CRESSEY ET AL.: COPEPODS AND SCOMBRID FISHES 



Indo- West Pacific through the eastern Atlantic to the 

 western Atlantic Ocean. It is replaced by two species 

 of bomolochids in the eastern Pacific — B. constrictus 

 and B. ensiculus. Unicolax ciliatus, the common 

 bomolochid of Scomberomorus, extends from the 

 Indo- West Pacific to the eastern Atlantic. It is re- 

 placed in the western Atlantic by H. divaricatus and 

 H. asperatus and in the eastern Pacific by H. nudi- 

 usculus. 



The gill parasites, Lernanthropus and Pseudocyc- 

 noides, show a similar pattern. The two species of 

 Lernanthropus, being circumglobal, extend farther 

 than Bomolochus does. Pseudocycnoides armatus is 

 found on species of Scomberomorus in the Indo-West 

 Pacific. It is replaced in the western Atlantic and 

 eastern Pacific by P. buccata. No Lernanthropus or 

 Pseudocycnoides were found on the single host 

 species of Strongylura and Scomberomorus in the 

 eastern Atlantic. 



Host specificity at the generic level depends on fac- 

 tors such as the number of species in a given host 

 genus, maximum body size of the host species, and 

 distribution of the host species. The most speciose 

 genera in each family (Scomberomorus with 18 of 47 

 species in the Scombrinae and Strongylura with 14 of 

 32 species in the Belonidae) have the most copepod 

 species, 50 and 857c, respectively, of the total para- 

 site fauna recorded for these two families (Table 1 1). 

 However, if one calculates a mean number of cope- 

 pod species per host species, a different picture em- 

 erges. In both fish families, monotypic genera, 

 including large pantropical species, contain the most 

 copepod species per host species, Acanthocybium 

 and Katsuwonus in the Scombridae with 6 of 46 

 species of copepods and Ablennes in the Belonidae 

 with 9 of 21. 



The genera with the next highest number of cope- 



pod species per host species are moderate-sized 

 species, Euthynnus (three species) with 3.7 copepod 

 species per host species in the Scombridae and 

 Platybelone (monotypic) with 7 of 21 in the Belo- 

 nidae. The three genera with the lowest number of 

 parasitic copepods per host species in the Belonidae 

 (0-0.5) are a special case, without parallel in the 

 Scombridae, small (4-28 cm body length) freshwater 

 South American species. No copepods were found on 

 the South African monotypic Petalichthys but only a 

 few host specimens were examined. 



ACKNOWLEDGMENTS 



Most of the copepod collections, which provide the 

 data on which this study is based, were reported in 

 Cressey and Cressey (1980). We reiterate our thanks 

 to the many scientists and staff of the institutions 

 cited in the earlier paper for making fish collections 

 available to us for study. Additional specimens of 

 Scombridae were examined in South Africa by the 

 second author through the assistance of Rudy van 

 der Elst (Oceanographic Research Institute, Dur- 

 ban), Philip Heemstra and Margaret M. Smith (J. L. 

 B. Smith Institute of Ichthyology, Grahamstown), 

 and P. A. Hulley (South African Museum, Cape- 

 town). M. A. A. Baker of the J. L. B. Smith Institute 

 recently loaned us a significant collection of South 

 African scombrid copepods, for which we are grate- 

 ful. Drafts of the manuscript were reviewed by Daniel 

 M. Brooks, Daniel M. Cohen, Robert H. Gibbs, Jr., 

 Ju-shey Ho, and Klaus Rohde. 



LITERATURE CITED 



Baudcm Laurencin, F. 



197 1. Crustacees et helminthes parasites de l'albacore (Thun- 



Table 11. — Number of parasitic copepod species per genus and maximum size of Belonidae and Scombridae. (Maximum size of belonid 



species given in cm body length and of scombrid species in cm fork length. 



261 



