GULF OF MEXICO 



307 



northern Florida and along the Gulf coast to Port 

 Aransas, Tex. 



Each large female produces each season several 

 to many thousand translucent ova which are 

 fertilized in the water and develop rapidly into 

 pilidium larvae. The eggs of this species have 

 been widely used in experimental studies and for 

 class demonstrations. Posterior regeneration takes 

 place readily, but anterior regeneration is limited 

 to the head anterior to the brain, although head- 

 less fragments, which can take no food, may live 

 for several months. With occasional changes of 

 the sea water and low temperature, a worm of this 

 species may live for a year or more without food, 

 the body meanwhile being reduced to a small 

 fraction of its original size. 



Order 3 HOPLONEMERTEA 



Family EMPLECTONEMERTIDAE 

 Paranemertes biocellata Coe, 1944 



This species may be recognized by the slender, 

 pale greenish body with sharply pointed head 

 bearing a single pair of oval, black ocelli near the 

 tip. The proboscis is provided with a slender, 

 cylindrical central stylet and either four or eight 

 pouches of accessory stylets. Size when mature 

 60 to 120 mm. in length and 2 to 4 mm. in width. 



This species is at present known only from 

 Biloxi, Miss., where it has been found burrowing 

 in the intertidal sand fiats and in shallow water. 



Family CARCINONEMERTIDAE 



Carcinonetnertes carcinophila Coe, 1902; Humes, 1941, 

 1942 



Nemertes carrinophilon KoUiker, 1845; Empledonema 

 carcinophila Verrill, 1895. 



This curious little nemertean is parasitic on 

 the gills of various species of crabs when young 

 and among the egg-masses of the host when 

 mature. The slender body is colored in various 

 shades of red, and there is a single pair of ocelli 

 on the head. The proboscis is very short; it has 

 a slender central stylet but no accessory stylets. 



At the time of reproduction a male and a female 

 place their bodies side by side and secrete a thick 

 sheath of mucus in which a hundred or more rela- 

 tively large eggs are deposited. Development is 

 of the direct type. 



Crabs of the family Portunidae, particularly 

 the lady crab (Ovipales ocellatun) and the blue 

 crab {(^allinectes sayidus) on the American coast 

 and Carcinus maenas in European waters are most 

 frequeatly infested, but representatives of other 

 families are occasional hosts (Humes 1942). 

 With the needlelike central stylet the young 

 worms presumably puncture the gills of the host 

 and suck out the blood, while the adults similarly 

 puncture the eggs of the host and suck out the 

 contents, whether yolk or embryo. It seems prob- 

 able that additional food for both young and adult 

 is obtained from such small animals as may be 

 encountered. 



Found on the Atlantic coast from the Bay of 

 Fundy to Florida and along the Gulf coast to 

 Texas, as well as on European shores from Scot- 

 land to the Mediterranean. The typical species 

 reaches a length of 20 to 70 mm., but Humes 

 (1942) found a smaller variety {C. carcinophila 

 imminuta) at Grand Isle, La., and at various 

 localities in the West Indies, Panama, and Brazil, 

 which differs in mmor morphological details. 



Family PROSORHOCHMIDAE 

 Oerstedia dorsalis Burger, 1895; Coe, 1940, 1943 



Planaria dorsalis Abildgaard, 1806; Tetrastemma dorsale 

 Verrill, 1892. 



Individuals of this widely distributed species 

 may be recognized by their small, cylindrical, firm 

 bodies often brightly colored and spotted or 

 banded in conformity with their environment. 

 Mature individuals seldom exceed 10 to 20 mm. 

 in length and 1 to 2 mm. in diameter. The head 

 bears four rather conspicuous ocelli. Proboscis 

 relatively large; provided with slender stylet on 

 pear-shaped basis and two pouches of accessory 

 stylets. The colors are extremely variable with 

 shades of red, brown, olive, whitish, or yellowish, 

 spotted, banded or striped with more deeply col- 

 ored pigment. 



Locally abxmdant among algae, Bryozoa, and 

 other growths on rocks and piles in the low inter- 

 tidal zone and below on the coasts of Europe to 

 Madeira, on the Atlantic coast of North America 

 from Nova Scotia to northern Florida, on the 

 Gulf coast westward to Texas, and on the Pacific 

 coast from Puget Sound to Mexico. The rela- 

 tively large eggs undergo the direct method of 

 development. 



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