Provisional Key to the Families of the Great Lakes Larval Fishes

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Petromyzontidae

2a. Chin barbels present (from 1b)

2b. Chin barbels absent (from 1b)

3a. Adhesive disc present on snout (from 2b)

3b. Adhesive disc absent (from 2b)

4a. Adhesive disc with papillae; recently hatched larvae 8-15 mm TL (from 3a)

4b. Adhesive disc smooth with sausage shaped enlargement; recently hatched larvae 5 - 8 mm TL (from 3a)

5a. Preanal length less than 30% TL; preanal myomeres less than 10 (from 3b)

5b. Preanal length greater than or equal to 30% TL; preanal myomeres greater than or equal to 10 (from 3b)

6a. Preanal myomeres greater than or equal to postanal myomeres (from 5b)

6b. Preanal myomeres signifcantly less than postanal myomeres (difference > 5 myomeres) (from 5b)

7a. Preanal myomeres approximately equal to postanal myomeres (difference ≤ 5 myomeres) (from 6a)

7b. Preanal myomeres signifcantly greater than postanal myomeres (difference > 5 myomeres) (from 6a)

8a. Postanal myomeres > 30 (from 6b)

8b. Postanal myomeres ≤ 30 (from 6b)

9a. Numerous oil globules; mouth superior; eye large, diameter usually > 8% TL (from 8b)

9b. Single or no oil globule; mouth terminal or inferior; eye small, diameter usually ≤ 8% TL (from 8b)

10a. Gut terminates immediately posterior to yolk sac; pectoral buds large; mouth terminal; swim bladder absent; pigment usually restricted to dorsum of head and dorso-lateral aspect of yolk-sac (from 9b)

10b. Gut does not terminate immediately posterior to yolk-sac; pectoral buds small; mouth terminal or inferior; swim bladder usually present; pigment not restricted to dorso-lateral aspect of yolk sac (from 9b)

11a. Mouth inferior; pigment concentrated on venter of yolk sac and from anus to caudal fn; preanal myomeres usually 14; greatest body depth usually 16-18% TL (from 10b)

11b. Mouth terminal; pigment variable; preanal myomeres usually 8 to 14; greatest body depth usually greater than 20% TL (from 10b)

12a. Total myomeres greater than 50; preanal length greater than 60% TL; preanal myomeres greater than or equal to 30 (from 7a)

12b. Total myomeres less than 50; preanal length less than 60% TL; preanal myomeres less than 30 (from 7a)

13a. Postanal myomeres usually less than or equal to 12 (from 12b)

13b. Postanal myomeres usually greater than or equal to 12 (from 12b)

14a. Numerous oil globules; yolk sac small; pectoral buds large; yolk-sac larvae large (5-9 mm TL); greatest body depth usually 16-17% TL; eye large, diameter 9 to 12% (from 13a)

14b. Single oil globule; yolk sac large; pectoral buds small; yolk-sac larvae small (1-5 mm TL); greatest body depth usually greater than 15 to 28% TL; eye small, diameter 6 to 9% (from 13a)

15a. Preanal myomeres usually greater than postanal myomeres (from 14b)

15b. Preanal myomeres equal to postanal myomeres (difference of one myomere) (from 14b)

16a. Total myomeres less a than 30 (from 13b)

16b. Total myomeres greater than or equal to 30 (from 13b)

17a. Postanal myomeres usually less than 15; oil globule anterior in yolk sac (from 16a)

17b. Postanal myomeres usually greater than or equal to 15; oil globule posterior in yolk sac (from 16a)

18a. Total myomeres less than 35; preanal myomeres less than or equal to 14 (from 16b)

18b. Total myomeres greater than or equal to 35; preanal myomeres greater than 14 (from 16b)

19a. Preanal myomeres usually 14; oil globule anterior in yolk sac; mouth developed; greatest body depth 16 to 18% TL (from 18a)

19b. Preanal myomeres usually less than 14; oil globule posterior in yolk sac; mouth not well developed; greatest body depth usually greater than 20% TL (from 18a)

20a. Oil globule absent; yolk sac bulbous; anus immediately posterior of yolk sac (from 18b)

20b. Anterior oil globule; yolk sac round; anus located far posterior to yolk sac (from 18b)

21a. Total myomeres usually greater than 48 (from 7b)

21b. Total myomeres usually less than or equal to 48 (from 7b)

22a. Preanal myomeres less than or equal to 39 (from 21a)

22b. Preanal myomeres greater than 39 (except for Esox niger) (from 21a)

23a. Total length usually 7 to 9 mm; yolk sac length 30 to 33% TL; venter of yolk sac pigmented, little dorsal pigment (from 22a)

23b. Total length usually 8 to 30 mm; yolk sac large or small, if large usually greater than 40% TL; if yolk sac large no pigment on venter, pigment most common on dorsum of larvae (from 22a)

24a. Postanal myomeres 13 to 17; larvae long and narrow; yolk sac small, round and far forward; total length usually 4 to 6 mm (from 22b)

24b. Postanal myomeres greater than or equal to 17; larvae long but robust; yolk sac elongate, extending to anus; total length greater than 6 mm (from 22b)

25a. Preanal myomeres 40 to 43; postanal myomeres 17 to 22; spiral valve evident; larvae unpigmented; eye undeveloped and unpigmented, diameter less than 5% TL (from 24b)

25b. Preanal myomeres 41 to 48; postanal myomeres 18 to 24; spiral valve absent; dark lateral stripe evident; dorsum pigmented; eye developed and dark pigment, diameter greater than or equal to 5% TL (from 24b)

26a. Postanal myomeres greater than 10 (Minytrema melanops may key here also) (from 21b)

26b. Postanal myomeres less than or equal to 10 (from 21b)

27a. Preanal myomeres 25 to 39; yolk sac elongate extending to anus, sometimes bulbous; oil globule absent; total length usually greater than 5 mm (from 26b)

27b. Preanal myomeres 37 to 41; yolk sac small and round; single or multiple oil globules present; total length usually 2 to 6 mm (from 26b)