The hard parts (trophi) of the rotifer mastax do contain chitin: evidence from studies on Brachionus plicatilis

The jaws (trophi) of the rotifer Brachionus plicatilis are soluble in strong acids but are resistant to long treatments by strong alkali. They show the same buoyant density as chitin and also as the chitin-containing layers of rotifer egg-shells. The presence of chitin in these structures was confirmed using the following techniques: chitosan-tests, thin-layer chromatography of trophi-hydrolysates which revealed glucosamine, by dissolving trophi with chitinase and electron microscopic WGA/gold-labelling. The content of chitin in the trophi was estimated by two different methods to be approx. 64% (50-75%).     

Combining confocal laser scanning and transmission electron microscopy for revealing the mastax musculature in Bryceella stylata (Milne, 1886) (Rotifera: Monogononta)

The rotiferan jaw apparatus (mastax) is characterized by enormous plasticity and according to morphology and feeding strategy, different mastax types can be distinguished. The cuticular hard parts (trophi) of the mastax are often highly specialized and have both a major taxonomic and phylogenetic relevance. Owing to numerous light and scanning electron microscopic studies, the morphology of the trophi is well known but only few attempts have been made to analyze the morphology and functionality of the mastax as a whole. Particularly, the complex muscular system connecting the individual trophi elements and moving them against each other was disregarded in the past. Therefore, the subject of the present study is a detailed analysis of the mastax musculature of the proalid rotifer Bryceella stylata using a combination of transmission electron and confocal laser scanning microscopic techniques, previously applied for revealing the somatic musculature in rotifers exclusively. Based on ultrathin serial sections and phalloidin-dyed specimens, a total number of six paired and two unpaired individual mastax muscles have been identified for the modified malleate trophi system of B. stylata. Possibly homologous muscles in other, so far investigated rotifer species are discussed as well as functional considerations of the individual mastax muscles and their interaction when moving the trophi elements are suggested.     

On the evolution and morphology of the rotiferan trophi, with a cladistic analysis of Rotifera

The phylogeny of Rotifera was examined in different computer‐generated cladistic analyses, including Seisonidea, Bdelloidea, Flosculariacea, Collothecacea and all ploimids treated on family level. The analyses were based on a character matrix solely dealing with morphological characters, primarily based on the trophi morphology. Limnognathia maerski (Micrognathozoa), Rastrognathia macrostoma and Gnathostomula paradoxa (Gnathostomulida) were used as outgroups. The cladistic analysis performed by paup produced 288 most parsimonious trees. peewee analyses produced between 140 and 432 trees, depending on the concavity value. The monophyly of Eurotatoria, Monogononta and Ploima was confirmed in all obtained trees. All analyses suggested a division of Ploima into major clades. One clade corresponded to Transversiramida while the other contained all other ploimid taxa and recognized Antrorsiramida as a monophylum. Based on the obtained results a scenario for the trophi evolution is proposed. The analyses suggested that the presence of an incus is synapomorphic for Gnathifera while mallei are synapomorphic for Micrognathozoa and Rotifera. The ancestral rotifer trophi probably resembled those in Harringia (Asplanchnidae).     

Combining confocal laser scanning and transmission electron microscopy for revealing the mastax musculature in Bryceella stylata (Milne, 1886) (Rotifera: Monogononta)

The rotiferan jaw apparatus (mastax) is characterized by enormous plasticity and according to morphology and feeding strategy, different mastax types can be distinguished. The cuticular hard parts (trophi) of the mastax are often highly specialized and have both a major taxonomic and phylogenetic relevance. Owing to numerous light and scanning electron microscopic studies, the morphology of the trophi is well known but only few attempts have been made to analyze the morphology and functionality of the mastax as a whole. Particularly, the complex muscular system connecting the individual trophi elements and moving them against each other was disregarded in the past. Therefore, the subject of the present study is a detailed analysis of the mastax musculature of the proalid rotifer Bryceella stylata using a combination of transmission electron and confocal laser scanning microscopic techniques, previously applied for revealing the somatic musculature in rotifers exclusively. Based on ultrathin serial sections and phalloidin-dyed specimens, a total number of six paired and two unpaired individual mastax muscles have been identified for the modified malleate trophi system of B. stylata. Possibly homologous muscles in other, so far investigated rotifer species are discussed as well as functional considerations of the individual mastax muscles and their interaction when moving the trophi elements are suggested.     

Two new species of the family Dicranophoridae (Rotifera, Ploima) from the littoral psammon, with notes on other brackish water rotifers in Denmark

The rotifer fauna has been investigated at three littoral brackish water localities in the Öresund, Denmark. Samples taken from plankton, periphyton and psammon yielded 14 rotifer species. Two of these are new to science and are described herein. Both species were found in psammon at the same locality. Erignatha longidentata n. sp. is characterised by having toes with swollen bases, convex outer margins and concave inner margins. The trophi have a pair of large subunci and relatively large unci. The other new species, Paradicranophorus wesenberglundi n. sp., is characterised by having two large red pigmented eyespots and large conical toes. The rami are lyrate, and intramallei and supramanubria are present in the mallei.     

Disentangling the morphological stasis in two rotifer species of the <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> species complex

The taxonomic uncertainty surrounding cryptic species complexes has traditionally been resolved using lengthy experimental approaches, while, since the advent of PCR based techniques the number of cryptic species described in a variety of taxa is increasing steadily. Here we formally describe a new rotifer species of the Brachionus plicatilis complex: Brachionus manjavacas n.sp., disentangling what was known as a morphological stasis. Detailed morphological analyses demonstrated significant differences in body shape and size between B. manjavacas and B. plicatilis s.s., analysed by geometric morphometrics; unfortunately these statistical differences are not taxonomically reliable because of wide overlaps. Size and asymmetry of masticatory apparatus, named trophi, observed by SEM, gave similar results, with taxonomic ambiguity. Only the shape of small pieces of the trophi, named satellites, were consistently different between the species. On a strictly classical taxonomical basis it is absolutely useful to name new species on morphological bases, as we did, and to assess their status as distinct entities. Nevertheless, the two species are broadly similar; therefore, we do not suggest using the small differences in shape of satellites of trophi to identify the species for further ecological studies, but to continue discriminating them on genetic marker bases. Handling editor: K. Martens     

The evolution of Synchaetidae (Rotifera: Monogononta) with a focus on Synchaeta: An integrative approach combining molecular and morphological data

This study represents the first phylogenetic reconstruction of Synchaetidae (Rotifera, Monogononta) and combines one morphological and two molecular data sets to derive the most comprehensive database for this taxon to date. Overall, 19 species were examined both morphologically (light- and scanning electron microscopy of habitus and trophi) and genetically (COI and 18S rRNA genes), thereby delivering new morphological information as well as the first molecular data for several species. Our results strongly support the monophyly of each of the three genera within Synchaetidae, with Synchaeta being the sister taxon of Polyarthra and Ploesoma. Resolution within each genus, however, was more poorly supported, possibly because of high levels of missing data for the more poorly known species that were also not re-discovered and revised in the present study. Nevertheless, an evolutionary reconstruction based on the total evidence topology indicates that the common ancestor of Synchaetidae was a rotatorivorous and pelagic freshwater rotifer exhibiting slightly enlarged lamellar trophi that were adapted to an enhanced pumping function. These features together with several, additional key character transformations (e.g., hatching independently from benthic or periphytic habitats) probably account for the success of Synchaetidae in pelagic environments and their being one of the most widely distributed and abundant rotifer taxa.     

Body musculature of Beauchampiella eudactylota (Gosse, 1886) (Rotifera: Euchlanidae) with additional new data on its trophi and overall morphology

This study presents the results of confocal laser scanning microscopy and fluorescence‐labelled phalloidin used to visualize the system of body musculature in Beauchampiella eudactylota. Moreover, the poorly known trophi of B. eudactylota are described based on scanning electron microscopy. In total, four paired longitudinal muscles (musculi longitudinales I–IV) and three circular muscles (musculi circulares I–III) were identified. Among these are the musculus longitudinalis ventralis, the musculus longitudinalis dorsalis and the musculus circumpedalis as documented in previous studies for other rotifer species. Compared to other species, B. eudactylota is characterized by the low number of lateral longitudinal muscles and the absence of some longitudinal muscles (musculi longitudinales capitum) and circular muscles (corona sphincter, musculus pars coronalis). Moreover, scanning electron microscopic data on the trophi of B. eudactylota reveal a number of striking similarities to the trophi in some species of Epiphanidae. This suggests that either (1) these similarities represent plesiomorphic characters present both in Epiphanidae and B. eudactylota or (2) they are synapomorphic features of B. eudactylota and some species of Epiphanidae, which would question the monophyly of Euchlanidae.     

A new rotifer from a coastal lake in Southeastern Brazil: Hexarthra longicornicula n. sp.

A new rotifer is described from among samples taken from coastal lakes in southeastern Brazil. Comparisons to related rotifers are made. This new animal belongs to the Hexarthra mira-intermedia species group by way of its general morphological configuration, the number of teeth in the trophi (5), and the two club-shaped caudal appendages (CSCA's). An extremely long dorsal antenna and very long setae extending from the bend in the ventro-lateral arm characterize this animal's speciation.     

<Emphasis Type="Italic">Rhinoglena kutikovae</Emphasis> n.sp. (Rotifera: Monogononta: Epiphanidae) from the Bunger Hills,East Antarctica: a probable relict species that survived Quaternary glaciations on the continent

A new species of rotifer, Rhinoglena kutikovae n.sp. (Monogononta: Epiphanidae), is described from a freshwater lake in the Bunger Hills, East Antarctica. The new taxon is characterized by the following combination of characters: body conical to vase-shaped; a single toe; distal foot pseudosegment bulged; tail prominent, semi-circular; two small spherical pedal glands with common duct, forming a complex with caudal ganglion; trophi with seven major teeth with offset head and two smaller teeth without offset head. The new species is compared with R. fertoeensis, R. frontalis and R. tokioensis, of which scanning electron microscopic information is presented of the trophi. R. kutikovae n.sp. is probably a relict species that survived Quaternary glaciations in glacial lacustrine refugia on the Antarctic continent.     

New records of rotifers from the South Island lakes,New Zealand

Thirty-five lakes in the South Island of New Zealand were surveyed for rotifers during 1988–1991. Of 85 taxa identified, 31 are first records for New Zealand, bringing the rotifers recorded from the country to 331. Four species (Keratella australis, K. slacki, Lecane herzigi and L. tasmaniensis), previously recorded as endemic forms only in Australia, are now added to the New Zealand checklist. Several of the new records are photographed, and scanning electron micrographs of the trophi are shown. Comments are made on the Australasian endemics and rotifer biogeography in New Zealand.     

A simplified method for preparing rotifer trophi for scanning electron microscopy

A simple, quick technique for the preparation of rotifer trophi for scanning electron microscopy is described. The method permits visual monitoring of the extraction process and does not require critical point drying of the specimens. Micrographs showing fine, structural detail of the hard parts of the mastax of representatives of the following genera are presented:Asplanchna, Conochilus, Filinia, Hexarthra, Keratella, Proalides, Synchaeta, andTrichocerca.     

On the structure and function of the mastax ofBrachionus plicatilis (Rotifera), a scanning electron microscope analysis

Sectioned specimens ofBrachionus plicatilis were examined by scanning electron microscopy (SEM). This technique was used to characterize the out-side appearance as well as the position and arrangement of the hard parts (trophi) in the interior of the mastax. Two strips of muscle stretch dorsally across the width of the mastax. Below these muscle strips, all the other components of the mastax form a continuous structure which is smoothly locked to the outside. Some nerve structures and glands of the mastax are found on the dorsal side, outside these muscle strips. By comparing the shape of parts of the trophi, exposed by sectioning, with the views of preparations of isolated trophi, it was possible to estimate how the trophi are positioned in relation to other components of the mastax and in relation to the animal as a whole. The results are used to complement and modify statements and conclusion from a previous study.     

A new marine rotifer of the genus Encentrum Its morphology and cultivation

Encentrum linnhei , a new marine rotifer from the west coast of Scotland is described. The structure of the trophi together with other characters clearly distinguish it from other species of the genus Encentrum . The work of Harring & Myers (1928) in clarifying the systematics of the Dicranophorinae greatly facilitated the "running down" of characters. A method of germ-free monoxenic culture of the rotifer is also described.     

Comparison of taxon-based and trophi-based response patterns of rotifer community to water quality: applicability of the rotifer functional group as an indicator of water quality

Rotifer community is often used as a taxon-based bioindicator for water quality. However, studies of the planktonic community from the viewpoint of functional groups in freshwater ecosystems have been limited, particularly for rotifers. Because rotifers have various trophi types determining their feeding strategies, thereby representing an ecological niche, their functional feeding groups can act as biological and ecological indicators in lakes and reservoirs where planktonic communities are dominant. We analyzed the patterns of spatial distribution of the rotifer community in various reservoirs and then its relationship with water quality through redundancy and regression analyses. Compared with taxon-based composition, the response of trophi-based composition appears simplistic and showed clearer tendency in relation with water-quality variables. Each trophi responded differently by the degree of eutrophication indicating that each trophi group is possibly affected by environments such as the combinations of water-quality variables in different ways.     

The ultrastructure of the mastax of Filinia longiseta (Flosculariaceae, Rotifera): Informational value of the trophi structure and mastax musculature

The study contributes to the discussion of mastax evolution within Rotifera by giving an insight into the ultrastructure of the mastax in the rotifer species Filinia longiseta (Flosculariacea) and additionally into the bdelloid rotifer species Adineta vaga and Zelinkiella synaptae. The existence of cuticularized jaw elements (trophi) in the mastax, a muscular pharynx, is one of the defining rotiferan characters and the basis on which the monophyletic taxon Gnathifera Ahlrichs 1995a, comprising Rotifera, Gnathostomulida, Micrognathozoa and Acanthocephala, was erected. By means of SEM observations of the trophi and ultrathin serial sections (TEM) of the mastax, the internal and external organization of the jaw elements of F. longiseta is reconstructed. TEM sections of the incus of Filinia demonstrate that the fulcrum and the rami are built up by multitudes of tiny cuticular tubes. While tubular substructures in the rotiferan fulcrum have been described previously, distinct cuticular tubes as a substructure of the ramus have only been described for species belonging to the taxa Seisonidea and Bdelloidea so far ( [Koehler and Hayes, 1969] and [Ahlrichs, 1995b]). By comparing the appearance and arrangement of the cuticular tubes in the rami of F. longiseta to those found in species of Seisonidea and Bdelloidea, a higher degree of resemblance between the structures in F. longiseta and Bdelloidea can be reported. The occurrence of the ramus substructures in species of Seisonidea (Paraseison annulatus and Seison nebaliae) is given consideration to represent an intermediate between the ramus substructure of Bdelloidea/Flosculariacea and Ploima. Additionally, the mastax musculature of F. longiseta, being associated with the trophi, is described: A total of seven muscles are found that directly insert the jaw elements or are indirectly associated with them via muscle-to-muscle connections.     

Revisiting the Cephalodella trophi types

The six trophi types proposed by Wulfert (Archiv für Hydrobiologie 31:592–636, 1937) are used as one main character to identify Cephalodella species, although these trophi types were just based on the trophi of 31 species described after light microscopy findings. Given the 160 species nowadays valid and the possibility of examining trophi with scanning electron microscopy it is questionable if the definitions of the six types might or rather have to be improved in order to facilitate species identification. Here, a new even simpler definition scheme is proposed to identify the six trophi types.     

Morphology of Floscularia ringens (Rotifera, Monogononta) from egg to adult

Abstract. 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 (<1 day), the young rotifer attaches permanently to a substrate and its morphology changes radically: the corona develops 4 wide lobes and the foot elongates, becoming slender and retractable. Once the corona has developed, the young animal begins to feed by producing filtering currents, and also starts to build its own tube. Here we report 4 new morphological details regarding this species. (1) A specialized epidermal groove is present on the trunk in front of the cloaca. (2) A small hole is located in the center of the inner surface of each pellet of the tube. (3) The muscles inside the foot are U-shaped in transverse section. (4) The size of the trophi remains unchanged during growth of the juvenile into an adult.