Errors in egg-laying by female Common Cuckoo Cuculus canorus in nests of its common host

Dozens of studies have documented that brood parasites are well adapted to a brood parasitic lifestyle but not all parasitism events are successful. Co-evolution between brood parasites and their hosts is a dynamic process so it is reasonable to expect that a female brood parasite may commit errors during egg deposition by laying her eggs outside the laying period of the host, with consequent impacts on her fitness. Using an extensive dataset from a long-term study, we evaluated egg-laying patterns and errors related to the timing of egg-laying in the Common Cuckoo Cuculus canorus (hereafter ‘Cuckoo’). Specifically, we tested whether the Cuckoo avoids laying before or on the day of host clutch initiation to reduce the risk of rejection of parasitic eggs, whether laying errors will be more frequent in periods with a lack of active host nests, and whether the laying errors will be more frequent in periods with intense Cuckoo parasitism and a consequent lack of suitable host nests. We found that about one-third of Cuckoo eggs were laid on the host clutch initiation day or 1 day before, and the percentage of Cuckoo eggs laid decreased thereafter. Surprisingly, the probability of Cuckoo egg acceptance by the hosts was not affected by the egg-laying stage of the host clutch. Errors in the timing of egg-laying with fatal consequences (i.e. those precluding Cuckoo hatching because of laying in incubated or deserted clutches) were recorded in about 5% of cases. Only laying date of a Cuckoo egg had a significant effect on the probability of errors, which increased during the breeding season. This may be related to the higher number of deserted and incubated host nests at the site at the end of the breeding season. Errors in egg-laying may be attributed to young and inexperienced females but also impaired body condition or intraspecific competition may cause this behaviour. Future studies, which will test these possible explanations, will help to understand better the mechanism of co-evolutionary arms races and differences between host specialist and generalist brood parasites in various host–parasite systems.     

Egg sac damage and previous egg sac production influence truncated parental investment in the wolf spider,Pardosa milvina

Life history theory predicts that iteroparous animals adaptively partition reproductive effort between current and future reproduction. When rearing costs of current offspring exceed the potential benefits, parental care should be terminated and deferred toward future reproduction. We tested two related predictions that follow from life history theory: (a) parents should be sensitive to offspring viability and withhold parental care if offspring survival probability drops and future reproductive opportunities are likely, and (b) parents should be less sensitive to offspring survival probability when future reproduction is unlikely and maximize parental care late in life. The wolf spider, Pardosa milvina, demonstrates extensive parental care; however, they may also abandon or cannibalize their egg sacs. We tested the effects of egg sac damage and production of a previous egg sac on egg sac abandonment and cannibalism decisions. Among four egg sac groups (1st egg sac intact, 1st egg sac damaged, 2nd egg sac intact, 2nd egg sac damaged), we daily monitored egg sac abandonment and cannibalism and measured differences in egg sac searching, protection, and grooming among removed and damaged egg sacs (N = 116 with 1st egg sac and 88 with 2nd egg sac). Females with first egg sacs abandoned and cannibalized damaged egg sacs significantly more compared to unmanipulated egg sacs; however, females with second egg sacs were insensitive to egg sac damage. Females also spent significantly more time protecting second egg sacs compared to first egg sacs and groomed damaged egg sacs significantly more than undamaged. These results support the general predictions of life history theory that indicate that abandonment and cannibalism should decrease with diminished future reproductive potential and that parents should be less sensitive to indicators of offspring survival probability late in life.     

The early life history of two sympatric New Zealand octopuses: eggs and paralarvae of Octopus huttoni and Pinnoctopus cordiformis

This study combined morphological and morphometric information on egg clutches, egg capsules and paralarvae of two sympatric coastal octopuses from New Zealand waters, Octopus huttoni and Pinnoctopus cordiformis, to provide species-specific traits to identify their early life stages obtained from field surveys. Eggs of O. huttoni (2.5 mm length; 1 mm width) were entwined with one another forming strings that ranged from 11 to 25.8 mm in length. Eggs of P. cordiformis (6.4 mm length; 1.5 mm width) were significantly bigger than those of O. huttoni and were grouped in small clusters of about seven eggs. Paralarvae O. huttoni and P. cordiformis differed in hatching size (1.4 mm versus 3.1 mm mantle length), number of suckers per arm (four versus eight), number of lamellae per outer demibranch (five versus ten) and arrangements of chromatophores in the body surface (29 to 59 versus 91 to 179), respectively. The morphological traits described in hatchlings from the laboratory allowed comparisons with field-collected paralarvae, suggesting that such characters were reliable species-specific patterns to enable a consistent differentiation between the early life stages of these two sympatric species, even in the absence of the brooding female.     

The breeding biology of Bennett's wallaby (Macropus rufogriseus jruticus) in South Canterbury,New Zealand

Abstract

The lipid and amino acid composition of the egg contents of captive dwarf cassowary (Casuarius bennetti) was investigated. Although the proportions of triacylglycerol (65%) and phospholipids (27%) were similar to those found in domestic hen eggs, the fatty acid content of the lipids was different. Egg lipids contained less than 2% linoleic acid and this is probably inadequate for chick development. An oil of high linoleic acid content — such as com oil — as a supplement to the maternal diet could improve the breeding success of these birds in captivity.     

Leaf hoppers of New Zealand: Subfamilies Aphrodinae,Jassinae, Xestocephalinae,Idiocerinae, and Macropsinae (Homoptera: Cicadellidae)

The cosmopolitan subfamilies Aphrodinae, Jassinae, Xestocephalinae, Idiocerinae, and Macropsinae are diagnosed and the New Zealand species described and illustrated. Each subfamily is represented in New Zealand by only one or two species, those in Idiocerinae having been introduced from Europe or North America. The species Euacanthella brunnea Evans (Aphrodinae) is synonymised with the Australian species E. insularis Evans (new synonymy).     

Exopeptidase activity in eggs of Trichostrongylus colubriformis (Nematoda)

Summary

A supernatant from eggs of the ruminant nematode Trichostrongylus colubriformis contained an enzyme that was similar to leucine aminopeptidase (LAP), based on hydrolysis of the substrate L-leucine β-naphthylamide to β-naphthylamine. A Michaelis-Menten constant (K _m) of 0.155 mM was obtained. Rate of hydrolysis of 16 substrates revealed that L-phenylalanine and L-tyrosine β-naphthylamides were hydrolyzed most readily while seven additional substrates were hydrolyzed at lesser rates. The optimum pH for enzymatic activity was 6.75–7.5. Enzymatic activity was lost by heating the egg supernatant to 60°C for 5 min or freezing at 0°C for 28 days. Addition of millimolar concentrations of the chlorides of zinc, manganese and magnesium to the egg supernatant had no stimulatory effect on enzyme activity while 10 and 100 mM concentrations significantly reduced activity. Ethylenediamine tetraacetic acid at 10^?4 M had no effect on enzymatic activity. Activity was inhibited by 10^?4 M 1,10-phenanthroline, but the inhibition was reversed by zinc chloride at 10^?3 M. Di-isopropylphosphofluoridate at 10^?3 M reduced enzymatic activity moderately. Enzyme activity in egg supernatant increased 2.2-fold from 21 days to 60–90 days of a primary infection in the host while a 3.3-fold increase was found in primary versus secondary infections.     

Reproductive system morphology of Lightiella magdalenina (Crustacea,Cephalocarida): functional and adaptive implications

The reproductive systems of adults and larvae of Lightiella magdalenina were examined. Lightiella magdalenina, similar to the best-known cephalocarida species Hutchinsoniella macracantha, is a simultaneous hermaphrodite. Although the morphology of their reproductive system is similar, L. magdalenina differs from H. macracantha in exhibiting reduced fecundity: it lays one egg, not two, per reproductive event. This is due to asynchronous development of the oocytes inside the paired female reproductive structures, which determines the maturation of a single egg at a time. The reduced fecundity of L. magdalenina could be offset by the precocious release of oocytes from the germarium, which begins the vitellogenetic process during the last larval stages. Due to this process, after their last moult, reproductive adults can have a large number of advanced vitellogenic oocytes, reducing the time required for their maturation. A possible adaptive relationship between the halved fecundity with pre- and post-hatching parental care is discussed.     

A note on pterosaur nesting behavior

Based on examination of eggshell structure and predicted vapor conductances in eggshells in recently described material from Argentina and China we conclude that pterosaurs buried their eggs. Egg-burying imposes theoretical restrictions on the distribution of pterosaurs, both geographically and spatially, raises the possibility of thermal sex determination and supports previous suggestions that they exhibited nesting fidelity. Some features associated with egg-burying, such as weight savings, are likely to have been fortuitous pre-adaptations for these flying reptiles, but others may have disadvantaged them relative to avian competitors or increased their vulnerability to extinction in a cooling climate.     

食品级惰性粉对三种储藏物害虫生长发育的影响

应用粉剂药膜法,一种食品级惰性粉——4号粉相应剂量处理赤拟谷盗Tribolium castaneum(Herbst)、烟草甲Lasioderma serricorne(Fabricius)、锯谷盗Oryzaephilus surinamensis(Linnaeus)的卵和1龄幼虫,赤拟谷盗、锯谷盗、烟草甲的卵平均孵化率均在97%以上,处理后卵孵化的1龄幼虫平均死亡率均在96%以上;处理3种害虫的1龄幼虫其平均死亡率均在99%以上。结果表明食品级惰性粉对3种试虫卵的孵化率几乎没有影响,但对其1龄幼虫有较好的防治效果。通过混粮法应用正交试验研究发现,惰性粉剂量和小麦含水量对赤拟谷盗F1代防治效果均有显著影响。当小麦处于安全水分时(含水量12%¹4%),10014%),100¹50 mg/kg 4号粉能有效防治赤拟谷盗F1代。