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The larval stage of fishes is critical in determining their dispersal, survival and recruitment, but little is known of the larval behaviours and tolerances of amphidromous fishes, particularly in New Zealand. We report the results of a series of observational and experimental studies on bluegill bully (Gobiomorphus hubbsi), including spawning sites and behaviours, larval characteristics at hatch, phototactic responses of larvae, and larval survival at different salinity levels. Spawning primarily occurred in the lower reaches of the river, and larvae from different nests exhibited marked differences in, and trade-offs between, larval characteristics at hatch, potentially affecting larval success. Larvae were positively phototactic to intense light, an unexpected result based on diel drift patterns and international research. Finally, larvae exhibited markedly higher survival rates when reared at intermediate salinities compared to freshwater or seawater, suggesting estuaries may play an important role as nursery grounds for bluegill bully and other amphidromous fish. 相似文献
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Abstract. In the first decisive study of color-change in brittlestars, four Caribbean species, Ophiocoma echinata, 0. paucigranulata, O. pumila, and O. wendti are reported to change color from day to night. Color-change is most striking in O. wendti, which is dark brown during the day, and is banded gray and black from dusk to dawn. The transformation occurs over a 3 to 4 hour period and is effected by chromatorphores which appear to respond to illumination, independently of the central nervous system. Color-change may also be mediated by an endogenous rhythm. Ophiocoma wendti is more responsive to light than the other 3 species tested. It reacts to lower levels of illumination at night than during the day, exhibiting negative phototaxis in moonlight as well as in sunlight. I suggest that color-change may expose (or shield) photosensitive tissues that control the brittlestar's detection of shaded fissures in the reef. Thereby, chromatophore activity may be connected with the brittlestar's chief defense from predators, the ability to detect shadow and escape into darkened crevices. Although experiments to date with predacious fish are equivocal. the color patterns of Ophiocoma species mav provide protective camouflage. 相似文献
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Joo Serdio Helena Coelho Snia Vieira Snia Cruz 《Estuarine, Coastal and Shelf Science》2006,68(3-4):547
The migratory response of intertidal microphytobenthos to changes in irradiance was studied on undisturbed estuarine sediments. Two non-destructive optical techniques were used to trace variations in vivo of surface biomass: PAM fluorometry, for measuring the minimum fluorescence level (Fo); and spectral reflectance analysis, for quantifying the normalized difference vegetation index (NDVI). Following the formation of a dense biofilm at the surface, replicated sediment samples were simultaneously exposed to six different irradiance levels, ranging from 50 to 1500 μmol m−2 s−1, during a period of 120 min. The migratory photoresponse of the biofilms was characterised by constructing biomass vs. light curves (BLC), relating the accumulation of microalgal biomass after that period (estimated by Fo or NDVI) to the irradiance level incident on the surface. BLCs allow characterising the main features of the migratory photoresponse of intact biofilms. Typical BLC showed a clear biphasic pattern, with an increase in microalgal accumulation under irradiances below 100 μmol m−2 s−1, maximum values under 100–250 μmol m−2 s−1, and a gradual decrease of surface biomass under higher irradiances, indicating a strong photophobic downward migratory response. Similar BLC patterns were obtained when measuring Fo or NDVI. The construction of BLCs for biofilms from intertidal sites with distinctive sediment characteristics and diatom taxonomic composition allowed to detected significant differences in the migratory photoresponse. Biofilms from a muddy sediment exhibited considerably larger amplitude in the migratory photoresponse than the biofilms from a sandy mud site, especially under high irradiances. The photophobic migratory response to high light was found to vary among diatom species, particularly in the case of the biofilms from the muddy sediments. 相似文献
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头足类是现存最古老的海洋生物之一,为视觉性动物,视觉在它们的捕食、避敌、求偶、交配等活动中发挥了重要作用。在长期的进化过程中,头足类的眼睛为它们带来了视觉上的强大优势。目前国内关于头足类眼睛的研究较少,主要集中于头足类眼睛视网膜的研究,国外的研究则主要集中于头足类眼睛的结构特点和一些视觉特性,本文对头足类眼睛的形成、形态、结构、视敏度变化、偏振光敏感性、趋光性及眼外光感受器——感光囊进行了论述。综合分析认为,除鹦鹉螺外,头足类的眼睛发达,虽然它们的眼睛保留了无脊椎动物无法识别颜色这一特性,但已经具备了形成物像,进行屈光和光调节的完善而精细的系统结构,分辨率高,甚至还具有一些高等脊椎动物所不具备的功能,同时还有眼外光感受器——感光囊进行辅助作用。因此,和它们的分类地位一样,头足类的眼睛一定程度上也处于海洋动物由低等进化到高等的一个过渡型的地位。此外,本文也对目前头足类眼睛研究进展的问题和未来研究方向进行了总结和展望。希望可以引起国内外同行的重视,并为相关研究提供借鉴和参考。 相似文献
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