TUCKER: LARVAL DEVELOPMENT OF CITHARICHTHYS; AND ETROPUS 



Citharichthys amblybregmatus and C. dinocer- 

 os are deep water forms. Because of the constancy 

 of their environment, they may have extended 

 spawning seasons, but little is known of their 

 habits. 



Considering the geographic and bathymetric 

 distributions of adults (Table 1) and probable 

 spawning periods (Append. Table 5), it is un- 

 likely that large numbers of larvae of different 

 species of western North Atlantic Citharichthys 

 and Etropus cooccur in the ichthyoplankton at 

 any given time. Among the six deepwater spe- 

 cies, C. amblybregmatus and C. dinoceros larvae 

 probably occur relatively far from shore. Appar- 

 ently, there is little difference between larval 

 occurrence of C. gymnorhinus and C. cornutus, 

 but spawning centers or peak periods could be 

 distinct. Topp and Hoff (1972) suggested that 

 adults of the two species were bathymetrically 

 separated, C gymnorhinus being found in shal- 

 lower water. Etropus rimosus adults occur in 

 shallow water and do not spawn during the sum- 

 mer. Citharichthys arctifrons has a more north- 

 ern distribution than the preceding three species 

 and its spawning peak is in the summer, prob- 

 ably earlier than that of E. rimosus. Among the 

 three coastal species, the geographic range of C. 

 arenaceus is distinct from those of the other two, 

 and C. macrops and E. microstomas cooccur only 

 off the Carolinas. In this area of overlap, C. 

 macrops probably spawns in the fall and E. 

 microstomus in the spring. Among the three 

 estuarine and coastal species, C. abbotti spawns 

 in the warmer months and may be restricted to 

 very shallow water. Citharichthys spilopterus 

 spawns in the colder months, beginning in late 

 summer in the Gulf of Mexico and in mid to late 

 fall off the Carolinas. Etropus crossotus may 

 spawn from March through the summer, or 

 later, in the gulf, but probably does not begin off 

 the Carolinas until after most spawning activity 

 of C. spilopterus is finished. 



SUMMARY 



The caudal fin formula (4-5-4-4) is the most re- 

 liable character for linking larval specimens to 

 the group of paralichthyine genera Citharich- 

 thys, Cyclopsetta, Etropus, and Syacium. 



The most useful characters for identification 

 to genus are number of elongate dorsal rays, de- 

 gree of cephalic spination, and pigmentation. 

 Known western North Atlantic Syacium and 

 Cyclopsetta larvae have 5-10 elongate dorsal rays 



and well-developed preopercular and frontal- 

 sphenotic spines. Known western North Atlantic 

 Citharichthys larvae have two or three elongate 

 dorsal rays, small (or no) preopercular spines, 

 small frontal-sphenotic spines, no pectoral mel- 

 anophore (except possibly C macrops), little 

 notochordal pigmentation, usually large eyes 

 and mouths, and (except for C. arctifrons) high 

 gill raker counts. Known western North Atlantic 

 Etropus larvae have no or two elongate dorsal 

 rays, small preopercular and frontal-sphenotic 

 spines, a melanophore at the base of the pectoral 

 fin, extensive notochordal pigmentation, small 

 eyes, and low gill raker counts. 



Table 9 summarizes the most useful charac- 

 ters for distinguishing larvae of the six species of 

 western North Atlantic Citharichthys and Etro- 

 pus that have been described in detail. The best 

 characters for determining species are number 

 of elongate dorsal rays, number of caudal verte- 

 brae, pectoral and notochordal pigmentation, 

 number of left pelvic rays (C. gymnorhinus), 

 head shape and snout to anus length (C. spilop- 

 terus), number of gill rakers, and length at trans- 

 formation. 



Citharichthys arctifrons larvae have three 

 elongate dorsal rays, no preopercular spines, 

 many caudal vertebrae, a small eye, large 

 mouth, and few gill rakers. Citharichthys cor- 

 nutus larvae have three elongate dorsal rays, a 

 strong first left pelvic ray, heavy pigmentation, a 

 large eye and mouth, and relatively many gill 

 rakers. Citharichthys gymnorhinus larvae have 

 three elongate dorsal rays, few caudal vertebrae, 

 five left pelvic rays (with the first weak), a dis- 

 tinct caudal pigment band, large eye and mouth, 

 and relatively many gill rakers. Citharichthys 

 spilopterus larvae have two elongate dorsal rays, 

 few caudal vertebrae, little pigmentation, a 

 small eye and mouth, very blunt anterior profile, 

 short snout to anus length, and relatively many 

 gill rakers. 



Etropus crossotus larvae have two elongate 

 dorsal rays, heavy pigmentation, a small eye and 

 mouth, and many (for the genus) gill rakers. 

 Etropus microstomus larvae have no elongate 

 dorsal rays, a small eye, and few gill rakers. 



ACKNOWLEDGMENTS 



I wish to thank the following individuals and 

 institutions for their contributions to this study: 

 for loans and gifts of specimens — E. H. Ahlstrom 

 (NMFS, La Jolla); Charles Bennett, William 



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