The Mechanisms of Free Oxygen Radicals in Noise Induced Hearing Loss and Roles of Antioxidants in Protection against Noise Effects

Parental care to developing embryos and newly hatched animals are common in higher vertebrates such as birds and mammals. Such kind of care is rare in fish in which external fertilization is the normal mode of reproduction and very little parental care is involved. Only limited numbers of fish species exhibit parental care behavior such as nest building, guarding of embryos and newly hatched larvae. Provision of nutrients (via skin mucus secretion) to larvae by both parents is known only to a group (3 species) offfeshwater discus fish. The male bristle nose catfish (Ancistrus spp.) are known to build nest and protect embryos and newly hatched larvae. A unique morphological feature, the snout tentacles (hence the name: bristle nose catfish) has intrigued scientists about its function. Based on the distribution of taste buds on it, the tentacles have been suggested to have chemosensory function. Lately it is suggested that the appearance of juvenile-like tentacles could be a mimicry strategy used by males to lure females into accepting that he is a "good father" who is already taking care of larvae. The larval mimicry hypothesis has its merits but has not been tested yet. My preliminary examination on the snout tentacles of mature male Ancisturs shows that thousands of goblet cells lining the epithelia of snout tentacles. The results of a total of 13 histochemical staining methods demonstrate that mucus contents of the snout tentacles are likely to be a cluster of glycoprotein compounds of high energy content. This novel finding prompts me to propose a "paternal nutrition provision" (PNP) hypothesis which predicts the mucus secretions are used by male fish to provide exogeneous nutrients as energy source to the larvae under his care in order to enhance the growth and survival of larvae. This form of "paternal care" has never been reported in teleost fish other than discus fish which however involves both parents. In order to test the proposed PNP hypothesis, a total of four experiments will be carried out. (1) Determination o/chemical nature o/the mucus secretion. Protein electrophoresis and mass spectrometry methods will be used to conduct qualitative and quantitative analyses on the chemical natures of the glycoprotein compounds and to ascertain the energy values of these glycoprotein compounds. (2) The role o/mucus on the growth and survival o/larvae. Newly hatched larvae from the same clutch will be randomly divided into two groups with equal number of siblings. One group will be allowed to stay with the father, while the other group will be placed close to the nest but inside a cage preventing direct contact with the father. The PNP hypothesis predicts that mucus-fed larvae should grow faster and have less mortality than those without nutrient provision from the father. (3) Mucus secretion as olfactory attractants/or larvae and/emales. Behavioral assays will be conducted through a serious ofY-maze, two-choice experiments to demonstrate that both larvae and females can cue in mucus secretion as a mixture of olfactory attractants. (4) Electrophysiological responses to mucus secretion. Mucus secretions collected from male fish will be delivered to the nostrils of both larvae and female fish and the electro-olfactor-gram (EGG) will be obtained with recordings of evoked potentials from olfactory bulbs of test fish. The EGG recordings will provide electrophysiological proof of larvae and females' response to mucus secretion from male fish. The results of the proposed study will provide direct proof that mucus secretion from snout tentacles is used by male Ancistrus to provide nutrients to newly hatched larvae. The secretion can also be used to attract female as mate choice and mate recognition signals. This study intends to collect necessary baseline data in order to submit a full proposal to National Science Foundation to investigate the evolution of such a very rare paternal care reproductive strategy in Ancistrus catfish. .