EGG AND LARVAL DEVELOPMENT OF THE 

 ATLANTIC THREAD HERRING, OPISTHONEMA OGLINVM^^^ 



William J. Richards,^ Robert Victor Miller,'' and Edward D. Houde^ 



ABSTRACT 



The egg and larval development of Atlantic thread herring, Opisthonema oglinum, is described, 

 based on wild-caught eggs and laboratory-reared larvae. This description includes morphological 

 details of the egg and osteological development, changes in body shape and pigmentation, and 

 significant features of transformation of the larval development stages. The egg is 1.10 to 1.28 mm 

 in diameter with a single oil globule. Ossification commences in the larvae when they attain 

 10 mm in standard length and all bones have at least begun to ossify by 20 mm. During trans- 

 formation (15 to 25 mm), the larvae assume juvenile characteristics; particularly evident during 

 this period is the anterior movement of the dorsal and anal fins from their posterior larval 

 positions to their medial adult positions. 



The Atlantic thread herring, Opisthonema ogli- 

 num (Lesueur), is a clupeid fish commonly found 

 in the subtropical and tropical waters of the 

 western Atlantic Ocean, but the eggs and larvae 

 of this species have not been described previously. 

 In 1968, Atlantic thread herring were reared 

 from eggs in the Tropical Atlantic Biological 

 Laboratory, Miami, Fla. (now the Southeast 

 Fisheries Center), and a complete developmental 

 series was obtained (Richards and Palko, 1969). 

 This paper describes the egg and morphological 

 development of the reared larvae. We used a 

 dynamic approach, similar to that of Moser and 

 Ahlstrom (1970), to describe the sequential 

 development of characters, instead of a static 

 approach in which a few selected sizes of larvae 

 are described in detail. Larvae reared under 

 laboratory conditions provide unusually good 

 specimens for studies of this kind. 



The major purpose of describing eggs and larvae 

 is to provide information so that they may be 

 identified in field collections. Identification is very 

 difficult among the clupeids because all of the 

 larvae are very similar in appearance. This group 

 is further complicated by the many species that 



'Contribution No. 236, Southeast Fisheries Center, National 

 Marine Fisheries Service, NOAA, Miami, FL 33149. 



^Contribution No. 1790, Rosenstiel School of Marine and At- 

 mospheric Science, University of Miami, Miami, FL 33149. 



^Southeast Fisheries Center, National Marine Fisheries 

 Service, NOAA, Miami, FL 33149. 



"Southeast Fisheries Center, National Marine Fisheries 

 Service, NOAA, Miami, FL 33149; present address: National 

 Marine Fisheries Service, NOAA, Washington, DC 20235. 



^Rosenstiel School of Marine and Atmospheric Science, 

 University of Miami, Miami, FL 33149. 



Manuscript accepted October 1973. 

 FISHERY BULLETIN: VOL. 72, NO. 4, 1974. 



occur. In the western North Atlantic 15 genera, 

 representing about 36 species, are found. Three 

 genera are distinctive since they are found in 

 fresh water, or at least spawn and develop in 

 fresh to brackish water. Five other genera are 

 distinctive because of their long anal fin, and one 

 poorly known genus because of its very few 

 vertebrae. However, approximately 17 species re- 

 main represented by seven genera, which are 

 very similar in appearance. These genera are 

 Clupea (one species), Etrumeus (one species), 

 Jenkinsia (three species), Sreuoor^m (four species), 

 Opisthonema (two species), Harengula (three 

 species), and Sardinella (three species). Some 

 species within these genera are imperfectly 

 known (Berry, 1964). At our laboratories, three 

 other species have now been reared besides 

 O. oglinum — Sardinella anchovia, Brevoortia 

 smithi, and Harengula jaguana — and descrip- 

 tions of these are in preparation. Except for 

 Sardinella, it appears now that O. oglinum can be 

 separated from all of the other genera on the basis 

 of meristic characters. Brevoortia is similar in 

 most meristic characters, but its anal fin is found 

 nearly below the posterior end of the dorsal fin, 

 unlike Opisthonema. The eggs are very similar to 

 one another, but size and spawning times are help- 

 ful in separating the species. Much detailed work 

 is needed to work out these identification prob- 

 lems, not only for the eggs and larvae but for the 

 adults as well. A recent paper gives useful infor- 

 mation on these identification problems (Houde 

 and Fore, 1973). 



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