Demography of zooplankton (Anuraeopsis fissa, Brachionus rubens and Moina macrocopa) fed Chlorella vulgaris and Scenedesmus acutus cultured on different media
*Dirección para correspondencia
Abstract
Generally zooplankton growth is often limited by the quality of their algal diet. A cheaper common practice in aquaculture, is to culture algae with fertilizers; however, the demography of zooplankton when fed these algae has not yet been evaluated. We studied the population growth and life table demography of the rotifers Anuraeopsis fissa and Brachionus rubens, and the cladoceran Moina macrocopa. For this, the algae Scenedesmus acutus or Chlorella vulgaris were cultured on defined (Bold’s basal) medium or the commercial liquid fertilizer (Bayfolan). Experiments were conducted at one algal concentration 1.0x106cells/mL of C. vulgaris or its equivalent dry weight of 0.5x106cells/mL of S. acutus. The population dynamics were tested at 23±1ºC in 100mL transparent jars, each with 50mL of the test medium, with an initial density of 0.5indiv/mL, for a total of 48 test jars (3 zooplankton 2 algal species x 2 culture media x 4 replicates). For the life table experiments with M. macrocopa, we introduced 10 neonates (<24h old) into each test jar containing the specific algal type and concentration. For the rotifer experiments, we set 5mL tubes with one neonate each and 10 replicates for each algal species and culture medium. We found that the average rotifer life span was not influenced by the diet, but for M. macrocopa fed S. acutus cultured in Bold’s medium, the average lifespan was significantly lower than with the other diets. The gross and net reproductive rates of A. fissa (ranging from 18-36 offspring per female) were significantly higher for C. vulgaris cultured in Bold medium. Regardless of the culture medium, Chlorella resulted in significantly higher gross and net reproductive rates for B. rubens than S. acutus diets. The reproductive rates of M. macrocopa were significantly higher in all the tested diets except when fed with S. acutus in Bold medium. The population increase rate, derived from growth experiments of A. fissa and B. rubens, ranged from 0.1-0.25/d and were significantly higher on C. vulgaris cultured in liquid fertilizer as compared to the other diets. The growth rates of M. macrocopa ranged from 0.1 to 0.38/d, and were highest with diets of C. vulgaris cultured in Bold medium and S. acutus cultured in fertilizer. Thus, regardless of the culture medium used, the growth rates of the evaluated zooplankton species were higher with Chlorella than with Scenedesmus. The peak population density was highest (2 800ind/mL) for A. fissa fed Chlorella that was cultured on liquid fertilizers, while B. rubens and M. macrocopa had peak abundances of 480 and 12ind/mL, respectively under similar conditions. Rev. Biol. Trop. 60 (3): 955-965. Epub 2012 September 01.
Key words: Rotifera, Cladocera, algae, fertilizer, diet, population growth, zooplancton.
Resumen
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Generalmente el crecimiento del zooplancton está a menudo limitado por la calidad de su dieta de algas. La demografía del zooplancton durante la alimentación con algas no ha sido estudiada, a pesar de que el cultivo de algas con fertilizantes es una práctica económica común en acuacultura. Se analizó la demografía de Anuraeopsis fissa y Brachionus rubens ]]> Moina macrocopa (cladóceros), alimentados con las algas verdes Scenedesmus acutus o Chlorella vulgaris cultivadas en medio Bold o fertilizante líquido comercial (Bayfolan, de Bayer). En los rotíferos no se observaron diferencias significativas en el promedio de vida, sin embargo, este parámetro en M. macrocopa con S. acutus cultivada en ]]> A. fissa fueron significativamente mayores con C. vulgaris cultivada en medio Bold, que con el fertilizante; estas tasas en B. rubens, independientemente del medio de cultivo, resultaron significativamente mayores con Chlorella que S. acutus. La tasa de reproducción de M. macrocopa fue significativamente mayor en todas, a excepción de S. acutus en Bold. En el crecimiento poblacional con A. fissa y B. rubens la tasa de crecimiento poblacional varió de 0.1 hasta 0.25/d, significativamente mayores en C. ]]> cultivadas con fertilizante, en comparación con las otras dietas; en M. macrocopa la tasa de crecimiento varió desde 0.1 hasta 0.38/d, las más altas fueron: con C. vulgaris cultivadas en medio Bold y S. acutus cultivadas con fertilizante. Así, en todas las especies, la tasa de ]]> Chlorella que con Scenedesmus.
Palabras clave: Rotífera, Cladócera, crecimiento poblacional, algas, dietas, fertilizantes.
]]> The production of adequate amounts of live food such as zooplankton for fish larvae remains a ‘bottleneck’ in aquaculture. Many reviews had well documented that the zooplankton requirement declines after the first 4-6 weeks, but during this period, demand is very high (50 000 rotifers per week per larva: Lubzens et al. 1989). This way, aquaculture facilities have to establish economical but large scale cultures of freshwater zooplankton.
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The live food predominantly used in freshwater aquaculture includes rotifers and cladocerans, this is because of their adequate body size for the gape of young larvae, high growth rates and ease of maintenance. The gape size of oviparous fish can be 10-25% of the total length (Østergaard et al. 2005) resulting in the need of small sized but nutritive prey. Rotifers are among the best suited prey during these early stages due to their small ]]>
Brachionids, particularly Brachionus calyciflorus, B. rubens and B. plicatilis (in marine systems) are most frequently used as live prey for fish. Anuraeopsis fissa is the smallest brachionid with high growth rates (Sarma et al. 1996) and therefore could serve as an important first diet for small fish species of the genus Chirostoma (although these measure only 20-30cm as adults, they have a high commercial value in Mexico (Chacón-Torres & Rosas-Monge 1995). Brachionus rubens is also useful due to its high growth rates (Azuara-García et al. 2006) and wide distribution under tropical conditions. Among cladocerans, Daphnia spp. are widely used in temperate countries but in the tropics M. macrocopa should be preferred, particularly due to its wide distribution, high maximal densities and growth rates (Sarma et al. 2005) and the high preference that fish larvae have for it (Zaret ]]>
The stoichiometric ratio of zooplankton is of paramount importance for using live food in aquaculture. Rotifers contain, as dry weight, 28-63% proteins and 9-28% lipids (Lubzens & Zmora 2003). Cladocerans, particularly Moina contain 59-78% proteins and 12-27% lipids (Watanabe et al. 1983). ]]> et al. 1995). These factors affect the population growth of zooplankton as well as the fish larvae. The quality of zooplankton as diet for fish larvae can be tested using proximal analyses as well as growth bioassays. Previous studies have indicated that the growth rates of rotifers are significantly influenced by the quality of the diet. Growth rates are lower on yeast than on algae-yeast mixed diets ]]> et al. 2005). These effects are also evident at the next trophic level. For instance, B. rubens cultured on the organic wastes had higher growth rate than Chlorella-fed populations; the nutritional quality of the rotifers cultured on this diet was further reflect in bioassays conducted with the predatory rotifer Asplanchna sieboldi, which had growth rates ranging from 0.05 to 0.08 per ]]> B. rubens cultured on C. vulgaris but 0.14 to 0.22 per day on rotifers fed organic wastes (Sarma et al. 2003). In an earlier study, Kibria et al. (1999) showed that the somatic growth of the perch (Perca fluviatilis) was higher on Daphnia carinata cultured in waste water ]]> Moina australiensis reared on the same medium.
Green algae grow well on commercial fertilizers (Chaumont 1993). Our preliminary experiments have shown that the liquid fertilizer of Bayfolan (Bayer product) supports algal growth comparable to the defined algal media such as Bold’s basal. This is important in terms of aquacultural requirements since culturing ]]> Scenedesmus and Chlorella (Flores-Burgos et al. 2003) can be used for zooplankton culture. However, few laboratory studies considered growing algae on commercial liquid fertilizers because of possible nutritional limitations.
In this study, we ]]> A. fissa, B. rubens and M. macrocopa fed Chlorella vulgaris or S. acutus, grown on Bold´s basal medium or the commercial liquid fertilizer Bayfolan (Bayer).
Materials and methods
Culture assays: Anuraeopsis fissa (body length, 70μm) and M. macrocopa ]]> Brachionus rubens (120μm) from a small pond in Tepozotlan town, all in Mexico. All the zooplankton species were cultured in moderately hard water (EPA medium) and fed a mixture of S. acutus and C. vulgaris at 23 ± 2°C. The EPA medium was prepared by dissolving 96mg NaHCO3, 60mg CaSO4, 60mg MgSO4 and 4mg KCl ]]>
Life table studies: All experiments were conducted at one algal concentration 1.0x106cells/mL of C. vulgaris or its equivalent dry weight of 0.5x106cells/mL of S. acutus (Mayeli et al. 2004). ]]> M. macrocopa, we introduced 10 neonates (<24h old) into each jar containing the specific algal type and concentration. For the two rotifer species, the experiments were conducted in 5mL tubes with one neonate each. For these experiments, we set up 10 replicates for each algal species and culture medium. The number of individuals in each cohort was counted daily. The neonates and dead individuals of the ]]>
Jack-knife method was used to derive means and standard errors of the demographic variables of rotifers (Meyer et al. 1986). ]]>
where, lx is the probability of an individual to survive to an age class, mx is the age specific fecundity, Ro is the average number of offspring per female, and r is the population growth rate.
Population growth experiments: Population growth experiments were conducted under similar conditions mentioned above, in 100mL recipients with 50mL of the test medium with the desired algal concentration.
Every jar included 25 individuals of a mixed population of each of the test species. In total there were 48 test jars (three zooplankton taxa x two algal species x two culture media x four replicates). The individuals were counted and transferred to fresh medium with the appropriate algae concentration in a daily basis. The experiments were continued over a three-week period, until the populations began to decline. Population growth rates were calculated using the formula:
]]> where No is the initial population density, Nt is the population density at time t and t is the time in days (Krebs 1985).
Data from demography ]]>
Results
]]> Demography: The survivorship curves of A. fissa showed a steady decline in the rate of survival with age, regardless of the diet (Fig. 1). The fecundity was highest on Chlorella cultured on Bold’s medium. B. rubens showed a steep decline in survivorship (Fig. 1) as compared to A. ]]> . The fecundity was also significantly higher with Chlorella as compared S. acutus. The survivorship and fecundity of M. macrocopa (Fig. 1) were higher with Chlorella cultured in Bold’s medium and Scenedesmus cultured in Bayfolan. These variables were much lower when fed Scenedesmus cultured on Bold’s medium.
For the rotifers, no significant impact of the tested diets was found on the average lifespan, which was eight days in the case of A. fissa and five days in that of B. rubens. The average lifespan of M. macrocopa was about 14 days for all the ]]> S. acutus cultured on Bold’s medium for which was significantly lower (F-test, p<0.05).
The gross and net reproductive rates of A. fissa ranged from 18-36 offspring per female and were significantly higher with C. vulgaris ]]> Fig. 2). Regardless of the culture medium, Chlorella resulted in significantly higher (F-test, p<0.05) gross and net reproductive rates for B. rubens when compared to S. acutus diets. The reproductive rates of M. macrocopa were significantly ]]> S. acutus on Bold’s medium. It varied from 30 to 85 offspring per female. The generation time ranged from 4 to 6 days for rotifers. In A. fissa it was significantly longer with C. vulgaris diet on Bold’s medium when compared to all other tested media. For B. rubens, it was not significantly influenced by the diet, while in M. macrocopa it was significantly lower only on S. acutus cultured in Bold’s medium. The population growth rate of A. fissa ranged from 0.55 to 0.60 with no significant differences due to diet type. For B. rubens it was significantly higher on Chlorella (0.75-0.85 per day) than on S. acutus (0.25-0.40 per day). The growth rate of M. macrocopa ranged between 0.2-0.40 per day and was significantly lower (F-test, p<0.05) for S. acutus cultured on Bold’s medium as compared to the other diets.
Population growth: The rotifer species A. fissa and B. rubens had higher growth rates ]]> C. vulgaris than on S. acutus (Fig. 3). Regardless of the culture medium S. acutus did not support higher reproductive output. On the other hand, C. vulgaris cultured on the fertilizer was a better diet due to significantly higher growth rates of both the rotifer species as compared to those observed on diets of C. vulgaris cultured on Bold´s medium. The cladoceran M. macrocopa also grew better on a diet of C. vulgaris than on S. acutus (Fig. 3). Growth rates were higher for C. vulgaris cultured in Bold’s medium than for S. acutus ]]>
The population growth rates of both, A. fissa and B. rubens, ranged from 0.1-0.25/d (Fig. 4). These were significantly higher on C. vulgaris cultured on fertilizer as ]]> M. macrocopa ranged from 0.1 to 0.38/d, and were highest on diets of C. vulgaris cultured on Bold’s medium and S. acutus cultured on the fertilizer. Thus, in all the three zooplankton species, regardless of the culture medium, the growth rates were highest on Chlorella than on Scenedesmus.
The peak population density reached was highest of 2 800indiv/mL in the smallest species tested, A. fissa. Brachionus rubens reached a density of 480indiv/mL while for M. macrocopa was of 12indiv/mL. The rotifer species attained the peak ]]> M. macrocopa reached peak densities between 15 to 18 days. There were no significant differences in the day at which peak densities were reached in relation to the diet.
Discussion
]]> Zooplankton bioassays are sensitive enough to test the quality of algal (Nandini et al. 2010) or seston (Gulati et al. 2001) diets. Our study also shows that all the three species used in this study showed significant differences in the life-history parameters with relation to, not only the differences between algal species but also the medium on which each alga was cultured. We found that, in general C. ]]> was a more suitable diet than S. acutus. In our study, the size of C. vulgaris ranged from 4.5-5.1μm while that of S. acutus from 8.8 to 8.9μm. Most zooplankton can easily filter algae in the size range of 5-25μm (Monakov 2003), therefore the algal size may not have been the reason for poor growth on S. acutus. This is most probably due to the fact that the cell wall ]]> et al. 1958) while that of Scenedesmus is 36 nm (Bisalputra & Weier 1963). This may have resulted in S. acutus being more difficult to digest by zooplankton than C. vulgaris.
The quality of algal ]]> et al. 1997). Although it has been suggested that in the face of poor food quality organisms would increase their intake (Brett 1993, Hessen 1993), this actually does not occur (Kilham et al. 1997). This is the reason why we found significant differences in the growth rates of the zooplankton in ]]> S. acutus cultured on Bold’s medium resulted in higher growth rates of M. macrocopa while Chlorella cultured on Bayfolan resulted in higher or similar growth rates of the rotifers as compared to same alga cultured on Bold’s medium. This clearly indicates that Bayfolan is adequate for plankton production for aquaculture practices and would help in bringing down the costs of algal production significantly.
That C. vulgaris cultured on the commercial fertilizer is adequate for the rotifers is also evident from the peak densities attained; for A. fissa this was more than five times that reached on C. vulgaris cultured on Bold’s medium. In the case of B. rubens significant ]]> et al. 1990).
Our study reiterates ]]> M. macrocopa as a live food for aquaculture. This species is known to have a higher protein content and lower ash content as compared to Artemia (Watanabe et al. 1983) or Daphnia (Kibria et al. 1999). It is one of the few cladoceran genera with much shorter age at first reproduction and lifespan which in turn result in higher growth rates. As compared to several cladoceran taxa, Moina frequently has growth rates values above 0.6 per day (Sarma et al. 2005). We also found that regardless of the algal type or culture medium used, the gross reproductive rate of Moina were up to 90. This indicates that a healthy, large scale, Moina culture would ensure sufficient prey for the fish larvae. Moina is also a preferred prey for commercially ]]> Chirostoma riojai showed high preference for M. macrocopa and consume it in large numbers (Morales-Ventura et al. 2004). It remains to be seen whether an exclusive diet of M. macrocopa, as compared to an artificial but balanced diet, improves the survivorship and growth of larval fish.
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Acknowledgments
JMV thanks Instituto Nacional de Pesca for permission and Posgrado de División de Ciencias Biológicas y de la Salud (UAM) for partial financial support. SN and SSSS thank PASPA and PAPIIT-IN221111 (UNAM) for financial ]]>
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*Correspondencia:
Jesús Morales-Ventura: Dirección General Adjunta de Investigación en Acuacultura, Instituto Nacional de Pesca, Ciudad de México, México/Posgrado División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana, México D.F. C.P. 04960. secciondf@yahoo.com.mx
S. Nandini: Laboratorio de Zoología Acuática, División de Investigación y Posgrado, Universidad Nacional Autónoma de México, Campus Iztacala, Tlalnepantla, Edo. de México, México, C.P. 54090. nandini@unam.mx.
S.S.S. Sarma: Laboratorio de Zoología Acuática, División de Investigación y Posgrado, Universidad Nacional Autónoma de México, Campus Iztacala, Tlalnepantla, Edo. de México, México, C.P. 54090. sarma@unam.mx. ]]> Maria Elena Castellanos-Páez: Posgrado División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana, México D.F. C.P. 04960. Laboratorio de Rotiferología y Biología Molecular de Plancton, División de Ciencias, Biológicas y de la Salud, Universidad Autónoma Metropolitana, Campus Xochimilco, Calzada del Hueso No. 1100, Villa Quietud, C.P. 04960, Ciudad de México, México; spaez@correo.xoc.uam.mx
1. Dirección General Adjunta de Investigación en Acuacultura, Instituto Nacional de Pesca, Ciudad de México, México; secciondf@yahoo.com.mx
2. Posgrado División de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana, México D.F. C.P. 04960.
3. Laboratorio de Zoología Acuática, División de Investigación y Posgrado, Universidad Nacional Autónoma de México, Campus Iztacala, Tlalnepantla, Edo. de México, México, C.P. 54090; nandini@unam.mx, sarma@unam.mx
4. Laboratorio de Rotiferología y Biología Molecular de Plancton, División de Ciencias, Biológicas y de la Salud, Universidad Autónoma Metropolitana, Campus Xochimilco, Calzada del Hueso No. 1100, Villa Quietud, C.P. 04960, Ciudad de México, México; spaez@correo.xoc.uam.mx
Received 18-VII-2011. Corrected 12-III-2012. Accepted 13-IV-2012.