A KEY TO CLADOCERANS (CRUSTACEA) OF BRITISH COLUMBIA

KEY TO FAMILIES

1a) Thorax, abdomen and thoracic legs covered by the carapace. Brood chamber is a space between the body and carapace; legs foliaceous and not clearly segmented2

1b) Thorax, abdomen and thoracic legs not covered by the carapace; the carapace is present as brood chamber only; legs clearly segmented8

2a) Animal enclosed in a large gelatinous mantle Second antennae (swimming appendages) unbranched in femaleFamily Holopediidae

2b) Carapace not gelatinous. Second antennae branched 3

3a) Second antennae each with at least 15 setae (both branches combined)
Family Sididae

3b) Second antennae with 10 or fewer swimming setae(counting setae on both branches of antenna)4

4a) Both branches of the second antennae with 3 segments; first antennae at least partly covered by flanges on the side of the headFamily Chydoridae

4b) One branch of the second antennae with three segments the other with four (basal segment short); base of first antennae not covered by a flange on the side of the head5

5a) First antennae less than three times as long as wide and attached to head near the carapace margin Family Daphniidae

5b) First antennae more than five times as long as wide; not attached to the head near the carapace margin6

6a) First antennae rigidly fixed to head, tapered to a point and curved, resembling elephant tusks; first antennae with several sensory hairs about halfway between tip and base, none at tipFamily Bosminidae

6b) First antennae blunt and flexible; sensory hairs at the tip of the first
antennae7

7a) First antennae attached posterior to compound eye; post-abdomen with a row of lateral feathered setae, and a distal bident tooth on post-abdominal margin near base of post-abdominal clawFamily Moinidae

7b) First antennae attached anterior to, or just below, compound eye; no distal bident tooth on post-abdominal marginFamily Macrothricidae

8a) Body more than four times as long as high; second antenna with about 50 swimming setae, none longer than the branches of the
antennaFamily Leptodoridae

8b) Body less than twice as long as high; second antennae with about 25 swimming setae, some as long as the branchesFamily Polyphemidae

Family Holopediidae

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One species in the family, Holopedium gibberum
Zaddach, 1855.

Planktonic habitat. Animal surrounded by a mass of clear jelly attached to the carapace (often lost during collection or sorting). Widespread and common.

Family Sididae

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1a) Dorsal ramus of second antennae three segmented; 3-4 mm long; common among aquatic plants in lakes and pondsSida crystallina

The only known species in the genus Sida, S. crystallina occurs in lakes and ponds throughout British Columbia. Although it is predominantly littoral, it is also taken in open water plankton tows.

1b) Dorsal ramus of antennae with two segments2

2a) With lateral expansion on basal segment of dorsal ramus of antenna; with a tongue-like projection on ventral surface of headLatona setifera

A littoral species occurring in lakes and ponds, L. setifera appears to be widespread, but not common, in B.C.

2b) Without lateral expansion of antenna; no tongue-like projection on ventral surface of head3

3a) With anal spines on the post-abdomen; ocellus present; about 2 mm
longPseudosida bidentata

Although this species has been recorded from B.C., it is unlikely that it occurs here. It is known from the southern United States where it occurs in lakes and ponds. There are no known specimens from B.C.

3b) Without anal spines on the post-abdomen; ocellus absent; 0.8-1.2 mm long; common and widely distributed...............Diaphanosoma4

4a) Head about 2/3 the valve length; eye in the middle of the head near the ventral margin; reflexed antennae reaching or exceeding posterior margin of carapace; limnetic.Diaphanosoma birgei

Widespread and common in the limnetic zone of lakes in British Columbia. Previously recorded as D. leuchtenbergianum, this species was described in 1981 by Korinek. D. leuchtenbergianum is a European species not occurring in North America.

4b) Head no more than 1/2 valve length; eye anterior, occcupying most of the anterior region of the head; reflexed antennae not reaching posterior margin of carapace; littoral. Diaphanosoma brachyurum

Widespread and common in ponds and the littoral zone of lakes.

Family Daphniidae

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Key to Genera

1a) Ventral margin of carapace straight and usually black, posterior end of ventral margin extended into a point or spine; usually found in
vegetation.Subfamily Scapholeberinae2

1b) Ventral margin of carapace rounded and not pigmented 3

2a) Female with a more or less pointed rostrum in lateral view; ventral margin of head sinuate or slightly concave; posteroventral spine short; dorsum of valves with an oval plate (fenestra) situated on the anterior side of the dorsal
notchMegafenestra

2b) Female rostrum never acutely pointed in lateral view; ventral margin of head concave; posteroventral spine well developed; no dorsal plate
Scapholeberis

3a) Adults with a tail spine, usually at least four times as long as broad, and pointed; no cervical sinusDaphnia

3b) Adults without a tail spine -- or if one is present, it is less than four times as long as broad and rounded; cervical sinus present4

4a) Rostrum present; second segment of the four-segment branch of the second antenna with an apical spine, the spine about 1/4 as long as the second segment; carapace with transverse striationsSimocephalus

4b) Rostrum absent; second segment of four-segment branch of the second antenna without an apical spineCeriodaphnia

Genus Megafenestra

Megafenestra nasuta, is the only species of this genus reported from British Columbia.

Megafenestra aurita has previously been reported from British Columbia as Scapholeberis aurita. However a revision of the subfamily Scapholeberinae by Dumont & Pensaert (1983), concluded that M. aurita does not occur in North America. Reports of M. aurita are assumed to be M. nasuta, which is the only species of Megafenestra known to occur in North America. Uncommon in British Columbia.

Genus Scapholeberis

1a) Pecten on post-abdominal claw composed of numerous spinules; basal spinules not more robust than others; front of rostrum flaring distally; mucro (posteroventral spine) 1/3-1/2 length of ventral margin of
carapace Scapholeberis mucronata

The range of S. mucronata is poorly known because the name has been used incorrectly for other species. In a revision of the subfamily Scapholeberinae, Dumont and Pensaert (1983) report the distribution in North America as arctic and subarctic. Most, perhaps all, reports of this species in B.C. are probably misidentifications.

1b) Pecten of post-abdominal claw with 2-5 more strongly built basal spinules; females with rostrum triangularly produced; mucro 1/8-1/4 length of ventral marginScapholeberis rammneri

Common and widespread in British Columbia. The distribution of this species is poorly recorded due to confusion with S. mucronata M�ller 1776 and S. kingi Sars 1888.

In a revision of the Scapholeberinae, Dumont and Pensaert (1983) concluded that S. kingi does not occur in North America, and described a new species S. rammneri. All specimens of Scapholeberis examined in the collection of the Royal B.C. Museum are S. rammneri.

Genus Simocephalus

1a) Post-abdominal claws with a proximal pecten Simocephalus exspinosus

Reported from British Columbia only once (Carl, 1940), in Okanagan Lake. The presence of this species in B.C. needs to be confirmed.

1b) Claws with a row of fine spinules; no proximal pecten2

2a) Vertex evenly rounded about the eye and without serrations or
spinulesSimocephalus vetulus

In ponds and littoral zones of lakes, often on vegetation. Common and widely distributed.

2b) With serrations or spinules in front of or below the eyes; vertex more or less angulateSimocephalus serrulatus

Occurs in ponds and littoral zones of lakes. Often found attached to plants using sticky secretions produced from a gland at the back of the neck. Common and widespread.

Genus Daphnia

1a) Carapace continues anteriorly along mid-dorsal line as median strip between halves of head shield; heavy-bodied forms with little lateral
compression.Subgenus Ctenodaphnia2

1b) Apex of head shield continues posteriorly along mid-dorsal line onto carapace; large to small forms with marked lateral compression Subgenus Daphnia3

2a) Posterior margin of post-abdomen deeply sinuate in lateral view; female length to 5.0 mm; carapace spine usually shortDaphnia magna

D. magna is found in marginal habitats such as small ponds with abundant organic matter and saline ponds. Occasionally found along the margins of lakes.

2b) Posterior post-abdominal margin not sinuate; 10 to 14 anal spines; female length to 3.0 mm; carapace spine usually longDaphnia similis

Usually found in marginal habitats such as temporary, saline or alkaline ponds.

3a) Swimming setae of reflexed antenna reaching or surpassing posterior margin of valves; seta arising from first joint of three-segment ramus of second antenna does not reach end of ramus; a small speciesDaphnia longiremis

D. longiremis prefers cold waters. In the southern parts of its range, including most of B.C., it occurs in larger lakes. During summer when surface waters warm up D. longiremis is restricted to deep waters below the thermocline. In cooler northern regions it may occur in smaller water bodies. Widespread in B.C.

3b) Swimming setae of reflexed antennae never reaching posterior margin of valves in adult females; seta arising from first joint of three-segment ramus reaches or exceeds end of ramus4

4a) Teeth of all 3 pectens of post-abdominal claw small and inconspicuous, all about the same length5

4b) Teeth of middle and proximal pecten larger than teeth of distal pecten 9

5a) Animal small, head and valves of adult females 1 mm or less in length; head may be drawn out into a small point anteriorly or be rounded; carapace spine less than 1/2 carapace length, usually very shortDaphnia ambigua

An inhabitant of a variety of habitats from small ditches to lakes.

5b) Head and valves more than 1.25 mm long 6

6a) Second abdominal process in female much smaller than first, usually about 1/4 length of first; carapace spine very long 3/4 length of valves or
moreDaphnia laevis

Occurring in the southern regions of North America, D. laevis has been reported along the west coast as far north as “Puget Sound” in Washington State (Brooks, 1957). Although there are no specimens known from B.C., it is possible this species will be found here. Lives in ponds and swamps.

6b) Second abdominal process in female about half the length of first
process7

7a) Anterior margin of head often with low, rounded crest, but never produced into a helmet; head twice as deep as long; optic vessicle very close to anteroventral margin of head; spines on ventral margin on posterior half
only Daphnia rosea

An inhabitant of ponds and lakes, D. rosea is widespread and common in British Columbia.

7b) Anterior margin produced into a helmet so the head is always longer than half its greatest depth; spines on ventral margin of carapace usually extend over more than posterior 1/28

8a) Helmet usually pointed (sometimes rounded); dorsal margin of head never with concavity at level of most anterior antennal muscles; valves viewed laterally a broad oval, less than 1 1/2 times as long as wide; spinules extend over posterior 1/2 to 2/3 of ventral margin of carapace, never more
than 2/3Daphnia galeata mendotae

A lake-dwelling species, D. galeata mendotae is tolerant of warm temperatures and is often found in the upper layers of lakes. Limnetic.

8b) Helmet rounded; dorsal margin of head usually with concavity at level of most anterior antennal muscle; spinules extend over at least posterior 2/3 of ventral margin of carapaceDaphnia thorata

D. thorata is a medium to large species found in larger lakes. Head shape is variable, but a rounded helmet is always present. An atypical form with a very wide helmet is occasionally found in British Columbia lakes. Limnetic.

9a) Teeth of middle and proximal pectens of about the same length, somewhat larger than teeth of distal pecten; ocellus inconspicuous or absent10

9b) Teeth of middle pecten distinctly larger than teeth of either proximal or distal pectens; ocellus present11

10a) Anterior margin of head with broadly rounded crest, longest in mid-line; rostrum small; helmet rounded; carapace spine less than 1/4 valve length Daphnia parvula

An inhabitant of permanent ponds and small lakes D. parvula is widespread across the United States, and has been reported to extend into southern Canada (Brooks 1957).

10b) Anterior margin of head produced into helmet, apex of which is always dorsal to mid-line; carapace spine at least 1/3 length of valveDaphnia retrocurva

Uncommon in British Columbia D. retrocurva is known from lakes in glaciated regions east of the Rocky Mountains (Brooks 1957) and from Washington and Oregon (Pennak 1989). B.C. collections are from the limnetic zone of lakes.

11a) Ventral margin of head concave; optic vesicle contiguous with margin in lateral view12

11b) Ventral margin of head sinuate or more or less straight, never strongly concave; optic vesicle usually separated from margin in lateral view14

12a) Head longest over optic vesicle; exoskeleton of dorsal part of head often distinctly brown; carapace spine 1/3 to 1/2 of length of carapace; spines of middle pecten of post-abdominal claw separated at their bases; length 2.5 to 3.0 mm.Daphnia middendorffiana

D. middendorffiana is most common in shallow ponds and lakes of arctic and subarctic regions (Brooks 1957; Haney and Buchanan 1987). Uncommon in southern British Columbia it may be more abundant in northern areas of the province. Closely related to D. pulex.

12b) Head longest in mid-line or between mid-line and optic vesicle, with anterior margin of head more of less straight perpendicular to body axis; posterior margin of ventral part of head close to anterior margin of valves; exoskeleton of dorsal part of head not distinctly brown 13

13a) Reticulations between the antennules and the compound eye nearly symmetrical polygons; carapace spine 1/5 to 1/3 of carapace length in mature specimens; length 1.3-2.2 mm; in males dorsal abdominal process long, extending beyond the base of the dorsal abdominal setae; generally in small ponds, occasionally in shallow water along the edge of small lakesDaphnia pulex

The taxonomy of D. pulex and related species is very confused and it can be very difficult to distinguish this species from other species with large teeth in the middle pecten of the post-abdominal claw, especially D. pulicaria and D. middendorffiana. The characteristics used to separate these species are extremely variable and many intermediate forms occur. Brooks (1957) considered D. pulicaria a variety of D. pulex. Males are easier to distinguish based on the length of the anterior-most dorsal abdominal process, but are often not present for examination. D. pulex is a littoral species generally found in small ponds or occassionally in shallow water along the margins of lakes. It is common and widespread.

13b) Some reticulations between antennules and compound eye elongate; rostrum pointed and ventrally prolonged; carapace spine more than 1/3 length of carapace; in males dorsal abdominal process short never reaching the base of the abdominal setae; occurs in lakes and ponds.Daphnia pulicaria

As noted in the previous account D. pulicaria can be difficult to distinguish from D. pulex. Most authors consider D. pulicaria to be synonymous with North American specimens reported as Daphnia schodleri Sars (Grogg, 1977; Dodson, 1981; Evans, 1985). A limnetic species, D. pulicaria is widespread and common in lakes and permanent ponds of British Columbia.

14a) Spinules on dorsal margin of valves large, distance between spinules less than 1 1/2 times spinule length; post-abdomen with 13 to 16 anal spines, all nearly equal length; 4 to 7 teeth (usually 5 or 6) in middle pecten of
clawDaphnia pulicaria

14b) Spinules of dorsal margin of valves small, distance between spinules at least twice often three times spinule length; carapace spine 1/3 to 1/2 valve length; post-abdomen with 8 to 11 spines distal spines much larger; middle pecten with 2 to 4 (rarely 5) widely spaced teethDaphnia catawba

Although reported from British Columbia, this species is probably restricted to eastern regions of North America (Brooks 1957; Pennak 1989); it is doubtful it occurs in British Columbia. In the eastern U.S. it is found in the plankton of small to large lakes (Brooks, 1957).

Genus Ceriodaphnia

1a) Central pecten of claw of post-abdomen with prominent teeth2

1b) Central pecten of post-abdominal claw without prominent teeth; with thin spinules, the central pecten of which may be longer and heavier than the
distal3

2a) Central pecten of 2 to 8 teeth with sides evenly tapered to a sharp point, usually separated from each other and from adjacent pectens by a
spaceCeriodaphnia reticulata

A littoral species C. reticulata is found in ponds and shallow water along the margins of lakes throughout British Coumbia. Often among aquatic vegetation it generally does not exceed 1 mm in length.

2b) Central pecten of 8 to 16 narrow teeth with nearly parallel sides and sharp tips, often abutting each other Ceriodaphnia dubia

Widely reported as C. affinis (a junior synonym), C. dubia is the most common species of Ceriodaphnia in British Columbia. Two forms occur, one with a coarse central pecten on the claw of the post-abdomen, and one with a fine central pecten (Berner, 1986). Occurs in the limnetic and littoral zones of ponds and lakes throughout British Colulmbia.

3a) Post-abdomen sharply incised proximal to anus; dorsal margin serrated between midpoint and incision; anal denticles straight, increasing in size
distally Ceriodaphnia megops

Reported in most keys as C. megalops, the original spelling of this species was megops (Sars 1862) and so takes precedence. Generally found in shallow water with abundant organic matter. C. megops is a rare species. Although reported from B.C., there are no collections from the province available for examination. It has been collected from southern Alaska (D. Berner pers. comm.), so may occur in B.C.

3b) Dorsal margin of post-abdomen not incised 4

4a) Post-abdomen very broad at midpoint, obliquely truncated distally; anal denticles short, nearly equal in length; littoralCeriodaphnia laticaudata

If C. laticaudata occurs in British Columbia it is very rare. It has been found in Alberta, the western Northwest Territories and a small coastal pond in Oregon, so probably will be found in B.C. There are no specimens from B.C. in the collection of the Royal B.C. Museum, or in the collection of D. Berner (pers. comm).

4b) Post-abdomen not expanded broadly at midpoint5

5a) Fornices high, usually very extended dorsolaterally 6

5b) Fornices smoothly arched or only slightly expanded laterally7

6a) Large, heavily reticulated body; very small head and
eye .Ceriodaphnia acanthina

Primarily littoral, but occasionally collected in plankton tows. Widespread but not common in British Collumbia.

6b) Body small and not heavily reticulated.Ceriodaphnia lacustris

This species has been reported from B.C. but may have been confused with C. acanthina. Although it may eventually be found in British Columbia, there are currently no confirmed B.C. collections. Not known west of the Rocky Mountains (D. Berner pers comm). Limnetic.

7a) Cervical notch with a fenestra on the anterior surface; post-abdominal claw with spinules of central pecten slightly longer than distal pecten; antennule with sensory hair at about midpointCeriodaphnia dubia

The most common species of Ceriodaphnia in British Columbia. C. affinis is a synonym. Limnetic and littoral in lakes and ponds.

7b) Cervical notch without a fenestra on the anterio surface8

8a) Anal denticles recurved with longer, finer spines between the short spines proximal to the anus; post-abdomen tapered moderately beyond
midpoint Ceriodaphnia pulchella

Most collections from British Columbia are from central and northern regions, although this species probably occurs throughout the province. Widely distributed but not common. Limnetic and littoral.

8b) Anal denticles nearly straight, without long, fine spines; post-abdomen
narrowCeriodaphnia quadrangula

Widely distributed but not common in British Columbia. Primarily littoral among vegetation but also reported in the limnetic zone.

Family Bosminidae

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1a) Posterior-ventral angle of carapace rounded or pointed, but not produced into spineBosmina (Eubosmina) coregoni

Although reported frequently from British Columbia these reports are probably misidentifications based largely on a popular key by Brooks (1959), who described and illustrated B. longispina under the name B. coregoni. Lieder (1991) considers B. coregoni to be introduced to North America from Eurasia in the early 1960s possibly through a ship’s bilgewater in the Great Lakes. Known from eastern North America, it is unlikely this species occurs in B.C. Limnetic.

1b) Posterior-ventral angle produced into spine2

2a) Post-abdominal claw with a proximal pecten of 4 to 12 large spines, increasing in length distally, the distal one much larger than the remaining proximal spines; with a distal pecten of short triangular spines decreasing in size towards the end of the claw; frontal sensory bristle near midpoint between eye and tip of rostrum; common. Bosmina (Bosmina) longirostris

Common and widely distributed in British Columbia.

2b) Post-abdominal claw with proximal pecten of spines increasing slightly in size distally; with a distal pecten of very fine setae-like spinules; frontal sensory bristle near tip of rostrum, near or at base of
antennule.Bosmina (Eubosmina) longispina

Post-abdominal claws of specimens examined have a row of very fine spinules distally, visible under high magnification. This species has gone in and out of synonomy with Bosmina (Eubosmina) coregoni. Brooks (1959) illustrated this species under the name B. coregoni and also indicates fine distal spinules on the claw. Not as common as B. longirostris.

Family Leptodoridae

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One species in the family Leptodora kindtii (Focke, 1844). Adult females up to 18 mm long. Animals are transparent and difficult to see. Common in the open water of large lakes and are occasionally found in ponds. Predator on smaller plankton. Widely distributed in British Columbia.

Family Polyphemidae

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One species, Polyphemus pediculus (L.). Generally planktonic, found in lakes and ponds often near shore or in aquatic vegetation. A predator on protozoans, rotifers and small cladocerans; P. pediculus is widespread in British Columbia.

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