FISHERY BULLETIN: VOL. 76, NO, 1 



and cestodes. The role of these worms as agents of 

 disease in shrimps is uncertain. Most of the species 

 reported, to date, appear to have little effect on 

 individual shrimp infested, and probably little 

 significant effect on populations of penaeids. How- 

 ever, flatworms in penaeid shrimps are often con- 

 spicuous and, thus, attract considerable attention. 

 Penaeid shrimp usually play the role of inter- 

 mediate host for most, if not all, flatworms they 

 harbor; therefore, shrimps play a significant role 

 in the ecology of parasites that may be transmitted 

 through the food web to higher vertebrate hosts. 



Class Trematoda Rudolphi 1808 

 Subclass Digenea Carus 1863 

 Famly Microphallidae (Travassos 1920) 

 Genus Microphallm Ward 1901 

 Microphalltis sp. 



Hutton et al. (1959) reported an undescribed 

 species of microphallid trematode metacercariae 

 from pink shrimp. They found that from two to 

 three metacercarial cysts up to hundreds (from 1.2 

 to 1.5 mm in diameter) were encysted in muscle 

 tissue surrounding internal organs, particularly 

 the cephalothoracic and abdominal musculature. 

 No effect on the shrimp host was reported. 



Overstreet (1973) also reported an unidentified 

 microphallid metacercaria from abdominal mus- 

 cles of white shrimp from Barataria Bay, La. The 

 cysts were 93-95 ;u,m to 77-83 ixm, much smaller 

 than those reported from pink shrimp from west 

 Florida by Hutton et al. (1959). 



Family Opecoelidae Ozaki 1925 

 Genus Opecoeloides (Odhner 1928) 

 Opecoeloidei finihriatus (Linton 1934) 

 Sogandares-Bernal and Hutton 1959 



Metacercariae of this trematode (Figure 30) en- 

 cyst in hepatopancreas, other internal organs, and 

 beneath the exoskeleton ofPenaeus duorarum, P. 

 setiferus, and P. aztecus. This is a very common 

 parasite of penaeids, occurring in up to 90% of 

 some samples of pink shrimp taken during the 

 summer from Apalachee Bay, Fla. No extreme 

 pathogenesis in shrimp has been reported as- 

 sociated with O. fimbriatus. The worm is approxi- 

 mately 1.5 to 2.0 mm long when excysted and is 

 quickly identified by its possession of an extremely 

 pedunculate acetabulum (Figure 30). The sexu- 

 ally mature worm (adult) is found mostly in fishes 

 of the family Sciaenidae which feed on shrimps. 



The metacercaria is found in penaeids from the 

 Gulf and Georgia coasts. 



Class Cestoidea Rudolphi 1809 

 Order Trypanorhyncha Diesing 1863 

 Family Eutetrarhynchidae Guiart 1927 

 Genus Prochristianella Dolfus 1946 

 Prochriitiatiella hispida (Linton 1890) 



Campbell and Carvajal 1975 

 Synonyms: Khynchohothrittm hispidum 



Linton 1890; P. penaei Kruse 1959 



Plerocercoid larvae of this tapeworm are very 

 common in Penaeus setiferus, P. duorarum, and 

 P. aztecus. I have found up to 95% of large samples 

 of P. duorarum from northwest Florida to harbor 

 the cestode. This cestode is found mainly in the 

 hepatopancreas of the host (Figure 31), and most 

 often fails to elicit any strong pathologic response 

 from the shrimp. Sparks and Fontaine (1973) and 

 Feigenbaum and Carnuccio (1976) reported a 

 strong host reponse to the plerocercoid when it 

 encysted in hepatopancreas. I have not observed 

 this in several hundred hosts examined, but host 

 destruction of trypanorhynchan plerocerci may 

 occur rarely in shrimp. Most evidence suggests a 

 long and relatively tolerant relationship between 

 shrimp and cestode. Often a single shrimp will 

 have one to two dozen encysted larvae in its 

 hepatopancreas. 



According to my measurements, the worm (Fig- 

 ure 32a, b) has the following mean dimensions: 

 length — 1.12 mm; bladder or blastocyst = 0.58 

 mm long by 0.37 mm wide; and scolex ( below both- 

 ridia) =0.11 mm wide by 0.35 mm long. These 

 measurements are close to those of Kruse's (1959) 

 description. Though no lifecycle has been experi- 

 mentally completed for a trypanorhynchan, the 

 hosts for adult worms of this group are probably 

 sharks and rays. From nature, cestodes of this 

 order have been found in the spiral valves of elas- 

 mobranchii (Kruse 1959). Aldrich (1965) and 

 Ragan and Aldrich ( 1972) gave host-parasite data 

 on this species. 



Parachristianella monomegacantha Kruse 1959 

 P. diniegacantha Kruse 1959 



Kruse (1959) described two other trypanorhyn- 

 chan plerocercoid larvae from Penaeus duorarum. 

 These species were found in the hepatopancreas of 

 shrimp from the northern gulf coast and are dis- 

 tinct from one another "in hook arrangement and 



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