Effects of the slow cooling during cryopreservation on the survival and morphology of Taiwan shoveljaw carp (Varicorhinus barbatulus) spermatozoa

Over the past decades, pollution, overfishing, and habitat degradation have driven the population size of Taiwan shoveljaw carp down markedly in Taiwan. Cryopreservation is a useful tool which could be used to maintain genetic resources to protect and preserve this endemic species. Four cryoprotectants [dimethyl sulphoxide (DMSO), dimethylacetamide (DMA), glycerol and methanol] and six freezing rates (0.5, 1, 2, 4, 8, 16 °C min-1) were tested in order to develop an optimal controlled slow-freezing protocol for Taiwan shoveljaw carp spermatozoa. Samples were subsequently examined under the scanning electron microscope to reveal whether cryopreservation had affected their ultrastructural morphology. The highest survival rate (50.1 ± 2.0%) was observed with a freezing rate of 8 °C min-1 in 1M DMSO, using SYBR-14 + PI staining. Fertility and hatching rate results using frozen-thawed spermatozoa (90.2 ± 2.2% and 22.3 ± 2.5%, respectively) were not significantly different from results with fresh spermatozoa. After cryopreservation, 21.0 ± 1.6% of frozen-thawed spermatozoa had mid-piece swelling and rupture of the head. Cryopreservation might, therefore, slightly affect Taiwan shoveljaw carp spermatozoa in terms of morphological change. However, these alterations could be compensated by using large enough numbers of normally functioning frozen-thawed spermatozoa to achieve a standard equal to fresh spermatozoa. This is the first report of successful cryopreservation of Taiwan shoveljaw carp spermatozoa using a controlled slow-cooling method

Rethinking the Kibera ‘Slum’: The Role of Social Networks as a Mechanism for Coping with the Increased Demand for Job Opportunities

Rural-urban migration is a livelihood strategy used to increase income at the household level. This study proposes four stages of livelihood enhancement in the urban informal sector: (1) Migration from rural to urban areas, (2) Entering an informal sector, (3) Formation of self-help groups and local enterprises and (4) Expansion of stable income-generating activities. At these different stages, social networks play critical roles in connecting new migrants to the assets and networks that they need to increase and stabilize their income. At the forth stage, migrants who operate local enterprises start creating ties with their business partners in the formal sector. Yet, they tend to choose to remain in the informal sector because of the better access to income, assets and networks. The traditional dualistic view of labour market, which is segmented into the formal and informal sectors, is not applicable to the cases observed in Kibera because the residents’ ultimate goal for livelihood enhancement is not solely to enter the formal market but also to maximize their income. Economic activities observed in Kibera cannot be fully explained by applying the existing studies and general theories of ‘slum’ as evidenced by this study. Comprehending the current state of Kibera leads to plentiful implication for expanding the theory and practice of sustainable development the in the informal sector. Keywords: Kibera, Informal sector, Social networks, Job market, Sustainable Developmen