Palaemonetes paludosusriverine grass shrimp

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Geographic Range

Palaemonetes paludosus, commonly known as glass shrimp, eastern grass shrimp, or ghost shrimp, is naturally found in freshwater ponds, lakes, and streams in the coastal plain of North American east of the Allegheny Mountains, from Florida to New Jersey. The California Department of Fish and Game introduced Palaemonetes paludosus in the lower Colorado River, it is now established in various locations in California. It is also found in Louisiana, Texas, and Oklahoma, where it has most likely been introduced. (Beck and Cowell, 1976; Lowe and Provenzano, 1990)

Habitat

Eastern grass shrimp are primarily found in freshwater habitats. They have been found in brackish water, but there is no evidence that they persist there. They reside in some sort of aquatic cover and are most abundant in dense beds of submerged vegetation. Eastern grass shrimp are not common in areas of little or no vegetation. In summer months these shrimp are abundant among semi-aquatic grasses and water hyacinths. Preferred water temperatures range from 10°C to 35°C. (Beck and Cowell, 1976)

Physical Description

Eastern grass shrimp are transparent. Individuals grow to be approximately 47 mm long. Adults usually do not exceed 50 mm long. Males and females are dimorphic. Males are distinguished from females by differences in the first and second pleopods. Males can be separated from females by the presence of the appendix masculina attached to the appendix interna on the endopod of the second pair of pleopods. Also, the endopod of the first pleopod is larger in males than in females.

Several features distinguish caridean shrimp in the genus Palaemonetes from penaeidean shrimp. The pleura of the second abdominal somite overlap those of the first and the third walking legs and do not have claws in caridean shrimp. Other morphological features include the following: a well developed rostrum bearing both dorsal and ventral teeth, a smooth carapace and abdomen, rounded abdominal pleura, and well developed eyes with globular pigmented corneas. Eastern grass shrimp have six to eight teeth on the dorsal surface of the rostrum, three to four on the ventral surface, and none on the tip.

Seasonal variation in abundance has been reported. Palaemonetes paludosus abundance increases from May to August and then decreases throughout the remainder of the year. Maximum density of these shrimp is usually in August, minimum density is in April. Increased abundance in August can be explained by the presence of large numbers of juveniles in the population. Biomass is largest in the months of November, March, and August, respectively. Biomass is lowest in May. Growth of immature stages most abundant in August results in the large biomass peak in November, when populations contain many adults. The peak in March is a result of the abundant large, ovigerous females in the population. (Beck and Cowell, 1976)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    50 (high) mm
    1.97 (high) in

Development

Larval eastern grass shrimp hatch from eggs after an incubation period of approximately 12 to 14 days at 26 to 28°C. Development from hatching to maturity takes two to three months when water temperatures exceed 26° C, cooler temperatures delay maturation. Eastern grass shrimp larval development is short, consisting of three stages. They first undergo metamorphosis 5 to 10 days after hatching at 15 to 31°C. In the first larval stage (the first zoea), eastern grass shrimp range from 3.7 to 3.9 mm in size. The rostrum is straight with dorsal humps near its base and usually lacks spines. The abdomen has six segments, the last two being fused with the telson. The larvae are yellowish in color and the yolk is a dark green mass under the carapace posterior to the eyes. Second zoeae range from 3.8 to 4.1 mm in size. The main difference between first and second zoea is that the eyes are separated from the carapace, and a small pair of median telson spines are present. The rostrum has a single spine, and the carapace has a pair of supra-orbital spines and a pair of antero-ventral spines. Third zoeae range from 3.8 to 4.4 mm. The differentiating characteristics are the presence of uropods and a second dorsal spine on the rostrum. In the post larva stages, there is a loss of function on the thoracic appendages, elongation of the antennal flagellum, and the presence of setae on the pleopods. The rostrum has three dorsal spines. The pleopods are biaramus and aid with swimming. (Dobkin, 1963)

Reproduction

Eastern grass shrimp reproduce sexually. In pre-spawning females, their ripening ovaries take on a greenish color. Females become receptive to males after molting, during which time their exoskeleton is soft. Copulation occurs within seven hours of molting. The male only recognizes the female as a potential mate if physical contact is made with her exoskeleton. During copulation, the ventral surfaces of the partners are positioned so that their genitals are close together. A spermatophore is extruded by the male and transferred to the female, where it remains until oviposition. Oviposition occurs within seven hours after sperm transfer. Part of the spermatophore dissolves and the spermatozoa are released. Ova are fertilized externally as they are extruded, then adhere to the pleopods and setae on the ventral surface of the female's abdomen. (Beck and Cowell, 1976)

The breeding season for Palaemonetes paludosus varies with location and temperature of the water. Breeding usually occurs between early-February and mid-October at water temperatures of 18 to 33°C. However, glass shrimp breed year-round in Florida, where water temperatures are warmer. In pre-spawning females the ripening ovaries take on a greenish color. Many females carrying eggs often have ripe ovaries, suggesting two broods per female are possible. Females that hatch in early spring reproduce in late summer as small adults (20 to 24 mm long) and again in late winter as large adults (25 to 43 mm long). Females typically produce 8 to 85 eggs during their life cycle and carry them for up to 2 months. (Beck and Cowell, 1976)

  • Breeding interval
    Eastern grass shrimp breed twice per year in warmer temperatures.
  • Breeding season
    Breeding season varies by location and water temperature.
  • Range number of offspring
    8 to 35
  • Average number of offspring
    85
  • Average gestation period
    2 months

Like many crustaceans, eastern grass shrimp females carry developing eggs on their abdomen. Females carry the eggs for up to 2 months. (Beck and Cowell, 1976)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • female

Lifespan/Longevity

Eastern grass shrimp are confined to a one year life cycle. Post spawning mortality occurs from April to October. (Beck and Cowell, 1976; Beck and Cowell, 1976)

  • Typical lifespan
    Status: wild
    6 to 13 months

Behavior

Eastern grass shrimp are more active at night than during the day. They remain close to the bottom of a stream or lake during the day. This decreases their predation risk from visual predators. Because this species of shrimp is relatively large, it would be to their advantage to restrict daytime movement in order to avoid being spotted by visual predators. At night, however, any movement associated with foraging would be much less likely to result in attacks by visual predators. (Turner, et al., 1975; Wessel, et al., 2001)

Home Range

The home range size of eastern grass shrimp is unknown.

Communication and Perception

There is little available information on communication or perception in Palaemonetes paludosus.

Food Habits

The diet of eastern grass shrimp is dominated by algae (diatoms and green algae), but they also consume vascular plants, detritus, aquatic insects, and other benthic coarse particulate organic matter. Diatoms that glass shrimp eat include species in the genera Fragilaria, Nivicula, Stephanodiscus, Gomphonema, Synedra, and Cymbella. Examples of green algae consumed include species in the genera Cosmarium, Closterium, and Scenedesmus. In laboratory conditions, these shrimp were observed feeding on aquatic weeds. Insects they feed on include mayfly nymphs (Baetidae) and dipteran larvae in the families Chironomidae, Heleidae, Chaoboridae, and Culicidae. (Beck and Cowell, 1976)

Predation

Largemouth bass (Micropterus salmoides) and other fish feed on Palaemonetes paludosus. Vulnerability to predators is often inversely related to habitat complexity. With more complex plant cover, glass shrimp have more protection from predators. Eastern grass shrimp may remain close to the bottom during the day as a means of avoiding predation from visual predators, such as wading birds, waterfowl, and sunfishes and bass (Centrarchidae). Their transparent bodies may help to camouflage them. (Wessel, et al., 2001)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Eastern grass shrimp are important for energy flow and turnover of detritus in freshwater habitats and are important links between freshwater organisms found in benthic and water column habitats. Interactions among eastern grass shrimp, benthic predators, and nektonic omnivores have strong direct and indirect effects on benthic densities and community composition. Omnivorous shrimp are important organizers of community structure and play a key role in reducing sediment cover on rock substrates, which increases algal populations.

The parasitic isopod Probopyrus pandalicola uses Palaemonetes paludosus, among other shrimp, as hosts. These parasites sterilize female hosts by preventing ovarian maturation, although they do not effect external sex characteristics. Growth of external sex characters of male host are effected. The growth of chelae is accelerated, while the growth of pleopod structures is slowed. The parasite causes these changes though a combination of nutritional drain and hormonal interference. (Beck, 1980; Lowe and Provenzano, 1990; Turner, et al., 1975)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Because of their unique physical appearance, Palaemonetes paludosus is a common aquarium pet.

Economic Importance for Humans: Negative

There are no known adverse affects of Palaemonetes paludosus on humans.

Conservation Status

Palaemonetes paludosus is not currently listed as threatened or endangered.

Other Comments

The amino acid levels in Palaemonetes paludosus are more similar to levels found in marine decapods than to other freshwater invertebrates, such as crayfish like Astacus pallipes. Some suggest that how recent the freshwater invasion by a taxon can be determined by similarity in amino acid concentration of tissue to that of marine species. If this is true, eastern grass shrimp may be relatively recent invaders of freshwater habitats. (Turner, et al., 1975)

Contributors

Chelsea Baranowski (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

filter-feeding

a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.

freshwater

mainly lives in water that is not salty.

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

phytoplankton

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

year-round breeding

breeding takes place throughout the year

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

United States Fish and Wildlife Service. Species Profiles. Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (Gulf of Mexico). Grass Shrimp.. Biological Report 82 (11.35). Washington, D.C.: United States Fish and Wildlife Service. 1985.

Beck, T. 1980. The effects of an isopod castrator, Probopyrus pandalicola, on the sex characteris of one of its caridean shrimp hosts, Palaemonetes paludosus. The Biological Bulletin, 158/1: 1-15.

Beck, T., B. Cowell. 1976. Life history and ecology of the freshwater caridean shrimp, Palaemonetes paludosus. American Midland Naturalist, 96: 52-65.

Dobkin, S. 1963. The larval development of Palaemonetes paludosus (Gibbes, 1850)(Decapoda, Palaemonetes) reared in the labortary. Crustaceana, 6/1: 41-61.

Lowe, B., A. Provenzano. 1990. Survival and reproduction of Palaemonetes paludosus in saline water. Journal of Crustacean Biology, 10/4: 639-647.

Turner, R., E. Lowe, J. Lawrence. 1975. Isosmotic intracellular regulation in the freshwater palaemonid shrimp Palaemonetes paludosus. Physiological Zoology, 48/3: 235-241.

Wessel, K., R. Merritt, K. Cummins. 2001. Distribution, diel movement, and growth of the grass shrimp Palaemonetes paludosus in the Kissimmee River-floodplain ecosystem, Florida. Annales de Limnologie, 37: 85-95.