NEW MARINE DECAPOD CRUSTACEANS FROM WATERS INFLUENCED BY 

 HYDROTHERMAL DISCHARGE, BRINE, AND HYDROCARBON SEEPAGE 



Austin B. Williams^ 



ABSTRACT 



Five species of decapod crustaceans new to science are described. These are caridean shrimps of the 

 family Bresiliidae — Alvinocaris markensis from a Mid-Atlantic Rift Valley hydrothermal field, A. 

 muricola from a cold brine seep at the foot of the West Florida Escarpment in the Gulf of Mexico, and 

 A. stactophila from a hydrocarbon seep on the continental slope of the northern Gulf of Mexico, with 

 a key to the species of Alvinocaris ; a squat lobster of the family Galatheidae — Munidopsis alvisca 

 from the Guaymas Basin and from the Juan de Fuca and Explorer ridges in the eastern Pacific; and 

 a brachyuran crab of the family Bythograeidae — Bythograea mesatlantica from a Mid-Atlantic Rift 

 Valley hydrothermal field. Species of both Alvinocaris and Bythograea are now known from the 

 eastern Pacific and Mid-Atlantic. Munidopsis species are widely represented in the world oceans. 



Deep ocean hydrothermally active fields and 

 waters influenced by brine and hydrocarbon seeps 

 continue to yield species new to science. Such en- 

 vironments were unknown until explored with 

 the aid of submersible research vessels from 

 which observations and collections could be ac- 

 complished. The species of decapod crustaceans 

 reported here come from hydrothermal fields in 

 the Mid- Atlantic Rift Valley, the Guaymas Basin 

 in the Golfo de California, and Juan de Fuca and 

 Explorer Ridges in the northeastern Pacific, a 

 cold brine seep at the foot of the West Florida 

 Escarpment, and a hydrocarbon seep on the con- 

 tinental slope of the northern Gulf of Mexico. 

 These are scattered localities that exhibit diverse 

 environmental conditions but that are bound 

 together by the common thread of chemotrophic 

 food chains (Childress et al. 1986; Brooks et al. 

 1987). 



The material from the Mid-Atlantic Rift Val- 

 ley, West Florida Escarpment, and Guaymas 

 Basin was observed and collected by scientists 

 working with the aid of the DSRV Alvin and RV 

 Atlantis II based at the Woods Hole Oceano- 

 graphic Institution. That from the northern Gulf 

 of Mexico came from the Minerals Management 

 Service Northern Gulf of Mexico Outer Continen- 

 tal Slope (MMS/NGOMCS) Regional Office Proj- 

 ect, involving observation and collection of mate- 

 rial by scientists from LGL Ecological Research 



iSystematics Laboratory, National Marine Fisheries Service, 

 NOAA, National Museum of Natural History, Washington, 

 D.C. 20560. 



Manuscript accepted January 1988. 

 FISHERY BULLETIN: VOL. 86, NO. 2, 1988. 



Associates and Texas A&M University, with the 

 aid of the submersible research vessel Johnson- 

 Sea-Link and its support vessels. Specimens from 

 Explorer and Juan de Fuca Ridges were collected 

 with the aid of the Canadian DSRV Pisces IV and 

 its support vessels. 



All specimens studied are deposited in the 

 Crustacean Collection of the United States Na- 

 tional Museum of Natural History, Smithsonian 

 Institution, Washington, D.C. 20560. 



CARIDEA: BRESILIIDAE 



Alvinocaris Williams and Chace, 1982 



Three species of bresiliid shrimps described 

 below as new to science are placed in the hereto- 

 fore monotypic genus Alvinocaris. Certain fea- 

 tures of these species necessitate minor changes 

 in the generic diagnosis by Williams and Chace 

 (1982) as follows: Rostrum with or without ven- 

 tral teeth. Telson with 2-5 pairs of principal 

 spines on posterior margin. Strong median ster- 

 nal spine between posterior pair of pereopods. 



Moreover, the branchial formula seems uni- 

 formly fixed in this genus as well as in the genus 

 Rimicaris Williams and Rona, 1986. The arrange- 

 ment, figured in Williams and Chace (1982) and 

 Williams and Rona (1986) may be described as 

 follows: 



Phyllobranchs extensively developed in 2 se- 

 ries; asymmetrically Y-branched pleurobranchs 

 with relatively short ventral and progressively 

 longer and more expansive dorsal ramus associ- 



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