PYCNOGONIDA 



By Joel W. Hedgpeth, Scripps Institution of Oceanography, University of California 



Our knowledge of the pycnogonid fauna of the 

 Gulf of Mexico is restricted to a few dredge hauls 

 in the northeast corner of the Gulf and some 

 scattered hauls farther south, the shore and 

 dredge collections at or near Tortugas, and a 

 few shore and buoy collections on the Texas 

 coast. Nevertheless, these records, particularly 

 those from the Tortugas, are of considerable 

 zoogeographical interest. Since the pycnogonids 

 lack an active, free-swimming larval stage, they 

 must rely upon passive means of dispersal. 

 Several instances of pycnogonid larvae in medusae 

 have been reported in the literature, and the 

 occurrence of several species in the sargassum 

 biota suggests an even more convenient vehicle 

 for dispersal (see Hedgpeth, 1947, for discussion 

 and summary of the hterature) . The distribution 

 pattern of several species along the coasts of 

 America, Europe, and Africa is similar to the 

 occiurence of stranded leguminous seeds, the "sea 

 beans," discussed with exhaustive thoroughness 

 byGuppy (1917). 



Another aspect of the fauna of special interest 

 is the occurrence of a ten-legged species, Penta- 

 colossendeis reticulata, along the southern edge of 

 the Florida Keys. A cognate octopodous form, 

 similar to the "normal" analogues of other ten- 

 legged species, has not yet been found for P. 

 reticulata. Its discovery would be a substantial 

 buttress for the author's theory concerning the 

 origm of ten-legged pycnogonids (1947), and 

 further collections, especially along the 100- 

 fathom line, should be of particidar interest. The 

 ten-legged Pentapycnon geayi Bouvier, known from 

 French Guiana and north of Puerto Rico, can also 

 be pjcpected in Gulf waters, especially in the 

 Tortugas area. 



Aside from the congregation of small, incon- 

 spicuous species at Tortugas there are relatively 

 few pycnogonids which are found in the waters of 

 the Gulf of Mexico and which, on the basis of our 

 inadequate information, might be considered char- 



acteristic of these waters. These have been indi- 

 cated on a distribution map (fig. 69). The large 

 prune purple pycnogonid, Anoplodactylus lentus, 

 has been collected at several stations in the north- 

 eastern part of the Gulf, at Tortugas, and off 

 Yucatan. A smaller form of this species is common 

 along the Atlantic coast from Carolina to Woods 

 Hole. Another species of this typically tropical, 

 warm temperate genus, A. insignis, common at 

 Tortugas, is found near Sanibel Island, in the 

 northeast corner off Cedar Keys, and due west of 

 Tortugas. It is common at Bermuda, and there 

 is one record (the type locality) off Bahia, Brazil. 

 Both of these species occur from near shore to 

 moderate depths; Anoplodadrjlus lentus, to 150 

 fathoms; A. insignis, to 48 fathoms. Another 

 large, conspicuous species, Pallenopsis schmitti. 

 found in depths from 20 to 155 fathoms, occurs in 

 the Tortugas area and off the coast of Florida near 

 the Bahamas. This species has also been found 

 north of Puerto Rico and the coast of Colombia. 

 The only species of Nymphon, a predominantly 

 cold-water genus known to occur in the Gulf, or 

 the entire American tropical area, for that matter, 

 is Nymphon fioridanum known from Tortugas and 

 off Cedar Keys. 



The shore collections from the western Gulf are 

 meager but interesting. Anoplodxictylus pygmaeus 

 has been found among the fouling growths on 

 buoys near Galveston, and Ammothella rugulosa 

 occurs among hydroids at Port Aransas. Anoplo- 

 dactylu^s pygmaeus is found off the coast of Virginia, 

 along the shore of southern England, and at 

 Naples. Ammothella rugulosa, a small easily over- 

 looked species, appears to be common at Tortugas 

 and along the southern coast of Florida. It has 

 been recorded from Brazil and Bermuda. 



A conspicuous gap in the distribution of pycno- 

 gonids in the western Gulf of Mexico is the 

 absence of Endeis spinosa, a situation confirmed 

 by the extensive collections of organisms asso- 

 ciated with fouling from New England to Panama 



425 



