Key To The Species Of Freshwater Calanoid Copepods Of B.C. (Males Only)

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1. Caudal ramus with 5 short terminal setae (Figs. 4a, 10a, 23a, 28a), length of caudal setae _ to ½ that of the urosome (Figs. 4a, 23a, 28a); right 5^th leg with right exopod 2 ending in a long claw (Figs. 4c, 13a, 19a, 23b); 2

- Caudal ramus with 3 long terminal setae (Fig. 6a) or 4 long terminal setae (Figs. 7a, 8a), length of caudal setae more than ½ the length of the urosome (Figs. 6a, 7a, 8a); right 5^th leg with right exopod 2 ending in a long claw (Figs. 7c, 7d, 8b, 8c), a reflexed claw (Figs. 5b, 5c), or no claw (Figs. 6b, 6c) 3

2. Apex of last segment (segment 25) of right 1^st antenna with an outwardly produced process (Fig. 4b); inner process of exopod 2 on left 5^th leg digitiform, inserted distally (Fig. 4d); distal process digitiform, inserted on outer side of exopod 2 (Figs. 4e, 4f) Acanthodiaptomus denticornis (Wierzejski)

- Apex of last segment (segment 25) of right 1^st antenna without an outwardly produced process (Fig. 23f); inner process of exopod 2 on left 5^th leg digitiform or not, inserted on the inside of exopod 2 and directed laterally away from midline of the body (Figs. 10c, 13c, 21d); distal process digitiform or not, but inserted at distal end of exopod 2 (Figs. 10b) 6

3. Basal segment 2 of left 5^th leg with a long curved process (Figs. 5b, 5c, 6b, 6c) 4

- Basal segment 2 of left 5^th leg without a long curved process 5

4. Urosome asymmetrical, sometimes twisted, with projection on right side in dorsal view (Fig. 5a); right exopod 2 with only one segment, the distal end with a reflexed claw (Figs. 5b, 5c); distal end of left exopod 2 with 2 short spines (Fig. 5c) Epischura nevadensis Lilljeborg

- Urosome symmetrical, not twisted, without projection on right side in dorsal view (Fig. 6a); right exopod 2 with two segments, the distal end rounded at tip and without claw (Fig. 6c); distal end of left exopod 2 with 1 long spine and 1 short spine (Fig. 6b) Heterocope septentrionalis Juday and Muttkowski

5. Right 1^st antenna geniculate (Fig. 7a); distal end of exopod 2 on left 5^th leg enlarged with 2 processes, joined by a "U-shaped" area as seen in posterior view (Fig. 7d), in anterior view the distal end appears as a cup-like structure (Fig. 7c); hairs on dorsal surface of caudal ramus (Fig. 7b) Eurytemora affinis (Poppe)
- Right 1^st antenna non-geniculate (Fig. 8a); distal end of exopod 2 on left 5^th leg rounded, without processes, and with a small spine (Figs. 8b, 8c); without hairs on dorsal surface of caudal ramus

Senecella calanoides Juday

6. Left 1^st antenna with 2 setae on segment 11 (Figs. 10d, 12h, 18c), and either 1 seta (Fig. 18c) or 2 setae on some or all of segments 13-19 (Fig. 17c) 7

- Left 1^st antenna with only 1 seta on segment 11 (Fig. 3b), and only 1 seta on segments 13-19 (Fig. 3b) 16

7. Exopod 2 on left 5^th leg with inner process long (Figs. 9b, 10c); inner process of exopod 2 long and curved, approximately equal to exopod 2 in length (Fig. 10c) 8

- Exopod 2 on left 5^th leg with both inner and distal processes short (Figs. 13b, 14d, 15a, 15b, 18a); inner process of left exopod 2 a short spine, tooth-shaped or pointed, shorter than exopod 2 (Figs. 13b, 14c, 15b, 17d, 18d) 9

8. Segment 23 of right 1^st antenna with an antennal process (Fig. 9a), this process long, out-curved and tapering and reaching past antennal segment 24 (Fig. 9a) Aglaodiaptomus forbesi Light

- Segment 23 of right 1^st antenna without an antennal process but with a hyaline membrane along segment margin, extending slightly past distal end of segment (Fig. 10e) Aglaodiaptomus leptopus (Forbes)

9. Inner margin of basal segment 2 on right 5^th leg with serrate border (Fig. 13a), or with cuticular outgrowths (Fig. 11b) or denticulate border (Figs. 12b, 12d) 10

- Inner margin of basal segment 2 on right 5^th leg smooth, without serrate, or cuticular outgrowths, or denticulate border (Figs. 14a, 14b, 15c) 12

10. Inner process of exopod 2 on left 5^th leg a short, narrow-based spine (Fig. 11a); spines on segment 10 of right 1^st antenna shorter than spine on segment 13 (Figs. 11c-11e) Hesperodiaptomus kiseri (Kincaid)

- Inner process of exopod 2 on left 5^th leg a short, wide-based spine (Figs. 12c, 13c); spines on segment 10 same length as spine on segment 13 (Figs. 12e-12g) 11

11. Basal segment 2, right 5^th leg, with lengthwise ridge on posterior face usually bearing a large spine (Fig. 12d); right 1^st antennal process on segment 23 extending well past segment 24 (Figs. 12i, 12j) Hesperodiaptomus eiseni (Lilljeborg)

- Basal segment 2, right 5^th leg, with lengthwise ridge on posterior face bearing a very small spine in mid-point of ridge (Fig. 13a); right 1^st antennal process on segment 23 extending to end of segment 24 (Figs. 13d, 13e) Hesperodiaptomus arcticus (Marsh)

12. Segment 3 of left 1^st antenna with 1 unusually long seta, reaching to distal end of antennal segment 8 (Fig. 14e) Hesperodiaptomus hirsutus Wilson

- Segment 3 of left 1^st antenna with seta not so elongate, not reaching past distal end of segment 6 13

13. Segment 2 of left 1^st antenna with 4 setae (Fig. 15d); segment 11 with 2 setae (Fig. 15d) and each of segments 13-19 with 2 setae Hesperodiaptomus caducus Light

- Segment 2 of left 1^st antenna with 3 setae; segment 11 with 2 setae and each of segments 13-19 with one seta on each segment (Fig. 18c); or segments 13-19 with 1 seta on some of the segments and 2 setae on others (Fig. 17c) 14

14. Basal segment 1 of right 5^th leg with inner protrusion extending between left and right legs

(Figs. 16a, 16b) Hesperodiaptomus nevadensis Light

- Basal segment 1 of right 5^th leg without inner protrusion (Fig.17b) 15

15. Claw on right 5^th leg long, with length equal to combined lengths of basal segments 1 and 2 plus lengths of exopods 1 and 2 (Fig. 17a) Hesperodiaptomus novemdecimus Wilson

- Claw on right 5^th leg short, with length about equal to combined lengths of exopods 1 and 2

(Fig. 18b) Hesperodiaptomus kenai Wilson

16. Distal pad of exopod 2 on left 5^th leg with distinctive transparent lobes¹¹

(Figs. 19b, 19c) Hesperodiaptomus franciscanus (Lilljeborg)

- Distal pad of exopod 2 on left 5^th leg not lobed or transparent 17

17. Processes of exopod 2 on left 5^th leg not similar to one another, either both modified to form a pincer-like structure (Figs. 20b, 20c), or inner process modified into a curved seta with distal process digitiform (Figs. 21c, 21d, 22a, 22c) 18

- Both processes of exopod 2 on left 5^th leg similar to one another, digitiform (Figs. 23d, 23e, 26a, 31b); not modified to form a pincer-like structure, the inner process not modified into a curved seta 20

18. Both inner and distal processes of exopod 2 on right 5^th leg modified to form a pincer-like structure (Figs. 20b, 20c); lateral spine inserted mid-segment (Fig. 20a)..... Onychodiaptomus sanguineus (Forbes)

- Both inner and distal processes of exopod 2 on right 5^th leg not modified to form a pincer-like structure; inner process either short and curved (Fig. 21c), or long and curved, reaching well beyond end of inner process (Figs. 22a, 22c); distal process digitiform (Fig. 21d); lateral spine inserted in lower part of segment (Figs. 21b, 22a) 19

19. Right 5^th leg slender, basal segment 2 elongate, its length 3x its width (Fig. 21a); and with inner proximal portion produced upward (Fig. 21b) Onychodiaptomus hesperus Wilson and Light

- Right 5^th leg not slender, basal segment 2 not elongate but nearly square-shaped and without inner proximal portion produced upward (Fig. 22b) Skistodiaptomus pallidus (Herrick)

20. Segment 23 of right 1^st antenna without antennal process (Fig. 23f) 21

- Segment 23 of right 1^st antenna with antennal process (Figs. 26c, 27c, 27d) 23

21. Distal process of exopod 2 on left 5^th leg almost the same length as inner process

(Fig. 23e) Leptodiaptomus pribilofensis (Juday and Muttkowski)²

- Distal process of exopod 2 on left 5^th leg twice as long as inner process (Figs. 24a, 24c, 25c, 25d ) 22

22. Lateral spine of exopod 2 on right 5^th leg inserted in lower part of segment, just above claw base

(Figs. 24b, 24d) Skistodiaptomus oregonensis (Lilljeborg)

- Lateral spine of exopod 2 on right 5^th leg inserted close to middle of segment, some distance from claw base (Figs. 25a, 25b) Leptodiaptomus tyrrelli (Poppe)²²

23. Antennal process on segment 23 of right 1^st antenna long, reaching beyond distal end of segment 24 (Figs. 26c; 27c, 27d) 24

- Antennal process on segment 23 of right 1^st antenna short, not reaching beyond distal end of segment 24 (Figs. 28b, 28c, 29c, 29d) 25

24. Exopod 2 of right 5^th leg with proximal part of segment distinctly angled at point of insertion of lateral spine (Fig. 26b) Leptodiaptomus ashlandi (Marsh)

- Exopod 2 of right 5^th leg with proximal part of segment slightly curved but not angled at point of insertion of lateral spine (Figs. 27a, 27b) Leptodiaptomus insularis Kincaid

25. Lateral spine of exopod 2 on right 5^th leg inserted above middle of segment

(Figs. 28d, 28e) Leptodiaptomus nudus (Marsh)

- Lateral spine of exopod 2 on right 5^th leg inserted below middle of segment (Figs. 29a, 29b, 30a, 30b, 31a, 31b, 32a) 26

26. Spine on segment 8 of right 1^st antenna unusually large, about ½ the size of the spine on segment 11 (Figs. 29e, 29f) Leptodiaptomus connexus Light

- Spine on segment 8 of right 1^st antenna small, approximately ¹/₅ the size of the spine on segment 11 (Figs. 32c, 32d) 27

27. Segment 23 of right 1^st antenna with base of antennal process originating at mid-length of segment (Figs. 30c-30e) Leptodiaptomus novamexicanus (Herrick)

- Segment 23 of right 1^st antenna with base of antennal process originating at apex of segment

(Figs. 31d, 31e, 32e, 32f, 33a) 28

28. Segment 23 of right 1^st antenna with antennal process slender, reaching distal end of segment 24, and with swollen tip (Figs. 31d, 31e) Leptodiaptomus sicilis ( Forbes)

- Segment 23 of right 1^st antenna with antennal process broad, only reaching as far as mid-length of segment 24, and with tip outcurved (Figs. 32e, 32f, 33a) 29

29. Spine on segment 11 of right 1^st antenna subequal to or longer than spine on segment 13 (Figs. 32c, 32d); 5^th leg, right exopod 2 with a square-shaped inner process (Fig. 32b)

Leptodiaptomus siciloides (Lilljeborg)

- Spine on segment 11 of right 1^st antenna about ½ the length of the spine on segment 13 (Fig. 33c); 5^th leg, right exopod 2 with rounded inner process (Fig. 33b) Leptodiaptomus signicauda (Lilljeborg)

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