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2012年  第33卷  第E1-2期

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研究论文
Despite serotonin’s and FMRF-amide’s wide distribution in the nervous system of invertebrates and their importance as neurotransmitters, the exact roles they play in neuronal networks leaves many questions. We mapped the presence of serotonin and FMRF-amide-immunoreactivity in the central nervous system and eyes of the pond snail Lymnaea stagnalis and interpreted the results in connection with our earlier findings on the central projections of different peripheral nerves. Since the chemical nature of the intercellular connections in the retina of L. stagnalis is still largely unknown, we paid special attention to clarifying the role of serotonin and FMRF-amide in the visual system of this snail and compared our findings with those reported from other species. At least one serotonin- and one FMRF-amidergic fibre were labeled in each optic nerve, and since no cell bodies in the eye showed immunoreactivity to these neurotransmitters, we believe that efferent fibres with somata located in the central ganglia branch at the base of the eye and probably release 5HT and FMRF-amide as neuro-hormones. Double labelling revealed retrograde transport of neurobiotin through the optic nerve, allowing us to conclude that the central pathways and serotonin- and FMRF-amide-immunoreactive cells and fibres have different locations in the CNS in L. stagnalis. The chemical nature of the fibres, which connect the two eyes in L. stagnalis, is neither serotoninergic nor FMRF-amidergic.
Using scanning electron microscopy and optical microscopy, we studied the structure of the integument and wax glands of the mealybug, Phenacoccus fraxinus Tang (Hemiptera: Coccoidea: Pseudococcidae). We observed the ultrastructure of four wax pores including trilocular, quinquelocular, and multilocular pores as well as tubular ducts, recording characteristics of their structure, size and distribution. We found that that the integument of the mealybug consists of three main layers—the procuticle, epidermis and basement membrane—and four sub-layers of the procuticle—the epicuticle, exocuticle, endocuticle and formation zone. The wax-secreting gland cells were closely arranged in epidermis. All of them were complex and composed of one central cell and two or more lateral cells. These complex cells possess a large common reservoir for collection and storage. Synthesized by the glandular cells, the wax is excreted outside integument through canals.
Population viability analysis (PVA) is a tool to evaluate the risk of extinction for endangered species and aid conservation decision-making. The quality of PVA output is dependent on parameters related to population dynamics and life-history; however, it has been difficult to collect this information for the giant panda (Aliuropoda melanoleuca), a rare and endangered mammal native to China, confined to some 30 fragmented habitat patches. Since giant pandas are long-lived, mature late, have lower reproductive rates, and show little sexual dimorphism, obtaining data to perform adequate PVA has been difficult. Here, we develop a parameter sensitivity index by modeling the dynamics of six giant panda populations in the Minshan Mountains, in order to determine the parameters most influential to giant panda populations. Our data shows that the giant panda populations are most sensitive to changes in four female parameters: initial breeding age, reproductive rate, mortality rate between age 0 and 1, and mortality rate of adults. The parameter sensitivity index strongly correlated with initial population size, as smaller populations were more sensitive to changes in these four variables. This model suggests that demographic parameters of females have more influence on the results of PVA, indicating that females may play a more important role in giant panda population dynamics than males. Consequently, reintroduction of female individuals to a small giant panda population should be a high priority for conservation efforts. Our findings form a technical basis for the coming program of giant panda reintroduction, and inform which parameters are crucial to successfully and feasibly monitoring wild giant panda populations.
Identifying the life-history strategies of fish and their associations with the surrounding environment is the basic foundation in the conservation and sustainable utilization of fish species. We examined the age, growth, and reproduction of Sarcocheilichthys nigripinnis using 352 specimens collected monthly from May 2009 to April 2010 in the Qingyi Stream. We found the sex ratio of this study population was 0.58:1 (female: male), significantly different from expected 1:1. Females and males both comprised four age groups. The annuli on the scales were formed during February and March. No obvious between-sex difference was observed in length-weight and length-scale-radius relationships. The total length in back-calculation significantly increased with age for both sexes, but did not differ significantly at each age between the two sexes. An inflection point was observed in the growth curves given by the von Bertalanffy growth function for total weight. At this inflection point, fish were 3.95 years. Both sexes reach their 50% sex maturity at age 2, when females and males were 94.7 mm and 103.0 mm total length. The temporal pattern of the gonado-somatic index corresponded to a spawning period that occurred from April through July. The non-synchronicity of egg diameter in each mature ovary during the breeding period suggested these fish may be batch spawners. The absolute fecundity increased significantly with total length and weight, whereas no significant correlation was observed between the relative fecundity and body size.