Sea lice (Copepoda: Caligidae) parasitic on fishes reported from the Neotropical region

The Caligidae, also known as sea lice, is a family of parasitic copepods of fish that consists of 31 genera and more than 450 species, some of which have been deleterious to cultured fish. The goal of this paper was to structure a list of sea lice species known from the Neotropical region based on information from published records. A total of 115 sea lice species found on 217 fish species were listed, including 58 species of Caligus and 22 of Lepeophtheirus. It seems that the inventory of this group of parasites is far from complete. Considering the promotion of finfish sea-cage aquaculture throughout the coastal areas of Latin America, a better understanding of the sea lice biodiversity will support systematic work on parasitic copepods in the Neotropics and will provide fundamental information that could impact fish disease control and prevention strategies.


Lepeophtheirus salmonis
In Neotropical marine fishes, copepods represent the second largest parasitic group. [6] However, the description of sea lice biodiversity has been given at slow pace, with isolate records of known species or descriptions of new species. In some cases, it may be difficult to access to scattered, past literature. Therefore, in the present work we provide a list of sea lice species that parasitize fish from the Neotropical region (Caribbean, Central and South America) as reference point for further studies into taxonomy, ecology, and other aspects of this interesting group of parasites.

Material and methods
The list of species herein presented is updated until March 2015, and contains records found in previous literature which was gathered by browsing in Zoological Record, Google Scholar and Scopus using search terms 'Caligidae', 'caligid', 'Caligus', 'Lepeophtheirus', 'sea lice', 'parasitic copepod', 'parasitic crustacean', combined with the name of a particular geographical region (e.g. 'Neotropics', 'Brazil', 'Colombia', 'Ecuador', 'Eastern Pacific'), including the Spanish translation of these terms. Records in Ho & Lin's book were also checked. [7] Genera and species are ordered alphabetically following the classification and systematics of Walter & Boxshall. [2] For each sea lice species, the name, authority, fish host species, locality and references are presented. Fish names follow FishBase. [8]

Results
In the present work, 115 species (including 19 unidentified species) of sea lice (Appendix 1) found on 217 fish species are listed. Of these, 58 are known species of Caligus and 22 of Lepeophtheirus. The remaining species are distributed in nine genera (Alebion, Anuretes, Caligodes, Euryphorus, Gloiopotes, Lepeophtheirus, Metacaligus, Parapetalus and Tuxophorus). The sea lice species with the widest host range were Caligus mutabilis , C. productus Dana, 1852, and C. rufimaculatus Wilson, 1905  The fish host species harbouring more sea lice species were Lutjanus argentiventris (8), Caranx caballus (7), and Scomberomorus sp. (7). Mexico, Brazil, and Chile were the countries with the major number of records of sea lice species (48, 36, and 23 species, respectively).

Discussion
According to the list provided in this paper, Caligus is currently the dominant caligid genus found in Neotropical marine and brackish water fishes. It is in agreement with the fact that species of Caligus are mostly found on warm water fishes in contrast with Lepeophtheirus diversity which tends to be low in tropical areas. [7,9] As far as we know, specific evolutionary or ecological mechanisms underlying this dominance of Caligus are not well understood. Morphologically, species of both genera are similar, the main distinguishing feature is the pair of lunules (sucker-like supplementary attachment organs on the frontal plates) present in Caligus and absent in Lepeophtheirus. [10,11] However, lunules are also present in other genera of the Caligidae. There is some evidence pointing out that species of Caligus are more active swimmers and transfer more frequently between hosts than species of Lepeophtheirus (see discussion in [12]). Such swimming ability would enable diversification in species of Caligus driven by dispersal and hostswitching. According to Hoberg and Brooks [13], in Earth's history, the major radiations in host-parasite assemblages have been preceded by ecological disruption, ecological breakdown and host-switching.
Even though sea lice are generally host specific, there are some species able to parasitize various hosts. [10] In the Neotropics, C. mutabilis appears to have the widest host range, including Atlantic and Pacific hosts. This species was originally described by Wilson in 1905,[14] and then redescribed by Cressey and Cressey [15]. It seems that C. mutabilis has intraspecific variation at least in the shape of the genital complex [14] and the length of the setae on the exopod of leg four, [15] but this issue has not been clearly addressed. In a recent phylogenetic analysis of sea lice species based on mtDNA sequences, [16] the group formed by C. mutabilis isolates showed a relatively high intraspecific genetic divergence. Therefore, it is necessary to perform a study to determine the extent of morphological and genetic variation within this species.
The present report includes sea lice species that have been found free-swimming. The occurrence of adults and juvenile stages of caligiform copepods in plankton samples has not been rare. There are species (e.g. C. undulatus) with a wide geographical distribution and that have yet to be reported from a fish host. [17] The large geographical range reached by some sea lice species (i.e. C. productus, C. bonito, and C. coryphaenae) in the Neotropics is comprehensible considering that some of their fish hosts (e.g. Coryphaena hippurus, Katsuwonus pelamis, Mugil cephalus, Thunnus albacares and Thunnus obesus) are distributed in tropical and subtropical seas throughout the world.
The present work, to some extent, provides evidence of the limited knowledge on the sea lice biodiversity in several Latin American countries. The number of species could be significantly higher than reported herein. For instance, a recent survey performed in one single locality of Ecuador uncovered 22 species of Caligus and 5 of Lepeophtheirus, most of which were new records to this country. [18] This situation is not only true for parasitic copepods. According to Luque and Poulin [6], our knowledge of the parasite biodiversity of Latin American fishes is in its infancy, the distribution of the study effort has been quite heterogeneous and the majority of known fish species have not been examined for parasites.
The threat of sea lice for farmed fish should not be minimized. In terms of aquaculture and fish health, the appropriate knowledge of the parasite fauna could be useful to improve diagnosis, control and management of parasitic diseases, as well as more detailed research in the future.

Disclosure statement
No potential conflict of interest was reported by the authors.  Wilson, 1937 Chanos chanos Panama [7] (Continued)