Hunger‐dependent and sex‐specific antipredator behaviour of larvae of a size‐dimorphic mosquito

1. Modification of behaviours in the presence of predators or predation cues is widespread among animals. The costs of a behavioural change in the presence of predators or predation cues depend on fitness effects of lost feeding opportunities and, especially when organisms are sexually dimorphic in size or timing of maturation, these costs are expected to differ between the sexes. 2. Larval Aedes triseriatus (Say) (Diptera: Culicidae) were used to test the hypothesis that behavioural responses of the sexes to predation cues have been selected differently due to different energy demands. 3. Even in the absence of water‐borne predation cues, hungry females (the larger sex) spent more time browsing than did males, indicating a difference in energy needs. 4. In the presence of predation cues, well‐fed larvae of both sexes reduced their activity more than did hungry larvae, and males shifted away from high‐risk behaviours to a greater degree than did females, providing the first evidence of sex‐specific antipredator behaviour in foraging mosquito larvae. 5. Because sexual size dimorphism is common across taxa, and energetic demands are probably correlated with size dimorphism, this research demonstrates the importance of investigating sex‐specific behaviour and behavioural responses to enemies, and cautions against generalising results between sexes.     

A mathematical model describing the combined effect of exposure time and temperature of hot-water treatments on survival of gladiolus cormels

Gladiolus cormels of five cultivars were given hot-water treatments at 50.0°C, 52.5°C, 55.0°C or 57.5°C for different exposure times. Survival of cormels was determined. A mathematical model to describe the combined effect of exposure time and temperature on cormel death is presented. Consequences of these relationships for the practical application of hot-water treatments to control cormel-borne Fusarium oxysporum f.sp. gladioli are discussed.     

Dasyclads, cyclocrinitids and receptaculitids: comparative morphology and paleoecology

The cyclocrinitids are an extinct tribe of dasycladacean green algae. They were anatomically very similar to certain Recent dasyclads, even at early growth stages. The morphology and preservation of cyclocrinitids strongly suggest that they had a siphonous cellular organization with extracellular, aragonitic calcification; these features are characteristic of living dasyclads. The light surficial calcification of cyclocrinitids and other dasyclads had important paleoecological effects. It restricted them to low-energy waters, as it provided relatively little structural support. It also confined them to warm, tropical waters; they are good paleoequatorial indicators. The decline of these algae during the late Ordovician and early Silurian may therefore reflect the simultaneous cooling and glaciation. Receptaculitids are entirely unrelated organisms. Their meroms have several distinctive features; they are not homologous to the lateral branches of cyclocrinitids or dasyclads. Receptaculitid calcification was extensive and their thalli were apparently quite sturdy; they often occurred in reefs. Receptaculitids also lived in high-latitude, cold-water environments. Thus, they were ecologically unlike any calcareous green algae, and cannot be used as paleoequatorial indicators. Receptaculitids remain problematical, although the arrangement of meroms suggests plant affinities. □ Calcareous algae, Problematica, Dasycladales, Cyclocriniteae, Receptaculitales, morphology, classification, paleoecology, paleogeography .     

Identifying predators at nests of small birds in a New Zealand forest

Time-lapse video equipment was used to film continuously at nests of two small passerines, the New Zealand Robin Petroica australis and the Tomtit Petroica macrocephala , in an indigenous broadleaf/hardwood forest in central North Island, New Zealand. The nests were illuminated with infrared light to allow night-time observations of predator and parent bird behaviour, and signs left at nests were linked to predator identity. Introduced Ship Rats Rattus rattus and the small native owl or Ruru Ninox novaeseelandiae were filmed preying on eggs or chicks on 12 occasions, and Ship Rats scavenged on eggs on two occasions. Parent birds sometimes altered the signs left at nests after predation, which confused identification of the predator, while Ship Rat scavenger and predator signs were indistinguishable. This suggests that attempts to identify predators from nest signs could be misleading and potentially a widespread problem. Time-lapse video filming with infrared illumination is potentially the least biased method of identifying predators, but it is expensive and so is best used in conjunction with simpler methods. This study found no evidence that filming altered predation rates or that the predators or parent birds reacted strongly to the camera or lights, so we believe that filming is a valuable and safe technique to guide management for the recovery of critically endangered species that are threatened by predators.     

Expression of Embryonic Haemoglobin in ts AEV-Transformed Embryonic Erythroid Cells During Temperature-Induced Differentiation

Cells prepared from 1-day-old chick blastoderms were infected with a temperature-sensitive mutant of avian erythroblastosis virus ( ts AEV). Clonal strains of transformed erythroblasts were isolated from the infected blastoderm cells. By shift to the nonpermissive temperature, these cells could be induced to differentiate into erythrocyte-like cells which expressed embryonic haemoglobins. Embryonic haemoglobins could not be detected in ts AEV-transformed erythroblasts from adult bone marrow when induced to differentiate under the same conditions. In contrast to normal primitive erythrocytes, ts AEV-infected embryonic erythroblasts differentiated in vitro expressed also adult haemoglobin. These results suggest an influence of the haematopoietic environment on the switch from embryonic to adult erythrocytes.     

The effects of body size on mating and reproduction in Brachinus lateralis (Coleoptera: Carabidae)

Abstract. 1. The causes and reproductive consequences of body size variation of Brachinus lateralis Dejean, a parasitic carabid beetle, were investigated.
2. Body size variation occurs within and between sites. Host size has a major influence on body size of the adult.
3. Fecundity is positively correlated with body size. Egg size is not correlated with body size.
4. Mating males tend to be larger than non-mating males. There is a positive correlation of body sizes in mating pairs.
5. Limited opportunity for host choice may maintain size variation despite the advantages of large size.
6. The non-random patterns of mating for a species without obvious intrasexual aggression suggest that subtle means of male-male competition or female choice may be important.     

Priority effects among young‐of‐the‐year fish: reduced growth of bluegill sunfish (Lepomis macrochirus) caused by yellow perch (Perca flavescens)?

1. When available, Daphnia spp. are often preferred by age‐0 yellow perch and bluegill sunfish because of energetic profitability. We hypothesised that predation by age‐0 yellow perch could lead to a midsummer decline (MSD) of Daphnia spp. and that priority effects may favour yellow perch because they hatch before bluegill, allowing them to capitalise on Daphnia spp. prior to bluegill emergence. 2. Data were collected from 2004 to 2010 in Pelican Lake, Nebraska, U.S.A. The lake experienced a prolonged MSD in all but 1 year (2005), generally occurring within the first 2 weeks of June except in 2008 and 2010 when it occurred at the end of June. MSD timing is not solely related to seasonal patterns of age‐0 yellow perch consumption. Nevertheless, when Daphnia spp. biomass was low during 2004 and 2006–2010 (<4 mg wet weight L^?1), predation by age‐0 yellow perch seems to have suppressed Daphnia spp. biomass (i.e. <1.0 mg wet weight L^?1). The exception was 2005 when age‐0 yellow perch were absent. 3. Growth of age‐0 bluegill was significantly faster in 2005, when Daphnia spp. were available in greater densities (>4 mg wet weight L^?1) compared with the other years (<0.2 mg wet weight L^?1). 4. We conclude that age‐0 yellow perch are capable of reducing Daphnia biomass prior to the arrival of age‐0 bluegill, ultimately slowing bluegill growth. Thus, priority effects favour age‐0 yellow perch when competing with age‐0 bluegill for Daphnia. However, these effects may be minimised if there is a shorter time between hatching of the two species, higher Daphnia spp. densities or lower age‐0 yellow perch densities.