Research Article |
Corresponding author: Sanny David P. Lumayno ( splumayno@up.edu.ph ) Academic editor: Wojciech Piasecki
© 2023 Sanny David P. Lumayno, Hannah Kathleen S. Labrador, Kyle Dominic E. Barnuevo, Roxanne A. Cabebe-Barnuevo, Rowena E. Cadiz, Ricardo P. Babaran.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Lumayno SDP, Labrador HKS, Barnuevo KDE, Cabebe-Barnuevo RA, Cadiz RE, Babaran RP (2023) Infection parameters of Norileca indica and a new record of Ceratothoa carinata (Crustacea: Isopoda: Cymothoidae) on Selar crumenophthalmus (Actinopterygii: Carangiformes: Carangidae) in the waters of the Sibuyan Sea, the Philippines. Acta Ichthyologica et Piscatoria 53: 147-155. https://doi.org/10.3897/aiep.53.108918
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Studies on cymothoid isopods as parasites affecting the marine fisheries and aquaculture industries are relatively scarce in the Philippines despite having detrimental impacts on their fish hosts. Parasitological examination on the bigeye scad, Selar crumenophthalmus (Bloch, 1793), a potential aquaculture species, in the waters of the Sibuyan Sea, Philippines was done on fish specimens collected on 21 April 2021. Out of the 88 specimens, a total of 13 big eye scads were infected with cymothoid isopod Norileca indica (Milne Edwards, 1840), found in the branchial cavities of the fish, resulting in a prevalence of 14.77%. A total of 20 individual isopods (13 females and seven males) were recovered, with a mean intensity of 1.53. Based on the morphological characteristics and as confirmed by the cytochrome oxidase subunit 1 (CO1) sequence, one host fish was also infected with Ceratothoa carinata (Bianconi, 1869). This appears to be the first record of C. carinata from the Philippines. To fully understand the implications of cymothoid parasites on the bigeye scad, further studies are recommended to account for the impacts of seasonality, reproductive stages of the host fish, and effects of abiotic factors such as water movement and depth.
bigeye scad, carangid, CO1, cymothoid isopod, morphology, Panay Island, parasite infection
The bigeye scad, Selar crumenophthalmus (Bloch, 1793), a potential aquaculture species, is one of the commercially important carangid fishes in the Philippines. According to the
Cymothoid isopods are parasitic in marine fishes and can infect the branchial cavity, buccal cavity, fins, and skin, or even penetrate the flesh of the host fish (
Due to the potential and economic significance of the bigeye scad in mariculture, it is essential to broaden the existing studies, particularly those on the effects of cymothoid infections in the Philippines. The study generally aimed to generate data on N. indica infections on the bigeye scad, caught in the Sibuyan Sea, Philippines. Specifically, the study assessed the prevalence and mean intensity of the N. indica. Incidentally, the study also documented the first record of C. carinata from the Philippines.
Study area and sample collection. A total of 89 bigeye scad were purchased from commercial catches landed in two fish landing sites at northern Panay Island (Kalibo, Aklan and Tangalan, Aklan), Philippines in April 2021 (Fig.
Each discovered isopod was extracted using fine forceps. Isopod samples were then measured for TL to the nearest 0.01 mm using a digital caliper, preserved in individual vials using absolute ethanol with a corresponding label, and kept in a –20°C freezer for further taxonomic and genetic identification. Morphological features included in the description were based on
DNA barcoding. Genomic DNA was extracted from the appendages of females using the Wizard Genomic DNA Purification Kit (Promega) following the manufacturer’s protocol. A targeted part of the mitochondrial cytochrome oxidase subunit 1 (CO1) gene of the specimen was amplified using the universal invertebrate primers 5′-GGTCAACAAATCATAAAGATATTGG-3′) and HC02198 (5′ TAAACTTCAGGGTGACCAAAAAATCA-3′) (
The generated sequences were compared to available sequences in GenBank by BLAST (https://blast.ncbi.nlm.nih.gov/Blast.cgi). Sequences were aligned against published sequences of known cymothoid species retrieved from GenBank to determine their phylogenetic relations using the neighbor-joining method as implemented in MEGA 7 (
Prevalence and mean intensity analyses. The prevalence and mean intensity of the isopod parasite were calculated based on
The prevalence is defined as the percentage of fish individuals infected with parasites of a given species related to the total number of fish examined, while the mean intensity specifies the total number of a certain parasite species per infected fish.
Order Isopoda Latreille, 1817
Family Cymothoidae Leach, 1814
Genus Norileca Bruce, 1990
Livoneca indica.—
Lironeca indica.—
Livoneca ornata.—
SC064 (ovigerous female): 20.75 mm TL, host Selar crumenophthalmus, Sibuyan Sea. SC064 (male): 12.26 mm TL, same data as preceding.
Four ovigerous females with a size range of 14.72–25.44 mm TL and four males with a size range of 7.17–12.26 mm TL collected from the same host, S. crumenophthalmus, captured in the Sibuyan Sea. SC020 (female): 24.24 mm TL SC020 (male): 10.71 mm TL, SC030 (female): 23.34 mm TL, SC030 (male): 11.93 mm TL, SC050 (female): 25.44 mm TL, SC050 (male): 11.77 mm TL, SC086 (female): 14.72 mm TL, SC086 (male): 7.17 mm TL.
Body twisted; dorsal surface smooth and polished appearance; ventral area soft; narrowest body part at pereonite 1; widest body part at pereonite 4. Cephalon: Triangular shape with rounded apex. Eyes: large and circular. Perionites: seven in total. Perionite 1: shortest in length. Perionites 6 and 7 narrower compared to perionites 1–5. Pleonites: narrow and positioned just behind perionite 7 overlapping with pleonite 2. Pleotelson: triangular and posteriorly pointed; dorsal surface smooth. Uropods: weak and short; visible on both sides of pleotelson in dorsal view; length not extending beyond pleotelson. Pereopods: seven pairs of soft-fleshed pereopods; pereopod 1 smallest; pereopods 2–7 gradually increasing in size. Color in preserved state: dorsal surface generally brown; anterior region light brown, transitioning to darker color towards posterior region; ventral area creamy white; pleotelson dark brown with light edges; uropods ranging from white to transparent; pereopods white.
Body size and shape: significantly smaller than females; body rather straight than twisted; dorsal surface smooth; ventral area predominantly covered with pereopods; narrowest body part at pereonite 1; widest body part at pereonite 5. Cephalon: triangular shape and rounded apex. Eyes: large and oval. Perionites: seven in total. Perionite 1 shortest. Perionites 1–4 with straight posterior margins. Perionites 5–7 with slightly concave posterior margins. Pleonites: narrow and positioned just behind perionite 7 overlapping with pleonite 1. Pleotelson: triangular and bluntly pointed; dorsal surface smooth. Uropods: weak; visible on both sides of pleotelson and nearly reaching apex of the pleotelson in dorsal view. Pereopods: seven pairs of soft-fleshed pereopods; pereopod 1 smallest; pereopods 2–4 approximately similar in size; pereopods 5–7 largest in size. Color in preserved state: dorsal surface pale brown with distinct black chromatophores; ventral area creamy white with brown coloration along edges; pleotelson dark brown with light brown edges; uropods ranging from white to transparent; pereopods white.
Order Isopoda Latreille, 1817
Family Cymothoidae Leach, 1814
Genus Ceratothoa Dana, 1852
Cymothoa carinata.—
Cymothoa (Ceratothoa) carinata.—
Meinertia carinata.—
Codonophilus carinatus.—Nierstasz 1931: 132.
Ceratothoa curvicauda.—
Ceratothoa
sp.
SC005 (non-ovigerous female) extracted from the buccal cavity of the host fish: 20.30 mm TL, host S. crumenophthalmus, Sibuyan Sea.
Body shape rectangular, maintaining straight posture; longitudinal medial ridge along dorsal pereon surface present; widest part undetermined because of slight damaged of perionite 4 and 5; narrowest part observed at perionite 1. Cephalon: subtriangular in shape with rounded and broad apex. Eyes: circular, moderately small. Perionites: seven in total, becoming narrower from perionites 5 to 7. Perionite 1: shortest; posterior margin straight; small conspicuous pointed structure extending to middle of eyes. Perionites 2–4: posterior margins straight. Perionites 5–6: posterior margins arched medially. Perionite 7: narrowest; posterior margin strongly curved medially. Pleonites: very narrow, positioned just behind perionite 7 extending to pleonite 1. Pleotelson: rather wide than long; dorsal surface with two sub-median depressions; posterior margins strongly concave. Uropods: weak; visible on both sides of pleotelson in dorsal view; similar in length to pleotelson. Pereopods: seven pairs of soft-fleshed pereopods. Pereopod 1: smallest. Pereopods 2–3: similar in size; slightly larger than previous. Pereopods 4–7: gradually increasing in size. Pereopods 5–7: largest. Color in preserved state: dorsal surface generally brown; anterior region white to brown, transitioning to darker color towards posterior region; ventral area light brown; pereopods white.
The morphological identification of the recovered parasites was confirmed by molecular analysis. Sequence analysis based on the mitochondrial CO1 gene showed a high sequence similarity (more than 99%) of SC30 and SC064 to N. indica. The phylogenetic tree showing the relation of this study’s specimens with other relevant cymothoid species is shown in Fig.
Neighbor-joining method used to estimate the phylogenetic relations among Cymothoidae based on mitochondrial CO1 sequence. Bootstrap probabilities are indicated near the nodes. Penaeus merguiensis AF279838 was used as outgroup.
On the other hand, specimen SC005 showed greater than 98.00% sequence similarity with C. carinata confirming the morphological identification. To our knowledge, this is the first record of C. carinata in the Philippines. Phylogenetic analysis based on mitochondrial CO1 genes also showed the clustering of the detected Isopoda with C. carinata LC724050.1, LC724049.1 recovered from Decapterus maruadsi (Temminck et Schlegel, 1843) in Sagami Bay, Kanagawa Japan (
In this study, 88 out of 89 bigeye scad specimens (as one fish contained C. carinata; specimen was not included in the analyses) of the bigeye scad collected during the month of April 2021 were examined, 13 individuals were found to have been infected with N. indica, leading to a prevalence of 14.77%. Of the 13 infected fish, 20 individual isopods (13 females and seven males) were extracted, resulting in a mean intensity of 1.53. All the female N. indica were extracted in the branchial cavities with their orientations mirroring the side of the branchial gill they attached to. Each male N. indica was seen along with the female isopod occupying the same gill holobranch on seven individuals of bigeye scad.
In the presently reported study, we determined the presence of N. indica on the bigeye scad caught from the Sibuyan Sea in April 2021 for the first time. To date, there have only been two existing studies on the prevalence and mean intensity of N. indica on the bigeye scad from the Philippines. The mean intensity of N. indica infection in the bigeye scad indicates the parasite load of an infected fish to be around one to two per host fish examined as also observed by
Aside from N. indica, the presently reported study also collected a single specimen of another cymothoid parasite in the bigeye scad. The collected parasite was identified as C. carinata by its pleotelson which is rather wide than long with a concave posterior margin, subtriangular cephalon, and narrow pleonite. The identification was also confirmed by its CO1 sequence. Similar to the report of
Additionally, this study presents the first molecular characterization of cymothoid parasites infecting wild fish from the Philippine waters. DNA barcoding of N. indica and C. carinata using the sequence of the mitochondrial CO1 gene generated a 680-bp amplicon which confirmed their morphological identification. Phylogenetic analysis of the sequences obtained in this study showed a close relation with N. indica isolates from India and Mozambique and C. carinata recovered in Japan. The use of DNA-based tools such as DNA barcoding in species identification is particularly helpful in the taxonomic studies of the family Cymothoidae as differentiating species under the family according to their morphological features appears to be challenging (
The presently reported study contributes to the limited data on parasites found in the bigeye scad from the Philippines, specifically N. indica and C. carinata as the first record of occurrence. Comprehensive studies are recommended to examine the physiological impacts of parasitism on bigeye scads at various life and reproductive stages, as well as in different seasons and fishing grounds throughout the country. Moreover, investigating mechanisms related to parasitism, host vulnerability, and immunity would be valuable, considering the potential of the bigeye scad as a species for aquaculture.
We gratefully acknowledge the research funding support of the Emerging Interdisciplinary Research (EIDR) Program from the Office of the Vice President for Academic Affairs (OVPAA), University of the Philippines (OVPAA-EIDR-C08-011-R) and the University of the Philippines Visayas Office of the Vice Chancellor for Research and Extension (SP20-13). We also thank the persons involved in the sample collection. We are also grateful to Christian C. Morales of the University of the Philippines Visayas Fisheries and Otolith Research Applications Laboratory of the College of Fisheries and Ocean Sciences for the map generation.