other factors, indicating that the effects of day length, temperature and sex on development time were similar in early- and late-born individuals. This indicates that the extended life cycle of millipedes born late in the season is not maternally deter- mined and that cohort-splitting is controlled entirely by the environmental conditions experienced by the offspring during their development. This conclusion is supported by the absence of significant variation in offspring live weight at birth measured at dif- ferent times in the breeding season. The results are discussed in relation to the bet-hedging theory, which is often put forward to account for cohort-splitting in arthropods. In P. angustus, the results are consistent with either bet-hedging or adaptive plasticity, but further studies are required to decide which interpretation is correct.

Cycles, stochasticity and density dependence in pink salmon population dynamics

Complex dynamics of animal populations often involve deterministic and stochastic components. A fascinating example is the variation in magnitude of 2-year cycles in abundances of pink salmon (Oncorhynchus gorbuscha) stocks along the North Pacific rim. Pink salmon have a 2-year anadromous and semelparous life cycle, resulting in odd- and even-year lineages that occupy the same habitats but are reproductively isolated in time. One lineage is often much more abundant than the other in a given river, and there are phase switches in dominance between odd- and even-year lines. In some regions, the weak line is absent and in others both lines are abundant. Our analysis of 33 stocks indicates that these patterns probably result from stochastic perturbations of damped oscillations owing to density-dependent mortality caused by interactions between lineages. Possible mechanisms are cannibalism, disease transmission, food depletion and habitat degradation by which one lineage affects the other, although no mechanism has been well-studied. Our results provide comprehensive empirical estimates of lagged density-dependent mortality in salmon populations and suggest that a combination of stochasticity and density dependence drives cyclical dynamics of pink salmon stocks.

A REGIONAL NETWORK OF DIALOGUE AND EXCHANGE PLATFORMS TO IMPROVE THE IDENTIFICATION OF FARMER'S NEEDS AND THE DISSEMINATION OF NEW CULTIVARS OF BANANA AND PLANTAIN (MUSA SPP.)

To improve the identification of farmer needs and the dissemination of new cultivars of banana and plantain (Musa spp.) in West and Central Africa, the Africa Research Center on Bananas and Plantains (CARBAP) and its partners used a mother/baby approach for participatory cultivar evaluation through a regional network of platforms for dialogue and exchange between all the stakeholders of the value chain. Eight platforms have been established in Cameroon, Benin, Gabon and Guinea. Each platform includes: (a) a common reference plot with ten cultivars; (b) a network of 20 farmers testing three cultivars in their own fields chosen from the reference cultivars; (c) a steering committee to manage the platform; and (d) a local users and experts club. Plantain cultivars and hybrid, cooking and dessert banana were chosen according to the production constraints and consumer demand. The platforms are designed and managed in partnership using participatory approaches. At key steps of the cycle duration (vegetative, flowering stage) and at harvest, stakeholders are convened by the steering committee for joint evaluation. Lessons learned on varietal innovation and participation collected from diverse stakeholders (extension services, non-governmental organizations, producer organization, nursery organization, processors, traders and scientists) are discussed. During the 2-year life cycle of the project, 215 people shared their views on 30 cultivars of banana and plantain. Their capacity was built on how to grow and use banana and plantain successfully. At the end of the project, each platform continued to carry on their activities, making the impact of the Innovation on Banana and Plantain (INNOBAP) project more sustainable.

Long-term changes in the littoral benthos of a Norwegian subalpine lake following the introduction of the European minnow (Phoxinus phoxinus)

The littoral benthos of the subalpine lake, Øvre Heimdalsvatn, has been documented in a series of investigations carried out in 1972, 1976, 1985 and 2000. During this 28-year period there have been major changes in the benthos of the lake following the introduction of European minnow (Phoxinus phoxinus) into the lake where brown trout (Salmo trutta) was formerly the sole species. In 1972 Ephemeroptera, Trichoptera, Plecoptera and Gammarus lacustris dominated the macrobenthos, constituting 85% of faunal numbers, while Chironomidae and Oligochaeta made up only c. 6%. However, by 1976, chironomids and oligochaetes had increased in relative abundance, while G. lacustris declined. This trend towards a dominance of chironomids and oligochaetes was confirmed in 1985 and 2000, although absolute numbers of Ephemeroptera, Plecoptera and Trichoptera increased in 2000 relative to 1972 values. Gammarus lacustris had a 2-year life cycle in Øvre Heimdalsvatn. In 1972 there were significantly more females than males, but by 1976 and through to 2000 there were greater numbers of males. Despite this reduction in females, numbers of juveniles increased, although mortality, probably due to increased predation from minnows, was higher than earlier. The introduction of the alien species, the European minnow, into Øvre Heimdalsvatn has clearly changed the composition and structure of the littoral macroinvertebrate benthos.

MASS SEXUAL REPRODUCTION IN THE TOXIGENIC DIATOMS PSEUDO-NITZSCHIA AUSTRALIS AND P. PUNGENS (BACILLARIOPHYCEAE) ON THE WASHINGTON COAST, USA1

Sexual reproduction is documented for the first time in field populations of the pennate diatoms Pseudo-nitzschia australis Freng. and P. pungens (Grunow ex Cleve) Hasle (var. cingulata Villac and hybrids between var. cingulata and var. pungens). A bloom dominated by these species began on June 26, 2006, along Kalaloch Beach, Washington, USA, coincident with a drop in the Si(OH)4:NO3 ratio to below two. Multimodal size distributions were detected for both species, and synchronous auxosporulation occurred within the smallest size class during a 3-week window. Auxospores and initial cells created a new class of large cells, and cells in the intermediate size classes increased in abundance during auxosporulation. Mating cells of both species were attached to colonies of surf-zone diatoms. Paired gametangia, gametes, zygotes, auxospores, and large initial cells were found. Auxosporulation began first for P. pungens (June 30), apparently once a critical, high cell concentration was reached, followed by P. australis (July 5), when the total Pseudo-nitzschia cell concentration reached 929,000 cells · L−1. Low frequencies of auxosporulation occurred throughout the bloom but increased 4-fold for P. australis and 3-fold for P. pungens when macronutrients were reduced to low levels on July 11. A 2-year life cycle was estimated for P. australis and 3 years for P. pungens, both with annual auxosporulation. Domoic acid (DA) in razor clams reached a maximum of 38 μg DA · g−1 on July 18. A significant relationship existed between the percent of cells within the new size range and DA concentrations in razor clams on the same beach.

History, Distribution, Damage, and Life Cycle of a Pine Shoot Gall Sawfly, Xyela gallicaulis (Hymenoptera: Xyelidae)

Larvae of Xyela gallicaulis Smith cause shoot stem galls in young pines. Loblolly pine, Pinus taeda L., is the most seriously damaged, but galls have been observed on slash pine, P. elliottii var. elliottii Engelm., and shortleaf pine, P. echinata Mill. Studies in Virginia and Georgia confirm a 2-year life cycle. Larval development takes 4 - 6 wks. After feeding, larvae bore out of the galls and drop to the ground where they form a papery cocoon in the soil to pupate, and where they remain for 22 - 25 months. Adults emerge from cells constructed in the soil from early-December to mid-January of the second year. Eggs are inserted into the vegetative buds during odd-numbered years. Insect associates found feeding in or on gall tissues are the Nantucket pine tip moth, Rhyacionia frustrana (Comstock) (Tortricidae), and the weevil Conotrachelus carolinensis Schoof (Curculionidae).

Formal statistical analysis of the data in disparate impact cases provides sounder inferences than the U. S. government's 'four-fifths' rule: an examination of the statistical evidence in Ricci v. DeStefano

Many countries have fair employment laws to protect racial, gender, religious or ethnic minorities from discrimination and courts in the USA can order remedies such as one out of every three new hires should be a member of a protected group after finding an employer discriminated. What steps can an employer undertake to ensure its employment practices do not disadvantage minorities when it does not need to comply with a court order? This issue arose in Ricci v. DeStefano, a ‘reverse discrimination’ case under review by the U.S. Supreme Court. Seventeen Whites and 1 Hispanic who achieved sufficiently high scores qualifying them for promotion to lieutenant or captain of the New Haven Fire Department sued the city because it cancelled the examinations after seeing that no African American could be appointed to an existing vacancy. The City of New Haven justified its action on the basis that both examinations had a disparate impact on African Americans and Hispanics because the ratios of their pass rates to that of Whites were less than 80%, contrary to a ‘rule of thumb’ in the government’s Uniform Guidelines. The city did not conduct statistical tests, which are referred to in the guidelines. The lower courts accepted New Haven’s explanation and granted summary judgement to it. A statistical study of the various criteria considered by the city and lower courts in their review of the data demonstrates that nearly 70% of the time a fair non-discriminatory test for either position will fail the government’s ‘80% rule’ and at least 60% of the time both fair tests would fail this ‘four-fifths rule’. Since the city created a new criterion after seeing the results, it is difficult to formulate precisely the other ‘rare’ or ‘unusual’ outcomes that would lead to cancellation of the examination. Would New Haven reject a list with no Hispanics or no Whites eligible for an immediate promotion? Would it require that all three groups be represented in the pool eligible for advancement to each position? From the viewpoint of statistical theory, the hypothesis being tested and the definition of pass or selection rates that will be compared should be decided before examining the data. Formal statistical tests on several relevant pass rates show that the lieutenant examination had a disparate impact on minority applicants, but the differences in the pass rates on the captain examination were not close to statistical significance. Furthermore, when the city cancelled both examinations, it only focused on the demographic mix of the high scorers who could receive an immediate promotion and ignored the 2-year life cycle of the list. Neither likely retirements nor job turnover during the 2-year life cycle

Female reproductive patterns in the millipede Polydesmus angustus (Diplopoda: Polydesmidae) and their significance for cohort-splitting

First-stadium juveniles of Polydesmus angustus born each month from May to September were reared throughout their life cycle under controlled seasonal conditions. At maturity, the reproductive patterns of 62 females were studied individually. It was confirmed that females born from May to August have a 1-year life cycle and those born from late August onwards a 2-year life cycle (cohort-splitting). A third type of life cycle - interseasonal iteroparity - was observed in a few females born late in the season. On average, annual females started to reproduce when 11.4 months old and produced 3.6 broods per female over 1.8 months; the later they were born from May to August, the later they reproduced the following year. Biennial females started to reproduce when 19.9 months old and produced 3.8 broods per female over 2.2 months; all reproduced early in the breeding season. These results indicate that only annual females can produce an appreciable proportion of biennial offspring from late August onwards, which rules out direct genetic determination of life-cycle duration. The reproductive characteristics of P. angustus suggest a non-genetic mechanism that can drive cohort-splitting. Because individual females reproduce for about 2 months on average, this automatically results in cyclic variation in life-cycle duration (annual/biennial/annual) in the long-term progeny of any female.