Ergasilus chelangulatus sp. nov. (Copepoda: Ergasilidae) a branchial parasite of the freshwater catfish, Pimelodus maculatus from the upper São Francisco River, Brazil

Ergasilus chelangulatus sp. nov. (Copepoda: Ergasilidae) parasito das brânquias do "mandi", Pimelodus maculatus do alto rio São Francisco, Brasil

TAXONOMY AND NOMENCLATURE

Ergasilus chelangulatus sp. nov. (Copepoda: Ergasilidae) a branchial parasite of the freshwater catfish, Pimelodus maculatus from the upper São Francisco River, Brazil¹

Ergasilus chelangulatus sp. nov. (Copepoda: Ergasilidae) parasito das brânquias do "mandi", Pimelodus maculatus do alto rio São Francisco, Brasil

Vernon E. Thatcher^I; Marilia C. Brasil-Sato^II

^IDepartamento de Zoologia, Universidade Federal do Paraná. Caixa Postal 19020, 81531-980 Curitiba, Paraná, Brasil. E-mail: [e-mail]

^IIDepartamento de Biologia Animal, Universidade Federal Rural do Rio de Janeiro. Rodovia BR 465, km 7, Caixa Postal 74539, 23851-970 Seropédica, Rio de Janeiro, Brasil. E-mail: [e-mail]

ABSTRACT

Ergasilus chelangulatussp. nov. is described from the freshwater fish, Pimelodus maculatus Lacépède, 1803 (Siluriformes: Pimelodidae) of the upper São Francisco River, Minas Gerais State, Brazil. The new species is based on female specimens and the male is unknown. This species has a serrate seta on exopod one and a two-segmented first endopod, as do most Amazonian species of this genus. The body is elongate and produced anteriorly. The antennae are elongate and have prominent sensilla on segments two and three. Ergasilus chelangulatus sp. nov. can be distinguished from all known species of Ergasilus by the fourth antennal segment (claw) which is bent at nearly a right angle.

Key words: Catfish parasite; copepod parasite; freshwater fish; South America.

RESUMO

Ergasilus chelangulatussp. nov. é descrita do peixe de água doce, Pimelodus maculatus Lacépède, 1803 (Siluriformes: Pimelodidae) do alto rio São Francisco, Minas Gerais, Brasil. A nova espécie está baseada em espécimes fêmeas e o macho é desconhecido. Esta espécie tem uma seta serrilhada no primeiro exopodito e tem o primeiro endopodito bi-segmentado, como a maioria das espécies amazônicas deste gênero. O corpo é alongado e projetado anteriormente. As antenas são alongadas com sensila proeminente no segundo e no terceiro segmentos. Ergasilus chelangulatus sp. nov. é distinta de todas as outras espécies conhecidas de Ergasilus por ter o quarto segmento antenal (garra) dobrado em ângulo quase reto.

Palavras-chave: América do Sul; copépodes parasitos; parasitos de siluriformes; peixes de água doce.

Species of Ergasilus are found world-wide and are considered to be one of the plagues of pisciculture. Only the females are found on fish hosts while the males are free-living in the zooplankton. Most species are found on freshwater fishes but a few infect marine fishes of the litoral. YAMAGUTI (1963) reported 69 species of this genus world-wide. HOFFMAN (1998) listed 32 species for North America and THATCHER (2006) cited 15 species of Ergasilus from South America (most from the Amazon region). The present paper describes the second species of the genus known from the São Francisco River of Minas Gerais State, Brazil.

MATERIAL AND METHODS

Fish hosts were captured with nets in the upper São Francisco River in the municipality of Três Marias, Minas Gerais State, Brazil. Copepod parasites were removed from the gill filaments with dissecting needles and fixed in 70% alcohol. They were transported to a laboratory of the Universidade Federal do Paraná, Curitiba, Paraná, where permanent slide preparations were made using the phenol-balsam method explained in THATCHER (2006). Digital photographs made through a light microscope were used to make the drawings. Measurements were made utilizing a measuring ocular and are expressed in micrometers.

RESULTS

Ergasilus chelangulatus sp. nov.

Figs 1-9

Species diagnosis (based on 10 females studied and measured; measurements in tables I and ^II). Body elongate, tapered towards both extremities and projecting anteriorly; head incompletely fused to first thoracic segment; first and second thoracic segments completely fused (Fig. 1). Thorax of five free segments, including genital segment (Figs 1 and 4). Ventral pigment granules centrally located from eye to genital segment. Eye cobalt blue – color 168 of Smithe (1975); body, indigo blue – color 173 of SMITHE (1975). Abdomen (Fig. 4) of three segments; segment two shortest of three. Uropod with two elongate caudal filaments. Antennule (Fig. 7) of six articles, provided with simple setae. Antenna (Fig. 2) of four segments (including claw); prominent sensilla on segments two and three; claw bent to nearly a right angle. Mouthparts (Fig. 8). Mandible with posteriorly directed terminal bristles; palp denticulate posteriorly. Maxilla terminally bristled; maxillule not observed. Legs (Figs 5, 6 and 9). Leg 1 (Fig. 5) endopod two-segmented, exopod three segmented; first endopodal segment with a single pinnate medial seta; terminal endopodal segment with two stout spines and five pinnate medial setae; first exopodal segment with a single postero-lateral spine; second exopodal segment with a single pinnate medial seta; terminal segment with four medial pinnate seta, one curved serate seta and two terminal spines. Leg 2 and leg 3 (Fig. 6) both rami three-segmented; first endopodal segment without spines and setae; second endopodal segment with two medial pinnate setae; terminal segment with four small pinnate setae and one small spine; first exopodal segment with one small lateral spine; second segment without spines and setae; terminal segment with six pinnate setae and one small spine. Leg 4 (Fig. 9) both rami two-segmented; first endopodal segment without spines and setae; terminal segment with five pinnate setae and one spine; first exopodal segment without spines and setae; terminal segment with five pinnate setae and one spine. Egg sac elongate with few rows of eggs.

Type host: Pimelodus maculatus Lacépède, 1803.

Site of infestation: Gill filaments.

Male: Unknown

Type locality: São Francisco River, downstream from the Três Marias Dam (18º12'32"S, 45º15"41"W), State of Minas Gerais, Brazil.

Type specimens: Holotype female and nine paratype females on permanent slides were deposited in the Crustacea Collection of the Instituto Nacional de Pesquisas da Amazonia, Manaus, Amazonas, Brazil.

Etymology: The specific name is in reference to the bent claw (chel = claw and angulatus = angled).

DISCUSSION

Ergasilus chelangulatussp. nov. is not closely similar to any known species. It has a curved, serrate seta on the first exopod and a two-segmented first endopod as do most known Amazonian species. The new species bears a superficial resemblance to Ergasilus cerastes Roberts, 1969, from North American catfishes, and to Ergasilus pitalicus Thatcher, 1984, from Colombian cichlids in that these have similar sensilla and two-segmented first endopods. Both of the latter have three-segmented fourth endopods, however, while the new species has only two segments in that structure. The other two species also lack a curved, serrate seta on the first exopod. Ergasilus chelangulatus sp. nov. can be distinguished at a glance from all other known species in the genus by the form of the fourth antennal segment (claw) which is bent into a nearly right angle.

ACKNOWLEDGEMENTS

Thanks to Yoshimi Sato, Leader of the Estação de Hidrobiologia e Piscicultura da CODEVASF, Três Marias, Minas Gerais, for his assistance during this research and to CEMIG/CODEVASF for logistical and material support.

LITERATURE CITED

Submitted: 18.II.2008; Accepted: 01.IX.2008.

Editorial responsibility: Marcus V. Domingues

• HOFFMAN, G.L. 1998. Parasites of North American Freshwater Fishes (Second Edition). Ithaca, Cornell University Press, 539p.
• SMITHE, F.B. 1975. Naturalist's Color Guide and Supplement. New York, American Museum of Natural History, 229p.
• THATCHER, V.E. 2006. Amazon Fish Parasites (Second Edition). Sofia, Pensoft Publishers, 508p.
• YAMAGUTI, S. 1963. Parasitic Copepoda and Branchiura of Fishes. New York, Interscience Publishers, 1104p.

1

Contribution number 1761 of the Departamento de Zoologia, Universidade Federal do Paraná

Publication Dates

• Publication in this collection
  16 Oct 2008
• Date of issue
  Sept 2008