Selection and viability after ingestion of vegetative cells, resting spores and resting cells of the marine diatom, Chaetoceros pseudocurvisetus, by two copepods

Feeding response of two copepods Neocalanus flemingeri and Calanus sinicus on cultures of three life-forms; vegetative cells, resting spores and resting cells, of Chaetoceros pseudocurvisetus was investigated. N. flemingeri fed heavily on the vegetative cells but scarcely responded to feed on the resting spores. C. sinicus showed significantly higher filtering rate on the vegetative cells and resting cells than on the resting spores. Survival of the three life-forms of C. pseudocurvisetus after gut passage of the copepods was also studied. The resting spores could germinate from fecal pellets of both N. flemingeri and C. sinicus; however, both the vegetative cells and the resting cells could not survive ingestion by the copepods. These results suggest that resting spore forming diatoms, such as C. pseudocurvisetus form spores which have a low nutritional value and during gut passage are largely indigestible due to the heavily silicified frustules and thus minimize the effects of grazing by copepods.     

Comparing two methods for quantifying soil-borne Entomophaga maimaiga resting spores

To improve usability of methods for quantifying environmentally persistent entomophthoralean resting spores in soil, we modified and tested two methods using resting spores (azygospores) of the gypsy moth pathogen Entomophaga maimaiga. Both methods were effective for recovering resting spores at concentrations >100 resting spores/g dry soil. While a modification of a method originally described by Weseloh and Andreadis (2002) recovered more resting spores than a modified method based on Percoll density gradients, the ability to estimate true densities from counts was similar for both methods. Regression equations are provided for predicting true resting spore densities from counts, with R² values for both methods ?0.90.     

Towards an optimal sampling strategy for Alexandrium catenella (Dinophyceae) benthic resting cysts

The study proposes methodological developments to optimize sampling strategy of resting cysts of Alexandrium catenella to estimate their abundance with a predefined error. This work also aims to provide information on spatial distribution of resting cysts in sediments. The distribution mode of A. catenella resting cysts related to the abundance variability was studied through sediment cores sampling on four different spatial scales and using Ludox CLX gradient density method. The quantification method underestimates by a factor of 2 the resting cysts abundance in one gram of sediment. Application of Taylor's power law allowed us to define a compromise between sampling effort and abundance estimation error. In the case of A. catenella resting cysts from Thau lagoon, the optimal sampling strategy consists of sampling 10 stations on a surface of 2 km² for a given coefficient of variability (C) of 15%, sampling 3 sediment cores at each station (C = 30%) and counting only one replicate by core (C = 18%). Results related to the application of Taylor's power law are closely dependent on resting cyst density and aggregation in a given sediment. In our area, A. catenella resting cysts are mainly observed in the upper 3 cm of sediment. Horizontally, their heterogeneity is lower on 10 cm² surface and tends to stabilize itself beyond a surface of 10 m². Each author has to carry out this pre-sampling effort for his own resting cysts-forming species, in his own area, in order to increase accuracy of resting cyst mapping.     

Egg Placement by Anopheles gambiae (Diptera:Culicidae) as Influenced by Resting Surface Slope and Enclosure

In these experiments, oviposition by laboratory-reared Anopheles gambiae s.s. was as likely to occur from a vertical perch, as from a horizontal sitting position on a substrate of moist mud or open water. Tall cylinders with moist, dark walls provided an enclosed vertical resting surface from which An. gambiae deposited eggs. Similar numbers of eggs were deposited in these cylinders as on dark and moist horizontally-positioned ovipositional substrates. Likewise, An. gambiae oviposited equally from a vertical perch among emergent surrogate reeds vs. sitting horizontally on mud. Open ovipositional resources with exposed resting surfaces presenting 45°, 90°, and 135° angles relative to the cage floor received fewer eggs than a horizontally positioned, moist and dark ovipositional dish, even though more An. gambiae females settled on these angled resting surfaces post-oviposition. We conclude that vertical resting sites are adequate perches from which oviposition can occur if they provide high humidity and the paramount dark and wet ovipositional cues for An. gambiae oviposition.     

DNA extraction and amplification methods for ephippial cases of Daphnia resting eggs in lake sediments: a novel approach for reconstructing zooplankton population structure from the past

This study describes a method of DNA extraction and amplification for ephippial cases of Daphnia resting eggs from lake sediment. Recent studies have reconstructed succession records of Daphnia species by genetically analyzing Daphnia resting eggs stored in lake sediments and revealed changes in dominant Daphnia species that correspond well with environmental changes. However, this approach is not applicable to lakes where most of the resting eggs in the sediment have already hatched out. We modified conventional methods for DNA extraction and amplification to enable genetic analyses of the ephippial case that envelops and protects the resting eggs, and we compared the performance of the modified method to the conventional one. We confirmed that we could efficiently analyze the sequences of the ephippial cases collected in a sediment core using our modified method. It enables us to reconstruct changes in genetic structure of Daphnia populations regardless of hatching rates of the resting eggs.     

Breathing with your belly: Abdominal exhalation,loco-ventilatory integration and size constraints on locomotion in small mammals

In mammals, diaphragmatic contractions control inhalation while contraction of some thoracic hypaxial muscles and the transversus abdominis muscle contribute to exhalation. Additional thoracic hypaxial muscles are recruited as accessory ventilatory muscles to improve inhalation and exhalation during locomotion. However, the contribution of abdominal hypaxial muscles to resting and locomotor ventilation is little understood in mammals and loco-ventilatory integration has not been studied in small basal mammals. We show for the first time that all of the abdominal hypaxial muscles actively contribute to both resting and locomotory ventilation in mammals but in a size-dependent manner. In large opossums (Didelphis), hypaxial muscles exhibit uniform mild tonus during resting ventilation (pressurizing the gut to aid in exhalation) and shift to phasic bursts of activity during each exhalation during locomotion. Smaller opossums (Monodelphis) actively exhale by firing the abdominal hypaxial muscles at ～10 Hz at both rest and at preferred locomotor speeds. Furthermore, the large opossums entrained ventilation to limb cycling as speed increased while the small opossums entrained limb cycling to the resting ventilation rate during locomotion. Differences in these species are related to size effects on the natural frequency of the ventilatory system and increasing resting ventilation rates at small size. Large mammals, with lower resting ventilation rates, can increase ventilatory rates during locomotion, while the high resting ventilation rates of small mammals limits their ability to increase ventilation rates during locomotion. We propose that increase in mammalian body size during the Cenozoic may have been an adaptation or exaptation to overcome size effects on ventilation frequency.     

Alpha blocking and 1/fβ spectral scaling in resting EEG can be accounted for by a sum of damped alpha band oscillatory processes

The dynamical and physiological basis of alpha band activity and 1/f^β noise in the EEG are the subject of continued speculation. Here we conjecture, on the basis of empirical data analysis, that both of these features may be economically accounted for through a single process if the resting EEG is conceived of being the sum of multiple stochastically perturbed alpha band damped linear oscillators with a distribution of dampings (relaxation rates). The modulation of alpha-band and 1/f^β noise activity by changes in damping is explored in eyes closed (EC) and eyes open (EO) resting state EEG. We aim to estimate the distribution of dampings by solving an inverse problem applied to EEG power spectra. The characteristics of the damping distribution are examined across subjects, sensors and recording condition (EC/EO). We find that there are robust changes in the damping distribution between EC and EO recording conditions across participants. The estimated damping distributions are found to be predominantly bimodal, with the number and position of the modes related to the sharpness of the alpha resonance and the scaling (β) of the power spectrum (1/f^β). The results suggest that there exists an intimate relationship between resting state alpha activity and 1/f^β noise with changes in both governed by changes to the damping of the underlying alpha oscillatory processes. In particular, alpha-blocking is observed to be the result of the most weakly damped distribution mode becoming more heavily damped. The results suggest a novel way of characterizing resting EEG power spectra and provides new insight into the central role that damped alpha-band activity may play in characterising the spatio-temporal features of resting state EEG.     

Are they still viable? Physical conditions and abundance of <Emphasis Type="Italic">Daphnia pulicaria</Emphasis> resting eggs in sediment cores from lakes in the Tatra Mountains

All species of Daphnia (Cladocera) produce, at some stage in their life cycle, diapausing eggs, which can remain viable for decades or centuries forming a “seed bank” in lake sediments. Because of their often good preservation in lake sediment, they are useful in paleolimnology and microevolutionary studies. The focus of this study was the analysis of cladoceran resting eggs stored in the sediment in order to examine the ephippial eggs bank of Daphnia pulicaria Forbes in six mountain lakes in the High Tatra Mountains, the Western Carpathians (northern Slovakia and southern Poland). Firstly, we analyzed distribution, abundance and physical condition of resting eggs in the sediment for their later used in historical reconstruction of Daphnia populations by genetic methods. To assess changes in the genetic composition of the population through time, we used two microsatellite markers. Although DNA from resting eggs preserved in the High Tatra Mountain lake sediments was extracted by various protocols modified for small amounts of ancient DNA, DNA from eggs was not of sufficient quality for microsatellite analyses. Distribution curves of resting eggs from sediment cores correspond to the environmental changes that have occurred in the High Tatra Mountains area during last two centuries (atmospheric acid deposition, fish introduction) and demonstrate their influence on natural populations. Evaluation of ephippia physical condition (the most common category was empty ephippial covers) suggests that the majority of resting eggs hatched to produce a new generation of Daphnia or may be due to failed deposition of resting eggs by Daphnia to the chitinous case. In conclusion, age, low quantity and poor physical condition of resting eggs from these Tatra lake sediments proved to be unsuitable not just for use in genetic analyses, but also the possibilities of autogenous restoration of Daphnia populations from the resting egg banks in the Tatra sediments are negligible.     

Chytrid mycoparasitism of entomophthoralean azygospores

Mycoparasitism – when one fungus parasitizes another – has been reported to affect Beauveria bassiana and mycorrhizal fungi in the field. However, mycoparasitism of any fungi in the Order Entomophthorales has never been reported before now. The majority of entomophthoralean species persist as resting spores (either zygospores or azygospores) in the environment and dormant entomophthoralean resting spores (whether formed as zygospores or azygospores) are thought to be especially well adapted for survival over long periods due to their thick double walls. Entomophthoralean resting spores can accumulate in the soil as large reservoirs of inoculum which can facilitate the onset and development of epizootics. We report parasitism of azygospores of the gypsy moth pathogen Entomophaga maimaiga caged in soil from southern Ohio by the chytrid fungus Gaertneriomyces semiglobifer. G. semiglobifer had previously been isolated from soil samples from North America, Europe and Australia or horse manure from Virginia. After isolation and identification of G. semiglobifer, azygospores of E. maimaiga exposed to zoospores of G. semiglobifer exhibited high levels of mycoparasitism and G. semiglobifer was subsequently reisolated from mycoparasitized resting spores. We discuss the importance of this finding to the epizootiology of insect diseases caused by entomophthoralean fungi.     

Kinetics of Accumulation of Ribulose-1,5-bisphosphate Carboxylase during Greening in Euglena gracilis: Nutritional Regulation

The accumulation of ribulose-1,5-bisphosphate carboxylase (RuBPCase) in resting Euglena gracilis strain Z during greening is photo-regulated (Freyssinet, Eichholz, Buetow 1984 Plant Physiol 75: 850-857. Greening resting cells are not photosynthetically competent for about the first 24 hours in the light. Therefore, substrates for a net synthesis of the enzyme must come from endogenous constituents. During this time, degradation of endogenous paramylum (carbohydrate) reserves provides the main source of substrates. By about 24 hours of greening, resting cells are photosynthetically competent and RuBPCase accumulation becomes highly sensitive to 3-(3,4 dichlorophenyl)-1,1-dimethylurea. Therefore, from about 24 hours of greening onward, substrates (and/or energy) for RuBPCase synthesis are provided by photosynthesis. Ethanol, a nutritional substrate ordinarily used constitutively by Euglena for growth, inhibits RuBPCase accumulation when added to the resting medium in the light. The alcohol exerts this negative regulatory effect by limiting the availability of substrates needed for a net synthesis of the enzyme.     

The Pool of ADP and ATP Regulates Anaerobic Product Formation in Resting Cells of Lactococcus lactis

Lactococcus lactis grows homofermentatively on glucose, while its growth on maltose under anaerobic conditions results in mixed acid product formation in which formate, acetate, and ethanol are formed in addition to lactate. Maltose was used as a carbon source to study mixed acid product formation as a function of the growth rate. In batch and nitrogen-limited chemostat cultures mixed acid product formation was shown to be linked to the growth rate, and homolactic fermentation occurred only in resting cells. Two of the four lactococcal strains investigated with maltose, L. lactis 65.1 and MG1363, showed more pronounced mixed acid product formation during growth than L. lactis ATCC 19435 or IL-1403. In resting cell experiments all four strains exhibited homolactic fermentation. In resting cells the intracellular concentrations of ADP, ATP, and fructose 1,6-bisphosphate were increased and the concentration of P_i was decreased compared with the concentrations in growing cells. Addition of an ionophore (monensin or valinomycin) to resting cultures of L. lactis 65.1 induced mixed acid product formation concomitant with decreases in the ADP, ATP, and fructose 1,6-bisphosphate concentrations. ADP and ATP were shown to inhibit glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, and alcohol dehydrogenase in vitro. Alcohol dehydrogenase was the most sensitive enzyme and was totally inhibited at an adenine nucleotide concentration of 16 mM, which is close to the sum of the intracellular concentrations of ADP and ATP of resting cells. This inhibition of alcohol dehydrogenase might be partially responsible for the homolactic behavior of resting cells. A hypothesis regarding the level of the ATP-ADP pool as a regulating mechanism for the glycolytic flux and product formation in L. lactis is discussed.     

Sampling Design Influences the Observed Dominance of Culex tritaeniorhynchus: Considerations for Future Studies of Japanese Encephalitis Virus Transmission

Mosquito sampling during Japanese encephalitis virus (JEV)-associated studies, particularly in India, has usually been conducted via aspirators or light traps to catch mosquitoes around cattle, which are dead-end hosts for JEV. High numbers of Culex tritaeniorhynchus, relative to other species, have often been caught during these studies. Less frequently, studies have involved sampling outdoor resting mosquitoes. We aimed to compare the relative abundance of mosquito species between these two previously used mosquito sampling methods. From September to December 2013 entomological surveys were undertaken in eight villages in a Japanese encephalitis (JE) endemic area of Bangladesh. Light traps were used to collect active mosquitoes in households, and resting boxes and a Bina Pani Das hop cage were used near oviposition sites to collect resting mosquitoes. Numbers of humans and domestic animals present in households where light traps were set were recorded. In five villages Cx. tritaeniorhynchus was more likely to be selected from light trap samples near hosts than resting collection samples near oviposition sites, according to log odds ratio tests. The opposite was true for Cx. pseudovishnui and Armigeres subalbatus, which can also transmit JEV. Culex tritaeniorhynchus constituted 59% of the mosquitoes sampled from households with cattle, 28% from households without cattle and 17% in resting collections. In contrast Cx. pseudovishnui constituted 5.4% of the sample from households with cattle, 16% from households with no cattle and 27% from resting collections, while Ar. subalbatus constituted 0.15%, 0.38%, and 8.4% of these samples respectively. These observations may be due to differences in timing of biting activity, host preference and host-seeking strategy rather than differences in population density. We suggest that future studies aiming to implicate vector species in transmission of JEV should consider focusing catches around hosts able to transmit JEV.     

Leak Current Rectification in Myxicola Giant Axons : Constant field and constant conductance components

Early leak current, i.e. for times similar to the time to peak of the transient current was measured in Myxicola giant axons in the presence of tetrodotoxin. The leak current-voltage relation rectifies, showing more current for strong depolarizing pulses than expected from symmetry around the holding potential. A satisfactory practical approximation for most leak corrections is constant resting conductance. The leak current-voltage curve rectifies less than expected from the constant field equation. These curves cannot be reconstructed by summing the constant field currents for sodium and potassium using a P_Na/P_K ratio obtained in the usual way, from zero current constant field fits to resting membrane potential data. Nor can they be reconstructed by summing the constant field current for potassium with that for any other single ion. They can be reconstructed, however, by summing the constant field current for potassium with a constant conductance component. It is concluded that the leak current and the resting membrane potential, therefore, are determined by multiple ionic components, at least three and possibly many. Arguments are presented suggesting that ion permeability ratios obtained in the usual way, by fitting the constant field equation to resting membrane potential data should be viewed with skepticism.     

Resting metabolic rates of two orbweb spiders: a first approach to evolutionary success of ecribellate spiders

Spiders are considered conservative with regard to their resting metabolic rate, presenting the same allometric relation with body mass as the majority of land-arthropods. Nevertheless, web-building is thought to have a great impact on the energetic metabolism, and any modification that affects this complex behavior is expected to have an impact over the daily energetic budget. We analyzed the possibility of the presence of the cribellum having an effect on the allometric relation between resting metabolic rate and body mass for an ecribellate species (Zosis geniculata) and a cribellate one (Metazygia rogenhoferi), and employed a model selection approach to test if these species had the same allometric relationship as other land-arthropods. Our results show that M. rogenhoferi has a higher resting metabolic rate, while Z. geniculata fitted the allometric prediction for land arthropods. This indicates that the absence of the cribellum is associated with a higher resting metabolic rate, thus explaining the higher promptness to activity found for the ecribellate species. If our result proves to be a general rule among spiders, the radiation of Araneoidea could be connected to a more energy-consuming life style. Thus, we briefly outline an alternative model of diversification of Araneoidea that accounts for this possibility.     

Zur fortpflanzungsbiologie von mesostoma ehrenbergii (Focke, 1836) (Turbellaria)

1. At temperature levels from 10 to 25°C animals from resting eggs produce subitaneous eggs independent on temperature. In contrast animals from subitaneous eggs produce subitaneous eggs dependent on temperature. At a high rate subitaneous eggs are only formed at temperature levels above 20°C.
2. Below 10°C no development occurs in the juveniles. At temperatures of 30/22°C (24.7°C) the first subitaneous eggs are formed after 6–9 days, at 14/9°C (10.7°C) they are formed after 34 days. At different temperature levels the developmental rate of the young is from 10.5 to 42 days. One generation extends over 16.5 (30/22°C) to 75 days (14/9°C). The average egg production is 10–20 subitaneous eggs or 30–60 resting eggs. The maximum egg production of one individual is 50 subitaneous eggs or 84 resting eggs. 50% of the animals have just formed resting eggs, before the juveniles are hatched. Resting eggs in the first egg-batch are formed 6–20 days later than subitaneous eggs. The duration of life is between 65 (30/22°C) and 140 days (19/13°C).
3. Young worms in resting eggs have a dormance period of at least 15–30 days.

At room temperatures (20°C) no juvenile in resting eggs hatches from water. By combining room and refrigerator (3.5°C) temperatures the hatching rate increases to a maximum of 85%. To reach a hatching rate of 50–65% the influence of low temperatures must be at least 30 days. At room temperatures 60% of the young in resting eggs hatch from mud covered with water. Combining high and low temperatures the hatching success is between 67 and 81%, where the highest percentage of the young may hatch at room temperature. Up to 90 days low temperatures cause a maximum hatching rate of 79%. It decreases to approximately 30% after 180 days. At high temperatures resting eggs preserved in 100% moist mud, survive for two months. By adding a period of low temperatures the hatching rate increases to a maximum of 52%. Low temperatures are survived for more than 6 months. Up to 30 days preservation at 3.5°C causes a maximum hatching rate of 61%, up to 12o days it decreases to 30%. At room temperature the young in resting eggs are not resistant against air-dried mud (30–40% rel. air moisture). Combining high and low temperatures air-dried mud is endured 1 month (hatching rate 5–14%). Preservation of 30–120 days at 3.5°C and 70% rel. air moisture result in a hatching rate of 43–61%. li]4. In the open air in Middle-Europe there occur 5–6 generations of M. ehrenbergii per life-cycle. The first generation hatches from resting eggs in May, where the production of subitaneous eggs is independent on temperature. All other generations up to October hatch from subitaneous eggs. The egg-production of those worms is dependent on environmental factors. In summer subitaneous egg production prevails, in autumn resting egg production. The abundance during the life-cycle is dependent on the number of animals which produce subitaneous eggs. Resting eggs are predestinated to endure periods of dryness and cold. The life-cycles of the species M. lingua and M. productum are different from those of M. ehrenbergii in length and in the number of generations. In both species 7 generations occur over 8 to 8.5 respectively 5.5 months. M. nigrirostrum only forms resting eggs. The life-cycle consists of one generation from February/March to May/June.     

Impulse-dependent extracellular resting dopamine concentration in rat striatum in vivo

The ambient resting dopamine (DA) concentration in brain regulates cognition and motivation. Despite its importance, resting DA level in vivo remains elusive. Here, by high-frequency stimulation of the medial forebrain bundle and immediately following the stimulus-induced DA overflow, we recorded a DA “undershoot” which is a temporal reduction of DA concentration to a level below the baseline. Based on the DA undershoot, we predicted a resting DA concentration of ∼73 nM in rat striatum in vivo. Simulation studies suggested that removing basal DA by DAT during the post-stimulation inhibition of tonic DA release caused the DA undershoot, and the resting concentration of DA modulated the kinetics of the evoked DA transient. The DA undershoot was eliminated by either blocking D2 receptors with haloperidol or blocking the DA transporter (DAT) with cocaine. Therefore, the impulse-dependent resting DA concentration is in the tens of nanomolar range and is modulated by the presynaptic D2 receptors and the DAT in vivo.     

The toxic dinoflagellate Cochlodinium polykrikoides (Dinophyceae) produces resting cysts

While harmful algal blooms (HABs) caused by the toxic dinoflagellate Cochlodinium polykrikoides have been known to science for more than a century, the past two decades have witnessed an extraordinary expansion of these events across Asia, North America, and even Europe. Although the production of resting cysts and subsequent transport via ships’ ballast water or/and the transfer of shellfish stocks could facilitate this expansion, confirmative evidence for cyst production by C. polykrikoides is not available. Here, we provide visual confirmation of the production of resting cysts by C. polykrikoides in laboratory cultures isolated from North America. Evidence includes sexually mating cell pairs, planozygotes with two longitudinal flagella, formation of both pellicular (temporary) cysts and resting cysts, and a time series of the cyst germination process. Resting cyst germination occurred up to 1 month after cyst formation and 2–40% of resting cysts were successfully germinated in cultures maintained at 18–21 °C. Pellicular cysts with hyaline membranes were generally larger than resting cysts, displayed discernable cingulum and/or sulcus, and reverted to vegetative cells within 24 h to ∼1 week of formation. A putative armored stage of C. polykrikoides was not observed during any life cycle stage in this study. This definitive evidence of resting cyst production by C. polykrikoides provides a mechanism to account for the recurrence of annual blooms in given locales as well as the global expansion of C. polykrikoides blooms during the past two decades.     

Long-term adaptation capacity of ponies: effect of season and feed restriction on blood and physiological parameters

Domesticated horses are increasingly kept under semi-natural housing conditions, whereas their adaptation capacity is not fully investigated. In all, 10 Shetland pony mares were held under semi-extensive conditions for 1 year. In winter animals were allocated into two feeding groups (60% and 100% of maintenance energy requirement, respectively). Triiodothyronine, thyroxine, non-esterified fatty acids (NEFA), total bilirubin, total protein, triglyceride, glucose, insulin and hair length were measured at monthly intervals, whereas BW, body condition score, cresty neck score and resting heart rate were recorded every 2 weeks. From summer to winter all Ponies showed a reduction in resting heart rate (P<0.001) and triiodothyronine (P<0.001) but an increase in NEFA (P<0.001), thyroxine (P<0.001) and triglyceride (P<0.001) concentrations. Feed restriction led to a reduced resting heart rate (P=0.009), increased NEFA (P<0.001) and total bilirubin (P=0.008) concentrations. Thyroid hormones did not differ between feeding groups (P>0.05). Refeeding of restrictively fed ponies resulted in a rapid increase in resting heart rate and BW and a return of blood parameters to reference values. Adequately supplied animals adapted without difficulty to varying environmental conditions, whereas feed restriction in ponies during winter resulted in reduced resting heart rates suggesting a reduced basal metabolic rate. The energy restriction was compensated by mobilizing body fat reserves which led to changes in blood parameters. Refeeding in feed restricted animals revealed a remarkably quick recovery of physiological and blood parameters to reference values. We therefore suggest that year round-outdoor housing can be a suitable housing system for robust horse breeds provided that an adequate food supply is available.     

Resting cysts,and effects of temperature and salinity on the growth of vegetative cells of the potentially harmful species Alexandrium insuetum Balech (Dinophyceae)

The potentially harmful species Alexandrium insuetum established by the incubation of resting cysts isolated from sediment trap samples collected at Jinhae-Masan Bay, Korea was characterized by morphological and phylogenetic analysis. The effects of temperature and salinity on the growth of A. insuetum were also investigated. The resting cysts are characterized by a spherical shape, a small size (20–25 μm) and the presence of either three or four red accumulation bodies. The similarity of morphological features of the resting cysts to those of other species of the minutum group (consisting of Alexandrium minutum and A. tamutum) indicates that the morphological features of resting cysts might improve the accuracy of the grouping of Alexandrium species. A. insuetum germinated from the resting cysts is morphologically consistent with vegetative cells reported from Korean and Japanese coastal areas, and has an partial large subunit (LSU) rDNA sequence identical to that from Japanese strains. The growth of A. insuetum was observed between salinity 20 and 35, with increasing temperature; however at 25 °C, A. insuetum could grow even at the salinity of 15. The highest growth rate (0.60 d⁻¹) was observed at 25 °C and the salinity of 25, which is higher than the previously reported growth rate of A. tamarense, which is responsible for outbreaks of paralytic shellfish poisoining and blooms in Jinhae-Masan Bay. These results suggest that the proliferation of A. insuetum in Jinhae-Masan Bay is likely to be highest during the summer.