Seasonal Variation In Morphology Research Articles

Diurnal and Seasonal Variation in Morphology and Elemental Composition of Particulate Matters

Diurnal and Seasonal Variation in Morphology and Elemental Composition of Particulate Matters

Diverge and Conquer: Phylogenomics of southern Wallacean forest skinks (Genus: Sphenomorphus) and their colonization of the Lesser Sunda Archipelago.

The archipelagos of Wallacea extend between the Sunda and Sahul Shelves, serving as a semipermeable two-way filter influencing faunal exchange between Asia and Australo-Papua. Forest skinks (Genus Sphenomorphus) are widespread throughout southern Wallacea and exhibit complex clinal, ontogenetic, sexual, and seasonal morphological variation, rendering species delimitation difficult. We screened a mitochondrial marker for 245 Sphenomorphus specimens from this area to inform the selection of 104 samples from which we used targeted sequence capture to generate a dataset of 1154 nuclear genes (∼1.8 Mb) plus complete mitochondrial genomes. Phylogenomic analyses recovered many deeply divergent lineages, three pairs of which are now sympatric, that began to diversify in the late Miocene shortly after the oldest islands are thought to have become emergent. We infer a complex and nonstepping-stone pattern of island colonization, with the group having originated in the Sunda Arc islands before using Sumba as a springboard for colonization of the Banda Arcs. Estimates of population structure and gene flow across the region suggest total isolation except between two Pleistocene Aggregate Island Complexes that become episodically land-bridged during glacial maxima. These historical processes have resulted in at least 11 Sphenomorphus species in the region, nine of which require formal description. This fine-scale geographic partitioning of undescribed species highlights the importance of utilizing comprehensive genomic studies for defining biodiversity hotspots to be considered for conservation protection.

Migratory Helicoverpa armigera (Lepidoptera: Noctuidae) Exhibits Marked Seasonal Variation in Morphology and Fitness.

Many insects adopt seasonal, trans-latitudinal migration in response to altering climatic conditions, resource availability or reproductive requirements. Though the migration behavior of the cotton bollworm, Helicoverpa armigera (Hübner)(Lepidoptera: Noctuidae), has been well-studied, little is known about the extent of intra-specific variation between northward- and southward-migrating individuals. In this study, we captured H. armigera adults along the species' migration route during 2017-2018 to determine seasonal variability in their morphology, flight capability, and reproductive performance. Northward migrants have broader, longer bodies and are 1.33 times heavier than southward migrants, hinting at a comparatively higher allocation of resources in the abdomen. Accordingly, the former migrants engaged in longer flights, had greater reproductive capacity and a longer lifespan than southward ones. As northward migrants originate from favorable environmental conditions, their fitness is higher than that of the southward cohorts that develop on less favorable host plants and in perhaps more adverse climatic or ecological conditions. Northward H. armigera migrants thus possess an advantageous morphology that benefits habitat colonization and resource exploitation. Our work offers a novel perspective on the ecological and reproductive benefits of long-distance migration and can aid the development of population monitoring and forecasting methods for this globally important agricultural pest.

Adaptive Plasticity in Insect Parasites – Philopterus Lice and their Accentor Passerine Hosts

One hundred and five alpine accentors Prunella collaris (Scopoli, 1786) and ninety four dunnocks Prunella modularis (Linnaeus, 1758) were captured in the West Carpathian Mountains of Slovakia in order to compare the morphology of their Ischnoceran parasites Philopterus emiliae Balat 1985 and Philopterus modularis (Denny, 1842), respectively. In the case of both host species, the largest bodied lice occurred in winter, before the beginning of the host breeding season. Lice collected during the host breeding season were smaller in size than those collected in winter. Lice collected in the autumn, following postnuptial molt were even smaller in size. The largest lice were found on the bodies of host individuals with relatively long wings. The lice Ph. emiliae also differed in shape. In winter, the relative size of the head was large, while in the autumn, the head was proportionately smaller in size, compared to other body regions. Adult lice Ph. modularis also tended to have larger heads in April than in July. Measurements of lice over an eleven year period from the same site yielded differences in shape, but not in size. This study is one of the first assessments of seasonal variation in morphology of lice.

남해 서부연안의 사구미 만에서 거머리말(Zostera marina)과 애기거머리말(Z. japonica)의 개체생태학

The autecology of the Zostera marina and Z. japonica was studied in populations growing in the same locality (Sagumi Bay, southwestern coast of Korea). Environmental factors and plant characteristics were examined monthly from August 2008 to September 2011. Along intertidal zone, Z. japonica (0.1-0.5 m above mean lower low water, MLLW) occurred above Z. marina (0.5-2.5 m MLLW). Tidal exposure at low tide during day was the highest in the spring and the lowest in the summer. Underwater Irradiance showed seasonal fluctuation that was the highest in spring and summer caused by tidal pattern. Strong seasonal patterns in water temperature appeared to control the seasonal variations in morphology, biomass and leaf growth. The seasonal pattern of Z. japonica resembled that of the Z. marina in morphological characteristics, above-and below-ground biomass, whereas it differed in shoot density and leaf elongation. Despite some similarities in seasonal growth patterns, the patterns of Z. japonica were lagged by 2 month of Z. marina. Seasonal variation in the above biomass of Z. marina was caused by changes in density and plant size, whereas that of Z. japonica was mainly caused by changes in shoot density. Zostera marina was more sensitive to high temperatures than Z. japonica, and the increasing water temperature during the summer became the factor that inhibits the growth of the Z. marina. Zostera Japonica, there is no clear change according to the amount of the light. It is because its habitat locates above that of Zostera marina so that the amount of the light that is necessary to growth is enough and in this condition, any preventing factor does not seem to work at all. Although underwater light getting into Zostera marina's habitat is very low level and there is no any hindrance to the survival of them, it prevents them from their productivity a bit.

Distribution, seasonality and putative origin of the non-native red alga Bangia atropurpurea (Bangiales, Rhodophyta) in the Laurentian Great Lakes

Bangia atropurpurea was first observed in Lake Erie in 1964 and subsequently spread to the lower Laurentian Great Lakes by the mid to late 1970s. The present study was initiated to examine the recent distribution of B. atropurpurea in the Great Lakes, the seasonal variation of the alga and the putative origin of this species based on DNA sequence analysis. From surveys in 1995 and 2002, this species has clearly spread, with newly identified populations observed in Lakes Huron, Michigan, Georgian Bay and the St. Lawrence River. Morphological analyses showed that Great Lakes populations from individual lakes or neighboring populations did not group together in cluster analyses. Correlation analysis, however, revealed significant relationships between the presence or absence of Bangia among the studied sites with pH and specific conductance as those locations that had stable populations had a mean pH and conductance of 8.2 and 353μS·cm−1 respectively. Seasonal variation in morphology of a population from Burlington, Ontario (Lake Ontario, Canada) was examined monthly for one year. Maximum filament length occurred in April, with the greatest diameter and archaeospore production observed in May. Significant correlations were also noted for many morphological characteristics with water temperature, population height on the shoreline relative to the waterline and total phosphorus. Collections of B. atropurpurea analyzed from the Great Lakes were observed to be identical in sequence to collections of European freshwater Bangia in the cox2–3 gene spacer, the nuclear internal transcribed spacers (ITS 1 and 2) and the 5.8S rRNA gene (between the small and large subunits of the rRNA gene). These results suggest a recent European origin; however, further global collections of B. atropurpurea and microsatellite analyses are necessary to confirm this hypothesis.

Seasonal variation in the egg morphology of the copepod Eurytemora americana and its relationship with reproductive strategy in a temperate estuary in Argentina

Abstract Berasategui, A. A., Hoffmeyer, M. S., Dutto, M. S., and Biancalana, F. 2012. Seasonal variation in the egg morphology of the copepod Eurytemora americana and its relationship with reproductive strategy in a temperate estuary in Argentina. – ICES Journal of Marine Science, 69: 380–388. Seasonal variation in the morphology of Eurytemora americana eggs and its relationship with reproductive strategy were studied in the Bahía Blanca Estuary. Eggs from field females were analysed morphologically by optical (OM) and electron microscopy [scanning electron microscopy (SEM)–transmission electron microscopy (TEM)] during the population pulse. Additionally, egg-carrying females were incubated simulating in situ environmental conditions to evaluate the resting egg character. Subitaneous and resting eggs were indistinguishable by OM, but showed different chorion appearance under SEM and TEM. Sinuous patterned chorion eggs, mainly produced during the period of population growth, were classed as subitaneous eggs based on their high level of hatching success. Eggs with a sponge-like appearance, produced after the population peaked, were classed as diapause eggs based on their inability to hatch even under favourable conditions. There were significant differences in egg size through the population pulse and diapause eggs were significantly bigger than subitaneous eggs. The observation of both morphotypes in egg-carrying females after peak population abundance confirms the existence of a transitional reproductive stage before the exclusive production of diapause eggs at the end of the pulse. Diapause egg production enables E. americana to resist adverse conditions, ensuring its survival in temperate estuaries.

Description, seasonal morphological variation, and molecular identification of Paraxanthus barbiger megalopae obtained from the natural environment

Larval identification represents a powerful tool for detailed studies on recruitment and population dynamics in marine invertebrates. However, intra-specific morphological variation can become a serious limitation for the correct identification at species level. High morphological variation can be expected in species with continuous breeding periods because larvae are exposed to seasonal fluctuations in physical and biological factors during their development in the plankton. We describe, for the first time, the megalopae of Paraxanthus barbiger, one of the most common and abundant brachyuran crabs along the coast of Chile. To validate larvae identification, the 16S rRNA gene was sequenced from both megalopae and adults, and was compared with sequences of three sympatric species. In addition, size, body shape, and appendage setation pattern variations were analyzed with a year-round sampling scheme. The results demonstrated high seasonal phenotypic plasticity in size. Despite these differences, certain conservative characteristics exist which can be very useful for identification at species level.

Stochastic Modelling of the Impact of Flood Protection Measures Along the River Waal in the Netherlands

River flooding is a problem of international interest. In the past few years many countries suffered from severe floods. A large part of the Netherlands is below sea level and river levels. The Dutch flood defences along the river Rhine are designed for water levels with a probability of exceedance of 1/1250 per year. These water levels are computed with a hydrodynamic model using a deterministic bed level and a deterministic design discharge. Traditionally, the safety against flooding in the Netherlands is obtained by building and reinforcing dikes. Recently, a new policy was proposed to cope with increasing design discharges in the Rhine and Meuse rivers. This policy is known as the Room for the River (RfR) policy, in which a reduction of flood levels is achieved by measures creating space for the river, such as dike replacement, side channels and floodplain lowering. As compared with dike reinforcement, these measures may have a stronger impact on flow and sediment transport fields, probably leading to stronger morphological effects. As a result of the latter the flood conveyance capacity may decrease over time. An a priori judgement of safety against flooding on the basis of an increased conveyance capacity of the river can be quite misleading. Therefore, the determination of design water levels using a fixed-bed hydrodynamic model may not be justified and the use of a mobile-bed approach may be more appropriate. This problem is addressed in this paper, using a case study of the river Waal (one of the Rhine branches in the Netherlands). The morphological response of the river Waal to a flood protection measure (floodplain lowering in combination with summer levee removal) is analysed. The effect of this measure is subject to various sources of uncertainty. Monte Carlo simulations are applied to calculate the impact of uncertainties in the river discharge on the bed levels. The impact of the “uncertain” morphological response on design flood level predictions is analysed for three phenomena, viz. the impact of the spatial morphological variation over years, the impact of the seasonal morphological variation and the impact of the morphological variability around bifurcation points. The impact of seasonal morphological variations turns out to be negligible, but the other two phenomena appear to have each an appreciable impact (order of magnitude 0.05–0.1 m) on the computed design water levels. We have to note however, that other sources of uncertainty (e.g. uncertainty in hydraulic roughness predictor), which may be of influence, are not taken into consideration. In fact, the present investigation is limited to the sensitivity of the design water levels to uncertainties in the predicted bed level.

Seasonal variation in morphology, growth and reproduction of Zostera caespitosa on the southern coast of Korea

Seasonal dynamics of Zostera caespitosa Miki were monthly monitored in Jangmok Bay of Geoje Island, Korea by examining morphometrics, reproductive phenology, leaf productivity and environmental factors from July 2001 to July 2002. Shoot size and weight reached to maximum values during summer, but the number of leaves per shoot did not exhibit a clear seasonal pattern. The leaf area was approximately 2-fold greater in summer in during winter, which was mainly due to the increase in shoot length. Flowering shoot appeared in early March, and developed into fruits in early May. By the end of May, all reproductive shoots bore mature fruits. Leaf growth exhibited a seasonal pattern, ranging from 1.5 mg DW shoot −1 d −1 in November to 16.3 mg DW shoot −1 d −1 in June. The leaf plastochrone intervals varied from 12.5 days in May to 37.5 days in November. The mean lifetime of leaves was 99.1 days and the annual leaf turnover was estimated to be 3.7 times per year. This study indicated that the growth and flowering phenology of Z. caespitosa was strongly coupled to seasonal light conditions.

Clutch size variation and morphology in a cyclomorphic Bosmina population

Clutch size, cyclomorphosis and allometric growth were analysed in a population of the humpbacked Bosmina (E.) coregoni gibbera. This species shows cyclomorphosis in antennule length and body height, traits that may reduce predation risk from Leptodora kindtii. Individuals with long antennule and extreme body height may pay a cost in terms of decreased reproductive capacity. On the other hand, increasing the body height may be a way to increase the brood chamber volume during periods of good food conditions. We tested these hypotheses by comparing the seasonal variation in clutch size with the seasonal variation in morphology. Antennule length and body height increased from mid-May to August and showed usually positive allometry at times with high population densities of the predatory cladoceran Leptodora kindtii. Clutch size decreased from spring to late summer contrary to the hypothesis that cyclomorphosis in height is caused by a seasonal variation in reproductive demand. However, within-dates antennule length was negatively related and body height was positively related to clutch size. We conclude that the long antennule may impose a cost that reduces the reproductive capacity. The hypothesis that carapace cyclomorphosis is driven by seasonally varying clutch sizes was rejected.

Seasonal Variation in Morphology of Continuously Stocked White Clover

Efforts to improve persistence of white clover (Trifolium repens L.) in the southeast USA would benefit from knowledge of annual growth patterns and associated periods of environmental stress. Our objective was to determine seasonal changes in morphological traits that contribute to plant growth and persistence among adapted cultivars and germplasm. ‘Louisiana S‐l’, ‘Osceola’, Brown Loam Synthetic No. 2 germplasm, and Southern Regional Virus Resistant germplasm were sown in common bermudagrass [Cynodon dactylon (L.) Pers.] pastures in September 1993 at Mississippi State and Newton, MS, and continuously stocked with cattle to maintain a 5‐ to 10‐cm sward height. Stolon length, viability of axillary buds, and seedling numbers were measured monthly for the next 2 to 3 yr. Stolon length of all entries increased to a maximum by June before declining to a minimum in October. Peak stolon production in the first, second, and third year after seeding at Mississippi State was 42, 123, and 59 m m−2, respectively. There were no monthly differences among the four entries for proportion of stolon nodes having elongated, viable, or nonviable axillary buds at either location. The proportion of nodes with elongated buds increased from 10 to 20% in October to 45% in March before declining during the spring. An increase in elongated buds during early summer preceded the fall decline. Number of volunteer seedlings ranged from 10 to 1870 m−2 during the year, but any positive influence on stand persistence was not apparent. The cyclical trends for axillary bud viability indicate continued potential for vegetative persistence, particularly in the winter and spring, but the longterm decline in stolon length of all entries suggests that selection for different characters was not associated with improved persistence.

Seasonal variations in size and morphology of Acanthocyclops robustus (Copepoda Cyclopoida)

The variations in the body length, swimming legs and some setae of the freshwater cyclopid Acanthocyclops robustus were analysed during an annual cycle in the field, and in laboratory experiments at different culture temperatures. In Lake Créteil. a shallow temperate sand-pit lake, there is a seasonal morphological variation of the setae: the plumose forms were restricted to the warmer season and the spinose ones to colder periods. Contrary to other years, the specific ‘spine formula’ of the swimming legs (3-4-4-4) did not vary during the reference year. In laboratory experiments, both sex and post-embryonic developmental temperatures had an effect on the length of adults. A significant parental effect on body length was detected. Pairs with anomalous spine formulae produced offspring either with anomalous spine formulae or typical 3-4-4-4 formulae. No significant effects of parental culture temperatures, offspring culture temperatures and sex on the total number of spines were found. Modification of plumose into spinose setae did not occur, whatever the offspring developmental temperatures. The results presented here suggest that the alterations of the appendages of the cyclopid A.robustus could be compared to the cyclomorphosis in other zooplanktonic groups, and contribute to our understanding of the role of phenotypic induction in aquatic biology.

Ciclomorfose em Bosmina (Crustacea, Cladocera) no Lago Paranoá, Brasília

In order to verify the existence of seasonal variations in morphology of Bosmina longirostris and Bosmina hagmanni, samples were taken from Paranoa Lake (Brasilia, DF) during 1983. Body length and breadth, antennule, mucro and eye diameter were measured. Alometry rates were also calculated. It was verified that throughout the year both Bosmina species presented variation involving the five measures. The measures, except the antennule and mucro of B. longirostris, depend, at least partially, on the size of the individual and, therefore, on the age structure of the population. The antennule and mucro variations of B. hagmanni were strongly related to alometry rates. For B. longirostris the antennule and mucro variations appeared to be related to phenomena in an embryonic phase.

The taxonomy ofPilayella littoralis(L.) Kjellm. (Phaeophyta, Ectocarpales) in the British Isles, a numerical approach

The taxonomy of Pilayella littoralis (L.) Kjellm. is confused due to the extreme variability of the species. A numerical taxonomic study has been carried out using computer clustering techniques on 71 morphological and ecological characters with 163 plants from a wide range of habitats in Britain, and the status of the clusters formed scrutinized with reference to the original data. On this basis certain clusters were grouped together as seasonal variants of similar entities. Estuarine plants tend to have in common a number of characteristics which separate them from those collected in marine habitats, such as a much higher incidence of opposite branching and considerably finer filaments. A number of other environmental gradients other than salinity can be associated with these characteristics, for example substrate, exposure etc. The fact that seasonal morphological variation is also common, especially in marine populations, underlines the complexity of the relationship between environment and form in the species, and it is concluded that the establishment of a practicable natural classification of intraspecific variation in P. littoralis is impossible.

Changes in the fine structure of tanycytes during the annual reproductive cycle of the male little brown bat Myotis lucifugus lucifugus

The hypothalamic arcuate nucleus in the male little brown bat Myotis lucifugus lucifugus was studied with the electron microscope. Animals were killed by intracardial perfusion at each season throughout the year so that the arcuate nucleus could be examined for seasonal variations in morphology. Striking seasonal changes in the fine structure of ependymal tanycytes lining the arcuate nucleus were observed. Tanycytes in animals collected in the fall and early winter exhibited pale processes characterized by a scant internal framework of microtubules and fine filaments. These processes, which were found throughout the arcuate nucleus, exhibited simple irregular shapes. In animals collected between January and June, tanycyte processes contained dense accumulations of fine filaments intermingled with microtubules, and projected long attenuated extensions that often formed multilamellar sheets around axodendritic terminals or other neuronal elements. Tanycyte processes of animals collected in July and August were densely packed with microtubules and fine filaments. The processes radiated elaborate multilamellar extensions that encapsulated axons, dendrites and even entire neuronal perikarya. Multilamellar sheets consisted of as many as 10 or 12 closely spaced gyres. The seasonal variations in tanycyte structure are suggestive of astrocyte-like behaviour. These changes are discussed with respect to seasonal changes in hypothalamic neuroendocrine activity.

Experimental studies on the seasonal variation of the rotifer Keratella cochlearis (Gosse)

A culture containing the rotifer Keratella cochlearis was divided into two aliquots, one reared at + 20°C and the second at + 5°C, all other conditions being identical. The experimentl lasted 74 days. At 20°C the animals did not undergo any noticeable morphological changes, while at 5°C the posterior spines grew longer, a development which had nearly reached its maximum as early as 30 days after the experiment began, i.e. after very few generations. The experiment shows that the temperature (and its direct consequences, such as slower growth) plays an important role in causing seasonal morphological variation in this rotifer. The results are in accordance with field experience as well as with culture experiments on other brachionid rotifers.

ENVIRONMENTAL CONTROL OF SEASONAL VARIATION IN THE BUTTERFLY COLIAS EURYTHEME. I. ADAPTIVE ASPECTS OF A PHOTOPERIODIC RESPONSE.

Organisms respond in a variety of ways to changing environmental conditions. They can maintain a single, broadly adapted phenotype in the face of environmental fluctuations with the expectation that, on the average, at least some members of a population will survive most conditions. Or, a population can maintain a variety of genetically determined phenotypes in anticipation of environmental changes. Finally, many organisms have evolved means of varying their phenotypes on cue, according to the environmental conditions they face. Frequently this is a reversible process, as is temperature acclimation (see Kinne, 1970). If environmental conditions cycle in a regular fashion as do the seasons in temperate zones, it may be advantageous for phenotypes to vary in anticipation of forthcoming changes. For example, insects avoid harsh winter (or summer) conditions by entering diapause; this may be determined long in advance of the onset of environmental adversity, and frequently long before the physiological modifications involved occur (Danilevsky et al., 1970; Levins, 1968). While animals could respond directly to such environmental parameters as temperature, such a response allows them no reliable way of predicting a change in living conditions before it actually occurs. The single most reliable indicator of seasonal change is photoperiod. (Photoperiodism in insects has been thoroughly reviewed: Beck, 1968; Danilevskii, 1965; Danilevsky et al., 1970; Lees, 1968; and de Wilde, 1962.) Multivoltine insects are faced with anticipating changes of the seasons and adjusting development accordingly for maximal fitness during each portion of the year. Although an indirect index of thermal change, photoperiod is a noise-free signal, completely unaffected by short-term meteorological changes, and, indeed, it determines long-term climatological change of interest to the organism. Diapause is a common, but not the only, photoperiodically determined response in the insects. Many also exhibit seasonal morphological variation. The changes in morphology may be as subtle as changes in aedeagus (penis) morphology in the leaf hopper, Euscelis plebejus (Muller, 1957), or they may be so striking that the seasonal morphs were at first mistaken for separate species, as with the butterfly Araschnia levana (Danilevskii, 1965). Many pierid butterflies also exhibit seasonal variation that involves the melanic and pteridine pigmentation of the wing surfaces. For instance, Pieris rapae, the European cabbage butterfly now widespread in North America, is rather dark in coloration in the spring and light in the summer (Kolyer, 1966, 1969; Hoffmann, pers. obs.). The alfalfa butterfly Colias eurytheme Boisduval (a pierid), together with its near relatives, C. philodice Latreille and C. eriphyle Edwards, is highly multivoltine and widely distributed over most of the North American continent. It has been known for some time to exhibit phenotypic variation, depending upon the season of collection. The cold weather and warm weather forms, which differ most strikingly in the extent of dark melanin pigment on the hindwing undersides, have been accorded the varietal names ariadne and amphidusa, respectively (Klots,