Aquatic prey switching and urban foraging by the White Ibis Eudocimus albus are determined by wetland hydrological conditions

Prey availability is known to limit reproduction of some species of nesting birds, but identifying the primary prey types of a species with a flexible diet can be challenging. For the White Ibis Eudocimus albus, a tactile feeding, medium‐sized wading bird, nestling prey composition is suggested to depend on landscape water depths/availability of foraging habitat at the time of nesting and on historical drying events affecting prey production. We collected and compared inter‐ and intra‐annual diet variation of White Ibis chicks reared in the Everglades over two years that were independently identified as being relatively good (2006) and poor (2007) nesting seasons. We collected 127 nestling boluses and analysed the temporal variation in biomass of eight functional prey groups using multivariate techniques. The boluses from 2006 in the central Everglades were dominated by fish, but in 2007, after fish had been reduced by the previous year of drying, the boluses from the same region were more variable and dominated by garbage (i.e. scavenging). Analysis of five different collections taken from a different colony in the northern Everglades indicated that boluses were characterized by crayfish and had fewer fish or less garbage when landscape water depths were relatively higher and more preferred habitat was available. At lower landscape water depths in 2007 the bolus composition shifted away from crayfish towards small fish and urban food (terrestrial insects and garbage). Our results support the suggestion of depth‐dependent diets; prey composition depends on the current landscape water levels around the colonies, and also suggests that previous drying events can lead to increased reliance on alternative food sources. White Ibis partially compensated for unavailable aquatic prey with alternative urban foods, but their nesting success appears to have suffered.     

How Can Stomata Contribute to Salt Tolerance?

Although some of the physiological mechanisms which contributeto salt tolerance in plants are known, there are still somemajor gaps in understanding and it remains impossible to providea satisfactory integrated picture for the plant as a whole.The operation of stomata in halophytes has received little attentioneven though all of the salt present in the shoot (apart fromthat taken in during submergence) is thought to be carried inthe transpiration stream. In non-halophytes, stomatal functionis damaged by sodium ions, and disruption of the normal regulationof transpiration should be seen as a possible contributor totheir inability to survive in salt-laden soils. The developmentof salt-tolerant cultivars of crops may require attention tothe need for appropriate adaptations to the ionic relationsof stomatal guard cells. Despite the small amount of evidenceavailable, it is possible to identify two alternative adaptationsthat occur in the stomata of halophytes: (1) the guard cellscan utilize Na⁺instead of K⁺to achieve their normal regulationof turgor; (2) the guard cells continue to use K⁺and are ableto limit their intake of Na⁺. The second adaptation is worthyof further exploration because it may provide a means for ‘topdown’ control of transpiration and, therefore, of theamount of salt delivered to the shoot. This mechanism may bevery important in some of the glandless halophytes, and it couldbe of particular interest as a potential contributor to thedevelopment of salt tolerance in crops. Salt tolerance; stomata; transpiration; halophytes; ionic regulation; sodium ions     

Root Initiation in Cuttings of Pinus radiata Seedlings: II. GROWTH REGULATOR INTERACTIONS

Effects of exogenous growth regulators are related to the histologicalevents in adventitious root initiation in hypocotyls of Pinusradiata D. Don. Indolebutyric acid (IBA) is required both forthe pre-initiative and post-initiative phases in root development.Kinetin has a marked inhibitory effect over the pre-initiativephase, with escape from inhibition following establishment ofmeristemoids. Gibberellic acid (GA₃) has three distinct effectsdepending on time of application. While inhibitory during thepre-initiative phase, it strongly enhances rooting if appliedat a time coincident with the first observable stage of rootinitiation. If applied following establishment of meristemoids,GA₃ inhibits root formation.     

Action cascade of an insect gonadotropin,testis ecdysiotropin,in male Lepidoptera

Summary

Testis sheaths from late last instar larvae and mid-developing pupae of Heliothis virescens and Lymantria dispar synthesize ecdysteroid in vitro. Gonadal ecdysteroid can stimulate the production of growth factors from the sheaths which, in turn, promote the growth and development of the genital tract. Ongoing basal synthesis is controlled by positive feedback to exogenous ecdysteroid; titers of this hormone approaching those of molting last instar larvae and developing pupae effect maximum synthesis. These findings suggest that circulating titers of ecdysteroid hormone promote gonadal ecdysteroidogenesis, and thus coordinate the actions of the gonads with metamorphic events in the whole animal. Synthesis of ecdysteroid by testes is initiated, however, by a brain neuropeptide, testis ecdysiotropin (TE). TE is a 21 amino acid peptide of molecular weight 2472 Da. TE boosts basal steroid synthesis by pupal testis sheaths as well. It acts primarily via G_i protein and second messengers diacyl glycerol and low calcium influx, resulting in stimulation of phosphokinase C. G_s protein and its resultant messenger, cyclic AMP, also play roles in activation and inhibition of ecdysteroidogenesis. The interplay of controlling systems probably serves to fine tune a system essential to gonadal development and function.     

Meristem Tip Culture in Lolium multiflorum

Complete plants were regenerated from meristem tips of Loliummultiflorum. Of the three basal culture media used, Murashigeand Skoog's medium gave the best results. Plantlets were produced without exogenous auxins or cytokinins,but 0.2 mg 1^–1 kinetin favoured development. As the mainaim in the development of this technique is the eliminationof viruses, the possibilities of using 2,4.D in the culturemedium and of culturing very small meristem tips for this purposewere considered.     

Models of Cell Number Increase in Developing Leaves

Negative logistic and negative exponential models to accountfor cell number changes in primary leaves of Phaseolus are considered.The negative exponential model gives a close fit to observeddata for cell number when the average division time is 12 h.From this model it is considered that about 20 per cent of thecells in the leaf are capable of continued division at the timewhen divisions actually cease.     

Impact of fuel-reduction burning on the frog Geocrinia lutea in southwest Western Australia

Abstract The four frog species in the Geocrinia rosea complex occur in state forest in southwest Western Australia. Fire management of these forests involves fuel-reduction burning with an average rotation of five to nine years. In this study we examined the impact of fire on Geocrinia lutea by counting calling males in six pairs of burned and control sites from 1992 to 1994. The immediate impact of the fire on G. lutea adults, and the survival of G. lutea eggs and larvae after the fire, were also addressed. We found that fuel-reduction burning in spring was associated with a significant decline in the number of calling males. The populations had not recovered two years after the fire. Up to 29% of the calling males may have been killed in the fire. Egg and larval survival was not significantly different between treatments. However, the treatments did differ in the cause of death, with higher in-situ egg death and lower predation at burned sites. The short-term impact of spring fuel-reduction burns may pose a serious threat of extinction for very small populations. The endangered species Geocrinia alba has many small, isolated populations and frequent fire may therefore be inimical to their survival. However, we do not know if there is a long-term effect. Populations may or may not have time to recover between fires.