First molecular data for Lernaea cyprinacea (Copepoda: Cyclopoida) infesting Odontesthes bonariensis, a commercially important freshwater fish in Argentina

Abstract

Parasitic copepods of the family Lernaeidae are often found infesting freshwater fishes worldwide. They cause lernaeosis, a disease that can lead to serious pathogenic effects on their fish hosts. The most common lernaeid is the Lernaea cyprinacea, which has been widely introduced through importation of tropical fishes, e.g. cyprinids. In South America, it is one of the most common parasites both in wild and in farmed fish in the central region of Argentina. The silverside Odontesthes bonariensis is the most important fish of the sport fisheries of Argentina and one of the fish most affected by lernaeosis. Six specimens of copepods were collected from 30 specimens of O. bonariensis collected in a Pampean shallow lake (33°25'28"S 62°53'56"W) of Córdoba (Argentina). The 28S rRNA gene of L. cyprinacea was amplified by means of PCR to obtain the 28S rDNA sequence. The sequence obtained of this parasite from Argentina showed high genetic similarity with those from various geographical origins. The present study provided molecular characterization of L. cyprinacea in South America for the first time.

Morphology is not a reliable taxonomic tool for the genus Lernaea: molecular data and experimental infection reveal that L. cyprinacea and L. cruciata are conspecific

“…Although molecular data have been used in the identification of Lernaea species [10, 11, 14–16, 65, 66], previous molecular studies appear to have focused exclusively on L. cyprinacea , which is therefore the only species for which there are molecular data currently (October 2018) available in public databases. Although these also include a transcriptome [65], and the complete mitochondrial genome [66], identification of L. cyprinacea based on molecular data has been focused principally on partial sequences of two nuclear rRNA genes: 18S and 28S [11, 14–16]. This unavailability of molecular data for the remaining Lernaea species presents a major obstacle to their application as a tool for species identification [16].…”

“…[9, 10]. However, experimental infection studies put a major question mark over the validity of the prevailing taxonomy of the genus by showing that the anchor exhibits high intraspecific variation [5, 11]. For example, Harding [6] and Fryer [7] have shown that the growth and orientation of the anchor are affected by the anatomy of the host.…”

“…Although molecular data (partial sequences of 18S and 28S rRNA) have been used in the identification of Lernaea species [10, 11, 14–16], their availability remains extremely limited. To illustrate this, in December 2018 there were only 21 sequences for just two genes ( 18S and 28S ), and a mitochondrial genome sequence, all belonging to a single species, L. cyprinacea , available in the GenBank database (Additional file 1: Table S1).…”

“…In this case, the anchor of L. cyprinacea specimens developed into the adults which were similar to those described for L. gobioptera [24] and/or L. cruciata [17, 25], and not the typical form of L. cyprinacea . However, despite the fact that the evidence for its extreme variability was presented several decades ago, perhaps due to the absence of other morphological features that could be used for this purpose, the shape of the anchor remains commonly used as the most useful morphological trait, for the identification of Lernaea species [10, 11, 16, 26–29]. The issue of reliability of this trait has not been revisited in decades, and it has never been studied using a combination of experimental infection and molecular tools.…”

Guppy (Poecilia) Poeciliidae fish naturally infected with Lernaea cyprinacea parasites (Linnaeus 1758) in KSA

“…Attachment of parasites to fish is frequently associated with anemia of the fish [39] . Previous studies [9,14,16,36, recorded other fish hosts from all over the world susceptible to L. cyprinacea (Table 3).…”