Size-hierarchy in a year-class and "condition" of common minnow Esomus danricus (Ham.) in relation to various ecological factors operating in the pond environment

Investigations were made on the existence of size-hierarchy in specimens of Esomus danricus (Ham.) belonging to the same year-class, and the variations in condition factor of the different size-groups. Divergence in the growth rates of individual fish resulted in the development of size-hierarchy in the population. Marked changes seemed to occur in condition factor of the different size-groups. A multitude of factors operating simultaneously in the pond environment appeared to govern the condition factor of fish.     

塔拉单宁水解酶产生条件的研究

微生物通过发酵产酶可以将植物单宁降解成小分子酚类化合物或其衍生物,但培养条件对其产酶影响很大。论文采用固态培养法,对黑曲霉产生塔拉单宁水解酶的条件进行了研究。结果表明,当培养液中塔拉单宁浓度为75 g/L、葡萄糖浓度为3 g/L、(NH4)2SO4浓度为0.2 g/L2、50 mL锥形瓶装液量为25 mL、惰性载体用量为5.6%(w/v)、起始pH为5.5、接种量为12%(v/v)、30℃培养72 h时,该黑曲霉产生的塔拉单宁水解酶活力可达到44.29 U/mL,是其自然条件下酶活力(24.09 U/mL)的1.84倍;没食子酸产率达到79.3%。研究结果对于揭示塔拉单宁生物降解的机理具有一定的参考价值。     

Some biological aspects and life history strategies of Nile tilapia Oreochromis niloticus (L.) in Lake Victoria, Kenya

The life history characteristics of introduced Nile tilapia (Oreochromis niloticus L.) in Lake Victoria, including, sex ratio, fecundity, reproduction, weight‐length relationship and body condition were studied and compared with those of other populations. Samples were collected by trawling and seining in the Kenyan sector of Lake Victoria between June 1998 and December 2000. Males predominated over females (sex ratio 1.42 : 1 : 00). O. niloticus spawned throughout the year but with a peak between December and June. Length at first maturity was (mean ± SD) 30.81 ± 0.09 for females and 34.5 ± 6 0.48 for males. There was little seasonal variation in relative condition, which ranged from 0.92 to 1.05 in males and 0.94 to 1.07 in females. Gonadosomatic index (GSI) was low during the postspawning period (July to October) and high during the protracted breeding period (December and June). Fecundity ranged from 905 to 7619 oocytes for fish of 28 to 51 cm total length (TL) respectively. The relationships between fecundity (F) and total length (L), weight (W) and ovary weight (OW) were: F = 8.159L^1.53, F = 96.269W^0.4504, F = 1806 + 39.4OW. The slope b of the weight‐length relationship was 3.08–3.32 for males and 3.07–3.22 for females. Growth was allometric in both cases and was significantly different from the expected value of 3. The life history strategy of O. niloticus is discussed in context of environmental changes occurring in the lake.     

Nutritional condition, starvation status and growth of early juvenile Japanese sea bass (Lateolabrax japonicus) related to prey distribution and feeding in the nursery ground

The nutritional condition and protein growth rates of Japanese temperate bass larvae and juveniles were studied in relation to prey distribution and feeding habits in the nursery grounds in Chikugo estuary, Ariake Sea, Japan. Samples were collected from a wide spatial area covering the nursery grounds of the fish in March and April 2003. Food habits of the fish were analyzed by examining the gut contents. Fish condition was evaluated by using RNA/DNA ratio and other nucleic acid-based indices and protein growth rates. The nucleic acid contents in individually frozen larvae and juveniles were quantified by fluorometric method. Two distinguished feeding patterns, determined by the distribution of prey copepods, were identified along the nursery ground. The first pattern showed the dependency of the fish on the calanoid copepod Sinocalanus sinensis, which was the single dominant prey in low saline upper river areas and the second pattern involved a multi-species dietary habit mainly dominated by Acartia omorii, Oithona davisae and Paracalanus parvus. Values of RNA, DNA, total protein, growth rates and for all the nucleic acid-based indices were higher in upstream areas than in the downstream areas. The proportion of the starving fish was higher in the downstream areas than in the upstream areas. Condition of juvenile sea bass was not equal throughout the nursery grounds; fish in the upper river were in better condition than those in the lower estuary. We speculated that utilization of S. sinensis, which appears a suitable prey item and provide a better foraging environment in the upstream nursery ground, is one of the key factors for early survival and growth of Japanese temperate bass larvae and juveniles in the Chikugo estuary.     

Male Condition, Female Choice, and Extreme Variation in Repeated Mating in a Scaly Cricket, Ornebius aperta (Orthoptera: Gryllidae: Mogoplistinae)

Mating in the scaly cricket Ornebius aperta often includes the transfer of many spermatophores to individual females during extended copulatory interactions. We manipulated male condition in staged matings to determine whether this could explain variation in the number of repeated copulations seen across pairs. Males on a high nutrient diet were in good condition, were more likely to mate repeatedly, and transferred more spermatophores on average than low-diet males (in poor condition). High-diet males were more likely to produce a vibratory signal that increased female receptivity to repeated mating attempts. Courtship and copulatory interactions were always terminated by females, and in every case males had already formed a spermatophore when deserted by females. We conclude that variation in male repeated mating success may be due to female choice rather than an inability or unwillingness of low-diet males to produce spermatophores.     

浸提条件对小麦秸秆中化感物质检测结果的影响

通过对比不同浸提条件下小麦秸秆中化感物质的检测结果,发现浸提温度和时间对化感物质的最终结果有很大的影响,在室温条件下,化感物质的量随着浸提时间的延长而增长,但在50℃时,随着浸提时间的延长,化感物质的量反而降低。化感物质最大量在50℃,24h浸提条件下得到。在高温高压条件下提取到的化感物质的量多于多数条件下得到的量（除少于50℃,24h浸提条件下得到的量）。试验结果表明随着漫提温度升高,植物材料中的化感物质在水中的溶解速度加快,但是性质不稳定,容易分解变性。     

IGF-1 concentration patterns and their relationship with follicle development after weaning in young sows fed different pre-mating diets

Piglet birth weight and within-litter birth weight variation are important for piglet survival and growth. Pre-mating diets may improve IGF-1 and follicle development during the weaning-to-oestrus interval (WEI) and subsequent piglet birth weight. The objective of this study was to modulate IGF-1 concentration during late lactation and the WEI of young sows by using specific pre-mating diets supplemented with microfibrillated cellulose (MF), l-carnitine (LC) or l-arginine (AR). A further objective was to investigate the relationship between IGF-1 and subsequent follicle development and oestrus and ovulation characteristics. In total, 56 first-parity and 20 second-parity sows in three consecutive batches were used for this experiment. Sows received daily either wheat (CON) or wheat plus MF, LC or AR at one of two supplementation levels (low and high) during last week of lactation and WEI. From weaning onwards, follicle and corpus luteum (CL) diameters were repeatedly measured with ultrasound. Blood samples were collected during the WEI for IGF-1 and on day 21 of pregnancy for progesterone analyses, respectively. Insulin-like growth factor-1 concentration, follicle diameter, oestrus and ovulation characteristics and CL diameter were not affected by pre-mating diets. Low IGF-1 class (≤156 ng/ml, N = 22) sows had smaller follicles at weaning (3.5 v. 3.8 mm, P < 0.05) and a longer weaning-to-ovulation interval (147.2 v. 129.8 h, P < 0.05) than high IGF-1 class sows. In first-parity sows, high loin muscle depth (LM) loss sows (≥8%, N = 28) had lower IGF-1 concentrations at weaning (167 v. 214 ng/ml, P < 0.05) compared to low LM loss sows (<8%, N = 28). However, after weaning, IGF-1 concentrations increased and did not differ between high LM loss and low LM loss sows. In conclusion, the different supplemented compounds in pre-mating diets did not improve IGF-1 concentrations around weaning in young sows. Furthermore, high body condition loss caused lower IGF-1 concentrations at weaning, but these levels rapidly recovered after weaning and were related to follicle development and the interval from weaning to ovulation.     

Thermal ecophysiology of a native and an invasive gecko species in a tropical dry forest of Mexico

For ectotherms, thermal physiology plays a fundamental role in the establishment and success of invasive species in novel areas and, ultimately, in their ecological interactions with native species. Invasive species are assumed to have a greater ability to exploit the thermal environment, higher acclimation capacities, a wider thermal tolerance range, and better relative performance under a range of thermal conditions. Here we compare the thermal ecophysiology of two species that occur in sympatry in a tropical dry forest of the Pacific coast of Mexico, the microendemic species Benedetti's Leaf-toed Gecko (Phyllodactylus benedettii) and the invasive Common House Gecko (Hemidactylus frenatus). We characterized their patterns of thermoregulation, thermoregulatory efficiency, thermal tolerances, and thermal sensitivity of locomotor performance. In addition, we included morphological variables and an index of body condition to evaluate their effects on the thermal sensitivity of locomotor performance in these species. Although the two species had similar selected temperatures and thermal tolerances, they contrasted in their thermoregulatory strategies and thermal sensitivity of locomotor performance. Hemidactylus frenatus had a higher performance than the native species, P. benedettii, which would represent an ecological advantage for the former species. Nevertheless, we suggest that given the spatial and temporal limitations in habitat use of the two species, the probability of agonistic interactions between them is reduced. We recommend exploring additional biotic attributes, such as competition, behavior and niche overlap in order assess the role of alternative factors favoring the success of invasive species.     

USE OF BIOELECTRICAL IMPEDANCE ANALYSIS TO ASSESS BODY COMPOSITION OF SEALS

Abstract: Bioelectrical impedance analysis (BIA) measures resistance and reactance of a current as it passes through an organism. The validity of using BIA as a tool to measure body water content, and hence body composition and condition, was tested on harp and ringed seals. The resistance and reactance readings from BIA were compared to estimates of total body water (TBW) determined via tritiated water dilution. The relationship between resistance and TBW (% of body mass) was linear after logarithmic transformation and the two variables were highly correlated. We describe the electrode configuration and placements which provide reliable results in these seals. Our findings indicate that BIA has considerable potential as an inexpensive, rapid, and reliable technique for estimating body composition of phocid seals.     

Biodegradation of gasoline and BTEX in a microaerophilic biobarrier

Continuous bioremediation of gasoline-contaminatedwater in a packed-bed biobarrier system underoxygen-limited conditions is discussed. This studywas part of an extensive effort to develop analternative technology for the in situbioremediation of hydrocarbons where there is alimited supply of oxygen. Protruded stainless steelpieces and granulated peat moss were used as packingmaterial to support microbial growth in twobiobarriers. The inoculum was an enrichment culture ofan indigenous microbial population from a soil sample.The biobarriers' inlet gasoline concentrations and thelinear liquid velocities were similar to thosecommonly found at in situ conditions. Gasolineremoval efficiencies ranged from 94% to 99.9% in thestainless steel-packed biobarrier, and from 86.6% to99.6% in the peat moss-packed biobarrier. Effluentgasoline concentrations below 0.03 mg/l were obtainedat gasoline loading rates less than 27.5 mg/l.d in thestainless steel-packed biobarrier. The remainingfraction of gasoline in the effluent consisted mainlyof three aliphatic compounds and not the aromaticcompounds. Both biobarrier packings supported nearcomplete removal of the most soluble aromatichydrocarbons of gasoline (BTEX) under all theconditions examined. The consumption of sulfate andthe presence of sulfate-reducing microorganismssuggested the presence of anaerobic metabolism duringthe degradation of gasoline. Up to 92% gasoline wasremoved during the first 3 cm of the biobarriers'length.