Community of macroparasites of the Pacific barracuda Sphyraena ensis Jordan and Gilbert, 1882 (Perciformes, Sphyraenidae) from the north coast of Peru

Study Extent

Caleta de Zorritos, Contralmirante Villar Province, Tumbes, on the north coast of Peru (80º 40' 29” LS; 03º 40' 39'' LO.

Sampling

Prior to necropsy of this marine fish, total body length (TBL) in cm and sex (S) were recorded. The skin, oral cavity, gills, coelomic cavity, stomach, intestine, mesentery, pyloric cecum, gonads, heart, swim bladder, kidneys, liver and spleen of the fish were examined for helminths and parasitic arthropods. All macroparasites collected were preserved in 70 % ethyl alcohol (Eiras et al., 2006). For the morphological study of the macroparasites, helminths were colored in carmine acetic acid and alternatively in gomori trichrome, dehydrated at concentrations of 50%, 70%, 90% and 100% of ethyl alcohol, diaphanized in clove oil and mounted in Canada balsam (Almeida and Almeida, 2014). Parasitic crustaceans were macerated in lactic acid or lactophenol for a 24-48 h exposure time, placed on slides and observed directly under a microscope (Boxshall et al., 2015). Taxonomic classification of the macroparasites was carried out with the help of the general literature of Yamaguti (Yamaguti, 1963a) for monogeneans and Yamaguti (1963b) for copepods. The host and parasite nomenclature were corroborated in the World Register of Marine Species (Worms, 2021).

Quality Control

For the analysis of the parasitic population component, the parasitological ecological indices of percentage prevalence (P %), mean abundance (MA) and mean intensity (MI) of infection were calculated following the indications by Bush et al. (1997) and Bautista-Hernández et al. (2015). The type of strategy of each parasitic species was evaluated according to the P %, for which the species were classified as "core or central" species for species with a prevalence greater than 45 %, "secondary" species for those with a prevalence of between 10 % and 45 %, and “satellite” species for those with a prevalence of less than 10 % (Bush and Holmes, 1986).

Method steps

1. TBL of the fish was classified in ranges using the Sturges rule as the criterion to determine the number of intervals, from which the P%, MA and MI values of the parasites were calculated to evaluate the association between these parameters and the TBL. To determine the degree of association between the P% of the parasites and TBL, the Spearman correlation coefficient (rs) was used, previously transforming the P% values to arcsine square root. Pearson´s correlation coefficient (r) was used to determine the relationship of the TBL of the fish with the MA and MI of each species of parasite. To calculate the degree of association between the sex of the host and P% of each species of parasite, 2x2 contingency tables were used, using Chi square (X2) and Yates' correction (Y). The Student's t test (t) was used to compare the MA and MI of each parasite and the sex of the host. The populations of the male and female fish were subjected to the Kolmogorov-Smirnov test with the modification of Lillierfors to corroborate the normality of the data and the homocesticity of variances based on the Levene (F) test (Zar, 2014). The analysis of the parasites in relation to the TBL and the sex of the host was carried out only for the species with a P% greater than 10% (Esch et al., 1990). The alpha diversity of the macroparasite community was determined for the total fish population of males and females of S. ensis using the following indices: total richness, mean richness, Margalef, Simpson (D), Shannon (H), Equitability (J) and Chao-1 (Iannacone and Alvariño, 2013; Minaya et al., 2020a, 2020b). The Student's t test was used to compare mean richness, Shannon and Simpson. The level of significance was evaluated at a level of alpha = 0.05. The descriptive and inferential statistics were performed using the statistical package IBM SPSS Statistics 24.0. The non-metric multidimensional scaling (NMDS) technique was used to evaluate the pattern of the structure of the parasite community as a function of the abundance of parasite species, and was represented graphically. The similarity matrix was constructed using the Bray – Curtis index. We analysed the abundance of infection of each species of parasite in each host fish and its relationship with the host's sex using a multivariate analysis of similarity (ANOSIM) test, with 10,000 permutations (Minaya et al., 2020c; Paliy and Shankar, 2016). The parasite specimens collected in this study were deposited in the collection of Helminths Parasites and Related Invertebrates - HPIA, of the zoological collection of the Museum of Natural History of the Universidad Nacional Federico Villarreal - MUFV, Lima, Peru. The codes are shown in table 1. In addition, a checklist of the parasitic records of Pacific barracuda S. ensis was prepared up to June 2021. For the elaboration of the list, the summaries of scientific meetings and pre-degree theses were not considered. The scientific names of the parasite and host species were reviewed following the classification schemes of the World Register of Marine Species (WoRMS, 2021).

1. Monogenea
   rank: class
2. Chauhaneidae
   rank: family
3. Microcotylidae
   rank: family
4. Thoracocotylidae
   rank: family
5. Paramonaxinidae
   rank: family
6. Hexanauplia
   rank: class
7. Caligidae
   rank: family
8. Lernaeopodidae
   rank: family
9. Pseudocycnidae
   rank: family
10. Bomolochidae
    rank: family
11. Caligidae
    rank: family
12. Trematoda
    rank: class
13. Didymozoidae
    rank: family
14. Chromadorea
    rank: class
15. Anisakidae
    rank: family

Specimens of the S. ensis were collected from Caleta de Zorritos, Contralmirante Villar Province, Tumbes, on the north coast of Peru.