Beloniformes: Development and Relationships 

 B. B. CoLLETTE, G. E. McGowEN, N. V. Parin and S. Mito 



THE Beloniformes (or Synentognathi) is an order of atherino- 

 morph fishes containing five families. 37 genera, and about 

 180 species. Species of the Adrianichthyidae inhabit fresh and/ 

 or brackish waters. Most species of the other four families are 

 epipelagic marine fishes but several genera of Belonidae and 

 Hemiramphidae are restricted to fresh waters and a few other 

 genera contain estuarine and freshwater as well as marine species. 

 Two groups have been recognized under various names by a 

 series of authors starting with Schlesinger ( 1 909) and continuing 

 through Regan (1911b), Nichols and Breder (1928), Rosen ( 1 964), 

 and Collette (1966). Each of these groups contains two families, 

 the Scomberesocidae and Belonidae in the first, the Hemiram- 

 phidae and Exocoetidae in the second. Recently, Rosen and 

 Parenti (1981) expanded the Beloniformes by adding the Ad- 

 rianichthyidae to the order as a separate suborder Adrianichthy- 

 oidei, the sister group of the Exocoetoidei (containing two su- 

 perfamilies Scomberesocoidea and Exocoetoidea). 



Development 



Eggs 



Most beloniform fishes produce large spherical eggs with at- 

 taching filaments, characters they share with other atherino- 

 morph fishes (Rosen and Parenti, 1981). Adrianichthyid eggs 

 are the smallest (1.0-1.5 mm in diameter); followed by exo- 

 coetids (generally 1.5-2 mm); Hemiramphidae (typically 1.5- 

 2.5 mm); Scomberesocidae (slightly elliptical, 1 .5-2.5 mm); and 

 belonid eggs which are generally the largest (most 3-4 mm) 

 (Table 90). These eggs typically have a homogeneous yolk and 

 a relatively small perivitelline space. According to Kovalev- 

 skaya (1982), eggs with long filaments, distributed over the en- 



tire sphere of the egg (one filament may be thicker and longer 

 than the others) should be considered primitive. Such eggs are 

 found in the Belonidae, some Hemiramphidae, primitive flying- 

 fishes of the genera Fodialor and Parexocoetus. and also in many 

 of the highly specialized species of the subfamily Cypselurinae. 



Eggs of the Adrianichthyoidei contain numerous small oil 

 globules which coalesce, at least to some extent, during devel- 

 opment (Matsui. 1949), as in the Atheriniformes and Cyprino- 

 dontiformes (Rosen and Parenti, 1981). Exocoetoid eggs either 

 contain minute, scattered oil globules (Fig. 1 76C) or lack oil 

 globules (Table 90). 



Adrianichthyid eggs have filaments distributed over the entire 

 chorion, a condition we refer to as uniformly spaced. Most of 

 these filaments are short, 0.21-0.35 mm in Horaichthys setnai 

 (Kulkami, 1940), however, on one portion of the chorion they 

 are as long as or longer than the egg diameter (Fig. 1 72). Pietri 

 (1983) described these two topographically distinct types of fil- 

 aments from the chorionic surface of Oryzias latipes as non- 

 attaching and attaching. Non-attaching filaments showed a reg- 

 ular distribution over the chorion with an interfilament distance 

 of about 65-70 /im, and functioned to maintain the integrity of 

 the egg cluster. Attaching filaments were located at one pole of 

 the egg forming a clump of about 25 filaments that united with 

 those of neighboring eggs to anchor the egg cluster to the gon- 

 oduct of the female. In Oryzias melastigma, the attaching fil- 

 aments also anchor the eggs to the female (Job, 1940) or to 

 filamentous algae. 



The eggs of most scomberesocids {Scomberesox, Namchthys 

 and Elassichthys) are pelagic, without long filaments. Eggs of 

 Scomberesox (Fig. 1 73A), however, have short bristles that ap- 

 parently represent remnants of chorionic filaments (see Boehlert, 



Table 90. Eggs of Beloniformes Fishes. Much of this information is based entirely on illustrations from the cited references. 



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