Egg dumping and life history strategy of Callosobruchus maculatus

Abstract.  Previous studies have demonstrated that female Callosobruchus maculatus adjust oviposition rates to cope with changes in host availability. A female lays fewer eggs when host availability is low, and hence decreases larval competition. However, females will also dump eggs on unsuitable substrates under conditions of host deprivation. Because the female does not feed as an adult, egg dumping possibly wastes energy and may thus be a maladaptive behaviour. In this study, the effect of mating and age on the egg-dumping behaviour and the life history strategy of the female are explored. Under host-deprived conditions, mating is seen to trigger egg-dumping behaviour. Also, females mated at 6 days dump significantly fewer eggs and live longer than females mated at 0 or 3 days. Thus, a trade-off between fecundity and longevity is seen among females subjected to different manipulations. In addition, 6-day-old virgin females contain more mature eggs than females mated at 6 days can produce when deprived of hosts. This finding indicates that the female reallocates internal energy resources by oosorption in a resource-limited environment. To test the maladaptive hypothesis, mated females were deprived of a host for 6 days and then given sufficient hosts each day. The results show that the more eggs dumped by a female in the first 6 days, the more eggs are laid later on beans. Egg dumping is thus not maladaptive.     

How habitat disturbance benefits geckos: Conservation implications

I here provide some field observations and literature data showing that egg laying site availability could be the main limiting factor for most arboreal gecko population dynamics. Several natural (typhoons, volcanism, sea level variations) or human-mediated habitat modifications (garden openings in forested areas) provide enough habitat disturbances to significantly increase reproductive outputs in island gecko populations. Such observations, however, also apply to continental populations. Our observations suggest that artificial shelter and egg laying site creation could easily allow populations to increase and also supply easier access to arboreal species for ecological or biodiversity studies. Furthermore, our observations also point out that occurrence in man-made habitats and genetic uniformity of most widespread island lizards should not be considered as evidence of their recent introduction through human agency.     

滑鼠蛇的繁殖输出及孵化热环境对孵出幼体表型特征的影响

用15条2002年6月中旬捕自浙江丽水的怀卵滑鼠蛇研究繁殖输出及孵化热环境对孵出幼体表型特征的影响。母体在捕后3周内各产一窝柔性卵。窝卵数、窝卵重和卵大小均随母体体长增加而增大,平均值分别为13．3(枚卵)、332．4g和24．8g。窝卵数和卵大小的变异系数分别为0．18和0．13。窝卵数与产后母体状态呈正相关,卵数量和大小无关。每窝部分可孵卵分别用恒温(24、27、30、33℃)和21．0-39．0℃(平均28．3℃)范围内的波动温度孵化,每隔5d记录恒温孵化卵的重量。孵化热环境对卵与环境之间的水分交换有显著影响,并影响孵化卵重量的时间变化。24、27、30、33℃和波动温度的平均孵化期分别为105．4、78．0、57．8、51．3和58．6d。不同热环境下的孵化成功率和幼体畸形率有一定差别,但统计上不显著。24℃和30℃孵出幼体雄性比例较高,27℃、33℃和波动温度孵出幼体雌性比例较高,但没有证据表明孵化温度能决定滑鼠蛇性别。除孵出幼体灰分含量外,孵化温度对其它幼体特征均有显著影响。33℃孵出幼体SVL较小,但剩余卵黄和其中的灰分含量大于其它温度孵出的幼体。24℃和30℃孵出幼体的总干重、总能量、躯干干重、脂肪体干重总体上小于27℃和波动温度孵出幼体。24℃孵出幼体特征性具有最小的剩余卵黄,33℃孵出幼体则特征性地具有最大的剩余卵黄。24℃和30℃孵出幼体特征较为接近,27℃和波动温度孵出幼体较为接近。对9个幼体特征变量做主成分分析发现,第一和第二主成分共解释81．2％的变异。幼体SVL、湿重、干重、脂肪含量、能量、躯干干重和脂肪体干重在第一主成分有较高的正负载系数(解释56．9％变异),剩余卵黄干重在第二主成分有较高的正负载系数(解释24．3％变异),第一和第二主成分的分值均差异显著。主成分分析进一步显示,24、30和33℃孵出幼体总体上小于27℃和波动温度孵出幼体[动物学报50(4)：541-550,2004]。     

不同孵化湿度下的乌龟卵孵化成功率及新生幼体特征

A total of 51 Chinese three-keeled pond turtle Chinemys reevesii eggs were incubated on wet and dry substrates (water potentials of - 12 kPa and - 300 kPa, respectively) at 30℃ to assess the influence of the hydric environments on egg survival and hatchling traits. Eggs incubated in the dry condition lost weight, whereas those incubated in the wet condition did not. The hydric environments did not affect incubation lengths (60.3 vs 60.7 days) as well as hatching successes (69.2% vs 88.0% ). Except for wet body mass and carapace width, which were larger for hatchlings from the -12 kPa treatment than from the -300 kPa treatment, the hydric environments did not affect most hatchling traits. These unaffected traits included dry body mass, carapace length, tail length, limb length, hatehling components (carcass, residual yolk and fat bodies), swimming performance and critical thermal minimum. In conclusion, within the water potential of -12 to -300 kPa, hydric environments have little effect on embryonic development and hatchling traits in Chinese three-keeled pond turtles [Acta Zoologica Sinica 50 (1) : 133 - 136, 2004].     

Developmental morphology of the cyprinid fish, Candidia barbatus

 Embryonic, larval, and juvenile development of a Taiwanese cyprinid fish, Candidia barbatus, is described from laboratory-reared specimens. The eggs, measuring 1.8–2.1 mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk and no oil globule. Hatching occurred 56–69 h after fertilization, the newly hatched larvae measuring 4.9–5.3 mm in body length (BL) with 25–26 + 13–14 = 39–40 myomeres. The yolk was completely absorbed at 7.6 mm BL. Notochord flexion was initiated at 6.8 mm BL and finished at 7.6 mm BL. Aggregate numbers of all fin rays were completed at 12 mm BL. Barbels on the upper jaw appeared near the corner of the mouth at 17 mm BL. Eggs of the species closely resembled those of its related cyprinid genera, Opsariichthys and Zacco. Larvae and juveniles of C. barbatus were similar to those of O. uncirostris subspp., Z. platypus, and Z. pachycephalus, but differed from the latter in the process of disappearance of the adipose finfold (postflexion larval stage), barbels on upper jaw (juvenile stage), and pigmentation on the lateral body surface (postflexion larval and juvenile stages). Although C. barbatus also differed from the Z. temminckii species' group [Z. temminckii and Zacco sp. (sensu Hosoya, 2002)] in having barbels, larvae and juveniles of the former showed more similarity to the latter species group than to O. uncirostris subspp., Z. platypus, and Z. pachycephalus, from the aspect of head and body pigmentation.     

A fluvial population of Cottus pollux (middle-egg type) from the Honmyo River, Kyushu Island, Japan

 Specimens of the Cottus pollux species' group collected from the upper part of the Honmyo River, Nagasaki Prefecture, Japan, were subjected to morphological and allozyme analyses to place them into one of the recognized valid taxa, viz. small-egg type (SE type), middle-egg type (ME type), or large-egg type (LE type). They were identified as ME type on the basis of specific morphological characteristics, such as laterally depressed cross-sectional shape at posterior half of the body and deep caudal peduncle, and by having a diagnostic allozyme allele (MEP ^* 54). This ME-type population is the first recorded from Kyushu Island, Japan. An ecological survey of the population revealed that females spawned larger eggs (2.8–3.2 mm in diameter) than those of other amphidromous populations, from which well-developed yolk-sac larvae of about 8.0 mm TL were hatched out. In addition, ME-type specimens collected on 25 and 26 May 2001 included 15 sex-unknown juveniles ranging from 18.8 to 30.2 mm SL, suggesting that they represented larvae hatched out on a nearby spawning ground, with no experience of downstream migration into Isahaya Bay. This observation strongly suggests that the ME-type population in the Honmyo River has a fluvial lifestyle, being different from other amphidromous populations. The former population may have arisen from an amphidromous ancestor through changes in egg size and early ontogenetic development. Received: February 25, 2002 / Revised: May 21, 2002 / Accepted: June 17, 2002 Acknowledgments We thank Professor M. Azuma, Nagasaki University, for his kind guidance of our field survey in the Honmyo River and Dr. G.S. Hardy, Thames, New Zealand, for correcting the English. Thanks are also offered to Mrs. Y. Miyajima and Y. Masaoka, Kyushu Branch of Construction and Technology Institute Co., for their helpful cooperation in the field survey. Drs. H. Sakai, National Fisheries University and Y. Yamazaki, Toyama University, and Mrs. N. Okabe and Y. Suzuki of Yamagata Prefecture are thanked for their help in sample collection. This work was partly supported by a Grant-in-Aid (No. 13660171) from the Japan Ministry of Education, Culture, Sports, Science and Technology to A. Goto. Correspondence to:Akira Goto     

Effects of providing dietary wood (oak) charcoal to broiler chicks and laying hens

Three experiments were carried out to determine whether dietary wood (oak) charcoal applied during entire or phase feeding period would affect growth performance, abdominal fat weight, carcass weight, carcass yield, carcass composition and nutrient excretion of broilers and to determine whether dietary wood charcoal supplementation would affect laying performance and egg quality of laying hens. In the first experiment, different inclusion levels (0, 25, 50 and 100 g/kg feed) of wood charcoal in the diet were examined for a 6-week-period using broiler chicks of initial age 1 week. Dietary wood charcoal significantly increased feed intake (P<0.001), body weight gain (P<0.001) and improved feed conversion ratio (P<0.05) up to 28 days of age. However, at 49 days of age, charcoal inclusion did not significantly (P>0.05) affect body weight gain, feed intake, carcass weight and carcass yield, but increased (P<0.05) feed conversion ratio, carcass ash content, fat excretion, while reducing (P<0.05) mineral excretion in a dose dependent manner. In the second experiment, a phase application of dietary wood charcoal for a 6-week-period broiler chicks of initial age 1 week was assessed. During the first 28 days of age wood charcoal improved feed conversion ratio significantly (P<0.05). At 49 days of age, the groups receiving charcoal in the starter and/or finisher diets showed significantly (P<0.05) higher body weight gain and carcass weight than the control group receiving no charcoal. In the third experiment, different levels (0, 10, 20 and 40 g/kg feed) of wood charcoal supplementation to a layer diet were examined for a 7-week-period using laying hens of initial age 34 weeks. Dietary charcoal supplementation did not have a significant effect on any parameters related to performance and egg quality, but significantly reduced number of cracked eggs and the reduction was dose dependent (P<0.01). These data demonstrate that wood charcoal inclusion to the diet could be of value in improving broiler performance during the first 28 days of fattening period. In later ages, the positive effects of wood charcoal are limited. However, in laying hens dietary supplementation of wood charcoal reduces number of cracked eggs.     

Omnivory in the calanoid copepod Temora longicornis: feeding, egg production and egg hatching rates

We measured in laboratory experiments the ingestion, egg production and egg hatching rates of female Temora longicornis as a function of diet. The diets consisted of a diatom (Thalassiosira weissflogii), an autotrophic dinoflagellate (Heterocapsa triquetra), and a bacterivorous ciliate (Uronema sp.) given as sole foods, or combinations of these single-food items: diatom+dinoflagellate, diatom+ciliate, dinoflagellate+ciliate, and diatom+ciliate+dinoflagellate. For the three single-item diets, the functional response was similar; i.e., ingestion rate increased linearly with food concentration (food range: ∼25 to ∼600 μg C l⁻¹). When all diets were considered, maximum daily carbon ration (∼70% of body weight) was independent of food type. However, the maximum daily egg production rate (12% of body carbon) was obtained with the diatom diet. For all diets, both ingestion and egg production rates increased with food concentration. Ingestion and egg production rates were affected differently by the interaction of food concentration and food type: at low food concentrations, ingestion rates were highest on diets containing the diatom. At high food concentrations, egg production rates were highest on the two phytoplankter diets and their combination. The presence of the ciliate in the diet did not enhance ingestion rate or egg production. Mixed-food diets did not enhance egg production relative to single-food diets. Hence, dietary diversity did not appear to be particularly advantageous for reproduction. Carbon-specific egg production efficiency (EPE; egg production/ingestion) was independent of food concentration and type, and equaled 9%. Egg hatching success was low (mean<30%) and independent of food concentration and type, and egg production rates. Our results are consistent with previous observations that egg production in T. longicornis is enhanced during diatom blooms. However, the relatively low EPE and egg hatching success suggest that reproduction and recruitment in this study were severely constrained by the biochemical composition of the diet, or the physiological condition of the females towards the end of their season of growth in Long Island Sound.     

Interaction between eggshell temperature and carbon dioxide concentration after day 8 of incubation on broiler chicken embryo development

Carbon dioxide (CO₂) is considered to be an important factor during incubation of eggs. Effects attributed to higher CO₂ concentrations during experiment might be due to confounding effects of other environmental conditions, such as incubation temperature. To disentangle effects of eggshell temperature (EST) and CO₂ concentration, an experiment was conducted. A total of 630 Cobb 500 hatching eggs from 37 to 45 wk commercial breeder flocks were collected and incubated according to treatments. The experiment was setup as a complete randomized 2 × 3 factorial design, resulting in 6 treatments. From day 8 of incubation onward, broiler eggs were exposed to one of two EST (37.8 or 38.9 °C) and one of three CO₂ concentrations (0.1, 0.4 or 0.8%). Eggs were incubated in climate-respiration chambers and metabolic heat production was determined continuously. At day 18 of incubation and at 6 h after hatching, embryo and chicken quality were determined by evaluation of organ weights, navel condition, blood metabolites and hepatic glycogen. Hatching time and chicken length at 6 h after hatching showed an interaction between EST and CO₂ concentration (both P = 0.001). Furthermore, no effect of CO₂ concentration was found on embryo development or chicken quality. Metabolic heat production between day 8 and 18 of incubation was not affected by either EST or CO₂. At day 18 of incubation, an EST of 38.9 °C resulted in a higher egg weight loss, longer embryos, higher yolk free body mass (YFBM) and lower heart weight than an EST of 37.8 °C (all P < 0.008). At 6 h after hatching, an EST of 38.9 °C resulted in a higher residual yolk weight and lower YFBM, liver weight and heart weight than an EST of 37.8 °C (all P < 0.003). Lactate, uric acid and hepatic glycogen were not affected by EST at either day 18 of incubation or at hatch. Glucose was not affected by EST at day 18 of incubation, but at hatch, it was higher at an EST of 37.8 °C than at an EST of 38.9 °C (P = 0.02). It can be concluded that effects of CO₂ concentration (at concentrations ≤0.8%) on embryonic development and chicken quality appear to be limited when EST is maintained at a constant level. Moreover, a higher EST from day 8 of incubation onward appears to negatively affect chicken quality at hatch.