RESUMO
The sea louse Caligus rogercresseyi has become one of the main constraints for the sustainable development of salmon aquaculture in Chile. Although this parasite's negative impacts are well recognized by the industry, some novel potential threats remain unnoticed. The recent sequencing of the C. rogercresseyi genome revealed a large bacterial community associated with the sea louse, however, it is unknown if these microorganisms should become a new focus of sanitary concern. Herein, chromosome proximity ligation (Hi-C) coupled with long-read sequencing were used for the genomic reconstruction of the C. rogercresseyi microbiota. Through deconvolution analysis, we were able to assemble and characterize 413 bacterial genome clusters, including six bacterial genomes with more than 80% of completeness. The most represented bacterial genome belonged to the fish pathogen Tenacibacullum ovolyticum (97.87% completeness), followed by Dokdonia sp. (96.71% completeness). This completeness allowed identifying 21 virulence factors (VF) within the T. ovolyticum genome and four antibiotic resistance genes (ARG). Notably, genomic pathway reconstruction analysis suggests putative metabolic complementation mechanisms between C. rogercresseyi and its associated microbiota. Taken together, our data highlight the relevance of Hi-C techniques to discover pathogenic bacteria, VF, and ARGs and also suggest novel host-microbiota mutualism in sea lice biology.
Assuntos
Copépodes/genética , Copépodes/microbiologia , Ectoparasitoses/genética , Ectoparasitoses/parasitologia , Doenças dos Peixes/parasitologia , Genômica/métodos , Interações Hospedeiro-Parasita , Microbiota/genética , Salmão/parasitologia , Animais , Chile , Copépodes/patogenicidade , Genoma/genética , Tenacibaculum/patogenicidadeRESUMO
Caligus rogercresseyi, commonly known as sea louse, is an ectoparasite copepod that impacts the salmon aquaculture in Chile, causing losses of hundreds of million dollars per year. In this study, we report a chromosome-scale assembly of the sea louse (C. rogercresseyi) genome based on single-molecule real-time sequencing (SMRT) and proximity ligation (Hi-C) analysis. Coding RNAs and non-coding RNAs, and specifically long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) were identified through whole transcriptome sequencing from different life stages. A total of 23,686 protein-coding genes and 12,558 non-coding RNAs were annotated. In addition, 6,308 lncRNAs and 5,774 miRNAs were found to be transcriptionally active from larvae to adult stages. Taken together, this genomic resource for C. rogercresseyi represents a valuable tool to develop sustainable control strategies in the salmon aquaculture industry.
Assuntos
Copépodes/genética , MicroRNAs/genética , RNA Longo não Codificante/genética , Transcriptoma , Animais , Cromossomos , Copépodes/patogenicidade , Doenças dos Peixes/parasitologia , Estágios do Ciclo de Vida/genética , Salmão/parasitologiaRESUMO
Chemical signals are a key element of host-parasite interactions. In marine ecosystems, obligate ectoparasites, such as sea lice, use chemical cues and other sensory signals to increase the probability of encountering a host and to identify appropriate hosts on which they depend to complete their life cycle. The chemical compounds that underlie host identification by the sea lice are not fully described or characterized. Here, we report a novel compound - the Atlantic salmon (Salmo salar) antimicrobial peptide cathelicidin-2 (Cath-2) - that acts as an activation cue for the marine parasitic copepod Lepeophtheirus salmonis. L. salmonis were exposed to 0, 7, 70 and 700 ppb of Cath-2 and neural activity, swimming behaviour and gene expression profiles of animals in response to the peptide were evaluated. The neurophysiological, behavioural and transcriptomic results were consistent: L. salmonis detects Cath-2 as a water-soluble peptide released from the skin of salmon, triggering chemosensory neural activity associated with altered swimming behaviour of copepodids exposed to the peptide, and chemosensory-related genes were up-regulated in copepodids exposed to the peptide. L. salmonis are activated by Cath-2, indicating a tight link between this peptide and the salmon louse chemosensory system.
Assuntos
Peptídeos Catiônicos Antimicrobianos/genética , Copépodes/patogenicidade , Salmo salar/genética , Animais , Anti-Infecciosos , Copépodes/genética , Doenças dos Peixes , Interações Hospedeiro-Parasita/genética , Salmo salar/parasitologia , Pele/parasitologia , Transcriptoma , CatelicidinasRESUMO
Cathepsins are proteases involved in the ability of parasites to overcome and/or modulate host defenses so as to complete their own lifecycle. However, the mechanisms underlying this ability of cathepsins are still poorly understood. One excellent model for identifying and exploring the molecular functions of cathepsins is the marine ectoparasitic copepod Caligus rogercresseyi that currently affects the Chilean salmon industry. Using high-throughput transcriptome sequencing, 56 cathepsin-like sequences were found distributed in five cysteine protease groups (B, F, L, Z, and S) as well as in an aspartic protease group (D). Ontogenic transcriptome analysis evidenced that L cathepsins were the most abundant during the lifecycle, while cathepsins B and K were mostly expressed in the larval stages and adult females, thus suggesting participation in the molting processes and embryonic development, respectively. Interestingly, a variety of cathepsins from groups Z, L, D, B, K, and S were upregulated in the infective stage of copepodid, corroborating the complexity of the processes involved in the parasitic success of this copepod. Putative functional roles of cathepsins were conjectured based on the differential expressions found and on roles previously described in other phylogenetically related species. Moreover, 140 single nucleotide polymorphisms (SNP) were identified in transcripts annotated for cysteine and aspartic proteases located into untranslated regions, or the coding region. This study reports for the first time the presence of cathepsin-like genes and differential expressions throughout a copepod lifecycle. The identification of cathepsins together with functional validations represents a valuable strategy for pinpointing target molecules that could be used in the development of new delousing drugs or vaccines against C. rogercresseyi.
Assuntos
Catepsinas/genética , Copépodes/enzimologia , Copépodes/patogenicidade , Doenças dos Peixes/parasitologia , Perfilação da Expressão Gênica , Salmão/parasitologia , Animais , Copépodes/genética , Copépodes/crescimento & desenvolvimento , Feminino , Masculino , Filogenia , Polimorfismo de Nucleotídeo Único , TranscriptomaRESUMO
Parasites can infect larval, juvenile or adult marine fishes; however, the effects of parasites on the growth and condition of fish larvae have seldom been investigated. This study analysed the effects of a parasitic copepod on the larval growth of the Chilean triplefin Helcogrammoides chilensis (Tripterygiidae) based on the microstructure of the sagittal otoliths. Fish larvae were collected during the austral spring of 2010 off central Chile. Their body length ranged from 5.1 to 16.6 mm (2 to 57 days old). They were parasitised by a penellid larval copepod that was always externally attached to the ventral side of the fish's gut. The prevalence of the copepod ranged from 2.7% to 20.8%, with one to four parasites per fish larva. Relationships between otolith size (radius, perimeter) and larval size were equal for parasitised and unparasitised fish larvae (P > 0.05). Larval growth was also similar for unparasitised (0.21 mm/day) and parasitised fish larvae (0.19 mm/day) (P > 0.05). However, a comparison of same-aged larvae showed that the larvae with copepods were smaller in both length and estimated body volume than the larvae without copepods. The Recent Otolith Growth Index, indicated that larval H. chilensis with copepods showed a reduction in recent growth and condition compared with those without evidence of copepods (P < 0.05). Nevertheless, a higher parasite load (two vs. one pennellids) did not decrease the condition of the larval fish. The infestation of pennellids on coastal fish larvae may therefore induce an increase in the pelagic larval duration and potentially affect the settlement rates of this intertidal fish.