Thaliacea, Nielsen, 1995

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 : 370-372

Key to the Thaliacea species of Sri Lanka

(based on Smith et al. 1901, Van Soest 1973, 1974a, b, 1981, 1998; Madin & Harbison 1978; Godeaux 1998; Kim et al. 2011, 2017; Gershwin et al. 2014, Purushothaman et al. 2017; Adam & Ishak 2018; Ishak et al. 2018)

1 Colonial or solitary; zooids not embedded in a common, tube-shaped matrix...................................... 6

- Colonial; zooids embedded in a common, tube-shaped matrix: Family Pyrosomatidae ............................... 2

2 Colony entirely smooth.............................................................. Pyrosomella verticillata

- Colony with longer or shorter projections or denticulations.................................................... 3

3 Colony with longer or shorter truncate processes comprising oral siphons......................................... 5

- Colony with short triangular denticulations lying dorsal to the opening of the oral siphon............................ 4

4 Test thick and opaque; ascidiozooids longer than high, with angular endostyle................... Pyrostremma spinosum

- Test thin and transparent; ascidiozooids as high as long, with a curved endostyle................... Pyrostremma agassizi

5 Colony small (about 20 mm); oral siphon of ascidiozooids as broad as the branchial basket.......... Pyrosoma aherniosum

- Colony larger (about 50 mm); oral siphon much narrower than the branchial basket................. Pyrosoma atlanticum

6 Smallish; body muscles in complete parallel rings around the body; intestine forming an arch in gonozooid and oozooid / nurse: Family Doliolidae .................................................................... Doliolum denticulatum

- Largish; body muscles often incomplete and nearing or fusing: Family Salpidae .................................... 7

7 Without stolon; bearing gonads, one or more eggs or embryos (blastozooid / aggregate form)........................ 24

- With a stolon ventrally or posteriorly; gonads absent (oozooid / solitary form)..................................... 8

8 Gut usually bent into a more or less compact loop posteriorly and not accompanying the branchial bar; luminous organs always absent............................................................................................. 11

- Gut straight overlying the branchial bar; luminous organs present or absent; seven annular body muscles generally interrupted ventrally............................................................................................ 9

9 Dorsal longitudinal muscles present................................................... Cyclosalpa quadriluminis

- Dorsal longitudinal muscles absent...................................................................... 10

10 Luminous organs absent................................................................... Cyclosalpa affinis

- Luminous organs present............................................................... Cyclosalpa floridana

11 Less than eight body muscles........................................................................... 19

- Eight or more body muscles............................................................................ 12

12 Without two posterior processes / tails.................................................................... 14

- With two posterior processes / tails...................................................................... 13

13 Nine to 12 body muscles, widely interrupted ventrally; test firm, with finely denticulated longitudinal ridges................................................................................................. Metcalfina hexagona

- Sixteen to 22 body muscles, all interrupted dorsally and ventrally; test firm, thick and papillated............. Thetys vagina

14 Eight or 9 body muscles, M I to M IV fused or closely approaching dorsally; test soft, smooth, elongated cylindrical............................................................................................... Iasis cylindrica

- Nine or more body muscles parallel to each other, or M I to M III fused or approaching dorsally...................... 15

15 Nine body muscles, with ventral interruptions not widening toward the posterior end............................... 17

- Nearly parallel body muscles, with ventral interruptions widening toward the posterior end.......................... 16

16 Nine to 18 body muscles................................................................. Ritteriella retracta

- Nineteen to 31 body muscles................................................................ Ritteriella picteti

17 All body muscles parallel to each other; test smooth................................................ Salpa maxima

- Muscles I to M III fused or nearing dorsally............................................................... 18

18 Muscles VIII and M IX parallel or converging but not fusing, test ridges longitudinal and serrated............ Salpa aspera

- Muscles VIII and M IX strongly fused dorsally; test entirely smooth................................. Salpa fusiformis

19 Five broad body muscles interrupted dorsally and ventrally......................................... Soestia zonaria

- Four or five narrow body muscles, continuous dorsally...................................................... 20

20 Five body muscles; test bearing projections................................................................ 22

- Four body muscles firmly fused dorsally in two groups (M I–II and M III–IV); test barrel-shaped without projections..... 21

21 Atrial musculature reduced............................................................... Pegea confoederata

- Atrial musculature complicate............................................................... Pegea bicaudata

22 Body globular; several projections bulging into the test, some of them beyond it............. Traustedtia multitentaculata

- Body cylindrical, with two posterior projections............................................................ 23

23 Atrial palps simple and straight........................................................... Thalia democratica

- Atrial palps bifurcate....................................................................... Thalia sibogae

24 With a compact nucleus; four or more body muscles; luminous organs always absent............................... 27

- Without a compact nucleus; four body muscles; one pair of luminous organs may be present......................... 25

25 Luminous organs present........................................................... Cyclosalpa quadriluminis

- Luminous organs absent............................................................................... 26

26 All body muscles free dorsally.............................................................. Cyclosalpa affinis

- Muscles (M I–II and M III–IV) strongly fused dorsally, both groups nearing or touching in the mid-dorsal line............................................................................................... Cyclosalpa floridana

27 Five or six body muscles.............................................................................. 30

- Four body muscles................................................................................... 28

28 Posterior projections absent.............................................................. Pegea confoederata

- Posterior projections present........................................................................... 29

29 Test firm and cylindrical, with two short posterior projections...................................... Pegea bicaudata

- Test soft and globular, with three long posterior projections.............................. Traustedtia multitentaculata

30 Six body muscles.................................................................................... 35

- Five body muscles................................................................................... 31

31 Two groups of body muscles continuous, fussing or touching dorsally........................................... 33

- Body muscles parallel or approaching dorsally............................................................. 32

32 Broad and parallel body muscles, interrupted ventrally, M I interrupted dorsally; test very firm, with a posterior projection........................................................................................... Soestia zonaria

- Narrow and short body muscles, interrupted dorsally and ventrally; test firm, with longitudinal rows of spines.. Thetys vagina

33 Muscles I–III and M IV–V fusing or touching dorsally; body fusiform................................ Iasis cylindrica

- Muscles I–III and M IV–V separately dorsally, the total number of muscle fibers (M I–V) 15 to 17 (usually 16); body oval 34

34 Test smooth........................................................................... Thalia democratica

- Test papillated............................................................................. Thalia sibogae

35 Body muscles asymmetrically arranged.................................................... Metcalfina hexagona

- Body muscles symmetrically arranged into three dorsal groups, M I–II, M III–IV and M V–VI; test thick and firm; body fusiform.............................................................................................. 36

36 Muscles I–II and M III–IV equally fused dorsally, both groups touching or approaching dorsally..................... 38

- Muscles I and M II more strongly fused than M III–IV....................................................... 37

37 Number of muscle fibers 60–109........................................................... Ritteriella retracta

- Number of muscle fibers 110–169............................................................ Ritteriella picteti

38 Both anterior and posterior projections echinated, posterior projection with a bifid appearance............... Salpa aspera

- Test completely smooth............................................................................... 39

39 Muscle groups I–II and M III–IV closely approaching dorsally, M IV and M V not approaching laterally...... Salpa maxima

- Muscle groups I–IV fused dorsally, M IV and M V fused laterally................................... Salpa fusiformis