108 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



value of the characters used to associate the Ophichthoidea with 

 the Congroidea and implied that the Ophichthidae could just 

 as easily be a specialized offshoot of the Anguilloidea. While 

 the only known larvae which could be confused with the 

 Ophichthidae are members of the family Congridae (e.g., Ac- 

 romycter larvae have pronounced gut loops. Nystactichthys lar- 

 vae have a gut which expands abruptly between the esophagus 

 and intestine), there are no known larval characters which un- 



equivocally establish the evolutionary relationships of the 

 Ophichthidae. Careful osteological studies of ontogenetic series 

 of eel larvae from the various families may eventually clear the 

 currently clouded picture. 



Department of Natural Resources, Marine Resources 

 Laboratory, 100 Eighth Avenue Southeast, Saint Pe- 

 tersburg, Florida 33701. 



Clupeiformes: Development and Relationships 

 M. F. McGowAN AND F. H. Berry 



THE order Clupeiformes contains four families of fishes: the 

 herrings, Clupeidae; the anchovies. Engraulidae; the wolf- 

 herrings, Chirocentridae; and the denticle herring, Denticipiti- 

 dae (Nelson, 1976). Denticeps clupeoides. the monotypic den- 

 ticipitid, occurs in freshwater in southwest Nigeria (Clausen, 

 1959). Two species of Chirocentrus occur in marine waters of 

 the Indo-Pacific region from the Red Sea to the western Pacific 

 (Whitehead, 1972). They are unusual among the Clupeiformes 

 in that they are piscivorous. The herrings and anchovies are, in 

 general, small schooling planktivores of marine coastal waters. 

 The Indo-Pacific shad, Tenualosa reevesii. reaches 509 mm 

 standard length; the West African riverine species, Thrattidion 

 noctivagns and Sierrathrissa leonensis. are mature at 18 mm 

 (Wongratana, 1980). There are 192 species of clupeids in 62 

 genera and 122 species of engraulids in 16 genera (Table 24) 

 based on our review of the literature. Herrings and anchovies 

 are most speciose in the tropics, and individual species are most 

 abundant in cold temperate regions and eastern boundary cur- 

 rents (Longhurst, 1971). Some are found in fresh or brackish 

 water; some are anadromous. They support major fisheries 

 worldwide. Their biology has been reviewed most recently by 

 Blaxter and Hunter (1982). 



Development 



The eggs and the larvae of Chirocentrus are known (Delsman, 

 1923, 1930b); the egg and larva oi Denticeps are unknown; and 

 the eggs or larvae of at least one species in a genus have been 

 described for approximately one-half the genera of herrings and 

 anchovies but for only one-third of all species. Ontogenetic 

 stages of herrings and anchovies are best known for species of 

 commercial interest or potential commercial interest in regions 

 with low clupeoid diversity such as the northeast Atlantic (e.g., 

 Chtpea, Sprattus. Sardina. Engraulis) and the California current 

 (e.g., Sardinops, Etrumeus. Engraulis). The ontogeny of mor- 

 phology and behavior, and the requirements for growth and 

 survival of the herring, Cliipea harengus, and the anchovy, En- 

 graulis mordax, are well known (Blaxter and Hunter, 1982). 

 Very little detailed information exists for clupeids from species- 

 rich areas, especially western African freshwaters and the New 

 World tropics. Descriptive taxonomy is still needed in these 

 areas. Table 25 lists the clupeiform fishes for which we found 

 some information about eggs and larvae. 



Published descriptions of clupeoid eggs and larvae may not 



be adequate for systematic studies for a variety of reasons. When 

 there are few species in an area with which to confuse the de- 

 scribed species, only the key identifying features are described. 

 When eggs are hatched but the larvae are not reared to meta- 

 morphosis, usually an atypical starving early larva is described. 

 When a well-described series of field-caught larvae is compared 

 with a laboratory-reared series there may be differences in pig- 

 mentation and size at a particular stage of development due to 

 the rearing environment. Future descnptions should describe 

 the eggs and yolk-sac larvae thoroughly because these stages 

 have characters other than those such as meristics which, be- 

 cause they are shared with the adults, are redundant for system- 

 atic purposes. Future descriptions should also try to describe 

 the development of characters which are of phylogenetic im- 

 portance in adult-based classifications because the ontogenetic 

 transformation of a character provides information about the 

 polarity of states of that character (Nelson, 1978). 



Because the eggs and larvae of so many clupeiform genera are 

 undescribed and because existing descriptions vary in com- 

 pleteness, it is premature to attempt a phylogenetic classification 

 of the Clupeiformes based on early life history stages. However, 

 because many species' eggs and larvae have been described it 

 is possible to identify and describe characters of taxonomic and 

 phylogenetic value, to discuss their distribution among the Clu- 

 peiformes, and to point out some similarities and conflicts be- 

 tween the distribution of egg and larval characters and current 

 hypotheses of clupeiform phylogeny. 



Taxonomic characters of eggs and larvae 



The taxonomic characters of clupeoid eggs include size, shape, 

 chorion thickness and sculpturing, width of perivitelline space, 

 degree of yolk segmentation, number and size of oil globules if 

 present, whether they are pelagic or demersal, whether they are 

 adhesive or not, and whether they are spawned in fresh, brackish 

 or full seawater. 



The egg of Chirocentrus is 1.60-1.65 mm in diameter, has a 

 very small perivitelline space, is pelagic, spherical, and is abun- 

 dant near shore, especially around river mouths (Delsman, 

 1930b). The egg of Chirocentus nudus has a chorion with fine 

 hexagonal sculpturing (unique among clupeiforms) and up to 9 

 small oil globules, while the egg of C. dorab has a smooth cho- 

 rion and may have a single oil globule (Delsman, 1923, 1930b). 



The eggs of clupeids are all globular and they range in size 



