Memórias do Instituto Oswaldo Cruz Fundação Oswaldo Cruz, Fiocruz ISSN: 1678-8060 EISSN: 1678-8060 Vol. 90, Num. 6, 1995, pp. 699-702

Memorias do Instituto Oswaldo Cruz
Vol. 90(6), Nov./Dec. 1995

Neotropical Monogenoidea. 25. Anacanthorus penilabiatus n. sp.(Dactylogyridae, Anacanthorinae) from Piaractus mesopotamicus (Osteichthyes, Serrasalmidae), Cultivated in the State of Sao Paulo, Brazil

Walter A Boeger/+, Wanda S Husak/+, Mauricio L Martins*

Departamento de Zoologia, Universidade Federal do Parana, 81531-990 Curitiba, PR, Brasil * Centro de Aquicultura, Universidade Estadual Paulista, 14870-000 Jaboticabal, SP, Brasil

Code Number: OC95142
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Anacanthorus penilabiatus n. sp. is described from the serrasalmid fish, Piaractus mesopotamicus (Holmberg, 1887), cultivated in the Centro de Aquicultura, Universidade Estadual Paulista. The new species is characterized by having a relatively straight copulatory organ with a long olipo on the distal margin and a median longitudinal flap, and a copulatory ligament. The large size of the infrapopulations of this species of parasite indicates that it should be considered a potential agent causing losses in aquaculture of the fish host.

Key words: Anacanthorus penilabiatus n. sp. - Piaractus mesopotamicus - aquaculture

Anacanthorus is a diverse taxon of monogenoidean parasites from the gill filaments of Characiformes fishes. A list of all presently known species of Anacanthorus is presented by Van Every and Kritsky (1992). While most of these species are abundant in fish collected in their natural habitat, some have been collected from several species of fish cultivated in experimental and private piscicultures. In these artificial settings, Anacanthorus spp. frequently reach large populational numbers, suggesting that they may represent a potential harzad to productivity.

During a study of parasites of Piaractus mesopotamicus (Holmberg 1887) by the third author, large numbers of an undescribed species of Anacanthorus were collected from the gills. This species is described and illustrated herein.

MATERIALS AND METHODS

Twelve pacus (P. mesopotamicus), measuring 20 +/- 2 cm of standard length, were collected by MLM from experimental tanks (49 m^3) of the Centro de Aquicultura, Universidade Estadual Paulista, Jaboticabal, State of Sao Paulo, Brazil, in 18/XII/1992. Methods of parasite collection, preparation, measurement, and illustration are as described by Kritsky et al. (1986). Measurements are in micrometers; average is followed by ranges in parentheses. Type specimens are deposited in helminthological collections of the Instituto Oswaldo Cruz (IOC), Rio de Janeiro, Brazil; U.S. National Museum (USNM), Beltsville, Maryland; and the University of Nebraska State Museum (HWML), Lincoln, Nebraska.

Description

Anacanthorus penilabiatus n. sp.

Figs 1-4

Type host: Piaractus mesopotamicus (Holmberg, 1887)

Type locality: Centro de Aquicultura, Universidade Estadual Paulista, Jaboticabal, State of São Paulo, Brazil, 18/XII/92

Type specimens: Holotype: IOC 33268 a. Paratypes, IOC 33268 b-j (9 specimens), USNM 84480 (10 specimens), HWML 38024

Intensity of infestation: up to 1713 specimens/fish.

Description (based on 46 specimens): body 732 (560-894; n=20) long; greatest width 112 (91-136; n=20). Cephalic lobes well developed. Two pairs of eyes, anterior pair smaller, slightly closer together than posterior pair, eye granules subovate; accessory granules absent. Pharynx sub-spherical, 38 (34-43; n=20) in diameter. Haptor 68 (45-90; n=20) long, 121 (91-167; n=20) wide, slightly bilobed. Hooks similar, each with truncate slightly depressed thumb, shank with variable enlargment on proximal end; hooks 31 (27-40; n=20) long, FH loop about 0.5 shank length; 4A's similar, each 17 (16-19; n=20) long, proximally expanded about 2/3 length. Gonads tandem; testis postovarian, 124 (97-198; n=20) long, 38 (31-62; n=20) wide; germarium 49 (36-62; n=20) long, 29 (16-41; n=20) wide. Prostatic reservoir large, subovate. Copulatory organ, accessory piece articulated by copulatory ligament. Copulatory organ 98 (87-119; n=20) long, oblique base, longitudinal flap near midlength, subterminal aperture with long, posteriorly recurved lip. Accessory piece 54 (47-62; n=20) long, rod shaped, distally spatulated with subterminal pointed projection, proximal end slightly expanded articulated to copulatory ligament. Copulatory ligament thin, flexible, wider that accessory piece.

REMARKS

Anacanthorus penilabiatus n. sp. is apparently related to the species depicting a copulatory ligament, which articulates the male copulatory organ and accessory piece, and a straight copulatory organ. Among these species, the new species depicts greater similarity to A. spatulathus Kritsky and Thatcher, 1979, from Colossoma macro-pomum (Cuvier) and C. bidens (Spix), and A. paraspathulatus Kritsky, Boeger and Van Every, 1992, from Mylossoma duriventris (Cuvier), as indicated by the general morphology of the copulatory complex and hooks. However, A. penilabiatus can be easily differentiated from these species by having: 1. a longer "lip" on the distal aperture of the copulatory organ; 2. a median, longitudinal flap on the copulatory organ; 3. a strongly flattened, spathulated distal portion of the accessory piece - in A. spathulatus this portion is much less flattened and closely resembles an "ice-cream scoop" and in A. paraspathulatus it is pointed and rod shaped.

The specific epithet is derived from Latin and refers to the morphology of the aperture of the cirrus, with long, recurved lip ("peni"=a penis; "labi"=a lip).

Although Van Every and Kritsky (1992) predicted that the species of Anacanthorus from Piaractus would likely depict an articulated copulatory complex (with copulatory ligament) and a copulatory organ with the tendency to curl, this is not what has been observed for A. penilabiatus. The new species, thus, do not fall into the ingroup analyzed by these authors in their phylogenetic analysis of the Anacanthorus from species of three serrasalmid genera. Copulatory complexes with the same general morphology as A. penilabiatus are found in many species of Anacanthorus parasitizing not only members of Myleinae but also members of several other families of Characiformes (see Kritsky et al. 1992). Thus, an articulated accessory piece with a somewhat straight copulatory organ is symplesiomorphic for the group of Anacanthorus of Serrasalmidae fishes. Although we expect all Anacanthorus spp. from Serrasalmidae to represent a monophyletic group, the determination of supporting synapomorphies must wait phylogenetic analysis.

There have been unpublished reports of large mortalities of "pacus", P. mesopotamicus, in Brazilian fish farms. Although the hosts of the specimens utilized in this study did not show any conspicuous sign of compromised health, the large infrapopulational numbers of this parasite species encountered suggests that it should be seriously considered in any scruitiny for agents causing these mortalities or other economical losses in aquaculture of this fish species.

ACKNOWLEDGEMENTS

To Dr Delane C Kritsky, Idaho State University, USA, for providing a presubmission review of the manuscript.

REFERENCES

Kritsky DC, Boeger WA, Van Every LR 1992. Neotropical Monogenoidea. 17. Anacanthorus Mizelle and Price, 1965 (Dactylogyridae, Anacanthorinae) from Characoid fishes of the Central Amazon. J helm Soc Wash 59: 25-51.

Kritsky DC, Thatcher VE, Boeger WA 1986. Neotropical Monogenea. 8. Revision of Urocleidoides (Dactylogyridae, Ancyrocephalinae). Proc helm Soc Wash 53: 1-37.

Van Every LR, Kritsky DC 1992. Neotropical Monogenoidea. 18. Anacanthorus Mizelle and Price, 1965 (Dactylogyridae, Anacanthorinae) of Piranha (Characoidea, Serrasalmidae) from the Central Amazon, their Phylogeny, and Aspects of Host-Parasite Coevolution. J helm Soc Wash 59: 52-75.

This work received financial support from the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq). This is the contribution number 884 from the Departamento de Zoologia, Universidade Federal do Parana.

+Research fellows CNPq
Received 13 December 1994
Accepted 12 April 1995

Copyright 1995 Fundacao Oswaldo Cruz, FIOCRUZ

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