FISHERY BULLETIN: VOL. 81, NO. 2 



la, b) are in the nasal sinuses and can only be collect- 

 ed by cutting open the nares; shiinoids (Fig. lc) are 

 firmly attached to lamellae of the nasal rosettes. 

 Other copepods, such as caligids, are not as firmly at- 

 tached, and many specimens are undoubtedly lost 

 during handling and preservation of the hosts. The 

 Scomberomorus species were represented by a rea- 

 sonable number of specimens with adequate size- 

 range coverage. 



The apparent optimum size for infestation by the 

 two species of pseudocycnids and the two bomolo- 

 chids is between 201 and 300 mm FL (fork length). 

 Infestations of Pseudocycnoides armatus and P. buc- 

 cata seem to remain at the same levels (about 2 per 

 fish) in groups with smaller and larger size in- 

 dividuals with about twice that infestation rate in the 

 optimum size range. Infestations of the bomolochids 

 Unicolax ciliatus (from S. commerson) and Holobo- 

 molochus divaricatus (from S. maculatus and S. 

 brasiliensis) apparently decrease with increased host 

 size after 300 mm FL; no Scomberomorus over 500 

 mm FL examined was parasitized by bomolochids. 

 The two species of Shiinoa (S. inauris horn Scomber- 

 omorus brasiliensis and S. maculatus and Shiinoa 

 occlusa from Scomberomorus commerson), on the 

 other hand, are not found on smaller fish, and the 

 greatest infestation rate occurs on fish over 400 

 mm FL. 



The change in infestation rate with host size in some 

 of these parasite species may be due primarily to 

 mechanical factors. In order for female pseudo- 

 cycnids to remain attached to the gill filaments, the 

 lateral lobes of the cephalon must partially encircle the 

 filament. Until a prospective host reaches an opti- 

 mum size, the filament may be too small for the adult 

 copepod to secure itself. As the host fish grows, the 

 filaments may become too large for the parasite to re- 

 main attached. Two very large S. commerson (1,115 

 and 1,150 mm FL) from New South Wales, Australia, 

 were parasitized by several P. armatus. These cope- 

 pods were considerably longer than average for the 

 species (8.1 vs. 4.9 mm), which may account for their 

 ability to infest a larger size host. Shiinoa attaches to 

 its host by piercing a nasal lamella with its recurved 

 second antennae which are opposed by an elongate 

 and recurved rostrum. The combination results in a 

 ring through the lamella, with the rest of the parasite 

 hanging free. It may be necessary for the host to at- 

 tain a minimum size (275 mm FL in our data) before 

 the lamella is large enough to accommodate the 

 parasite. (Shiinoa males attach to female copepods 



rather than the host.) 



The presence of bomolochid species on 100-200 mm 



hosts cannot be as easily correlated with mechanical 



230 



factors. Bomolochids are not firmly attached to their 

 hosts. Those species considered here are found loose 

 within the nasal sinuses and are capable of moving 

 about possibly as scavengers more than as true para- 

 sites. Possibly the reduction in infestation of bomo- 

 lochids in larger fish is associated with the increased 

 presence of Shiinoa in the nasal sinuses of hosts 

 larger than 300 mm. 



ECOLOGICAL RELATIONSHIPS 



To determine the influence of ecological relation- 

 ships as opposed to phylogenetic host specificity of 

 parasitic copepods found on scombrids, we examin- 

 ed the literature records of parasitic copepods from 

 fishes with habits similar to those of scombrids (large 

 size, open ocean, fast swimming, predatory, etc.). We 

 compiled data for the following fish groups: Billfishes 

 (Istiophoridae and Xiphiidae), sharks, A lepisaurus, 

 Lampris, Coryphaena, several genera of Carangidae, 

 Rachycentron, Pomatomus, and the gempylids, Ru- 

 vettus and Thyrsites. 



We have tried to use discretion in evaluating the 

 reliability of literature records. For example, Bere 

 (1936) reported Caligus bonito from Pomatomus sal- 

 tatrix, Lutjanus griseus, Mugil cephalus, Oligoplites 

 saurus, Scomberomorus maculatus, and S. cavalla. 

 She indicated in her report that the copepod material 

 was identified by C. B. Wilson. The first author of this 

 paper examined the specimens, deposited in the 

 Smithsonian (USNM 79090), in order to verify the 

 Pomatomus record. Bere presumably sent Wilson the 

 material separated by host. Wilson apparently put 

 together all specimens that he identified as a single 

 species. The collection contains about 15 Caligus 

 specimens with no host names and represents three 

 species — Caligus bonito, C. mutabilis, and males of a 

 third species. It is impossible to verify the occurrence 

 ofC. bonito onPomatomus, and the record must be ig- 

 nored. Another record (Capart 1959) of C. pelamy- 

 dis from Pomatomus is questionable because 

 Capart's illustration does not appear to be of C. pela- 

 mydis. Eliminating unreliable reports leaves C. cor- 

 yphaenae, a relatively distinct species, as the only 

 copepod common on scombrids which also occurs on 

 many ecologically similar species. It has been record- 

 ed from the following nonscombrid genera: Caranx, 

 Elagatis, Coryphaena, Xiphias, Squalus, Seriola, 

 Isurus,Echeneis, and Sphaeroides. There have been a 

 few reports of Caligus productus and C. pelamydis 

 from nonscombrid hosts, but both of these copepods 

 have been often confused with closely related spe- 

 cies. Rohde (1980) reported C. pelamydis from 3 of 

 88 specimens of Trachurus trachurus and 22 of 122 



