Expanded description of Dolops bidentata (Bouvier, 1899) (Branchiura: Argulidae) based on specimens collected on Pygocentrus nattereri Kner, 1858 (Characiformes) from Poconé Wetland, MT, Brazil

Descrição expandida de Dolops bidentata (Bouvier, 1899) (Branchiura: Argulidae) baseada em espécimes parasitos de Pygocentrus nattereri Kner, 1858 (Characiformes) do Pantanal de Poconé, MT, Brasil

BIOLOGY

Expanded description of Dolops bidentata (Bouvier, 1899) (Branchiura: Argulidae) based on specimens collected on Pygocentrus nattereri Kner, 1858 (Characiformes) from Poconé Wetland, MT, Brazil

Descrição expandida de Dolops bidentata (Bouvier, 1899) (Branchiura: Argulidae) baseada em espécimes parasitos de Pygocentrus nattereri Kner, 1858 (Characiformes) do Pantanal de Poconé, MT, Brasil

Silva-Souza, AT.I, ^*; Abdallah, VD.^II; de Azevedo, RK.^II; da Silva, FA.^III; Luque, JL.^II

^IDepartamento de Biologia Animal e Vegetal - CCB, Universidade Estadual de Londrina - UEL, CP 6001, CEP 86051-990, Londrina, PR, Brazil

^IICurso de Pós-graduação em Ciências Veterinárias, Departamento de Parasitologia Animal, Universidade Federal Rural do Rio de Janeiro - UFRRJ, CP 74508, CEP 23851-970, Seropédica, RJ, Brazil

^IIIDepartamento de Farmácia, Universidade de Cuiabá - UNIC, Tangará da Serra, MT, Brazil

ABSTRACT

The current information on the branchiuran Dolops bidentata, a species described more one hundred years ago, is valid but incomplete; hence, an expanded description is given herein. Additional morphological information was obtained by light and scanning electron microscopy from specimens collected on Pygocentrus nattereri from the Poconé Wetland, MT, Brazil. Description of the appendages and other structures such as respiratory area, mouth, details and ornamentation of antennules and maxillae are provided for the first time.

Keywords: taxonomy, Crustacea, Serrasalminae, fish parasites, neotropics.

RESUMO

O branquiúro Dolops bidentata foi descrito há mais de 100 anos, e a descrição original é válida, mas incompleta. Uma descrição expandida é dada, então, aqui. Informação morfológica adicional foi obtida por microscopia de luz e eletrônica de varredura para espécimes coletados de Pygocentrus nattereri do Pantanal de Poconé, MT, Brasil. Descrição dos apêndices e de outras estruturas tais como áreas respiratórias, boca, detalhes e ornamentação das maxilas e da antênula são apresentadas pela primeira vez.

Palavras-chave: taxonomia, Crustacea, Serrasalminae, parasitas de peixe, neotrópico.

1. Introduction

The Branchiura of freshwater habitats, consisting of the valid genera Argulus, Chonopeltis, Dipteropeltis, and Dolops, presently contains 113 valid species and 12 undescribed species (Poly, 2008). The entire group is composed of ectoparasitic species that usually live on fishes. The highest diversity of genera and species occurs in the Afrotropical and Neotropical Regions (Poly, 2008). Also, these crustaceans can be pointed out as one of those which cause greater economic loss to fish farms (Pavanelli et al., 1999).

Bouvier (1899a) described the crustacean Gyropeltis bidentata from French Guiana, after Bouvier (1899b) transferred this species to the genus Dolops. In Brazil, D. bidentata was recorded by Malta (1982) parasitising six species of fishes namely: Schizodon fasciatus, Prochilodus nigricans, Astronotus ocellatus, Serrasalmus nattereri, Rhytiodus microlepis and Colossoma bidens, but additional information about its morphology was not provided.

The main diagnostic character of D. bidentata is the maxilla, swollen at the base, and with two stout teeth. Despite the validity of the original description of D. bidentata by Bouvier (1899b), some structures were scarcely detailed. Characteristics such as the shape of the respiratory area on the ventral surface of lateral lobes, the mouth, the details and ornamentation of the maxillae and first antennae are lacking in Bouvier's illustrations. Thus, an expanded description is provided on the basis of an evaluation of specimens collected from Pygocentrus nattereri Kner, 1858 from Brazil, with additional information on ultrastructure obtained by scanning electron microscopy and additional morphological details obtained by light microscopy.

2. Material and Methods

In June, 2006 fifty nine specimens of Pygocentrus nattereri were collected from Coqueiro Bay (16º 15' 12'' S and 56º 22' 12'' W), Pirizal district, Poconé Wetland, in the state of Mato Grosso, Brazil. The fishes were collected by using a fishing rod and cast nets and identified according to Britski et al. (2007). The crustaceans were removed from the body surface and fixed in 70% ethanol. In the laboratory, some specimens were transferred to lactic acid and used to be drawn. Other specimens were prepared for scanning electron microscopy using standard techniques (Dedavid et al., 2007) and analysed with a FEI Quanta 200 scanning electron microscope in the Electron Microscopy and Microanalysis Laboratory of the Pró-reitoria de Pesquisa e Pós-graduação da Universidade Estadual de Londrina. Measurements are given in millimetres as the range followed by the arithmetic mean in parentheses and were made with the use of the software Motic Images Plus™ 2.0. The illustrations were made with the aid of a drawing tube mounted on a Hund Wetzlar H-600 phase contrast microscope. Voucher specimens are deposited in the Invertebrate Collection of the Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, AM, Brazil(INPA 1864).

3. Results

Dolops bidentata (Bouvier, 1899) (Figures 1, 2, 3)

Host: Pygocentrus nattereri Kner, 1858 (Characiformes: Serrasalminae)

Site of infection: Body surface

Locality: Coqueiro Bay (16º 15' 12'' S and 56º 22' 12'' W), Pirizal district, Poconé Wetland, State of Mato Grosso, Brazil.

Voucher specimens: 12 male specimens and nine female specimens, INPA.

Adult male (description based on 12 specimens)

Body sub-oval (Figure 1a, b), length 3.4-4.4 (3.9 mm); carapace oval, comprising 78.8% of total length. Ventral surface of frontal region and lateral lobes with numerous regularly arranged, sharply pointed, spines of dissimilar size along lateral lobes of carapace (Figure 1a). Eyes on dorsal surface, anterior to antero-lateral depressions. Antero-lateral depressions slight. Lateral lobes of carapace tapering, slightly rounded terminally, extending as far back as 3^rd pair of swimming legs; separated by broad sinus 1/4 length of carapace. Dorsal surface of carapace extensively spotted with dark dendriform markings (Figure 1b). Paired respiratory areas on ventral surface of lateral lobes; anterior respiratory area small and oval; posterior respiratory area with 1 indentation on medial margin (Figure 2a). Thorax distinctly 4-segmented. Abdomen sub-oval 0.9-1.3 (1.05 mm) comprising 21.2% of total length, abdominal lobes short, pointed terminally, abdominal margin serrated, separated by broad sinus 1/2 length of abdomen. Furcal rami small; adjacent to midline at anal sinus base; paired testes elongate and bilobed. Antennule 2 sections; stout proximal section; slender distal section; both 2-segmented. First segment of proximal section bearing large, broadly rounded posterior spine; second segment with stout anterior spine and large straight robust lateral spine. Distal section of antennule with terminal segment with group of apical spines. Antenna 4-segmented; 1^st carrying spines, 2^nd and 3^rd segments without ornamentation; 4^th terminating in group of apical spines (Figure 2b). Maxillule swollen at base, tipped with stout claws (Figure 2c). Mouth with mandibles covered with small teeth (Figure 2d). Maxilla 5-segmented (Figure 2e); basal segment with 2 teeth on each plate; oval area above spines unarmed; 2^nd to 5^th segments armed with simple, pectinate scales; terminal segment with cluster of stout setae. First to 4^th pair of legs biramous, 1^st to 3^rd near equal size and 4^th higher than the other; sympods 2-segmented; flagellum present on 1^st and 2^nd legs; extending medially from origin on dorsal surface at base of exopod. Small clusters of simple scales on swimming legs. Exopod only slightly longer than endopod in all the legs. Endopod of legs 1 to 4 of one segment. Sympods of all legs and natatory lobes bearing plumose setae similar to those on exo- and endopods. Natatory lobes of leg 4 with round posterior margin. Second, 3^rd and 4^th legs highly modified by accessory copulatory structures; posterior margin of first segment of 2^nd leg bearing large, unequal, 2 cup-shaped sockets; anterior margin of first segment of 3^rd leg bearing large, 2 cup-shaped sockets and accessory copulatory cushion on anterior margin of second segment of 4^th leg, all ornamented with specialised scales (Figure 2 f-i).

Adult female (description based on 9 specimens).

Body shape similar to the male (Figure 1c, d), length 2.5-5.5 (3.9 mm); carapace comprising 77.65% of total length. Abdomen sub-oval (0.7 mm), comprising 22.35% of total length, abdominal lobes short and less pointed than in male, separated by broad sinus 1/3 length of abdomen. Paired spermthecae oval, situated in fused part of abdomen. Cephalic appendages and first pair of legs similar to those of male. Second to 4^th pairs of legs unmodified.

4. Discussion

Some structures described in Bouvier (1899a, b) were scarcely detailed. Bouvier's description of D. bidentata stated that the first antenna is devoid of basal teeth and its palp ends bear 5 short bristles, but in our specimens the first antenna comprises 2 sections, the first segment of proximal section has a broad posterior spine and the second segment has anterior spine and large robust lateral spine. The terminal segment of the distal section has four apical spines. Bouvier (1899a, b) described the mandible with 16 teeth, but in our work we observed 24 teeth.

Unlike that observed in our specimens, in Bouvier's description, the 4^th pair of legs is smaller than the others. In the original description, the abdomen of the male is rounded and with a shallow slit in the back, but we observed in our specimens a sub-oval abdomen, pointed terminally, with the margin of the abdomen serrated, separated by broad sinus half the length of the abdomen. In the original description, the 2^nd and 3^rd pair of legs are modified by accessory copulatory structures, however in our specimens, as well as the 2^nd and 3^rd pair of legs, the 4^th pair is also modified and all are ornamented with specialised scales (not described by Bouvier). Furthermore, the respiratory areas located on the ventral surface of the lateral lobes, the mouth, the details of the maxillule and maxilla are absent in Bouvier's illustrations. All these morphological differences could be considered intraspecific variations as a result of ontogenetic changes or perhaps due to insufficient details of the appendages morphology given by Bouvier (1899a, b).

Acknowledegments - Authors would like to thank to Dr. Célia G. T. de Jesus Andrade and Osvaldo Capello from LMEM / PROPPG / UEL who assisted with the scanning electron microscopy analyses and to Diones Krinski from UNEMAT for his help with fish and parasites collections. Vanessa D. Abdallah was supported by a student fellowship from CNPq (Conselho Nacional de Pesquisa e Desenvolvimento Tecnológico, Brazil); Rodney K. Azevedo was supported by a student fellowship from FAPERJ (Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro, Brazil) and José L. Luque was partially supported by a Research fellowship from CNPq.

Received April 13, 2010

Accepted June 30, 2010

Distributed February 28, 2011

• BOUVIER, MEL., 1899a. Sur les "Argulides" du genre Gyropeltis, recueillis récemment par M. Geay dans la Guyane. Bulletin du Muséum d'Histoire Naturelle, vol. 5, p. 39-41.
• -, 1899b. Les crustacés parasites du genre Dolops Audoin. Bulletin Sociéte Philomatique de Paris, Série 8, vol. 10, p. 53-81.
• BRITSKI, HA., SILIMON, KZS. and LOPES, BS., 2007. Peixes do Pantanal: manual de identificação 2a. ed. Brasília, DF: Embrapa Informação Tecnológica. 227 p.
• DEDAVID, BA., GOMES, CI. and MACHADO, G., 2007. Microscopia eletrônica de Varredura. Aplicações e preparação de amostras Porto Alegre: EDIPUCRS. 60 p.
• MALTA, JCO., 1982. Os argulídeos (Crustacea: Branchiura) da Amazônia brasileira. Aspectos da ecologia de Dolops discoidales Bouvier 1899 and Dolops bidentata Bouvier 1899. Acta Amazonica, vol. 12, no. 3, p. 521-528.
• POLY, WJ., 2008. Global diversity of fishlice (Crustacea: Branchiura: Argulidae) in freshwater. Hydrobiologia, vol. 595, no. 1, p. 209-212.
• PAVANELLI, GC., EIRAS, JC. and TAKEMOTO, RM., 1999. Doenças de peixes: profilaxia, diagnóstico e tratamento. Maringá: EDUEM. 264 p.

Publication Dates

• Publication in this collection
  14 Mar 2011
• Date of issue
  Feb 2011

History

• Received
  13 Apr 2010
• Accepted
  30 June 2010