Effects of experimental conditions on the feeding rate of Mysis mixta (Crustacea,Mysidacea)

Predation by the Baltic Sea mysid Mysis mixta onnewly hatched Artemia sp. and culturedDaphnia magna was examined in the laboratory. Wedesigned experiments to study the effects onconsumption rate of different experimental conditions:light, container size, diel variation, duration ofadaptation period, starvation and the duration of afeeding experiment.Consumption differed significantly between mysids keptin bright light vs mysids in complete darkness, withabout twice the consumption in darkness. Acclimationto light conditions prior to the experiment did notinfluence this result. The duration of an experimenthas large effect on estimated consumption. Predationrates in 1-h experiments were up to 60% higher thanthose recorded in 4-, 12- and 24-h incubations.Consumption rates of starved mysids were significantlyhigher (27% on average) than that of unstarvedindividuals. No significant diel variation inconsumption was observed over an experimental periodat 36 hours. We found a tendency, however notstatistically significant, that the food consumptionincreased when the container size ws increased between1 and 8 l.     

Elemental composition of Mysis mixta (Crustacea, Mysidacea) and energy costs of reproduction and embryogenesis under laboratory conditions

Mysis mixta were reared under laboratory conditions (temperature: 9-10 degrees C; salinity: 7 per thousand, ad libitum food). Dry weight, ash, total carbon and nitrogen content of mysids (muscle tissue, eggs, and embryos of different developmental stages) have been analyzed. We found significant variations in ash content and elemental composition during growth and maturation for both sexes. The proportion of carbon in abdominal muscle decreased gradually from juveniles with body weight of 3-4 mg (42.9%) to males and gravid females ( approximately 40.0%). The nitrogen content was relatively constant (11.4% in average) with significant differences only between juveniles (11.3%) and mature females (11.6%). In embryos, carbon and nitrogen content were highest in early stages (58.6 and 14.3%, respectively). By the end of the marsupial development, carbon had decreased to 51.4% and nitrogen to 12.6%. The C:N ratio reflected the change in somatic carbon content, and the ratio decreased 6.2% from juveniles to gravid females, indicating lipids to be an energy source during maturation and reproduction. The weight-specific female investment in reproduction increases with body size. In gravid females, intersegmental growth during brooding period was observed, while males appear to store energy only for copulation and die after mating. Ontogenetic variation in body composition has implications for elemental budgets of M. mixta, its value as prey for fish and in modeling energy and nutrient cycling.     

Are marine planktonic invertebrates food limited? The case of Mysis mixta (Crustacea,Mysidacea) in the Baltic Sea

Summary Linear regression analysis of field data from a coastal area of the Baltic Sea indicated that growth of the zooplanktivorous Mysis mixta was food limited. No statistically significant effects of temperature on growth were detected.     

Seasonal variation in lipid and fatty acid composition of ice algae from the Barents Sea

The fatty acid compositions of neutral lipid, glycolipid and phospholipid fractions from ice algae sampled from the Barents Sea in spring and autumn were examined for seasonal differences. The ice-algal assemblages were dominated by diatoms. In spring, Nitzschia frigida was the most common species whereas resting stages of Thalassiosira bioculata and Actinocyclus cf curvatulus predominated in autumn. With the exception of one spring sample, neutral lipids predominated over glycolipids and phospholipids in all algal samples. The lipid fractions displayed characteristic fatty acid compositions. In the spring samples the major fatty acids of the neutral lipid fraction were 16:0, 16:1(n-7) and 20:5(n-3) whilst the glycolipid fraction was characterised by higher levels of 20:5(n-3) and C16 polyunsaturated fatty acids, particularly 16:4(n-1). Phospholipids contained higher levels of 22:6(n-3) than the other two lipid fractions although 20:5(n-3) was still the major polyunsaturated fatty acid. In the autumn samples, the neutral lipid fraction contained higher proportions of saturated fatty acids and 16:1(n-7) than the two polar lipid fractions and 22:6(n-3) was most abundant in phospholipids. As with the spring samples, 20:5(n-3) was the major polyunsaturated fatty acid in all lipid fractions of the autumn algae. Overall, the fatty acid compositions of the lipid fractions from spring and autumn algal samples were similar and are consistent with diatoms being the predominant group in the ice algae studied. The high level of neutral lipids observed in both spring and autumn samples suggests that the production of neutral lipids is characteristic of ice algae regardless of season. Nevertheless, some species-specific differences in lipid production may exist since the neutral lipid content of autumn samples containing mainly A. curvatulus was substantially higher than those in which T. bioculata predominated. Received: 26 September 1997 / Accepted: 12 January 1998     

Seasonal variations in the biochemical composition and lipoperoxidation of Hyalella curvispina (Crustacea, Amphipoda)

We assessed the effect of seasonal variations on the biochemical composition and lipoperoxidation of an amphipod crustacean, Hyalella curvispina, which inhabits the coastal plain of the state of Rio Grande do Sul, and correlated this with information on the biology of the species. The animals were collected monthly from September 2003 to August 2005, in Gentil Lagoon, Tramandaí, Rio Grande do Sul, Brazil. Glycogen levels, total proteins, total lipids, triglycerides, and lipoperoxidation were measured for each sex separately. The results suggest that these animals have seasonal storage and degradation of the energy substrates investigated. During summer, glycogen, total lipids, and triglycerides were stored, and were utilized especially during autumn and winter. Proteins were utilized differently in males and females. Females stored proteins especially in spring and used them in summer; whereas males stored proteins especially in spring and used them in winter. The levels of lipoperoxidation during the year differed between females and males. These variations may be related to biotic factors (e.g., reproduction period and others) and to abiotic factors (e.g., water temperature, salinity and others).     

Seasonal variation in fatty acid composition of silver pomfrets,Pampus argenteus (Euphrasen), in Kuwait waters

Proximate and fatty acid composition of wild silver pomfrets, Pampus argenteus, were studied in Kuwait waters for a period of 1 year (November 2007–October 2008) to see whether there were any seasonal compositional differences between males and females. Ten adults (five males, five females) were sampled each month during (i) Pre‐spawning (March–May), (ii) Spawning (June–August), (iii) Post‐spawning (September–November), and (iv) Winter (December–February). Both sexes had significantly (P < 0.05) higher whole body moisture and lower crude protein and lipid contents in winter compared to the respective males and females sampled in other seasons. However, females had significantly higher (9.1%) lipid content during the pre‐spawning season than females in other seasons (7.0–8.2%). The most abundant fatty acid in whole body lipid in both sexes was C16 followed by C18:1n‐9, which accounted for about 31–35% and 22–24% of total lipids, respectively. Males in the pre‐spawning and spawning seasons had significantly higher total monosaturated fatty acids (MUFA) than males and females in post‐spawning and winter. Males had significantly higher total polyunsaturated fatty acids (PUFA) during post‐spawning seasons than females in pre‐spawning and winter seasons. However, there were no significant differences (P > 0.05) in total saturated fatty acids (SFA), PUFA, EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid) or n‐3/n‐6 ratios between respective males and females in different seasons. Livers in males had significantly (P < 0.05) higher MUFA, SFA, PUFA, EPA and DHA than respective females in all months during the spawning season. Female gonads had significantly (P < 0.05) higher MUFA and PUFA but lower SFA content than males in different months during the spawning season. In contrast to the liver, the gonad DHA content and n‐3/n‐6 ratios in females were significantly higher than in males. The gonads from both sexes contained more than double the amount of EPA present in liver; in the case of DHA this was more than three‐fold higher in female gonads, but not in males. Thus, the presence of higher proportions of PUFA, EPA and DHA in gonads, particularly in eggs of silver pomfret, indicates their need for these fatty acids, which may be used as a guideline for dietary essential n‐3 fatty acid requirements for feed formulation of this species. A higher content of DHA in eggs also indicates the higher requirement for DHA in the broodstock diet of silver pomfret.     

Diet and predators of Tenagomysis tasmaniae Fenton, Anisomysis mixta australis (Zimmer) and Paramesopodopsis rufa Fenton from south-eastern Tasmania (Crustacea:Mysidacea)

The diets of three mysid species Tenagomysis tasmaniae Fenton, Anisomysis mixta australis (Zimmer) and Paramesopodopsis rufa Fenton were investigated together with a number of potential fish predators by gut contents and stable isotope analysis. Gut content analysis of the three mysis species revealed that all have an omnivorous diet, although the stomachs of P. rufa contained a greater percentage of crustacean remains, whereas the stomach contents of T. tasmaniae were largely composed of fragments of macroalgae. The stomach contents of A. mixta australis were composed mainly of fine particulate matter. Diel feeding rhythms were examined from mysids collected during a 24-hour sampling session in October. P. rufa appeared to be primarily a day-time feeder while T. tasmaniae fed more intensively at night. The results for A. mixta australis were inconclusive. Gut contents analysis of fish collected at the study site revealed predation on mysids by Arripis trutta (juveniles), Aldrichetta forsteri, Vincentia conspersa and Pseudolabrus fucicola. The mysid species most frequently eaten was Tenagomysis australis Fenton. The mysid species most frequently eaten was Tenagomysis australis Fenton.     

Doxomysis algoaensis, a new mysid species (Crustacea: Mysidacea) from Algoa Bay (South Africa)

Doxomysis algoaensis sp.nov. is described from Algoa Bay, South Africa where it is common in nearshore marine waters just beyond the breaker line. D. algoaensis sp.nov. is morphologically similar to D. australiensis, but can readily be distinguished by the shape and armature of the telson and the length of the exopod of the fourth male pleopod. The apical cleft is one fifth the telson length in the former species and one third the length in D. australiensis. The telson apex on each side of the cleft is also armed with five and four stout spines in the two species, respectively. In D. australiensis, the exopod of the fourth male pleopod is almost three times the length of the endopod; in D. algoaensis sp.nov., the exopod is only slightly longer than the endopod. Other distinctive features of D. algoaensis sp.nov. include the maxillary palp, which is only slightly broader than long and the greater number of spines on the endopod of the uropod.     

Production and biomass of Tenagomysis tasmaniae Fenton, Anisomysis mixta australis (Zimmer) and Paramesopodopsis rufa Fenton from south-eastern Tasmania (Crustacea: Mysidacea)

Annual production estimates were calculated for Tenagomysis tasmaniae, Anisomysis mixta australis and Paramedopodopsis rufa using the size-frequency and Petrovich methods. Annual production for T. tasmaniae was more than twice that for P. rufa and A. mixta australis. The P:B ratio was however , higher for a. mixta australis than T. tasmaniae and P. rufa. The P:B values for the three species are among the highest ratios reported for mysids.     

Seasonal variation of fungal propagules in a fruit market environment, Nagpur (India)

The concentration of airborne fungal spores in a marketenvironment was examined to provide basic information needed to evaluatethe importance of varying levels and heterogeneity. Sampling has beencarried out by rotorod sampler and exposed Petri plate method to obtainthe quantitative and qualitative estimations respectively.Aspergillus was the most frequent and predominant genusdetected. Cladosporium, Penicillium and Alternariaspores were also fairly abundant which are well known as allergenic andpathogenic. The high concentration of airborne spores was recordedduring December–January. While the maximum concentration ofAspergillus was found during summer months in the marketenvironment.     

A new species of Gastrosaccus (Crustacea,Mysidacea) from Algoa Bay (South Africa)

The effect of temperature on growth rate, shell size and shell shape in Krithe praetexta praetexta (Sars) was studied in four thermocultures. From July 1995 to June 1996, the cultures were kept in a continuously flowing open system pumping water from the intermediate watermass of the Gullmarn fjord, west coast of Sweden. Three cultures were kept at constant temperatures of 5, 10 and 14 °C, respectively. The fourth (reference) culture largely followed the natural variation in temperature. At the termination of the experiment, all living ostracods from a 125 m sieve were sampled from the cultures. Population age structures were analysed for the various thermocultures of K. praetexta praetexta. These were more shifted towards later ontogenetic stages with higher temperature, i.e. the ontogenetic development was more rapid in the warmer cultures. An alternative explanation is due to diapause causing cohorts to accumulate in some ontogenetic stages only when the temperature is constant. The differences in shell size of K. praetexta praetexta among the thermoconstant cultures were not statistically significant.     

Population dynamics of Tenagomysis tasmaniae Fenton,Anisomysis mixta australis (Zimmer) and Paramesopodopsis rufa Fenton from south-eastern Tasmania (Crustacea:Mysidacea)

The population dynamics of a coastal mysid community was examined at One Tree Point in southern Tasmania over a 12-month period, including three 24-hour sampling sessions. Fourteen mysid species were recorded. Zonation patterns, life-history and diel activity of the three most abundant species, Tenagomysis tasmaniae, Anisomysis mixta australis and Paramesopodopsis rufa were examined. These three species were found in large numbers throughout the year associated with the macroalgal fringe on either side of the bay. Habitat partitioning within this zone of occurrence was evident. T. tasmaniae was the most abundant species (annual mean density 32.4 m^–3), followed by A. mixta australis (annual mean density 20.5 m^–3 ) and P. rufa (annual mean density 11.3 m^–3). The major peaks of abundance of these three species were temporally separate. Breeding was intensive for the three species from spring till late autumn. A cessation of breeding in winter was evident for A. mixta australis and to a lesser extent for P. rufa but T. tasmaniae bred throughout the year although at a reduced rate during winter. Examination of the diel behaviour identified peaks of abundance at sunrise and sunset for T. tasmaniae; P. rufa was caught in greater numbers at night, but no consistent pattern was observed for A. mixta australis.     

Breeding biology of Tenagomysis tasmaniae Fenton,Anisomysis mixta australis (Zimmer) and Paramesopodopsis rufa Fenton from south-eastern Tasmania (Crustacea: Mysidacea)

The number, size and developmental stage of young in the brood pouch of female Tenagomysis tasmaniae, Anisomysis mixta australis and Paramesopodopsis rufa was recorded throughout the year. Breeding was intensive from spring till the end of autumn for the three species. Calculation of the egg ratio for each species showed that their major reproductive peaks occurred during spring and summer. A winter depression in the breeding cycle was observed for T. tasmaniae and P. rufa, but A. mixta australis ceased breeding during winter. Seasonal variation in the length of gravid females and number of young carried was evident for these three species. Females were longer in spring and summer and carried more young than in autumn and winter. A linear relationship between female length and brood size was demonstrated for each species; annual and seasonal equations were calculated for females carrying each developmental stage. The seasonal equations showed that for a female of given length fecundity was greater during spring than any other season. Natality was estimated to be highest during late spring, summer and early autumn for the three species. No seasonal variation in the size of eggs was evident for the three species. The reproduction pattern of T. tasmaniae, A. mixta australis and P. rufa appears to be very similar to that reported for the majority of iteroparous coastal temperate mysids throughout the world.     

Seasonal, genetic and age variation in non-esterified fatty acid concentrations in the ewe

Plasma samples were collected at intervals of about 2 weeks from about ten 2 1/2 year old, or older, and five 1 1/2 year old ewes of each of the Scottish Blackface, Finnish Landrace and Tasmanian Merino ewes and were assayed for their non-esterified fatty acid (NEFA) concentrations. The NEFA concentrations showed an increase with time for every animal. The NEFA concentrations and their linear increase was least in the Finnish Landrace animals. The increase with time was greatest in the Merinos. There was no difference between the age groups. There was no evidence of any annual, cyclical trend.     

Seasonal distribution and fatty acid composition of littoral microalgae in the Yenisei River

We studied fatty acid (FA) composition of littoral microalgae in the fast-flowing oligotrophic river, the Yenisei, Siberia, monthly for 3 years. Seasonal dynamics of species composition had similar patterns in all the studied years. In springs, a pronounced dominance of filamentous green algae occurred, in summer and autumn diatoms were abundant, and in late autumn and winter epilithic biofilms consisted primarily of cyanobacteria and detritus. In general, FA composition of the algal periphytic community was dominated by 16:0, 16:1ω7, 20:5ω3, 14:0, and 18:3ω3 throughout the studied period. Several groups of FAs, which had peculiar seasonal dynamics, were differentiated by statistical analysis based on a method of correlation graphs. The seasonal changes in FA composition could be partly explained by the seasonal succession of species composition of the community. Besides, we found that populations of both diatom and green algae grown in summer at a higher water temperature were lower in polyunsaturated fatty acids than those in spring, at a lower temperature. Hence, we suppose that the regular seasonal dynamics of FA composition of the studied littoral microalgae was driven both by changes in species composition and by temperature adaptations of the algal populations. The highest content of essential polyunsaturated FAs, eicosapentaenoic and docosahexaenoic acids, in the spring “psychrophilic” populations of diatoms could make them of the higher nutritive value for zoobenthic primary consumers.     

Seasonal variations of total lipids, fatty acid composition, and fucoxanthin contents of Sargassum horneri (Turner) and Cystoseira hakodatensis (Yendo) from the northern seashore of Japan

The present study describes the seasonal changes in lipid components of two brown algae, Sargassum horneri (Turner) and Cystoseira hakodatensis (Yendo), with specific reference to fucoxanthin (Fx) and n-3 (omega-3) polyunsaturated fatty acids (PUFAs). Young thalli of S. horneri were collected from different places, Nesaki and Matsushima, and cultivated in the same place. Total lipids (TL) and Fx contents of S. horneri increased from October or November and reached a maximum in January and then decreased thereafter. TL and Fx of S. horneri originated from Matsushima were always higher than those originated from Nesaki, suggesting that genetic variation might be a reason for the different TL and Fx contents found in both S. horneri seeds from different origin. Similar seasonal variation in the TL and Fx content has been more clearly observed in C. hakodatensis. Maximum TL content of S. horneri and C. hakodatensis reached to more than 14 and 15 % in winter season. These values were much higher than those found in previous studies showing TL content range from 1 to 5 %. Fatty acid composition of lipids from S. horneri and C. hakodatensis also changed seasonally. Total monounsaturated fatty acids showed the lower values from January to April, while there were no big variations in total saturated fatty acids and total n-6 PUFAs. On the other hand, total n-3 PUFAs became highest in winter. Overall, S. horneri and C. hakodatensis harvested from winter to spring will be used as good n-3 PUFA source with high levels of TL and Fx.