FISHERY BULLETIN: VOL. 81, NO. 2 



3. S comber omorus niphonius is possibly the most 

 primitive species of the genus based on Caligus and 

 other copepod parasites (Pseudocycnoides scomber- 

 omori, a copepod specific to <S. niphonius, is more 

 primitive than P. armatus found on several other 

 Indo-West Pacific Scomberomorus). 



Scombrid Phylogeny 



Historic 



Many workers have arranged the scombrids accord- 

 ing to their ideas of relationships within the group. In 

 this section we present a brief history of scombrid 

 classifications, culminating in the most recently pub- 

 lished article by Collette and Russo (1979). Then we 

 present a classification derived from infestation by 

 parasitic copepods and discuss differences between 

 the two classifications. 



Modern attempts at classification of the scombrid 

 fishes date from Regan (1909), who placed the family 

 Scombridae as the sole member of a division Scom- 

 briformes in the suborder Scombroidei of the order 

 Percomorphi. Starks (1910) was the first to define 

 subdivisions within the family recognizing five sub- 

 families: Scombrinae, Scomberomorinae, Acantho- 

 cybinae, Sardinae, and Thunninae (Fig. 13). Starks 

 based his classification on osteology. Characters 

 from soft anatomy, particularly the viscera and the 

 circulatory system, were added by Kishinouye (in 

 particular, his classic 1923 monograph). Kishinouye 



was so impressed by the differences that he separat- 

 ed the most advanced scombrids as a separate order, 

 Plecostei, with two families, the Thunidae (Thunnus) 

 and the Katsuwonidae (Auxis, Euthynnus, and Kat- 

 suwonus). Rather illogically, he left the other scom- 

 brids as two families, Scombridae (Scomber and 

 Rastrelliger) and Cybiidae (all the bonitos and seer- 

 fishes) of the Teleostei, suborder Acanthopterygii 

 (Fig. 14). The next revisor of the family, Fraser- 

 Brunner (1950) overreacted to this splitting of the 

 scombrids into four families in two orders by ignoring 

 the anatomical data in constructing his classification 

 (Fig. 15). The most recent classification of the scom- 

 brids (Collette and Russo 1979) has been slightly 

 revised for presentation here (Fig. 16). 



Parasite Based 



Once a host-parasite relationship has been estab- 

 lished, several events can occur with respect to the 

 evolution of this relationship. Assuming the host will 

 evolve and allowing for speciation, the parasite may 

 gradually change maintaining compatability with its 

 changing host or the parasite may be divided into 

 separate populations because of a speciation event in 

 the host. In the former case, there is no speciation 

 event in the host, thus a single parasite population 

 would remain sympatric. In the latter case, the spe- 

 ciation event in the host would divide the parasite 

 population into two allopatric populations and act as 

 a vicariant event with respect to the parasites. The 



RASTBELLLGEft 



SCOMBER 



FIGURE 13.— Diagram of relationships of the Scombridae from Starks (1910). A) Characters of Scomber. B) Acquirement of interposed 

 opisthotics. C) Thunnus type of cranial crests, and the inferior cranial pit indicated, with the Scomberomorus type of ethmoid and nasals. D) 

 The inferior cranial pit excluding the pterotic from the brain cavity, and the condition of the ethmoid and nasals of Scomber. E) The condition 

 of the infravertebral processes from which Auju.s andEuthynnus (given as Gymnosarda by Starks 1910) have diverged. F) The: Scomberomorus 

 type of cranial crests, elongate form, concave ethmoid, and nonprojecting nasals. 



252 



