Hypoxia does not promote naphthalene bioaccumulation in the brown shrimp,Penaeus aztecus

Since increased ventilation is known to be a common strategy used by aquatic animals to cope with hypoxia, we tested in present study the hypothesis that hypoxia can promote the bioaccumulation of naphthalene, a representative polycyclic aromatic hydrocarbon (PAH), in Penaeus aztecus, a penaeid shrimp subject to hypoxia and PAH contamination in the northern Gulf of Mexico. For each of the two naphthalene concentrations, five groups of shrimps were, respectively, subjected to five different conditions, namely, clean seawater under normoxia, seawater containing acetone under normoxia and hypoxia, and seawater containing 10 or 250 μg/L naphthalene under normoxia and hypoxia. Our results suggest that hypoxia does not significantly alter naphthalene bioaccumulation in either the gills or the hepatopancreas of P. aztecus. The absence of a promoting effect of hypoxia on naphthalene bioaccumulation is attributed to the increased disposition of naphthalene when the shrimps are subjected to hypoxia.     

Hypoxia does not promote naphthalene bioaccumulation in the brown shrimp, Penaeus aztecus

Since increased ventilation is known to be a common strategy used by aquatic animals to cope with hypoxia, we tested in present study the hypothesis that hypoxia can promote the bioaccumulation of naphthalene, a representative polycyclic aromatic hydrocarbon (PAH), in Penaeus aztecus, a penaeid shrimp subject to hypoxia and PAH contamination in the northern Gulf of Mexico. For each of the two naphthalene concentrations, five groups of shrimps were, respectively, subjected to five different conditions, namely, clean seawater under normoxia, seawater containing acetone under normoxia and hypoxia, and seawater containing 10 or 250 microg/L naphthalene under normoxia and hypoxia. Our results suggest that hypoxia does not significantly alter naphthalene bioaccumulation in either the gills or the hepatopancreas of P. aztecus. The absence of a promoting effect of hypoxia on naphthalene bioaccumulation is attributed to the increased disposition of naphthalene when the shrimps are subjected to hypoxia.     

Regional variations in trace element concentrations in tissues of black tiger shrimp Penaeus monodon (Decapoda: Penaeidae) from South Vietnam

The goal of the present study was to examine the specific bioaccumulation of 22 trace elements in muscle, exoskeleton and hepatopancreas of black tiger shrimp Penaeus monodon from the Mekong River Delta (MRD), and the South Key Economic Zone (SKEZ), South Vietnam. The general tendency in most trace element concentrations among different tissues were hepatopancreas > exoskeleton > muscle. Comparisons of trace element levels in tissues between the two regions showed that concentrations of Se in muscle and As in all three tissues were higher in SKEZ; whereas in MRD, the higher concentrations of most elements such as Mn, Cu, Cd, Ba, Hg, were observed in tissues. These geographical variations in trace element levels may reflect the differences in human activities between the two regions of South Vietnam. The target hazard quotient (THQ) values for trace elements (<1) indicate that local residents are not exposed to potential health risks via the consumption of shrimp.     

Use of the clam Asaphis deflorata as a potential indicator of organochlorine bioaccumulation in Hong Kong coastal sediments

In order to test its ability as a bioaccumulator, the deposit feeding clam Asaphis deflorata, collected from a clean coastal area in Hong Kong (Ding Chau, Ma On Shan), was exposed to field-collected sediments representing a gradient of contamination. Sediments were collected from four sites, namely Shek O in the southeast of Hong Kong Island, Ap Lei Chau in Aberdeen district, Tai Kok Tsui in the Mong Kok waterfront, and To Kwa Wan near Kowloon City pier. Shek O was the cleanest and To Kwa Wan was the most polluted site. Replicate 30 L fiberglass tanks containing equal numbers of organisms were maintained for 28 days, with equal quantities of sediment and filtered seawater. Prior to this the animals were depurated for 10 days in clean sediment. During the 28-day holding period, sampling of both sediment and clams was performed on days 0, 10 and 28, along with condition index measurements. Concentrations of organochlorine pesticides and PCBs in sediments showed that Shek O was the cleanest of the sites, followed by Ap Lei Chau, Tai Kok Tsui and To Kwa Wan. There were marked differences among the sites, especially in PAH concentrations, with To Kwa Wan showing extremely high sediment concentrations.Following exposure, the biota concentrations of various organochlorine pesticides and PCBs suggested that there was sediment concentration-dependent accumulation by A. deflorata on day 10 of the experiment. However, there was no significant increase on day 28 for any of the compounds tested. Contaminant concentrations in clams feeding on Shek O sediments were minimal and almost the same on all sampling days, indicating the presence of only baseline contaminant concentrations. The condition indices (CI) of the clams on various sampling days showed that the animals were relatively more stable in sediment from Shek O. There were some deaths in all the test tanks (including those containing Shek O sediments). In addition, clams appeared to bury faster in the cleaner Shek O sediment and remained buried, unlike those in the sediment from the other locations, where some remained predominantly on the surface. Nevertheless, despite not completely burying, the clams in other test sediments still exhibited sediment concentration-dependent tissue accumulation. The results of the investigation indicate the possibility of developing a standard test protocol for bioaccumulation by sediment dwelling invertebrates, for practical use in Hong Kong, using A. deflorata.     

Effects of 4-nonylphenol exposure in mussels (Mytilus galloprovincialis) and crabs (Carcinus aestuarii) with particular emphasis on vitellogenin induction

Since it is often difficult to estimate possible adverse effects due to contamination in selected ecosystems, multi-species biomonitoring may provide more information, taking into account different routes of exposure, ecological roles and metabolic capabilities of animals. In this context, we exposed for 7 days the mussel Mytilus galloprovincialis and the crab Carcinus aestuarii to 4-nonylphenol (NP), a well-known xenoestrogen. In mussels (0–0.2 mg NP l⁻¹), we measured NP bioaccumulation in soft tissues and vitellogenin (Vg)-like protein levels in digestive glands from both males and females by the alkali-labile phosphate assay (ALP). As no reference data were available for crab exposure, the NP 96-h LC₅₀ value was previously determined. Then, in sublethally exposed (0–1.0 mg NP l⁻¹) male crabs, NP bioaccumulation and Vg levels were measured in hemolymph, gonads and digestive gland. Bioaccumulation of NP increased from 43 to 371 μg g⁻¹ d.w. in mussels, and from 3.6 to 37 μg g⁻¹ d.w. in crabs, depending on the NP concentration in water. Dose-dependent Vg-like protein induction was observed in both species, appearing to be related to NP bioaccumulation, although a partial decrease was recorded at the highest concentration tested. A similar trend was observed in both digestive gland and gonad of exposed crabs; Vg increased to a lesser extent, although significantly, in hemolymph. Results demonstrated that NP induces Vg synthesis both in male and female mussels, as well as in male crabs. On the basis of the responsiveness of both species investigated, a multi-species approach is indicated in biomonitoring programmes.     

溯河洄游长江刀鲚(Coilia nasus)摄食虾类的调查

刀鲚(Coilia nasus)是长江的名贵经济鱼类.虽然传统上认为其溯河生殖洄游全过程不会摄食,但该问题一直尚未完全弄清.作为有效解明这一问题的第一步,本研究在前期长江流域干流和湖泊刀鲚资源调查的基础上,先利用耳石微化学技术筛选出长江河口区、江苏江段、安徽江段和鄱阳湖水域溯河洄游型的刀鲚个体,再对其胃、肠容物的大型游泳动物(鱼、虾类)进行调查分析.结果发现,在河口区、江苏和安徽江段所有刀鲚个体胃充塞度为0级,均未发现摄食有游泳动物;而鄱阳湖水域刀鲚个体的胃充塞度达4~5级,均发现有摄食淡水虾类的日本沼虾(Macrobrachium nipponense)和秀丽白虾(Exopalaemon modestus)的情况.其中29%和71%的刀鲚胃中分别含有1只和2只虾.所有刀鲚个体肠内均未发现有内容物.鉴于鄱阳湖已被确定为溯河洄游型刀鲚的产卵场之一,结果表明长江刀鲚在经河口,通过长江江苏和安徽江段干流到达鄱阳湖产卵场的过程中应该不会摄食大型游泳动物;而进入鄱阳湖产卵场后会开始摄食日本沼虾和秀丽白虾.这种两阶段的现象可能反映出了刀鲚的一种在洄游通道上节约能量,以利长距离溯河;而在产卵场补充能量,以利于性腺最终成熟的生存策略.     

Comparative petroleum hydrocarbons levels and biochemical responses in mussels from hydrothermal vents (Bathymodiolus azoricus) and coastal environments (Mytilus galloprovincialis)

Aliphatic hydrocarbons and PAHs in the whole soft tissues of Bathymodiolus azoricus from three Mid-Atlantic Ridge hydrothermal vents (Menez-Gwen, Lucky Strike and Rainbow), and Mytilus galloprovincialis from three contaminated coastal sites in South Portugal were analysed, and its effects on the digestive gland microsomes mixed-function oxygenase system (MFO) were assessed.Aliphatic hydrocarbons levels were present in the same magnitude in both coastal and hydrothermal environments, while the UCM (unresolved complex mixture) for coastal mussels were higher than in vent mussels. In general, significantly higher PAHs concentrations were found in coastal mussels, compared to B. azoricus where low molecular weight PAHs (2–3 rings) represented the majority of PAHs contrarily to what was observed in M. galloprovincialis. The MFO components were present in both mussel species, and were detected in vent mussels for the first time. However this system seems to have different roles in species from these contrasting environments. In coastal mussels MFO responded to hydrocarbon contamination while response in hydrothermal organisms appeared to be related mainly to endogenous factors.     

Cloning and developmental expression of kinesin superfamily7 (kif7) in the brackish medaka (Oryzias melastigma), a close relative of the Japanese medaka (Oryzias latipes)

kif7 is a member of the kinesin superfamily members which are molecular motor proteins that move along microtubules in a highly regulated manner through ATP hydrolysis. In this paper, we report on the cloning of the Oryzias melastigma kif7 (omkif7) using primers designed according to the Japanese medaka (Oryzias latipes) database. The cloned omkif7 has an open reading frame of 3762bp and is deduced to encode a polypeptide of 1254 amino acids that possesses the putative ATP-binding and microtubule-binding motifs in its motor domain at the N-terminal region. We characterized the cloned omkif7 by comparison with the zebrafish kif7. Both omkif7 and zebrafish kif7 are shown to be expressed in all embryonic stages and adult tissues examined with higher expression level in the testis and ovary. Whole-mount in situ hybridization revealed that the expression of omkif7 is ubiquitous during the early stages of embryonic development, but became more restrictive and localized to the brain, fin bud and eye at later development. This study suggested that the brackish O.melastigma can serve as a good seawater model organism for developmental studies by utilizing the resources developed from its close relative of the Japanese medaka.     

Differential piscivory of the native Percichthys trucha and exotic salmonids upon the native forage fish Galaxias maculatus in Patagonian Andean lakes

The present paper analyses predation patterns, of Percichthys trucha and salmonid fish upon Galaxias maculatus in five lakes of northern Patagonia with differing community and environmental characteristics. Tank experiments were performed to evaluate relative efficiency of native and exotic predators of G. maculatus under treatments with and without cover (aquatic vegetation). Important differences were found between predators with regards to distribution and consumption of G. maculatus. Salmonids are more efficient than P. trucha in consuming G. maculatus in deep environments with scarcely vegetation; in contrast to native species they frequently use the pelagic environment. Although pelagic habitat might have served in the past as a refuge from native predators in the past, G maculatus now experiences intense predation in the pelagic zone by exotic salmonids. It is suggested that the widespread distribution of G. maculatus in Patagonian lakes may have facilitated the success of salmonids throughout Patagonia.     

Reproductive traits of the freshwater shrimp Caridina fossarum Heller, 1862 (Decapoda, Caridea, Atyidae) in the Ghomp-Atashkedeh spring (Iran)

In the present study, some biological traits of Caridina fossarum reproduction are studied in the Ghomp-Atashkedeh spring (Fasa, Shiraz, Iran), for the first time. This Iranian endemic freshwater species was studied from April 2007 to March 2008. Minimum sexable size (MSS) and absolute or relative size at the onset of maturity (SOM and RSOM) in terms of carapace length (CL) was found to be 2.4 mm, 4.3 mm and 55%, respectively. Sex ratio showed variations on a monthly basis. Sex reversal is a possible scenario for C. fossarum because the size-specific sex ratio revealed a reverse pattern. Based on the proportions of ovigerous females, the main breeding season was determined to be from April to August, demonstrating a peak during early spring. There is a period of extended recruitment at water temperatures above 20 °C. The size at which 50% of females are mature was estimated at CL = 5.03 mm from the proportion of ovigerous females during the breeding season. The pleopodal egg number varied from 3 to 75 eggs per female with a mean value 34.39 ± 14.27. The results showed that although there is a significant relationship between carapace length CL and pleopodal egg number, it is not the most important factor affecting potential fecundity in C. fossarum due to the low values of slope (= 1.51) and determination coefficient (= 0.052).     

Histopathology alterations and histochemistry measurements in mussel, Mytilus edulis collected offshore from an aluminium smelter industry (Norway)

Histopathological characteristics of specific organs express condition, and represent time-integrated impacts on the organism stemming from alterations at lower levels of biological organisation. As integrative parameters, histochemical investigations have proved to be sensitive tools to detect effects of chemical compounds.The objective of this study was to determine changes in the tissues of mussels collected at a PAH contaminated site compared to a reference site using histopathological and histochemical parameters: lipofuscin (LF) accumulation in mussel digestive gland, and lysosomal membrane stability (LMS), and using additional information provided by body burden analysis to compare the sensitivity of these parameters.The histochemical measurements for both LF and LMS gave a clear indication of a high level of stress in animals from the PAH contaminated site. This LF accumulation in lysosomes is the result of peroxidation of autophagocytosed proteins associated with protein aggregates and oxidatively damaged organelles. These measurements were able to detect the effects of PAHs, and showed a strong relationship with the body burden results.     

Biomarker responses in caged rockfish (Sebastes schlegeli) from Masan Bay and Haegeumgang, South Korea

The purpose of this study was to compare enzymatic biomarker activities in fish caged at two sites, Masan Bay (contaminated) and Haeguemgang (reference). In the present study, ethoxyresorufin O-deethylase (EROD), brain acetyl cholinesterase (bAChE), muscle acetyl cholinesterase (mAChE) and butyryl cholinesterase (mBChE) in caged rockfish (Sebastes schlegeli) were measured 0, 1, 3, 7, 14, 21 and 30 days after caging. The level of CYP1A mRNA and Protein expression was induced higher in Masan Bay at 1, 3, 7, 14 and 30 days after caging. EROD activity in the caged fish was significantly higher in Masan Bay than in Haeguemgang 3 and 7 days after caging, but not at 14 and 30 days after caging. bAChE activity was significantly inhibited at 7 and 14 days after caging in Masan Bay. However, mBChE activity was not significantly inhibited during the experiment. Taken together, the data suggest that the caged fish were exposed, at least transiently, to CYP1A inducers and ChE inhibitors, which is consistent with our previous observations.     

Fungal infection of Eudiaptomus gracilis (Copepoda, crustacea) in Lake Mondsee

An Aphanomyces sp. (Oomycetes) was found to be an important egg parasite of Eudiaptomus gracilis (Copepoda) in Lake Mondsee (Austria). The infection is evidenced by densely packed infection hyphae, attached with holdfasts and wrapped around the female's abdomen. The infection hyphae give rise to hyphae which penetrate the egg sac, and subsequently kill all eggs. The infection obviously has no pathogenetic effects on the egg-carrying female. Infected females appear during summer and fall, mainly in warm water layers. Infected egg clutches are found at all seasons of the year, indicating considerable birth control of the Eudiaptomus population by parasite infection. It seems possible that the actual Aphanomyces sp. is not the only parasite involved.     

Application of the value of nonlinear parameters H and Δ H in strong earthquake prediction

In this paper, the relation that the curves of nonlinear parameter H and its difference ΔH bear with strong earthquakes in North China has been studied. First, the RSH algorithm has been applied to the North China region; the schemes of six quantitative prediction indexes have been studied in detail and then tested by tracing-back predictions. The result shows that all the six prediction schemes are of certain prediction efficiency and have passed the test. Among the six schemes, A and E are of the best effect, with correlation coefficients R of 0.47 and 0.48 respectively. We recommend these two schemes for practical use in prediction in the future. Furthermore, the relation between the curve of ΔH (the difference of H) and strong earthquake has been studied. Based on the above results, the RSΔH algorithm that uses the ΔH value to predict strong earthquake has been put forward and applied to predict strong earthquakes in North China. The correlation coefficient R of tracing-back prediction by this method is 0.45; this means that this method is also of better prediction efficiency. A combined application of these two algorithms has also been proposed. By the combined method, the time length spanned by false predictions can be shortened and thus the R value can be raised. Contribution No. 96A0033, Institute of Geophysics, SSB, China. This project sponsored by the Chinese Joint Seismological Science Foundation.     

近40年来南四湖湿地NDVI变化特征及其控制因子分析

利用Landsat系列卫星的MSS、TM和ETM+遥感数据,计算了研究区的归一化植被指数(NDVI),并以此为湿地植被活动的指标,研究1973 2011年间该湿地植被变化特征及年内季节变化特征,揭示植被活动在年内和年际变化的控制因子以及湿地植被对于气候变化、人类活动和极端干旱事件的响应特征.结果表明:(1)近40年来南四湖湿地植被各个季节的变化特征不尽相同.春季NDVI呈现先降低后增加的特征,主要先后受到研究区围垦、渔业养殖等人为活动和气候变化(增温)的影响;夏季和冬季的NDVI呈现显著降低趋势,主要受到围垦、渔业养殖等人类活动的影响;秋季NDVI的变化不显著.(2)年内季节变化方面,湿地植被面积和NDVI都呈现单峰的变化特征,从春季开始增加,在夏季末(全年的第202和205 d)达到最大值,然后开始下降,到冬季降至最低.植被的年内季节变化特征主要受到月均温度的控制.(3)干旱在一定程度上不是湖泊湿地NDVI增加的限制因子.干旱导致湖泊水位下降,滨湖滩地及湖底露出,可能会促进湿地植被生长和植被面积的扩大,使得湿地NDVI增加.     

冬、春季芦苇(Phragmites australis)和狭叶香蒲(Typha angustifolia)的腐解过程及其对水质的影响

水生植物修复已经成为水体富营养化修复的重要手段,但其周期性的衰亡也给水体带来不容忽视的负效应.以府河流域丘陵地带农业区小水系自然生长的芦苇(Phragmites australis)和狭叶香蒲(Typha angustifolia)为研究对象,通过模拟实验,研究其冬季和春季腐烂分解过程的差异以及对水体营养盐水平的影响.结果表明,2种挺水植物的剩余干物质量整体上都呈现先快速下降再缓慢下降的趋势,芦苇和狭叶香蒲春季的分解速率分别为0.0251和0.0169 d~(-1),分别明显高于冬季分解速率(0.0027和0.0052 d~(-1));且腐烂分解速率与植物初始氮磷含量和氮磷比都有一定相关性.2种植物在冬季和春季磷的矿化速率都明显高于氮的矿化速率.实验水体的总氮和总磷浓度在腐解过程呈现初期迅速上升、中期迅速下降、后期缓慢下降的趋势.总体来看,芦苇和狭叶香蒲的腐烂分解受季节和初始氮磷浓度的影响较大,芦苇反应较香蒲更敏感且对水质的影响具有时效性.     

铁对拟柱孢藻(Cylindrospermopsis raciborskii)和角星鼓藻(Staurastrum spp.)季节动态和生长的影响——以广东大沙河水库为例

拟柱孢藻（Cylindrospermopsis raciborskii）和角星鼓藻（Staurastrum spp.）是热带亚热带浮游植物群落中的常见优势种类,为了解铁对2种浮游植物季节动态和生长的影响,本文通过对典型热带水库的野外调查,分析铁与2种藻生物量和相对生物量的季节动态的关系,并通过室内实验分别以无机磷（KH₂PO₄）和有机磷（C₆H₁₃O₉P）为磷源,比较3种铁浓度（0.029、0.29和0.689 mg/L）下拟柱孢藻（C.raciborskii,N8）和角星鼓藻（Staurastrum sp.,FACHB-1449）的比生长速率、铁载体产量和碱性磷酸酶活性的差异.结果显示,拟柱孢藻和角星鼓藻是浮游植物群落的主要优势种类,两者的生物量最大占到总生物量的82%以上;两者对环境变量响应的区别主要体现在对溶解性铁浓度变化的响应差异上,拟柱孢藻生物量与溶解性铁有显著的线性回归关系,但角星鼓藻的生物量与铁没有显著线性回归关系.室内实验中,拟柱孢藻N8的比生长速率在无机磷源铁浓度为0.689 mg/L条件下最大,为0.098±0.01 d^-1,2种磷源条件下比生长速率均随铁浓度降低而显著降低,6个实验组均检到铁载体：6个实验组角星鼓藻FACHB-1449的比生长速率没有明显差异,平均为0.079±0.001 d^-1,均未检出铁载体,磷源和铁浓度对其比生长速率的影响不显著;有机磷源条件下,拟柱孢藻N8实验组碱性磷酸酶活性均显著高于角星鼓藻FACHB-1449实验组,拟柱孢藻N8实验组酶活性随铁浓度降低而显著降低,但角星鼓藻FACHB-1449各实验组的碱性磷酸酶活性无明显差异.以上结果表明,水体中溶解性铁的供应对拟柱孢藻的种群动态和优势有重要作用,与角星鼓藻相比,拟柱孢藻的生长更易受到铁的限制,尤其在无机磷缺乏、磷源主要以有机磷形式供应时,铁对拟柱孢藻生长的限制作用增强.     

基于离散三维活体荧光光谱法的湖泊水体叶绿素a浓度原位测量

荧光光谱分析技术具有灵敏度高、检测快速等优点,三维荧光光谱提供的指纹荧光信息比普通荧光光谱更丰富,选择性更好,在多组分分离上更具优势.离散三维活体荧光光谱法通过提取水体蓝藻、绿藻、硅藻、甲藻和隐藻5个门类藻类荧光光谱的指纹特征,分类测量藻类叶绿素a浓度,经过加和得到总的水体叶绿素a浓度.将基于该方法研制的三维荧光光谱水体藻类原位测量仪用于太湖水体叶绿素a浓度的测定,并与YSI多参数水质检测仪、BBE藻类现场分析仪、分光光度法等测定结果对比,结果表明:该方法与分光光度法间无显著性差异,与分光光度法、BBE法间的相关性好,相关系数达0.96以上,精密度、准确率优于基于普通荧光法的原位测量仪,是一种快速有效的原位测量方法.     

太湖和巢湖中微囊藻(Microcystis)与长孢藻(Dolichospermum)的长时序变化及其驱动因子

随着我国湖泊治理力度的加大,太湖和巢湖的营养盐水平,特别是氮水平近年来明显下降,如2007年以后太湖总氮和近年来巢湖的氨氮水平都呈现下降趋势,但是2个湖泊水华蓝藻的优势种却向相反的方向演化,太湖的长孢藻(Dolichospermum)比例在增加,而巢湖的长孢藻比例却在降低,为阐明这种变化过程和驱动因素,本研究利用太湖(19932015年)和巢湖(2012 2018年)的历史数据分析了2个湖泊中的水华蓝藻——微囊藻(Microcystis)和长孢藻生物量的历史变化过程,并结合营养盐数据分析了影响2种水华蓝藻变动的驱动因素.结果显示:太湖和巢湖的微囊藻生物量多年来始终保持高位波动,近年来均有升高的趋势,这与2个湖泊磷的高位波动具有明显的相关性,磷是决定微囊藻生物量长尺度变化的主要驱动因素;太湖的长孢藻生物量呈现较大波动变化,2007年以后明显升高,巢湖的长孢藻生物量则明显下降,氮与长孢藻生物量呈现负相关关系,而且这种负相关仅在低磷浓度时具有显著性.微囊藻生物量对磷浓度变化敏感的正反馈响应是其水华形成的重要机制之一,在高温高磷条件下,微囊藻可以快速繁殖,并竞争性排除长孢藻,从而形成优势;而长孢藻可以通过温度生态位和固氮两种方式占据优势,在氮浓度相对较低,且温度低于微囊藻形成水华的温度范围时,长孢藻可以依靠温度生态位的优势形成水华,而在氮限制的条件下,即使在夏季高温时,长孢藻依然可以利用固氮作用形成水华,但是关键的温度阈值和开始固氮的氮浓度阈值仍不清楚.基于2种水华蓝藻对营养盐变化响应的差异,建议在进行蓝藻水华治理、污染削减过程中,应针对不同水华蓝藻的特性进行分时段分类别的营养盐控制策略.     

Effect of prolonged hypoxia on food consumption, respiration, growth and reproduction in marine scavenging gastropod Nassarius festivus

The effects of prolonged exposure to reduced oxygen levels (3.0 and 1.5 mg O₂ l⁻¹) on marine scavenging gastropods Nassarius festivus were studied for 8 weeks. The percentages of individuals engaged in feeding and amount of food consumed were reduced as oxygen level decreased; absorption efficiency, however, did not vary significantly with oxygen level. Oxygen consumption rates and specific oxygen consumption rates were lower at reduced oxygen levels. Reproduction occurred at all oxygen levels with less egg capsules being produced at lower oxygen levels. Egg size and number of eggs per capsule, however, were not significantly affected by oxygen level. The increase in shell length was 12%, 6% and 5% at 6.0 mg O₂ l⁻¹ (normoxia), 3.0 mg O₂ l⁻¹ and 1.5 mg O₂ l⁻¹, respectively. At the end of the experiment, the amount of energy allocated to growth and reproduction decreased at reduced oxygen levels with values obtained at 3.0 mg O₂ l⁻¹ and 1.5 mg O₂ l⁻¹ being 48% and 70% lower than those at 6.0 mg O₂ l⁻¹. At all oxygen levels, most of the accumulated energy was allocated to shell growth and reproduction, and the amount allocated to somatic growth was relatively insignificant. The reduction in energy allocated to reproduction was greater than that to shell growth as the oxygen level was reduced, indicating a strategic energy allocation of marine scavengers under stressful conditions to enhance survival.