Biology of Ixodes (Pholeoixodes) hexagonus under laboratory conditions Part II. Effect of mating on feeding and fecundity of females

The effect of mating on the feeding and fecundity ofIxodes (Pholeoixodes) hexagonus females was studied under controlled laboratory conditions of 22–23°C and 98% relative humidity. The feeding period of mated females was 6–15 days and 11–13 days for unmated females. The mean weight of the engorged mated females was 114.84±45.89 mg, whereas, that of the engorged unmated females was significantly lower (80.61±28.84 mg). During the initial slow feeding period, the weight of mated females increased 6.6 times. At the end of the blood feeding, they had increased their initial weight 35.5 times. Unmated females never entered the rapid engorgement phase and up to 12 days of feeding period their mean weight did not increase more than 9.2 times. The pre-oviposition periods of mated and unmated females were 6–15 days and 4–12 days, respectively. The mean of the egg production efficiency was 40.26±12.47% for mated females and 35.68±12.2% for unmated females. The mean of the mass conversion efficiency was 73.6±13.7% for mated females and 66.48 ±16.55% for unmated females. Sixty per cent of the eggs deposited by mated females hatched whereas only 1% of the eggs deposited by unmated females hatched. These results indicate thatI. hexagonus females possess some predisposition for parthenogenesis and only fertility and not fecundity depends on mating.     

Feeding convergence in South American and African zooplanktivorous cichlids Geophagus brasiliensis and Tilapia rendalli

Synopsis Acará, Geophagus brasiliensis, and red-breasted bream, Tilapia rendalli, are important planktivorous cichlids in southern Brazilian lakes and reservoirs. In laboratory experiments, I quantified behavior and selectivity of different sizes of these two fish feeding on lake zooplankton. Feeding behavior depended on fish size. Fish < 30 mm were visual feeders. Fish 30–50 mm either visually fed or pump-filter fed depending on zooplankton size. Fish > 70 mm were pump-filter feeders. Replicate 1 h feeding trials revealed that, as the relative proportions of prey changed during an experiment, acará (30–42 mm, standard length) and tilapia (29–42 mm) shifted from visual feeding on large evasive copepods to filter feeding on small cladocerans and rotifers. Electivity and feeding rate increased with prey length, but were distinct for similar-sized cladocerans and copepods. Visual/filter-feeding fish had lowest electivities for small and poorly evasive rotifers and cyclopoid nauplii. They fed non-selectively on cyclopoid copepodites, had intermediate electivities for calanoid nauplii and small cladocerans, and had highest electivities for large cladocerans, cyclopoid adults, and calanoid copepodites and adults. Although belonging to different cichlid genera and native to South America and Africa, respectively, acará and red-breasted bream (= congo tilapia) exhibited similar selectivity for zooplankton. Apparently, few stereotyped feeding behaviors have evolved during the acquisition of microphagy in fish. Shift in feeding modes allows these two species to optimally exploit the variable and dynamic patchy distribution of planktonic resources.     

Effect of UVB radiation on the survival, feeding, and egg production of the brackish-water copepod, Sinocalanus tenellus, with notes on photoreactivation

We examined the effects of UVB radiation on hatching success of eggs, survival of various naupliar and copepodite stages, and feeding and egg production of adult females of the brackish-water copepod, Sinocalanus tenellus, by exposure to varying doses of UVB irradiance in the laboratory. Artificial UVB radiation resulted in an increased mortality of eggs, nauplii and copepodites with increasing UVB doses. UVB induced damage was stage-specific with eggs being most susceptible (LD₅₀= 4.1 kJ m^–2 ) and adult females being least susceptible (LD₅₀= 16.7 kJ m^–2). Effects on feeding and egg production of adult females were significantly evident at UVB doses higher than 11.0 kJ m^–2 and 7.0 kJ m^–2, respectively. We also examined the photorepair response of eggs and various developmental stages in simultaneous irradiation of UVB and enhanced PAR. With enhanced PAR there was a considerable recovery against UVB damage, being higher for younger animals than older ones. In nature, however, solar UVB radiation may rarely cause appreciable damage to S. tenellus population due to optically high attenuation properties of their habitat waters.     

The effect of the nanoflagellateTetraselmis suecica on the growth and survival of grunion,Leuresthes tenuis,larvae

Synopsis The nanoflagellateTetraselmis suecica was tested both as the sole food source and as a diet complement toArtemia nauplii for grunion,Leuresthes tenuis, larvae. A total of 4800 grunion larvae, obtained through artificial insemination and incubation, were cultivated under laboratory conditions. Growth and survival rates were registered for 14 days in two experimental series. In the first series the nanoflagellateT. suecica was offered as the sole food source at five different concentrations. Survival and growth increased in agreement with the increase inT. suecica concentration. In the second series,Artemia nauplii were offered at six concentration levels. This series was divided into two groups: the nanoflagellateT. suecica was added to one group at a concentration of 5000 cells ml^–1; the other group was maintained without nanoflagellates. In this series, survival and growth were directly related to nauplii concentration, but significant effects of the nanoflagellates were evident only in relation to the survival; the greatest difference (58% without nanoflagellates vs. 69% with nanoflagellates) was observed at anArtemia concentration of 1000 nauplii 1^–1. The mechanism responsible for increased survival ofL. tenuis larvae in presence of phytoplankton is unclear.     

Experimental studies on the development of Lernaeocera branchialis (Copepoda: Pennellidae): population processes from egg production to maturation on the flatfish host

Quantitative population dynamical information derived from laboratory- and field-based experiments is provided for the fish-parasitic copepod, Lernaeocera branchialis, infecting flounder (Platichthys flesus) and whiting (Merlangius merlangus). Adult, post-metamorphosis females from whiting can produce more than one set of egg-strings. The mean number of eggs in each egg-string pair was 1445. At 10 °C these eggs took about 12.7 d after extrusion before hatching of NI nauplii began. Hatching took up to 12 days to be completed with an exponentially declining pattern of output over this period. In the laboratory about 44% of the egg-string egg population successfully passed through the NI to NII nauplius moult and the NII to copepodid moult to produce infective copepodids, a process lasting about 2 d. The non-feeding copepodids had a maximum survival time at 10 °C of 18 d, with a time to 50% survival of 7.5 d. In laboratory infection experiments at 10 °C, copepodids infected flounder and passed through all their developmental stages to adulthood and copulation in a minimum of 25 d. Field experiments on the seabed off Lowestoft in June 1987 with a sea temperature of about 16 °C suggested that the developmental period in those conditions could be as short as 11 d. Previously uninfected flounder in the field experiments became naturally infected with copepodids at a mean rate of not less than 30 parasites per fish d^–1.     

Factors affecting zooplankton feeding by the sea anemoneAiptasia pallida

Effects of various treatments on prey capture, prey ingestion and ingestion time of individualArtemia salina nauplii by the sea anemoneAiptasia pallida Verrill were studied in the laboratory. Exposure to crudeArtemia homogenate, 5 × 10^–4 M reduced glutathione or 5 × 10^–4 M proline significantly decreased the number ofArtemia that were captured and ingested but had no significant effect on the ingestion time of individualArtemia. Multiple captures increased the total ingestion time but decreased ingestion time per prey item. Results suggest that, under these conditions, the prey capture phase of zooplankton feeding was somewhat distinct from the ingestion phase since chemical stimuli that significantly reduced prey capture had no significant effect on ingestion time.     

The life cycle ofRhipicephalus lunulatus Neumann, 1907 (Acarina:Ixodidae) under laboratory conditions,with notes on its ecology in Zimbabwe

The durations of the developmental periods ofRhipicephalus lunulatus at 25°C and 87% RH were: preoviposition, 2–9 days; oviposition, 29–34 days; minimum incubation, 11–27 days; nymphal premoult period, 11–23 days; and adult premoult period, 19–30 days. The durations of the feeding periods on a rabbit were: 3–7 days for larvae and 4–11 days for nymphs. Adult feeding was completed on a rabbit and a sheep in 10–22 days in January and 14–64 days in September, and only fertilized females completed engorgement. The mean number of eggs laid by engorged females was 4732, with 95% being laid within the first 16 days. In the southeastern lowveld of Zimbabwe adult ticks were most abundant on cattle between November and December, and their preferred sites of attachment were the legs and tail. Other hosts of adultR. lunulatus were impala (Aepyceros melampus), warthog (Phacochoerus aethiopicus), kudu (Tragelaphus strepsiceros) and eland (Taurotragus oryx).     

The role of phototrophic sulfur bacteria as food for meiobenthic harpacticoid copepods inhabiting eutrophic coastal lagoons

Laboratory experiments were undertaken using Amonardia normani and Schizopera cf. compacta, two meiobenthic harpacticoid copepods commonly found in coastal lagoons. The first experiments were designed to determine if the phototrophic sulfur bacteria Chromatium gracile can be ingested by these copepods and at what concentrations. Egestion rate was used as an index of feeding rate. The response of the egestion rate, expressed in numbers of faecal pellets produced by copepod per day, as a function of bacterial concentration followed the functional model. A. normani attained constant feeding rates from the bacterial concentration of 1 × 10⁷ cells ml^–1 (5 µg C ml^–1) onwards, S. cf. compacta attained constant feeding rates from 2.6 × 10⁷ cells ml^–1 (13 µg C ml^–1) onwards. The faecal pellet volume changed significantly (p<0.05) between food concentrations for A. normani but not for S. cf. compacta (p>0.05). In order to investigate the effect of the phototrophic bacterial diet on the population dynamics of A. normani three groups of nauplii were maintained at 2 × 10⁷ cells ml^–1 and observed every day. The mortality of these nauplii was very high compared to those maintained on a diatom diet (Nitzschia constricta); only in one of the groups did some copepodites develop but no adults were ever observed. Adults fed on bacteria did not have different (p>0.05) survival rates compared to those fed on diatoms, nevertheless, the number of nauplii produced was significantly less (p<0.05) on the bacterial diet. These results lead us to suggest that although the phototrophic sulfur bacteria (Chromatium gracile) can be ingested by both copepod species it cannot sustain the full development of the A. normani population. Thus, a bloom of phototrophic sulfur bacteria does not seem to be a favourable situation for opportunistic benthic copepods to colonize eutrophic coastal lagoons after a dystrophic crisis.     

Reproduction of the calanoid copepod Calanus propinquus in the southern Weddell Sea,Antarctica: observations in laboratory

Reproduction of the dominant Antarctic copepod Calanus propinquus was studied in February–April, 1989 aboard the R.V Dmitry Mendeleev during cruise N° 43 to the Weddell Sea. Single females were kept at 0 °C in the laboratory for 56 days with abundant food concentration (above 300 µg C l^–1 of Platymonas viridis). Females released clutches at night at 2–3 day intervals. Most clutches contained from 10 to 40 eggs, mean 37.3 eggs female^–1. Average carbon content of an egg was 0.37 ± 0.05 µg C. The maximum daily egg production rate of 30–50 eggs female^–1 d^–1 was observed for the first 3 days of the laboratory incubation, corresponding to 3.7–6.2% body C. The state of gonadal development of females showed the decline of the reproductive season in late February. The data suggest that egg laying in the region under study starts in December and lasts until March. The state of ovarian maturation, changes in vertical distribution and biochemical body composition of females suggest the possibility of two-year life cycle in C. propinquus in the southern Weddell Sea.     

The ecology and production of copepods, particularly Thermocyclops hyalinus, in the tropical Lake George, Uganda

(1) Total copepod numbers per litre in Lake George, Uganda, vary slightly during the course of a year. Numbers increase during the dry seasons June-August and January-February, and decrease during the rains. This variation is more marked in the mid-lake area, where copepod numbers are higher, but the change in numbers is not more than two-fold. By comparison with populations in temperate regions the population in Lake George is stable in size and shows little seasonal variation. (2) The carnivorous cyclopoid Mesocyclops leuckarti forms only 4–21 %, by num-bers, of the total copepod population and does not occur in numbers large enough to be analysed profitably. (3) The bulk of the population is the much smaller Thermoeyclops hyalinus and analysis of this population into the main development stages of its life history shows an almost constant age structure over the lake as a whole, throughout the year. (4) The development time of the eggs, as determined previously (Burgis, 1970), is 1–5 days. This, plus mean development-times of 6 and 11 days for nauplii and copepodites respectively, has been used to determine the daily rate of recruitment from each stage of the life history to the next. The recruitment from nauplii to copepodites and from copepodites to adults are very similar and almost constant. Recruitment from eggs to nauplii is. however, mueh greater, and it thus appears that the major loss to the population is at this eariy stage in the life history. This may well be due to predation by the larvae of Chaohorus. (5) Using this recruitment rate from eggs to nauplii, the potential turnover time of population numbers was calculated to have a mean value of 4–2 days for the lake as a whole. This is similar to maximum summer turnover times found by authors such as Hall (1964) for Daphnia populations in temperate waters. (6) The biomass of individuals at various stages in their life history was deter-mined as carbon, and application of these determinations to the numerical counts was used to calculate the standing-crop biomass in the lake. With a constant population of stable age-structure it is possible to estimate the daily biomass production from the turnover time of numbers. For the population of Thermocyelops hyalinus in Lake George this gives a mean figure of 211 μg C/I/day during 1969–70. (7) Instantaneous birth rates and instantaneous rates of change in population numbers (b and r) have also been calculated for the population of Thermocyclops. The values of r show some variation at one centre site, fluctuating around zero, but when calculated for lake mean figures r is hardly different from zero throughout the year. The values of b also show fluctuations when calculated for one site but when calculated for lake mean figures show no more than two-fold variations, being higher at the beginning of the two rainy seasons. The values of b are not as high as those attained during the summer in some temperate Daplmia populations such as those described by Wright (1965). The values of ZJ tend to be higher inshore than in mid-lake areas of the lake. (8) The instantaneous mortality rate r/has been calculated from b-r. With such very small values of r, d is always very similar to b. Most, if not all, recruitment to the population is counterbalanced by loss, probably predation. (9) At one inshore site the population was analysed and counted in detailed cate-gories, over a period of 10 days. This allowed a more accurate estimation of the standing-crop biomass and thus of production. A mean value of 103 μg C/l/day was obtained for these samples. (10) The mean daily level of production, c. 211 μg C/l/day, o(Thermocyclops hyalinus in Lake George, is among the higher values of zooplankton production available for comparison most of which are from temperate regions of the world. The fact that it is applicable throughout the year gives an annual value of 77g C/m³/year which is probably high.     

Feeding and growth of larval herring,Clupea harengus,in relation to density of copepod nauplii

Synopsis Feeding and growth rates of 1–3 wk old herring larvae from four different stocks were compared in laboratory experiments (8°C). For most of the larval groups, feeding rate was saturated at nauplii (Acartia tonsa, nauplii stages 3–5) densities over 301^–1 (5 g d.w. 1^–1). Specific growth rate increased asymptotically with nauplii density, and reached about 6% d^–1 at densities over 120 nauplii 1^–1. The growth rates attained in the laboratory were similar to field measured growth rates of similarly aged herring larvae at comparable food densities. Since food particles were homogenously distributed in the laboratory tanks, patches of dense plankton concentrations are, thus, apparently not necessary for larval growth and survival in the sea. Growth efficiency differed between larval groups, with large sized larvae being the most efficient in transforming ingested matter into growth. The difference probably relates to different sizes rather than to the different geographical origins of the larvae.     

Sporulation ofEnteromorpha spp. (Chlorophyta) and overwintering of spores in sediments of the Wadden Sea,Island Sylt,North Sea

For the last two decades dense mats of species of the filamentous green algaeEnteromorpha spp. have regulary occurred on tidal flats of Köningshafen Bay (island Sylt, North Sea, FRG). In calm areas overwintering of adult plants or plant fragments is a common process to guarantee the mass development during the next season. In contrast, the distribution ofEnteromorpha on exposed sandy tidal flats depends on recruitment by juvenile stages. In 1993Enteromorpha spore settlement was recorded regularly in the field. Polyethylene dishes were placed in the field and left for a period of seven days and lateron cultivated in the laboratory to checkEnteromorpha germling development. During summer 1993 — at a minimum distance of 200 m to the nearest adultEnteromorpha populations — a total of at least 82×10⁶ spores m^–2 settled. During winter the number of spores attached to the collecting dishes was close to zero and the adjacent sand flats were free of any visibleEnteromorpha plants. In further experiments it was shown that the development ofEnteromorpha juveniles in the next spring depended on the overwintering capacity of spores. More than 2×10⁶ spores m^–2 attached to large sand grains and other substrata (e.g. Hydrobia ulvae) survived the winter. In a laboratory experiment several species ofEnteromorpha were able to survive in total darkness for at least 10 months.     

Observations on the incidence and seasonal fluctuations of certain crustacean larvae in the plankton of the South-West Coast of India

The seasonal fluctuations in the incidence of planktonic organisms and the larval forms of certain crustaceans such as crabs, barnacles and post larvae of prawns in the plankton of the south-west coast of India have been followed for a period of three years from 1963. South-west monsoon period is the least productive period for zooplankton in this area. Brachyuran zoeae, post larvae of prawns and barnacle nauplii occur in the plankton throughout the year with distinct peaks for different groups. The zoeae ofUca annulipes occur in the plankton from September to May with a peak during November–December. The zoeae ofPortunus pelagicus are present in the plankton from September to June and their abundance is in February–March. The post larvae ofMetapenaeus affinis are found in the inshore plankton from November to June with the peak in March. The nauplii ofBalanus amphitrite communis occur in the plankton in all the months of the year, the peak incidence has been during November January. The zoeae ofU. annulipes are found to tolerate better the medium saline conditions. Of the ecological factors, salinity of the ambient water and the availability of planktonic food for the larvae seem to influence the seasonal fluctuations of these crustacean larvae in this locality.     

Adaptive Responses of the Larvae of Cirripede Barnacle Peltogasterella gracilis to Changes in Seawater Temperature and Salinity

The responses of the larvae of the cirripede barnacle Peltogasterella gracilis (Crustacea: Cirripedia: Rhizocephala) that parasitizes the hermit crab Pagurus pectinatus to different combinations of seawater temperature (25, 22, 20, 16, and 12°C) and salinity (from 34 to 8) were studied in a laboratory. The nauplii of P. gracilis completed the entire cycle of development at 22 to 12°C in a narrow range of salinity (from 34 to 28), which agrees well with the environmental conditions of the crab hosts' habitat. At favorable temperatures (22–20°C) and salinity (34–28), the nauplii reached the cypris stage in 88 ± 2 h, while at 12°C and 34–30, the naupliar development took 156 ± 5 h. The cypris larvae appeared more resistant compared with the nauplii, in terms of changes in both the temperature and salinity of seawater. They actively swam at all experimental temperatures and in the salinity range of 34–18. At temperatures (22–16°C) and salinities (34–24) favorable for the cyprids, their longevity in plankton equaled 6–10 days. Thus, the nauplii of P. gracilis is the more vulnerable stage of development in the life cycle of this parasitic barnacle. The tolerance against changes in environmental factors is due to the adaptive capabilities of parasitic larvae and the environmental conditions in the habitats of its host, a typical marine crustacean. The insignificant parasitization rate of the hermit crab by its rhizocephalan parasite may be explained by the death of the nauplii of P. gracilis, which occurs when they enter to the surface water layer.     

Larval Mirogrex terraesanctae (Cyprinidae) of Lake Kinneret (Israel): growth rate,plankton selectivities,consumption rates and interaction with rotifers

The rotifer Synchaeta pectinata dominated gut content of first feeding Mirogrex larvae (7 mm, 10 days age) and was a selected prey of neuston-caught larvae up to 15 mm TL. A negative L-value (linear index of selection) applied to predation on nauplii and copepodites by 7 and 8 mm larvae; nevertheless, caloric intake was dominated by copepods in 8–10 mm larvae. Neuston-caught larvae 13–20 mm TL fed selectively on Cladocera, especially Bosmina, and on the rotifer Asplanchna spp.Growth, estimated from otolith ring counts and from analysis of size distribution data, ranged from 3 to 7 mm mo^–1, with higher rates for early spawned larvae. When consumption as estimated from gut content, was compared to amounts of food required for growth, it appeared that the smallest larvae were underfed, while 13–16 mm fish obtained rations close to sufficiency.Rotifer standing stock biomass in Lake Kinneret has decreased in recent years, especially in winter, the spawning period of Mirogrex. Postulated causes are predation by an increasingly large population of Mirogrex larvae, and decrease of external supply. Larval distribution appeared to be linked to S. pectinata abundance; highest densities of both organisms occurred in the area of inflow from the Jordan and Golan streams. Larval food enrichment of inflow water by fish pond drainage might have caused observed increases in Mirogrex stock size since 1960.     

Host and site selection by larval stages and adults of the parasitic copepod Lernaeenicus sprattae (Sowerby) (Copepoda,Pennellidae) in the Oslofjord

Sprat caught by beach seining during the period 1977–1980 were examined for adult Lernaeenicus, and both sprat and herring caught in 1981–1983 were examined for all parasitic stages. Lernaeenicus was never found on herring. Adult L. sprattae were always found in the sprat's eye, usually (89%) in the upper rear quadrant of the eye. Double and triple infection of one or both eyes were found. Infection experiments support results from field work. The sprat is the only intermediate and final host of L. sprattae. In laboratory experiments, copepodites showed no preference for particular size groups of sprat. The infective stages, copepodid and adolescent female, are both initially randomly distributed on the host before the copepodites move towards the fins and the gravid females to the eye.     

Evaluation of the meiobenthic copepod Bryocamptus zschokkei (Schmeil) as an ecologically-relevant test organism for lotic freshwaters

Despite proven utility as ecotoxicological testorganisms in marine systems, harpacticoidcopepods have not been used in freshwaterbiomonitoring. Here we assess the value ofBryocamptus zschokkei, a common member ofmeiofaunal stream communities, as a testorganism for lotic systems by measuring theeffects of copper on acute (survival ofovigerous females) and sub-lethal (offspringproduction, juvenile [i.e. naupliar andcopepodite] development times) end points. Allovigerous females survived exposure atconcentrations <180 µg Cu l^–1, butat >180 µg Cu l^–1, mortalityincreased with exposure times up to 72 h;seventy-two and ninety-six hour LC50s wereidentical (290 µg Cu l^–1). After sixtydays, total offspring production per femaledeclined with increasing copperconcentration; no offspring were producedat 150 µg Cu l^–1 and significantlyfewer offspring were produced at 100 µg Cul^–1 compared with the control. In thejuvenile development tests, nauplii andcopepodites did not survive at 150 µg Cul^–1, but there was no significant effecton development times at lower Cu concentrations(0–100 µg Cu l^–1). Comparison oflaboratory-derived, toxicity end points withdata for B. zschokkei populations incopper-contaminated streams in south-westEngland, demonstrated that significant declinesin the number of surviving offspring closelymatched concentrations of copper across whichdeclines in field populations occurred. Theseresults indicate that B. zschokkei haspotential as an ecologically-relevant testorganism for lotic systems.     

Compartment analysis of plant cells by means of turgor pressure relaxation: II. Experimental results onChara corallina

Summary The three-compartment model (paper I) described turgor pressure relaxations as a sum of two exponential functions. The predicted shape of the curves could be confirmed inChara corallina by improving the recording and processing of data. An evaluation on the basis of the three-compartment model provided values for the hydraulic conductivity of the plasmalemma ofLp _p=2×10^–5 to 4×10^–5 cm sec^–1 bar^–1 and ofLp _i=3×10^–5 to 1×10^–4 cm sec^–1 bar^–1 for the tonoplast (assuming the area to be 90% of the plasmalemma area). The mean proportion of the total volume occupied by the cytoplasm was calculated to be 9%. This value is consistent with the concept of a highly vacuolated cell. Other explanations for the biphasic relaxation curves are discussed.     

Demographic characteristics of the copepod <Emphasis Type="Italic">Acanthocyclops americanus</Emphasis> (Sars, 1863) (Copepoda: Cyclopoida) fed mixed algal (<Emphasis Type="Italic">Scenedesmus acutus</Emphasis>)-rotifer (<Emphasis Type="Italic">Brachionus havanaensis</Emphasis>) diet

The predatory copepod Acanthocyclops americanus is commonly found in shallow ponds and lakes in Mexico. We tested the survivorship and reproduction-related variables of this copepod, isolated from Lake Huetzalin (Xochimilco, Mexico City), on four mixed diets comprising two algal concentrations (0.8 × 10⁶ and 1.6 × 10⁶ cells ml⁻¹ of Scenedesmus acutus) and two rotifer densities (1 and 8 ind. ml⁻¹ of Brachionus havanaensis). Survivorship patterns of naupliar and adult stages of A. americanus were evaluated at 24 ± 1°C. The demography experiments were initiated with five females and five males (1:1 ratio, 5th copepodites) into each of the 16 test [= 4 diet combinations × 4 replicates (cohorts)] jars containing 50 ml medium and with one of the chosen algal-rotifer diets. Data on the survival of naupliar and copepodites (up to V) showed a high death rate (80%) in A. americanus by the time nauplii reached the adult stage. The duration of developmental time for nauplii and the copepodite V (C-V) was about 28 days by which time A. americanus became adults. Food combination had a significant effect on both survival and duration of the naupliar and C-V but not on the development time in C-I, C-II, C-III, and C-IV. Naupliar stages showed highest life expectancy at low food levels (rotifers or alga). Adult male and female copepods showed better survival under higher availability of rotifers in the medium, while higher algal density resulted in steep mortality during the first days. Average adult lifespan and life expectancy of A. americanus varied from 19 to 23 days, depending on the diet combination. Age-specific reproductive output (m _x ) of female A. americanus showed low reproduction (<10 offspring per female on any given day) when raised on low rotifer density, regardless of the algal concentration. On the other hand, enhanced offspring production (average of about 50 nauplii per female) was recorded when the rotifer density was higher (i.e., 8 ind. ml⁻¹). Gross and net reproductive rates varied from 48 to 438 and 27 to 318 offspring per female, respectively. In general, higher availability of rotifers in the medium resulted in higher (8–10 times as compared to those in low rotifer density) gross and net reproductive rates. There was no significant difference in the generation time (13–14 days) in relation to the diet combination. The rate of population increase (r) (range: 0.29–0.69 per day) increased with greater abundance of B. havanaensis in the medium. Thus, our study showed that inclusion of animal protein in the diet is necessary for high population growth rates of A. americanus.