Between-habitat comparison of digestive enzymes activities and energy reserves in the SW Atlantic euryhaline burrowing crab Neohelice granulata

The digestive and metabolic characteristics at the biochemical level underlying between-habitat dietary shift of the SW Atlantic euryhaline burrowing crab Neohelice granulata under natural conditions are unknown. We made studies on adult males of N. granulata from the open mudflat and the vegetated saltmarsh in a SW Atlantic costal lagoon (Mar Chiquita, 37°32'-37°45'S; 57°19'-57°26'W, Argentina). We determined and compared amylase, maltase, sucrase, proteolytic, lipase and alkaline phosphatases activities in the hepatopancreas; glycemia, and glycogen, free glucose, triglycerides and protein concentrations in hepatopancreas, chela muscle, and anterior and posterior gills. The results show that N. granulata exhibits characteristics and between-habitat differences at the biochemical level (i.e. high amylase and disaccharidase activities, differences in total proteolytic, lipase and levamisole-insensitive AP activities in the hepatopancreas, and in the concentrations of glycogen in the gills, triglycerides in the hepatopancreas and of protein in the chela muscle) which could represent adaptive digestive and metabolic strategies to face the differences in environmental conditions (i.e. food availability). The possible relationship between digestive and metabolic characteristics and feeding patterns, type of food available and environmental conditions in each habitat is discussed.     

Pollen of the Asteraceae from the Paleocene-Eocene of South Africa

Two species of dispersed pollen (Tubuliforidites antipodica and T. viteauensis) that have affinity with the Asteraceae were recovered from Paleocene-Eocene sediments of South Africa. This is the earliest unequivocal record of the Asteraceae. The two species were examined with light, scanning, and transmission electron microscopy. The pollen wall structure of both taxa are of the Anthemoid type, a pollen wall structural type considered to be primitive among asteraceous pollen. The wall structure type is indicative of many taxa of the Mutisieae. The appearance of this pollen type in the Paleocene-Eocene of South Africa supports a early Tertiary, west Gondwana origin of the Asteraceae, and the evolutionary basal position of the Mutisieae.     

Nutrient reserves may allow for genome size increase: evidence from comparison of geophytes and their sister non-geophytic relatives

Background and Aims

The genome size of an organism is determined by its capacity to tolerate genome expansion, given the species'' life strategy and the limits of a particular environment, and the ability for retrotransposon suppression and/or removal. In some giant-genomed bulb geophytes, this tolerance is explained by their ability to pre-divide cells in the dormant stages or by the selective advantage of larger cells in the rapid growth of their fleshy body. In this study, a test shows that the tendency for genome size expansion is a more universal feature of geophytes, and is a subject in need of more general consideration.

Methods

Differences in monoploid genome sizes were compared using standardized phylogenetically independent contrasts in 47 sister pairs of geophytic and non-geophytic taxa sampled across all the angiosperms. The genome sizes of 96 species were adopted from the literature and 53 species were newly measured using flow cytometry with propidium iodide staining.

Key Results

The geophytes showed increased genome sizes compared with their non-geophytic relatives, regardless of the storage organ type and regardless of whether or not vernal geophytes, polyploids or annuals were included in the analyses.

Conclusions

The universal tendency of geophytes to possess a higher genome size suggests the presence of a universal mechanism allowing for genome expansion. It is assumed that this is primarily due to the nutrient and energetic independence of geophytes perhaps allowing continuous synthesis of DNA, which is known to proceed in the extreme cases of vernal geophytes even in dormant stages. This independence may also be assumed as a reason for allowing large genomes in some parasitic plants, as well as the nutrient limitation of small genomes of carnivorous plants.     

Fitness consequences of alternative life histories in water striders,Aquarius remigis (Heteroptera: Gerridae)

Using field and laboratory observations and experiments over 3 years, I investigated whether reproductive trade-offs shape individual life histories in two natural populations of the water strider, Aquarius remigis, in which univoltine and bivoltine life cycles coexist. Both later eclosion dates and food shortages, even after adult eclosion, induced diapause in females, thus deferring reproduction to the following spring. Adult body size was positively affected by food availability during juvenile development. Higher food levels also increased the reproductive output of females, but not their longevity or oviposition period. When compared to spring breeders (univoltine life cycle), direct (summer) breeders (bivoltine life cycle) experienced reduced lifetime egg numbers and longevity, as well as reduced survivorship of their second-summer-generation offspring; these reproductive costs offset, at least in part, the advantage in non-decreasing populations of having two generations per year. Fecundity was correlated with body size, and among summer-generation females direct breeders were larger than non-breeders. The time remaining before the onset of winter and/or the time since adult eclosion augmented cumulative energy uptake, and consequently the lipid reserves and winter survival probability of non-breeding (diapausing) summer adults approaching hibernation. Overwintered spring reproductives died at faster rates than non-reproductive summer individuals despite greater food availability in spring, indicating a mortality cost of reproduction. Body length correlated with absolute and not with proportional lipid content but showed no consistent relationship with survivorship in the field. These results are in agreement with current theory on the evolution of insect voltinism patterns, and further indicate high degrees of life history flexibility (phenotypic plasticity) in the study populations in response to variable environmental factors (notably photoperiod and food availability). This may be related to their location in a geographic transition zone from uni- to bivoltine life cycles.     

Retranslocation of carbon reserves from the woody storage tissues into the fruit as a response to defoliation stress during the ripening period in Vitis vinifera L.

A technique for reliable labeling of the carbon reserves of the trunk and roots without labeling the current year's growth of grapevines was developed in order to study retranslocation of carbon from the perennial storage tissues into the fruit in response to defoliation stress during the ripening period. A special training system with two shoots was used: the lower one (feeding shoot) was cut back and defoliated to one single leaf (¹⁴CO₂-feeding leaf) while the other (main shoot) was topped to 12 leaves. The potted plants were placed in a water bath at 30 °C to increase root temperature and therefore their sink activity. Additionally, a cold barrier (2–4 °C) was installed at the base of the main shoot to inhibit acropetal ¹⁴C translocation. Using this method, we were able to direct labeled assimilates to trunk and roots in preference to the current year's growth. On vines with root and shoot at ambient temperature, 44% of the ¹⁴C activity was found in the main shoot 16 h after feeding whereas only 2% was found in the temperature-treated vines. At the onset of fruit ripening, and at three-week intervals thereafter until harvest, potted grapevines were fed with ¹⁴CO₂ using the temperature treatment described above. Sixteen hours after feeding, half of the vines of each group were defoliated by removing all except the two uppermost main leaves. Three weeks after each treatment, vines were destructively harvested and the dry weight and ¹⁴C incorporation determined for all plant parts. Under non-stressing conditions, there was no retranslocation of carbon reserves to support fruit maturation. Vines responded to defoliation stress by altering the natural translocation pattern and directing carbon stored in the lower parts to the fruit. In the three weeks following veraison (the inception of ripening in the grape berry), 12% of the labeled carbon reserves was translocated to the fruit of defoliated plants compared to 1.6% found in the clusters of control vines. Retranslocation from trunk and roots was highest during the middle of the ripening period, when 32% of the labeled carbon was found in the fruit compared to 0.7% in control plants. Defoliation during this period also caused major changes in dry-matter partitioning: the fruit represented 31% of total plant biomass compared to 21% measured in the control vines. Root growth was reduced by defoliation at veraison and during the ripening period. Defoliation three weeks before harvest did not affect dry matter or ¹⁴C partitioning.     

Mixotrophic growth ofChlorella sorokiniana in outdoor enclosed photobioreactor

Chlorella sorokiniana was cultured in heterotrophic or mixotrophic mode in outdoor enclosed tubular photobioreactor. The culture temperature was maintained at 32–35 °C. At night, theChlorella culture grew heterotrophically, and 0.1 M glucose was completely consumed. The biomass growth yield of glucose was 0.35 ± 0.001 g-biomass g-glucose^–1. During the day, the algal culture grew mixotrophically and the biomass growth yield was 0.49 g-biomass g-glucose^–1 in low density culture (initial biomass concentration, X_o = 2 g l^–1), 0.56 g-biomass g-glucose^–1 in medium density culture (X_o = 4 g l^–1) and 0.46 g-biomass g-glucose^–1 in high density culture (X_o = 7 g l^–1). The daily area productivity of the culture, with X_o = 4 g l^–1 corresponded to 127 g-biomass m^–2 d^–1 during the day and 79 g-biomass m^–2 d^–1 during the night. In all the cultures, the dissolved O₂ concentration increased in the morning, reached the maximum value at noon, and then decreased in the afternoon. The dissolved CO₂ concentration remained at 3 mBar in the morning and increased in the afternoon. Glycolate was not found to accumulate in culture medium.     

Short- and long-term advantages of an alternative ontogenetic pathway

We documented hypotheses on the evolution of developmental heterochronies by estimating short- and long-term advantages of alternative morphs. In this respect, we compared food energy intakes and body condition between paedomorphic and metamorphic Alpine newts ( Triturus alpestris , Caudata, Amphibia) in four populations. Because we found a strong correlation between fat reserves and body condition, we used this last parameter as an indicator of long-term gains. In all studied sites, paedomorphic females showed higher body condition than metamorphic ones. Paedomorphic males were also at advantage in two populations. Paedomorphs exhibited higher energy intakes than metamorphs in two populations and similar gains in two others. Our results support unifying theories that predict the occurrence of facultative paedomorphosis in varied habitats as paedomorphs exhibited better energy balance than metamorphs. This work shows the need for considering integrative parameters such as body condition in the comparative study of performances when studying developmental heterochronies. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 105–112     

Fruit-bearing branchlets are carbon autonomous in mature broad-leaved temperate forest trees

In order to evaluate the degree of carbon autonomy for fruit development, the carbon source-sink relationship in fruit-bearing branchlets of mature deciduous forest trees was manipulated in situ. The tests included half and complete defoliation, girdling or the combination of both treatments, which were applied on fruiting branchlets by using a canopy crane. Concentrations of non-structural carbohydrates (NSC) were analysed in different branchlet tissues and fruits, to identify situations of carbon imbalances induced by the treatments. NSC concentrations of branchlets were generally lower under treatments resulting in decreased fruit growth. All three investigated species (Carpinus betulus, Fagus sylvatica and Tilia platyphyllos) exhibited complete carbon autonomy of fruiting at the level of whole, undisturbed branchlets, since neither a decrease of total infructescence biomass, nor of individual fruit mass occurred on girdled, un-defoliated branchlets. On girdled, 100% defoliated branchlets, fruit biomass relative to controls decreased by approximately 50% in Carpinus and Tilia, but by almost 80% in Fagus, which can be explained by different proportions of photosynthetically active infructescence tissues among the species. In contrast to the other two species, Tilia branchlets did not import carbon to compensate for assimilate loss after defoliation.     

Deteriorating effects of diapause duration on postdiapause life history traits in the Kanzawa spider mite

Abstract. The aim of this study is to clarify the deleterious effects of long‐term diapause on survival, postdiapause number of offspring and longevity in two populations of Kanzawa spider mite Tetranychus kanzawai Kishida (Acari: Tetranychidae), which were collected from Orixa japonica (Rutaceae) and Hydrangia hirta (Saxifragaceae) in Kyoto Prefecture, Japan. As the chilling period lengthens, the rate of surviving females declines more steeply in the Orixa population than the Hydrangea population. In the Orixa population, the offspring numbers of diapausing females chilled for 30 or 90 days are not significantly different from those of the parental generation, whereas they decrease to approximately one‐half that of the parental generation in the Hydrangea population. The postdiapause longevity in the 30‐ or 90‐day chilling treatments does not shorten significantly compared with that of parental generation in the Orixa population, but the longevity of the Hydrangea population declines significantly after these chilling periods. These results suggest that deteriorating effects of diapause act in a quite different manner in the two populations. A possible mechanism generating such a difference is discussed in view of trade‐off between the maintenance of body conditions and survival during hibernation.     

The effect of a seasonal time constraint on development time, body size, condition, and morph determination in the horned beetle Allomyrina dichotoma L. (Coleoptera: Scarabaeidae)

Abstract.  1. In horned beetles selection favours males that adjust their investment in horn development in relation to cues that predict adult body size. Here it is shown that in the Japanese horned beetle, Allomyrina dichotoma . There is a significant discontinuity in the horn length body size allometry. This can be described as a linear relationship that is shifted towards an increased horn length to body length ratio in males with horns longer than 16 mm.
2. Larval nutrition explains morph determination in A. dichotoma . However, unlike other species, variation in larval nutrition was the result of a seasonal time constraint that limits the time available for feeding prior to the onset of winter diapause.
3. Even when eggs were reared with an ad libitum food supply, minor morphs were still observed. Individuals that were oviposited later in the season had less time to feed, shorter development times, eclosed as smaller individuals and, in the case of males, were more likely to be hornless. Major morphs, minor morphs, and females all reduced their body size in response to seasonal time constraints in the same way. However, males that were laid later in the season had faster development times than females laid at the same time, but showed no reduction in their size relative to females, suggesting seasonal time constraints increase growth rates in males but not in females.
4. No evidence was found that seasonal time constraints resulted in a reduction of size-corrected fat reserves at eclosion, or that minor morphs gained any developmental advantage by reducing investment in horn length.