Co-infestation of gills by different parasite groups in the mullet, Mugil platanus Günther, 1880 (Osteichthyes, Mugilidae): effects on relative condition factor

Moderate pathogenic effect of Ligophorus uruguayense (Monogenoidea, Ancyrocephalidae) in juvenile mullet Mugil liza (Actinopterygii, Mugilidae) from Brazil

Monogenoidea pathogenic activity can elicit various histological responses in fish. Species of Ligophorus are specific parasites of mullets, and its relationship with host fish may result in a moderate pathogenic action. In order to ascertain this relationship, estuarine mullets (Mugil liza) were collected in an estuary, reared in laboratory, for three weeks, and forwarded for histological and parasitological analyses. Ligophorus uruguayense (Monogenoidea) infestation in the gills of the mullets was identified. The severe infestation by only one species of Monogenoidea may result from the specificity of these parasites to mullets. Mullets submitted to histological analysis exhibited respiratory epithelium detachment; mild, moderate and severe hyperplasia of the respiratory epithelium; atrophy; and telangiectasia of the gills. This is the first study reporting that mullets highly infested by Monogenoidea can show mild (100%) to severe (20%) gill changes with a distinct frequency of occurrence. Because of the high prevalence of mild alterations observed, it is possible to accept that L. uruguayense is moderately pathogenic to M. liza, even during high prevalence and intensity of infestation, as a result of its specificity.

An ecological and comparative analysis of parasites in juvenile Mugil liza (Pisces, Mugilidae) from two sites in Samborombón bay, Argentina

ABSTRACT Mugil liza Valenciennes, 1836 is an economically important food fish and has been recommended for aquaculture in South America. A total of 278 fishes were collected in the spring and summer of 2009 and 2010. These fish were sorted into sample groups according to their size class. We used Bayesian statistics and 95% credible intervals for each parameter tested were calculated. Fish studied harbored a total of 15 different species of parasites. Diversity of parasite species found on Mugil liza was greatest at the S.R.C. collection site, but evidenced a lower species richness than at A.R. site. The 1st size fishes of both sites evidenced greater parasite diversity than either 2nd or 3rd size fish. Differences observed could be explained by the different use of habitat types at the two sites or differential susceptibility to infection by parasites. The dominance of D. fastigatainfluenced observed results of lower community diversity indexes. New works elucidating different parasite life cycles within juvenile and adults ofM. liza in Argentina, promise to be important for determining the risk of the parasitism by zoonotic metacercariae A. (P.) longa and use of this fish as food and an economic resource, and the possible use of mullet parasites in other promising fields as indicators of biodiversity, and/ or water contamination.

Fitness responses to co-infestation in fleas exploiting rodent hosts

To understand mechanisms behind positive interspecific co-occurrences in flea infracommunities, we asked whether co-infestation results in an increase of flea fitness (quantity and/or quality of the offspring). We studied reproductive performance of Xenopsylla ramesis and Parapulex chephrenis when they exploited their characteristic host (Meriones crassus and Acomys cahirinus, respectively) either alone or together with another species. We used egg production, the number of new imagoes, pre-imaginal survival and egg size as fitness-related variables and predicted that fitness will be higher in fleas feeding in mixed- than in single-species groups. In both fleas, mean number of eggs produced per female flea did not depend on experimental treatment. No effect of single- vs mixed-species infestation on the mean number of new imagoes per female and the number of emerged imagoes per egg was found for X. ramesis, whereas both these numbers were higher in mixed- than in single-species groups for P. chephrenis. X. ramesis produced eggs of similar size independently of treatment, whereas eggs produced by P. chephrenis in mixed-species groups were significantly larger than eggs produced in single-species groups. We conclude that an increase in reproductive performance as a response to co-infestation may be one of the mechanisms behind aggregative structure of flea infracommunities. However, this response may vary among flea species.

Effect of dietary supplementation with propolis and Aloe barbadensis extracts on hematological parameters and parasitism in Nile tilapia

This study evaluated the influence of diet supplementation with propolis and Aloe barbadensis on hematological parameters and parasitism in tilapia. One hundred and eighty fish were distributed among 12 water tanks forming four treatments: fish supplemented with a 1:1 mixture of 0%, 0.5%, 1% and 2% propolis and aloe extracts. After the fish had been fed on the experimental diets for 15 and 21 days, blood samples were taken and parasites collected. The monogeneans Cichlidogyrus sclerosus, C. halli, C. thurstonae and Scutogyrus longicornis were identified in the gills. Between the sampling times, there were increases in the numbers of erythrocytes, leukocytes, thrombocytes and lymphocytes, as observed after 21 days, possibly due to the stress level over the course of the assay and/or accumulation of substances in the organism. Supplementation with the mixture of propolis and aloe for 15 days showed the highest efficacy against the parasites. This was possibly due to the association between the two compounds. The results demonstrated that supplementation with mixtures of extracts did not produce hematological alterations and also favored a significant reduction in the number of gill parasites. The best results were achieved after 15 days of feeding with a diet with 0.5% and 1% supplementation with the extract mixture, which increased efficiency by 83 and 85% respectively

Nematode infection in fish from Cartagena Bay, North of Colombia

Parasitic nematode infection indices were recorded in different fish species collected at Cartagena Bay, North of Colombia. Among 19 studied species, the Mugil genus presented the highest prevalence (83.9-100%), although Sciades herzbergii, Caranx hippos and Centropomus undecimalis were also found infected with nematodes. Parasites were found in the liver, intestinal mesenteries and encysted near the intervertebral joints, with an average parasite abundance of 4.0 ± 0.3 nematodes per fish. Morphological analysis allowed the identification of these nematodes as Contracaecum sp. A small, but positive correlation was found between parasite abundance and length (R=0.294, P<0.001) and weight (R=0.244, P<0.001). In contrast, the correlation between parasite abundance and condition factor was negative (R=-0.191, P<0.001). These results are the first describing the presence of nematodes in several fish species of this ecosystem, and it highlights the need for monitoring parasitism in Mugil species in order to avoid parasite ingestion during fish consumption.

First record of Trichodina heterodentata (Ciliophora: Trichodinidae) from channel catfish, Ictalurus punctatus cultivated in Brazil

This study characterises morphologically Trichodina heterodentata Duncan, 1977 from channel catfish, Ictalurus punctatus (Rafinesque, 1818) in the State of Santa Catarina, Brazil. Body and gill smears were air-dried at room temperature, impregnated with silver nitrate and/or stained with Giemsa. Ten characteristics were selected to compare the present material with other morphological characterisations of T. heterodentata. Prevalence rate was 100%, mean intensity 89,333.70 (3,125 to 299,100 parasites per host). Trichodina heterodentata was considered medium-sized trichodinid with mean body diameter 59.4 ± 8.5 μm, denticulate ring 38.5 ± 4.5 μm, adhesive disc 60.2 ± 6.7 μm diameter and 24.4 ± 1.6 denticles. In relation to previous reports of T. heterodentata this material resembles in 90% of the analysed characters. This work confirms the biometrical variation that exists in the different populations of T. heterodentata. A list of hosts and comparative measurements of T. heterodentata are presented and the channel catfish is considered a new host.

Ligophorus saladensis n. sp. (Monogenea: Ancyrocephalidae) from Mugil platanus Günther in Samborombón Bay, Argentina

Ligophorus saladensis n. sp. (Monogenea: Dactylogyridae) is described from the gills of the grey mullet Mugil platanus Günther collected in Samborombón Bay, Argentina. The new species differs from L. mugilinus Euzet & Suriano, 1977, L. mediterraneus Sarabeev, Balbuena & Euzet, 2005 and L. huitermpe Fernandez, 1987 by the morphology of the accessory piece of the male copulatory organ and mean values derived from measurements of the sclerotised hard-parts. This is the second report of monogeneans on M. platanus in the Southwestern Atlantic Ocean region and the first description of a species of Ligophorus Euzet & Suriano, 1977 from M. platanus. Some aspects of the speciation and host-specificity of Ligophorus spp. are discussed.