THE MYSIDACEA AND EUPHAUSIACEA 



By Albert H. Banner, Department of Zoology and Entomology, University of Hawaii 



Very lit tie is known of the mysid and euphausiid 

 fauna of the Gulf of Mexico. Only three articles 

 deal with the mysids of the region and only one 

 with the euphausiids, together reporting not over 

 a dozen stations mostly occupied before 1900 by 

 the steamer Albatross. Tattersall (1951), in his 

 review of the mysids of North America, reports 

 the following species from this region either on the 

 basis of previous records or specimens not previ- 

 ously reported: 



Family LOPHOGASTRIDAE 



Lophogaster americanus Tattersall. 

 Lophogaster longirostris Faxon. 

 Gnathophausia ingens (Dohrn). 



Family PETALOPHTHALMIDAE 



Petalophlhalmus armiger Willemoes-Suhm. 

 Family MYSIDAE 



Gastrosaccus dissimiiis Coifmann. 

 Gastrosaccus mexicanus Tattersall. 

 Mysidopsis bigelowi Tattersall. 

 Metamysidopsis munda (Zimmer). 

 Mysidium integrum Tattersall. 



Hansen (1915), in his similar review of the 

 euphausiids of the U. S. National Museum, lists 

 two species collected by the Albatross in 1885 and 

 one species collected by the Grampus in 1889: 

 Thysanopoda pectinata Ortmann, Thysanopoda 

 orientalis Hansen, and Euphausia tenera Hansen. 



All of the species of euphausiids and the species 

 of the first two families of mysids reported are 

 pelagic or bathypelagic forms and were found in 

 the d eeper water of the Gulf. The species reported 

 from the family Mysidae are all neritic forms and 

 were collected relatively close to land. 



The shortness of this list should not be construed 

 to be indicative of an impoverished fauna either 

 in numbers of species or in numbers of individuals, 

 but rather it should be seen as an indication of 

 insufficient sampling. To catch these relatively 

 large and active planktonts it is necessary to tow 

 for them with large and rather coarse-meshed 



plankton nets; as many of the species exhibit 

 diurnal migrations it is necessary to tow either at 

 the surface after dark or in deeper water during 

 the day. To capture many of the species of 

 mysids it is necessary to sample the waters imme- 

 diately above the mud and sand bottoms, for 

 mysids are often hypoplanktonic and spend most 

 of their lives hovering immediately above the 

 bottom. When adequate sampling is carried out 

 the number of species of both mysids and euphau- 

 siids can be expected to at least quadruple. 



When the fauna of the Gulf is better known the 

 "schizopods" will be found to be divisible into 

 four major ecological groups: 



1. Epipelagic {or epiplanktonic) species. — This 

 group, living in or near the photic zone of the open 

 sea, will include a few species of mysids but most 

 of the species of euphausiids. The species probably 

 will be found to be relatively widespread in the 

 adjacent regions of the subtropical and tropical 

 Atlantic at least, and possibly will be found to be 

 circumtropical like Euphausia tenera listed above. 



2. Bathypelagic species. — This group will con- 

 tain both mysids and euphausiids but will be rich 

 neither in number of species nor in number of 

 individuals. Most species that will be found 

 probably will have extremely wide ranges of dis- 

 tribution like Petalophthalmus armiger which is 

 also kno\vn from off Ireland, the Gulf of Panama, 

 the Gulf of Aden, the Bering Sea, and off Hawaii, 

 to list a few of its localities of capture. 



3. Neritic species. — This portion of the "schizo- 

 pod" fauna will be composed mainly of species of 

 mysids with the addition of some species of 

 euphausiids. The distribution ranges of species in 

 this group will be more narrow than those of the 

 pelagic group; some at least will extend for 

 thousands of miles along the coasts. Examples of 

 the type of range are Mysidopsis bigelouji which is 

 known to extend from Massachusetts to Louisiana 

 and Metamysidopsis munda which extends from 

 Chesapeake Bay to the coast of Brazil. Other 

 species may have a more limited distribution. 



447 



