Pseudoplagiopyla, SMALL & LYNN, 1985

GENUS PSEUDOPLAGIOPYLA SMALL & LYNN, 1985

Diagnosis: Ovoid body shape, dorso-ventrally compressed; oral cavity deep, opening on ventral side with a more internal tubular part extending directly backwards ( Fig. 17C); dense somatic ciliature; one dumb-bell-shaped macronucleus and one roundish micronucleus; one species.

KEY TO THE SPECIES OF THE FAMILY PLAGIOPYLIDAE – MODIFIED FROM LYNN & SMALL, 2000 (Due to the scarcity of available morphological data, P. cucullio has been omitted from the present taxonomic key).

1. Tubular part of oral cavity in plane of long axis of body ................................................................................2

– Tubular part of oral cavity extending to the left ............................................................................................3

2. Tubular part of oral cavity curving anteriorly, then posteriorly with the presence of the furcula; endocommensals in gut of echinoids ................................................................................................ Plagiopyla mystax

– Tubular part of oral cavity extending directly backwards from outer oral cavity........................................ ............................................................................................................................... Pseudoplagiopyla sinistra

3. One macronucleus.............................................................................................................................................4

– Two macronuclei ............................................................................................................. Plagiopyla binucleata

4. Macronucleus ovoid, ellipsoidal, dumb-bell-shaped or reniform ....................................................................5

– Macronucleus vermiform .............................................................................................. Plagiopyla stenostoma

5. One micronucleus .............................................................................................................................................6

– More than one (up to five) vesicular-type micronuclei...................................................... Plagiopyla ramani

6. Free-living species ............................................................................................................................................7

– Endocommensal of sea urchins ........................................................................................................................8

7. Freshwater species ...........................................................................................................................................9

– Marine species ................................................................................................................................................10

8. Body length, on average, 50–75 µm; spindle-shaped extrusomes..................................... Plagiopyla minuta

– Body length, on average, 79–120 µm, no extrusomes................................................. Plagiopyla nyctotherus

9. One type of extrusomes .................................................................................................................................. 11

– Two types of extrusomes (straight and multi-layered, curved and homogeneus) .......................................... ............................................................................................................................. Plagiopyla narasimhamurtii

10. Straight/elongated extrusomes ......................................................................................................................12

– Curved extrusomes ............................................................................................................. Plagiopyla frontata

11. Straight extrusomes .......................................................................................................................................13

– Curved extrusomes ....................................................................................................... Plagiopyla megastoma

12. Body length, on average, 60–80 µm, micronucleus diameter less than 5 µm, one contractile vacuole pore ................................................................................................................................................. Plagiopyla ovata

– Body length, on average, 70–114 µm, micronucleus diameter around 5 µm, 1–2 contractile vacuole pores .............................................................................................................................................. Plagiopyla marina

13. Body length, on average, 80–130 µm, micronucleus diameter less than 5 µm .................. Plagiopyla nasuta

– Body length, on average, 135–150 µm, micronucleus diameter more than 5 µm ............ Plagiopyla simplex

Type species: Pseudoplagiopyla sinistra , by monotypy.