Among the several groups of copepods that are teleost parasites, the siphonostomatoid family Caligidae is by far the most widespread and diverse. With more than 108 nominal species, the caligid genus Lepeophtheirus von Nordmann is one of the most speciose. There are no reports of this genus in Costa Rican waters. A new species of Lepeophtheirus is herein described based on female specimens collected from plankton samples in waters off Bahía Wafer, isla del Coco, an oceanic island in the Eastern Tropical Pacific. The new species, L. alvaroi sp. nov., has some affinities with other congeners bearing a relatively short abdomen, a wider than long genital complex and a 3-segmented exopod of leg 4. it differs from most of these species by the presence of an unbranched maxillular process and by the relative lengths of the terminal claws of leg 4, with two equally long elements. it is most closely related to two other Eastern Pacific species: L. dissimulatus Wilson, 1905 and L. clarionensis Shiino, 1959. it differs from these species by the proportions and shape of the genital complex, the shape of the sternal furca, the relative length of the maxillar segments, the absence of a pectiniform process on the distal maxillar segment, the length of leg 4 and the armature of leg 5. The new species represents the first Lepeophtheirus described from Costa Rican waters of the Pacific. The low diversity of this genus in this tropical region is explained by its tendency to prefer hosts from temperate latitudes. Until further evidence is found, the host of this Lepeophtheirus species remains unknown.
Entre los varios grupos de copépodos que son parásitos de teleósteos, la familia sifonostomatoide Caligidae incluye los más dispersos y diversos. Con más de 108 especies nominales, el género de calígidos Lepeophtheirus von Nordmann es uno de los más diversos. No existen registros previos de este género en aguas de Costa Rica. Se describe una nueva especie de copépodo calígido del género Lepeophtheirus con base en especímenes femeninos recolectados a partir de muestras de plancton en aguas de Bahía Wafer, isla del Coco, una isla oceánica del Pacífico Tropical Oriental. La nueva especie, L. alvaroi sp. nov., tiene algunas afinidades con congéneres que poseen un abdomen relativamente corto, un complejo genital más ancho que largo y un exópodo de la pata 4 con 3 segmentos. Esta especie difiere de la mayoría de estas especies por la presencia de un proceso maxilular no ramificado y por el tamaño relativo de las garras terminales de la pata 4, con dos elementos igualmente largos. Está más cercanamente relacionada con otras dos especies del Pacífico Oriental: L. dissimulatus Wilson, 1905 y L. clarionensis Shiino, 1959. Difiere de estas especies por las proporciones y forma del complejo genital, la forma de la furca esternal, la longitud relativa de los segmentos maxilares, la ausencia de un proceso pectiniforme en el segmento maxilar distal, la longitud de la pata 4 y la armadura de la pata 5. La nueva especie representa el primer Lepeophtheirus descrito en aguas del Pacífico de Costa Rica. La baja diversidad del género en esta región tropical se explica por su tendencia a preferir hospederos de latitudes templadas. Hasta encontrar más evidencia, el hospedero de esta especie de Lepeophtheirus permanece desconocida.
Palabras clave: crustáceos parásitos, zooplancton, diversidad, copépodos, nueva especie, Isla del Coco, Costa Rica ]]>
Caligids are the most widely distributed group of siphonostomatoid copepods in the world seas (Ho et al. 2000, Boxshall & Halsey 2004). Lepeophtheirus von Nordmann is the second most diverse genus of the family Caligidae; the most ]]>
Caligus Müller, which contains more than 250 species. Currently, it is known to contain 108 nominal species (Ho et al. 2001). Morphologically, this genus is characterized by the lack of lunules, a three-segmented exopod of the fourth leg, and the presence of a postantennary process (Ho & Lin 2004). Members of this genus are known as parasites of a wide variety of teleosts and elasmobranchs (Kabata 1979, Cressey & Cressey 1980, Ho & Lin 2004) and one species, L. ]]>
Krøyer, is deemed as the most serious parasite of farmed fish (Jackson & Minchin 1992; Johnson et al. 2004).
Caligid copepods attach themselves to the cavity of the mouth, the gills, and the operculum of their hosts (Boxshall & Montú 1997). However, adult caligids can also be found in the water column and some species are known only from plankton ]]>
Caligus and Lepeophtheirus, appear to have a well-defined tendency to distribute at different latitudes. The former genus is clearly more diverse in tropical waters and Lepeophtheirus parasitizes mainly fishes from temperate-cold latitudes (Ho & Lin 2004, Muñoz & Olmos 2007). There are only a few works dealing with the caligid fauna of the Eastern Tropical Pacific and only a reduced number of species of this ]]>
L. dissimulatus Wilson, 1905, L. parvus Wilson, 1908, L. clarionensis Shiino, 1959, L. thompsoni Baird, 1850, and L. simplex Ho, Gómez & Fajer-Avila, 2001 (Wilson 1905, Shiino 1959, Causey 1960, Ho et al. 2001).
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As a part of a biological survey of the marine biota of the oceanic island isla del Coco, Costa Rica, zooplankton samples were recorded at different sites and environments around this protected area (Morales-Ramírez 2008). During the examination of these samples female specimens of a species of Lepeophtheirus were observed. This caligid copepod was found to represent a new species, which is ]]>
Materials and methods
During the last week of November, 2001 an oceanographic cruise was carried out in neritic and oceanic ]]>
Results
Order Siphonostomatoida Thorell, 1859 Family Caligidae ]]>
Genus Lepeophtheirus von Nordmann, 1832
Description of female: Body (Figs. 1A, 2A) lengths of two specimens: 2.28mm (holotype) and 2.16mm (paratype), excluding setae on caudal rami. Cephalothoracic shield ]]>
Fig. 1H). Caudal ramus small, subquadrate, 70µm long and 85µm wide, carrying 6 elements: short inner seta as long as ramus, 3 long terminal setae plus two short outer setae (Fig. 1H), the outermost about 2.5 times as long as ramus (Figs. 1H, 2G). ]]>
Antennule (Fig. 1B) 2-segmented; proximal segment with shallow, incomplete suture on dorsal surface, segment armed with 26 plumose setae on frontal surface; second segment with 11 setae plus 2 aesthetascs on distal margin. Antenna 3-segmented (Fig. 1C); proximal segment largest, robust, with ]]>
Fig. 1C). Sternal furca with large, subtriangular box and moderately divergent and distally blunt tines (
Fig. 1D). Maxillule (Fig. 1E) comprising slender, unbranched pointed process, proximal papilla bearing 2 equal setae and one long seta. Two additional papillae with branched setal elements on medial proximal position. Maxilla (Fig. 1F) 2-segmented; proximal segment (lacertus) unarmed; distal segment (brachium) slender, slightly longer than first segment. Brachium without ornamentation or armature on outer edge, with 2 unequal elements (calamus and canna) terminally. ]]>
Fig. 1G) 3-segmented; proximal segment (corpus) largest but unarmed; middle and distal segments partially fused to form strong, sharply pointed claw with short medial spiniform seta.
Armature on rami of legs 1-4 as follows (Roman numeral indicating spines and Arabic numeral, setae): ]]>
Leg 1 (Figs. 1I, 2A) protopod with short plumose outer seta and inner seta; endopod represented by short ]]>
Fig. 1I). First segment of exopod longest, with short spiniform seta on outer distal corner; inner margin with row of short and medium-sized setules. Second segment about half the length of first one, middle 2 of 4 terminal elements on last exopodal segment with accessory setal processes (Fig. 2A); 3 curved subequal setae on medial margin. Leg 2 (Fig. 2B) with small coxa armed with large ]]>
Fig. 2C). Leg 3 (Fig. 3D) protopod (apron) with narrow marginal membrane, posterior edge with small, plumose setae at distal outer and distal inner corners. Both rami 2-segmented; exopodal spine on proximal segment robust. Two subdistal elements on third exopodal segment curled. Leg 4 (Fig. 2E) protopod with short, plumose outer seta ]]>
Fig. 2F). Leg 5 represented by a broad rounded plate armed with three biserially plumose setae and an isolated papilla bearing a single plumose seta at posteroventral corner of genital complex (Fig. 2G).
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Type material: holotype: adult female collected from the plankton at Bahía Wafer, isla del Coco, Costa Rica, coll. J. Picado, November 4, 2001, specimen partially dissected, slide with appendages sealed with Entellan ®, specimen ethanol-preserved, vial (MZUCR-283501). Paratype: adult female from same locality and date, specimen undissected, ethanol-preserved, vial deposited in ECO-CHZ-07567.
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Male: Unknown. Host: Unknown. Type locality: Bahía Wafer, isla del Coco, Costa Rica (5°32´N, 87°04’W), in the Eastern Tropical Pacific Ocean. Temperature ]]>
Etymology: This species is named after Dr. Alvaro Morales-Ramírez (CiMAR-University of Costa Rica), a Costa Rican zooplanktologist who has encouraged, for many years, different kinds of surveys of the planktonic fauna of Costa Rica and Central America.
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Remarks: The specimens examined herein were identified as belonging to the genus Lepeophtheirus because of the absence of lunules, the anterior margin of the cephalothorax is not folded, and its possession of a three-segmented exopod of the fourth leg (Ho & Lin 2004). There are many species of Lepeophtheirus (more than 50) with a relatively short abdomen (Castro & Baeza 1981) as in the new ]]>
L. exilipes Ho & Lin, 2003, L. atypicus Lin, Ho & Chen, 1996, L. goniistii Yamaguti, 1936, L. lagocephali Pillai, 1963, L. rotundipes Dojiri, 1979, and L. erecsoni Thompson, 1891.
Lepeophtheirus gonistii has a characteristic forked spine on the first exopodal segment of female leg 4, a structure which is simple in the new species. In both L. erecsoni and L. lagocephali the terminal claws of leg 4 decrease in length from the inner to the outer margin (Dojiri 1979, Boxshall & Bellwood 1981), thus differing from the new species. In
L. rotundipes the general habitus and the shape and proportions of the genital complex are different (see Dojiri 1979, Fig. 2G). The postantennal processes are relatively straight in L. alvaroi sp. nov. and strongly curved in L. rotundipes, the maxillule in L. rotundipes is ]]>
L. rotundipes whereas it is more V-shaped in the new species. In both L. exilipes and L. atypicus, with equally long middle and inner terminal claws of leg 4, the genital somite is produced posteriorly on both sides of the abdomen (Ho & Lin 2004), a character absent in the new species; also, in both species the second maxillar segment has a ]]>
L. alvaroi sp. nov., which has a simple process (Fig. 1E). Another Pacific species with a general resemblance with L. alvaroi sp. nov. is L. mugiloidis Villalba & Durán, 1985, both have similar ]]>
L. mugiloidis, a bifid maxilla, a reduced first exopodal spine of leg 4, and a sternal furca with clearly wider tines than in the new species (see Villalba & Durán 1985). ]]>
There are two other species, both known also from the Eastern Tropical Pacific, that have the same general combination of characters including, most importantly, an unbranched maxillular process and a similar structure and armature of leg 4, with the middle claw as long as the inner one. These are L. dissimulatus Wilson, 1905 and L. clarionensis ]]>
L. alvaroi sp. nov. in the following characters: the length/width ratio and shape of the genital complex is different in both species; in L. dissimulatus the genital complex is relatively larger than in L. alvaroi sp. nov. and only slightly longer than wide; the abdomen is clearly shorter than in the new species (see Shiino 1959, fig.15A). This species is easily ]]>
Fig. 1A). Also, in L. dissimulatus the middle seta of the fifth leg is clearly shorter than the other two (see Castro & Baeza 1981, fig 6) vs. a middle seta equal to the outer one in the new species (Fig. 2G). ]]>
Lepeophtheirusclarionensis Shiino, 1959 from isla Clarión, a Mexican Pacific oceanic island, is probably the most similar to L. alvaroi sp. nov. Like the new species, it has a short abdomen, an unbranched maxillular process and a leg 4 with two exopodal elements (inner and middle ones) of the same size (see Shiino 1959, figs.14C, K). it ]]>
L. alvaroi sp. nov.; it is also clearly larger, about half as wide as the cephalothorax whereas this structure is about 1/3 as wide. The cephalothorax has a different shape in both species; it is more robust and widest at its distal 1/3 in the new species, whereas it is relatively uniformly wide in L. clarionensis (see Shiino 1959, fig. 14A). Legs 4 are longer in our specimens from isla del ]]>
L. clarionensis, barely reaching beyond half length of the genital complex (Shiino 1959, fig. 14A). The first segment of the maxilla is shorter than the second segment in L. clarionensis (Shiino 1959, fig.14D) whereas it is relatively longer in the new species. Also, the fifth leg is armed with a single seta (see Shiino 1959, fig.14M) vs. a set of three setae in L. ]]>
sp. nov. (Fig. 2G).
Overall, it is concluded that the new species has a unique combination of diagnostic characters that includes: rounded genital complex without posterior processes, a short, 1-segmented abdomen less than half the length (about 25%) of the genital complex, a simple, unbranched maxillular process, first segment of maxilla longer than ]]>
Discussion
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The host of this species remains unknown, it was recorded in plankton samples; many caligids are found in the water column and this has been deemed as a possible, little known life mode of these parasites (Venmathi Maran & Ohtsuka 2008). Some species, such as Caligusundulatus Shen & Li, 1959 have been recorded only from the plankton. This also may be the case for the specimens reported herein. ]]>
Lepeophtheirus have been recorded in many different teleost families, and in the Eastern Pacific hosts include species belonging to Sciaenidae, Tetraodontidae, Balistidae, Labridae, and Serranidae (Shiino 1959, Causey 1960, Ho et al. 2001).
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Most species of Caligus have been found to parasitize mainly warm water fishes distributed in low latitudes; contrastingly, members of Lepeophtheirus are found mostly on fish from cold water at higher latitudes. Hence, despite being the second most speciose group of the Caligidae, the diversity of this genus in tropical areas tends to be low, i.e., only three species have been recorded in waters of Taiwan vs. 34 of Caligus (Ho & Lin ]]>
Caligus in Brazilian waters (Boxshall & Montú 1997, Luque & Tavares 2007). The same tendency is true in the Eastern Tropical Pacific; Shiino (1959) reported 8 species of Caligus and 3 of Lepeophtheirus and Causey (1960) 8 vs. 2 species, respectively. in Chilean waters, at lower and intermediate latitudes of the South Pacific, the number of species of these genera is almost equal (12 Caligus vs. 11
Lepeophtheirus) (Muñoz & Olmos 2007).
Acknowledgments
This work was possible with the ]]>
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*Correspondencia a: Eduardo Suárez-Morales. El Colegio de la Frontera Sur (ECOSUR), Unidad Chetumal, Av. Centenario Km 5.5, Chetumal, Quintana Roo 77000, México; esuarez@ecosur.mx. Rebeca Gasca. El Colegio de la Frontera Sur (ECOSUR), Unidad Chetumal, Av. Centenario Km 5.5, Chetumal, Quintana Roo 77000, México.
1. El Colegio de la Frontera Sur (ECOSUR), Unidad Chetumal, Av. Centenario Km 5.5, Chetumal, Quintana Roo 77000, México; esuarez@ecosur.mx
Received 02-III-2012. Corrected 30-V-2012. Accepted 24-IX-2012.
