Elaiophores in three Neotropical Malpighiaceae species: a comparative study

Malpighiaceae species are recognized for their sepal elaiophores of which secretions reward oil-collecting bees. Information on elaiophore location, structure and functioning is likely to provide valuable insights into pollination ecology and evolution of the family. We characterized the elaiophores in three Malpighiaceae species and compared the patterns of distribution and dimensions of these glands, their structural organization, their histochemistry and their life spans. Intact elaiophores from buds and 1-day flowers (bagged and un-bagged) of Banisteriopsis variabilis, Byrsonima coccolobifolia and Peixotoa reticulata were collected for structural, histochemical and ultrastructural studies. We also reported the behavior of elaiophore-visiting insects. Elaiophores exhibit uniseriate secretory epithelium covered by a thick cuticle and vascularized parenchyma. The secretory surfaces can be flat (B. coccolobifolia and P. reticulata) or convoluted (B. variabilis). In B. variabilis and P. reticulata the epithelium has longer cells than in B. coccolobifolia and these become papillose, taking an appearance similar to trichomal elaiophores. The mixed secretions accumulate within subcuticular spaces and may be released either by a natural rupture of the cuticle (B. coccolobifolia and P. reticulata) or by a sudden rupture caused by the bee activity (B. variabilis). Different bees were observed exploiting the elaiophores, acting as potential pollinators or oil robbers. A greater diversity of oil-collecting bees was registered in B. variabilis. The differences identified, mainly in relation to the location of the glands on the sepals, in the fine structure of secretory epithelia and cuticle architecture, and in their secretion release mechanisms, in some way, can affect the behavior of visitors.     

三种鹭异步孵化与雏鸟生长的比较研究

根据1996～1999年的野外工作和实验饲养,研究了池鹭、白鹭、夜鹭3种鹭的繁殖、雏鸟生长和异步孵化对雏鸟生长的影响.3种鹭于4月上、中旬迁到常山、余杭鹭保护区,9月下旬陆续迁离.孵卵期池鹭为23.0 d(n=26),白鹭23.9 d(n=32),夜鹭25.3 d(n=34);孵化率池鹭为76.32%,自鹭86.96%,夜鹭95.45%,池鹭繁殖力为3.21只,白鹭3.38只,夜鹭3.50只.雏鸟体重增长与成体体形大小呈负相关.幼雏体重增长与孵化顺序相关.在生长早期(≤8 d)全部雏鸟正常发育,之后差异显著.第1和第2孵化雏鸟生长曲线相似,但明显高于第4雏鸟,表明较早孵化者获得食物能力较强,而迟孵出雏鸟有食物不足现象.该3种鹭孵育幼雏能力的最适度估计为3只左右.     

Critical thermal maxima of three species of Hawaiian estuarine fish: a comparative study*

Crticial thermal maxima (CTM) of three species of Hawaiian estuarine fishes were determined in relation to acclimation temperature and time of day. The species studied were Mugil cephalus L., Chelon engeli (Bleeker) and Kuhlia sandvicensis (Steindachner). Critical thermal maxima of all three species were significantly affected by acclimation temperature and time. In relation to acclimation temperature, Mugil cephalus and Chelon engeli have similar critical thermal maxima with Kuhlia sandvicensis having a critical thermal maxima about 1° C below that of the other two species studied. Mugil cephalus and Chelon engeli showed an increasing critical thermal maxima toward midday which decreased therafter. Critical thermal maximum of Kuhlia sandvicensis increased throughout the day.     

The Johnston's organ of three homopteran species: A comparative ultrastructural study

A transmission electron-microscopy study has been carried out on the pedicel of three homopteran species, with particular focus on the leafhopper Scaphoideus titanus Ball. The two other species, the planthoppers Hyalesthes obsoletus Signoret and Metcalfa pruinosa Say, were investigated in order to compare the ultrastructure of the Johnston's organ (JO) among representatives of the Auchenorrhyncha group. The results showed the presence of a well developed JO located within the pedicel. Depending on the species the JO is made of 25 up to 72 scolopidia arranged in a coronal array. Each scolopidium is connective, heterodynal, amphinematic and hosts three structurally dissimilar sensory neurons. Two of them have a type 1 ciliary segment while the third bears a type 2 cilium. The type 2 dendrite tip is associated with a tubular cap and is longer than the others, ending into the cuticle at the base of the flagellum. Other scolopidia with one or two neurons were found in S. titanus, forming an accessory organ. The presence of such a well developed mechanosensory apparatus is discussed in relation with the lifestyle of the three species.     

A comparative study of larval cannibalism in three species of ladybird

Abstract. 1. Cannibalism was studied under laboratory conditions in three species of Coccinellidae (Coleoptera): Cycloneda sanguinea , Olla v-nigrum , and Harmonia axyridis . Larval cannibalism varied among species, C. sanguinea  > H. axyridis  ≥  O. v-nigrum .
2. Larvae of all species cannibalised more in response to reduced food availability (14 h starvation daily) than in response to reduced food quality (dry Ephestia eggs).
3. Larvae of H. axyridis cannibalised siblings at lower rates than non-siblings, but larvae of C. sanguinea and O. v-nigrum did not. Rates of cannibalism increased significantly with increasing size disparity among larvae of all three species.
4. Cannibalism in C. sanguinea and H. axyridis , but not in O. v-nigrum , increased with larval density, suggesting that not all attacks on conspecifics are driven by hunger.
5. Costs, not benefits, were the predominant effects of exclusively and partially cannibalistic diets. A diet of conspecific eggs yielded survival equivalent to the Ephestia egg diet for H. axyridis and O. v-nigrum , but developmental time was extended and adults were smaller. Larvae of C. sanguinea had superior survival and faster development on conspecific eggs than on the Ephestia egg diet. Only H. axyridis larvae survived as well on diets comprised exclusively or partially of conspecific larvae as on Ephestia eggs, although they developed more slowly.     

A comparative study of aboveground biomass of three Mediterranean species in a post-fire succession

The aboveground biomass of three woody species (Cistus albidus, Quercus coccifera and Pinus halepensis) in two early successional stages (3- and 10-year old) of a post-fire Mediterranean ecosystem was investigated. Among these three species, which belong to the successional series of holm oak (Quercus ilex), C. albidus and Q. coccifera are two dominant shrub species in the garrigue ecosystem and P. halepensis is a pioneer tree species widely represented in the Mediterranean area. The results obtained showed that in monospecific stands, C. albidus and Q. coccifera had a high recovery potential. In the 3-year-old stands, the cover of P. halepensis was only 19.8% for a total biomass of 0.75 ± 0.21 t ha^–1, while the plant cover of C. albidus and Q. coccifera was, respectively, 26% and 85.5% and biomass was 4.72 ± 1.09 and 11.5 ± 0.16 t ha^–1. Only 10 years after fire, the plant cover of C. albidus and Q. coccifera was, respectively, 55% and 100% and total biomass 13.2 ± 1.7 and 35.8 ± 4.7 t ha^–1. The greatest increase in biomass was noted for P. halepensis (29.7 t ha^–1). If mean annual biomass increments are considered, it appears that there was a significant decrease with the stand age for the two shrub species although the tree species showed an increase in productivity. These differing patterns in biomass and productivity of shrub and tree species with stand age provide information on biomass accumulation rates of pioneer species in a Mediterranean succession and their importance in the vegetation dynamics.     

A comparative study of positional behavior in three species of tamarin monkeys

Tamarins of the genusSaguinus are small-bodied New World monkeys that exhibit clawlike or modified nails. Patterns of positional behavior and habitat utilization are presented for three species,Saguinus fuscicollis, S. geoffroy, andS. mystax. These data were collected on free-ranging tamarin populations in Panama and Peru. Despite considerable differences in body weight, all three species exhibited very similar patterns of positional behavior, with quadrupedal bounding and running accounting for 43 – 52% of travel time. Leaping was the second most common locomotor activity and accounted for 31 – 41% of travel. Although each species leaped principally on small supports in the perimeter of the tree crown, approximately 20% of all leaps inS. fuscicollis involved moderate to large sized vertical trunks located in the undercanopy. Leaping between trunks was rare in the two larger tamarin species. Measurements taken on live wild-trapped adults reveal that compared toSaguinus geoffroyi andS. mystax, S. fuscicollis is characterized by a long legspan and an especially long armspan. It is proposed that inS. fuscicollis, elongated forelimbs play an important role in maneuvering and rotating the body during the in-air phase of trunk-to-trunk leaping, and increase the breaking distance needed to decelerate the body upon impact. Additional relationships between body size, substrate preference, and positional behavior in callitrichines are discussed.     

Morphology and tenacity of the tube foot disc of three common European sea urchin species: a comparative study

The variation in tenacity of single tube feet from three sea urchin species with contrasted habitats was assessed and correlated with the ultrastructure of their adhesive secretory granules. The tube feet of Arbacia lixula and Sphaerechinus granularis have larger discs and more complex adhesive granules than those of Paracentrotus lividus, but A. lixula attaches to glass with significantly lower tenacity (0.05-0.09 MPa) than the other two species (0.10-0.20 and 0.11 -0.29 MPa, respectively). However, the estimated maximal attachment force one tube foot can produce is similar for all three species investigated. No clear relationship between tube foot size, tenacity, adhesive secretory granule ultrastructure and species habitat can therefore be established. For P. lividus the tenacity of single tube foot discs on four different smooth substrata was also compared, which showed that both the total surface energy and the ratio of polar to non-polar forces at the surface influence tube foot attachment strength. This influence of the surface characteristics of the substratum appears to affect the cohesiveness of the adhesive secretion more than its adhesiveness.     

The influence of synoptic weather patterns on the at-sea behaviour of three species of albatross

The relationships between behaviour and synoptic-scale weather patterns and wind speeds for wandering (Diomedea exulans), black-browed (D. melanophrys) and light-mantled sooty (Phoebetria palpebrata) albatrosses were examined using observations collected from ships in the Southern Ocean south of Tasmania, Australia. Wandering albatrosses were found in high-pressure systems in significantly higher numbers than expected than in low-pressure systems. Wandering albatrosses were also found more frequently at lower latitudes than were black-browed and light-mantled sooty albatrosses. Light-mantled sooty and black-browed albatrosses showed no significant association with high- or low-pressure systems, suggesting that they can use either pressure system for travel. High-pressure systems may act as "traps" for wandering albatrosses, due to the lower wind speeds generally associated with these systems.     

Chick growth rates in Charadriiformes: comparative analyses of breeding climate, development mode and parental care

The rate at which a young bird grows is highly diverse across taxa. We investigated the influences of ecological variables on growth rates of shorebirds, gulls and their allies (order Charadriiformes) using comparative analyses of 68 species. We investigated three hypotheses: (1) exposure to cold temperatures results in reduced growth rate due to the increased energy expenditure required for thermoregulation, (2) fast growth rates allow offspring to complete development in habitats with short periods of fair ecological conditions, and (3) parental feeding allows the offspring to grow faster than self-feeding offspring. Charadriiform species are suitable for testing these hypotheses, because they breed in diverse environmental conditions that include Arctic and Antarctic habitats, temperate zones and tropics, and in some species the offspring feed themselves (precocial) whereas in others they are fed by the parents (semi-precocial). First, we tested the influence of ambient temperature on growth rate and we found that species breeding in cold habitats had faster growth rates than species breeding in warm temperatures. The relationship between growth rate and ambient temperature was not significantly different between precocial and semi-precocial offspring. Second, we tested the influence of the length of the breeding season on growth rate, and we found that species with shorter breeding seasons had faster growth rates than species with longer breeding seasons. Finally, we show that precocial offspring grew slower than semi-precocial offspring, and this relationship remains significant when the influences of ambient temperature and breeding season length are statistically controlled. In conclusion, our work, using phylogenetically corrected models, confirms that ambient environment and developmental mode of young together influence the growth of Charadriiform chicks, and their effects are additive.     

Complex growth rate evolution in a latitudinally widespread species

The simultaneous effects of selective agents acting on somatic growth rates, their interactions, and their interactions with local environmental conditions that vary across a species' geographic range are potentially complex and poorly known. This is particularly true of viviparous ectotherms whose offspring may be adapted to the gestation environment provided by their mothers. We studied multiple sources of growth rate variation in a widespread, viviparous reptile, including the effect of the maternal environment on growth following parturition. Females in early pregnancy were collected from replicate populations close to the tropical and temperate margins of this species' range. These females completed gestation in either of two different, common environments designed to simulate the thermal and photoperiod environments at the sampling locations. Our experiments revealed complex growth rate evolution between the northern and southern extremes of Eulamprus quoyii's geographic range and local adaptation of growth rates to maternal environments. Unique to this study was the manifestation of these growth rate differences, entrained in utero, but expressed following parturition and maintained through to maturity despite the presence of compensatory growth. In addition to providing the most complete picture to date of the evolution of somatic growth in a viviparous ectotherm, our study suggests that understanding local adaptation to maternal gestation environments, in terms of both mean growth rates and growth rate reaction norms, could change our understanding of how growth rates have evolved in other viviparous ectotherms. Indeed, such local adaptation may provide a selective advantage in the evolution of viviparity.     

The relationship between size,budding rate,and growth efficiency in three species of hydra

Three species of the fresh water carnivore hydra, H. littoralis, H. pseudoligactis, and C. viridissima present a graduation in size with the first species the largest and albino Chlorohydra the smallest. When presented with a daily overabundance of food (artemia), considerable variation in food intake and gross efficiency of growth (proportion of food energy consumed that is turned into new protoplasm or buds) existed among the species. The degree of association between size of species and food intake was highly significant. However, budding efficiency among the species was found to be independent of food intake (when the effects of species size were eliminated) and of species size (when the effects of food intake were removed). However, species with high (low) efficiencies have significantly higher (lower) reproductive rates. A lowering of the temperature from 25° to 15° C. increased the size of the species, increased food intake, but decreased reproductive rate. In all species except H. pseudoligactis a corresponding increase in the production of bud energy with no change in efficiency also occurred. On the other hand, lowering of the temperature for H. pseudoligactis significantly lowered reproductive efficiency but had no effect on the total calorific output of buds. This species, in constrast to the others, appears to have a compensatory ability to adjust its efficiency to maintain a high calorific output when temperature increases. It was also found that albino Chlorohydra have budding efficiencies of around 35 percent which are not influenced by changes in food intake or light. Normal green hydras, however, have efficiencies which range from 40 to 62 percent above their albino counterparts when fed once a day and once every two days in light respectively. It it concluded first, that the symbiotic algae in the gastrodermals cells of green hydra contribute quantitatively in the order of the above amounts to the growth process in this species, and second, that green hydras have the ablity to increase their growth efficiency when food intake is reduced thus reducing the drop in calorific but output that normally occurs in the albino (control) form.     

Chick growth in albatrosses: curve fitting with a twist

We present a new type of equation to describe the growth patterns of procellariiform seabirds and other species whose chicks characteristically lose mass towards the end of the rearing period. Our equation is based on the Gompertz curve; our principles are also applicable to logistic and von Bertalanffy curves. From our model, five coefficients can be derived to characterise the patterns of growth. These are: growth rate, peak mass and age at which it is attained, loss rate and an index describing the overall shape of the curve. We illustrate the use of this new equation with data collected, using automated weighing platforms, on six years of chick growth of Black-browed Diomedea melanophris and Grey-headed D. chrysostoma albatrosses at Bird Island, South Georgia. In comparison with Grey-headed Albatross, Black-browed Albatross chicks grow at a faster rate and to a higher peak mass; they also reach their peak mass at an earlier age, and lose mass at a faster rate in the mass recession period. However, in both species, chicks reached peak mass when 72% of the rearing period had elapsed; within species, only this did not vary between years. This new equation not only enables the period of mass recession to be incorporated into growth analysis, but, because it does not require assumptions about asymptotic mass, greatly facilitates inter-species comparisons.     

Mating strategies in two species of dart-poison frogs: a comparative study

Comparative field studies of species of dart-poison frogs in the genus Dendrobates were carried out to test predictions from two hypotheses that attempt to explain female-female competition for mates in species of Dendrobates with male parental care. The sex role reversal hypothesis proposes that males invest so much time and energy in parental care that receptive males are rare relative to receptive females, and females compete to find and mate with receptive males. The parental quality hypothesis proposes that females compete to monopolize the parental effort of particular males, because they potentially suffer a cost when their mates care for the offspring of other females. Comparisons between species with male parental care (Dendrobates leucomelas) and female parental care (Dendrobates histrionicus) contradicted prediction of the sex role reversal hypothesis, but were consistent with predictions of the parental quality hypothesis. Male D. histrionicus did not compete for mates more aggressively than male D. leucomelas, and male D. leucomelas were not more selective about mating than male D. histrionicus. Female D. leucomelas and D. histrionicus were both selective about mating; female D. leucomelas associated with and competed for particular males, whereas female D. histrionicus did not.     

A comparative study of bark lectins from three elderberry (Sambucus) species

Three elderberry lectins isolated from the bark of three different species of the genus Sambucus which are native to Europe (S. nigra), North America (S. canadensis), and Japan (S. sieboldiana) were studied comparatively with regard to their carbohydrate binding properties and some structural features. All three lectins contained two identical carbohydrate binding sites per molecule and showed a very high specificity for the Neu5Ac(alpha 2-6)-Gal/GalNAc sequence. However, relative affinities for various oligosaccharides were significantly different among them, suggesting differences in the detailed structure of the carbohydrate binding sites of these lectins. The three lectins were immunologically related, but not identical, and all were composed of hydrophobic and hydrophilic subunit regions, although the molecular sizes of these subunits were slightly different among the three lectins. N-terminal sequence analysis of the subunits of these lectins suggested that they have a very similar structure in this region but also indicated the occurrence of N-terminal processing such as the deletion of several amino acid residues at the N-termini for both hydrophobic and hydrophilic subunits of all three lectins. Tryptic peptide mapping of the three lectins showed a similar pattern for all of them but also showed the presence of some unique peptides for each lectin.     

Glucagon-initiated human growth hormone release: a comparative study

Human growth hormone (HGH) responses in 20 healthy adults to subcutaneous glucagon, arginine infusion and tolbutamide and insulin hypoglycemia were compared. HGH rose in all four tests. HGH response to glucagon was also studied in 49 patients with suspected pituitary insufficiency, of whom 25 also later received an arginine infusion; an abnormal response to glucagon was the most frequent functional abnormality and often HGH was the only anterior pituitary hormone of which a deficiency was detectable. In seven subjects (two healthy controls and five patients with suspected hypopituitarism) there was a subnormal HGH response to arginine but a normal response to glucagon. It is concluded that glucagon is a simple and effective stimulus to HGH release, equal or superior to arginine, tolbutamide and insulin, and is an important test of anterior pituitary function.