Dynamics of heat transfer to cold eggs in incubating bantam hens and a black grouse

Incubating birds transfer large amount of heat from the brood patch to the eggs during rewarming of cold eggs. If a vasoconstriction is present in the brood patch as in other parts of the body, it could possibly limit heat transfer to the eggs. To investigate this, heat transfer to water-circulated eggs was measured in incubating bantam hens (Gallus domesticus) and a black grouse hen (Lyrurus tetrix) during exposure to cold eggs. Egg temperature, egg surface temperature, heat production and cloacal temperature were also measured. At all levels of egg cooling, egg surface temperature and heat transfer to the eggs was stable throughout an exposure, except during resettling movements, which often changed egg surface temperature and the level of heart transfer. Egg surface temperature decreased linearly with egg temperature in both species, but was lower and more variable at low egg temperature in black grouse than in bantam hens. A higher proportion of the heat production was transferred to the eggs in the black grouse (corresponding to 109–118% of the increase above resting level) than previously reported in bantam hens. Clutch size did not affect this efficiency of heat transfer in black grouse. It is concluded that a vasoconstruction of the brood patch does not occur even under strong cold stress from the eggs. Heat transfer to the eggs is probably controlled more by behavioural adjustments than circulatory changes. An increase in brood patch blood flow probably occurs at relatively high egg temperature at the onset of egg rewarming. The efficiency of heat transfer, and thus the energetic cost of rewarming eggs, depends on the insulation of the bird and nest structure. The boreal/subarctic black grouse was able to reduce heat loss to the environment and transfer a higher proportion of its heat production to the eggs than the tropical bantam hen.Abbreviations AVAs arteriovenous anastomoses - HP heat production - HT heat transfer - T _a ambient temperature - T _b cloacal temperature - T _brp brood patch temperature - T _e egg temperature - T _es egg surface temperature     

Comparative life history of female mosquito fish,Gambusia affinis,in tidal freshwater and oligohaline habitats

Synopsis Female Gambusia affinis were collected from low salinity/near-neutral pH and tidal freshwater/low pH localities to document life history variation between these two habitats. Mosquito fish were 2.7 times more abundant in low salinity/near-neutral pH (2.37 ± 0.72 ppt; pH = 5.73 ± 0.11) than in tidal freshwater/low pH (0.27 ± 0.19 ppt; pH = 4.46 ± 0.18) habitats in Old Fort Bayou, a black-water tidal river of the Biloxi Bay estuary, Mississippi. Fish were common in both areas from June 1985 through February 1986. There were no significant differences between habitats in the length-weight relationships during the reproductive season with the exception of February. However, there were significant differences in life histories, although the areas were only 4 km apart. Ovarian recrudescence was observed in fish from both areas in February, but ovaries of low salinity fish were more developed than ovaries of freshwater fish. All fish from both areas had regressed ovaries by late September. The monthly slopes of the brood size vs. standard length regressions were significantly different between areas throughout the reproductive season with the exception of June. Although freshwater fish produced heavier tail-free embryos, fish from low salinity had significantly higher GSI values and brood size throughout the reproductive season. These observations suggest that Gambusia affonis may have a greater reproductive effort in low salinity/near-neutral pH environments than in freshwater/low pH habitats.     

Geographic variation in parasitism rates of two sympatric cuckoo hosts in China

Rates of brood parasitism vary extensively among host species and populations of a single host species. In this study, we documented and compared parasitism rates of two sympatric hosts, the Oriental Reed Warbler (Acrocephalus orientalis) and the Reed Parrotbill (Paradoxornis heudei), in three populations in China. We found that the Common Cuckoo (Cuculus canorus) is the only parasite using both the Oriental Reed Warbler and Reed Parrotbill as hosts, with a parasitism rate of 22.4%-34.3% and 0%-4.6%, respectively. The multiple parasitism rates were positively correlated with local parasitism rates across three geographic populations of Oriental Reed Warbler, which implies that higher pressure of parasitism lead to higher multiple parasitism rate. Furthermore, only one phenotype of cuckoo eggs was found in the nests of these two host species. Our results lead to two conclusions: (1) The Oriental Reed Warbler should be considered the major host of Common Cuckoo in our study sites; and (2) obligate parasitism on Oriental Reed Warbler by Common Cuckoo is specialized but flexible to some extent, i.e., using Reed Parrotbill as a secondary host. Further studies focusing on egg recognition and rejection behaviour of these two host species should be conducted to test our predictions.     

Occurrence of Amoebophrya spp. infection in planktonic dinoflagellates in Changjiang (Yangtze River) Estuary,China

The parasitic dinoflagellates in the genus of Amoebophrya can infect broad ranges of planktonic dinoflagellates, and transform algal biomass into organic matter that can be recycled within the planktonic community. The ecological significance of Amoebophrya spp. during harmful algal bloom (HAB) events was gradually recognized along with revelation of its host specificity and diversity in picoplankton communities. The eutrophicated coastal waters of China are frequently affected by HABs, particularly in Changjiang (Yangtze River) estuary and the adjacent East China Sea; while, no research has been conducted to explore the ecological roles of parasitism during HAB events and the related dinoflagellate bloom dynamics. For the first time, we confirmed the presence of Amoebophrya infections in the planktonic community of this region; six species of dinoflagellates were infected, including Ceratium tripos, Scrippsiella trochoidea, Gonyaulax spinifera, Gymnodinium sp., Gonyaulax sp. and an Alexandrium sp. Molecular sequences retrieved from environmental water samples revealed high genetic diversity of Amoebophryidae-like organisms in the water column. Amoebophrya-infected dinoflagellates were only observed in high salinity (>20) stations suggesting that salinity may be a factor limiting the distribution of Amoebophyra infections in natural environment. Whereas, no evidence of Amoebophrya infection was observed in the bloom-forming species Karenia mikimotoi, suggesting that K. mikimotoi in this region was likely free of Amoebophridae infection.     

Brooding season, sex ratio, and brood pouch development in the seaweed pipefish, Syngnathus schlegeli, in Otsuchi Bay, Japan

Males of the seaweed pipefish, Syngnathus schlegeli, take care of their eggs in the brood pouch. These pipefish were periodically collected from the shallow seagrass beds in Otsuchi Bay on the Pacific coast of northern Honshu, Japan, from spring to autumn to investigate the basic reproductive ecology. Appearance of the pipefish in the coastal seagrass beds coincided with the initiation of reproduction. The reproductive season was from May to at least October, with its peak in July. A rearing experiment revealed that the brooding period of the male had a negative correlation with water temperature, and it was estimated to last about 1 month in the bay. Almost all males were brooding during the peak of the reproductive season. Although, the brood pouch of most males was either full or devoid of eggs, 6.2% of the males had a partially filled (20%–90%) brood pouch, and multiple clutches were identified in the brood pouch of some males, indicating that the mating system of the pipefish is polygamous, perhaps polygynous. Sex ratio fluctuated among months, and the overall sex ratio tended to be biased to male. Body size of males with an immature brood pouch had a wide range, from 133 to 215 mm standard length (SL). The smallest brooding male was 134 mm SL. Mean SL of brooding males was significantly larger than that of nonbrooding mature males. The number of males with an immature brood pouch was greater at the beginning than later in the reproductive season. The results seem to collectively indicate that the occurrence of a larger proportion of immature males at the onset of the reproductive season may be ascribed to both new recruitment and larger body size at maturation, resulting from the males trading the reproductive effort to somatic growth, perhaps to increase future reproductive success. Received: April 4, 2000 / Revised: September 21, 2000 / Accepted: January 16, 2001     

Multiple Parasitism by Cotesia sesamiae and Cotesia flavipes (Hymenoptera: Braconidae) on Busseola fusca (Lepidoptera: Noctuidae)

Busseola fusca (Fuller) is one of the most important pest of cereals in sub-Saharan Africa. Cotesia sesamiae (Cameron) is the predominant parasitoid attacking B. fusca larvae in many parts of Africa. An exotic parasitoid, Cotesia flavipes Cameron, was introduced into Kenya in 1993 for the control of Chilo partellus (Swinhoe). Laboratory studies indicated that although C. flavipes would search for, and attack B. fusca , it was not able to complete its development in this host. The aim of the present study was to investigate the outcome of multiple parasitism of B. fusca by the two Cotesia species. The study showed that when both parasitoid species stung a B. fusca larva at the same time, both parasitoids emerged from more than half of the host larvae, C. flavipes alone emerged from 17%, and C. sesamiae alone emerged from 9%. When the larvae were parasitized by C. sesamiae first, and then 2 h later by C. flavipes , and vice versa, most of the progeny were C. flavipes . However, when B. fusca larvae were stung by C. sesamiae three days before oviposition by C. flavipes , significantly more C. sesamiae emerged from the larvae. When C. flavipes oviposited first, no larvae produced C. flavipes only. The interaction of parasitoids and the host immune system, and the implications of these results for the biological control of stem borers in East Africa are discussed.     

Osmoregulatory disturbances induced by the parasitic barnacle Loxothylacus texanus (Rhizocephala) in the crab Callinectes rathbunae (Portunidae)

The osmoregulatory response of the blue crab Callinectes rathbunae parasitized with the rhizocephalan barnacle Loxothylacus texanus, and subjected to sudden salinity changes, was experimentally measured in the laboratory. Parasitized and control crabs were exposed to salinity changes every 3 h and their hemolymph osmolality measured. Two experiments, one with increasing salinity conditions (5‰, 12‰, 19‰, 25‰) and a second one with decreasing salinities (35‰, 25‰, 15‰, 5‰) were conducted. The results show that L. texanus significantly alters the hemolymph osmolality of C. rathbunae maintaining it at lower than normal levels. In the increasing salinity trial, the hypoosmotic hemolymph condition of parasitized crabs was present at all salinities tested, whereas in the decreasing salinity trial a significant effect was found only at salinities of 5‰ and 15‰. Since C. rathbunae is constantly subjected to abrupt salinity changes in the tropical estuaries where it occurs, moving into high salinity areas may be the only way to cope with the impact of L. texanus.     

白冠长尾雉育雏期的栖息地选择

20 0 1年 4～ 8月 ,在河南省董寨国家级自然保护区对白冠长尾雉 (Syrmaticusreevesii)育雏期的栖息地进行了调查。野外共遇见 2 4个不同的家族群 ,平均大小为 (2 96± 0 35 )只。白冠长尾雉的家族群主要在针阔混交林中活动 ,这些地方的坡向以东南方向居多、坡度较缓而坡位靠下 ,与林缘的距离大于 6 0m而与水源的距离通常小于 30m。逐步判别分析的结果表明 ,与林缘的距离、乔木胸径、灌木盖度、草本植物的种类和高度等是影响白冠长尾雉家族群栖息地选择的关键因子 ;植被结构 ,尤其是草本植物的特征 ,是影响家族群栖息地选择的主要方面。建议在对白冠长尾雉采取保护措施时 ,从提供丰富的食物资源和良好的隐蔽条件入手。注意保护现存栖息地 ,在育雏期保护好草本植物。     

Intraspecific and Interspecific Competition Between Cotesia flavipes and Cotesia sesamiae (Hymenoptera: Braconidae), Gregarious Larval Endoparasitoids of Lepidopteran Stemborers

Super and multiple parasitism of Chilo partellus (Lepidoptera: Pyralidae) and Sesamia calamistis (Lepidoptera: Noctuidae) by Cotesia flavipes Cameron and Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) were investigated in the laboratory. Progeny production of Co. flavipes increased as a result of increasing the number of ovipositions, from one to three per one Ch. partellus host larva, then decreased as a result of four and five ovipositions per larva. Cocoon weight, sex ratio and emergence of the parasitoid progeny were not affected by superparasitism. Low progeny production of Co. sesamiae and poor survival of Ch. partellus host larvae were found as a result of superparasitism. When S. calamistis was the host, the duration of immature stages of Co. flavipes , parasitoid emergence, progeny production and sex ratio were not affected by superparasitism, but cocoon weight, adult longevity and the potential fecundity of adult females decreased. Superparasitism of S. calamistis by Co. sesamiae did not affect emergence, longevity or sex ratio of adult progeny of the parasitoid, but prolonged immature development, lowered cocoon weight and decreased potential fecundity of adult female progeny. Co. flavipes out-competed Co. sesamiae when Ch. partellus was parasitized by both species. The potential for local displacement of Co. sesamiae by Co. flavipes in areas dominated by Ch. partellus in East Africa is discussed.