Helminths of the marine tucuxi, Sotalia fluviatilis (Gervais, 1853) (Cetacea: Delphinidae), in northern Rio de Janeiro State, Brazil

BIOLOGICAL AND APPLIED SCIENCES

Helminths of the marine tucuxi, Sotalia fluviatilis (Gervais, 1853) (Cetacea: Delphinidae), in northern Rio de Janeiro State, Brazil

Osana Prado Melo^I; Renata Maria Arruda Ramos^II; Ana Paula Madeira Di BenedittoI, ^*

^IUniversidade Estadual do Norte Fluminense - UENF; CBB; Laboratório de Ciências Ambientais; Av. Alberto Lamego, 2000; 28013-600; Campos do Goytacazes - RJ - Brasil

^IIEverest Tecnologia em Serviços Ltda.; Av. N. S. dos Navegantes, 675/1201; 29056-900; Vitória - ES - Brasil

ABSTRACT

The objectives of this work were to reporte the helminths of the marine tucuxi, Sotalia fluviatilis (Cetacea: Delphinidae) in northern Rio de Janeiro State; and to check if the infestation rate varied with the host characteristics (sex and maturity) and year seasons. From 1989 to 2002, 80 marine tucuxis that were by-caught in fisheries were examined and four parasites were recorded: Braunina cordiformis, Anisakis typica, Halocercus brasiliensis and Nasitrema sp. The parasitism in the marine tucuxi corroborated its feeding habits and there were no infestation rate differences between males and females, youngs and adults, as well as between year seasons. This work reports for the first time the occurrence of the genus Nasitrema in the marine tucuxi.

Key words:Sotalia fluviatilis, marine tucuxi, helminths, Rio de Janeiro State, Brazil

RESUMO

Os objetivos deste trabalho foram reportar os helmintos parasitas do tucuxi marinho, Sotalia fluviatilis, na costa norte do Estado do Rio de Janeiro; e checar se a taxa de infestação varia com as características do hospedeiro (sexo e maturidade) e estações do ano. Entre 1989 e 2002, 80 tucuxis marinhos capturados acidentalmente em pescarias foram examinados e quatro espécies de parasitas foram registradas: Braunina cordiformis, Anisakis typica, Halocercus brasiliensis e Nasitrema sp. O parasitismo no tucuxi marinho corrobora seu hábito alimentar e não foram constatadas diferenças nas taxas de infestação entre machos e fêmaes, jovens e adultos, assim como entre as estações do ano. Este trabalho reporta pela primeira vez a ocorrência do gênero Nasitrema no tucuxi marinho.

INTRODUCTION

Sotalia fluviatilis (Gervais, 1853) (Cetacea: Delphinidae), known as tucuxi, occurs in Central and South America, including the basins of Amazon and Orinoco Rivers (Borobia et al., 1991). Two different ecotypes are recognized based on skull and body dimensions: marine and fluvial forms (Jefferson et al., 1993). Marine tucuxi inhabits coastal and estuarine waters and despite its continuous occurrence along the distributional range, it is one of the less studied delphinids.

In the Brazilian coast, the knowledge about the parasites associated with the marine tucuxi is still scarce. Previous studies were based on few specimens stranded on the beach or by-caught in fisheries (e.g. Borobia and Barros, 1989; Da Silva and Best, 1996; Marigo et al., 1999). Santos et al., (1996) carried out the first quantitative study about the parasitism of this cetacean, analyzing 23 specimens from northern Rio de Janeiro State.

The objectives of the present work were to report the parasites of this cetacean in northern Rio de Janeiro State, adding new information to the study conducted by Santos et al. (1996); and to check if the infestation rate varies with the host characteristics (sex and maturity) and year seasons.

MATERIALS AND METHODS

From 1989 to 2002, 80 specimens of the marine tucuxi were collected as by-catch in fisheries carried out between Barra do Itabapoana (21º18'S, 40º45'W) and Macaé (22º25'S, 41º46'W) (Figure 1). The host characteristics considered in this work were sex (male and female) and maturity (young and adult). The last one was estimated according to Ramos et al. (2000) which considered males and females as adults when e•6 years old and body length e•180.0 cm and e•6 years old and body length e•160.0 cm, respectively. The year seasons were grouped into spring-summer, from October to March; and autumn-winter, from April to September. These seasons included the highest and lowest recorded values of temperature and rainfall, respectively (Martin et al., 1998).

The cetaceans were necropsied and the stomachs, intestines, lungs, liver, heart, gonads and nasal cavity were only macroscopically examined to verify the helminths presence. Prevalence and mean intensity were calculated following Bush et al. (1997). The Chi-square test (Zar, 1996) was used to compare the infestation rate between the hosts.

Parasites recovered were fixed in 5% formalin and were deposited in the collection from Laboratório de Ciências Ambientais, UENF.

RESULTS

Four parasite species were identified: two Nematoda, Anisakis typica and Halocercus brasiliensis; and two Trematoda, Braunina cordiformis and Nasitrema sp. Overall prevalence was 50% (N= 80), representing 40 animals infested. B. cordiformis was found in the second and third stomach compartment of 26 animals; A. typica in the first stomach of 19 animals; H. brasiliensis in the lungs of five animals; and Nasitrema sp. in the nasal cavity of eight animals. Prevalence and mean intensity of parasite species are shown in Table 1. Comparisons between the marine tucuxis infested did not show significant differences (p >0,05) for the variables sex, maturity and year seasons.

DISCUSSION

The helminths A typica, H. brasiliensis and B. cordiformis have been already reported as parasites of the marine tucuxi in northern Rio de Janeiro State by Santos et al. (1996). This work corroborates their occurrence and reports for the first time the genus Nasitrema in this host. Cetaceans can be definitive hosts of several helminths species and most of them they are infected through the food chain (Dailey and Brownell, 1972). The dolphin's prey species are fish, mollusks and crustaceans, which are the intermediate hosts of their parasites (Geraci and Lounsbury, 1993). In the study area, despite 36 different prey species were eaten by the marine tucuxi, the Atlantic cutlassfish, Trichiurus lepturus, was dominant in its diet, being the preferred prey (Di Beneditto et al., 2001).

Unfortunately, information about the parasitism of the Atlantic cutlassfish along the study area is inexistent. However, Chung et al. (1996) described the high infestation rate of the nematode Anisakis simplex in the intestine of the Atlantic cutlassfish specimens collected in Taiwan. Considering that in the study area A. typica was found in the marine tucuxis examined, this fish could be its intermediate host. Rohde et al. (1995), describing the parasitism of marine fish, found trematodes in the Atlantic cutlassfish, indicating its potential to be intermediate host of these parasites.

Low diversity in parasite species is related to host diet (Aznar et al., 1994). Only four parasite species were recorded in the marine tucuxi along the study area. The narrow range of preferred prey in its diet could be the factor determining the low diversity of parasite groups. The same pattern was recorded for Commerson's dolphin (Cephalorhynchus commersonii) and franciscana (Pontoporia blainvillei) in Argentinian waters (Aznar et al., 1994; Berón-Vera et al., 2001).

The absence of significant differences between sex, maturity and seasons was consistent with recent findings in diet studies. Di Beneditto et al. (2001) did not found differences in diet composition between those features in marine tucuxis collected in northern Rio de Janeiro State. Unfortunately, the lack of quantitative studies about the parasitism of the marine tucuxi along its distribution range did not allow interpopulations' comparisons. More samples are needed to understand the host-parasite interactions in this cetacean species.

ACKNOWLEDGEMENTS

The authors would like to thank to Dr. Claúdia P. Santos from FIOCRUZ who confirmed the parasite species and Dr. Leandro R. Monteiro from UENF for reviewing this manuscript. We also express our appreciation to the fishermen from Atafona who provided the cetaceans' carcass. A.P.M. Di Beneditto was supported by CNPq (Process nº 300322/03-8). This work is a contribution of the Graduate Program of Ecology and Natural Resources/UENF.

Received: May 10, 2004;

Revised: March 17, 2005;

Accepted: August 01, 2005.

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*

Author for correspondence.

Publication Dates

• Publication in this collection
  10 Apr 2006
• Date of issue
  Jan 2006

History

• Accepted
  01 Aug 2005
• Reviewed
  17 Mar 2005
• Received
  10 May 2004