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Phylum Arthropoda
Subphylum Crustacea
Class Eumalacostraca
Order Decapoda
Family Alpheidae

Yagerocaris cozumel Kensley, 1988



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Yagerocaris cozumel: after Kensley, 1988

Taxonomic Characterization: Small shrimp with weakly pigmented eyes, partly concealed by carapace. Carapace with strong pterygostomian tooth and well developed cardiac notch. Upper antennular flagellum biramous. Exopods on maxillipeds 1-3. Epipods present on maxillipeds 1-3 and pereiopods 1-4. Chelipeds weakly developed, with carpus cylindrical, bearing a row of setae on mesial face, chela simple, not enlarged, fingers unarmed. Telson with posterior margin between inner pair of spines produced into rectangular lobe reaching more than halfway along elongate inner spines (Kensley, 1988; Chace & Kenlsey, 1992; Anker, pers. obs.). According to Anker (pers. commun.), Yagerocaris is not a hippolytid shrimp, as initially classified, but instead belongs to the family Alpheidae.

Ecological Classification: Stygobitic

Size: Specimens ranged in size from 5.5-7.2 mm carapace length.

Number of Species in Genus: One

Species Range: Known only from Cenote Aerolito and Cueva de Quebrada, Parque de Chankanaab, Cozumel, Quintana Roo, Mexico.

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Yagerocaris cozumel: USNM paratype

Closest Related Taxa: Possibly genera Salmoneus Holthuis, 1955 (Chace & Kensley, 1993) and Potamalpheops Powell, 1979 (Anker, pers. obs.)

Habitat: Anchialine limestone caves with direct connection to marine environments.

Ecology: Free-swimming specimens were collected from euhaline waters (marine salinity) at 9 to 12 m depths. The foregut of dissected specimen contained an unidentifiable brown finely macerated mush (Kensley, 1988).

Life History: Most known specimens show a combination of both male and female characteristics, being ovigerous and bearing a well developed, slender appendix masculina on the second pleopod, possibly indicating protandrous hermaphroditism. Protandrous hermaphroditism in cave species has a primary advantage correlated with larger size of breeding females. Secondarily, considering the somewhat restricted gene pool within caves, it would enhance opportunity for gamete exchange if two individuals encountering one another were both hermaphroditic and in the appropriate reproductive phase (Kensley, 1988).  Of the nine specimens reported on by Kensley (1988), 5 were ovigerous, 1 postovigerous and 3 nonovigerous.

Evolutionary Origins: Represents probably one of the most basal lineages within Alpheidae. The unusually strong pterygostomian tooth and the configuration of the telson have no equivalents among the alpheid genera.

Conservation Status: Known only from two anchialine caves with marine connections on Isla Cozumel.

References:

  • Chace, F.A. Jr. & B. Kensley. 1992. The cardiac notch in Decapods. Journal of Crustacean Biology, 12(3): 442-447.
  • Kensley, B. 1988. New species and records of cave shrimps from the Yucatan Peninsula (Decapoda: Agostocarididae and Hippolytidae). Journal of Crustacean Biology, 8(4):688-699, 7 figures.

Contributor: Dr. Arthur Anker, University of Alberta, Edmonton, Canada


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