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While separated by large expanses of dry terrain unsuitable for aquatic biota, aridland waters possess high biodiversity. How aquatic micrometazoans disperse to, and colonize, these isolated ephemeral habitats are not well understood. We used a multi‐faceted approach including wind tunnel and rehydration experiments, and next‐generation sequencing to assess potential movement of diapausing propagules of aquatic invertebrates by anemochory across regional scales (102–105 km). Wind tunnel experiments using dry playa sediments with added micrometazoan propagules demonstrated that after entrainment by saltation and downwind transport, propagules could be subsequently rehydrated and were viable. Further, rehydration of fallen natural dust yielded micrometazoans, including rotifers, gastrotrichs, microcrustaceans, and nematodes. Using conserved DNA primers, we identified > 3300 eukaryotic Operational Taxonomic Units (excluding fungi) in the dust including some taxa found in rehydration experiments. Thus, we provide strong evidence that anemochory can disperse micrometazoans among isolated, ephemeral ecosystems in North American deserts and likely elsewhere.

Members of the sessile rotifer species Cupelopagis vorax are unusual ambush predators that live permanently attached to submerged freshwater plants. Previous light microscopical research has revealed several uncommon features in this species including a stellate‐patterned integument and an expansive foregut region called the proventriculus. In this study, we apply transmission electron microscopy to explore the ultrastructure of both the integument and foregut to determine how they differ from other rotifers. Our results reveal that the integument is covered by a thick glycocalyx and is patterned with tubercles that originate from the intracytoplasmic lamina (ICL) within the syncytial epidermis. The ICL forms an apical layer within the syncytium, is electron dense and mostly amorphous, and forms tubercles up to 2.3 μm; these tubercles probably account for the patterned appearance of the integument and are similar to what has been found in other gnesiotrochan rotifers. The basal cytoplasm is highly granular and contains two types of membrane‐bound vesicles: large ovoid vesicles (320–411 nm) with amorphous, opaque contents, and secretory bulbs (110–264 nm) with electron‐lucent cores and occasionally electron‐dense contents. Only the secretory bulbs were observed to form connections to the apical plasmalemma, and so are probably exocytotic. Internally, the proventriculus is a large distensible sack that connects the anterior pharyngeal tube to the posterior mastax. The proventricular epithelium is a thin syncytium mostly covered with a dense glycocalyx and a strong brush border of microvilli underlain by a thin terminal web. The cytoplasm contains few organelles and there is no evidence that it is either secretory or has features (e.g., ICL) that might aid in maceration. We hypothesize that the thick glycocalyx might serve a protective function against the movements of live prey and/or against enzymes released from the rotifer's gastric glands that become regurgitated during feeding.

While ubiquitous, temporary waters vary greatly in geographic distribution, origin, size, connectivity, hydroperiod, and biological composition. However, all terminate as active habitats, transitioning into either dryness or ice, only to be restored when conditions improve. Hydroperiod in some temporary habitats is cyclical and predictable, while in others it is sporadic. Although the rotifer communities of temporary waters are subjected to unique selective pressures within their habitats, species share many of the same adaptive responses. Here, we review temporary waters and their rotiferan inhabitants, examining community composition, life history, and evolutionary strategies that allow rotifers to flourish in these fluctuating environments.

The freshwater littoral comprises a mosaic of habitats structured at several scales by a combination of hydrophyte architecture and physiology. Within this complex environment littoral invertebrates should distribute themselves to maximize fitness: that is, for sessile animals selection of permanent substrata is critical, while distribution of motile (periphytic) animals should follow predictions of Ideal Free Distribution theory. Here we explore the relationships between littoral rotifers and hydrophytes by conducting nestedness analyses on 10 published datasets (7 sessile; 3 periphytic); one dataset each of microcrustaceans and insects were included for comparison. We used four metrics to assess nestedness: mean matrix temperature (T); counts of discrepancy shifts and species segregation; and percent singletons. Six sessile rotifer datasets exhibited nestedness (T = 9.25–30.2°, supported by ≥2 null models; the other metrics varied widely). Our results indicate that distribution of sessile rotifers and periphytic insects was highly structured, but until more data is available little can be said about the distribution of the periphytic rotifer or microcrustacean community structure. Sessile rotifer species possessing idiosyncratic temperatures (T>T +1.5 SD) exhibited a trend toward a record of cosmopolitanism. Important idiosyncratic hydrophytes included Ceratophyllum, Chara, and Utricularia. Two of the three periphytic, rotifer datasets exhibited nestedness (T = 19.2°, 39.9°), but each was supported by only one of the four null models. The periphytic microcrustaceans did not show nestedness, while the insects did (T = 15.5°; supported by four null models). The three other metrics varied considerably among the periphytic datasets, showing no discernable pattern.

This paper reviews several neutral models as possible mechanisms for simulating and explaining so-called “hollow curve distributions.” The models include simple random assignment, MacArthur's broken stick, Preston's lognor-mal (but as simulated by Sugihara), Fisher's logseries, and Hubbell's unified neutral theory of biodiversity and biogeog-raphy. Each model is fitted to data describing the distribution of genera over families in the phylum Rotifera.

Colonies of the freshwater colonial rotifer Sinantherina socialis (Monogononta, Flosculariidae) have been shown to be unpalatable to a variety of small-mouthed, zooplanktivorous fishes. To test whether invertebrate predators ingest the rotifer S. socialis, we conducted two types of experiments: (1) Microcosm experiments—in separate experiments, four invertebrate predators (i.e., dragonfly nymphs, damselfly nymphs, notonectids, and Hydra) were offered prey either singly or in combination. Prey were comprised of S. socialis; Epiphanes senta, a solitary, free-swimming rotifer; and Daphnia magna, a microcrustacean. In each experiment, the percent of prey surviving after 12, 18, and 24 h was recorded. (2) Paired-feeding experiments—in separate experiments, predators were offered prey in a pairwise fashion, in which members of D. magna were alternated with a rotifer, either S. socialis or E. senta. The results of the microcosm experiments showed that, after 24 h, 60–100% prey items of S. socialis survived the predators, but significantly fewer individuals of E. senta (6–89%) and D. magna (

Floscularia ringens is a cosmopolitan, sessile rotifer (class Monogononta) that lives inside a tube it constructs from numerous small, rounded pellets. Adults of F. ringens produce parthenogenetic eggs that are retained within the tube. Upon hatching, juveniles remain within the maternal tube for a short time completing their development before swimming away. The free-swimming juvenile has a conical body, short foot, small corona, and mastax with trophi, but appears unable to feed. After a short time (

To resolve several taxonomic problems within the family Conochilidae (Rotifera, Monogononta, Flosculariacea), we initiated a comparative study of the morphology in this and related taxa using samples collected from widely separated geographical regions. As part of this study, we paid special attention to trophal morphology using scanning electron microscopy. We also constructed and analysed a data matrix comprising 19 morphological characters of 11 taxa using cladistic methods to uncover all most-parsimonious trees. The results indicate that Conochilidae share a body form with Flosculariidae, but they possess a trophal structure which clearly differentiates them from all other Flosculariacea; thus, the diagnosis of the family Conochilidae is amended to incorporate morphological characters of the trophi. The analysis of our data matrix yielded a single, most-parsimonious tree. From the topology of that tree and our scanning electron microscopy observations, we propose the following: (1) the status of Conochilidae as a separate suborder of Flosculariacea is rejected; (2) taxonomic separation of Conochilus and Conochiloides as subgenera of Conochilus is confirmed; and (3) Lacinularia causeyae Vidrine, Mclaughlin & Willis, 1985 is reallocated to a new genus within the family Conochilide, Conochilopsis gen. nov., as Conochilopsis causeyae (Vidrine et al.) comb. nov.

We examined the nature and adaptive significance of substrate selection by larvae of the sessile rotifer Collotheca gracilipes. In a small artificial pond the preferred substrate was the anatomical undersurfaces (abaxial) of Elodea canadensis leaves, although four other macrophytes were present (Ceratophyllum demersum, Lemna minor, Myriophyllum spicatum, and Nymphaea odorata). Density of adults on Elodea at times reached >6 individuals/mm2, with >98% attached to abaxial surfaces. However, larvae offered plants in pairwise combinations selected substrates in the following order: Lemna > Elodea > Myriophyllum > Nymphaea. No larval loyalty to parental substrate was exhibited. Larvae preferentially selected abaxial over adaxial surfaces of Elodea leaves (91% on abaxial) in continuous illumination experiments, but the larvae did not discriminate between the two surfaces in total darkness (48% on abaxial). In the absence of a plant substrate, cell debris from any one of four aquatic and two terrestrial plant species induced larval settlement on the bottom of plastic well-depressions. Activity could not be attributed to carbohydrate, lipid, nucleic acid, or protein moieties within these extracts. However, alpha-amylase induced rapid larval settlement in the depressions. In the presence of this calcium chelator, larvae did not distinguish between ad- and abaxial leaf surfaces to the same degree as without the enzyme. Phospholipase-C and EDTA induced similar effects. Larval preference for abaxial surfaces could be reduced slightly when pH was stabilized at < 7.0. Because living Elodea in neutral-to-alkaline water can remove Ca+2 from beneath its leaves and release it from adaxial surfaces while photosyn- thesizing, we hypothesized that larvae initiate substrate selection activities on any surface when they are in microhabitats having ambient Ca+2 concentrations below a threshold concentration. Short- term, in vitro growth experiments showed that rotifers attached to abaxial surfaces of Elodea leaves grew significantly taller and produced more eggs per female than those which had been induced to settle on adaxial surfaces.

Larvae of the sessile rotifer Ptygura beauchampi begin substrate selection activities when they chemotactually sense a stimulus associated with the glandular tfichomes which cover their preferred substrate, the trap door region of the largest, prey capturing organs of the carnivorous aquatic plant, Utricularia vulgaris. Four other co-occurring congeneric species (U. gibba, U. inflata minor, U. intermedia, and U. purpurea) and 2 smaller, morphologically distinct, trap types of U. vulgaris were not colonized. All of these Utricularia traps (except U. purpurea) have glandular trichomes which are nearly indistinguishable from one another. The stimulus appears to be chemical in nature, arising from the terminal head cells of trichomes as they develop. The chemical stimulus (an allelochemic agent) may be the utricularian prey-lure first proposed by Cohn in 1875. This symbiotic relationship should be termed commensal because rotifers colonize, but do not feed on the plant or its prey, and because the plant is apparently not affected by the colonization.