COPEPODS AND NEEDLEFISHES: 

 A STUDY IN HOST-PARASITE RELATIONSHIPS 



BY ROGER F. CRESSEY' AND BRUCE B. COLLETTE,^ SYSTEMATIC ZOOLOGISTS 



ABSTRACT 



A survey of museum material of the species of needle- 

 fishes (Belonidae) found 3,863 copepods of 31 species 

 from 25 species of needlefishes. Twelve species of cope- 

 pods are described as new; one is included in a new 

 genus (Acu'icola) of Ergasilidae. The new species are: 

 Ergasilus spatulus, E. argulus, E. coleus, E. semicoleus, 

 E. inflatipes, Acusicola cunula, Paraergasilus remulus, 

 Parabomolochus ensiculus, P. cotistrictus, P. sinensis, 

 Nothobomolochus digitatus, and Colobomatus good- 

 ingi. In addition, 11 previously described species are 

 reported: Ergasilus orientalis Yamaguti, Acusicola 

 tenax (Roberts), Parabomolochus bellones (Burmeister), 

 Nothobomolochus gibber (Shiino), Caligus tylosuri 

 (Rangnekar), C. belones Kr0yer, C. malabaricus Pillai, 

 Caligodes laciniatus (Kr0yer), Lernanthropus belones 

 Kr0yer, L. tylosuri Richiardi, and Lernaeolophus sul- 

 tanus (Milne-Edwards). Eight additional species were 

 not named or described in detail because of insufficient 

 material. The copepod fauna of each species of needle- 

 fish is listed separately after the taxonomic descriptions 

 of the copepods. 



Eight questions regarding needlefishes and their cope- 

 pod parasites are considered: 



(1) Host specificity. The ergasilld and bomolochid 

 copepods show little host specificity; Caligodes 

 laciniatus, Lernanthropus belones, and L. tylo- 

 suri are restricted to certain groups of needle- 

 fishes. 



(2) Distributions. Maps of the ranges of the com- 

 mon species of copepods and their needlefish 

 hosts show general agreement; however, Colo- 

 bomatus goodingi is restricted to warmer waters 

 than its hosts. 



(3) Intraspecific variation in copepods. Total 

 lengths of female Caligodes laciniatus and Ler- 

 nanthropus belones were related to host species 



and geography, respectively. Lengths of setae 

 in Parabomolochus bellones also varied geo- 

 graphically rather than by host species. 



(4) Relative evolutionary rates. The four worldwide 

 species of needlefishes appear to be more highly 

 differentiated than the four worldwide species 

 of copepods. One widespread copepod, Parabo- 

 molochus bellones, has given rise to P. constric- 

 tus in the eastern Pacific, whereas the needlefish 

 hosts have differentiated to only the subspecific 

 level. 



(5) Effect of host size. Specialized copepods (those 

 possessing holdfasts) are attached to needle- 

 fishes of larger than average size; generalized 

 copepods that laclc these adaptations are found 

 on average-sized needlefishes. 



(6) Competition between copepods. Individual 

 needlefishes infested with several species of 

 copepods have copepods living in different eco- 

 logical niches on the host. Distributional evi- 

 dence indicates that the widespread Parabomo- 

 lochus bellones is being replaced in the Indo- 

 West Pacific by P. sinensis and two species of 

 Nothobomolochus. 



(7) Variation in infestation in time and space. The 

 relative infestation of Bahamian Strongylura 

 notata with Colobomatus goodingi seems to be 

 increasing. Geographic differences in infesta- 

 tion of widespread hosts were prominent in 

 Caligodes laciniatus, Lernanthropus tylosuri, 

 and Colobomatus goodingi. 



(8) Nature of the symbiotic relationship. The cope- 

 pods with holdfasts appear to be doing at least 

 mechanical damage to their hosts; the bomolo- 

 chids appear to be commensal or even mutual- 

 istic. 



This paper is a cooperative undertaking by a 

 specialist in a parasite group (Cressey) and one 

 in the host group (Collette). Misidentification of 



' U.S. National Museum Division of Crustacea, Washington. 

 D.C. 20560. 



- Bureau of Commercial Fisheries Systematica Laboratory, 

 Washington, D.C. 20560. 

 Published November 1&70. 



host animals has marred most past attempts of 

 parasitologists to analyze collection and literature 

 data. Identifications of hosts have rarely been au- 

 thoritative because only occasionally has a special- 

 ist for the hosts been consulted. We have not used 

 literature records in our analysis because the re- 

 sulting misidentifications in the literature cloud 



FISHERY BULLETIN: VOL. 68, NO. 3 



347 



