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Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Order Decapoda
Family Palaemonidae

Creaseria morleyi (Creaser, 1936)

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Creaseria morleyi: from Cenote Ucil

Synonyms: Palaemon morleyi Creaser, 1936

Taxonomic Characterization: Preserved specimens are translucent to white in color. Eyes reduced, bullet-shaped and without pigment. Rostrum with dorsal and ventral teeth. Carapace with antennal and branchiostegal spines (Hobbs, 1977).

Disposition of Specimens: National Museum of Natural History, Smithsonian Institution, and The Museum, Texas Tech University.

Ecological Classification: Stygobitic

Size: Total length up to 70 mm. Male carapace length to 20.3 mm. Female carapace length to 29.0 mm.

Number of Species in Genus: One

Genus Range:

  • Yucatan Peninsula: Creaseria morleyi (Creaser, 1936)

Species Range: Widely distributed in caves and cenotes in the states of Quintana Roo, Campeche and Yucatan (the Northwestern and Northeastern Coastal Plains, the Sierra de Ticul and the Sierra de Bolonchen physiographic districts). Collection sites in Quintana Roo include Cueva del Fermin, Pozo de San Martin, Cenote de Juan Coh, Cenote de Las Ruinas, Cenote de Santa Domingo, Cenote de Tos Virlol, Cenote Ajin and Cueva Coop (Iliffe, 1992). Type locality is Cenote de San Isidro, Merida, Yucatan, Mexico.

Closest Related Species: No known close relatives

Habitat: Freshwater limestone caves

Ecology: Live in quiet water habitats ranging in depth from .5 m to greater than 3 m. Seen in areas of total darkness as well as entrance areas receiving light. These bodies of water are floored by guano, organic silt, debris and rocks. Have been observed crawling over the bottom of the substrate. In addition, they are swift swimmers that are extremely sensitive to vibrations. Within their stomachs was evidence of a cannibalistic lifestyle. These animals are very aggressive, if two or more are placed in a container, they will attack and mutilate each other (Hobbs, 1979).

Life History: A total of 101 specimens taken from 32 localities include 56 females, 24 males, 3 juveniles and 18 other specimens.

Evolutionary Origins: The shrimp were believed to be derived from a marine ancestor stranded by sea level regressions in the early Pleistocene (Wilkens, 1982).

Conservation Status: Restricted to freshwater caves and cenotes in Yucatan, Quintana Roo and Campeche. Classified as endangered by the NOM-059-ECOL-2001 "Norma Oficial Mexicana".


  • Creaser, E.P. 1936. Crustaceans from Yucatan. In: A.S. Pearse, E.P. Creaser & F.G. Hall (eds.). The Cenotes of Yucatan. pp. 117-132. Carnegie Institution, Washington Publ. 457, Washington, DC
  • Hobbs, H.H. III. 1979. Additional notes on cave shrimps (Crustacea: Atyidae and Palaemonidae) from the Yucatan Peninsula, Mexico. Proceedings of the Biological Society of Washington, 92(3): 618-633, 3 figures, 2 tables.
  • Hobbs, H.H. Jr and H.H. Hobbs III. 1976. On the troglobitic shrimps of the Yucatan Peninsula (Decapoda: Atyidae and Palaemonidae). Smithsonian Contributions to Zoology, 240: 1-23, 8 figures, 2 maps.
  • Hobbs, H.H. Jr and H.H. Hobbs III. 1977. A review of troglobitic decapod crustaceans of the Americas. Smithsonian Contributions to Zoology, 244: 1-185.
  • Iliffe, T.M. 1992. An annotated list of the troglobitic anchialine and freshwater cave fauna of Quintana Roo. Pp. 197-215 in: Diversidad Biológica en la Reserva de la Biosfera de Sian Ka'an, Quintana Roo, México, Vol. II, D. Navarro and E. Suárez-Morales, eds., Centro de Investigaciones de Quintana Roo, Chetumal, Q.R., Mexico, 382 pp.
  • Pérez-Aranda, L. 1983. Palaemonidae: Creaseria morleyi. Fauna de los Cenotes de Yucatan, No. 1, Universidad de Yucatan, Merida, 11 pp., 5 figures.
  • Wilkins, H. 1982. Regression evolution and phylogenetic age: The history of colonization of freshwaters of Yucatan by fish and Crustacea. Association of Mexican Cave Studies Bulletin, 8:237-243.

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