How costly is clutch formation in the Audouin's Gull Larus audouinii?

During the Audouin's Gull's breeding season at the Ebro Delta in 1993, 24 fresh eggs from eight three-egg clutches (modal clutch-size) were collected at the peak of the laying period. Eggs were processed to obtain formalin-fixed yolks, which were halved and stained using the potassium dichromate method. Digitized images of the yolks were examined to assess the daily rates of yolk deposition. We used these data in combination with egg compositional analysis to build a model of energy demands during the formation of an average clutch in Audouin's Gull. To show how the different parameters of clutch formation affect the daily energy investment peak, we performed a simulation analysis in which the rapid yolk development (RYD) period, the follicle triggering interval (FTI), the laying interval (LI) and the albumen synthesis period (ASP) were allowed to vary simultaneously. In our sample, the mean RYD period was seven days with a range from six to eight days. There were no significant differences in yolk volume among eggs in a clutch, but albumen volume was significantly smaller in third eggs. According to our model the albumen synthesis of the a-egg coincides with the energy demand peak for clutch formation. This peak represents an increase by ca. 42% in female energy requirements. Values obtained from the simulation analysis showed that only the ASP of the a-egg and the RYD durations of the second and third follicles produced noticeable reductions in peak energy investment. We predict that in gulls, whose laying intervals seem to be kept constant, significant increases of the durations of the RYD periods of second and third eggs, or even significant reductions of yolk size of these eggs, may operate simultaneously to match the energy demands during clutch formation to the prevailing food conditions.     

柳蓝叶甲的生物学特性室内观察

在实验室条件下(27±0.5℃,12 D:12 L)研究了柳蓝叶甲Plagiodera versicolora的生物学特性。结果表明,幼虫每隔2~3 d蜕皮1次,共蜕皮2次。成虫产卵前期4 d,世代周期17 d。产卵具有一定的周期性,约10 d为1个周期。叶龄对幼虫的生长发育和成虫的产卵行为有极显著的影响。当幼虫以成熟叶为食料时,其生长发育速率明显减慢,各龄期延长,蛹重较轻;成虫以成熟叶或老叶为食料时产卵几乎完全被抑制,而以幼叶为食料时几乎每天均能产卵。此外,柳蓝叶甲产出卵表面化合物对产卵行为有极为显著的影响。卵表面的有机提取物对成虫产卵具有显著的引诱作用;相反,卵表面的水提取物对产卵有一定的驱避作用。     

Reproduction of three eulophid wasps that parasitise larvae of the citrus leafminer

The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) (CLM), is a citrus pest indigenous to Southeast Asia. It was discovered in Israel in 1994. The pest attacks the young foliage of citrus, and damage is caused by the larvae tunnelling under the epidermis of young leaves, leading to foliage destruction. The present study documents basic biological parameters of three exotic eulophid wasps in the laboratory: Semielacher petiolatus, Quadrastichus citrella and Teleopterus sp. S. petiolatus females preferred to lay eggs in the 3rd larval instar of CLM, but did not lay eggs in the 1st instar. Its development ranged from 9 to 14 days. Female longevity was 30.2±5.9 days, its daily oviposition was 12.16±0.68 eggs/day, the total number of eggs oviposited per female was 278.9±74.1, and the number of CLM larvae parasitised was 260.0±68.3. Q. citrella preferred to lay in the 3rd and 4th instar larvae, but not in the 1st instar, its development ranged from 9 to 14 days, female longevity was 40.6±1.9 days, oviposition came to 8.3±0.6 eggs/day, the total number of eggs oviposited was 281.3±64.9/female and the number of parasitised CLM larvae was 276.5±63.7. Teleopterus sp. preferred to lay eggs in the 3rd larval instar, its development required 11–17 days, female longevity was 28.7±3.8 days, its daily number of offspring was 5.2±0.38 offspring/day and with emergence of 138.9±27.7 offspring/female. This knowledge enabled us to maintain high quality cultures for their releases in Israel.     

Assessment of lighting needs by W-36 laying hens via preference test

Light intensity, spectrum and pattern may affect laying hen behaviors and production performance. However, requirements of these lighting parameters from the hens’ standpoint are not fully understood. This study was conducted to investigate hens’ needs for light intensity and circadian rhythm using a light tunnel with five identical compartments each at a different fluorescent light intensity of <1, 5, 15, 30 or 100 lux. The hens were able to move freely among the respective compartments. A group of four W-36 laying hens (23 to 30 weeks of age) were tested each time, and six groups or replicates were conducted. Behaviors of the hens were continuously recorded, yielding data on daily time spent, daily feed intake, daily feeding time, and eggs laid under each light intensity and daily inter-compartment movement. The results show that the hens generally spent more time in lower light intensities. Specifically, the hens spent 6.4 h (45.4%) at 5 lux, 3.0 h (22.1%) at 15 lux, 3.1 h (22.2%) at 30 lux and 1.5 h (10.3%) at 100 lux under light condition; and an accumulation of 10.0 h in darkness (<1 lux) per day. The 10-h dark period was distributed intermittently throughout the day, averaging 25.0±0.4 min per hour. This hourly light-dark rhythm differs from the typical commercial practice of providing continuous dark period for certain part of the day (e.g. 8 h at night). Distributions of daily feed intake (87.3 g/hen) among the different light conditions mirrored the trend of time spent in the respective light intensity, that is, highest at 5 lux (28.4 g/hen, 32.5% daily total) and lowest at 100 lux (5.8 g/hen, 6.7%). Hen-day egg production rate was 96.0%. Most of the eggs were laid in <1 lux (61.9% of total) which was significantly higher than under other light intensities (P<0.05). Findings from this study offer insights into preference of fluorescent light intensity by the laying hens. Further studies to assess or verify welfare and performance responses of the hens to the preferred lighting conditions and rhythm over extended periods are recommended.     

Individual quality and food availability determine yolk and egg mass and egg composition in tree swallows Tachycineta bicolor

Variation in egg size and composition can have important consequences for the quality of offspring. We investigated the factors influencing the yolk mass and egg mass of tree swallows breeding in Ithaca, NY. Using a nondestructive technique to estimate yolk mass via standardized digital-candler photographs, we compared yolk size and egg size of tree swallows Tachycineta bicolor in response to variation in food availability and individual quality. Insect availability one to three days prior to laying, but not four to six days, predicted yolk mass, while insect availability two to three days prior to laying predicted total egg mass. This suggests that, while eggs are formed over longer periods, food availability closer to time of laying has the greatest influence on egg size. These results were supported by collected eggs, as yolk rings revealed that tree swallow eggs are formed over 5–6 days. There was an influence of female quality as well, with early laying birds, independent of food availability, laying larger eggs. Eggs laid later in the laying sequence had larger yolks and greater egg mass. Overall, variation in egg quality appears to be due to a combination of environmental conditions, reflected in food resources, individual quality, and allocation tradeoffs during the laying period.     

Biology ofMicroplitis mediator [Hym.: Braconidae] a gregarious endoparasite ofAgrotis segetum [Lep.: Noctuidae]

Microplitis mediator (Haliday) a gregarious endoparasite was recorded for the first time fromAgrotis segetum (Schiff) in Ankara, Turkey. The female parasites found their hosts by responding to the faeces of the caterpillars. An average, females laid 15.5±1.6 eggs in the bodies of their hosts. The newly laid eggs were elongated, oval in shape and 0.23±0.004 mm long and 0.07 mm wide. They hatched in 5, 4 and 3 days at 20±2°C, 25±2°C and 30±2°C respectively when maintained at 60–70% R.H. and 14∶10 light∶dark regime. At the same temperatures, the larval stage lasted for 24.9±0.6, 18.2±0.4 and 17.1±0.5 days respectively. The prepupal stage was completed in 2 days at 25±2°C, whereas the prepupal and pupal (cocoon) stage lasted 10.9±0.2, 7.0±0.1 and 6.2±0.1 days respectively at the temperatures mentioned above. The adults started mating and feeding shortly after emergence. Female parasites started laying after one day, 7–11 hours and 5–7 hours at the temperatures stated above. At these temperatures females lived for 10.8±0.2, 5.4±0.1, 4.6±0.1 days and laid on average 556, 484 and 363 eggs respectively, whereas the males survived 10.5±0.3, 4.7±0.1 and 4.4±0.1 days respectively.      

Mate provisioning, nutritional requirements for egg production, and primary reproductive effort of female Common Terns Sterna hirundo

We assessed the nutritional importance of mate provisioning to females during egg production and its effects on clutch parameters (egg size, length of the laying period) in Common Terns Sterna hirundo: (1) we estimated the costs of egg production by modeling the daily protein, lipid, and energy requirements of laying females, and (2) compared these costs to both the amount, and the timing, of the male's contribution via mate provisioning. Net lipid, net protein, and gross energy requirements for a three‐egg clutch were estimated to be 5.4 g, 8.6 g, and 569 kJ respectively. Peak protein and lipid requirements occurred one (day ?1) and two (day ?2) days before laying, respectively. Peak energy requirement occurred on day ?1; a cost of 127% to 157% above maintenance. Variation in male provisioning effort (in terms of energy and nutrients delivered) paralleled variation in predicted female requirements for egg production at the level of individual pairs. Males delivered protein in excess of the female's requirements on all days investigated. Male lipid delivery accounted for 45% of female net requirement on the day when demand was greatest (day ?2), but exceeded requirements on all other days. However, the proportion of the female's total energy budget (egg production, maintenance, and activity costs) that was supplied by her mate rose from an average of 29% on day ?2 to 76% during the interval between second and third eggs. Paradoxically, females that were fed at higher rates during the interval between first and second eggs produced clutches with lower total volumes, smaller last‐laid eggs, and clutches with a greater egg‐size hierarchy than conspecifics receiving less food from their mates. Also, females fed at higher rates during the interval between second and third eggs took longer to produce their clutch. These negative relationships between mate provisioning and clutch parameters contrast with previous studies in this and other species.     

Curcumin addition in diet of laying hens under cold stress has antioxidant and antimicrobial effects and improves bird health and egg quality

Curcumin is an herbal component with several biological properties, and we highlight here the thermal stability, antioxidant and anti-inflammatory activity. We determined whether curcumin supplementation in the diets of laying hens under cold stress and naturally infected with Escherichia coli would control infection, and would have positive effects on overall health, as well as egg production and quality. We allocated 36 chickens that had been naturally infected with E. coli into two groups, with six replicates and three chickens per repetition: control group and curcumin group (200 mg curcumin/kg). The experimental period lasted 42 days, and fecal, blood and egg samples were collected at 1, 21 and 42 days We found that feces and eggs had lower total bacterial counts, E. coli counts and total coliform counts in the curcumin group at 21 and 42 days. In fresh eggs, the brightness and yellow intensity (b+) were significantly higher in the curcumin group. In stored eggs, higher specific gravity, albumen height and lower yolk pH were observed in the curcumin group. Fresh eggs collected and stored on day 42 showed lower levels of lipid peroxidation in the curcumin group, while the total antioxidant capacity in the stored eggs was significantly higher in the curcumin group. The curcumin group showed lower total leukocyte counts as a result of lower numbers of neutrophils and lymphocytes, as well as lower levels of total protein, alkaline phosphatase and alanine aminotransferase. Lower serum lipoperoxidation at 42 days was observed in the curcumin group, probably because of the higher activity of glutathione peroxidase and glutathione transferase in other words, because of antioxidant stimulation. Taken together, our findings suggest that curcumin supplementation in laying hens under cold stress and with colibacillosis has positive effects on infection control because of antioxidant stimulation.     

The effect of light exposure on buoyancy of halibut eggs

Effects of light-exposure on eggs of the Atlantic halibut ( Hippoglossus hippoglossus ) were investigated. Egg buoyancy, yolk sac osmolality and perivitelline space (PVS) in light and dark-exposed eggs were followed during 3–12 days after fertilization. In light-exposed eggs, the density increased to a maximum at day 6 while the density in dark exposed eggs significantly decreased between day 4 and 10. There was no significant difference between treatments at day 12. The pattern of yolk osmolality reflected these changes in density. Embryonic volume, calculated from estimates of total volume and PVS, was found to decrease rapidly at days 3–4 after fertilization in the light exposed group, whereas the control group during the same period showed no change. After this period, the embryonic volume showed a parallel decrease in both groups. The increased egg density is caused by both the loss of water from the embryonic compartment and by increased yolk osmolality. These results are discussed in relation to changes in vertical distribution in both natural and culture systems.     

The Incorporation of Orally Administered Radioiodine Into Hens’ Eggs and Follicles

Incorporation of radioiodine into eggs and follicles was studied by oral administration of I131 to hens. With the single dose administration of I131 the shell, including the shell membranes, reached a maximal concentration of 0.017 % of the given amount per g of shell in eggs laid within one day after administration. The white reached a maximal concentration of 0.01 % per g in eggs laid about one day after administration. The subsequent reduction in concentration both in the shell and white from later laid eggs showed a rapid course. In the yolk, radioiodine began to appear in eggs laid about one day after administration. A maximal concentration of 2.78 % of the given amount per yolk was reached in eggs laid about five days after administration. The subsequent reduction in concentration could be followed in the yolk from eggs laid up to and including the ninth day after administration; then the concentration was about 1/50 of the maximal concentration. With continuous administration of I131 once daily for 16 days, the concentration in the shell and white was in the same amount as corresponding maximal concentration in single dose administration as long as the daily supply continued. Following cessation of administration, the concentration decreased in the shell and white with a course simliar to that obtained in the single dose administration. In the yolk, the concentration increased in eggs laid up to and including the ninth day after commencement of the continuous dosing; thereafter, the equilibrium remained as long as the administration continued. About 13 % of the daily given dose of I131 was recovered per yolk. After discontinuation of administration, an obvious concentration reduction was first obtained in the yolks from eggs laid five days later. A calculation of the results for the yolks from the single dose administration to be valid for the daily continuous dosing showed good agreement with the results obtained in the present multiple dose experiments. The follicular uptake of I131 in single dose administration was rapid, with the greatest uptake by the follicle which was in the most rapid phase of growth at the time of administration. During autoradiography of the follicles and eggs following single dose administration of I131, most of the radioiodine was recovered in the growth zone which corresponded to the follicle’s development during the first day after administration.     

Protein consumption by mated, unmated, sterile and fertile adults of the Queensland fruit fly, Bactrocera tryoni and its relation to egg production

Abstract. Female adults of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) at 25 °C require more than 0.1 mg of yeast autolysate per day to mature their oocytes to the vitellogenic stage and mate. Those given 0.2 mg per day from day 2 of adult life mated (when given the opportunity between 11 and 13 days) and each laid approximately 100 eggs (just over one egg per ovariole) by day 56. Females allowed to feed ad libitum from day 2, then 0 or 0.2 mg per day from day 14, laid approximately 75 and 100 eggs, respectively (after mating), whereas those fed ad libitum from day 2 to day 56 laid approximately 540 eggs after mating (averaging just over six eggs per ovariole). The developmental pattern of intake of normal females when on an ad libitum diet showed a rise to a peak at 5–7 days, followed by a decline to sustained low levels if not mated, but rising to a lower peak if mated between days 11–13 followed by a steady decline. Female flies that had been sterilized by 80 Gy gamma irradiation at the puparial stage had a pattern of food consumption similar to that of normal females mated at 7 days but they produced no yolky oocytes and had a darkened fat body. Normal and irradiated males had a feeding pattern similar to that of unmated nonirradiated females but at a lower level. The results are discussed in terms of the control of protein intake and the rate of its conversion to yolk.     

ESTABLISHMENT OF WEIGHT HIERARCHIES IN THE BROODS OF HOUSE MARTINS DELICHON URBICA

Nestling birds may differ in size and weight on the first day a clutch is fully hatched, mainly because eggs within clutches hatch over a period of several days. This asynchronous pattern of hatching is usually thought to facilitate brood reduction when the food supply is unpredictably restricted. The purpose of the study reported here was to examine the contribution of egg-weight, clutch-size, hatching spread, food supply and season to weight differences in newly hatched broods of the House Martin. At laying, heavy eggs had a greater moisture and dry weight content than light eggs and immediately before hatching there was a correlation between initial egg-weight and the dry weight of embryo and yolk. Heavier clutches also tended to give rise to heavier hatchlings. There was, however, no correlation of fresh egg-weight with the dry weight of embryos alone and the relative dry weight of embryos in a clutch was dependent on laying sequence. Hatching spread (the number of days between the emergence from the egg of the first and the last hatchling of the clutch) was 0.75 ± 0.46 days for clutches of two and increased with the size of the clutch up to 1.80 ± 0.79 days for clutches of five. When food was scarce during laying, hatching spread was greater. Weight difference in newly hatched broods was correlated with hatching spread and moreover in multivariate analysis was also correlated with periods of food scarcity during laying. It was concluded that all examples of weight hierarchies among hatchlings should not be considered adaptive; in some cases they may be imposed by food scarcity. This can lead to mortality of the runs even if food is plentiful. When the weight hierarchy is not adversely accentuated by food scarcity it may function as previously suggested, to allow brood reduction. Alternatively, particularly among House Martins, it may spread out the peak food needs of individual nestlings thereby spreading the demand on the adults.     

Predation of Clitostethus arcuatus (Col.: Coccinellidae) on Trialeurodes vaporariorum (Hem.: Aleyrodidae)

Greenhouse whitefly, Trialeurodes vaporariorum, is a serious pest of glasshouse crops. It shows resistance to different insecticides and growers are interested in finding other useful control methods. This research was carried out to study the predation potential and biology of Clitostethus arcuatus (Rossi) as one of the most important predators of this pest. Adult C. arcuatus were reared on tobacco leaves bearing colonies of greenhouse whitefly eggs under controlled conditions (25±2°C, 65±5% RH and 16 h L:8 h D). Results showed that the average developmental time of the egg, first through fourth instar larva and pupa were 2.82±0.12, 4.47±0.14, 4.54±0.1, 6.3±0.2, 7±0.22 and 3.8±0.13 days, respectively; and longevity of female and male were 66.4±2.6 and 54.9±2.5 days, respectively. The average feeding rates of female, male and larvae (first through fourth) were 61.4±0.7, 27.6±0.9 eggs/day and 12±1.03, 30.3±2.4, 41.3±2, 68.04±2 eggs/day, respectively. The larvae consumed an average of 992.2±36 eggs during the total larval developmental period with a daily mean of 45.8±0.5. A significant difference was shown between the feeding rate of fourth instar larval stages and between sexes. Females, males and one pair of C. arcuatus (♀,♂) consumed an average of 17.2±0.4, 10.6±0.8, 23.1±0.5 nymph/day; 28.5±0.9, 20.3±0.6, 47.2±0.6 pupa/day and 8±0.3, 6.5±0.54, 13.6±0.4 adult/day, respectively. The feeding rate was significantly different among whitefly life stages. Females laid an average of 3±0.23 eggs/day.     

Breeding ecology of Red‐faced Cormorants in the Pribilof Islands,Alaska

ABSTRACT Red‐faced Cormorants (Phalacrocorax urile) are North Pacific endemics recognized as a vulnerable species, but little is known about their breeding ecology. We studied Red‐faced Cormorants on St. Paul Island, Alaska, from 1975 to 2009, with more detailed data collected in 2004 and 2005. Mean clutch sizes in 2004 (3.2 ± 0.8 [SD] eggs) and 2005 (3.1 ± 0.8 eggs) were similar to the long‐term average (2.9 ± 0.3 eggs from 1976 to 2009). The mean laying interval in 2004 and 2005 was 2.15 ± 0.80 d (N= 407), and the mean egg period (number of days between laying of an egg and hatching) was 31.1 ± 1.4 d (N= 158). Approximately 64 ± 17% of eggs hatched during the period from 1975 to 2009. The mean number of chicks per nest in 2004 and 2005 was 2.8 ± 0.8 (N= 232), and the mean number of fledglings per initiated nest in all years was 1.22 ± 0.52. Chicks fledged 46 to 66 d posthatching. In 2004 and 2005, the primary causes of egg loss were predation by Arctic foxes (Vulpes lagopus) and destruction of eggs and abandonment of nests due to storms. Starvation was the primary cause of nestling mortality in both years. Because chicks are dependent on parents to provide food for over 45 d, consistent near‐shore foraging opportunities must be available. From 1975 to 2009, Red‐faced Cormorants experienced only 1 yr of complete reproductive failure (1984). The consistent reproductive success of Red‐faced Cormorants suggests that conditions may be relatively stable for this species on St. Paul Island, or that the variability in their breeding ecology (e.g., phenology, clutch sizes, and incubation strategies) provides the flexibility needed to successfully fledge some chicks nearly every year.     

No sex difference in yolk steroid concentrations of avian eggs at laying

Yolk steroids of maternal origin have been proposed to influence genetic sex determination in birds, based on sex differences in yolk steroid concentrations of peafowl eggs incubated for 10 days. More recent reports dispute this proposal, as yolk steroids in eggs incubated for 3 days do not show such sex differences. To date, research examining this phenomenon has only analysed incubated eggs, although sex in avian species is determined before incubation begins. This may be a serious methodological flaw because incubation probably affects yolk steroid concentrations. Therefore, we investigated sex differences in yolk steroid concentrations of unincubated avian eggs. We withdrew yolk for steroid analysis from fresh, unincubated Japanese quail (Coturnix japonica) eggs by biopsy, and then incubated those eggs for 10 days, after which we harvested the embryonic material for genetic sexing and the incubated yolk for further steroid analysis. We found no sex differences in fresh Japanese quail eggs; however, sex differences were apparent in yolk steroids by day 10 of incubation, when female eggs had significantly more oestrogen in relation to androgen than male eggs. Concentrations of all yolk androgens decreased dramatically between laying and day 10 of incubation, whereas oestradiol (E2) concentrations increased marginally. Thus, yolk concentrations of androgens and E2 do not appear critical for avian sex determination.     

A new type of highly polymerized yolk protein from the cochineal insect Dactylopius confusus

A female specific protein was isolated from eggs and female hemolymph of cochineal insects, using density gradient ultracentrifugation, ammonium sulfate precipitation, and size exclusion column chromatography. The protein was found to consist of four different subunits with apparent molecular weights (Mr) 45,000, 49,000, 53,000, and 56,000, respectively. All four subunits were found to be glycosylated; no association of lipids was detected. Size exclusion column chromatography and non-denaturing polyacrylamide gel electrophoresis demonstrated that the native yolk protein exists as large polymers. Electron microscopy showed that these molecules are long, helical ribbons of variable size which are found in both hemolymph and eggs. Using cryo-electron microscopy, it was shown that the ribbons were 14.6 ± 1.5 nm wide; the helix they form has a repeat distance of 104.9 ± 11.3 nm and a diameter of 42.1 ± 5 nm. A clear substructure of the ribbons was recognized. The newly identified protein is the major yolk protein of Dactylopius confusus and no other proteins resembling the more familiar vitellins of other insect species were detected. Moreover, the D. confusus yolk protein appears to be unique both in its subunit structure and in its polymerizing qualities. Thus, the cochineal yolk protein (CYP) is suggested to represent a new type of insect yolk protein. © 1996 Wiley-Liss, Inc.     

Developmental progression of gill rakers as a post-hatch developmental marker in pink salmon, Oncorhynchus gorbuscha

We evaluate the usefulness of gill rakers as a post-hatch developmental marker in salmon by tracking development in undisturbed and stressed yolk-bearing salmon embryos. Native pink salmon (Oncorhynchus gorbuscha) from Auke Creek, Juneau, Alaska and genetically stressed outbred hybrids between Auke Creek and Pillar Creek (Kodiak Island) salmon were incubated in ambient-temperature Auke Creek water. Environmentally stressed native embryos were reared in water that was 2 to 4 °C warmer than ambient. The sum of rakers on the first left and right branchial arches of natives reared at ambient temperatures averaged 23.20 (SD?±?1.64) per embryo when post-hatch sampling began. The subsequent increase in raker counts was linear and positively correlated with the accumulation of thermal units until counts reached maxima 223 days after fertilization, which coincided with the complete consumption of yolk reserves. The average maximum raker count was 39.55 (SD?±?1.76) per embryo, which is substantially fewer than the 60 rakers typically observed in adults. Neither raker development nor yolk consumption patterns were affected by hybridization. Elevated incubation temperatures accelerated raker formation and yolk consumption in native embryos, but the number of rakers associated with a given amount of yolk was the same regardless of temperature suggesting that changes in yolk consumption rate and raker development rate did not influence raker counts. These results indicate that rakers are easily observed and counted, grow in a predictable sequence, and are developmentally stable in the face of both genetic and environmental stress, thereby making them potentially reliable post-hatch developmental markers.     

Intrinsic rate of natural increase of Brueelia amandavae (Ischnocera, Phthiraptera) populations infesting Indian red avadavat

The incubation period of eggs, duration of three nymphal instars, adult longevity and the daily egg-deposition rate of the ischnoceran Phthiraptera, Brueelia amandavae, were determined by rearing the louse in vitro (35 ± 1°C, 75–82% RH, feather diet). The data obtained were utilized for life table construction and determination of the intrinsic rate of natural increase (0.031 per day) and the doubling time (23.45 days) of the louse population. The doubling time of the louse in in vivo experiments was 21.5 days.     

An accurate tool for ageing Two‐spined Blackfish for use in determining timing of spawning in upland streams in the Brindabella ranges,ACT, Australia

To manage populations of threatened fish species in modified habitats and regulated rivers requires an understanding of their reproductive biology and spawning cues. In particular, accurate information about early life stages in these species can be used to facilitate programmes that maximise recruitment and breeding success. This study aimed to develop methods to accurately age early juvenile freshwater native fish, Two‐spined Blackfish, (Gadopsis bispinosus), to allow the determination of spawning date. This was accomplished through the examination of otolith microstructure in early juveniles. The age at which the first ring was deposited and the relationship between days and number of rings were determined using both field and aquarium trials. Field trials of marked juvenile otoliths revealed daily deposition of rings (1.02 ± 0.02 rings per day for fish sacrificed six days postmarking). The strength of this relationship lessened slightly as juveniles aged (0.92 ± 0.02 rings per day for fish sacrificed 13 days postmarking). The first otolith ring was deposited 7.50 ± 1.09 days after spawning. The enumeration of daily rings combined with knowledge of the commencement of ring deposition enabled accurate estimation of spawning date. The current study is the first to examine otolith microstructure in juvenile Two‐spined Blackfish allowing accurate determination of spawning date. While more research is required to accurately age older juveniles, this technique has the potential to precisely correlate spawning with environmental cues, facilitating better management of temperature and flow during breeding periods, potentially increasing spawning and recruitment of this endangered species.