The effects of temperature and food on copepodite development,growth and reproduction in three species of Boeckella (Copepoda; Calanoida)

Three species of Boeckella (B. triarticulata, B. dilatata and B. hamata) were reared from copepodite I to adult at three naturally fluctuating food levels and three temperatures in a 3 × 3 × 3 factorial design. Development times, lengths, times to produce the first clutch, clutch sizes, egg voumes, interclutch times, infertile clutches, total egg production, total reproductive time and mortality were measured. Development times for the three species were surprisingly similar but mortality differed among the treatments. The three species differed in their reproductive strategies. B. triarticulata, the largest species, produced a few large clutches. B. dilatata, the smallest species, produced many small clutches and invested the most energy per egg. B. hamata produced larger clutches than B. dilatata but not as many. B. hamata was the most tolerant of low, food levels and exhibited the most plasticity across the treatments. Thus, greater plasticity in life history characters is associated with survival in a wider-range of conditions.     

The biogeography of three Boeckella species (Copepoda: Calanoida) in New Zealand

The New Zealand distributions of three species of Boeckella (Copepoda, Calanoida), B. triarticulata, B. dilatata and B. hamata are mapped. B. triarticulata is primarily a pond dweller but is also found in reservoirs and shallow lakes. B. dilatata is mainly found in the deeper glacial lakes and ponds in the central region of the South Island and B. hamata has a more widespread distribution in lakes and ponds in the South Island and lower half of the North Island. Differences in temperature optima, food requirements and dispersal ability among the three Boeckella species are related to vicariant events to explain their distribution in New Zealand.     

Variations in the embryonic development times and hatching success of three Boeckella species (Copepoda: Calanoida)

Embryonic development times of Boeckella triarticulata, B. dilatata and B. hamata are compared. Two species, B. triarticulata and B. hamata had widely varying embryonic development times. Variable development times often resulted in greater hatching success.     

Development,Growth and Survivorship of Juvenile Calanoid Copepods on Diets of Cyanobacteria and Algae

Nauplii and immature copepodites of Boeckella triarticulata, B. hamata and B. dilatata were tested for their ability to survive and grow on monospecific diets of four species of filamentous cyanobacteria, Cyclotella (Cy) and Cryptomonas (Cr) at 2 mg dry weight 1⁻¹. Cr supported the development from nauplius to adult of all three calanoid species; complete development on other diets occurred only in B. dilatata on Cy and Anabaena oscillarioides (Ao). Differences between nauplii and copepodites of B. dilatata and B. hamata in survivorship and development on diets of Cy, Anabaena flos-aquae (Af), Ao and Nostoc sp. 2 (N2) imply ontogenetic shifts in resource utilization with developmental phase. Ranked in order of their ability to support the development of juvenile boeckellids the foods were Cr > Cy > Ao > N2 > Af > Nostoc calcicola = no food.     

Effect of changes in resource level on age and size at metamorphosis in Hyla squirella

Recent experiments suggest that timing of metamorphosis is fixed during development in some anurans, insects, and freshwater invertebrates. Yet, these experiments do not exclude a growth rate optimization model for the timing of metamorphosis. I manipulated food resources available to larvae of squirrel treefrogs (Hyla squirella) to determine if there is a loss of plasticity in duration of larval period during development and to critically test growth rate models for the timing of metamorphosis. Size-specific resource levels for individual tadpoles were switched from low to high or high to low at three developmental stages spaced throughout larval development. The effects of changes in resource availability on larval period and mass at metamorphosis were measured. Switching food levels after late limb bud development did not significantly affect larval period in comparison to constant food level treatments. Therefore, developmental rate in H. squirella is better described by a fixed developmental rate model, rather than a growth rate optimization model. The timing of fixation of developmental rate in H. squirella is similar to that found in other anuran species, suggesting a taxonomically widespread developmental constraint on the plasticity of larval period duration. Mass at metamorphosis was not significantly affected by the timing of changes in food levels; the amount of food available later in development determined the size at metamorphosis. Larval period and mass at metamorphosis were negatively correlated in only one of two experiments, which contrasts with the common assumption of a phenotypic trade-off between decreased larval period and increased mass at metamorphosis. Received: 19 August 1996 / Accepted: 20 June 1997     

Calanoid copepods feeding on algae and filamentous cyanobacteria: rates of ingestion, defaecation and effects on trichome length

The relative abilities of freshwater calanoid copepods to grazealgae and filamentous cyanobacteria were examined in three speciesof Boeckella (B.triarticulata, B.hamata, B.dilatata) fed Cydotella,Cryptomonas and two species of Nostoc and Anabaena. Althoughrates of ingestion were highest on Cryptomonas, all the Boeckellaspecies consumed cyanobacteria, some species at similar ratesto Cyclolella. Faecal production on the foods was highest onCydotella and, in B.triarticulata, higher on A.flos-aquae andNostoc sp. 2 than on Cryptomonas. At 1 mg l^–1 of thesecyanobacteria, female B.triarticulata voided 70% by volume ofthe material they ingested as compact faecal pellets. By theirgrazing they also decreased dramatically the trichome lengthsof A.flos-aquae, A.oscillarioides and Nostoc sp. 2, therebypossibly altering the potential susceptibility of these filamentouscyanobacteria to grazing by other zooplankton.     

Resource partitioning of Calamoecia lucasi Brady and Boeckella triarticulata (Thomson) (Copepoda:Calanoida) in an Australian reservoir

In Lyell Reservoir the food niches of Calamoecia lucasi and Boeckella triarticulata appear to be substantially separated by food type and/or food size. Large B. triarticulata eat a wider size range of food particles and exhibit greater dietary richness and breadth than do the small C. lucasi, even though the dietary richness and breadth for the two calanoid species fluctuate through time. The dietary overlap is also variable but is generally low, ranging from 0.329–0.752 in terms of Schoener's index.     

The naupliar stages of Cyclopina yutimaete Lotufo (Cyclopinidae,Cyclopoida)

The six naupliar stages of Cyclopina yutimaete Lotufo are described and compared to other cyclopoid nauplii. They seem more similar to freshwater cyclopoid nauplii than to marine species. The hirsute aspect of the last segment of the antennule is of diagnostic value for these nauplii.     

Larval development of Octomeris sulcata Nilsson-Cantell (Cirripedia: Thoracica: Chthamalidae) from Japan and Korea

Embryos obtained from gravid adults of the chthamalid barnacle Octomeris sulcata Nilsson-Cantell from Japan and Korea were cultured through six naupliar stages to the cyprid and juvenile barnacle stage in laboratory conditions, fed either the diatom Skeletonema costatum (Grev.) Cleve or the dinoflagellate Prorocentrum minimum (Pavillard) Schiller. The nauplii were planktotrophic and, depending on diet, reached the cyprid stage 9 or 17 days after hatching in individual cultures at 22 °C with 24 h illumination. The survival rate was higher and the duration of the naupliar stages was shorter when fed P. minimum rather than S. costatum. This is probably due to the presence of feathered setae on the antennae. Feathered or plumose setae in nauplii of different cirripede taxa are apparently linked to the type of phytoplankton in the seas when these taxa first evolved.The larval stages of O. sulcata are described, and morphological differences between larvae reared from Japanese andKorean adults are compared. The polygonal cephalic shield and unilobed labrum, a pair of posterior shield spines after naupliar stage IV, feathered setae and a hispid seta on the coxa of the antenna, a cuspidate seta on the mandible, and the gnathobase of the antenna are important in distinguishing the nauplii of this species from other species, including Chthamalidae.     

Effects of temperature and salinity on the larvae of two species of rhizocephalan (Crustacea: Cirripedia)

Summary

Responses of larvae of two rhizocephalan species to changes in seawater temperature and salinity were studied under laboratory conditions. Peltogasterella gracilis parasitizes the hermit crab Pagurus pectinatus, which occurs at stable salinity and gradually changing temperature in summer. Sacculina polygenea is a parasite of the crab Hemigrapsus sanguineus, which lives in the intertidal zone in summer where salinity and temperature can fluctuate during the day. The development of both species is comprised of five naupliar stages and the cyprid stage, and it was considered successful if more than 50% of the nauplii attained the cyprid stage. P. gracilis nauplii successfully developed at 12–20°C and 30–34‰, but at 22°C successful development occurred in a narrower salinity range (32–34‰). All nauplii died both at 25°C and in 26‰. S. polygenea nauplii successfully reached the cyprid stage at higher temperatures (18–25°C) and a wider salinity range (18–34‰) than P. gracilis nauplii, but at 12°C and 16‰ larval development of S. polygenea was suppressed. Under favorable conditions, naupliar development lasted 3.5 days in P. gracilis and 2–3 days in S. polygenea. The cyprids of both rhizocephalan species demonstrated a greater resistance to temperature and salinity changes than nauplii. However, P. gracilis cyprids were active in a narrower salinity range (16–34‰), as compared to S. polygenea cyprids (8–34‰). Under favorable conditions the cyprids of both species survived for 6 to 10 days.     

Copepod nauplii use phosphorus from bacteria,creating a short circuit in the microbial loop

In subtropical oceans phytoplankton carbon: phosphorus (C : P) ratios are high, and these ratios are predicted to increase further with rising ocean temperatures and stratification. Prey stoichiometry may pose a problem for copepod zooplankton nauplii, which have high phosphorus demands due to rapid growth. We hypothesised that nauplii meet this demand by consuming bacteria. Naupliar bacterial and phytoplankton carbon and phosphorus ingestion, assimilation and incorporation were traced using ³³P and ¹⁴C radioisotopes. Bacterial carbon was incorporated four times less efficiently into biomass than phytoplankton carbon. In contrast, bacterial and phytoplankton phosphorus were incorporated at similar efficiencies, and bacteria could meet a substantial amount of naupliar phosphorus requirements. As parts of the ocean become more oligotrophic, bacteria could help sustain naupliar growth and survival under suboptimal stoichiometric conditions. Thus, nauplii may be a shortcut for phosphorus from the microbial loop to the classical food web.     

The fauna of athalassic saline waters in Australia and the Altiplano of South America: comparisons and historical perspectives

Similarities and differences between the fauna of inland saline waters in Australia and on the Altiplano are explored and explanations sought.Elements common to both continents include the calanoid copepod genus Boeckella (B. triarticulata in Australia, B. poopoensis and B. meteoris in South America) and the cladoceran genus Daphniopsis. Salinity data for Altiplano lakes are given for six species of Boeckella and for Daphniopsis.Ostracods have adapted to the open water of saline lakes in Australia but not in South America, a difference that may reflect past differences in the degree of predation by birds. In South America, diatoms are grazed by the flamingos Phoenicoparrus andinus and P. jamesi, while in Australia the main diatom grazer is probably the aquatic oniscoid isopod Haloniscus searlei. However, at least four species of flamingos were present in Australia during the late Cenozoic and one or more of these may well have grazed diatoms. The extinction of diatom-grazing or carnivorous flamingos, or both, in Australia may have been factors in the unique colonization of inland saline waters by H. searlei.     

The Nauplius Larva of Crustaceans: Functional Diversity and the Phylotypic Stage

SYNOPSIS. The crustacean nauplius larva is a development stagecharacterized by the presence of three pairs of head appendages.All crustaceans pass through the naupliar stage whether embryonicallyor as freeliving larvae. The nauplius is thought to be the phylotypicstage and represent a fundamental developmental constraint incrustaceans. However, free-living nauplii are primitive andI present evidence that this form is functionally plastic, e.g.,locomotory modes are diverse even in closely related species.I argue that this functional plasticity allowed the persistenceof nauplii in the early evolution of crustaceans and, as a consequence,naupliar development became a deep-seated feature of crustaceans.Thus, we see nauplii as phylotypic. This suggests that, in spiteof the presence of phylotypic stages in various phyla, phylotypyitself may not represent a similar, underlying developmentalconstraint in every case.     

Population Dynamics of Crustacean Zooplankton in a Mesotrophic Lake,with Emphasis on Boeckella hamata BREHM (Copepoda: Calanoida)

The crustacean zooplankton in Lake Mahinerangi, a polymictic, mesotrophic reservoir, were studied for 19 months. The cladocerans, Bosmina meridionalis and Ceriodaphnia dubia, had unimodal patterns of abundance with peak densities in summer; cyclopoids had a single peak of maximum abundance in autumn and Daphnia carinata showed a bimodal pattern with peak densities in early summer and early winter. The strong seasonality in abundance of zooplankton in Lake Mahinerangi distinguishes this lake from other temperate lakes in New Zealand and may reflect its cool winter temperatures (< 5 °C for 2 months). A calanoid, Boeckella hamata, bred throughout the year and was the dominant species numerically. Instar analysis indicated that there were at least three, and possibly four, generations per year. Instantaneous birth and death rates were low with annual mean values (0.036 and 0.057, respectively) that were 2-3.5 times less than those recorded in a population of the same species in Lake Pounui, but within the range of those recorded in calanoid populations elsewhere in New Zealand. The Boeckella population in Lake Mahinerangi appears to be controlled largely by temperature, parasitism and food, with predation having no, or a negligible, effect.     

Predation on and by pelagic Turbellaria in some lakes in Brazil

Planktonic Turbellaria are of common occurrence in both natural and man-made lakes in Brazil. Experiments were performed in 1987 and 1989 to determine which zooplankton species are consumed by predatory Mesostoma sp. from three natural lakes in the Rio Doce Valley. Experiments were also performed in 1989 with a yet unidentified flatworm from Barra Bonita reservoir. Both predators consumed Daphnia and Ceriodaphnia at a high rate: 4 individuals per day in the case of Mesostoma sp., a large species and 1.5 ind day^–1 in the case of the smaller species from Barra Bonita reservoir. Consumption of copepod nauplii, copepodids and adults was much lower, and Ostracoda were not consumed at all. Experiments on food selectivity showed a clear preference by the flatworms for cladocerans.In the lakes studied, flatworms are heavily preyed upon by larvae of Chaoborus and by Mesocyclops species.Turbellaria densities in the natural lakes were around 300 individuals per cubic meter, whereas in Barra Bonita reservoir, 1000 individuals per cubic meter was a mean value in a fifteen days study.Federal University of São Carlos - Laboratory of LimnologyUniversity of São Paulo - Canter of Water Resource and Applied EcologyPost-graduate student - University of São Paulo     

Life cycle of Boeckella poppei Mrazek and Branchinecta gaini Daday (King George Island, South Shetlands)

In Lake Wujka, a shallow, polymictic Antarctic lake situated at 15 m from the seashore, several yearly cohorts occur of the copepod Boeckella poppei and one of the fairy shrimp Branchinecta gaini. There is circumstantial evidence that the two species compete for food, and perhaps adult fairy shrimp feed on the nauplii of the copepod. Both species are positively influenced by a measure of salinity. However, when autumn storms massively sweep seawater into the lake, all fairy shrimp are wiped out; no hatching occurs until next spring. In B. poppei, some nauplii and copepodites survive or hatch after the salt flows out of the lake. This is an advantage to the copepod that may balance its coexistence with the shrimp. Its cycle is, however, aborted by the freezing of the lake. In contrast to many other Antarctic lakes, the life cycle of the crustaceans is therefore controlled by salinity rather than freezing.     

Long-term development of the crustacean plankton in the Saidenbach Reservoir (Germany) – changes,causes, consequences

The rates of development and food intake of the copepod Temora longicornis (Müller) were studied using artificial blooms of Phaeocystis globosa Scherffel under different conditions of nutrient limitation. Mesocosms with 800 l of natural seawater were manipulated by inoculation with cultured P. globosa and by addition of nitrogen and/or phosphorus, to obtain N- or P-limited blooms of P. globosa. During development and ageing of these blooms, water from the mesocosms was used as medium for incubation of nauplii of T. longicornis. Only moderate rates of naupliar development as well as high rates of mortality were observed, irrespective of major differences of nutrient conditions and density of P. globosa. Grazing by the nauplii on P. globosa seemed to be low, suggesting a low food quality of this alga at all physiological conditions studied. The results of this study indicate a low capability of T. longicornis nauplii for control of nuisance algal blooms caused by P. globosa.     

Cannibalistic behaviour of rock-pool copepods: An experimental approach for space, food and kinship

Studies on cannibalism in harpacticoid copepods are restricted to predation on naupliar larvae in rock-pool harpacticoids of the genus Tigriopus. An earlier experimental study on the Mediterranean copepod Tigriopus fulvus indicated that females recognized their own larvae and preferentially preyed on nauplii other than their own. In a series of laboratory experiments, we tested if there were differences in naupliar predation as a function of crowding, food level and sex in Tigriopus brevicornis and T. fulvus. Results show that cannibalism was restricted to the first larval stages (N1 and N2). Both food availability and adult density significantly affected the predation rate. Contrary to earlier suggestions, adult males also preyed on the nauplii. We found no evidence that adults spare their own offspring, for neither T. fulvus nor T. brevicornis.This is in accordance with what one would expect for species having the life history characteristics of Tigriopus, i.e.: multiple broods and large number of offspring. Earlier results indicating parental care in Tigriopus must be taken with caution.     

The production and ingestion of faecal pellets by nauplii of marine calanoid copepods

The downward transport of organic matter as zooplankton faecalmaterial is influenced by copepods which fragment, ingest andrecycle some of the pellet contents. Most of this activity hasbeen attributed to the later copepodite stages and the adults,but little is known about the role of nauplii. Stage-relateddefaecation rates during the naupliar development of two speciesof copepod, Calanus helgolandicus and Pseudocalanus elongatus,were quantified in a series of laboratory experiments. The productionof faecal material commenced soon after the appearance of theNIII in both species and increased throughout naupliar development.The causes of the increase were the formation of larger pelletsby later stages in Calanus and an increased rate of productionby Pseudocalanus. Calanus nauplii, when supplied with algalfood at concentrations that would support full naupliar development,ingested or broke up the pellets of the smaller Pseudocalanusspecies at rates of 1.15 pellets nauplius^–1 h^–1This consumption increased to 2.96 pellets nauplius^–1h^–1 when the concentration of algal food was reduced toa limiting level. Pseudocalanus was not able to consume thepellets of Calanus. Ingestion of Pseudocalanus faecal pelletsby Calanus could supply a nutritional benefit to a food-limitednauplius.     

Combined effect of cyprid age and lipid content on larval attachment and metamorphosis of Balanus amphitrite darwin

Various algal diets of different lipid content and composition were used to rear batches of naupliar larvae of Balanus amphitrite. The cyprids in these larval batches differed in lipid content and were used to investigate the combined effect of cyprid lipid content and cyprid age on attachment and metamorphosis. For this purpose, cyprids were aged for 0,3 and 6 d at 8°C prior to utilization in laboratory attachment assays. The percentage attachment of cyprids with similar lipid content differed significantly among the three age categories. A strong and a weak positive relationship between cyprid lipid content and attachment were monitored in young and old cyprids, respectively. A significant interaction (two‐way ANOVA) between cyprid age and lipid content was observed, indicating that these factors jointly affect larval attachment and metamorphosis in B. amphitrite from the beginning of the cyprid stage.