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Family: Alpheidae
Snapping Shrimp
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Bocas Species Database Habitat: Alpheus immaculatus is found associated with the sea anemone species Bartholomea annulata at greater depths (15 m or deeper) than where A. armatus is usually found. It favors habitats such as coral reefs, and backreef lagoons. The tentacles of this sea anemone protect the shrimps from predators. Distribution: This species is reported from the Tropical Western Atlantic in Jamaica, Haiti, Netherlands Antilles and Panama. Natural History Notes: In 1980, detailed ecological and behavioral studies conducted by Dr. Nancy Knowlton showed the existence of several “morphs” of the species Alpheus armatus. Due to the fact that they reproduce in a strictly assortative way, those “morphs” had to be considered as different species from A. armatus. Three of those species have already been named as A. immaculatus Knowlton and Keller, 1983, A. roquensis Knowlton and Keller, 1985 and A. polystictus Knowlton and Keller 1985. There would potentially be a fourth species, A. aff. armatus, not yet described, but observed by Dr. Arthur Anker in Brazil. In addition to the absence of green spots, A. immaculatus differs from A. armatus by the slender shape of its rostrum and by the absence of a large white patch on the dorsal side of the major chela (claw). Knowlton and Keller (1983) also showed that the two species, A. immaculatus and A. armatus, do not interbreed. In the field, where the two species were encountered in the same area, no interspecific male-female pairs have been found. Also, in laboratory, when different interspecific male-female pairs were placed together in the same cluster of anemones, aggressive behaviors would be observed, whereas such behaviour would not be observed with intraspecific male-female pairs. Depth: At 15 m or deeper Characteristics: Alpheus immaculatus has a body length of about 37 mm. The female is generally slightly smaller than the male. The adult shrimps show a complex color pattern of red and white, semi-transparent patches. The adults also have their antennae striped red and white, whereas the juveniles have completely white antennae. Alpheus immaculatus has a rather slim rostrum (foremost extension of the carapace) that extends beyond the basal segment of the antennules. The eyes, enclosed in ocular hoods, are well developed and have a dark pigmentation. The ocular hoods are continuous with the carapace. The carapace has a smooth texture and its shape looks rather compressed vertically. The tail is composed of 5 abdominal somites (segments) with rounded shapes and the sixth somite is rather concave where the uropod is connected. The tip of the tail, called telson, is almost as wide as long (around 2∕3) and shows sinuous lateral margins. The telson is also equipped of two pairs of dorsal spines. Notes: The name "immaculatus", which means "spotless" in Latin, refers to the absence of green spots characteristic of the species Alpheus armatus. |
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