6 - Sphaeromatidae::“Cute As Buttons”

264 ZOOGEOGRAPHY
TABLE 4. {Continued)
Macrostylis setifer Menzies, 1962a. North of Puerto Rico Trench, 5477-
5494 m
Macrostylis vemae Menzies, 1962a. North of Puerto Rico Trench, 5410—
5684 m
Family Mesosignidae
Mesosignum kohleri Menzies, 1962a. Colombia abyssal plain, 2868-4076 m
Family Nannoniscidae
Nannoniscus camayae Menzies, 1962a. Off Panama, 1714 m
SUBORDER GNATH11DEA
Family Gnathiidae
Akidognathia poteriophora Monod, 1926. OffU. S. Virgin Islands, 914 m.
SUBORDER VALVIFERA
Family Arcturidae
Antarcturus annaoides Menzies, 1956b. South of Jamaica, 1244 m
Arcturus caribbaeus Richardson, 1901. OfTAves Island, 1360 m
Arcturus purpureus Beddard, 1886. Off Leeward Islands, 900 m
Note: Records from deep water around Bermuda are not included.
great area of mixed-salinity waters resulting from the outflow of the Orinoco,
Amazon, Tocantins, and Parnaiba rivers form an effective barrier to the
movement of shallow-water isopod species.
3. Species having an amphi-Panamic distribution—7 species, 4.2% [8,
3.7%] (Table 5). In spite of the history of immergence and emergence of the
Isthmus of Panama, this very small amphi-Panamic component in the Carib­
bean isopod fauna suggests that most of this fauna has evolved since the last
emergence of the late Pliocene. Given the limited mobility of most isopod
species, the Panama Canal seems to have played a minimal role in contribut­
ing to this component.
4. Species occurring outside of the western Atlantic (but excluding the
amphi-Panamic species)—3 species, 1.8% [7, 3.2%].
5. The role of the Gulf of Mexico isopod fauna (see Clark and Robertson,
1982) in the composition of the Caribbean/Bahamian is complex and diffi­
cult to analyze. One hundred and thirteen species of shallow-water isopods
have been recorded from the Gulf of Mexico (Table 6). This number would
indicate that many species remain to be recorded in this region. Of these 113
species, 61 (54%) have also been reported from the Caribbean region. It is
therefore possible that there exists a true Gulf of Mexico fauna, whose evolu­
tion was perhaps spurred by the relative isolation and reduction of the Gulf