THE NEMERTEAN FAUNA OF THE GULF OF MEXICO 



By Wesley R. Coe, Professor Emeritus, Yale University 



Nemerteans are found along all the seacoasts 

 of the world and off the shores to depths of hun- 

 dreds of meters. Some of the species are circum- 

 polar, extending southward along the Atlantic 

 coasts as far as Madeira or South Africa on the 

 east and to southern New England or Florida or 

 the Gulf of Mexico on the west, and in the Pacific 

 to California or Mexico on the east and to Japan 

 on the west. A few species live in both the North- 

 ern and Southern Hemispheres and a few others 

 in fresh-water streams and lakes. Some are 

 limited to the polar seas and others to the tropics, 

 but many have a wide geographical range and 

 survive under a great variety of environmental 

 conditions. Some of the bathypelagic species 

 live at depths of 1,000 to 2,000 meters or more, 

 and the populations may be carried for thousands 

 of miles by the deep ocean curreats, reproducing 

 generation after generation in their endless 

 circuits throughout the great oceans. 



With the exception of the species mentioned 

 in a few local lists of invertebrates, and two 

 papers by Coe (1951, 1951a) no reports of the 

 nemerteans ot the Gulf have been published previ- 

 ously. The following account is compiled from the 

 records of the collections sent to the writer from 

 various localities between Apalachicola, Fla., and 

 Port Aransas, Tex., during the past years. No in- 

 formation is yet available for all that portion of 

 the Gulf coast south of the Mexican border, 

 although there are several reports on the species 

 found at various West Indian islands. Several of 

 these species have been found on the Atlantic 

 coast of southern Florida and presumably occur 

 also on the Gulf coast (Coe 1951a). 



In the area covered by this report only 17 

 species are at present known, presumably for the 

 reason that only sporadic efforts have been made 

 toward a complete survey of the littoral fauna of 

 that region. On the Atlantic coast of North 

 America there are 53 known species of nemerteans 

 (Coe 1943) and on the Pacific coast 95 species 



(Coe 1940). Hence, it seems probable that less 

 than half of all the species now actually living in 

 the Gulf can be included in this report. 



Even on the Atlantic coast the nemerteans 

 have been studied extensively only as far south as 

 New Jersey, and our knowledge of the species 

 living between that State and Florida is based on 

 collections made at widely separated localities. 

 It may therefore be assumed that some, perhaps 

 many, additional species remain to be discovered. 



GEOGRAPHICAL DISTRIBUTION 



All except two of the species known from the 

 northern shores of the Gulf are also found on the 

 Atlantic coast. Therefore, it may be assumed 

 that the nemertean faima of this part of the Gulf 

 coast is, or has in the geologically recent past been, 

 a continuation of that of the Atlantic coast. It 

 seems quite possible that it is now a separate fauna 

 which was isolated in Pleistocene times by the 

 Florida peninsula. To determine whether the 

 species of the two areas are at present continuous, 

 it is essential to obtain additional collections on 

 both sides of the southern half of that peninsula. 

 It is already known that the species found at 

 Pensacola, on the Gulf side, are similar to those 

 found by the writer personally at St. Augustine, 

 on the Atlantic side. It is also known that these 

 two nemertean faunas are separated by an area 

 in which other species predominate (Coe 1951, 

 1951a). Because of the great differences in the 

 environmental conditions between the coasts of 

 northern and southern Florida, however, a more 

 or less complete separation would seem probable. 

 In other groups of invertebrates, likewise, the 

 species found in southern Florida are commonly 

 identical with those of the West Indies and 

 northern South America. 



The nemerteans evidently represent a conserva- 

 tive group and many of the species have a wide 

 geographical distribution. Of the 17 species at 

 present known from the Gulf of Mexico, all except 



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