DEVELOPMENTAL ABNORMALITIES OF THE FLATFISH Achirus lineatus 

 REARED IN THE LABORATORY' 



Edward D. Houde- 



ABSTRACT 



Of 31 Achirus lineatus juveniles reared in a single experiment, 26 were abnormal. Abnormalities in- 

 cluded incomplete eye migration, hooked dorsal fins, the presence of a left pectoral fin, ambicoloration, 

 and partial albinism. The abnormal specimens have been described and photographed. A single re- 

 versed specimen, preserved as a nearly metamorphosed individual, also is described. Most of the 

 abnormal conditions were interrelated. Possible effects of the rearing tank environment on abnormal 

 development are discussed. 



Larvae of lined soles, Achirus lineatus (Lin- 

 naeus), were reared in the laboratory from 

 fertilized eggs collected in plankton tows from 

 Biscayne Bay, Fla. Development and details of 

 metamorphosis were described by Houde, Futch, 

 and Detwyler (1970). No developmental ab- 

 noimalities were detected until metamorphosis 

 was nearly complete. At 50 days after hatching, 

 the 31 survivors were examined and 26 (84 SO 

 were found to be abnormal. 



The unique metamorphosis of flatfishes 

 (Pleuronectiformes) may be responsible for the 

 high percentage of abnormal specimens reported 

 for this group in the literature (Norman, 1934; 

 Hubbs and Hubbs, 1945; Dawson, 1962). Most 

 of the described abnormal conditions in flatfishes 

 were encountered in lined soles from this rear- 

 ing experiment. Abnormalities included, in 

 order of frequency, (1) ambicoloration (25 

 specimens), (2) retention of left pectoral fin, 

 normally lost after metamorphosis (23 speci- 

 mens), (3) partial or no migration of the left 

 eye (17 specimens), (4) hooked dorsal fin, (same 

 17 specimens), (5) partial albinism (1 speci- 

 men), and (6) reversal (1 siiecimen). Similar 

 abnormalities have been described previously in 



' Contribution No. 198, fi-om the National Marine 

 Fisheries Service, Tropical Atlantic Biological Labora- 

 tory, Miami, Fla. 33149. 



' Present address: University of Miami. Rosenstiel 

 School of Marine and Atmospheric Science, Division of 

 Fishery Sciences, 10 Rickenbacker Causeway, Miami, 

 Fla. 33149. 



Manuscript accepted March 1971. 



FISHERY BULLETIN: VOL. 69, NO. 3. 1971. 



flatfishes, but are rare in the famil.v Soleidae 

 (Dawson, 1962) . None have been reported pre- 

 viously for A. lineatus. The extremely high 

 percentage of abnormal individuals among lab- 

 oratory-reared specimens from this experiment 

 apparently reflects some eff'ect of the aquarium 

 environment on the development of A. lineatus. 

 A high proiJortion of pigment-deficient individ- 

 uals of plaice (Pleuronectes platessa) was as- 

 sociated with high densities of metamorphosed 

 specimens in rearing tanks and with low food 

 levels in the tanks (Shelbourne, 1964, 1965;- 

 Riley, 1966), but other abnormalities were not 

 discussed. Although the exact nature of the 

 influence of the rearing tank on the production 

 of abnormal specimens of lined soles is unknown, 

 it is possible that harmful effects are created by 

 (1) frequent contact with sides of small rearing 

 tanks, (2) unnatural lighting, and (3) high 

 concentrations of metabolites. Seshappa and 

 Bhimachar (1955) reported failure of eye mi- 

 gration in the tongue sole Cynoglossus semifas- 

 ciatus (Cynoglossidae) when postlarvae were 

 kept in the dark. Two of my previous rearing 

 experiments with A. lineatus also produced ab- 

 normal individuals. Some juvenile specimens 

 of other flatfishes, Paralichthys alhigutta (Bo- 

 thidae) and Gymnachirus ynelas (Soleidae), also 

 developed abnormally when reared from eggs 

 hatched in my laboratory. The high incidence 

 of abnormalities in the reared lined soles sug- 

 gests that these conditions in flatfishes are not 



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