''Eulimnadia texana'', the Texas clam shrimp or desert shrimp, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

belonging to the Limnadiidae family. It is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. It is an arid land specialist, living for many years as a cyst and bursting into life at the arrival of rains, maturing rapidly in temporary pools and producing eggs that can remain dormant until the next rains occur, perhaps in many years time.

Description

Desert shrimps are

sexually dimorphic Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

. The males have their front two pairs of thoracic appendages modified into claws while the hermaphrodites have unmodified legs.

Distribution and habitat

Desert shrimps live in ditches, ponds, pools, and other ephemeral freshwater habitats in northern

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

and parts of the southern and

southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural list of regions of the United States, region of the United States that includes Arizona and New Mexico, along with adjacen ...

, west of the

Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...

Biology

Individual shrimps are either male or

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

. The hermaphrodites can fertilize their own eggs or can mate with males but are unable to mate with other hermaphrodites. This arrangement is called androdioecy and is very rare among animals. The reproductive cycle varies between paired shrimps and isolated hermaphrodites and it is possible that using both strategies enhances the likelihood that fertile eggs will be available when the ephemeral water body in which they live dries up. Although to biologists, androdioecy seems a strategy unlikely to be successful, research using biogeographical,

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

and paleontological evidence has shown that the practice has persisted in the genus '' Eulimnadia'' for 24 to 180 million years. The shrimps are

omnivore An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize t ...

s and

filter feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a s ...

s, able to feed on the algae and microorganisms that also make use of the revived pool.

Life cycle

In the

Mojave Desert The Mojave Desert (; ; ) is a desert in the rain shadow of the southern Sierra Nevada mountains and Transverse Ranges in the Southwestern United States. Named for the Indigenous peoples of the Americas, indigenous Mohave people, it is located pr ...

, standing water occurs for only a short time after it rains. Storms are a rare event, and when a downpour occurs in the summer (making the water warm enough), eggs of the desert shrimp spring into life. They have been lying in the dust and baked clay of a dried-up pool in a dormant state for years, looking like grains of sand. The nauplius larvae which hatch outgrow with great rapidity. They undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

and reach a reproductive size in four to seven days. Each hermaphrodite then produces clutches of up to 300 eggs once or twice a day. By the twelfth day of their lives, they may be 5 mm long. During the course of their short lives, each may produce thousands of eggs. If time allows, several generations may occur. When the water evaporates and little remains of their pool, they dig a hole in the mud and bury their eggs as the water level falls. By the time the pool has dried, the shrimps are desiccated corpses. However, their eggs live on, waiting for the next rainstorm which may be decades away. During the intervening years, desert winds may carry away some of the eggs and a few may end up in locations where water accumulates after rain. This allows the shrimp to colonize new areas without traveling while active. Hermaphrodites live 25% to 50% longer than males in this species.

References

{{Taxonbar, from=Q4566841 Spinicaudata Freshwater crustaceans of North America Crustaceans described in 1871