Theletrum lamothei sp. nov. (Digenea), parasite of Echidna nocturna from Cuajiniquil, Guanacaste, and other digenes of marine fishes from Costa Rica     Gerardo Pérez-Ponce de León¹ , Virginia León-Règagnon ¹ , Scott Monks ²     Received 11-VI-1997. Corrected 24-II-1998. Accepted 3-III-1998.

Abstract

A new species of Theletrum is described from the intestine of two palenose morays, Echidna nocturna, collected in Cuajiniquil, Guanacaste Province, Costa Rica. The new species differs from the type species, T. fustiforme Linton, 1910 by having a subspherical pars prostatica, a subspherical seminal vesicle extending anteriorly to the anterior border of the acetabulum, by the presence of a poorly developed hermaphroditic sac, and by having a larger body size. We also report eight additional species of digeneans parasitizing marine fishes in several localities along the Atlantic and Pacific coast of Costa Rica: Bianium simonei, Didymozoinae (metacercariae), Ectenurus virgulus, Hypocreadium myohelicatum, Lecithochirium microstomum, Pseudolecithaster sp., Stephanostomum casum, and Tergestia laticollis. In addition, we present an updated list of helminth parasites of marine fish from Costa Rica and discuss the importance of including parasites as an integral part of biodiversity inventories.
 

Key words

Theletrum lamothei sp. nov., helminths, digenean, marine fish, Costa Rica.
 

Surveys of helminth parasites of wildlife in Costa Rica are relatively few; previous to this study, 60 helminth species have been collected from Costa Rican vertebrate and invertebrate hosts. Of these, 25 are parasites of marine and freshwater fishes, including five monogeneans, 11 digeneans and eight cestodes (Brooks & McCorquodale 1995, Marques et al. 1995, 1996;Lamothe et al. 1997), as well as one acanthocephalan (Van Cleave 1940, Monks et al. 1997). This information is difficult to obtain because it is disperse throughout various sources, and was published over a period of 45 years. In consideration of the initiative developed by Costa Rica to establish an inventory of the biological diversity within its territory, and to facilitate their efforts to preserve biodiversity, the objectives of this paper are to compile and update information related to the knowledge of platyhelminth parasites of marine and freshwater fishes from Costa Rica. In addition, we describe a new species of digenean belonging to Theletrum Linton 1910, collected from a marine fish in the locality of Playa Cuajiniquil, Guanacaste Province.
 
 

Material and Methods

Information about previous records of platyhelminth parasites of fishes from Costa Rica was obtained from the data base of the Colección Nacional de Helmintos (CNHE), Instituto de Biología, U.N.A.M., Mexico City, as well as a bibliographical search for recent publications. The new records we present herein, along with the new species, are from the capture of several fish species we made in February, 1996, at Playa Cuajiniquil, Guanacaste Province (10°, 57' N, 85°, 38'W), Playa Ocotal, Guanacaste Province (10°, 32' N, 85°, 44' W), Playa Hermosa, Guanacaste Province (10°, 38' N, 85°, 38' W) and Playa Nacascolo, Bahía Prieta, Limón Province (10°, 38' N, 85°, 38' W). Helminths were relaxed with hot tap water and fixed in AFA or Bouin's fluid. Worms were stained with Ehrlich's hematoxylin, Mayer's paracarmine or Gomori's trichrome and mounted as permanent slides with Canada balsam. Measurements are in mm unless otherwise indicated, and include the average and range in parentheses. Drawings were made with the aid of a camera lucida and all specimens were deposited at the CNHE, Mexico City, and in the United States National Parasite Collection (USNPC), Beltsville, Maryland; HWML refers to the University of Nebraska State Museum, Harold W. Manter Laboratory, Division of Parasitology, Lincoln, Nebraska.
 

Results

In this study, we collected nine species of digenean parasites in six species of marine fishes from several localities of the Atlantic and Pacific coasts of Costa Rica (Table 1). In addition, 18 fish species examined were negative for digeneans (Table 2). We describe a new species of Theletrum Linton 1910, and present additional information in relation to other digeneans that represent new host and locality records. These species are not described nor illustrated; we only note morphological features and data relating to geographical distribution.

TABLE 1  

Helminths (Monogenea, Digenea, Eucestoda, Acanthocephala, Nematoda) parasites of marine and  freshwater fishes from Costa Rica.
Helminth	Host	Locality	Reference
MONOGENEA
Ahpua piscicola Bravo 1973	Caranx caballus	Golfo de Nicoya	Lamothe et al. 1997
	Oligoplites altus
Choricotyle louisianensis Hargis 1955.	Menticirrhus sp.	Puntarenas	Bravo & Arroyo 1962b
Pseudomazocraes monsivaesae
Caballero y Bravo 1955	Vomer declivifrons	Puntarenas	Lamothe et al. 1997
Polymicrocrocotye manteri Lamothe 1967	Lutjanus colorado	Golfo de Nicoya	Lamothe et al. 1997
Tagia ecuadori (Meserve 1938)
Sproston 1946	Sphaeroides sp.	Puntarenas	Bravo & Arroyo 1962b
DIGENEA
Acanthostomum gnerii Szidat 1954	Rhamdia rogersi	San José	Caballero & Brenes 1957
Bianium plicitum (Linton 1928) Stunkard 1930	Sphaeroides sp.	Puntarenas	Caballero & Brenes 1957
B. simonei (Travassos,Freitas and Buhrheim)
Yamaguti, 1971	Arothron hispidus	Bahía Prieta	This work
Bucephalus introversus Manter, 1940	Caranx hippos	Bahía Culebra	Manter 1940
Crassicutis cichlasomae Manter 1936	Cichlasoma sp.	Liberia, Guanacaste	Bravo & Arroyo 1962a
Crassicutis opisthoseminis Bravo y Arroyo 1962	Cichlasoma sp.	Liberia, Guanacaste	Bravo & Arroyo 1962a
Didymozoinae Poche 1907 (Metacercarias)	Haemulon maculicauda	Bahía Culebra	This work
Ectenurus virgulus Linton 1910	Fistularia commersoni	Playa Ocotal	This work
Helicometrina sinuata (Rudolphi, 1819)	"Moray"	Bahía Culebra	Manter 1940
Hypocreadium myohelicatum	Epinephelus itajara	Playa Cuajiniquil	This work
Lecithochirium monticellii (Linton 1998)
Crowcroft  1946	Synodus sp.	Puntarenas	Bravo & Arroyo 1962b
Lecithochirium microstomum Chandler 1935	Fistularia commersoni	Playa Ocotal	This work
Manteria brachydera (Manter 1940)
Caballero 1950	Oligoplites altus	Golfo de Nicoya	Ponciano 1986
	O. refulgens "	Golfo de Nicoya	"
	Caranx caballus	Golfo de Nicoya	"
Mecoderus oligoplitis Manter 1940	Oligoplites sp.	Puntarenas	Bravo & Arroyo 1962b
	O. altus, O. refulgens	Golfo de Nicoya	Ponciano 1986
Proctotrema costaricae Manter 1940	"Medialuna"	Bahía Culebra	Manter 1940
Pseudolecithaster Campbell and Munroe 1972	Echidna nocturna	Playa Cuajiniquil	This work
Stephanostomum casum (Linton 1910)
McFarlane 1934	Epinephelus itajara	Playa Cuajiniquil	This work
Tergestia laticollis (Rudolphi 1819) Stossich 1899
	Caranx caballus	Playa Ocotal	This work
	Caranx caballus	Bahía Culebra	Manter 1940
Theletrum lamothei sp. nov.	Echidna nocturna	Playa Cuajiniquil	This work
EUCESTODA
Acanthobothrium nicoyaense Brooks y McCorquodale 1995	Aetobatus narinari	Golfo de Nicoya	Brooks & McCorquodale 1995
A. costarricense Marques, Brooks y Monks 1995.	Dasyatis longus	Golfo de Nicoya	Marques et al. 1995
A. cimari Marques, Brooks y Monks 1995.	D.longus	Golfo de Nicoya	Marques et al. 1995
A. puntarenense Marques, Brooks y Monks 1995.	D.longus	Golfo de Nicoya	Marques et al. 1995
A. vargasi Marques, Brooks y Monks 1995.	D.longus	Golfo de Nicoya	Marques et al. 1995
A. campbelli Marques, Brooks y Monks 1995.	Urotrygon chilensis	Golfo de Nicoya	Marques et al. 1995
Acanthobothroides pacificus Marques, Brooks y Molina 1996.	Himantura pacifica	Bahía Culebra	Marques et al. 1995
Rhinebothrium geminum Marques, Brooks y Molina 1996.		Bahía Culebra	Marques et al. 1995
ACANTHOCEPHALA
Koronacantha pectinaria (Van Cleave 1940)
Monks, Marques,	Microlepidotus brevipinnis	Playa Cuajiniquil	Monks et al. 1997
León-Règagnon and Pérez-Ponce de León 1996	"Medialuna"	Bahía Culebra	Van Cleave 1940
NEMATODA
Echinocephalus janzeni Hoberg, Brooks, Molina y Erbe 1997	Himantura pacifica	Playa Cuajiniquil	Hoberg et al. en prensa

    TABLE 2 List of fishes examined that were negative for platyhelminths.  
 

No. of Fishes               Fish Species                      No. of Fishes                   Fish Species

  1             Alphestes immaculatus Breder, 1936                1        Lutjanus colorado Jordon and Gilbert, 1882
  1             Anisotremus interruptus (Gill, 1862)                  1        Lutjanus synagris (Linnaeus, 1758)
  2             Anisotremus scapularis (Tschudi, 1845)            1        Muraena lentiginosa Jenyns, 1842
  5            Calamus brachysomus (Lockington, 1880)         1        Mycteroperca xenarcha Jordan, 1888
  1            C. taurinus (Jenyns, 1842)                                1        Orthopristis forbesi (Jordan and Starks, 1897)
  3            Centropomus viridus Lockinham, 1877               1        Pomadasys elongatus (Steindachner, 1879)
  1            Cirrhitus rivulatus Valenciennes, 1855                1        Pseudupeneus grandisquamis (Gill, 1863)
  3            Diodon holocanthus Linnaeus, 1758                   2        Selene brevioortii (Gill, 1863)
  1            Eucinostomus currani Yanez-Aranciba, 1978      1        S tegastes acapulcoensis (Fowler, 1944)
 
 

Digenea Van Beneden, 1858 Familia Hemuiridae Looss 1907 Theletrum lamothei sp. nov. (Figs. 1A, 1B)

Description (based on nine specimens): Body elongate, smooth, 3.85 (2.61-5.40) long to 0.57 (0.42-0.65) wide at the level of acetabulum. Complete circular postacetabular ridge present. Tegument not serrated and tail appendage absent. Oral sucker subterminal, 0.22 (0.17-0.27) long by 0.24 (0.19-0.28) wide. Preoral lobe present. Acetabulum 0.39 (0.31-0.45) long and 0.39 (0.27-0.47) wide, and located in anterior one-third of body. Ratio of length of oral sucker to length of acetabulum 1: 1.77 (1.43-1.99). Pharynx subspherical, 0.10 (0.08-0.14) long by 0.12 (0.11-0.14) wide. Esophagus very short. Intestinal cecae extending almost to posterior end of body.
 

Fig. 1. Theletrum lamothei sp. nov. from Echidna nocturna. A. Holotype, dorsal view. B. Genitalia terminal showing the seminal vesicle, pars prostatica, and the base of the hermaphroditic sac.
 

Testes subspherical, oblique, and postacetabular. Anterior testis 0.24 (0.12-0.34) long by 0.23 (0.17-0.29) wide; posterior testis 0.28 (0.22-0.34) long by 0.28 (0.22-0.32) wide. Seminal vesicle saccate, overlapping anterior border of acetabulum; vesicle 0.21 (0.13-0.32) long by 0.15 (0.11-0.19) wide. Pars prostatica vesicular, 0.23 (0.16-0.35) long by 0.16 (0.11-0.22) wide, surrounded by numerous glandular cells. Hermaphroditic sac membranous, indistinct, and cylindrical; 0.05 (0.04-0.05) long by 0.04 (0.03-0.07) wide. Copulatory organ absent. Genital pore postbifurcal.

Ovary subspherical, located near posterior end of body; ovary 0.23 (0.15-0.29) long by 0.29 (0.26-0.35) wide. Vitelline glands forming two compact, oblique, postovarian masses; borders generally smooth, slightly lobate in some specimens. Vitellaria on left side 0.32 (0.23-0.36) long by 0.22 (0.18-0.27) wide; on right side 0.31 (0.22-0.56) long by 0.23 (0.17-0.29) wide. Juel's organ situated between vitelline glands and ovary. Uterine seminal receptacle present. Uterus entirely preovarian, opening at base of hermaphroditic sac. Eggs 32.15µm (32-35µm) long and 15.67µm (13-19µm) wide. Excretory vesicle "Y" shaped, excretory stem bulbous; excretory pore wide, terminal.

Type-Host: Echidna nocturna (Cope, 1872)
(Muraenidae)
Site of infection: Intestine
Type- Locality: Playa Cuajiniquil, Golfo
Santa Elena, Guanacaste Province (10°, 57' N, 85°, 38' W)
Specimens deposited: Holotype: CNHE No. 3179. Paratypes: CNHE No. 3180; USNPC No. 87581.
Etymology: This species is named in honor of Dr. Rafael Lamothe Argumedo, who, as a collaborator with costarican parasitologists, has contributed much to the knowledge of helminth diversity of Costa Rica.

Remarks: The genus Theletrum was originally established to include T. fustiforme (Linton 1910). Three additional species, T. frontilatus Manter 1969, a parasite of Siganus rivulatus Forskal in Moreton Bay, Queensland, Australia (subsequently allocated by Yamaguti (1971) to Hysterolecithoides Yamaguti, 1934), T. gravida Manter 1940 in Abudefduf saxatilis Linnaeus from the Pacific coast of Mexico, and T. magnasaccus Sogandares-Bernal and Sogandares 1961, a parasite of A. saxatilis in the Atlantic coast of Panama (both later transferred by Yamaguti (1971) to genus Genolinea Manter 1925), were added later. Gibson & Bray (1979) erected Neotheletrum for the latter 3 species, making Theletrum monotypic. Both T. lamothei, and the type species, have a preoral lobe and a postacetabular ridge in the tegument, as well as possessing a uterine seminal receptacle and a Juel's organ. In Linton's (1910) original description of T. fustiforme, a seminal receptacle is mentioned, however, after examination of the original type specimens and vouchers (USNPC 8500, 39392; HWML 473, 124642), we agree with Gibson & Bray (1979) that this structure is absent. The new species differs from T. fustiforme in the shape of the pars prostatica because, in the new species, it forms a subspherical vesicle, while in T. fustiforme, it is elongate. Furthermore, the two species differ in the shape of the seminal vesicle; in T. lamothei sp. nov. the vesicle is subspherical and only extends to the anterior border of the acetabulum, but in T. fustiforme it is elongate, sinuous, and extends posteriorly beyond the anterior border of the acetabulum, and the hermaphroditic sac is less developed in the new species than in T. fustiforme. Additionally, the new species differs from T. fustiforme by having a larger body size (2.6-5.4 x 0.42-0.65 vs. 1.47-1.82 x 0.35, respectively), as well as in the dimensions of suckers, testes, and ovary. The current study represents the first report of a member of this genus from the Pacific coast of Central America; T. fustiforme is only known from the Gulf of Mexico and the Caribbean Sea.

   Larval Didymozoid (Didymozoinae Poche 1907) not identified (Metacercariae)

Seven metacercariae were collected with morphometric characteristics consistent with those described in marine fishes from Australia as "species 5" by Køie & Lester (1985). Leòn-Règagnon et al. (1997) recorded this didimozoinid metacercariae in 14 fish species from Chamela Bay, Mexico. They found a higher prevalence and abundance in fishes from the Haemulidae. Our results are in accordance with their findings in that we collected these specimens from Haemulon maculicauda Gill 1963. Taxonomic identification at the species level was not possible because specimens were collected as larval stages; adult didimozoinids are parasites in gills of larger size fishes (Yamaguti 1971).

Host: Haemulon maculicauda Gill 1963 (Haemulidae)
Site: gills
Locality: Playa Hermosa, Bahía Culebra (10°, 38' N, 85°, 38' W)
Specimens deposited: CNHE: 3182 (9 specimens)

  Ectenurus virgulus Linton 1910

We found a single specimen of E. virgulus. This species differs from the only other member of the genus in the Americas, E. americanus (Manter 1947) Manter & Pritchard 1960, by having the suckers located further apart and by having a smaller acetabulum than the other species. Ectenurus virgulus is not highly host specific, having been reported as a parasite of 12 genera of fishes, representing 6 different families. This species has been reported from the Gulf of Mexico, Caribbean Sea, and the Pacific coast of Mexico (Yamaguti 1971, Lamothe et al. 1997, León-Règagnon et al. 1997). The current study is the second report of this digenean from Pacific Ocean, and represents a new host and locality record.

Host: Fistularia commersonii Ruppell 1835 (Fistularidae
Site: Intestine.
Locality: Playa Ocotal, Guanacaste Province (10°, 32' N, 85°, 44'  W)
Specimens deposited: CNHE: 3183 (1 specimen)

   Lecithochirium microstomum Chandler 1935

One specimen from the intestine of Fistularia commersonii was identified as L. microstomum. This species is widely spread in tropical and subtropical Atlantic and Pacific oceans around the world, and exhibits a low host specificity because it has been found in many host species from different families. The record of L. microstomum in a fistularid from Costa Rica confirms this low host specificity.

Host: Fistularia commersonii (Fistularidae)
Site: Intestine
Locality: Playa Ocotal, Guanacaste Province (10°, 32' N, 85°, 44' W).
Specimens deposited: CNHE: 3175 (1 specimen)
 

Pseudolecithaster sp.

This genus includes 2 species. The type species, P. antimorae, was described from the Western North Atlantic by Campbell and Munroe (1977). Pseudolecithaster alocytii (Tkachuk 1979) Aleshkina & Gaevskaja 1985 has been recorded from the Indian Ocean, Australia, New Zealand and the Atlantic coast of Africa (Tkachuk 1979, Korotaeva 1983, Aleshkina & Gaevskaya 1985). The single specimen we collected differs from both species in the shape of the ovary, which is multilobed in those species and spherical with smooth borders in our specimen. The vitelline lobes are also different in the specimen from Costa Rica, being almost spherical, in contrast with the other species, in which they are elongate. The terminal genitalia, which is of great taxonomic value, cannot be observed with detail in our specimen.

This differences and the geographical distribution make us believe that we are dealing with an undescribed species, but the lack of additional material does not permit a description in this study.
Host: Echidna nocturna (Cope, 1872) (Muraenidae)
Site: Intestine
Locality: Playa Cuajiniquil, Golfo Santa Elena, Guanacaste Province (10°, 57' N, 85°, 38' W)
Specimens deposited: CNHE: 3176 (1 specimen)
 

Family Lepocreadiidae (Odhner 1905) Nicoll 1935 Bianium simonei (Travassos, Freitas and Buhrnheim, 1965) Yamaguti, 1971

Eight digeneans were identified as B. simonei, a species previously described as parasite of Spheroides testudineus Linnaeus from Brazil (Yamaguti 1971). This species was originally allocated to genus Amarocotyle Travassos, Freitas and Buhrnheim, 1965 but transferred to Bianium by Yamaguti (1971) based on the examination of the type material. The present constitutes a new host and locality record.
Host: Arothron hispidus (Linnaeus, 1758) (Tetraodontidae)
Site: Intestine
Locality: Playa Nacascolo, Bahía Prieta, Limón Province (10°, 38' N, 85°, 38'  W)
Specimens deposited: CNHE: 3181 (8 specimens).

  Hypocreadium myohelicatum Bravo and Manter 1957

Twenty specimens were collected from the intestine of Epinephelus itajara Lichtenstein 1822 and identified as Hypocreadium myohelicatum. Taxonomy of this group of digeneans has been controversial; Manter (1940) and Nahhas & Cable (1964) considered genus Hypocreadium Ozaki 1936 a synonym of Pseudocreadium Layman 1930. Yamaguti (1971) consider them as independent genera and, in this work, we follow Yamaguti's criteria. This species was originally described from the Pacific coast of Mexico, in Puerto Vallarta, Jalisco, as parasite of Balistes capistratus (= B. polylepis Steindachner 1876) by Bravo & Manter (1957); later, Ponciano (1986) reported H. myohelicatum from Trachinotus rhodopus Gill in Puerto Angel, Oaxaca. In this work, we present a new host and locality record for H. myohelicatum.
Host: Epinephelus itajara Lichtenstein 1822 (Serranidae)
Site: Intestine.
Locality: Playa Cuajiniquil, Golfo Santa Elena, Guanacaste Province (10°, 57' N, 85°, 38' W)
Specimens deposited: CNHE: 3174 (18 specimens)

  Family Acanthocoplidae Lühe 1909 Stephanostomum casum (Linton 1910) McFarlane 1934

One specimen of S. casum was identified based on body form, sucker ratio, anterior extent of the vitellaria, extent of the cirrus sac, and the presence of 36 oral spines. However, we could not observe the uroproct, which is characteristic of this species. This species was originally described by Linton (1910) from the intestine of Lutjanus griseus Linnaeus 1758 from Tortugas, Florida. In the Pacific coasts, it was recorded by Manter (1940) in L. viridis Valenciennes 1845 from Galapagos Islands, Ecuador, and in L. jordani Gilbert 1897 from Secas Islands, Panama, and finally, from L. novemfasciatus Gill 1862 from Oaxaca, Mexico. The present constitutes a new host and locality record.

Host: Caranx caballus Günther 1869 (Carangidae)
Site: Intestine
Locality: Playa Ocotal, Guanacaste Province (10°, 32' N, 85°, 44'  W)
Specimens deposited: CNHE: 3177 (1 specimen)

  Family Fellodistomidae Nicoll 1913 Tergestia laticollis (Rudolphi, 1819) Stossich, 1899

Two specimens were identified as T. laticollis based on the shape and dimensions of the body, the number of cervical folds and by the presence of a semicircle of lanceolate muscular lobes around the oral sucker. This digenean was previously recorded from the Pacific coast of Costa Rica by Manter (1940) as a parasite of Caranx caballus Günther 1864. However, this species exhibits a wide geographical distribution and low host specificity at the species level because it has been reported from 14 different fish species, mainly from Carangidae and Scombridae (Yamaguti 1971). Additional records of T. laticollis in the Pacific coast include those made by Ponciano (1986) and Castillo et al. (in press) from Caranx hippos Linnaeus 1758 from Puerto Angel, Oaxaca, and from Euthynnus lineatus Kishinouye from Chamela Bay, Jalisco, México, respectively.

Host: Caranx caballus Günther 1869 (Carangidae)
Site: Intestine
Locality: Playa Ocotal, Guanacaste Province (10°, 32' N, 85°, 44'  W)
Specimens deposited: CNHE: 3178 (2 specimens)
 

Discussion

In this study, we report 9 species of digenean parasites of marine fishes of Costa Rica from 6 species of hosts, to increase the total number of species reported to 34. By comparison, we have recorded 148 species of helminth parasites from 98 species of fish from the Pacific coast of México; these data were collected as a result of isolated studies that began in the 1940's and continue to this date (Lamothe et al. 1997). Clearly, we are still in the beginning stages of a complete understanding of the biodiversity of helminth parasites of the fishes of Costa Rica.

It is interesting to compare the results of the current study with those from fishes collected from Chamela Bay, Jalisco, México. This locality represents the northernmost extent of the dominant marine currents found in Costa Rican waters. The warm Costanera current begins near the equator, and near Chamela Bay, mixes with the cold California current (Wyrtky 1965 in Pacheco 1991). The sharing of numerous species of parasites of fishes from Costa Rica with fishes from the Pacific Coast of México may be, in part, a result of these north-flowing currents from Costa Rica. Among others, the presence of the digeneans Tergestia laticollis (Castillo et al. 1997), and Lecithochirium microstomum (León-Règagnon et al. 1997), the acanthocephalan Koronacantha pectinaria (Monks et al. 1997), and the nematode Echinocephalus janzeni (Hoberg et al in press) may be either the result of migration patterns of the definitive hosts or the result of passive transport of intermediate hosts by marine currents.

Despite the scarcity of surveys of helminths from marine fishes of Costa Rica, the proportions of each group in our study is relatively consistent with surveys of marine fishes from other localities. In our study, digeneans are the most common group (54.3%), and of these, 31.6% represent the order Hemiuriformes. This is consistent with studies of the digenean fauna of marine fishes from various other localities (Manter 1940, Nahhas & Cable 1964, Overstreet 1969, León-Règagnon et al. 1997).

Marine fishes constitute an important resource group, both as a feature of ecotourism and as a food source, so they should be considered an essential feature of initiatives for preservation and sustainable use of biodiversity. Just as with any other type of wildlife, fishes are susceptible to damage caused by parasites, and information about host-parasite relationships is essential to wise management. Thus, knowledge of the parasite fauna should be an integral part of any biodiversity inventory. Fishes are an important source of animal protein for human consumption, and the impact of parasites on fish populations, especially those maintained for aquacultural purposes, is well documented (Williams & Jones 1994, Rohde 1993). In addition, the potential risk of transmission of zoonotic diseases, such as anisakiasis (Sakanari 1990) through the consumption of parasitized fish, could cause public health problems (Williams & Jones 1994). In conclusion, we would like to highlight the importance making a biodiversity inventory that includes not only animals and plants that are attractive and charismatic, but also those organisms that live in close association with them, and which, at some critical moment, may alter survival rates, and in this way, break the delicate balance of the ecosystem.
 
 

Acknowledgements

We gratefully acknowledge the help of Instituto Nacional de Biodiversidad (INBio) for the kind use of their facilities, collecting permits and technical support in collecting hosts. Some of these hosts were collected while we were participating in an INBio training course in Vertebrate Parasitology for Parataxonomists at the Guanacaste Conservation Area in February, 1996; we appreciate the help and interest of the Parataxonomists involved in this training course. We also thank Helena Molina, Escuela de Biología, Universidad de Costa Rica for her support to obtain and identify fishes, and Greg Klassen (Tau Biodiversity, N.B., Canada) and Fernando Marques (University of Toronto) for assistance in the field. We also thank Ralph Lichtenfels, curator of the USNPC and Scott Gardner, curator of HWML for the loan of specimens of Theletrum fustiforme. This study was partially funded by operating grant No. A7696 from the Natural Sciences and Engineering Council (NSERC) of Canada to Daniel R. Brooks, and travel expenses from INBio to GPPdL.
 
 

Resumen

Se describe una especie nueva de digéneo del género Theletrum, parásito del intestino de una "morena pecosa", Echidna nocturna, recolectada en Playa Cuajiniquil, Provincia de Guanacaste, Costa Rica. La nueva especie es diferente de T. fustiforme Linton, 1910, la especie tipo, por presentar una pars prostatica subesférica, una vesícula seminal subesférica que se extiende hasta el borde anterior del acetábulo, por la presencia de un saco hermafrodita y por una mayor longitud del cuerpo. También se registran ocho especies adicionales de digéneos parásitos de peces marinos en varias localidades de las costas del Atlántico y del Pacífico de Costa Rica. Por último, presentamos una lista actualizada de los helmintos parásitos de peces marinos y dulceacuícolas de Costa Rica y discutimos la importancia de incluir a los parásitos como una parte integral de las investigaciones sobre biodiversidad.
 

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¹ Laboratorio de Helmintología, Instituto de Biología U.N.A.M. Ap. Postal 70-153 C.P. 04510, México D.F. email: ppdleon@servidor.unam.mx

² Department of Zoology, University of Toronto, Toronto, Ontario 1A1 3G5, Canada.