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Rotifer Identification : The Brachionidae

Explore the classification, morphology, and ecology of Brachionidae rotifers, including identification techniques and notes on biogeography. Learn about the problems in classification and taxonomy of these diverse filter feeders.

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Rotifer Identification : The Brachionidae

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  1. RotiferIdentification: The Brachionidae

  2. Rotifer Identification: the Brachionidae • Classification • Morphology: • Trophi • Lorica • Identification • Notesonbiogeography and ecology • Problems

  3. Brachionidae: classification Brachionidae Ehrenberg, 1838 • AnuraeopsisLauterborn, 1900 (5 spp.) • BrachionusPallas, 1766 (63 spp.) • (KellicottiaAhlstrom, 1938 (2spp.)) • KeratellaBory de St. Vincent, 1822 (48spp.) • (NotholcaGosse, 1886 (40 spp.)) • PlationusSegers et al., 1993 (3 spp.) • PlatyiasHarring, 1913 (3 spp.)

  4. Some general features • Morphological diagnosis: • Malleate trophi • Trunk lorica present, dorsal and ventral plate, fused or separate • (corona features) • Weak diagnosis (esp. against Epiphanidae) • strong morphological adaptability (spine production and length, size) • Identification: Ahstrom 1940, 1943, Koste 1978, Koste & Shiel 1987 and scattered literature

  5. Key to the genera of Brachionidae: • No foot: • Lorica dorsal and ventral plate • Anterior spines: Keratella, (Kellicottia) • No anterior spines, large, drop-shaped eggs: Anuraeopsis • Lorica plates fused, unci teeth differentiated: (Notholca)

  6. Key to the genera of Brachionidae: • Foot present: • Foot annulated, crescent-shaped manubria shaft: Brachionus • Foot pseudosegmented • Lorica flat, rounded, foot ventrally: Platyias • Lorica high, foot terminally: Plationus

  7. Keratella Bory de St. Vincent, 1822 Morphology: • Diagnosis = Lorica • Elongate, stiff • Dorsal plate: transversally arched • 6(4) dorso-anterior spines, median largest and curved • Ventral plate bilobate anteriorly • Trophi: malleate Features: morphologically well-defined, ecologically diverse: pelagic and littoral; filter feeders - small algae

  8. Identification • Dorsalloricafacettation(foundation pattern): • middorsalridgeor • middorsalrow of facets • facets, extra facets, marginalfacets,… • Caudalspines: 0, 1 or 2 but beware!

  9. Ecology • Pelagic (no foot) to littoral • Oligotrophic to Dystrophic • (rarely) low to high pH • freshwater to marine • filter feeders on small unicellular algae • Very common and numerous in eutrophic and polluted waters

  10. Biogeography • Cosmopolitanism important • Latitudinal variation: Northern-hemisphere centered, Gondwanan • Endemism: important, less so in Africa; strong in Australia, South America • Historical!

  11. Problems • Cryptic speciation?: see Keratella cochlearis - tecta group • Huge morphological variability • Confused taxonomy and nomenclature (infrasubspecific variants)

  12. AnuraeopsisLauterborn, 1900 Features: Small (!), Pelagic, microphages; Dorsal and ventral lorica plate, no spines Typical egg mophology

  13. Anuraeopsis Lauterborn, 1900 Key to Southeast Asian species: • Lorica ornamented: A. coelata • Lorica smooth • Head aperture margin smooth, body shape: A. fissa • Head aperture margin with fine serration, body shape: A. navicula

  14. Ecology • Pelagic (no foot) • Meso- to eutrophic • freshwater, thermophilic • filter feeders on (very) small unicellular algae

  15. Brachionus Pallas, 1766 Morphology: • Diagnosis = Trophi (except B. budapestinensis, B. murphyi) • Lorica: trunk, not subdivided • (corona) Features: DIVERSE: pelagic and littoral; filter feeders - algae

  16. Identification Number of anterior dorsal spines (0, 2, 4, 6) relative size and shape of anterior spines Shape of ventral head aperture margin

  17. Identification • Position of foot aperture (terminal, ventral) • Dorsal projection over foot aperture presence and shape • Special features

  18. Ecology • Pelagic to littoral • Oligotrophic to Dystrophic • (rarely) low to high pH • freshwater to brackish • filter feeders on small unicellular algae • Very common and numerous in eutrophic and polluted waters

  19. Biogeography • Cosmopolitanism important • Latitudinal variation: tropic-centered • Endemism: strong in Australia, South America • Historical!

  20. Problems • Cryptic speciation: see Brachionus plicatilis group (papers:) • Huge morphological variability • Confused taxonomy and nomenclature (infrasubspecific variants)

  21. Plationus Segers et al., 1993 One Southeast Asian species: P. patulus • Lorica asymmetrical • 10 anterior spines • 2 postero-lateral, 2 postero-median spines of variable length (phenotypic plasticity!) Features: littoral/pelagic, filter feeders

  22. Ecology and distribution • Littoral to (rarely) Pelagic • Meso- to eutrophic • cosmopolitan • very common in rice fields

  23. Platyias Harring, 1913 • Features: • Lorica: Dorsoventrally compressed, round • Foot: ventral, pseudosegmented • Trophi: malleate

  24. PlatyiasHarring, 1913 Two Southeast Asian species: Platyias quadricornis and P. leloupi • Difference: dorsal lorica facettation: • anterior pentagonal facet: P. quadricornis • middorsal ridge: P. leloupi Features: Dorsoventrally compressed, round lorica, ventral pseudosegmented foot

  25. Ecology and distribution • Littoral / benthonic • freshwater • browsers, grazers (?) • P. quadricornis: cosmopolitan • P. leloupi: tropical

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