CRESSEY ET AL.: COPEPODS AND SCOMBRID FISHES 



1979). Copepod fauna: 3 species in 2 genera, the 

 same species as in Orcynopsis plus Caligus asymmet- 

 ricus, which is found on various species in three of 

 the four tribes. 



Sarda Cuvier 



The four species of Sarda all have several dorsal 

 stripes, ranging from horizontal to oblique in orienta- 

 tion. Sarda and Gymnosarda share a number of char- 

 acters that distinguish them from Orcynopsis and 

 Cybiosarda (Collette and Chao 1975). 



Collette and Chao (1975) recognized four species of 

 Sarda (Fig. 8): Sarda australis (Macleay) is restricted 

 to the east coast of Australia, Norfolk Island, and 

 New Zealand; S. chiliensis inhabits the eastern Pa- 

 cific where it is divisible into two subspecies, S. c. 

 chiliensis (Cuvier) from Peru and Chile and S. c. lin- 

 eolata (Girard) from Alaska to Baja California; S. 

 orientalis (Temminck and Schlegel) is widespread in 

 the Indo-Pacific from South Africa and the Red Sea 

 east to Japan, China, the Philippine Islands, the 

 Hawaiian Islands, and across into the eastern Pacific 

 from Baja California to Peru; andS. sarda (Bloch) is 

 found throughout tropical and temperate waters of 

 the Atlantic Ocean including the Gulf of Mexico and 

 the Mediterranean and Black Seas (Collette and 

 Chao 1975; Fig. 8). 



A summary of the 26 most important characters 

 used in distinguishing the species of Sarda was pre- 

 sented by Collette and Chao (1975:table 17). 



Copepod fauna: 9 species in 3 genera. In addition to 

 the two widespread bonito parasites, U. collateralis 

 and Caligus bonito, three other copepods are com- 

 mon on species of Sarda; Ceratocolax euthynni, Cal- 

 igus pelamydis, andC. asymmetricus. The presence of 

 five common copepods on species of Sarda presents 

 an opportunity for further analysis. 



Over 200 specimens of the four species of Sarda 

 were examined with an overall infestation rate of 7 5 % 

 (156 of 206 specimens examined). It is thought that 

 as a host species or related group of host species dis- 

 perses from its place of origin it loses parasites in the 

 process (see discussion of Scomberomorus commer- 

 son above). When one examines the infestation rates 



of the individual Sarda species, first with all of its 

 copepod parasites and secondly each species with its 

 individual parasite species, the change in infestation 

 rates from one Sarda species to another may reflect 

 the speciation of Sarda species away from the center 

 of origin of the genus. 



An analysis of these data (Table 8) indicates an 

 origin of the genus in Australasia (S. australis, S. 

 orientalis, or an ancestor of theirs) with the eastern 

 Pacific S. chiliensis derived from S. australis and the 

 Atlantic S. sarda from S. chiliensis. The infestation 

 rates of C. bonito, C. asymmetricus, and U. collateralis 

 suggest that the copepod parasites of S. sarda could 

 have been derived from those of S. orientalis. The oc- 

 currence of C. pelamydis onS. sarda, however, and its 

 absence on S. orientalis reinforce the idea that S. 

 sarda may have been derived, along with its para- 

 sites, from S. australis or S. chiliensis but not from S. 

 orientalis. Sarda sarda has the lowest overall infesta- 

 tion rate (68%) and has lost one Caligus species 

 (asymmetricus) and replaced U. collateralis with the 

 Atlantic scombrid bomolochid copepod Ceratoco- 

 lax euthynni. 



The overall infestation rates of the four species of 

 Sarda are 8. australis, 90%; S. orientalis, 82%; S. chil- 

 iensis, 76%; and S. sarda, 68%. These data support 

 the proposal that species radiation progressed from 

 Indo- West Pacific to eastern Pacific to Atlantic with- 

 in the genus. 



The 26 morphological characters used by Collette 

 and Chao (1975:table 14) to distinguish the species 

 of Sarda tend to support the evolutionary hypothesis 

 deduced from the copepod data. Sarda sarda is the 

 most specialized of the four species in its increased 

 numbers of vertebrae and other correlated meristic 

 characters. Sarda australis appears most primitive in 

 such characters as number of dorsal and anal finlets. 

 It shares some primitive characters, such as the oc- 

 casional presence of vomerine teeth, with S. sarda. If 

 other similarities between these two species (loca- 

 tion of first closed haemal arch, length of haemal pre- 

 and postzygapophyses, shape of vertical wing of 

 pelvic girdle, etc.) can also be considered primitive, 

 then S. chiliensis and S. orientalis are in a relatively 

 intermediate evolutionary position. In some cases, 



Table 8. — Infestation rates by four species of copepods on the four species of 

 Sarda (arrows indicate direction of decrease). 



241 



