Development of cell types in the pituitary of Anguilla anguilla,Pleuronectes platessa and Limanda limanda

Pituitary cell types have been studied by application of specific histochemical methods. Identification of cell types in the fishes Anguilla anguilla, Pleuronectes platessa and Limanda limanda at different seasons and maturity stages is based on both tinctorial and structural characteristics of different cell types; their granulation, state of vacuolation, condition of the nucleus and presence or absence of the nucleolus. Gonads from fish caught monthly were also prepared for histological examination to determine their maturity stage and sex. Female A. anguilla at maturity stages II and III, and yellow in all external morphological characters, were used. A general cytohistological study of the pituitary gland during the annual cycle has been carried out with the aim of discovering (a) the causes of the longterm growth, and (b) the pituitary's physiological control of the fishes' metamorphosis. Variations in number and activity of the cell types to be found in the meso adenohypophysis have been investigated by cell counts of representative medial sagittal sections of the pituitary during different months. somatotrophs show short-term fluctuations, but gonadotrophs show an alternating cycle of increase and decrease. Chromophobes do not show much change in their number during the annual life-cycle. Basophils are found in all 3 lobes of the adenohypophysis and exhibit very little structural difference, so that a common function for all 3 cell types may be assumed. Observations on variations in concentration of neurosecretory material have been made; peak accumulation of neuroscretory material occurs between August and October and then remains almost constant up to December. This periodic increase suggests that neurosecretory substances have an influence upon the animal's metabolic activities. Studies in relation to the maturation cycle carried out on monthly samples of male and female P. platessa and L. limanda regarding the percentage, relative numbers and state of activity of chromophobes, somatotrophs and gonadotrophs produced results which appear to agree with the functions suggested for each cell group; their variation in number and activity keeps pace with corresponding maturity phases. Somatotrophs predominate in all maturity stages in both sexes. Chromophobes exhibit a cyclic increase and decrease; few are present in ripening gonads, many in spawning individuals. Gonadotrophs show a relative increase in number during gonadal ripening. Active and inactive gonadotrophs are identifiable at all maturity stages. The eel pituitary size is independent of both length and weight; however, for P. platessa pituitary size is related to weight, which is (in part) dependent upon the maturity stage. Implications of variations in relative proportions of cell types are discussed with regard to present knowledge of the pituitary gland.     

Effect of Dimethoate (Rogor 30% EC) on the brain neurosecretory cells of third instar grubs of Oryctes rhinoceros L. (Coleoptera : Scarabaeidae)

The brain neurosecretory cells of III instar grubs of Oryctes rhinoceros were exposed to insecticide Dimethoate (Rogor 30% EC) in the laboratory condition. The sublethal doses (0.125, 0.25 and 0.5%) of Rogor at time intervals of 8, 16 and 24 h have produced marked changes in the structure and the secretory activities of medial and lateral neurosecretory cells. Rogor stimulates the synthetic activity of these cells at the initial stages of its action and results in the accumulation of neurosecretory materials (NSM) in the cytoplasm. The decreased neurosecretion at later stages of the action was due to its transportation through the axons before the death of treated grubs. Similarly, vacuolization, shrinking and degeneration of cells were also observed in treated grubs.     

Histological changes of the digestive epithelium in <Emphasis Type="Italic">Calanus finmarchicus</Emphasis>: an index for diapause?

Samples collected in the Irminger Basin during the Marine Productivity Programme (2001–2004) were used to study Calanus finmarchicus vertical distribution and histological changes of its mid-gut epithelium in relation to overwintering strategy. Previous studies have shown that cell composition of the glandular part of the mid-gut, size and abundance of B cells responsible for digestive enzyme secretion and thickness of the epithelium could be good indicators of individual physiological state. We used C. finmarchicus abundance, vertical distribution, lipid sac volume and mid-gut epithelium histological composition of individuals collected in contrasting hydrographic areas of the Irminger Basin and sampled at different seasons to understand C. finmarchicus life cycle in the Irminger Basin. Lipid sac volumes were significantly different between the seasons but neither between the hydographic areas nor the various depths of the water column. B cells concentrations and thickness of the epithelium have allowed us to distinguish a non-diapausing surface population (350 m) in the East Greenland Current while individuals at depth (1,250 m) were overwintering. This result is correlated by a bimodal vertical distribution of the CV in this biozone. In the other hydrographic areas, all CV were dormant, although surface individuals were not analysed in the Southern Irminger Current.     

A study of a sustainable greenway approach for a part of the Silk Road in Turkey

The article describes different steps and methodologies to create an alternative greenway with recreational, scenic, historical and cultural values in Hamsiköy-Zigana, part of Trabzon-Gümü?hane former state highway. As a first step, inventory studies and analyses were carried out to determine the cultural and natural values of the area. As the second step, area analyses studies were carried out. Depending on results of expert-based visual assessment and suitability analyses for determining the suitability of greenway planning in the study area; recreational, scenic, historical–cultural and multifunctional status of the greenway having all these three functions at the same time were mapped using suitability rank in GIS and the plan square technique. As a result, the plan squares having high suitability for the above functions were dense in the determined study, in terms of old highway and neighbourhood. In the whole area (4385.25 ha), 598.00 ha were ranked as good (A), 770.27 ha as medium (B) and 3016.98 ha as poor (C), in terms of suitability value. Seasonal assessments for recreation and scenery functions of A, B and C indicate that the area has opportunities for all seasons. As a third step, the results are discussed and some proposals suggested.     

Seasonal variation of soil carbon and nitrogen under five typical Pinus massoniana forests

Five different typical Pinus massoniana forests were sampled in the Guizhou Province to evaluate the effects of seasons on soil organic carbon (SOC), total nitrogen (STN), and inorganic nitrogen (SIN) in these forests. More seasonal variation occurred in the topsoil than in lower layers. The SOC and STN contents varied the least amongst the soil layers, but the SIN contents had the largest values and ranges during autumn. Carbon-to-nitrogen ratio (C/N) exhibited neither a vertical change nor a seasonal trend. C/N was either maximal or minimal depending upon the sites during autumn, indicating that ecological process during summer soils would strongly change this. More gravel content resulted in higher litter stock, SOC, and STN level in low-productivity forests. A low phosphorus level might result in low SOC and STN contents in clay-rich soils. Low litter stock and clay content will result in low SOC and STN levels in coniferous and broad-leaved mixed forests in contrast to pure forests. The SOC and soil N contents in P. massoniana forests are apparently affected by different sampling seasons, particularly in topsoil. This should be taken into account when evaluating C and N contents and their respective storages in other forest types.     

Variations in the progress of 14C uptake as a source of error in estimates of primary production

The progress curves of ¹⁴C retention for samples of phytoplankton from the Irish Sea incubated at contrasting light intensities have been obtained by two methods. The first method (A) involved the incubation of the samples for various periods up to 6 h, while the second method (B) consisted of making a series of short-term incubations over the same 6 h period. Over this period, the cumulative uptake was tenerally less when estimated by Method A than by Method B. The difference was greater in the samples incubated at the lower light intensity, the light history of the samples having no effect on the difference. The differences has a kinetic basis, with two combinations of progress curves obtained by use of the two methods. The first combination was associated with samples collected in the early morning, while the second combination was exhibited by samples taken in the afternoon irrespective of sampling depth. In certain samples, no increase in the ¹⁴C retained by the cells as measured by Method A was observed after 4 h. The cumulative retention of ¹⁴C by the cells after 2 h was generally greater when estimated by Method A than by Method B, this situation being reversed after 4 h. This reversal indicated a change in uptake kinetics between 2 and 4 h and it is suggested that this interval represents the time necessary for the ¹⁴C to work through the cellular pool of carbon. The findings are discussed in relation to the methodology for obtaining both estimates of primary production and ¹⁴C uptake-light intensity curves for marine phytoplankton.     

Field identification of ‘types’ A and B of the ascidian Ciona intestinalis in a region of sympatry

The ascidian species Ciona intestinalis is a major model chordate in developmental and evolutionary biology, and an important fouling organism and invasive species. However, genomic investigation has recently revealed the existence of two cryptic species, genetically distinct yet without obvious morphological differences, currently referred to as types A and B. Here, we show that they are externally distinctive in a zone of sympatry in the western English Channel. Examining genotyped specimens, we found that types A and B of C. intestinalis can generally be distinguished by body colour, pigmentation at the distal end of the siphons and the presence or absence of tubercles on the sides of the siphons. Detecting specimens of hybrid descent still requires detailed molecular analysis, but these visual characters in combination will identify living specimens of types A and B with high probability. These differences are shown to be inherited.     

Three-dimensional fluorescence spectral characterization of soil dissolved organic matters in the fluctuating water-level zone of Kai County, Three Gorges Reservoir

Three-dimensional fluorescence spectroscopy was used to investigate the fluorescent properties of soil dissolved organic matter (DOM) in the water-level-fluctuation zone (WLFZ) of Kai County, Three Gorges Reservoir (TGR). Most of the soil DOM analyzed in this study was found to contain four fluorescence peaks. Peaks A and C represent humic-like fluorescence, whereas peaks B and D represent tryptophan-like fluorescence. Peaks E and F, which represent tyrosine-like fluorescence, only appeared in certain soils. Soil humus was the main source of DOM in soil, and higher concentration of soil DOM was found in the exposed soil than submerged soil. Compared to the peaks A and B, the fluorescence intensities of peaks C and D were strongly influenced by the fluctuating water level. Analysis of fluorescence intensities of different peaks in soil DOM showed that WLFZ soil was not contaminated significantly. Soil DOM contained at least two types of humic-like fluorescence groups and two types of protein-like fluorescence groups. The proportion of the content of peak A in soil organic matter was quite stable. The soil DOM in exposed soil had relatively high humification and aromaticity, and periodic submerging and exposure of soil had an impact on the humification of soil DOM.     

Histochemical and ultrastructural characterisation of mantle storage cells in the hydrothermal-vent bivalve Bathymodiolus azoricus

This study reports on two types of storage cells that are present in the mantle connective tissue of the deep-sea mussel Bathymodiolus azoricus. One type corresponds to the adipogranular cells, a kind of storage cell previously described in other bivalves. In these cells extensive regions of the cytoplasm are filled with glycogen deposits and these zones became strongly stained after histochemical (PAS) or ultrastructural detection of polysaccharides. Several lipid droplets and membrane bound granules containing homogeneous electron-dense material are also present in adipogranular cells. A second type of cell contains large lysosomes in addition to numerous lipid droplets, but lacking cytoplasmic glycogen deposits. Due to these characteristics we named them adipolysosomal cells. They can be identified in semi-thin sections stained with PAS reaction because the lysosomes are the only positively stained structures. In the connective tissue of the mantle, some cells containing many lysosomes and a few lipid droplets were also observed. These cells differ from the adipolysosomal cells mainly because they have a reduced amount of lipid reserves, and could be an initial stage in the development of adipolysosomal cells. The vesicular connective tissue cells that in other Mytilidae are specialised in glycogen storage were not detected in B. azoricus. The reserves accumulated in the two types of storage cells described in B. azoricus may be important for the survival of these hydrothermal-vent bivalves if their nutrition is affected by a temporary loss or reduction of endosymbiotic bacteria due to sulphide and/or methane shortage caused by oscillations in vent activity.     

Importance of cysts in the population dynamics of the red tide flagellate Heterosigma akashiwo (Raphidophyceae)

To elucidate roles of cysts in occurrences of Heterosigma akashiwo blooms, cyst dynamics were studied in northern Hiroshima Bay, the Seto Inland Sea of Japan, where H. akashiwo regularly forms red tide in June. Monthly measurements of seasonal changes in the densities of vegetative cells of H. akashiwo and their germinable cysts in surface sediments (top 1-cm layer) were made for 2 years at three stations. Vegetative cells of H. akashiwo could be detected from April through December throughout the water column, and the existence of vegetative cells was confirmed in surface waters even in winter after incubation of sampled seawater in culture medium. Germinable cysts, enumerated by the extinction dilution method, existed in sediments in all seasons, even before and after the seasonal bloom. The effects of incubation temperature on the germination of natural cysts of H. akashiwo in sediments were examined. Germination was not observed at 5 °C, was low at 10 °C, while it increased at 15 °C, and maintained a high level to 25 °C. The bottom water temperature reached 15 °C (suitable for the germination of cysts) and the surface about 18 °C or more (suitable for the growth of vegetative cells) 2 to 3 weeks before the blooms. The dark survival of H. akashiwo cysts was tested, and it was found that the cysts were viable for at least 650 d at 11 °C, and for 165 d at 25 °C, indicating a significant role of cysts in the survival during winter and summer seasons. The cysts presumably also play an important role in seeding primary populations into water columns when the bottom water reaches a suitable temperature (around 15 °C); thereafter the populations develop with great annual regularity to bloom in June. These results suggest that initiation of H. akashiwo red tides in the Seto Inland Sea could be triggered by bottom water temperature. Received: 3 July 1998 / Accepted: 12 January 1999     

Ultrastructural observations on prey capture and digestion in the scyphomedusa Aurelia aurita

Aurelia aurita medusae are able to catch their prey with their entire body surface. Catch efficiency in medusae caught in Kiel harbour in May 1985 was found to be highest at the tentacles and lowest at the subumbrella. Surface structures of the medusa as well as the cnidom are described by SEM observations. Microbasic heterotrichous euryteles and atrichous isorhizas were found. Discharged nematocysts on the prey's skin indicate different functions of the two types. The villi in the gastral cavity show a characteristic morphological differentiation that consists of a ciliated distal and a basal area covered by vesicles. Four types of glandular cells were identified by TEM observations. Mucous cell types preferably occur in densely ciliated areas. The presence of serous cells is restricted to the basal region of the gastral villi and gastral cavity where the extracellular predigestion takes place. The time of food passage in young medusae of A. aurita decreases from 19 h at 4°C to 4 h at 22°C.     

Seasonal fluctuations in sand temperature: effects on the incubation period and mortality of loggerhead sea turtle (<Emphasis Type="Italic">Caretta</Emphasis><Emphasis Type="Italic">caretta</Emphasis>) pre-emergent hatchlings in Minabe,Japan

Incubation period, hatching success, and emergence percentage in loggerhead (Caretta caretta) nests were quantified during the 1993 and 1995 nesting seasons and following incubation seasons in Minabe, Wakayama, Japan. Sand and nest temperatures were also monitored. Over the seasons, daily mean sand temperature at nest depth fluctuated between 18.0°C and 33.3°C, with a steep increase in the second week of July and a peak in late August. Temperatures inside the nest chambers were a few degrees above those of the surrounding sand at the end of incubation. The incubation period ranged from 46 to 82 days. A significant negative correlation was found between mean sand temperature and incubation period. The relationship conformed to the day-degree concept. There was no significant seasonal trend in hatching success, but many pre-emergent hatchlings were found dead in most of the clutches during the warmest part of the season. Emergence percentage was correlated with mean sand temperature calculated for 4 days before emergence, suggesting that mortality may be due to heat. This heat-related mortality is considered to be a common phenomenon at our study site, because the peak in emergences coincides with the peak in high temperatures. These temperature effects on hatchling mortality must be taken into account in estimates of hatchling sex ratios. Because sand temperatures already exceed the optimal thermal range for incubation, this population is vulnerable to even small temperature increases resulting from global warming.     

沿海三市饮用水源水内分泌干扰毒性研究

近十多年来,江苏沿海化工产业发展迅速,化工废水的长期排放对水生生态系统及人群健康构成潜在威胁.采用非洲猴肾细胞(CV-1)核受体介导的体外转录激活试验方法,对中国东部沿海A、B、C三市的6个水源地进行了拟雌激素活性调查研究.结果表明:C市2处水源水的有机提取物在枯水期、平水期和丰水期均无拟雌激素活性检出,水质较好;A市...     

The effect of chronic formaldehyde exposure on the hippocampus in chronic cerebral hypoperfusion rat model

The aim of this study was to evaluate the effect of chronic formaldehyde (FA) exposure on the hippocampus in the chronic cerebral hypoperfusion rat model. Seventy-two male Sprague-Dawley rats were randomly divided into four groups: (A) sham-operated bilateral common carotid artery occlusion (BCCAO) with room air inhalation, (B) BCCAO with room air inhalation, (C) sham-operated BCCAO with FA inhalation at a concentration of 10?mL?vapor?m^?3, 1?h per day for 90 days, and (D) BCCAO with FA inhalation. Decreased mobility, injected conjunctivae, and overreaction were observed in groups C and D rats after 30 days of FA exposure. The level of malondialdehyde (MDA) increased significantly in group D at 90 days after FA exposure. The expression of Bax protein increased, while Bcl-2 and NR2B proteins decreased significantly in group D compared to group B or C. Neuronal nuclear antigen (NeuN) positive cells decreased significantly in group D. Neuronal loss, oxidative stress, and the expression of proteins were more prominent at 90 days after FA exposure, especially in group D. Oxidative stress-induced neuronal damages in the hippocampus may be a possible mechanism of neurotoxicity as a result of chronic FA exposure. Chronic exposure of FA caused more neuronal damage in the chronic cerebral hypoperfusion rat model.     

不同施肥模式对华北平原小麦-玉米轮作体系产量及土壤硝态氮的影响

为了探索培育高产粮田的施肥模式,实现氮肥资源的高效利用与环境效益,以华北平原的小麦（Triticum aestivum）-玉米（Zea mays L.）轮作体系作为研究对象,通过2007─2011年4个轮作季,探讨不同的施肥模式对作物产量和土壤硝态氮的影响。试验以处理A（当地传统管理）作为对照,从测土确定施肥量、按作物生长发育明确施肥时期、合理分配各时期的养分配比及增施有机肥等方面改变传统施肥模式,设置3种高产施肥培育模式,分别为处理B（现有高产田推荐管理）、处理C（高肥料投入管理）和处理D（水肥高效管理）,进行田间小区试验。4个轮作季的总产量以处理D为最高,达75430 kg·hm-2,其次是处理C为75166 kg·hm-2,当地传统的产量最低。冬小麦季的吸氮量为处理C和D显著高于A处理,分别高出444.78 kg·hm-2和310.20 kg·hm-2,但与处理B无显著差异;处理D在夏玉米季的吸氮量为776.75 kg·hm-2,显著高于处理A。处理B的氮肥偏生产力值最高为38.21,处理D为36.71,处理A和C均为28.33。各处理经过4个轮作季后,土壤硝态氮均在120-160 cm出现累积峰,A、B、C和D的硝态氮峰值分别为58.65、28.98、105.89、45.29 mg·kg-1。在0-100cm土层,处理B的硝态氮累积量达到144.22 kg·hm-2,显著高于处理A、C、D;所有处理在100-200 cm土层均出现较高的硝态氮累积,处理C高达1021.19 kg·hm-2;0-400 cm的土壤硝态氮累积量分别为724.27、711-92、1324.30、730.70 kg·hm-2。处理A、B、C、D在耕层土壤氮素的表观损失分别为1298.95、653.18、1236.39和718.43 kg·hm-2,处理B、D显著低于处理A、C,D和B间差异不显著。因此,处理D是培育高产的理想施肥模式,合理的施肥量、科学的施肥时期以及有机无机的合理配比是达到高产、提高肥效和环境友好的关键。     

稀土矿城市不同季节大气可吸入颗粒物中稀土含量特征及颗粒物细胞毒性

为探讨典型稀土矿城市不同季节大气可吸入颗粒物(inhalable particulate matter,PM10)中稀土元素污染特征及其细胞毒性响应,将前期采集于包头市的PM10颗粒物进行提取,检测PM10中的稀土元素(rare earth elements,REEs)含量,并将人肺上皮细胞(A549)暴露于不同浓度水平(25,50,100μg·m L-1)的PM10样品和标准颗粒物1649b(standard reference material,SRM1649b)暴露液,用WST-1法测定暴露24 h后的细胞活性,用2’7’二氯荧光素二醋酸盐(2’7’-dichlorofluorescein diacetate,DCFH-DA)荧光探针法和彗星实验分别测定暴露3 h后的细胞内活性氧(reactive oxygen species,ROS)产生水平和DNA双链损伤程度。结果表明,包头春、夏季大气PM10和SRM1649b均引起A549细胞活性下降,并诱导细胞内ROS生成量增加,造成显著的细胞内DNA损伤,含REEs的大气颗粒物毒性显著高于标准颗粒物。与春季相比,包头夏季PM10对细胞活性的抑制程度更高,造成更多的DNA双链损伤,从而表现出更强的细胞毒性和遗传毒性。包头PM10呈现明显的轻稀土元素(light rare earth elements,LREEs)富集,铈(Ce)、钷(Pm)、镧(La)和钕(Nd)含量占稀土总量的50%以上。LREEs均与细胞活性和细胞内ROS产生水平呈负相关性,包头春季和夏季PM10中稀土元素含量的差异是导致包头PM10细胞毒性效应不同于标准颗粒物且具有季节性差异的原因之一。     

镉诱导仔猪睾丸支持细胞氧化酶活性降低及DNA损伤的研究

以仔猪睾丸支持细胞为实验模型,采用二步酶消化法分离支持细胞进行培养。探讨了0、10、20、40、80gmol·L^-1的氯化镉对支持细胞的毒性作用。结果表明：10gmol·L^-1以上的氯化镉有抑制支持细胞生长的作用,并能使支持细胞氧化酶活性下降,造成支持细胞DNA损伤。     

The alarm call system of wild black-fronted titi monkeys, <Emphasis Type="Italic">Callicebus nigrifrons</Emphasis>

Upon encountering predators, many animals produce specific vocalisations that alert others and sometimes dissuade the predators from hunting. Callicebus monkeys are known for their large vocal repertoire, but little is known about the function and meaning of most call types. We recorded a large number of natural predator responses from five different groups of black-fronted titi monkeys in their Atlantic forest habitat in South Eastern Brazil. When detecting predatory threats, adult group members responded with call sequences that initially consisted of two brief, high-pitched calls with distinct frequency contours. Call A was mainly given to raptors but also to predatory capuchin monkeys and other threats within the canopy, while call B was given to predatory or non-predatory disturbances on the ground. In later parts of the sequences, we also recorded a high-pitched unmodulated call C and various low-pitched loud calls. Results therefore suggest that calls A and B provide listeners with rapid and reliable information about the general classes of danger experienced by the caller, while obtaining more specific information through other call types and combinations and behavioural responses. We discuss these findings in relation to current evolutionary theory of primate communication.     

Decontamination efficiency and root structure change in the plant-intercropping model in vertical-flow constructed wetlands

Subtropical climatic conditions can contribute to the death of the aerial parts of constructed wetland plants in winter. This presents a barrier to the widespread application of constructed wetland and is an issue that urgently needs to be solved. Three contrasting experi- ments, the plant-intercropping model （A）, the warm- seasonal plant model （B）, and the non-plant model （C）, were studied in terms of their efficiency in removing pollutants, and the change in root structure of plants in the plant-intercropping model within the vertical-flow con- structed wetlands. The results indicate that model A was able to solve the aforementioned problem. Overall, average removal rates of three pollutants （CODcr, total nitrogen （TN） and total phosphorous （TP）） using model A were significantly higher than those obtained using models B and C （P 〈 0.01）. Moreover, no significant differences in removal rates of the three pollutants were detected between A and B during the higher temperature part of the year （P〉 0.05）. Conversely, removal rates of the three pollutants were found to be significantly higher using model A than those observed using model B during the lower temperature part of the year （P 〈 0.01）. Furthermore, the morphologies and internal structures of plant roots further demonstrate that numerous white roots, whose distribution in soil was generally shallow, extend further under model A. The roots of these aquatic plants have an aerenchyma structure composed of parenchyma cells, therefore, roots of the cold-seasonal plants with major growth advantages used in A were capable of creating a more favorable vertical-flow constructed wetlands media- microenvironment. In conclusion, the plant-intercropping model （A） is more suitable for use in the cold environment experienced by constructed wetland during winter.     

Seasonal variations in the densities of fecal pellets produced by Oikopleura vanhoeffeni (C. Larvacea) and Calanus finmarchicus (C. Copepoda)

Two abundant macrozooplankters, Oikopleura vanhoeffeni (Lohmann) and Calanus finmarchicus (Gunnerus) were collected from the coastal waters off Newfoundland in different seasons during 1990–1991 and incubated in natural seawater to collect freshly egested, field produced, fecal pellets. The densities of fecal pellets from O. vanhoeffeni and C. finmarchicus were measured in an isosmotic density gradient. These are the first reported seasonal measurements of fecal pellet densities from two different types of macrozooplankters, O. vanhoeffeni, a larvacean, filter feeder and C. finmarchicus, a crustacean, suspension feeder. Pellet density ranges and medians were significantly different among seasons for both species, depending primarily on the type of phytoplankton ingested and its ability to be compacted. Winter O. vanhoeffeni and fall C. finmarchicus feces filled with nanoplankters and soft bodied organisms had less open space [packing index (% open area) = 3.5 and 4% for O. vanhoeffeni and C. finmarchicus, respectively] and were more dense (1.23 and 1.19 g cm^-3) than spring feces filled with diatoms (packing index = 15 and 23%, density = 1.13 and 1.11 gcm^-3). For copepods, these results contrast with previously published density values and with the predicted copepod fecal pellet density calculated, in the present study, using the conventional mass/volume relationship. Copepod spring and summer diatom-filled feces had a calculated density of 1.12 and 1.24 gcm^-3 vs a measured median density of 1.11 gcm^-3 for both spring and summer feces; the fall feces containing nanoplankters had a calculated density of 1.08 gcm^-3 vs a measured median density of 1.19 gcm^-3. Knowledge of the seasonal variations in fecal pellet densities is important for the development of flux models.