Eduardo Suárez-Morales

The Tanaid Hexapleomera robusta (Crustacea : Peracarida) from the Caribbean Manatee, With Comments on Other Crustacean Epibionts

The tanaidaceans are among the most conspicuous and ecologically relevant benthic microcrustaceans in the marine realm but there are only a few records of species of tanaids associated with other marine organisms. During a long-term survey on the biology and distribution of the Caribbean manatee Trichechus manatus manatus Linnaeus in Mexican waters, parasites and epibionts were collected from 47 individuals that were captured for tagging in two bay systems. Well-established epibiotic communities of the tanaidacean Hexapleomera robusta (Moore) were found on eight of these animals; this tanaid crustacean formed patches of tubes adhered to the skin surface. Patches were distributed in different parts of the body surface but mainly along the backbone depression, the caudal zone, and on the lateral margins; in some instances they were related to clusters of barnacles. Highly significant differences of infestation rates were revealed between Chetumal Bay and Ascension Bay, the latter representing better conditions (high salinity and hydrodynamism) for tanaid invasion and settlement on the manatee. It is speculated that the tanaid is a commensal; no visible damage was found in the host and its presence was not related to skin lesions. The tanaid probably captures suspended particles as the manatee feeds. This is the first confirmed record of a symbiotic association involving a tanaid and the Caribbean manatee. The tanaid species recorded ( H. robusta ) and the harpacticoid copepod Balaenophilus manatorum (Ortiz, Lalana & Torres), have both been recorded also as epibionts of sea turtles. The tanaid has been known from sea turtles for some time, but the copepod was first recorded from a manatee and was subsequently found on sea turtles a few years later.

New species of continental cyclopoid copepods (Crustacea, Cyclopoida) from the Yucatán peninsula, Mexico

We report here on the cyclopoid copepod fauna encountered during a sampling campaign in several community wells on the Yucat n peninsula in 1997. In 18 freshwater and oligohaline localities, 13 different cyclopoid species were identified. Acanthocyclops rebecae n.sp., found in the south of Campeche, shows clear affinities with the northern vernalis-robustus cline. Two new Diacyclops species, D. pilosu s n.sp. and D. ecabensis n.sp. are described from wells near the archeological site of Tulum. Both are closely related to D. uruguayensis Kiefer, 1935 and D. hispidus Reid, 1988. Specimens of both sexes of Mesocyclops aequatorialis pescei Pesce, 1985 were collected in a deep community water well in the north of Quintana Roo. The male of this species is described for the first time. Micromorphology of the appendages revealed that this subspecies is distinctly different from all other Mesocyclops species known thus far and should be raised to specific rank. The description of Microcyclops echinatus n.sp. which seems closely related to M. elongatus (Lowndes, 1934), is based on specimens obtained in a plankton sample from Laguna Esmeralda in the center of the peninsula. Finally, some observations on two local populations of Microcylops dubitabilis Kiefer, 1934 are given.

Limnological and morphometrical data of eight karstic systems `cenotes' of the Yucatan Peninsula, Mexico, during the dry season (February–May, 2001)

The karstic nature of the Yucatan Peninsula allows the formation of natural sink-holes from the dissolution of calcareous rock. These systems are almost the only epigean source of fresh water available in this region. In spite of their biological importance, little is known about the morphometric and limnologic characteristics of these karstic systems. We measured limnological variables in eight cenotes in central Quintana Roo during February–May, 2001. Zooplankton biomass and chlorophyll a were also measured in order to determine if the behavior of primary and secondary production was related to environmental parameters. Important short-term changes were observed in nutrients (NO3−, NO2−, PO43-), biomass, and chlorophyll a. The morphometrically conditioned productivity (MCP), which evaluates the cumulative effect of several morphometric variables on production (area, maximum length, shoreline development, perimeter), showed a negative correlation with respect to zooplankton biomass, as did also both pH and temperature. Conversely, NO3− and NO2− had a positive correlation with zooplankton biomass. No correlation was found for chlorophyll a. Significant differences in NO3− (F = 61.52, p<0.001), NO2− (F = 7.36, p<0.001), zooplankton biomass (F = 17.57, p<0.001), chlorophyll a (F = 62.19, p<0.001), and conductivity (F = 497.49, p<0.001) were found among the systems. These results indicate the existence of sharp differences between these karstic systems (oligotrophic, with smaller area, deep and less productive) and non-karstic ones, (eutrophic, larger area, shallow and more productive) but are similar to previous data from other karstic systems of Mexico and other parts of the world. However, understanding of these fragile tropical systems is in the initial phase. It is necessary to increase the intensity of these studies in order to allow a full explanation of their limnological behavior.

Occurrence and histopathological effects of Monstrilla sp. (Copepoda: Monstrilloida) and other parasites in the brown mussel Perna perna from Brazil

During a parasitological survey of the brown mussel Perna perna from highly productive culture fields in the southern sector of Brazil, monstrilloid copepods were discovered in the mantle of this mytilid bivalve. Numerous specimens of endoparasitic copepods were found within nodules in the mantle of the host; they belong to an undetermined species of Monstrilla . Monstrilloid copepods were known to be endoparasitic in polychaetes and in one species of prosobranch mollusc only; their occurrence as parasites of bivalve molluscs has not been previously documented. This is also the first record of these crustaceans infecting commercial molluscs. The prevalence of Monstrilla sp. infecting the brown mussel was 25.6%. At the histological level, it was observed that the larvae induced a strong haemocytic infiltration resulting from the complete larval encapsulation within the host mantle. The effect of this monstrilloid in the cultured populations of P. perna deserves further study.

Distribution Patterns of the American Species of the Freshwater Genus Eucyclops (Copepoda: Cyclopoida)

ABSTRACT Based on the superposition of 19 individual tracks of American species of the freshwater copepod genus Eucyclops, two generalized tracks were found. The Western Amazonian track (southern Peru, eastern Brazil, and central Colombia) corresponding to the Amazonian subregion and the South American Transition Zone, and the Mesoamerican-Northwestern South American track (central Colombia, Central America, and northeastern Mexico) corresponding to the Neotropical region, the Mexican Transition Zone, and the Nearctic region. One node was found in Colombia, an area where both generalized tracks intersect. The distributional patterns of Eucyclops apparently involve two cenocrons: one Holarctic, and another Paleotropical. The Western Amazonian generalized track can be correlated with the existence of rivers that function either as barriers or dispersal passageways, the uplift of the Andes, and the presence of the Miocene “Pebas lake/wetland system.” The Mesoamerican-Northwestern South American generalized track can be associated with climate changes resulting from the uplift of North American mountain ranges, the presence of marine barriers (Isthmus of Tehuantepec and Panama) and the uplift of mountains in southern Mexico and Central America. The closing of the marine barrier represented by the Isthmus of Panama seems to have been a key event in the northward and southward dispersal of Eucyclops in the Americas.

ON THE PELAGIC COPEPOD COMMUNITY OF THE CENTRAL MEXICAN TROPICAL PACIFIC (AUTUMN, 1990)

[Zooplankton samples were collected during autumn (September, 1990) off the coasts of the Mexican state of Jalisco, northwestern Mexico, in the eastern tropical Pacific. Taxonomic analysis of the pelagic Copepoda yielded 44 species, Subeucalanus subcrassus, Temora discaudata, Undinula vulgaris, Euchaeta marina, Centropages furcatus, and Candacia catula being the overall dominant forms. Together they represented almost 75% of total copepod numbers. The influence of the North Equatorial Current, related to tropical conditions, is clear in the local community structure. Shannon-Wiener diversity was homogeneously high (over 3.2 bits/ind.) in most samples. Highest densities were recorded in the neritic zone. Overall copepod density values suggest a moderate to high productivity in the surveyed area. Station clustering showed a neritic and an oceanic facies, their limits roughly determined by the outer border of the narrow shelf. However, the coast-ocean gradient is moderate, with abundant neritic-oceanic forms, and oceanic representatives over the continental shelf. These effects may result from across-shelf mixing of neritic and oceanic water due to (1) the effect of inshore-wards wind-driven advective processes, and (2) the narrowness of the continental shelf. It is suggested that these processes favour a degree of homogeneity of the copepod community along this and other parts of the Mexican tropical Pacific. Durante el otono (septiembre de 1990) se recolectaron muestras de zooplancton en la costa del estado de Jalisco, en el Pacifico Tropical Oriental. El analisis taxonomico de los copepodos pelagicos produjo 44 especies. Las formas dominantes fueron Subeucalanus subcrassus, Temora discaudata, Undinula vulgaris, Euchaeta marina, Centropages furcatus y Candacia catula, las cuales representaron aproximadamente el 75% de los copepodos recolectados. La influencia de la corriente Nor-Ecuatorial, esta relacionada con las condiciones tropicales y es clara su influencia en la estructura de la comunidad local. La diversidad de Shannon-Wiener se considero alta (H′ = 3.2). Las maximas densidades fueron registradas en las zonas neriticas. En general, las densidades de copepodos indican una productividad moderada a alta en el area estudiada. El patron de agrupamiento de estaciones identifica un facie neritica y una oceanica; aparecen limitadas aproximadamente por el borde exterior de la estrecha plataforma continental. Sin embargo, el gradiente costero-oceanico es moderado, con abundantes formas neritico-oceanicas y oceanicas sobre la plataforma continental. Estos efectos resultan de la mezcla de agua neritica y oceanica sobre la plataforma debido a (1) procesos de adveccion inducidos por viento hacia la costa, y (2) a la estrechez de la plataforma continental. Se sugiere que ambos efectos podrian favorecer la homogeneidad de la comunidad de copepodos a largo de esta y otras zonas del Pacifico tropical mexicano., Zooplankton samples were collected during autumn (September, 1990) off the coasts of the Mexican state of Jalisco, northwestern Mexico, in the eastern tropical Pacific. Taxonomic analysis of the pelagic Copepoda yielded 44 species, Subeucalanus subcrassus, Temora discaudata, Undinula vulgaris, Euchaeta marina, Centropages furcatus, and Candacia catula being the overall dominant forms. Together they represented almost 75% of total copepod numbers. The influence of the North Equatorial Current, related to tropical conditions, is clear in the local community structure. Shannon-Wiener diversity was homogeneously high (over 3.2 bits/ind.) in most samples. Highest densities were recorded in the neritic zone. Overall copepod density values suggest a moderate to high productivity in the surveyed area. Station clustering showed a neritic and an oceanic facies, their limits roughly determined by the outer border of the narrow shelf. However, the coast-ocean gradient is moderate, with abundant neritic-oceanic forms, and oceanic representatives over the continental shelf. These effects may result from across-shelf mixing of neritic and oceanic water due to (1) the effect of inshore-wards wind-driven advective processes, and (2) the narrowness of the continental shelf. It is suggested that these processes favour a degree of homogeneity of the copepod community along this and other parts of the Mexican tropical Pacific. Durante el otono (septiembre de 1990) se recolectaron muestras de zooplancton en la costa del estado de Jalisco, en el Pacifico Tropical Oriental. El analisis taxonomico de los copepodos pelagicos produjo 44 especies. Las formas dominantes fueron Subeucalanus subcrassus, Temora discaudata, Undinula vulgaris, Euchaeta marina, Centropages furcatus y Candacia catula, las cuales representaron aproximadamente el 75% de los copepodos recolectados. La influencia de la corriente Nor-Ecuatorial, esta relacionada con las condiciones tropicales y es clara su influencia en la estructura de la comunidad local. La diversidad de Shannon-Wiener se considero alta (H′ = 3.2). Las maximas densidades fueron registradas en las zonas neriticas. En general, las densidades de copepodos indican una productividad moderada a alta en el area estudiada. El patron de agrupamiento de estaciones identifica un facie neritica y una oceanica; aparecen limitadas aproximadamente por el borde exterior de la estrecha plataforma continental. Sin embargo, el gradiente costero-oceanico es moderado, con abundantes formas neritico-oceanicas y oceanicas sobre la plataforma continental. Estos efectos resultan de la mezcla de agua neritica y oceanica sobre la plataforma debido a (1) procesos de adveccion inducidos por viento hacia la costa, y (2) a la estrechez de la plataforma continental. Se sugiere que ambos efectos podrian favorecer la homogeneidad de la comunidad de copepodos a largo de esta y otras zonas del Pacifico tropical mexicano.]

THE FRESHWATER CLADOCERA (ORDERS CTENOPODA AND ANOMOPODA) OF MEXICO, WITH COMMENTS ON SELECTED TAXA

Knowledge of the composition and distribution of the freshwater Cladocera in Mexico is still limited. All the available literature was reviewed and added to our own new records in different states of Mexico to present here a revised and updated list of the 110 species of the orders Ctenopoda and Anomopoda recorded for the country, with separate state records. Ecological, biogeographical, and taxonomic comments are made for selected taxa of the commonest neotropical groups: Sididae, Daphniidae, Bosminidae, Macrothricidae, and Chydoridae.

The introduced Asian parasitic copepod Neoergasilus japonicus (Harada) (Cyclopoida: Ergasilidae) from endangered cichlid teleosts in Mexico.

The cyclopoid copepod Neoergasilus japonicus (Harada, 1930) is recorded from three endangered or threatened fish species from southeast Mexico: the tailbar cichlid Vieja hartwegi (Taylor and Miller, 1980); the Angostura cichlid V. breidohri (Werner and Stawikowski, 1987); and the sieve cichlid C. grammodes (Taylor and Miller, 1980). This ectoparasitic copepod is considered, together with most other members of Neoergasilus, an Eastern Asian form. N. japonicus is one of the most widespread parasitic Asian copepods, as it has rapidly invaded Europe and North America, including Mexico. We estimated the prevalence, mean abundance, and intensity of infection of N. japonicus in these cichlid teleosts; our data agree with previous works stating the high prevalence of this ectoparasite. This copepod has a wide range of hosts among freshwater fish taxa, but this is only the second published report from cichlids in the Neotropical region. The three cichlids surveyed, V. hartwegi, V. breidohri, and C. grammodes, are new hosts of this copepod. Its occurrence in Mexico is attributed to different events of introduction by human agency. This is the southernmost record of N. japonicus in continental America. It is a matter of concern that this copepod is parasitizing endangered or threatened endemic cichlids in the Neotropical region. Because its high infective efficiency and ability to shift hosts, this Asian parasite is expected to spread farther southwards into Central and South America.

A REDESCRIPTION OF MOINA HUTCHINSONI, A RARE CLADOCERAN (BRANCHIOPODA: ANOMOPODA) FOUND IN REMNANTS OF A MEXICAN SALINE LAKE, WITH NOTES ON ITS LIFE HISTORY

Abstract Moina hutchinsoni Brehm, 1937, a nearctic anomopod cladoceran, was observed in shallow ephemeral ponds of the former Texcoco Lake, near Mexico City, Mexico. The type material, from Lake Winnemucca, Nevada, was considered lost; additional topotypic material could not be obtained from that locality because the site is completely dry. The species is redescribed herein based on specimens from Texcoco Lake and Border Lake, Nebraska. Specimens from these localities were compared to study the morphological variability of this species; differences were found in the cuticular hair patterns on head, body, antennules, and second antennae, in the number of feathered setae on the postabdomen, and in the structure of pectens in claws. The life cycle of this rare species was analyzed in the laboratory. In culture, diet consisted of the microalgae Ankistrodesmus falcatus (freshwater) and Chlorella sp. (marine); both algae were consumed by the cladoceran. Culture temperature ranged between 15° and 20°C, and salinity range was 5–25 g L−1. Cultured specimens were significantly larger than those from field populations. Lower temperatures correlated with a delayed first reproduction and with a longer inactive time between succeeding clutches. The wide thermal and salinity ranges tested during culturing, plus the ability of these animals to consume algae not normally found in its natural environment, suggest a euryecious character of this species in laboratory conditions that contrasts with the affinity of natural populations for high-salinity habitats. The lifespan of this species is longer than that of other moinids; it may be the longest-lived species within the Moinidae. The average clutch size ranged from 12 to 24.8 neonates; optimal environmental conditions differed for number of neonates and maximum clutch size. Loss of the natural environments (saline lakes) where this rare species has been recorded, both in Mexico and U.S.A., suggests an endangered status of this cladoceran.

DISTRIBUTION AND TAXONOMY OF THE TROPICAL AMERICAN MESOCYCLOPS G. O. SARS, 1914 (COPEPODA, CYCLOPOIDA)

The distributional and taxonomic status of the copepod genus Mesocyclops G. O. Sars, 1914, known from tropical America, is revised. Currently, the main characters to recognize species (i.e., presence/absence of a spine on the basipodite of the first trunk limb, the presence/absence of teethlike projections on the intercoxal sclerite of the fourth trunk limb, and the shape of the seminal receptacle) have not been strong enough to make a clear, confident taxonomic border between morphologically similar species. This is most evident in species belonging to the M. thermocyclopoides, the M. meridianus-brasilianus, and the M. reidae-ellipticus groups. Although some species qualify as Pantropical, Neotropical, endemic, and transitional forms, it is necessary to increase collection efforts and evaluate other morphological features in order to establish the taxonomic limits within these intrincate species groups as well as to determine the real distributional range of each. Se revisa el estado de conocimiento taxonomico y distribucion de las especies de Mesocyclops G. O. Sars, 1914 conocidas en America tropical. Actualmente, las caracteristicas morfologicas para diferenciar entre especies (vg. presencia/ausencia de una espina sobre el basipodito de la primera pata toracica, presencia/ausencia de proyecciones con forma de diente sobre el esclerito intercoxal de la cuarta pata toracica y la forma del receptaculo seminal), no han sido suficientes para marcar un limite taxonomico confiable entre especies morfologicamente similares. Esto es mas evidente en las especies que pertenecen a los grupos M. thermocyclopoides, M. meridianus-brasilianus y M. reidae-ellipticus. Por otro lado, aunque algunas especies son calificadas como formas Pantropicas, Neotropicas, endemicas y de transicion, es necesario incrementar los esfuerzos de colecta y evaluar otras caracteristicas morfologicas con el fin de establecer limites taxonomicos mas claros dentro de los grupos de especies antes senalados, asi como determinar los ambitos reales de distribucion de cada una.