CRESSEY ET AL.: COPEPODS AND SCOMBRID FISHES 



specimens of Scomber scombrus with C. pelamydis 

 from Helgoland (these copepod identifications were 

 verified by G. Boxshall of the British Museum 

 (Natural History)). 



As the record shows, most species of copepods com- 

 mon on scombrid hosts are restricted to scombrids. 

 Caligus coryphaenae apparently is the only common 

 scombrid parasitic copepod whose host choice is in- 

 fluenced by ecological rather than phylogenetic 

 factors. 



There is evidence that in some cases the presence of 

 a species of parasitic copepod on two or more host 

 species which are not closely related may be the 

 result of an association between the hosts. The para- 

 sitic copepod Pumiliopes jonesi (= P. capitulatus) is 

 common on the eyes of scombrids of the tribe Scom- 

 brini {Rastrelliger and Scomber) and on the clupeids 

 Clupanodon punctatus and Herklotsichthys dis- 

 plonotus. Both groups are filter-feeding schooling 

 fishes. 



Another example is Caligus macaroui (= C. fulvipur- 

 pureus) common on the Pacific saury, Cololabis saira 

 (Hotta 1962), but reported on Auxis as well by 

 Gussev (1951). Cololabis feeds primarily on plank- 

 tonic crustaceans with eggs and larvae of fishes form- 

 ing secondary diet items (Hotta and Odate 1956; 

 Taka et al. 1980). Auxis feeds on a wide variety of 

 small fishes, cephalopods, and planktonic crus- 

 taceans (Uchida 1981). We are unaware of any rec- 

 ords of Auxis preying on Cololabis, but sauries are 

 common food items of billfishes. 



HOST SPECIFICITY 



Host specificity is concerned with the predilection 

 of a parasite species for one or a few species of host or 

 hosts. The comprehensive data on which this study is 

 based demonstrate host specificity. 



The occurrence of a species of parasite in a variety 

 of host species does not necessarily imply a lack of 

 host specificity. Careful analysis of collection data 

 with reference to percent of host individuals parasi- 

 tized by a particular parasite species will usually 

 show that one or a few host species are heavily infest- 

 ed, some occasionally infested, and some rarely in- 

 fested with the parasite species. Dogiel et al. (1961) 

 referred to these groups as main, secondary, and ac- 

 cidental hosts. Holmes (1979) referred to the three 

 groups as required hosts, suitable hosts, and unsuit- 

 able hosts. Holmes considered required and suitable 

 hosts as those with which the parasite can develop to 

 maturity (or to an infective stage in intermediate 

 hosts), and unsuitable hosts as those with which the 

 parasite cannot develop, but may be transported to a 



suitable or required host. Not enough is known of the 

 life histories of most parasitic copepods to evaluate 

 their state of "well being" on respective hosts. Col- 

 lection data, however, indicate that species found on 

 several host species vary in infestation rate in ways 

 suggesting the host categories of Dogiel et al. and 

 Holmes. In addition, unpublished data based on par- 

 asitic copepod collections by the first author from 

 fishes of the Gulf of Mexico indicate the same cate- 

 gories of infestation. 



The recently published revised data on the parasitic 

 copepods of scombrids (Cressey and Cressey 1980) 

 enable us to compare data based on a synoptic re- 

 view of literature records of copepods parasitic on 

 scombrids (Silas and Ummerkutty 1967) with a sur- 

 vey based solely on verified host and parasite iden- 

 tifications (Cressey and Cressey 1980). We have 

 used the same format as that of Holmes and Price 

 (1980) except we have considered specificity at the 

 generic level rather than the family level (our data are 

 based only on the Scombridae). 



Comparisons of the two analyses (Tables 3, 4) point 

 out the inadequacies of an unverified data base. Data 

 based on the literature survey of Silas and Ummer- 

 kutty (1967) indicate that 60% of the copepod spe- 

 cies parasitic on scombrids are specific to 1 genus, 

 5 % to 2 genera, 1 1 % to 3 or 4 genera, 2 % to 5 or more 

 genera, and 23% were also recorded from nonscom- 

 brid hosts. The data based on Cressey and Cressey 

 (1980) and additional records in this paper indicate 

 54% specific to 1 genus, 18% to 2 genera, 9% to 3 or 4 

 genera, 9% to 5 or more genera, and only 9% are also 

 found on nonscombrids. Clearly, the latter is a better 



TABLE 3.— Host specificity of scombrid copepods 

 based on data from Silas and Ummerkutty (1967). 



Table 4.— Host specificity of scombrid copepods 

 based on data from Cressey and Cressey (1980) and 

 later. 



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