Research Article |
Corresponding author: Faezeh Yazdani Moghaddam ( yazdani@um.ac.ir ) Academic editor: Sanja Matić-Skoko
© 2024 Ehsan Damadi, Faezeh Yazdani Moghaddam, Mehdi Ghanbarifardi.
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:
Damadi E, Yazdani Moghaddam F, Ghanbarifardi M (2024) Taxonomic characterization of five species of emperor fishes (Actinopterygii: Eupercaria: Lethrinidae) based on external morphology, morphometry, and geographic distribution in the northwestern Indian Ocean. Acta Ichthyologica et Piscatoria 54: 115-124. https://doi.org/10.3897/aiep.54.118586
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Species of the genus Lethrinus, commonly referred to as emperor fishes, mainly distributed in the Indo–West Pacific, including the Persian Gulf and Gulf of Oman are poorly known. It is difficult to characterize them morphologically, as there are no distinguishing meristic features for the majority of species. We studied the morphological features of 65 specimens representing the genus Lethrinus to define and identify the species involved. Among the morphological characters commonly considered in this type of study, we also included new, previously undescribed characters. The results of Tukey’s post hoc HSD test for metric and meristic variables, which showed significant differences between species in ANOVA, indicate that most metric traits and the number of scale rows above the lateral line differ significantly among the five morphotypes distinguished. Principal component analysis (PCA) and discriminant function analysis (DFA) effectively showed the morphometric variation between these morphotypes. The characteristics of body depth, head length, pectoral fin length, and caudal fin length are the most distinguishing diagnostic at the species level. We determined that the collected fish specimens represented: Lethrinus borbonicus Valenciennes, 1830, Lethrinus crocineus Smith, 1959, Lethrinus lentjan (Lacepède, 1802), Lethrinus microdon Valenciennes, 1830, and Lethrinus nebulosus (Forsskål, 1775). We also confirmed their validity as distinct species. Notably, L. crocineus, previously known only from the western Indian Ocean (Africa and Socotra), is now reported for the first time from the Persian Gulf and the Gulf of Oman. Lastly, a distribution map for the Lethrinus species is included.
Gulf of Oman, Lethrinus, morphological features, new record, Persian Gulf, taxonomy
The Persian Gulf and Gulf of Oman in the northwestern Indian Ocean (NIO) are recognized as two of the largest brackish-water environments of outstanding universal value in the world (
Specimen collection. A total of 65 specimens were collected between 5 and 50 m depth along the Persian Gulf and the Gulf of Oman at eight stations (Fig.
Morphometric analysis. A total of 16 morphometric traits were measured in the laboratory for each specimen. Nine meristic features were counted. Counts and measurements were taken as far as possible on the left side of the fish, following standard methods for Lethrinus taxonomy (
Ethical statement. Handling and sampling in the Persian Gulf and the Gulf of Oman were approved by the Ethic-Scientific Committee of the Ferdowsi University of Mashhad, Iran, and the Iranian Fisheries Organization (scientific permit IR.UM.REC.1400.183).
Examining Lethrinus specimens collected in the Persian Gulf and the Gulf of Oman revealed a total of five Lethrinus species. These species are L. borbonicus, L. crocineus, L. lentjan, L. microdon, and L. nebulosus. The presently reported findings of Lethrinus crocineus represent a new record for the marine fauna of the Persian Gulf and the Gulf of Oman. Below are brief descriptions of the morphometric and meristic characteristics of these species as well as univariate and multivariate analyses.
Family Lethrinidae
Genus Lethrinus Cuvier, 1829
Lethrinus borbonicus
Valenciennes in Cuvier and Valenciennes, 1830.—
Dorsal-fin rays X, 9; anal-fin rays III, 8; pectoral-fin rays13; tubed lateral-line scales 46–47; 5.5 transverse scale rows above lateral line; 15–16 transverse scale rows below lateral line; 13–15 lower series of scale around caudal-peduncle; high-bodied forms; numerous small scales on inside of pectoral fin base; molariform teeth; cheek without scales; body gray; fins mostly light brown; upper half of body darker than rest of body; posterior margin of opercular membrane gray.
Lethrinus crocineus Smith, 1959. Holotype: SAIAB 22; Paratypes: not studied; Type locality: western Indian Ocean (Mozambique: Pinda).
Dorsal-fin rays X, 9; anal-fin rays III, 8; pectoral-fin rays13; tubed lateral-line scales 46–47; 5.5 transverse scale rows above lateral line; 15–17 transverse scale rows below lateral line; 15–16 lower series of scale around caudal-peduncle; high-bodied forms; numerous small scales on inside of the pectoral fin base; molariform teeth; cheek white and without scales; body gray; fins usually yellowish, except pelvic fin.
Sciaena nebulosa
Forsskål in Niebuhr, 1775.—
Dorsal-fin rays X, 9; anal-fin rays III, 8; pectoral-fin rays13; tubed lateral-line scales 46–47; 5.5 transverse scale rows above lateral line; 15–17 transverse scale rows below lateral line; 14–15 lower series of scale around caudal-peduncle; high-bodied forms; forked caudal fin; numerous small scales on inner surface of pectoral-fin base; molariform teeth; cheek without scales; body light gray; head with light blue stripes; pale blue stripe dorsally on basal half of pectoral fin; white spots on body.
Bodianus lentjan
Lacepède, 1802.—
Dorsal-fin rays X, 9; anal-fin rays III, 8; pectoral-fin rays13; tubed lateral-line scales 46–47; 5.5 transverse scale rows above lateral line; 15–16 transverse scale rows below lateral line; 14–15 lower series of scale around caudal-peduncle; high-bodied forms; some scales on inside of pectoral fin base; molariform teeth; cheek white and without scales; body gray; pectoral and caudal fins red; inner part of pectoral fin red; posterior edge of opercular membrane red.
Lethrinus microdon
Valenciennes in Cuvier and Valenciennes, 1830.—
Dorsal-fin rays X, 9; anal-fin rays III, 8; pectoral-fin rays13; tubed lateral-line scales 47–48; 4.5 transverse scale rows above lateral line; 16–17 transverse scale rows below lateral line; 15–16 lower series of scale around caudal-peduncle; low-bodied forms; forked caudal fin; no scales on inside of the pectoral fin base; conical teeth; cheek without scales; body gray; fins brown.
Morphometrics. To characterize the morphological variation between Lethrinus species, morphometric features were analyzed. The MANOVA results showed no significant difference between males and females, the sexes were pooled in all analyses (0.0511 < P < 1.0000) (Suppl. material
Principal component analysis (PCA) results of the five of Lethrinus species samples in the presently reported study in the Persian Gulf and the Gulf of Oman; (A) morphospace plotted on 14 morphometric traits; and (B) morphospace plotted on 10 meristic traits morphometric traits; L. borbonicus (green), L. crocineus (yellow), L. lentjan (red), L. microdon (blue), L. nebulosus (black). LLS = lateral-line scales; SALL = scale rows above lateral line; SBLL = scale rows below lateral line; LSACP = scale around caudal-peduncle; SPS = supratemporal patch of scales; BD = body depth; HL = head length; POL = preorbital length; UJL = upper-jaw length; CPD = caudal-peduncle depth; CPL = caudal-peduncle length; PDL = predorsal length; PAL = preanal length; PPL = prepelvic length; LDFB = length dorsal-fin base; LAFB = length anal-fin base; LPF = length pectoral fin; LCF = length caudal fin; OD = orbit diameter [% of HL].
This study is the first univariate and multivariate analysis to determine the morphometric and meristic variation and taxonomic validation of Lethrinus fishes in the Persian Gulf and Gulf of Oman. The morphological examination of Lethrinus specimens collected from the coastal waters of the Persian Gulf and Gulf of Oman confirms the presence of the previously unreported L. crocineus in these ecoregions. The discovery of this species in the Persian Gulf and the Gulf of Oman indicates that there is a suitable habitat for L. crocineus in these ecoregions and further species of the genus Lethrinus could be discovered in the future. This species was previously known from the tropical regions of Africa and Socotra (
We would like to thank the local fishermen for their help in collecting the specimens. Financial support for this research was provided by the Ferdowsi University of Mashhad, Iran.
List of specimens
Data type: xlsx
Explanation note: Specimens, localities, accession numbers and coordinates of the five Lethrinus species used for the morphometric analysis in the Persian Gulf and Gulf of Oman.
Morphological characteristics of Lethrinus species
Data type: xlsx
Explanation note: Statistically significant for each metric and meristic characteristic among the species of Lethrinus. Measured characteristics expressed as a percentage of standard length (%SL) and head length (%HL). Asterisks indicate significant P values: *** (< 0.001).