448 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Table 1 14, Tetraodontoid Taxa for whk h Information is Available on Egg and Larval Stages. YS — yolk-sac stage; pre — preflexion 



stage; flex — flexion stage; post — postflexion stage; U — unstated; den- demersal; pel — pelagic; PS— examined for the present study. Numbers in 



parentheses after each genus refer to the number of species represented. A blank means no information available on that stage. 



Eggs 



Larvae 

 developmental stage 



Type 



Oil 

 droplets 



Diodon (3) 



Tragiilichlhys ( 1 ) 

 Molidae- 

 Masliirus ( 1 ) 

 Mola ( 1 ) 

 Ranzania ( 1 ) 



pel 



1.62-2.1 



cluster 



pel 1.8 cluster 



pel 1.42-1.68 cluster 



X Fujita, 1962; Stroud et al., MS; PS 



Breder and Rosen, 1966 



Breder and Rosen, 1966 



Roberts, 1982a 

 X Uchida et al., 1958; Mito, 1966; Masuda et 



al., 1975; Fujita. 1962 

 X Uchida et al., 1958; Fujita, 1962. 1966 



X Welsh and Breder. 1921 



Breder and Rosen, 1 966 

 X Munro, 1945 



X Miller et al., 1979; Leis and Rcnnis. 1983; 



PS 



Robertson, 1975a 



Evermann and Kendall, 1898; Breder, 1927; 

 Nichols and Breder, 1927; Fowler, 1945; 

 Breder and Clark, 1947; Heck and Wein- 

 stein, 1978; Moyer, pers. comm.; Fujita. 

 1962; PS 



Sanzo, 1930d'; Mito. 1966; Leis, 1978; Sak- 

 amoto and Suzuki, 1978; Fujita, 1962; PS 



PS 



X Schmidt, 1921; Martin and Drewry, 1978 



X Martin and Drewry, 1978 



X Schmidt, 1921; Leis. 1977 



' Misideniified as Crayracion sp. (Tetraodontidae). 



 No caudal fin forms: pre, fiex and post in this case refer to clavus formation, not notochord lleMon, 



£gg.j.— Tetraodontoid fishes are oviparous. Pelagic and demer- 

 sal eggs are known; the chorion is smooth; clusters of oil droplets 

 are present; eggs range in size from large (2. 1 mm) to small (0.6 

 mm) and are spherical; incubation times are long and range 

 from 3 to 20 days; development at hatching varies; the peri- 

 vitelline space is narrow; the yolk is unsegmented; and embryos 

 may be heavily pigmented. Parental care of eggs is present only 

 in some tetraodontids. 



Larvae. — M\ tetraodontoid larvae are pelagic. Development in 

 most tetraodontids is direct; in molids and diodontids special- 

 ized ontogenetic stages may exist. There are few larval special- 

 izations except in the Molidae, and development is usually com- 

 pleted at a small size. There is often an apparently unspecialized 

 pelagic juvenile stage, which may be very large at settlement. 

 Larvae are enclosed in a more or less inflated vesicular sac. 

 Larvae are deep and wide in head and trunk, and the tail is 

 comparatively small and compressed. The head is large and 

 rounded and the gut is coiled and massive. The eye is partic- 

 ularly large. The specialized adult scales form directly (i.e., do 

 not pass through an unspecialized spinule stage). In molids spe- 

 cialized larval spines are formed. The pectoral fin is the first to 

 form, and the caudal fin is last. Except for the tail of molids, 

 structures are not formed and subsequently lost — they never 

 form. The specialized dentition develops during the larval stage 

 directly, without any intervening generalized teeth. However, 

 diodontids and tetraodontids may have small, raised points 



along the cutting edges of their beak-like teeth. Meristic char- 

 acters are summarized in Table 1 1 3 [see Tyler ( 1 980) for further 

 information]. The number of vertebrae is low ( 16-30), as is the 

 number of caudal fin rays (0-12). Pelvic fins arc lacking and 

 except for some triodontids. the fins lack spines. Larvae are 

 heavily pigmented. The few larval specializations which do oc- 

 cur are the vesicular dermal sac of all species and the huge 

 dermal spines of molids. 



Only two groups have specialized ontogenetic stages between 

 larvae and juveniles. In the Diodontidae, some Atlantic species 

 of Chilomycterus (sensu lato) have a postflexion stage {"Lyo- 

 sphaera") that lacks dermal spines, but has fleshy protuberences 

 in the locations the spines will occupy and other enlarged pro- 

 tuberences unassociated with spines (Evermann and Kendall, 

 1898; Breder, 1927; Heck and Weinstein, 1978). In the Molidae, 

 Mola and Mastwus have a deep-bodied, compressed stage 

 ("Molacanlhus") that has reduced larval spines, and a distinctly 

 non-adult shape (Martin and Drewry, 1978). 



Family Accounts 

 Triodontidae. — 'Ho\.hm% is known of triodontid eggs or larvae. 



Tetraodontidae. — Tetraodontid eggs are demersal, small to me- 

 dium-sized, have multiple oil droplets (Table 1 14) and hatch 

 in 3-20 days. The very large ovarian eggs of Chonerhinos (Table 

 1 14), a highly specialized freshwater genus (Tyler, 1980; Rob- 

 erts, 1982a), are here regarded as a specialization for freshwater 



