The infection of Moina macrocopa by a colonial peritrich, Epistylis daphniae, and its effects on the host

• 1 The effects of infection by Epistylis daphniae on its host, Moina macrocopa, were studied in the laboratory at 28°C by comparing the growth, reproduction and survival between infected and uninfected hosts.
• 2 Infestation by epizoites had little or no effect on the survival of the dadoceran hosts when adequate food was present.
• 3 The infected cladocerans had lower growth rates as juveniles, lower net reproduction rates as adults, and smaller body size at death than uninfected hosts.
• 4 The index of infection at different stages in the life cycle was related to the durations of intermoult period. Ranked in order of both index of infection and intermoult duration, the development stages were: old adult > young adult > juvenile.

     

A review on the “in vitro” culture of freshwater mussels (Unionoida)

Many Unionoida are considered to be extinct, endangered, or of special concern. These bivalves have complex life cycle stages that limit successful culture. In nature, the larvae (glochidia) of these bivalves must successfully parasitize a host (mainly fish) in order to metamorphose into juveniles. The two artificial methods used to obtain juvenile freshwater mussels in laboratory are either by induced attachment to host fish or by in vitro culture of glochidia. This article is focused on the in vitro method that represents a novel and alternative process to fish infestation, offering the ability to obtain larger numbers of juveniles without the need for host fishes and reducing the overall costs of propagation. In vitro culture requires a medium which fulfills the nutritional needs of each glochidia species and avoids microbial contamination. Recently, this methodology has presented excellent results with survival and transformation rates up to 94% using host fish plasma. High efficiencies on growth, and survival rates (84%) of juvenile freshwater bivalve Hyriopsis myersiana (Lea, 1856) up to 120 days were obtained when reared in adequate recirculating aquacultural systems using a very specific diet. More research is still needed to demonstrate successful propagation, mainly concerning the media nutritional composition to increase glochidia transformation and juvenile quality.     

Cultivation of Sponge Larvae: Settlement,Survival, and Growth of Juveniles

The aim of this study was to culture sponge juveniles from larvae. Starting from larvae we expected to enhance the survival and growth, and to decrease the variation in these parameters during the sponge cultures. First, settlement success, morphological changes during metamorphosis, and survival of Dysidea avara, Ircinia oros, Hippospongia communis, under the same culture conditions, were compared. In a second step, we tested the effects of flow and food on survival and growth of juveniles from Dysidea avara and Crambe crambe. Finally, in a third experiment, we monitored survival and growth of juveniles of D. avara and C. crambe transplanted to the sea to compare laboratory and field results. The results altogether indicated that sponge culture from larvae is a promising method for sponge supply and that laboratory culture under controlled conditions is preferred over sea cultures in order to prevent biomass losses during these early life stages.     

The effects of infection by Tetracapsuloides bryosalmonae (Myxozoa) and temperature on Fredericella sultana (Bryozoa)

The myxozoan, Tetracapsuloides bryosalmonae, exploits freshwater bryozoans as definitive hosts, occurring as cryptic stages in bryozoan colonies during covert infections and as spore-forming sacs during overt infections. Spores released from sacs are infective to salmonid fish, causing the devastating Proliferative Kidney Disease (PKD). We undertook laboratory studies using mesocosm systems running at 10, 14 and 20 °C to determine how infection by T. bryosalmonae and water temperature influence fitness of one of its most important bryozoan hosts, Fredericella sultana, over a period of 4 weeks. The effects of infection were context-dependent and often undetectable. Covert infections appear to pose very low energetic costs. Thus, we found that growth of covertly infected F. sultana colonies was similar to that of uninfected colonies regardless of temperature, as was the propensity to produce dormant resting stages (statoblasts). Production of statoblasts, however, was associated with decreased growth. Overt infections imposed greater effects on correlates of host fitness by: (i) reducing growth rates at the two higher temperatures; (ii) increasing mortality rates at the highest temperature; (iii) inhibiting statoblast production. Our results indicate that parasitism should have a relatively small effect on host fitness in the field as the negative effects of infection were mainly expressed in environmentally extreme conditions (20 °C for 4 weeks). The generally low virulence of T. bryosalmonae is similar to that recently demonstrated for another myxozoan endoparasite of freshwater bryozoans. The unique opportunity for extensive vertical transmission in these colonial invertebrate hosts couples the reproductive interests of host and parasite and may well give rise to the low virulence that characterises these systems. Our study implies that climate change can be expected to exacerbate PKD outbreaks and increase the geographic range of PKD as a result of the combined responses of T. bryosalmonae and its bryozoan hosts to higher temperatures.     

Postmetamorphic growth,survival, and age at first reproduction of the salamander,hynobius nebulosus tokyoensis Tago in relation to a consideration on the optimal timing of first reproduction

The postmetamorphic growth and survival of the salamander Hynobius nebulosus tokyoentisTago were surveyed in the study site located in Habu village of Hinodemachi, a suburb of Tokyo City, during 1975–1981. A laboratory experiment on the growth rate of juveniles was conducted in parallel with the field survey. The result indicated that this salamander grew at the rate of 8,mm in s.v.l. per year during the juvenile stage, but its growth rate decreased markedly as low as 1.8 mm for males and 1.1 mm for females, once it had attained sexual maturity. According to the “capture-recapture” procedure the annual survival rate after metamorphosis was found to be quite high; that is, approximately 0.7. By using the growth rate of juveniles and the difference between the sizes at metamorphosis and sexual maturity, the age at first reproduction was estimated to be 4 year for males and 5 year for females. From the data obtained in this study, the intrinsic rates of increase (r) were calculated for various values of age at first reproduction under different survival schedules, and the relationship between the age at first reproduction and fitness as measured by r was examined. The result indicated that an optimal age maximizing fitness always existed under respective survival schedules, and the observed age at first reproduction of this salamandei was found to coincide well with the predicted optimal age.     

Host choice and fitness of anemonefish Amphiprion ocellaris (Perciformes: Pomacentridae) living with host anemones (Anthozoa: Actiniaria) in captive conditions

In this study, we investigated the host choice of naïve Amphiprion ocellaris, a specialist, at two different stages of development (newly settling juveniles and post-settlement juveniles). The fish were exposed to their natural and unnatural host species in the laboratory and their fitness was assessed in terms of activity and growth rate. Newly settling juveniles exhibited little host preference, while post-settlement juveniles immediately associated with their most common host in the wild. The analysis of fish activity confirmed that A. ocellaris is diurnal; they are most active in the morning, less at midday and barely move at night. The average travelling distance of juveniles was shorter in the groups living with their natural host, increasing in the groups living with an unnatural host and was highest in groups that did not become associated with any other unnatural host species. Post-settlement juveniles living with the natural host species grew better than those living with unnatural hosts or without anemone contact. These results suggest that the welfare of A. ocellaris in captivity will be optimized by keeping them with their natural anemone host species, although more generalist Amphiprion species may survive in association with other hosts.     

Blood feeding in juvenile Paragnathia formica (Isopoda: Gnathiidae): biochemical characterization of trypsin inhibitors, detection of anticoagulants, and molecular identification of fish hosts

The 3 post-marsupial juvenile stages of the gnathiid isopod, Paragnathia formica, are haematophagous ectoparasites of fishes that may, in heavy infestations, cause host mortality. Protein digestion in fed stage 3 juveniles is accomplished by cysteine proteinases, but what bioactive compounds attenuate host haemostatic, inflammatory and immunological responses during feeding is unknown. Trypsin inhibitory activity and anticoagulant activity were detected in crude extracts of unfed P. formica stage 1 juveniles; fractionation of stage 1 crude extracts by ion exchange chromatography resulted in 3 preparations each displaying these bioactivities. Further characterization revealed anti-thrombin activity in 2 of these preparations, whilst the third displayed the strongest anticoagulant activity that targeted a factor of the intrinsic coagulation pathway. Three trypsin inhibitors (18 kDa, 21 kDa, and 22 kDa) were also detected using reverse zymography. In parallel, homogenates of fed stage 2 and 3 juveniles were used to identify their fish hosts by amplifying the 16S mitochondrial rDNA and 18S genomic rDNA vertebrate gene regions. Blood from at least 4 fish families had been ingested by separate individuals during feeding. This study demonstrates that trypsin inhibitors and anticoagulants are present in P. formica juveniles which could suppress host haemostatic, inflammatory and immunological responses during feeding, and that juveniles are not host specific.     

The combined effects of temperature and salinity on hatching success and the survival,growth, and development of the larval stages of Metapenaeus bennettae (Racek & Dall)

During the spawning season of the estuarine prawn Metapenaeus bennettae (Racek & Dall), laboratory and field experiments were conducted to examine the combined effects of temperature and salinity on hatching success of eggs and the survival, growth and development of larvae. Response surface analysis showed that optimal levels of temperature and salinity for maximum hatching success varied depending on conditions during spawning. Similarly, temperature and salinity conditions that produced maximum survival and growth of larvae depended on conditions during rearing prior to experimental temperature/salinity treatments. At the onset of feeding, larvae showed the lowest tolerance to changes in temperature and salinity. Supplementary feeding experiments in the laboratory, and survival rates in field experiments indicated that starvation was a more potent factor than the effects of temperature and salinity in determining survival through the protozoeal larval stages. Late larval stages were relatively indifferent to the effects of temperature and salinity. It is suggested that, during early development, adaptive response to the prevailing physical conditions enhances survival in an estuarine environment.     

Rank-dependent compromises between growth and predator protection in lizard dominance hierarchies

Juvenile Anolis aeneus lizards often live in dominance hierarchies, and in both the laboratory and field, rank was primarily determined by a juvenile's size relative to the others when it entered a hierarchy. Because juveniles entered hierarchies soon after hatching and left when they reached subadult sizes, most juveniles slowly rose in status during their sojourn in dominance hierarchies. In laboratory experiments, rank and growth rate were positively related when both food and perches were uniformly distributed. However, when perches were non-uniformly distributed, juveniles competed to live on those perch configurations which offered protection from predators. Under these conditions, growth was more weakly related to rank than in the uniform-habitat trials, and high-ranking juveniles living on the preferred (safe) perches had significantly lower growth rates than those living elsewhere. In contrast, low-ranking juveniles in non-uniform habitats experienced no such compromise between growth and safety, and those on the preferred perches tended to grow faster than those living elsewhere. Since most juveniles in the field seem to gradually rise from low to high rank, the behavioural strategies for optimizing growth and survival may change ontogenetically in this species.     

A delayed effect of the aquatic parasite <Emphasis Type="Italic">Margaritifera laevis</Emphasis> on the growth of the salmonid host fish <Emphasis Type="Italic">Oncorhynchus masou masou</Emphasis>

Parasitic species often have detrimental effects on host growth and survival. The larvae of the genus Margaritifera (Bivalvia), called glochidia, are specialist parasites of salmonid fishes. Previous studies have reported negligible influences of the parasite on their salmonid hosts at natural infection levels. However, those studies focused mainly on their instantaneous effects (i.e., during the parasitic period). Given the time lag between physiological and somatic responses to pathogen infections, the effect of glochidial infection may become clearer during the post-parasitic period. Here, we examined whether the effect of glochidial infections of Margaritifera laevis on its salmonid host Oncorhynchus masou masou would emerge during the post-parasitic period. We performed a controlled aquarium experiment and monitored fish growth at two time intervals (i.e., parasitic and post-parasitic periods) to test this hypothesis. Consistent with previous observations, the effects of glochidial infection were unclear in the middle of the experiment (day 50; parasitic period). However, even with a natural glochidial load (48 glochidia per fish), we found a significant reduction in growth rates of infected fish in the extended period of the experiment (day 70; post-parasitic period). Our results suggest that examining only instantaneous effects may provide misleading conclusions about mussel–host relationships.     

Life history cost of trematode infection in Helisoma anceps using mark-recapture in Charlie's Pond

Parasitism has the potential to affect key life history traits of an infected host. Perhaps the most studied interactions are in snail-trematode systems, where infection can result in altered growth rates, survival, and/or fecundity of the individual. Positive correlations between host size and parasite prevalence are often attributed to changes in growth rates or mortality, which have been observed in the laboratory. Extending lab-based conclusions to the natural setting is problematic, especially when environmental conditions differ between the laboratory and the field. The present study uses reproduction experiments and mark-recapture methods to directly measure key life history traits of the pulmonate snail Helisoma anceps in Charlie's Pond. Based on previous laboratory and field experiments on H. anceps, we predict a significant reduction in fecundity, but not growth rate or survival, of infected snails. Individual capture histories were analyzed with multistate models to obtain estimates of survival and infection probabilities throughout the year. Recaptured individuals were used to calculate specific growth rates. Trematode infection resulted in complete castration of the host. However, neither survival nor growth rates were found to differ between infected and uninfected individuals. The probability of infection exhibited seasonal variation, but it did not vary with size of the snail. These results suggest that the correlation between host size and trematode prevalence is not due to differential mortality or changes in growth rates. Instead, the infection accumulates in large snails via the growth of smaller, infected individuals.     

Effects of the eyefluke, Diplostomum spathaceum, on the behaviour of dace (Leuciscus leuciscus)

The behaviour of dace infected with Diplostomum spathaceum was investigated in the laboratory. As the number of parasites present in the eye increased, the efficiency with which the fish fed on Gammarus pulex declined. The loss of efficiency was compensated for by an increase in the time devoted to feeding. Heavily infected fish spent more time in the surface layers of the water. This may increase the likelihood that a gull might eat the fish and thereby continue the life-cycle of the parasite. The parasite modifies the behaviour of its host in a way that increases the parasite's chances of survival at the expense of the host.     

Hibernation in the mountain pygmy possum Burramys parvus (Marsupialia)

Mountain pygmy possums Burramys parvus (40 g) disappear from their Mt. Kosciusko boulder fields from May to October/November and it is assumed that they hibernate during this time. However, laboratory studies did not observe the characteristic hibernation pattern of placentals, which, throughout the hibernation season, show long bouts of torpor (several days to weeks) that are interrupted by short (< 1 day) normothermic periods. We investigated the pattern of hibernation in juvenile (N = 8) and adult (N = 8) male and female B. parvus in the laboratory at an air temperature that was similar to that in the field during winter. Adults commenced hibernation earlier and hibernated longer (about seven months) than juveniles (about five months). All adult individuals hibernated whereas only six of the eight juveniles did so. Hibernating animals showed distinct seasonal changes in the duration of torpor bouts. Torpor bouts were short (about five days) at the beginning, long (12–20 days) during the middle, and short again at the end of the hibernation season. Normothermic periods were usually shorter than one day. The pattern of the seasonal change of torpor bout duration differed between juveniles and adults and between sexes. Body temperature during mid-hibernation was regulated at about 2 ° c in females and 3 ° C in males and the metabolic rate was similar to that of hibernating placentals.     

Starving early juvenile sprat Sprattus sprattus (L.) in western Baltic coastal waters: evidence from combined field and laboratory observations in August and September 2003

Growth patterns inferred from otolith microstructure analysis were compared between sprat Sprattus sprattus early juveniles (26–42 mm total length, L _T) collected in August 2003 in shallow coastal waters of the Kiel Fjord, and sprat recruits (60–95 mm L _T) sampled in October during a pelagic trawl survey of the western Baltic Sea. At the end of August, a sudden and very rapid decline in otolith growth was observed in early juveniles but not in sprat recruits. Laboratory results indicated that the early juvenile fish were starving prior to capture. Specifically, when transferred to the laboratory, otolith growth rates immediately increased in fish provided ad libitum food rations, while otolith growth of starved fish continued to decline in the same manner observed prior to field collection. In addition, the vast majority of juvenile sprat had empty stomachs on the sampling day. Given that juveniles and recruits probably experienced similar temperature conditions, the rapid decline in juvenile growth rates presumably resulted from very poor feeding conditions in nearshore waters. Starvation during the early juvenile period has not been documented before, but may, at least in the case of Baltic sprat, comprise a density-dependent mechanism operating in coastal nursery areas in some years.     

Host,Pathogen, and Environmental Characteristics Predict White-Nose Syndrome Mortality in Captive Little Brown Myotis (Myotis lucifugus)

An estimated 5.7 million or more bats died in North America between 2006 and 2012 due to infection with the fungus Pseudogymnoascus destructans (Pd) that causes white-nose syndrome (WNS) during hibernation. The behavioral and physiological changes associated with hibernation leave bats vulnerable to WNS, but the persistence of bats within the contaminated regions of North America suggests that survival might vary predictably among individuals or in relation to environmental conditions. To investigate variables influencing WNS mortality, we conducted a captive study of 147 little brown myotis (Myotis lucifugus) inoculated with 0, 500, 5 000, 50 000, or 500 000 Pd conidia and hibernated for five months at either 4 or 10°C. We found that female bats were significantly more likely to survive hibernation, as were bats hibernated at 4°C, and bats with greater body condition at the start of hibernation. Although all bats inoculated with Pd exhibited shorter torpor bouts compared to controls, a characteristic of WNS, only bats inoculated with 500 conidia had significantly lower survival odds compared to controls. These data show that host and environmental characteristics are significant predictors of WNS mortality, and that exposure to up to 500 conidia is sufficient to cause a fatal infection. These results also illustrate a need to quantify dynamics of Pd exposure in free-ranging bats, as dynamics of WNS produced in captive studies inoculating bats with several hundred thousand conidia may differ from those in the wild.     

Factors that affect juvenile emergence in Gammarus palustris (Bousfield, 1969)

In the laboratory, hatched juveniles of the amphipod Gammarus palustris (Bousfield, 1969) emerged from the female's brood pouch at increased rates when the mother was pipetted, fed on mussel meat, or was immersed after a period of exposure to the air. Because juveniles emerged unaided from females feeding on mussel meat, its presence appeared to stimulate the juveniles to emerge.G. palustris is typically found at the high tide mark in the intertidal zone during the reproductive season. Females experience factors similar to those tested in the laboratory only when covered by water; when the tide is out they lie quiescent under rocks and debris. It is hypothesized that in the field juveniles emerge at the greatest rate at the beginning of an incoming tide.     

Yellow-bellied marmots do not compensate for a late start: the role of maternal allocation in shaping life-history trajectories

Yellow-bellied marmots, Marmota flaviventris, are obligate hibernators with a relatively short active season. Animals born earlier in the season have higher chances of fulfilling the energetic requirements to survive the long winter. Therefore, the onset of breeding should have a profound impact on juvenile survival. However, there are different ways to compensate for a late start. Late breeders might allocate more resources to late born offspring, making up for the bad start, or juveniles might show compensatory growth. They are not exclusive hypotheses and both can lead to juveniles entering hibernation with a similar body condition. We used data from a long term study in and around the Rocky Mountain Biological Laboratory in Colorado to test these two hypotheses. Animals are individually marked and trapped regularly. We compared mass at weaning, mass at the end of the season, growth rates and survival between animals born earlier and later in the season. We found no evidence of increased maternal input: late breeders had lighter offspring at weaning than early breeders, and late born juveniles did not increase their growth rates. Therefore, late born individuals ended the season with lower body mass, and were thus, less likely to survive the winter. In conclusion, life-history trajectories of juvenile yellow-bellied marmots were determined by maternal allocation, whereas post-weaning decisions did not modify their fate.     

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.     

长江口水域夏季鱼卵和仔稚鱼年间变化

基于2005年、2008年、2009年和2011年8月(夏季)在长江口水域(30°30'—31°45'N,121°15'—123°10'E)4个航次的浮游生物拖网资料,分析了长江口水域鱼卵和仔稚鱼的种类组成、数量分布特征及其年间变化。结果表明:4个航次采集的鱼卵和仔稚鱼鉴定到种的种类有17种,隶属于8目13科,以鲈形目种类最多,11种,其次是鲱形目,5种,其他各目种类均小于5种;种类数存在明显年间差异,2005年种类数最多(鱼卵3种,仔稚鱼8种),其次是2009年和2011年,2008年种类数最少(鱼卵1种,仔稚鱼5种)。优势种年间更替明显,长蛇鲻(Saurida elongata)、虾虎鱼(Gobiidae spp.)和中华小公鱼(Stolephorus chinensis)在2005年是优势种,2008年优势种为鳀鱼(Engraulis japonicus),2009年优势种为鳀鱼、寡鳞飘鱼(Pseudolaubuca engraulis)、虾虎鱼等,2011年虾虎鱼和小公鱼(包括小公鱼属未定种Stolephorus spp.和中华小公鱼Stolephorus chinensis)成为优势种。2005年鱼卵和仔稚鱼数量分布的密集区在嵊泗列岛附近水域,2008年鱼卵和仔稚鱼出现较少,未出现明显的数量密集区;2009年鱼卵数量较少,仔稚鱼数量较多,密集区主要分布在在长江口以外123°E附近水域;2011年鱼卵主要分布在在长江北支口门外附近水域,仔稚鱼在调查区内分布相对均匀。     

Survival of glochidial larvae of the freshwater pearl mussel, Margaritifera laevis (Bivalvia: Unionoida), at different temperatures: a comparison between two populations with and without recruitment

The viability of free-living glochidia of the freshwater pearl mussel (Margaritifera laevis) was studied in the laboratory at water temperatures of 10 degrees C, 15 degrees C and 20 degrees C. To obtain glochidia, gravid female mussels were collected from the Chitose River, inhabited by adult and juvenile mussels, and from the Abira River, where only adult mussels were found. Daily survival rates of glochidia from each population at various water temperatures were significantly different, and survival time was longest at the lowest temperature in each population. Maintenance of some field mussel populations might become difficult at higher water temperatures due to the short survival time of glochidia and expected low density of host fish. Daily survival rates of glochidia were compared between the Abira population at 15 degrees C and the Chitose population at 20 degrees C, since these temperatures were close to the mean water temperature during the period of glochidial release in the respective rivers. Daily mean survival rates were significantly different between the Abira population at 15 degrees C and the Chitose population at 20 degrees C. Mean glochidial survival rate for the Chitose population changed from 85.3% to 66.2% from 9 to 13 h, whereas that for the Abira population dropped suddenly from 80.4% to 34.2% from 10 to 14 h after the initiation of experiment. Absence of juveniles in the Abira River might have been caused by the low glochidial viability. Survival times of free-living glochidia in Margaritiferidae tend to be shorter than in other families in Unionoida. A trade-off is suggested between high fertility and low glochidial survival rate in Margaritiferidae.