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Investigates population growth of Asplanchna sieboldi using rotifers Brachionus calyciflorus and B. patulus as prey. Difference in prey type and food density; Influence of culture medium on growth; Comparison between preys.

Investigates the effect of the cyclopoid copepod Mesocyclops thermocyclopoides on the interactions between the predatory rotifer Asplanchna intermedia and its prey Brachionus calyciflorus and B. angularis. Density of zooplankton of all major taxa; Population density of predators; Extinction of rotifer prey species in nature.

Evaluates trophic interactions between rotifer Asplanchna priodonta and the plankton community of Lake Windsborn, Germany. Analysis of long-term population dynamics of the species in relation to hydrochemical and climatic varieties; Absence of any trophic interactions; Information on the diet of the rotifer; Dependency of trophic position of the rotifer on the structure of plankton community.

The pseudocoelomic body cavity of the rotifer Asplanchna spp. contains free cells that form a highly dynamic, three-dimensional polygonal network of filopodia. Using video-enhanced differential interference contrast microscopy, we have qualitatively and quantitatively characterized the motion types involved with network motility: (1) filopodial junctions are displaced laterally at 10.52±0.46 µm/s; (2) free-ending filopodia form and extend at rates of 8.77±0.40 µm/s, until they retract again at 7.23±0.87 µm/s; (3) filopodial strands fuse either laterally or tip to the lateral side. The combination of these motion types results in enlargements, diminutions, and extinctions of filopodial polygons, and in the formation of new polygons. Moreover, there is intense and fast (5.11±0.28 µm/s) particle transport within the filopodial strands. The organization of the cytoskeleton in filopodia was examined by electron microscopy and by labeling with fluorescent-tagged phalloidin. Filopodia contain several microtubules that are often organized in a bundle. Moreover, F-actin is present within the filopodia. To characterize which of these cytoskeletal systems is involved with cell and organelle motility, we have examined cell dynamics after incubations with colchicine or cytochalasin D. The results of these pharmacological experiments provide evidence that microtubules are required for both cell and organelle motility, but that actin filaments contribute to these phenomena and are required for the structural maintenance of slender filopodia. [ABSTRACT FROM AUTHOR]

Summary1. Interactions were observed between three morphotypes of the predatory rotifer Asplanchna silvestrii and six different prey (Brachionus plicatilis, B. rotundiformis, B. pterodinoides, B. satanicus, Hexarthra jenkinae and copepod nauplii) to understand the differences in feeding abilities among morphotypes that may have led to the evolution of this predator polymorphism. The outcome of predation events was affected significantly, both by predator morphotype and prey type. Predator morphotypes also interacted differently with different prey types. 2. The two smaller morphotypes, the saccate and the cruciform, responded similarly to prey overall, except that the smallest morphotype (saccate) was unable to ingest the most mobile prey (nauplii) and less able to ingest relatively large prey (B. plicatilis). The largest morphotype, the campanulate, had the highest encounter rate with prey, but the lowest probability of attack after encounter, so that it consumed far fewer prey per feeding bout than did the smaller morphotypes. This may have been because campanulates prefer larger prey than used in this study. 3. Highly mobile prey (H. jenkinae and copepod nauplii) were much less susceptible to predation than the less mobile Brachionus species. While evasiveness reduced attacks by saccates and cruciforms, campanulates did not have a significantly lower attack rate on H. jenkinae and copepod nauplii than on less evasive prey. Large body size moderately defended B. plicatilis against ingestion by saccates only. The short-spined B. satanicus was the only prey that was rejected after capture, resulting in lower ingestion probabilities for B. satanicus than other brachionid prey. [ABSTRACT FROM AUTHOR]

Provides information on a study of the different behavioral responses in giant rotifer Asplanchna sieboldi. Methodology and materials used to conduct the study; Results of the study; Information on the preparation of asplanchna sieboldi for scanning electron microscopy; Discussion on the results.

1. Diet composition and the production of embryos were measured in Asplanchna girodi and Asplanchna priodonta collected through 3 years in the San Joaquin-Sacramento delta of California. The two species are sympatric in low to moderate densities for 5 months of the year. 2. Despite marked differences in the structure of the trophi, both species consumed the same array of prey species. Percentage composition of the diet varied both intra- and interspecifically. The food niches of the two species appear to differ little from one another. 3. Individuals of Asplanchna girodi had a larger mean number of prey in the gut per individual than did those of A. priodonta, due to their larger size. Per unit volume, each species prey gathering performance was the same. Asplanchna priodonta produced more embryos per calculated unit volume of prey ingested than did A. girodi. 4. During spring, when both species were present in the plankton, A. priodonta did not capture Size Class 2 and 5 animals (volumes 0.09–1.0 μm3 × 106 and 3.0–3.5 μm3×106 respectively) nor large Synchaeta. Both these prey classes were in the diet during the summer and autumn months. Several hypotheses are examined as possible explanations for this phenomenon. [ABSTRACT FROM AUTHOR]

The effects of dietary co-tocopherol on the growth, the phenotype, and the reproduction of the rotifer Asplanchna sieboldi are reviewed. New data show that postmitotic, newborn rotifers of this species cultured with emulsified 5 × 10-7 M d-α-tocopherol attain significantly larger adult body sizes than control rotifers cultured without this compound. The cytoplasmic enlargement in this large syncytial organism cannot be induced by either 2, 5, 7, 8-tetramethyl-2-(4',8'-dimethylnonyl)-6-hydroxychromane or ethoxyquin. A specific, tocopherol- stimulated growth response apparently has not been reported in other systems. Data on the effect of co-tocopherol on the growth of another rotifer, Brachionus calyciflorus, are given. [ABSTRACT FROM AUTHOR]

This article focuses on the Asplanchna and the spines of Brachionus calyciflorus in two Javanese sewage ponds. A substance liberated by Asplanchna causes females of Brachionus calyciflorus to produce offspring with postero-lateral spines. In plankton samples from two sewage ponds near Bandung in Java the postero-lateral spines of B. calyciflorus were extraordinarily long. The Javanese sewage ponds are extremely rich in zooplankton, and the density of Asplanchna is very high. The relationship between postero-lateral spine length and Asplanchna density is also confirmed by a comparison of the two ponds.

We have determined the changes in fecundity, mortality, and growth of the ploimate rotifer, Asplanchna girodi, in response to variations in food density. Rotifers were raised from birth on either fixed allotments of Paramecium tetraurelia or on allotments that varied temporally. Fecundity, growth rates, and size of the rotifer at the time of birth of the first offspring varied directly with food level. Longevity and age at the birth of the first young varied inversely with food level. The size of offspring remained constant regardless of parental food intake. Individuals switched from low to high food rations produced more offspring than those given a high ration from birth. The per capita death rate was insensitive to food level, but the birth rate varied directly with food level. Young individuals were better able to resist starvation than adults. These responses of A. girodi to varying resource densities are interpreted as being adaptive in environments with temporally varying food resources. When food levels are high, many young are produced and act to buffer the population against a decline in numbers when the food levels are reduced. The restoration of higher food levels causes the starved individuals to respond with high fecundities, which act to restore population densities to previous levels. In all resource environments, individual fecundity is adjusted to produce young with high changes of survival and reproduction. [ABSTRACT FROM AUTHOR]

When the diet of A. sieboldi contains tocopherol and certain types of prey, such as congeners, females develop into one of two morphotypes-cruciform or campanulate. The frequency with which these morphotypes can be produced in a population is a function of: probabilities that the daughters of amictic (asexual) cruciforms and campanulates will be cruciform and campanulate; the probabilities that cruciforms and campanulates will be amictic and mictic; and the birth rates of amictic cruciforms and campanulates. These reproductive parameters wee determined from laboratory observations on individuals from populations maintained on a diet of A. brightwelli with d-α-tocopherol at 10-7 mol/L. A Markovian model was developed and, when used with these data and initiated with a single amictic cruciform, showed that an equilibrium distribution of 34.8% amictic cruciforms, 51.0% mictic cruciforms, 8.5% amictic campanulates, and 5.7% mictic campanulates was approached at a rapidly decelerating rate and finally attained after 15 generations. Varying the inputs to this model showed that very high equilibrium frequencies of campanulates could be produced if most campanulates were amictic and had predominantly campanulate daughters, even if almost all daughters of cruciform parents were cruciform, but could not be produced even by dramatically increasing either the probability of cruciforms bearing campanulate offspring or the reproductive rate of amictic campanulates relative to that of amictic cruciforms. The high proportions of campanulates often observed in natural populations could not be produced if the reproductive parameters of the amictic cruciforms and campanulates were similar to those determined in this study, unless the cruciforms were preferentially eliminated through cannibalism or predation. Shifts in the frequency distributions of cruciforms and campanulates, such as have been noted in natural populations, could be due to: progressions to equilibrium distributions; variations in the types of prey available; changes in environmental factors that differentially affect the redproductive parameters of the two amictic morphotypes; different intensities of selective, intermorphotypic cannibalism; successions of invertebrate and vertebrate predators that differentially ingest the two morphotypes; and clonal replacements that alter characteristics of the two morphotypes affecting reproduction and survival. [ABSTRACT FROM AUTHOR]

Laboratory experiments showed that A. bright-welli could outreproduce, or coexist with, A. silvestrii only when the absence of dietary tocopherol prevented the latter from transforming to the giant cruciform and campanulate morphs. When tocopherol permitted polymorphic transformations, as often occurs in nature, the giant morphs of A. silvestrii ingested and rapidly excluded the much smaller, only slightly polymorphic A. brightwelli. Such interference (or encounter) competition from trimorphic Asplanchna species is known to occur in nature and must limit the distribution and abundance of monomorphic or only slightly polymorphic species. The ability to eat congeneric competitors may have provided some selective pressure for the evolution of gigantism in the genus. [ABSTRACT FROM AUTHOR]

The article discusses the effect of methyl parathion-treated prey on the population growth of the predator asplanchna sieboldi. According to the author, the use of pesticides in combating pests in agriculture has increased tremendously in the last two decades in Mexico. Methyl parathion became one of the most used chemicals for controlling insect pests in agricultural and domestic environments. A substantial portion of these pesticides applied in agricultural fields was found to have reached the freshwater bodies in the area including rivers, ponds and lakes as run-offs.

The aim of the present study was to survey the rotifer composition of the Três Lagoas Lake Complex in the city of João Pessoa, state of Paraíba, Brazil. These urban lakes receive waste from the surrounding neighborhoods. Samples were carried out every two months between August 2008 and August 2009. The rotifers were identified using an optical microscope and specialized literature. Seventeen species were found, distributed among eight families and ten genera. Brachionidae was the most representative family. There were four new records for the state of Paraíba - Asplanchna priodonta (Gosse, 1850), Asplanchna sp., Rotaria rotatoria (Pallas, 1766) and Squatinella sp. [ABSTRACT FROM AUTHOR]

A correction to the article "Spine development in two taxa of Brachionus calyciflorus from Lake Littra, Australia: constitutive and induced defenses against Asplanchna," published in the December 8, 2016 issue of the journal is presented.

The rotifer Asplanchna sieboldi performs several well-defined behavioural responses to external stimuli. Contact of male and female occasionally elicits a mating response in the male. The mating response is composed of a series of distinct behavioural elements. After the initial contact, the male stretches out its body wall outgrowths, arcs into a characteristic mating posture and glides along the surface of the female until the penis becomes attached to the female’s body wall, through which the spermatozoa are injected. Under experimental conditions, the mating response could be evoked by stimulation with agar spheres that were impregnated with extracts prepared from females, while agar spheres prepared from buffer only did not cause any mating response. If the active substance was added directly to the suspending medium in the observation chamber, mating could be triggered just by mechanical stimulation. It is concluded that the mating response is triggered by a combination of chemical and mechanical stimuli. During the time course of the experiment there was no adaptation to the chemical stimulus. The receptor cells involved in the perception of the two stimuli remain to be identified. The mating response suppressed other behavioural responses that are usually triggered by tactile stimulation of the apical mechanosensors, suggesting that signal processing by the nervous system occurs. [ABSTRACT FROM AUTHOR]

1. We examined the effect of different periods of prior starvation(from 30 min to 16 h) on the prey capture behaviour, and functional and numerical responses of the predatory rotifer Asplanchna sieboldi using the rotifer Brachionus calyciflorus as prey. 2. Feeding activity (i.e. encounter, attack, capture and ingestion) by Asplanchna increased significantly with increasing prey densities from 2 to 16 mL--1 and with increasing prior starvation periods from 0.5 to 8 h. 3. Asplanchna sieboldi showed a type II functional response at all the prior starvation periods tested. The asymptotic prey density was highest after 8 h of starvation. 4. The instantaneous population growth rate of A. sieboldi ranged from 0.089 ± 0.044 (when starved for 8 h in every 24 h and at a prey density of 2 individuals mL--1 for the other 16 h) to 1.015 ± 0.142 in the control (no starvation and at a prey density of 16 individuals mL--1). The effect of starvation time on the numerical response was evident only at the higher prey density. [ABSTRACT FROM AUTHOR]