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

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

belonging to the Limnadiidae family. It is

endemic Endemism is the state of a species being found 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 found else ...

to North America. 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 the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

. 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 (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

and parts of the southern and southwestern United States, west of the

Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it fl ...

Biology

Individual shrimps are either male or hermaphrodite. 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 Androdioecy is a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison with the other major reproductive systems: dioecy, gynodioecy and hermaphroditism. In animals, androdioecy has be ...

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 (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

and

paleontological Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

evidence has shown that the practice has persisted in the genus '' Eulimnadia'' for 24 to 180 million years. The shrimps are omnivores and filter feeders, 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 ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily ...

, 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 Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

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 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 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