Influence of plant sulphur nutrition on oviposition and larval performance of the diamondback moth

We measured adult oviposition preference, larval growth, and feeding behaviour of the crucifer specialist Plutella xylostella (L.) (Lepidoptera: Plutellidae) on plants of Brassica napus (L.) cv. Express (Brassicaceae), grown under three different sulphur regimes. The nutrient solutions used were the following: one sulphur‐free (S₀), one normal sulphur (S_n, normal field concentration), and one sulphur‐rich (S₊, double concentration of S_n). Females laid more eggs on S_n than on S₀ plants, while only a slight, non‐significant difference was observed between S_n and S₊ plants. Moreover, the development time from hatching to emergence was significantly shorter, and adults were heavier on S_n than on S₀ plants. Comparing these same two parameters from S_n and S₊ plants, we found a shorter development time on plants rich in sulphur, although this trend was not statistically significant. Larval feeding preferences were tested in a dual choice assay using leaf discs. A significantly higher number of larvae preferred leaf discs of S_n plants than those of S₀ plants. Furthermore, the larvae preferred S₊ to S_n discs. An optimal supply of sulphur to oilseed rape is necessary for a good seed harvest, and it also plays an important role in acceptance by P. xylostella of the host plant. Maintaining higher levels of sulphur in the plant nutrient solution benefits insect performance, both at the adult and larval stage.     

Reproductive biology of the microtype tachinid fly Zenillia dolosa (Meigen) (Diptera: Tachinidae)

Reproductive biology including mating, adult longevity, fecundity and development of the tachinid fly Zenillia dolosa was investigated for optimizing rearing procedures using Mythimna separata as a host in the laboratory. Females lay microtype eggs containing a first instar larva on food plants of the host and then the eggs must be ingested by the host for parasitization. Mating success was 58.5% with mating duration of 80.7 min. Mating was most successful when day 0–1 females were kept with day 2–4 male flies. Female body size was positively correlated with its fecundity but not with longevity. However, females that survived longer produced more eggs during their lifetime. Parasitoids successfully developed in 4th to 6th instar host larvae. Host instars at the time of parasitoid egg ingestion significantly influenced development time of the immature parasitoid, but did not affect body size of the emerging parasitoid. We suggest that pairing newly emerged females with day 2–4 males should result in higher mating success and using the last instar hosts for parasitization should minimize development time of the parasitoid for rearing.     

Reproductive biology of the electric lanternfish Electrona risso (Myctophidae) and the bigscale fishes Melamphaes polylepis and Scopelogadus mizolepis (Melamphaidae)

This study was the first to investigate the key reproductive traits of the electric lantern fish Electrona risso (Myctophidae, n = 918) and the bigscale fishes (Melamphaidae) Melamphaes polylepis (n = 260) and Scopelogadus mizolepis (n = 649). Specimens of these mesopelagic species were collected in March and April 2015 in the eastern Central Atlantic (0–24° N, 20–26° W). Sex ratio was not significantly different from 1:1 in E. risso and M. polylepis but significantly skewed toward female dominance in S. mizolepis. Reproductive phases were determined macroscopically and by histological analyses on selected individuals. Female length at 50% maturity (L₅₀) was 55.1 mm standard length (L_S) in E. risso, with an observed female maximum length (L_max) of 81.2 mm L_S. M. polylepis females had an L₅₀ of 40.2 mm L_S and an L_max of 86.7 mm L_S. S. mizolepis had an L₅₀ of 46 mm L_S and an L_max of 97.9 mm L_S. The three species show histological features of iteroparity, but the E. risso population appears to occur in two year-classes and experience only one spawning season per lifetime in the study region. All three species are batch-spawners. A batch fecundity of 2668 eggs was estimated from one E. risso individual, with a relative batch fecundity of 369 eggs g⁻¹ gonad-free body mass. M. polylepis had a batch fecundity of 1027 eggs and a relative batch fecundity of 149 eggs g⁻¹ (n = 3). S. polylepis had a batch fecundity of 1545 eggs and a relative batch fecundity of 215 eggs g⁻¹ (n = 21). The median gonado-somatic index during the actively spawning phase of E. risso was 4.5, significantly lower than that of M. polylepis (7.5) and S. mizolepis (7.1). No regressing or regenerating phases were observed in this study. Batch-spawning in all three species is suggested to be advantageous to cope with intra-annual variability in food supply and other risks for offspring survival. With what appears to be in effect a (facultative) semelparous strategy in combination with a short life span in E. risso, interannual differences would have a great effect on population dynamics of this species. Knowledge is still lacking on temporal aspects of reproduction such as the duration of the spawning season and the frequency of spawning, as well as age and growth.     

Life history of the symbiotically luminous cardinalfish Siphamia tubifer (Perciformes: Apogonidae)

Characteristics of the life history of the coral reef‐dwelling cardinalfish Siphamia tubifer, from Okinawa, Japan, were defined. A paternal mouthbrooder, S. tubifer, is unusual in forming a bioluminescent symbiosis with Photobacterium mandapamensis. The examined S. tubifer (n = 1273) ranged in size from 9·5 to 43·5 mm standard length (L_S), and the minimum size at sexual maturity was 22 mm L_S. The number of S. tubifer associated during the day among the spines of host urchins was 22·9 ± 16·1 (mean ± s.d .; Diadema setosum) and 3·6 ± 3·2 (Echinothrix calamaris). Diet consisted primarily of crustacean zooplankton. Batch fecundity (number of eggs; F_B) was related to L_S by the equations: males (fertilized eggs) F_B = 27·5L_S ? 189·46; females (eggs) F_B = 31·3L_S ? 392·63. Individual mass (M; g) as a function of L_S was described by the equation: . Growth, determined from otolith microstructure analysis, was described with the von Bertalanffy growth function with the following coefficients: L_∞ = 40·8 mm L_S, K = 0·026 day^?1 and t₀ = 23·25 days. Planktonic larval duration was estimated to be 30 days. The age of the oldest examined individual was 240 days. The light organ of S. tubifer, which harbours the symbiotic population of P. mandapamensis, increased linearly in diameter as S. tubifer L_S increased, and the bacterial population increased logarithmically with S. tubifer L_S. These characteristics indicate that once settled, S. tubifer grows quickly, reproduces early and typically survives much less than 1 year in Okinawa. These characteristics are generally similar to other small reef fishes but they indicate that S. tubifer experiences higher mortality.     

Size‐dependent reproductive success of wild zebrafish Danio rerio in the laboratory

Size‐dependent reproductive success of wild zebrafish Danio rerio was studied under controlled conditions in the laboratory to further understand the influence of spawner body size on reproductive output and egg and larval traits. Three different spawner size categories attained by size‐selective harvesting of the F₁‐offspring of wild D. rerio were established and their reproductive performance compared during a 5 day period. As to be expected, large females spawned more frequently and had significantly greater clutch sizes than small females. Contrary to expectations, small females produced larger eggs when measured as egg diameter with similar amounts of yolk compared to eggs spawned by large spawners. Eggs from small fish, however, suffered from higher egg mortality than the eggs of large individuals. Embryos from small‐sized spawners also hatched later than offspring from eggs laid by large females. Larval standard length (L_S)‐at‐hatch did not differ between the size categories, but the offspring of the large fish had significantly larger area‐at‐hatch and greater yolk‐sac volume indicating better condition. Offspring growth rates were generally similar between offspring from all size categories, but they were significantly higher for offspring spawned by small females in terms of L_S between days 60 and 90 post‐fertilization. Despite temporarily higher growth rates among the small fish offspring, the smaller energy reserves at hatching translated into lower condition later in ontogeny. It appeared that the influence of spawner body size on egg and larval traits was relatively pronounced early in development and seemed to remain in terms of condition, but not in growth, after the onset of exogenous feeding. Further studies are needed to explore the mechanisms behind the differences in offspring quality between large‐ and small‐sized spawners by disentangling size‐dependent maternal and paternal effects on reproductive variables in D. rerio.     

Influence of prey on developmental performance, reproduction and prey consumption of Neoseiulus californicus (Acari: Phytoseiidae)

The Spical strain of the predatory mite Neoseiulus californicus (McGregor) is used as a biological control agent, but little is known about its preferred prey and host plants in Japan. Here we studied the development, reproduction and prey consumption of the Spical strain when fed on eggs of five different spider mite species deposited on both their laboratory-rearing plant and cherry, on which all five spider mite species developed well. The developmental periods of immature N. californicus females and males were significantly affected by the prey species they fed on, but not by the plants. No difference was found between males and females. The developmental period was shorter on eggs of two Tetranychus species than on eggs of Panonychus ulmi. Immature females had a higher predation rate than immature males. Preoviposition period, oviposition period and the number of eggs laid per female were not significantly affected by either the plants or the type of prey eggs. The postoviposition period and total adult longevity were shorter on eggs of P. ulmi than of the other four prey species, but there was no effect of plant substrate. The postoviposition period of the Spical strain was much longer than that of other N. californicus strains or other predatory mite species: the postoviposition period of the Spical strain was more than three times longer than the oviposition period, accounting for more than 75% of the total adult longevity. This suggests that the females need multiple mating to reach full egg load, but this remains to be tested. Total consumption by N. californicus adults was lower for eggs of P. ulmi than for eggs of the other four species, apparently because of the shorter postoviposition period when fed on eggs of P. ulmi. The intrinsic rates of natural increase (r _m) on the rearing plant did not differ among prey species, whereas those on cherry were significantly different: the value was higher on Tetranychus urticae eggs than on eggs of other species. Only when N. californicus fed on T. urticae eggs, the r _m-values were significantly different between the rearing plant and cherry (higher on cherry). Thus, the Spical strain of N. californicus could feed on eggs of all five spider mite species, deposited on a variety of plants with similar r _m-values, suggesting that it could be successfully used to control spider mites in orchards and various crop fields of Japan.     

Life‐history characteristics of the large Amazonian migratory catfish Brachyplatystoma rousseauxii in the Iquitos region,Peru

The main life‐history traits of the dorado Brachyplatystoma rousseauxii, a large Amazonian catfish undertaking the largest migration known for a freshwater fish species (from the nursery area in the estuary of the Amazon to the breeding zones in the head waters of the western Amazon basin close to the Andes), were determined from a 5 year sampling of >15 000 specimens in the Peruvian Amazon. The breeding season occurred during the falling and low‐water periods, which is hypothesized to be an adaptation to maximize the chances of young stages to reach the estuary. The size at first sexual maturity was slightly larger for females than males, c. 91 and 83 cm standard length (L_S), respectively. Both males and females reproduce for the first time at >3 years old. The fecundity per spawning event ranged from 481 734 to 1 045 284 oocytes for females weighing 25 and 34 kg, respectively. Seasonal variations of body condition were similar among sexes, but differed between immature specimens that had a higher condition during the low‐water period and lower condition during rising waters, and mature individuals that showed the opposite pattern. The growth characteristics were estimated by L_S frequency analysis. For females, the best fitting models gave a mean birth date in August, during the height of the breeding cycle, with the following von Bertalanffy growth function parameters: L_S∞ = 153·3, K = 0·29 and t₀ =– 0·37 years. For males, the best fitting model gave a mean birth date in July, also during the height of the breeding period, with L_S∞ = 142, K = 0·30 and t₀ =– 0·36 years. At a given age, females were systematically larger than males and the size difference increased with age. The largest females sampled (148 cm L_S) was 11 years old and the largest male (134 cm L_S) was 9 years old. The mortality estimates were higher for males total (Z) = 1·34, natural (M) = 0·52 and fishing (F) = 0·82 than for females (Z = 0·98, M = 0·50, F = 0·48). The life‐history patterns of B. rousseauxii are discussed in light of the available knowledge about this species and the understanding of its complex life cycle.     

Sensory interaction during trap-finding by female onion flies: implications for ovipositional host-plant finding

Using various three-dimensional traps alone and in combination with the onion volatile, dipropyl-disulphide (Pr₂S₂), we found that visual behaviour of female onion flies, Delia antiqua (Meigen), varied with the visual context (background composition and trap spacing) in which traps were presented and the females' reproductive state (mated vs. unmated). Against a background of real onions, females alighted more frequently on spherical than cylindrical traps, and white than green spheres, but females responded equally to white and green cylinders. In an onion field, baiting traps with Pr₂S₂ significantly increased female response to white over green traps, but had no influence on their response to trap shape. When traps were spaced 10 m apart and against a background of bare soil, females orienting to Pr₂S₂ baits alighted more frequently on vertical than horizontal traps, but shape and spectral reflectance were insignificant. However, when traps were spaced 0.25 m apart, females orienting to Pr₂S₂ baits alighted more frequently on cylinders than spheres. Mated females alighted more frequently on green than white cylinders, but unmated females responded to cylinders independent of spectral reflectance. When located 20 m downwind from Pr₂S₂ baits, mated females alighted on green cylinders significantly more often than unmated females. Response to traps mimicking onion plants suggests that ovipositional host-finding in female onion flies is dominated by olfactory responses at long range (several metres) and by visual cues at short-range (ca. 1 m). The view that host location by female onion flies is a hierarchical response pattern mediated by multiple sensory modalities and modified by resource level (habitat) and reproductive status, is discussed.     

Photosynthesis and photosystem 2 efficiency of two salt-adapted halophytic seashore <Emphasis Type="Italic">Cakile maritima</Emphasis> ecotypes

The effects of salinity (0–400 mM NaCl, marked S₀, S₁₀₀, S₂₀₀, and S₄₀₀) on growth, photosynthesis, photosystem 2 (PS2) efficiency, ion relations, and pigment contents were studied in two seashore Cakile maritima ecotypes (Tabarka and Jerba, respectively, sampled from humid and arid bioclimatic areas). Growth of Jerba plants was improved at S₁₀₀ as compared to S₀. Tabarka growth was inhibited by salinity at all NaCl concentrations. Leaf sodium and chloride concentrations increased with medium salinity and were higher in Jerba than in Tabarka plants. Chlorophyll content, net photosynthetic rate, stomatal conductance (g _s), and intracellular CO₂ concentration were stimulated at moderate salinity (S₁₀₀) in Jerba plants and inhibited at higher salt concentrations in both ecotypes: g _s was the most reduced parameter. The maximum quantum efficiency of PS2 (F_v/F_m), quantum yield, linear electron transport rate, and efficiency of excitation energy capture by open PS2 reaction centres showed no significant changes with increasing salt concentration in Jerba plant and were decreased in Tabarka subjected to S₄₀₀. However, the efficiency of dissipation of excess photon energy in the PS2 antenna was maintained in Jerba and was increased in Tabarka plants challenged with S₄₀₀. Hence the relative salt tolerance of Jerba was associated with a better ability to use Na⁺ and Cl⁻ for osmotic adjustment, the absence of pigment degradation, and the concomitant PS2 protection from photodamage.     

Sex differences in metabolic rates in field crickets and their dipteran parasitoids

Sex differences in metabolic rate (MR) can result from dimorphism in the performance of energetically demanding activities. Male crickets (Teleogryllus oceanicus) engage in costly calling and aggressive activity not performed by females. Consistent with this difference, we found higher maximal MR, factorial scope, and fat content in males than females. T. oceanicus song is also costly because it attracts the parasitoid fly Ormia ochracea. Parasitized crickets had reduced maximal MR consistent with a metabolic cost to harboring larvae. This cost was greater for females, either because females invest more heavily into reproduction at the expense of metabolic capacity, or because males are under stronger selection to respond to infection. Little is known about O. ochracea outside of its auditory system and parasitic lifestyle. We observed greater resting MR in male flies, possibly reflecting a sex difference in the requirement for metabolic power output, because male flies perform potentially costly mating behavior not seen in females. We found a positive relationship between larval density within a cricket and pupal resting MR, suggesting that crickets in good condition are able to both harbor more larvae and produce larvae with higher resting MR. These results reveal a complex interplay between the metabolism of crickets and their fly parasitoids.Communicated by G. Heldmaier     

Comparative study of the molting cycle of wild and reared swimming crabs Callinectes danae (Crustacea: Portunidae)

Specimens of Callinectes danae Smith 1869 were caught in northeastern Brazil (2178 males, 2031 females); of these, 24 males and 24 females were reared for 6 months. Water temperature (T) and salinity (S) showed a significant effect on the average ecdysis in wild crab (μ), with a model obtained that was: μ = exp(?0.12268T + 0.06148S)/(1 + exp(?0.12268T + 0.06148S)). Size at morphometric maturity was significantly larger for wild males and females (9.45 and 8.38 cm, respectively) than for reared individuals (8.95 and 7.93 cm). Females of sizes above CW₅₀ (carapace width at maturation) showed an increased ecdysis activity, whereas males showed a decrease in ecdysis frequency in sizes over CW₅₀. Five and six molts were observed for females and males, respectively, in both wild and reared crabs; the modal classes of the reared crabs were shifted to smaller sizes. In reared females the terminal‐pubertal molt occurred at 107 days of age and at 148 days, on average, in males. The intermolt period varied from 8 to 41 days and increased with age.     

Onion fly,Delia antiqua,oviposition and mating as influenced by insect age and dosage of male reproductive tract extract (Diptera: Anthomyiidae)

One hundred percent of virgin female onion flies,Delia antiqua, receiving 1/20 of a male equivalent of an aqueous extract of mature male reproductive tract remained unmated in the presence of males and began laying unfertilized eggs at a normally mated rate of about 20 eggs/female/day. The 50% behavioral response (BR₅₀) fell between 1/40 and 1/20 of a male equivalent. Sex peptide responses are not always all-or-none. Some females receiving extract at 1/40 male equivalent oviposited at an intermediate rate. Moreover, at low sex peptide dosages, some females were fully activated ovipositionally but were receiptive to mating. A low level of sex peptide was present in 1-day-old males. Sex peptide titer rose with age until plateauing by 6 days posteclosion. Males began mating at 3 days, when they first had ample mature sperm; 50% of 6-day-old males mated. The mean number of females inseminated per male exposed to an excess of virgin females over 24 h was 4.3±0.6 (±SE). Presence of mature eggs was not always a prerequisite for mating, although probability of insemination was correlated with egg maturation. One-day-old preovipositional females receiving 1/20 of a male equivalent of extract began ovipositing when they had mature eggs at 5–6 days old. Therefore, sex peptide may act early and permanently or have a long half-life and affect behaviors once females reach sexual maturity. Male flies provide females with an excess of sex peptide in many cases.D. antiqua males transferred ca. 5–10 times more sex peptide than necessary to activate females fully. We suggest this excess is related to the speed of female response. It is yet unclear whether sex peptide potency or titer in Diptera has become exaggerated by intra- or intersexual selection.     

Life history parameters of the microtype parasitoid fly Pales pavida (Diptera: Tachinidae), and effects of host age and number of eggs ingested by host on parasitism success

With the aim of developing better procedures for rearing the microtype tachinid fly Pales pavida (Meigen), we performed ecological studies in the laboratory using the natural host Mythimna separata (Walker), investigating larval development, mating behaviour, individual oviposition patterns and relationships between parasitisation and number of eggs ingested (NEI) per host. The host instar at the time of parasitoid egg ingestion significantly affected the development time of the immature parasitoid: development took longer when the hosts ingested eggs when at the fifth instar than at the sixth (last) instar. There was no difficulty obtaining mated females in the laboratory when day 0–1 female flies were kept with day 2–4 males. Mean lifetime fecundity was 5805?±?568 eggs per female. Daily rates of oviposition by individual females varied widely; the greatest number of eggs laid in a day was exactly 1700. When the NEI by day 1 fifth instars or day 0 or 3 last instars was 1, 3, 6 or 10, the parasitisation percentage tended to increase with increasing NEI, although it did not differ significantly between NEI 6 and 10. Therefore, the percentage adult emergence per egg ingested decreased from NEI 6 to 10, particularly in the case of last instars. Using day 0 last instars, with six eggs ingested per host, should increase parasitisation rates and shorten the development time of the parasitoid for rearing.     

Wise flies: a pre‐dispersal seed predator prefers hermaphrodites over females in the gynodioecious Polemonium foliosissimum

1. Oviposition choices can profoundly affect offspring performance. Oviposition decisions of the dipteran pre‐dispersal seed predator, Hylemya sp. (Diptera: Anthomyiidae), when choosing among sex morphs of their host‐plant—Polemonium foliosissimum Hook—were evaluated. Polemonium foliosissimum is gynodioecious, with female and hermaphrodite sex morphs that differ in flower size. 2. It was asked: Do female flies preferentially oviposit on hermaphrodite plants and, if so, are oviposition choices correlated with flower size? Is larval survivorship higher on hermaphrodite plants and, if so, is larval success correlated with flower size? Can the differences in oviposition and/or larval success be explained by slight differences in flowering phenology between the sexes? 3. Hermaphrodite flowers received 45% more Hylemya eggs than females. Although hermaphrodites had larger petals and sepals than females, egg loads were not correlated with petal or sepal size. Larval survival was 30% greater on hermaphrodites than females and higher on plants with larger sepals. However, the difference in sepal area between genders did not fully explain larval survival differences. Egg numbers declined over weeks, but differences in egg loads between the sex morphs were not attributable to a slight phenological delay of females. Larval survival declined over the season; however, larval survival differences between sex morphs were consistent. 4. Hylemya preferentially oviposited on hermaphrodites where their larvae had a significantly greater survival rate compared with females. The present results add to the knowledge that intra‐specific choices have consequences for phytophagous insects and that the relationship between antagonists and their gynodioecious host plants is complex.     

Toxic effect of deltamethrin on the life table and development of Helicoverpa armigera (Hubner)

Effect of deltamethrin (Decis 2.8% EC) on the fitness of Helicoverpa armigera (Hübner) was determined using demographic studies. Survivorship (I_x) and expectancy (e_x) was high with commencement of age and gradually decreased with progression of age in the exposed and unexposed groups. Highest number of unhatched eggs (~20%) was recorded with LC₅₀ (79.0 mg/L) opposed to 1% in the control. Daily fecundity rate was significantly greater (200 females/day) in the control than 126 in LC₂₀ (5.13 mg/L). Potential fecundity was lowest (179 females/female/generation) with LC₅₀ treatment than 675 in the control. Smallest value of intrinsic rate of increase (r_m) occurred at LC₅₀ (0.0393 females/female/day) while the highest value (0.0539) was at control. Overall larval development was significantly reduced to 18.0 days with LC₅₀ opposed to 24.1 days at control. Pupal period was shortened to 7.6 days with LC₅₀, while it recorded 9.3 days in control.     

Reproductive biology of albacore Thunnus alalunga

Reproductive variables in albacore Thunnus alalunga were evaluated by gonad histology in samples of 132 males (58–118 cm fork length, L_F) and 112 females (59–101 cm L_F) that were collected from the western North Pacific Ocean from 2001 to 2006. In the sex ratio examination, males greatly outnumbered females in large adult fish (L_F > 100 cm). Thunnus alalunga exhibited a protracted spawning period from March to September in the waters off eastern Taiwan and the Philippines, and the peak spawning activity occurred in March and April. Minimum sizes associated with the classification of mature fish were 78 and 83 cm L_F for males and females, respectively. In addition, the largest L_F of immature fish were 93 cm for males and 94 cm for females. The spawning frequency estimate in April was 1·7 days. Batch‐fecundity estimates of 21 females (89–99 cm L_F) ranged between 0·17 and 1·66 million eggs (mean ±s.d . = 0·94 ± 0·43). The relative fecundity estimates of the 21 females ranged between 9·2 and 92·4 oocytes g^?1 body mass (mean ±s.d . = 50·5 ± 22·8). The results presented in this study provide increased information regarding this species' reproductive‐related characteristics than are currently available in stock status determinations.     

Leaf characteristics and gas exchange of the mangrove <Emphasis Type="Italic">Laguncularia racemosa</Emphasis> as affected by salinity

Under constant salinity we analysed the leaf characteristics of Laguncularia racemosa (L.) Gaertn. in combination with gas exchange and carbon isotopic composition to estimate leaf water-use efficiency (WUE) and potential nitrogen-use efficiency (NUE). NaCl was not added to the control plants and the others were maintained at salinities of 15 and 30 ‰ (S₀, S₁₅, and S₃₀, respectively). Leaf succulence, sodium (Na), nitrogen (N), and chlorophyll (Chl) contents increased under salinity. Salinity had a negative impact on net photosynthetic rate (P _N) and stomatal conductance (g _s) at high and moderated irradiances. Potential NUE declined significantly (p<0.05) with salinity by 37 and 58 % at S₁₅ and S₃₀, respectively, compared to S₀ plants. Conversely, compared to S₀ plants, P _N/g _s increased under saline conditions by 12 % (S₁₅) and 50 % (S₃₀). Thus, WUE inferred from P _N/g _s was consistent with salinity improved short-term WUE. Long-term leaf WUE was also enhanced by salinity as suggested by significantly increased leaf δ¹³C with salinity. Improved WUE under salinity explains the eco-physiological success of mangrove species under increasing salinity. Conversely, decline in NUE may pose a problem for L. racemosa under hyper-saline environments regardless of N availability.     

Humidity‐controlled cold storage of Neoseiulus californicus (Acari: Phytoseiidae): effects on male survival and reproductive ability

Humidification can suppress water loss from an organism and has great potential for improving the cold storage of short‐lived arthropods, such as predatory mites. The effectiveness of humidity‐controlled cold storage was recently verified for Neoseiulus californicus (McGregor) females but was not examined for males. Combining both males and females in one storage protocol might increase the predator population because it would enhance the opportunity for multiple mating, which is necessary for females to maximize their egg production. Newly emerged adult males were stored at an air temperature of 5°C and relative humidity (RH) of 100% or 80%. The median survival time (LT₅₀) was 32 days at 100% RH and 14 days at 80% RH; the survival curves differed significantly. Males stored at 100% RH for 0, 10, 20 and 30 days were introduced to virgin females for mating at 25°C to evaluate their reproductive ability. The pre‐oviposition period was significantly prolonged in the females mated with males stored for ≥20 days. No negative effects of storage were observed on the oviposition period, total number of eggs or net reproduction rate (R₀) in the females mated with males stored for ≤20 days or on the mean generation time (T) for those stored for 30 days. A slight decrease in the intrinsic rate of increase (r_m) was observed in the females mated with males stored for ≥20 days. Our storage method can preserve N. californicus males for 20 days with only a minor reduction in their survival and reproductive ability.     

Oviposition deterrent effect of Spodoptera littoralis (Boisd.) larval frass to adult females of two major noctuid insect pests

Water extract of fresh frass of Spodoptera littoralis larval instars (L_1–3, L₄, L₅ and L₆) fed on Castor oil leaves was prepared by soaking at concentration (20?g frass/50?ml distiled water) followed by steering before filtration. Oviposition deterrent activity of the extract to S. littoralis and A. ipsilon adult females was evaluated as the mean number of laid eggs in treatments in comparison with control under laboratory conditions. Total amount of phenols and flavonoids in larval frass was determined. Extraction of L₆ frass obtained complete oviposition deterrent to S. littoralis adult moths and the minimum number of laid eggs by A. ipsilon adult females (11.8?eggs/female) in comparison with control (1026.0 and 848.2?eggs/female respectively). Maximum number of laid eggs by S. littoralis females was 361.0/f at treatment with L_1–3 frass extract and 748.0/adult female of A. ipsilon at treatment with L₄ frass extract. Low amount of phenols and/or flavonoids in frass extract of L₆ increased the oviposition deterrent effect while high amount of them as obtained in L₄ frass extract (3.504 and 1.610%, respectively) decreased the effect at both of tested insects.     

Sexual size dimorphism in anadromous brown trout Salmo trutta

Anadromous trout Salmo trutta exhibits sexual size dimorphism (S_SD); females were larger than males in populations where male mean total length (L_T) at maturity was below 49 cm and females were smaller than males when mean male L_T was above 49 cm, the slope of the regression of female on male L_T was 0·59. In streams with mean annual discharge below 41 m³ s^?1, flow added significantly to a model with S_SD as the dependent variable and male mean L_T at maturity as the first predictor variable. There was a slight increase in S_SD with increasing latitude, which may result from an increase in male size with increasing latitude.