LEIS: TETRAODONTIFORMES 



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Table 1 18. Early Life History Characteristics of the Tetraodontiform Fishes. (P) indicates primitive, and (D) derived. (?) indicates 



assumed, (s) indicates that character is secondarily m state given. ( — ) indicates not applicable for family. See text for discussion of characteristics. 



(*) indicates character for which polarity cannot be established if the Zeiformes is considered the sister group of the Tetraodontiformes. 



specializations of the Tetraodontiformes. A dermal sac is con- 

 sidered derived (10a). A strongly inflated dermal sac (with a 

 large subdermal space) linking head and trunk in a ball-like unit 

 is considered a further derivation from the presence of a sac 

 (lOb). (II) Restriction of gill opening to a pore — In perciforms 

 with restricted gill openings (no zeiform fishes have restricted 

 gill openings), the opercles are fully open in early larvae and 

 gradually close to a pore. The assumed primitive condition in 

 Tetraodontiformes is for closure to a pore to occur after some 

 rays of the median fins have ossified (11a) because this is closest 

 to the perciform condition. Having the opening closed to a pore 

 at hatching is considered derived from closure at the end of the 

 yolk-sac stage (lib). (12) Scale development— The specialized 

 scales of adult tetraodontiform fishes form in two ways: directly 

 or by first passing through a relatively unspecialized spinule 

 stage. The intermediate spinule stage is considered primitive 

 because it is present in acanthurids and at least Capros in the 

 zeiforms. In acanthurids small spine-like scales change into tri- 

 angular scales arrayed in vertical rows, and these spine-like 

 scales form first on the lower gut and laterally on the head, in 

 the same place they first form in most tetraodontiform fishes 

 which have them. In Capros small spinules form prior to flexion 

 and eventually cover the whole body before differentiating into 

 scales. (13) Very large dermal spines (larval specialization)— 

 The ver>' large, fixed spines with conical or pyramidal bases of 

 molids are unique and are considered derived. ( 1 4) Preopercular 

 spinule cluster (larval specialization)— This cluster of spinules 



is unique to balistids and most monacanthids and is considered 

 a derived character. (15) Long notochord tip— The notochord 

 may extend well past the caudal fin aniage, and if so, following 

 flexion it will protrude dorsal and parallel to the caudal rays (to 

 about '/: their length) for a time. This condition was initially 

 considered derived because it is absent in acanthuroid fishes. 

 However, in the Tetraodontiformes the long notochord tip is 

 absent only in taxa in which the tail becomes greatly reduced 

 (i.e., Diodontidae, Ostraciidae, Molidae). Therefore, it seems 

 better to regard the long notochord tip as a primitive characler 

 within the order, but a character derived after the supposed split 

 from the acanthuroid fishes. The absence of this structure within 

 the order is thus derived. Zeiform larvae (Zeus. Capros) have 

 an elongate notochord tip very similar to that of balistoid fishes, 

 so this is considered the primitive condition. (16) Dorsal fin 

 spine development sequence— Dorsal fin spine development 

 prior to dorsal fin soft ray development is considered primitive 

 because this is the condition in acanthuroids and zeiforms. ( 1 7) 

 Dorsal fin spines— Acanthuroid fishes have 4 to 14 dorsal fin 

 spines, and zeiform fishes 5 to 10. Therefore, in the tetraodon- 

 tiform fishes, the most primitive character state is the greatest 

 number of spines (i.e., 4-6 of triacanthodids and triacanthids). 

 The intermediate derived condition is a reduction in this num- 

 ber to three spines ( 1 7a). From the intermediate condition are 

 derived one or two spines ( I 7b) and no spines ( I 7c). ( 1 8) Initial 

 formation of fin spines— The presence of dorsal fin spine aniage 

 and pelvic fin buds prior to flexion in fishes that have late- 



