Appendicularia, Lahille, 1890

Karunarathne, Krishan D. & Croos, M. D. S. T. De, 2021, Pelagic tunicates (Appendicularia and Thaliacea) of Sri Lanka: two first records with an annotated checklist, Zootaxa 5067 (3), pp. 352-376 : 370

Key to the Appendicularia species of Sri Lanka

(based on Tokioka 1960; Bückmann 1969; Fenaux 1993, 1998; Aravena & Palma 2002)

1 Usually trunk flattened or spindle-shaped; endostyle curved upwards; tail orientated at the right angle to body: Family Fritillaridae............................................................................................. 11

- Trunk oval in shape and on the same axis as tail; endostyle straight: Family Oikopleuridae ........................... 2

2 Digestive tract incompletely developed; no oral glands and subchordal cells....................... Megalocercus huxleyi

- Digestive tract completely developed..................................................................... 3

3 Digestive tract forms a loop broadly open to the front; oral glands and subchordal cells present......... Stegosoma magnum

- Digestive tract compactly coiled into a nucleus.............................................................. 4

4 Oral glands and subchordal cells present................................................................... 8

- Oral glands and subchordal cells absent.................................................................... 5

5 Ceacum developed upwards and backwards............................................... Oikopleura fusiformis

- Ceacum directed either upward or backward only............................................................ 6

6 Small ceacum directed backwards......................................................... Oikopleura gracilis

- Finger-shaped ceacum directed upwards................................................................... 7

7 Ceacum close to the cardial region....................................................... Oikopleura longicauda

- Ceacum separated from the cardial region by a wide bight.................................... Oikopleura intermedia

8 Numerous subchordal cells, arranged in two rows............................................. Oikopleura albicans

- Subchordal cells few, arranged in a single row.............................................................. 9

9 With small postcardial ceacum on the left stomach lobe..................................... Oikopleura cophocerca

- Without postcardial ceacum on the left stomach lobe........................................................ 10

10 One spindle-shaped cell................................................................ Oikopleura rufescens

- Two spindle-shaped cells.................................................................. Oikopleura dioica

11 Anterior ovaries......................................................................... Tectillaria fertilis

- Posterior ovaries..................................................................................... 12

12 Distal end of the tail acuminate......................................................................... 15

- Distal end of the tail notched........................................................................... 13

13 Amphichordal cells absent................................................................ Fritillaria borealis

- Amphichordal cells present............................................................................ 14

14 Testis trapezoidal and laterally encircled by the ovary in a string.................................. Fritillaria venusta

- Testis Y-shaped and ovary spherical........................................................ Fritillaria pellucida

15 Ciliated rings of the branchial passages oval and elongated...................................... Fritillaria fraudax

- Ciliated rings of the branchial passages circular............................................................ 16

16 Trunk oval, compressed dorsoventrally...................................................... Fritillaria gracilis

- Trunk elongate, bent upwards in the digestive nucleus region..................................... Fritillaria formica