Rotifer Identification: The Brachionidae Hue University Rotifer Taxonomy workshop 6-12 March 2010

Rotifer Identification: The Brachionidae

Hue University Rotifer Taxonomy workshop 6-12 March 2010

Rotifer Identification: the Brachionidae

Classification Morphology:

Trophi Lorica

Identification Notes on biogeography and ecology Problems


Brachionidae: classification

Brachionidae Ehrenberg, 1838 Anuraeopsis Lauterborn, 1900 (5 spp.) Brachionus Pallas, 1766 (63 spp.) (Kellicottia Ahlstrom, 1938 (2spp.)) Keratella Bory de St. Vincent, 1822 (48spp.) (Notholca Gosse, 1886 (40 spp.)) Plationus Segers et al., 1993 (3 spp.) Platyias Harring, 1913 (3 spp.)


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


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)


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


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

Identification

Dorsal lorica facettation (foundation pattern): middorsal ridge or middorsal row of facets facets, extra facets, marginal facets,…

Caudal spines: 0, 1 or 2 but beware!


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


Biogeography

Cosmopolitanism important Latitudinal variation: Northern-hemisphere

centered, Gondwanan Endemism: important, less so in Africa;

strong in Australia, South America Historical!


Problems

Cryptic speciation?: see Keratella cochlearis - tecta group

Huge morphological variability Confused taxonomy and nomenclature

(infrasubspecific variants)


Anuraeopsis Lauterborn, 1900


Features: Small (!), Pelagic, microphages;Dorsal and ventral lorica plate, no spinesTypical egg mophology

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


Ecology

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


Brachionus Pallas, 1766

Morphology: Diagnosis = Trophi (except B. budapestinensis, B. murphyi) Lorica: trunk, not subdivided (corona)


Features: DIVERSE: pelagic and littoral; filter feeders - algae

Identification

Number of anterior dorsal spines

(0, 2, 4, 6)

relative size and shape of anterior spines

Shape of ventral head aperture margin


Identification

Position of foot aperture (terminal, ventral) Dorsal projection over foot aperture presence and

shape Special features


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


Biogeography

Cosmopolitanism important Latitudinal variation: tropic-centered Endemism: strong in Australia, South

America Historical!


Problems

Cryptic speciation: see Brachionus plicatilis group (papers:)

Huge morphological variability Confused taxonomy and nomenclature

(infrasubspecific variants)


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

Ecology and distribution

Littoral to (rarely) Pelagic Meso- to eutrophic cosmopolitan very common in rice fields


Features: Lorica: Dorsoventrally compressed, round Foot: ventral, pseudosegmentedTrophi: malleate

Platyias Harring, 1913


Features: Dorsoventrally compressed, round lorica, ventral pseudosegmented foot

Platyias Harring, 1913

Two Southeast Asian species: Platyias quadricornis and P. leloupi

Difference: dorsal lorica facettation: anterior pentagonal facet: P. quadricornis middorsal ridge: P. leloupi


Ecology and distribution

Littoral / benthonic freshwater browsers, grazers (?) P. quadricornis: cosmopolitan P. leloupi: tropical


Documents

Rotifer Identification: The Brachionidae Hue University Rotifer Taxonomy workshop 6-12 March 2010