The effect of temperature on reproduction in three species of cyclopoid copepods

Megacyclops viridis (Jurine), Macrocyclops albidus (Jurine), and Acanthocyclops vernalis (Fischer) were raised in the laboratory at six temperatures (5, 8, 10, 12, 15 and 20°) and fed a mixture of ciliates (Paramecium caudatum and Colpidium campylum). Data were taken on clutch size, embryonic development time, interclutch period, time to first clutch, sex ratio and longevity.Clutch size, time to first clutch, embryonic development time, interclutch period and longevity are inversely related to temperature. The ratio of males to females in a cohort is independent of temperature.     

Latitudinal diversity patterns of continental benthic copepod species assemblages in the Americas

The diversity, considered as richness (numbers) of genera and species, of continental benthic Copepoda of the Americas was examined. Thirty-three local lists of planktonic and benthic Cyclopidae (Eucyclopinae and Cyclopinae), 21 local lists of epibenthic Harpacticoida (Canthocamptidae), and 8 local lists of interstitial Harpacticoida (Parastenocarididae) were compared. Available data do not allow the rejection of the null hypothesis of no significant difference in diversity of tropical and temperate copepod faunas. For Cyclopidae, 6–15 genera and 6–44 species were recorded from local areas; linear regression analysis showed no significant correlation between latitude and number of genera and species. For Canthocamptidae, 1–13 genera and 3–43 species were recorded locally, with no significant correlation between latitude and number of species; for genera the correlation between latitude and number of genera was strongly positive, but the effect of latitude is small. No relationship between latitude and diversity of the Parastenocarididae was evident from inspection. Endemism of Cyclopidae and Canthocamptidae is significantly greater in South America, as shown by comparisons of Sørensen's similarity coefficient between paired areas. Because of this high degree of endemism, conservation strategies for South American wetland invertebrates should emphasize preservation of many small sites.     

Influence of temperature and food concentration on body size,weight and lipid content of two Calanoid copepod species

Two species of Copepoda Temora longicornis (Müller) and Pseudocalanus elongatus (Boeck) were cultured continuously in the laboratory. Four and three generations, respectively, were raised at 16 different combinations of temperature and food concentration. Prosome length and ash-free dry weight were measured in the adult stage and in Pseudocalanus also in copepodite stage I, and the relation between length and weight was established. In Pseudocalanus also the relative amount of lipid was estimated.Prosome length and length-specific body weight (condition factor) were positively correlated with food concentration. Lipid content in Pseudocalanus was also strongly affected by the concentration of food.Prosome length was negatively correlated with temperature. However, length-specific body weight in Temora was positively correlated with temperature. Therefore, at higher temperature Temora was smaller, but heavier per unit body length. In Pseudocalanus a similar but less significant influence of temperature on length-specific weight was found; lipid content was not significantly influenced by the temperature.Females of Temora had larger length-specific weights than males. In Pseudocalanus the opposite was found, coinciding with a higher lipid content in males than in females.It is discussed that at natural concentrations of phytoplankton body size and weight of copepods are reduced in the North Sea during the major part of the growing-season.     

The effect of seasonal temperature extremes on sediment rejection in three scleractinian coral species

Sedimentation from resuspension following storm surge is a natural occurrence on coral reefs, and scleractinian corals have adapted to effectively reject sediment. However, it is unclear whether the physical ability to reject sedimentation is affected during seasonal temperature extremes. We acclimated three coral species (Montipora aequituberculata, Lobophyllia corymbosa and Fungia fungites), with different active shedding mechanisms, to three temperature treatments (winter minimum, summer maximum and mean). Corals were then exposed to a sediment rejection experiment in which we measured clearance rates and tissue inflation cycles associated with the clearance of sediment. Temperature impacted clearing rates of M. aequituberculata, which exhibited significantly faster sediment rejection under winter temperatures. Fungia fungites, on the other hand, exhibited significantly higher tissue inflation rates under summer temperatures. Although limited in scope, this study demonstrates that temperature can have a strong effect on the response of corals to sedimentation.     

The effect of temperature on the development time and brood size of diaptomus pallidus herrick

Diaptomus pallidus individuals were raised in the laboratory at three temperatures (15, 20, and 25°C) and fed an alfalfa and trout-food diet ad libitum. Data were taken on the development times of the egg, naupliar, and each copepodid stage and the brood sizes of field animals acclimated to the test conditions.The results indicated D. pallidus does not have a temperature range over which its development rate is nearly constant as earlier reported. Rather, the development rate is temperature dependent within the experimental range. Broods produced at 20°C and 25°C were significantly smaller than those produced at 15°C but not significantly different from each other.     

The interacting effect of prolonged darkness and temperature on photophysiological characteristics of three Antarctic phytoplankton species

Photophysiological characteristics of the Southern Ocean phytoplankton species Phaeocystis antarctica, Geminigera cryophila, and Chaetoceros simplex were assessed during 7 weeks of darkness and subsequent recovery after darkness at 4 and 7°C. Chlorophyll a fluorescence and maximum quantum efficiency of PSII decreased during long darkness in a species-specific manner, whereas chlorophyll a concentration remained mostly unchanged. Phaeocystis antarctica showed the strongest decline in photosynthetic fitness during darkness, which coincided with a reduced capacity to recover after darkness, suggesting a loss of functional photosystem II (PSII) reaction centers. The diatom C. simplex at 4°C showed the strongest capacity to resume photosynthesis and active growth during 7 weeks of darkness. In all species, the maintenance of photosynthetic fitness during darkness was clearly temperature dependent as shown by the stronger decline of photosynthetic fitness at 7°C compared to 4°C. Although we lack direct evidence for this, we suggest that temperature-enhanced respiration rates cause stronger depletion of energy reserves that subsequently interferes with the maintenance of photosynthetic fitness during long darkness. Therefore, the current low temperatures in the coastal Southern Ocean may aid the maintenance of photosynthetic fitness during the austral winter. Further experiments should examine to what extent the species-specific differences in dark survival are relevant for future temperature scenarios for the coastal Southern Ocean.     

Effect of photoperiod and temperature on the development of frost hardiness in three Alnus species

The influence of short day and low temperature on cold acclimation of A. crispa (Ait.) Pursh, A. glutinosa (L.) Gaertn. and A. rubra Bong, was investigated. Two clones of each species originating from in vitro propagation were exposed to three daylength/temperature treatments. Periodically plantlets were exposed to controlled freezing temperature in order to evaluate their level of frost hardiness.
Short day (SD) and cold temperature (CT) and long day (LD) and cold temperature (CT) were the most effective treatments for the development of frost hardiness in shoots and roots of the three species tested. Short day (SD) and warm temperature (WT) induced a significant increase in hardiness in shoots of all three species. However, this treatment did not trigger root hardening. A. crispa was found to be the hardiest species followed by A. glutinosa and A. rubra . Intraspecific variation was observed between the two A. glutinosa clones. A glutinosa clone AG8, a Russian provenance, showed a greater freezing resistance than A. glutinosa clone AG2, a German provenance.     

Effect of temperature and food concentration on post-embryonic development, egg production and adult body size of calanoid copepod Eurytemora affinis

Post-embryonic development time, egg production rate and adultbody size of calanoid copepod Eurytemora affinis from Lake Ohnuma,Japan, were determined under six temperature-food conditions(10³,5 x 10³, 10⁴ and 5 x 10⁴ cells ml^–1 at 15°C,5 x 10⁴ cells ml^–1 at 10and20°C) in the laboratory.The measured parameters varied with both temperature and foodconcentration. Development time from hatching to adult femalewas 9.2, 11.4 and 22.8 days at 20, 15 and 10°C respectively,at the highest food concentration. The males developed to adultat one to two days earlier than the females. An effect of foodshortage on development time occurred at the lowest food concentration.This development time was 24.8 days even at 15°C, beingtwice as long as that at the highest food concentration. Prosomelength of these food-limited females was approximately 75% ofwell-fed ones, which reduced by only 10% with increasing temperaturefrom 10 to 20°C. Clutch size (C, eggs clutch^–1) ofwell-fed individuals depended on prosome length of the adultfemale (L, mm), and was expressed as an equation: C = 65.2 L³⁸³. Clutch size of individuals reared at less than 10⁴ cellsml^–1, however, mostly laid below the estimated curve,especially at the lowest food concentration being only 10% ofthat at the highest food concentration. These results suggestthat food availability is a more important factor affectingpopulation growth of E.affinis in Lake Ohnuma than variationof temperature.     

Short communication. The effect of temperature, food concentration and female size on the egg production of the planktonic copepod Acartia bifilosa

Egg production of a brackish water calanoid copepod Acartia bifilosa was measured in the laboratory in different chlorophyll (Chl) a concentrations (0-24 mgr; l^-1) and temperatures 4-24C), and the cephalothorax length and carbon content of females were determined. Egg production was positively correlated both with Chl a concentration and with temperature; highest egg production was obtained with 14-20 g Chl a l^-1 and at 13-18°C. There was also a significant positive correlation between egg production and female length-specific carbon content (g C m^-1). However, no correlation was observed between egg production and cephalothorax length of females. Female carbon content changed during the 3 day experiments; carbon content was positively related to Chl a concentration and negatively related to temperature. We conclude that food availability (Chl a concentration), rather than temperature, limits the egg production of A.bifilosa in the present study area in the northern Baltic Sea. Further, both food concentration and temperature affect egg production not only through the direct effect on the numbers of eggs produced per female, but also through their effect on female carbon content.      

Predatory interactions between a cyclopoid copepod and three sibling rotifer species

SUMMARY 1. Cyclopoid copepod predation on rotifers affects the dynamics and structure of zooplankton communities. We address the differential vulnerability of three sympatric rotifer sibling species belonging to the Brachionus plicatilis species complex. These co-occur with their cyclopoid predator, Diacyclops bicuspidatus odessanus .
2. Using video recording and tracking, we analysed the steps in predation including attack distance, attack angle, and rotifer species swimming in the presence and absence of the predator. Our results show the greater vulnerability of B. rotundiformis (the smallest species) to D. b. odessanus predation, which is associated with a high percentage of attacks after contact. Brachionus plicatilis (the biggest species) is the less vulnerable prey, with low percentage of attacks after contact and captures after attacks. Branchionus ibericus , the intermediate sized species, had also intermediate vulnerability.
3. The differential vulnerability provides insight into the coexistence and seasonal succession of these competing rotifer species. Our results show that the competitive superiority of B. rotundiformis may be balanced by its greater vulnerability to copepod predation.     

The effect of sediment characteristics on the distribution of two subtidal harpacticoid copepod species

Abundances of two harpacticoid copepod species, Enhydrosoma littorale Wells and Zausodes c.f. arenicolus Wilson, were significantly higher in one of two adjacent subtidal, soft-bottom habitats in St. George Sound, Florida (29°54′N : 84°37′48′′W). For Enhydrosoma littorale, a laboratory-preference experiment indicated that sediment-related factors caused the observed distribution. In a series of preference experiments, differences between the sediments of the two habitats in granulometry and organic matter were shown not to account for the preference. Rather, the preference results from differences in the microbes attached to the sediment particles in the two areas. In contrast, Zausodes c.f. arenicolus did nol prefer sediments from its area of high field abundance in laboratory preference experiments, indicating that factors external to the sediment i.e. hydrographic conditions or biological interactions, were responsible for this species' distribution.     

The effect of temperature on asexual population growth of three species of Naididae (Oligochaeta)

The population growth rates of monospecific cultures of asexually reproducingNais variabilis, N. elinguis andPristina aequiseta were determined under laboratory conditions at 8 °C, 12 °C and 20 °C. Two different agar-based culture media were used to promote bacterial populations as a food for the worms. The exponential growth rate (r) of the worm populations was dependent upon species, temperature and culture medium. Highest r-values recorded were forN. variabilis andP. aequiseta at 20 °C (mean population doubling time about 3 days) and the lowest r-value recorded was forP. aequiseta at 8 °C (mean population doubling time about 22 days). The r-values forN. elinguis were generally lower than expected, possibly because conditions in the experimental cultures were less suitable for this species. Temperature, culture medium and species identity also affected the carrying capacity of the cultures. Carrying capacity increased with increase in temperature over the experimental range.P. aequiseta cultures supported significantly higher carrying capacities than theNais cultures at all temperatures.     

The prediction of development rate and the effect of temperature for the meiobenthic copepod,Microarthridion littorale (Poppe)

Specimens of the meiobenthic copepod, Microarthridion littorale (Poppe ), were cultured in the laboratory on substrata consisting of sediment, benthic diatoms, and detrital filtrate. No significant differences were found in egg development times of M. littorale cultured in winter vs. summer, and we suggest several possible interpretations. Egg development time was independent of the number of clutches a female carried in the laboratory, suggesting confidence in estimates of egg development time without knowledge of the number of broods a female has produced. Egg, naupliar, and copepodite development rates were determined over a range of temperatures. Regression analyses indicated that both Bělehrádek's temperature function and a curvilinear model adequately described the relationship between development and temperature for all three developmental stages. A linear model was also adequate to describe copepodite development (Lack of Fit Test, P = 0.05). Eight of the reared females produced egg sacs, allowing us to estimate generation time (egg to egg) as 29.6 days at 25°C and 21.6 days at 33°C. Generation times were compared to those for a closely related benthic copepod, Tachidius discipes. Life history parameters between the two differed, and we advise caution when using predictions of development time derived from a species other than the one being studied.     

Competitor-mediated coexistence: Interactions among three species of benthic macroalgae

Manipulative field experiments were used to determine the mechanism of coexistence of three species of benthic macro-algae (Eisenia arborea Areschong, Halidrys dioica Gardner, and Pterocladiacapillacea (Gmelin)) which occur in a narrow band of substratum from 0.3 to 2.3 m below MLLW on Santa Catalina Island, California. Eisenia forms a canopy and excludes Halidrys from areas beneath this canopy. Pterocladia occurs in the space beneath the Eisenia canopy. Upon canopy removal, Halidrys grows adventitiously, excludes Pterocladia, and preempts all space on the substratum. However, Pterocladia is not physiologically restricted to being an understory plant. When the canopy is removed and Halidrys is prevented from entering the area, Pterocladia flourishes. Pterocladia persists in the community because of its ability to utilize the refuge from its superior competitor, Halidrys, afforded by the Eisenia canopy. Eisenia, the competitive dominant to Halidrys, therefore, mediates the coexistence of Halidrys and its inferior competitor Pterocladia in a manner similar to the role that predators and physical disturbance play in other marine communities.     

The benthic dinoflagellate genus Amphidinium in south-eastern Australian waters,including three new species

Seventeen species of the mainly sand-dwelling genus Amphidinium are reported from south-eastern Australian waters. Three new species are described: A. boggayum, A. mootonorum and A. yuroogurrum. Additional features from previously described species are presented, including non-motile cell stages. Nine of these species are new records for Australia; however, these species are probably widespread and common. Two potentially ichthyotoxic species of Amphidinium were commonly found: A. carterae and A. cf. operculatum. A table of morphological characters is compiled as a step towards recognizing new characters with which to group species of this presently artificially defined unarmoured dinoflagellate genus.     

Factors influencing the degree of sexual size dimorphism within and among calanoid copepod species

Populations of Diaptomus leptopus (Copepoda: Calanoida) and other calanoid copepods exhibit varying degrees of sexual size dimorphism. We examined whether intraspecific or interspecific variation in dimorphism could be explained by allometry, and we examined the relationship between adult size attained and development rate to determine any relationship between the two. We compared the degree of sexual size dimorphism in D. leptopus and in other calanoid copepods inhabiting temporary and permanent habitats. Allometry did not explain variation in sexual size dimorphism within or among populations or among species. Permanence of habitat affected the degree of dimorphism: dimorphism was greater within and among species inhabiting temporary environments. Non-significant differences in development rate were found among populations and significant differences were found between sexes of D. leptopus when reared under identical laboratory conditions: males developed more rapidly than females but there was no general relationship between development rate and adult size. Potential adaptive hypotheses to explain the differences between populations inhabiting temporary and permanent habitats are discussed.     

Transport and particle size distribution of suspended and benthic organic matter in three headwater streams

The breakdown and decomposition of two species of deciduous leaf litter, Fagus sylvatica L. and Salix viminalis L. and two species of aquatic macrophyte Isoetes lacustris L. and Potamogeton perfoliatus L. were examined in an oligotrophic lake. In all cases plant litter in coarse mesh litter bags lost significantly more material than the fine mesh after 1 years submergence in the lake. This however was considered to be the result of physical environmental factors and microbial activity rather than animal processing. The litter was ranked in order of fastest to slowest rates of decay as follows — Isoetes, Potamogeton, Salix and Fagus. Decomposition processes proceeded at a relatively slow rate as a result of low temperatures and low phosphate and mineral ion concentration. The results suggested that there was an accumulation of organic material in the lake.     

The effect of temperature on the activity of three species of Helicid snail (Mollusca: Gastropoda)

The activity of the land snails Cepaea nemoralis (L.), C. hortensis (Müll.) and Arianta arbustorum (L.) was measured over 24 hours at the constant temperatures of 0, 3, 8, 17, 22 and 26°C at 100% relative humidity and with 16 hours light and 8 hours dark. The activity of all three species varies significantly with temperature and light, and there are differences in the activities of the species at each temperature. A. arbustorum is relatively more active than Cepaea at low rather than high temperatures, as is C. hortensis with respect to C. nemoralis , though to a lesser extent. There is little diurnal rhythm in activity at 0°C, but all species become more nocturnal as temperature increases; C. nemoralis is most, and A. arbustorum least nocturnal. The results obtained assist in explaining the observed geographical and local distributions of the species concerned.