Zooplankton of the Great Lakes

 

Chirocephalopsis bundyi

Classification

Kingdom - Animalia
Phylum - Arthropoda
Subphylum - Crustacea
Class - Branchiopoda
Subclass - Sarsostraca
Order - Anostraca
Family - Chirocephalidae
Genus - Chirocephalopsis
Specific epithet - bundyi

Taxonomic History

The first identification of Chirocephalopsis bundyi (fairy shrimp) was in 1876 by S.A. Forbes.  In the past, this species has been listed under the genera Eubranchipus and Pristicephalus (Dexter 1953)

Anatomy

Fairy shrimp are distinct members of the class Branchiopoda with stalked compound eyes, 11 pairs of swimming appendages, and a long, cylindrical body without a carapace (Ward and Whipple 1918).  These swimming appendages are used for locomotion, respiration, and food consumption.  Their total length usually ranges from 10 to 18 mm long (Pennak 1953).  The coloration in fairy shrimp is variable, but is mostly a whitish color.  The first antennae of this species are relatively small, uniramous, and unsegmented (Pennak 1953).  The body of a fairy shrimp is loosely distinguished as the head and the trunk segments.  The trunk segments includes the swimming legs, the genital segments, and the telson with two cercopods (Figure 3).

Female fairy shrimp have an elongated, cylindrical second antennae, while the males have large second antennae specialized for holding the females during copulation  (Pennak 1953).  This male species of fairy shrimp also has an antennal appendage, which is ribbonlike and coiled close to the second antennae (Figure 1).  The genital segment includes the two penes on the male and the egg sac on the female (Figures 1 and 2)(Pennak 1953).  In addition the females have a much more compact head and thinner body frame than the male fairy shrimp.

Distribution

C. bundyi has been observed in various different localities, but is common in the northern states and Canada.  Some of these locations include Alaska, the Yukon Territory, Alberta, Manitoba, Ontario, Quebec, Massachusetts, New York, Michigan, Wisconsin, Ohio, Indiana, and Wyoming (Pennak 1953).  The locations of these fairy shrimp are variable from year to year in distribution and abundance due to favorable conditions (Ward and Whipple 1918).  In most locations, males are less abundant than females. (Knight et al. 1975).  These populations of fairy shrimp are more abundant in the spring and then disappear in the summer with unfavorable temperature conditions.  C. bundyi is rarely found in bodies of water that are warmer than 15 degrees Fahrenheit.

Habitat

Fairy shrimp are mostly found in temporary ponds or vernal pools.  These bodies of water are usually fishless because they are too temporary, small, and alkaline for fish populations to survive (Pennak 1953).  Fairy shrimp are absent from lakes and are seldom found in bodies of water that exceed one acre.  These organisms would not be able to survive with fish as predators, but can usually survive with amphibians and carnivorous insects, which are other predators of the fairy shrimp.  Also, C. bundyi are restricted to clear ponds or pools in opposition to other fairy shrimp, which inhabit more muddy waters (Pennak 1953).

Feeding Ecology

The fairy shrimp primarily feed on algae, bacteria, Protozoa, rotifers, and bits of detritus (Pennak 1953).  This food is compacted in the ventral groove on a mucilaginous string located between the bases of the appendages.  The available food is constantly traveling forward to their mouth using the movement of their appendages (Ward and Whipple 1918).  Mastication of their food occurs right outside the digestive tract in an opening formed by the overhanging labrum (Pennak 1953).  It is believed that this species feeds continuously, but that not all of the food is ingested (Pennak 1953).  The primary food for C. bundyi are microscopic organisms and detritus, which they feed on at the bottom sediment with their ventral side pointed downward (Pennak 1953).  Fairy shrimp are normally found swimming gracefully on their backs with the swimming appendages faced up toward the light.  These organisms frequently rest on their dorsal side at the bottom sediments (Ward and Whipple 1918). 

Life History

Reproduction requires both the male and female for C. bundyi since they are not hermaphroditic.  Testes and ovaries are located on either side of the digestive tract and within the genital segment respectively for males and females.  The males begin by taking a dorsal position to the female with their second antennae clutched onto the females genital segment (Pennak 1953).  The male will turn its body at a particular angle to the female so that it can curve its posterior end and join its genital segment with the external uterine chamber of the female (Pennak 1953).  The process of copulation only takes a few seconds or minutes, but the pair may stay together for days before separating.

The female carries its eggs in an oval brood sac for one to several days before being released into the water.  The eggs are released in separate clutches (1-6 total) with anywhere from 10 to 250 eggs per clutch (Pennak 1953).  Some of these eggs become resting eggs as they dry out or are frozen until conditions are appropriate to hatch.  The resting period usually lasts about six to ten months under normal conditions (Pennak  1953).

The eggs of fairy shrimp hatch into a naupliar stage with three pairs of appendages, which will become the first antennae, second antennae, and mandibles in the adults (Pennak 1953).  These nauplii will go through a series of instars where they will shed their exoskeleton in order to grow.  Throughout these instars, the appendages will increase in number, size, and complexity (Pennak 1953).  At the sixth instar, all the appendages are present, but it is not until the sixteenth instar that sexual maturity is achieved (Pennak 1953).  Instars for the genus Artemia can be observed in Figures 3, 4, and 5 respectively at days one, three, and five after hatching.  Artemia are from the same order as fairy shrimp and show many similarities in their physical appearance as nauplii.

Literature Cited

Dexter, R.W.  1953.  Studies on North American fairy shrimps with the description of two new species.  The American Midland Naturalist 49(3):751-771.

Knight, A.W., R.L. Lippson, and M.A. Simmons.  1975.  The effect of temperature on the oxygen consumption of two species of fairy shrimp.  The American Midland Naturalist 94(1):236-240.

Pennak, R.W.  1953.  Fresh-water invertebrates of the United States.  The Ronald Press Company.  326-340.

Ward, H.B. and G.C. Whipple.  1918.  Fresh-water Biology.  John Wiley and Sons, Inc.  558-571.

 

Figure 1. Male fairy shrimp with distinguishing ribbon-like antennal appendages and small serrations on the 2nd antennae.

 

Figure 2. Female fairy shrimp with a prominent egg sac, 11 pairs of swimming appendages, and a compact head.

Figure 3. The forked tail or telson with two cercopods and numerous long filaments.

Figure 4.  Day one nauplius of Artemia.

Figure 5.  Day three nauplius of Artemia.

 

Figure 6.  Day five nauplius of Artemia.