Brachionus Pallas, 1766
Class Rotatoria: Order Ploimida: Family Brachionidae (ref. ID; 7097)

Synonym Noteus Ehrenberg, 1830 (ref. ID; 2891, 3688), Schizocerca Daday, 1883 (ref. ID; 3688)

[ref. ID; 953]
The structure of the trophi within the genus Brachionus is remarkably constant. The fulcrum is short and broad. The rami are broad, rounded externally and have conspicuous anterior processes onto which some membraneous filaments between rami and unci are attached. The median edge of the rami are adorned with rows of zig-zag like processes, apparently complementary to the unci. These consist of fused teeth-like projections of the rami. The rami are hollow structures, each having two cavities. Openings of these cavities are evident in dorsal view as a pair of large holes, and in caudal view as a second, smaller pair of holes. Each uncus is a more or less pentagonal plate, composed of almost completely fused, subequal teeth, with a subuncus. The distal part of the unci fit in cup-shaped articulations of the manubria. Cavities in the proximal part of the manubria are covered by a membrane. The external margin of the manubria is characteristic: it is sickle-shaped, and bent inwards distally: By this shape, the manubria fit around the rami when inactive, with their tips curved ventrad. (ref. ID; 953)

[ref. ID; 1663]
Dorsal and ventral plate of lorica completely fused laterally. Anterior dorsal margin of lorica usually with four or six spines. Posterior margin with or without spines. Body moderately flattened dorso-ventrally. Foot long, annulated, retractile, not segmented. Two toes. Mastax malleate. Planktonic species. Some of species are common and highly variable, especially in hard waters. Sometimes dense populations. (ref. ID; 1663)

[ref. ID; 2891]
The genus contains, to date, 30 distinct polymorphic species. There has, until now, been no unified agreement among authors on the taxonomic boundaries of distinguishable form-series within the genus; this applies also to obligatory unified nomenclature (Pejler 1977). Kutikova (1970) gave many ecotypes (varieties) and modifications (forms) the rank of subspecies. Ruttner-Kolisko (1972, 1974) divided the genus into groups (Formenkreis); clusters of similar and recognized related species ranked together as the urceolaris group, patulus group, quadridentatus group and angularis group. In this author's revision of Voigt's (1956-57) taxonomic work (Koste 1978) on the Rotatoria-Monogononta, the genus is divided into the following Formenkreis: (1) Formenkreis patulus (including (?)donneri and leydigi), (2) Formenkreis quadridentatus (including bidentata), (3) Formenkreis urceolaris (including pterodinoides, plicatilis, baylyi, variabilis, novae-zealandia and satanicus), (4) Formenkreis havanensis-zahniseri (including falcatus), (5) Formenkreis mirus (including diversicornis), (6) Formenkreis calyciflorus (including dimidiatus, gillardi and budapestinensis), (7) Formenkreis angularis (including charini, kasadensis, dolabratus, caudatus and forficula; keikoa). The taxonomy of the genus has, to date, been based on characteristic features of the lorica. The following are distinctive; general shape, spines and form of the dorsal and ventral anterior and posterior lorica margins, the form and spines of the foot-opening, and the structure and tesselation (foundation pattern) of the lorica surface. Correlations of these morphological characteristics with autecological and synecological factors are recognized only in individual species, e.g. lengthening of caudal spines in B. calyciflorus and B. bidentata as a response to the carnivorous Asplanchna in the same environment (Gilbert 1966; Halbach 1970; Pourriot 1974). (ref. ID; 2891)

[ref. ID; 3073]
Caudal region of Brachionus-spp. (ref. ID; 3073 )
The foot glands of Brachionus-spp. (ref. ID; 3073 )

[ref. ID; 3114]
In this genus, the following characters are regarded by Ahlstrom (1948) and Gillard (1948) as the specific taxonomically important ones. 1. Number of the occipital spines (six, four, two, wanting). 2. Length of the anterior spine and position of the longest spine (the longest spines are: anterior lateral, antero-intermediate, anterior median spines). 3. Basal plate (present or absent). 4. Mental margin (flexible, rigid, with four spine like protuberances with median sinus, irregularly elevated toward center). 5. Posterior spines (present or absent: if present, the direction of development: widely apart at the base, or quite close together. 6. Extension of the dorsal plate (over or not overhanging on the foot opening: with or without kneelike swellings on the inner side near the base.) 7. Foot sheath (present or absent: if present, whether it is longer or not than the long spines). 8. Proportion in the length of the anterior spines to the medians (as in zahnersi and satanicus). 9. Ornamentation of the lorica. 10. Lateral view of the posterior part of the lorica (truncated or pointed). 11. Shape of the occipital spines (saw-toothed or not). 12. Lorica (divided or undivided into dorsal and ventral plate). 13. Foot opening (with or without anchor-shaped spines). 14. Length of the anterior median spines (in havanaensis and var. rahes). According to the Sudzuki's opinion, all of the above criteria have not always the same value as taxonomic characters for the species; of all, the features (shape) of the occipital spines are the most important. Next, the features of the mental margins, the features of the posterior are (except the spines) are important. Nevertheless such criteria as whether the metal margin is flexible or rigid, and as the presence of the kneelike swelling on the inner side near the base do not seem so serious. (ref. ID; 3114)

[ref. ID; 4594]
Body flattened dorso-ventrally. Dorsal and ventral of lorica completely fused laterally. Anterior dorsal edge of lorica with six or four spines; anterior ventral margin with central sinus, with or without spines. Posterior margin with or without spines. Foot annulate, with two toes. Mastax malleate. (ref. ID; 4594)

Most confused Platyias.