Morphometric Characters Research Articles

Revalidation of Enteromius crocodilensis (Fowler, 1934) from synonymy with the disjunctly distributed Enteromius argenteus (Günther, 1868) based on molecular and morphological evidence.

The rosefin barb, Enteromius argenteus, as currently described, is a freshwater fish with a distribution that is geographically separated and divided into the northern population in the Kwanza River system in Angola, and the southern population in the Inkomati River system in South Africa and Eswatini. Due to this disjunct distribution pattern, it is likely that the two populations represent distinct species. mtDNA sequence data and detailed examination of morphometric characters revealed considerable genetic (2.8%-3.5%) and morphological differentiation of the two populations, suggesting their recognition as two distinct species. Enteromius crocodilensis is revalidated and redescribed for the southern population that is readily distinguished from E. argenteus by nonoverlapping circumpeduncular scale counts (12-13 vs. 14) and color pattern (presence of a conspicuous dark band along the midline vs. absence of characteristic melanin patterns). Phylogenetic analysis based on mtDNA cytochrome oxidase subunit I (COI) data places both E. argenteus and E. crocodilensis in a well-supported clade that includes a number of morphologically similar sawfin barb species from southern and central Africa.

A New Species of the Cyrtodactylus pulchellus Group (Squamata: Gekkonidae) from Surat Thani Province, Thailand Underscores This Group’s Remarkable Diversity on the Thai-Malay Peninsula

An integrative taxonomic study recognized a new species of the Cyrtodactylus pulchellus group from Kanchanadit District, Surat Thani Province, Southern Thailand. Phylogenetic analyses of the mitochondrial ND2 gene revealed a new species, Cyrtodactylus kanchanaditsp. nov., that is closely related to C. lekaguli. The new species differs from its sister lineage by bearing mean genetic divergence of 4.53% and significant differences in both mensural and morphometric characters (p < 0.05). Cyrtodactylus kanchanaditsp. nov. can be differentiated from the remaining members of the C. pulchellus species group because of its genetic divergence of ≥7.99% and a combination of differences in body size: 11–15 supralabial and 10–12 infralabial scales, 29–35 paravertebral tubercles, 18–23 longitudinal rows of dorsal tubercles, 32–37 rows of ventral scales, 20–23 subdigital lamellae on the fourth toe, 32–37 femoroprecloacal pores in adult males, and four or five dark body bands; weak tuberculation on body; absence of tubercles in the ventral body fold, absence of precloacal pores in females, and absence of scattered pattern of white tubercles on dorsum; presence of precloacal groove depression; and maculated white caudal bands. Cyrtodactylus kanchanaditsp. nov. is currently known from its type locality.

Molecular and morphological characterisation of Ditylenchoides anyae sp. n. (Nematoda: Anguinoidea) from Iran

Summary A new species, Ditylenchoides anyae sp. n., recovered from soil in the headland areas of non-cultivated fields in Alborz Province, Iran, is described and illustrated based on its morphological, morphometric, and molecular characters. The new species was characterised by a slender body and length of 784 (663-925) μm (females) and 667-712 μm (males), lip region continuous, stylet length 6.4 (6.0-7.0) μm, lateral fields with four incisures, and excretory pore situated 110 (82-137) μm from the anterior end, median bulb of pharynx fusiform, non-muscular, and non-valvate, isthmus elongate, slender ending at a pyriform basal pharyngeal bulb not overlapping intestine, vulva with distinct and relatively large lateral flaps, a well-developed post-vulval uterine sac, 31.3 (27-35) μm long, a female tail elongate-conoid with pointed terminus; and male with adanal bursa and spicules 21-22 μm long. The new species was characterised using the D2-D3 expansion segments of 28S rRNA, ITS rRNA, and partial 18S rRNA gene sequences. Phylogenetic analyses of the genus Ditylenchoides are given based on the analysis of these genes.

Morphological and molecular characterization of the elusive vegetative stage of the diatom Cerataulina bicornis: a new record from Indian Sundarbans

Abstract The resting spore stage of Cerataulina bicornis has been reported sporadically from the Indian Sundarbans, with one sediment core record that dates back to ∼2000 yrs. BP, but its vegetative stage has remained elusive during this entire period. The present report of its vegetative stage is a new record from this estuarine system. A comprehensive morphometric description along with molecular data of rbcL and 18s rDNA of the vegetative stage of C. bicornis is presented. The morphological and morphometric characters observed in the light microscope (LM) and scanning electron microscope (SEM) studies, along with a detailed description of the copulae, establish its distinction from other Cerataulina spp. described from different parts of the world.

Characterization of Drupe Traits in Sixty-Six Teak Candidate Plus Trees (CPTs) in Gujarat Forests of India for Enhanced Seed Collection and Fruit Production

The most valuable timber of the world i.e., teak was recognized as king of wood due to its wood quality such as durability, physical and aesthetic wood property for multiple uses. It is distributed throughout India and Southeast Asia and known for center of teak genetic diversity. It has a high demand in international market and national market due to multifarious uses. However, the natural population of Teak is decreasing in India due to anthropogenic activities, deforestation, climate change and other environmental factors. In addition, the poor seed yield per tree and extremely low seed germination rates are significant problems for the teak plantation industry and production of quality seed. Nevertheless, there are huge gap between demand and supply of industrial timber in India. This can be fulfilled by the teak plantation within agroforestry systems and degraded forest lands. Gujarat forest has natural teak populations which falls in the conjunction point of Western Ghats of India. Hence, sixty-six CPTs of teak were screened out for quality seed collection and reproduction from natural teak populations. Fruits of teak were collected from various CPTs with wide range of geographic locations in Gujarat forests of India. The drupe and stone morphometric traits were studied to capture the phenotypic and genotypic variations; to select better traits on the basis of repeatability coefficient; and to look geographic location effect on various fruit characters and inter-character correlations for quality seed collection and fruit production. Present result showed significant differences (p≤ 0.0001) in all the studied fruit traits among 66 CPTs of Tectona grandis. Drupe were lengthiest in GJNBD 0467 (12.36 mm), broadest in the GJNBD 0467 (14.75 mm) and heaviest in the GJAH 1056 (0.73 g) CPT, whereas smallest in GJNBD 1122 (8.3 mm), narrowest in GJNBD 1122 (9.91 mm) and lightest in GJNBD 1122 (0.32 g) CPT. Stone were longest in GJNBD 0467 (8.71 mm), thickest in GJAH 1056 (10.01 mm) and heaviest in GJAH 1056 (0.51 g) CPT, while shortest in GJNBD 1122 (6.06 mm), thinnest stone in GJNBD 1122 (7.56 mm) and lightest in GJNBD 0772 (0.22 g) CPT. Overall, GJNBD 0467, GJAH 1056, GJNBD 0950, GJAH 0844 and GJNBD 0470 CPTs were superior for studied traits as compared to others. CPT repeatability coefficient was higher for drupe characters as compared to stone parameters, where selection can be made for drupe length for future tree improvement programme. The genetic improvement via CPT selection is better option for maintaining genetic diversity of Teak, its conservation and management. Latitude showed strong negative correlation with drupe length, stone length and drupe mass. Longitude was negatively correlated with stone length and width. Thus, the geographical parameter has an impact on the seed formation, evolution and plant fitness. The strong correlations were found among seed morphometric characters which influenced to seed development and creating fitness interaction with continuous changing environment.

Quantifying phenotypic variability of indigenous chickens using morphometric traits by applying multivariate analysis: Input for sustainable rural chicken farming

Despite environmentally influenced performance traits in farm animals, variations in morphometric characters reflect unswerving genetic effects. In this study, body weight and body dimension measurements of indigenous chickens reared in four rural communities were investigated using multivariate statistical procedures to elucidate the existence of phenotypic variability between chicken populations. The study districts were selected based on higher indigenous chicken population, geographic distance, and agro-ecological distinctiveness. Eleven morphometric traits were measured on 1060 adult chickens from the districts. The results revealed that there were significant (p < 0.0001) variations between populations across districts. Significantly (P < 0.0001) higher mean values for morphometric traits were obtained in chickens reared in the Hula (highland district) than in those of the three districts. Likewise, multivariate discriminant analysis showed that most of the variables had significant power to differentiate the chicken populations into separate groups. Accordingly, three discriminant functions were extracted, of which the first two explained 95.6 % of the total variances in the populations. Moreover, in cluster analysis, chickens were differentiated into two sub-groups: Hula as a separate population, and Shebedino, Aleta Chuko and Boricha populations clustered together. Furthermore, the discriminant analysis correctly assigned 56.7 %, 55.1 %, 51.5 %, and 53.3 % to their source populations of Hula, Aleta Chuko, Shebedino, Hula, and Boricha, respectively, showing high mixing and mobility of chickens across neighboring districts. Therefore, this study confirmed the existence of significant morphometric variability between the studied populations, which could be used as a valuable source of information for selective breeding and sustainable use of indigenous chickens, particularly for rural farmers who almost rely on phenotypic features to select breeding stocks. In addition, the higher morphometric measurements shown for Hula chickens should be confirmed by on-station evaluation, and further molecular tools should be applied to validate the genetic distinctiveness of the studied chicken populations.

Integrative morphological, cytogenetic and molecular characterization of the Andean climbing catfish Astroblepus mindoensis (Regan, 1916) (Siluriformes:Astroblepidae).

Astroblepus species, commonly known as Andean climbing catfish, exhibit a unique challenge in species delimitation, leading to ongoing taxonomic debates. Here we report data on Astroblepus mindoensis, a vulnerable species endemic to Ecuador, obtained by an integrative approach that includes cytogenetic analysis, molecular identification of the specimens, and recording of morphological and morphometric characters useful for species diagnosis. Thus, this study aimed to associate the karyotype data of the specimens analyzed with morphological and molecular characters, improving and expanding the existing taxonomic information, thus contributing to the systematics of the species. Our morphology results, unlike Regan's original description, which is brief and ambiguous, provide a more detailed morphometric and meristic description. Molecular phylogenetic reconstruction and genetic distance based on a fragment of the cytochrome c oxidase subunit I (COI) showed that our samples constitute a well-supported and monophyletic clade within the A. grixalvii species complex. The cytogenetic analysis identified distinct chromosomal markers, including a single cluster of major ribosomal genes (on chromosome pair 3) and of minor ribosomal genes (on chromosome pair 12) with their localization differing from those reported in other Astroblepus species analyzed. Additionally, the presence of a heteromorphic chromosome pair in males suggests the presence of an XX/XY sex-determination system that has not been identified in other congeneric species. Further investigation is necessary to determine if these chromosomes are associated with the accumulation of repeated sequences, as typically occurs with sex chromosomes, and to assess their presence in other species of the genus.

Morphological characterization and sexual dimorphism of saw-scaled viper (&lt;em&gt;Echis&lt;/em&gt;: viperidae: ophidia) population in Sri Lanka

The Saw-scaled vipers (SSV) of the genus Echis (Viperidae: Ophidia) primarily inhabit tropics. In Sri Lanka, E. carinatus is densely populated in the Northern Province where they account for over 50% of the local snakebites. Although it was initially reported as a unique Sri Lankan subspecies named E. c. sinhaleyus, its existence was later questioned, urging the need for more detail studies. The present study examined morphological characters and sexual dimorphism in 30 specimens (17 males and 13 females) collected from Kilinochchi and Jaffna Districts in the Northern Province, using 12 mensural and 17 meristic traits, updating Deraniyagala’s report of 1951. Results showed that the adult females have longer snout to vent length (SVL) than that of males (280.34±43.32 vs. 240.88±27.03), revealing a positive sexual dimorphism index. Males had a greater TL/SVL ratio (x̄̄=13.89±0.68) than that of females (x̄̄=10.65±085). ANCOVA test retrieved most accurate and an independent significant effect of ‘sex’ on TL while SVL serving as the covariate. Males and females shared consistent meristic characters, except for number of dorsal scales at the lower part of the body, ventral and sub-caudal scales. There were more ventral scales in females (145.54±3.31) than that of males (138.41±4.08), and sub-caudal scales were higher in number in males (28.94±1.85) than that of females (25.85±2.82). Although, there were some colour pattern variations of the specimens, (head pattern and ventral pattern), they were not sex-associated and distributed evenly between males and females. This is the first study to illustrate the detail morphometric characters; mensural traits; meristic traits, and color patterns and to demonstrate the sexual dimorphism in the SSV from Sri Lanka, with noticeable differences in the snoutvent length (SVL), tail length (TL), ventral scales, and sub-caudal scales between male and female.

Bioecology of Wild Betta Fish (Betta schalleri) of Bangka Island Waters

The Betta schalleri is a wild betta fish endemic to Bangka Island which has potential as an ornamental fish. However, the fish’s endangered conservation status is one of the problems for its conservation efforts. The aim of this study was to analyze the Betta schalleri according to its biological and ecological properties. The research method was quantitative descriptive. Parameters measured in this study included fish morphology, fish meristics, water quality and habitat characteristics. The fish samples collected was 15 Betta schalleri. Observations on the physical characteristics of the Betta schalleri were based on morphometric characters, namely: 1) Total Length (TL) (22355.59 mm); 2) Standard Length (SL) (16386.74 mm);3) Head Length (HL) (3912.51 mm); 4) Head Height (HH) (3112.72 mm); 5) and Caudal Height (CH) (4922.29 mm). The meristic characters brought about the following 1) Dorsal Fin (D.II.8); 2) Anal Fin (A.II.24-25); Ventral Fin (V.I-II.4); Pectoral Fin (P.11-12); Caudal Fin (C.13) and Linea Lateralis (LL.31-32). The betta schalleri typically live in peat water, calm and fresh water that tend to be brown in color. The aquatic plants grow in the form of Pandanus sp. and Utricularia sp. In general, Betta schalleri thrive in a pH of 4-5, a temperature from 280C to 310C, and dissolved oxygen of 5.6- 11 mg/l.

Taxonomic identification of Morocco scorpions using MALDI-MS fingerprints of venom proteomes and computational modeling

The venom of scorpions has been the subject of numerous studies. However, their taxonomic identification is not a simple task, leading to misidentifications. This study aims to provide a practical approach for identifying scorpions based on the venom molecular mass fingerprint (MFP). Specimens (251) belonging to fifteen species were collected from different regions in Morocco. Their MFPs were acquired using MALDI-MS. These were used as a training dataset to generate predictive models and a library of mean spectral profiles using software programs based on machine learning. The computational model achieved an overall recognition capability of 99 % comprising 32 molecular signatures. The models and the library were tested using a new dataset for external validation and to evaluate their capability of identification. We recorded an accuracy classification with an average of 97 % and 98 % for the computational models and the library, respectively. To our knowledge, this is the first attempt to demonstrate the potential of MALDI-MS and MFPs to generate predictive models capable of discriminating scorpions from family to species levels, and to build a library of species-specific spectra. These promising results may represent a proof of concept towards developing a reliable approach for rapid molecular identification of scorpions in Morocco. Significance of the studyWith their clinical importance, scorpions may constitute a desirable study model for many researchers. The first step in studying scorpion is systematically identifying the species of interest. However, it can be a difficult task, especially for the non-experts. The taxonomy of scorpions is primarily based on morphometric characters. In Morocco, the high number of species and subspecies mainly endemic, and the morphological similarities between different species may result in false identifications. This was observed in many reports according to the scorpion experts. In this study, we describe a reliable practical approach for identifying scorpions based on the venom molecular mass fingerprints (MFPs). By using two software programs based on machine learning, we have demonstrated that these MFPs contains sufficient inter-specific variation to differentiate between the scorpion species mentioned in this study with a good accuracy. Using a drop of venom, this new approach could be a rapid, accurate and cost saving method for taxonomic identification of scorpions in Morocco.

What does external morphometry tell us about stock discrimination of Sardina pilchardus stocks from Türkiye?

The analysis of shape is a fundamental part of much biological research. Morphometrics, which incorporates concepts from biology, geometry, and statistics, is the study of the geometrical form of organisms. In addition, morphometric characteristics can be used to differentiate ‘phenotypic stocks’ as groups with similar growth, mortality, and reproductive rates. In this study, 25 morphometric characters were used to discriminate European pilchard (Sardina pilchardus) stocks from Türkiye. Intraspecific variation of the European pilchard was investigated based on morphometric characters. Samples were collected from the Aegean Sea (AS; N = 54), the Sea of Marmara (MS; N = 50) and the Mediterranean Sea (MEDS; N = 50) during the 2019 fishing season. Principal Component Analysis (PCA) and Canonical Discriminant Analysis (CDA) were used for stock discrimination of the European pilchard. Univariate statistics (ANOVA) showed that 24 of the 25 measurements differed significantly between samples to a varying degree (p &lt; 0.001). According to CDA, an overall classification success rate of 87.7% was achieved using 12 morphometric parameters. All samples were clearly separated from each other in the discriminant space, suggesting that there was no strong intermingling between populations. In addition, we would like to conclude that the morphological difference is not at the genetic level, and would like to emphasize the need for additional stock discrimination methods.

Kurbağa balığında (Chaunax abei Le Danois, 1978) Suruga Körfezi’ndeki (Japonya) tek gözlülük (tek taraflı anoftalmi)

The first case of monocularism (unilateral anophthalmia) was observed in a single specimen of Chaunax abei (Le Danois, 1978) during the seasonal trawl sampling in Suruga Bay in 2021. This occurrence marks the first reported incident of such an abnormality within the Chaunacid species. The monocularism was evidenced by photographs, and descriptive statistics of morphometric characters were presented.

Morphometric Character of Horseshoe Crab (Tachypleus) at Mempawah Mangrove Park Coastal Area, West Kalimantan, Indonesia

Abstract In Mempawah Mangrove Park (MMP) coastal area, fishers are still often catch horseshoe crabs as a bycatch. One of its genera is Tachypleus. This research aimed to assess the morphometric character of Tachypleus from MMP Coastal area, West Kalimantan. A total of 14 parameters were measured from samples that were collected using a trammel net. The sampling frequency was three times from July to September 2022. Physical and chemical parameters of the waters are also studied to support the ecological information. Two species of Tachypleus were found in these waters, i.e. Tachypleus gigas (8 males and 4 females) and Tachypleus tridentatus (6 males and 11 females). In terms of size, females were larger than males in both species. Based on morphometric comparison between females and males of T. gigas, there was a significant difference in CL/PW ratio (p&lt;0.05). On the other hand, for T. tridentatus, the ratio of PL/OL differed significantly (p&lt;0.05).

Phenetic taxonomy approach: Identifying relationship of local gelodok fish in East Java

Various natural and human factors have fragmented the populations of Mudskippers, which will disrupt their existence in the wild population, especially their mangrove habitat in East Java. Classification of relationships is identified as a first step in efforts to conserve fish outside their natural habitat. The relationship determination is based on phenetic characteristics supported by morphometric, meristic, and morphological characters. The purpose of this study was to identify the relationship of gelodok fish based on phenetic characters. The method used in the phenetic analysis is UPGMA (Unweighted pair-group using arithmetic) using NTSYSpc 2.01 software. There are four types of fish can be found in those areas, which are: Periophthalmodon schlosseri, Periophthalmus argentilineatus, Boleophthalmus pectinirostris, and Boleophthalmus boddarti. Based on the dendrogram of morphological analysis results, apomorphy A and apomorphy B were obtained, namely the Periophthalmodon schlosseri clade and the Periophthalmus argentilineatus clade with a similarity level of 90.322% and the Boleophthalmus pectinirostris clade and the Boleophthalmus boddarti clade with a similarity level of 78.494%. The relationship between the species Periophthalmodon schlosseri and Periophthalmus argentilineatus is very close with a value of 90%. While the species Boleophthalmus pectinirostris and Boleophthalmus boddarti have a closely relationship with a value of 78%. It is recommended to develop targeted conservation strategies to protect the most unique and vulnerable populations.

Morphometric Characters and Meristic Counts of Mastacembelus armatus (Lacebede, 1800) from Maruthur Anicut, Tirunelveli District, India

The present study highlights about morphometric measurement and meristic count of Mastacembelus armatus (Lacebede, 1800) collected from the Maruthur wetland ecosystem have been investigated with 23 specimens to observe the relationship between morphometric characters. Identification of species is an initial step in any research work and plays a vital role in the behavioural study. Morphometric character analysis and meristic counts are considered as simplest and authentic methods for fish species identification which is termed as morphological systematics. Fourteen different morphometric characters in percentage of total fish length (9 characters), head length (5 characters), and five different meristic counts (branched and unbranched rays) have been studied. The obtained result reveals that morphometric characters vary depending on the growth and size of the fish. However, the meristic counts were comparatively similar. All the characters show a positive correlation both in the percentage of total length and head length. The different morphometric and meristic counts of M. armatus have been analyzed for the population dynamics which includes taxonomy study and proper identification of fishes. The fin formula was calculated for some hard rays and soft rays. Therefore, this study supplement additional data for the identification of the fish species.

Linear Morphometry of Male Genitalia Distinguishes the Ant Genera Monomorium and Syllophopsis (Hymenoptera: Formicidae) in Madagascar.

Morphometric analyses of male genitalia are routinely used to distinguish genera and species in beetles, butterflies, and flies, but are rarely used in ants, where most morphometric analyses focus on the external morphology of the worker caste. In this work, we performed linear morphometric analysis of the male genitalia to distinguish Monomorium and Syllophopsis in Madagascar. For 80 specimens, we measured 10 morphometric characters, especially on the paramere, volsella, and penisvalvae. Three datasets were made from linear measurements: mean (raw data), the ratios of characters (ratio data), and the Removal of Allometric Variance (RAV data). The following quantitative methods were applied to these datasets: hierarchical clustering (Ward's method), unconstrained ordination methods including Principal Component Analysis (PCA), Non-Metric Multidimensional Scaling analyses (NMDS), Linear Discriminant Analysis (LDA), and Conditional Inference Trees (CITs). The results from statistical analysis show that the ratios proved to be the most effective approach for genus-level differentiation. However, the RAV method exhibited overlap between the genera. Meanwhile, the raw data facilitated more nuanced distinctions at the species level compared with the ratios and RAV approaches. The CITs revealed that the ratios of denticle length of the valviceps (SeL) to the paramere height (PaH) effectively distinguished between genera and identified key variables for species-level differentiation. Overall, this study shows that linear morphometric analysis of male genitalia is a useful data source for taxonomic delimitation.

Modeling and predicting meat yield and growth performance using morphological features of narrow-clawed crayfish with machine learning techniques

In recent studies, artificial intelligence and machine learning methods give higher accuracy than other prediction methods in large data sets with complex structures. Instead of statistical methods, artificial intelligence, and machine learning are used due to the difficulty of constructing mathematical models in multi-parameter and multivariate problems. In this study, predictions of length–weight relationships and meat productivity were generated by machine learning models using measurement data of male and female crayfish in the narrow-clawed crayfish population living in Apolyont Lake. The data set was created using the growth performance and morphometric characters from 1416 crayfish in different years to determine the length–weight relationship and length-meat yield. Statistical methods, artificial intelligence, and machine learning are used due to the difficulty of constructing mathematical models in multi-parameter and multivariate problems. The analysis results show that most models designed as an alternative to traditional estimation methods in future planning studies in sustainable fisheries, aquaculture, and natural sources management are valid for machine learning and artificial intelligence. Seven different machine learning algorithms were applied to the data set and the length–weight relationships and length-meat yields were evaluated for both male and female individuals. Support vector regression (SVR) has achieved the best prediction performance accuracy with 0.996 and 0.992 values for the length–weight of males and females, with 0.996 and 0.995 values for the length-meat yield of males and females. The results showed that the SVR outperforms the others for all scenarios regarding the accuracy, sensitivity, and specificity metrics.

Integrative description of two new species of the genus Mesobiotus (Eutardigrada, Macrobiotoidea) from Russia, with an updated phylogeny of the genus

In this study, we describe two new species of Mesobiotus based on morphological data collected through light and scanning electron microscopy. Descriptions include DNA sequences of four commonly used molecular markers (18S rDNA, 28S rDNA, ITS-2, and COI). Mesobiotus efa sp. nov. was discovered in North-West Russia and belongs to the group of species with smooth cuticle, harmsworthi-type OCA, typical Mesobiotus claws IV with unindented lunules, and egg chorion with reticulated processes in form of ‘sharp wide cones’ or ‘cones with long slender endings’, egg process bases with well-developed crone of dark thickenings without finger-like projections, and egg shell surface between the processes with ridges without reticulation, areolation or semi-areolation. It can be distinguished from all know species of this group by a unique combination of morphological and morphometric characters. Mesobiotus vulpinus sp. nov. was found in the Russian Far East, and is similar to Mesobiotus mauccii by having an egg chorion with polygonal relief. The new species can be distinguished from M. mauccii by having a narrower buccal tube, by details of oral cavity armature, and by longer egg chorion processes. Furthermore, we provide results of the phylogenetic analyses of the genus Mesobiotus conducted in this study.

Comparative Analysis of Morphometric and Meristic Characters in Oreochromis niloticus (Linnaeus, 1758), Nile Tilapia across Diverse Ecological Zones in Nigeria

The present study investigated the comparative analysis of morphometric and meristic characteristics in Oreochromis niloticus (Linnaeus, 1758) from six lakes in different ecological zones across Nigeria. A total of 347 samples were collected. Twenty-nine morphometric characters were measured to the nearest 0.01 cm using Vernier calipers and nine meristic characters were counted in all the collected individuals. The results of the univariate analysis of variance (ANOVA) revealed that all observed morphometric and meristic characters were significantly different (P=0.05) across the study sites. Notably, O. niloticus from Asejire Lake had significantly higher values in all the morphometric characters. The multivariate analysis of variance (MANOVA) identified three morphometric and four meristic characters as the most discriminating traits among the studied populations. These findings align with previous research highlighting the utility of morphometric and meristic data in delineating fish populations based on habitat differences and genetic compositions. Significant differences in head-related (head length), swimming-related (anal fin length and caudal peduncle length), and feeding-related (both left and right gill raker) measurements further underscored environmental influences on morphological variation. The study suggests that ecological factors such as food availability and environmental conditions contribute to the observed variations. This research provides valuable insights into the population dynamics and adaptation strategies of O. niloticus in diverse aquatic environments across Nigeria

Morphology and vocalization comparison of the Houston Toad and the Dwarf American Toad: implications for their historic range.

Documenting changes in the distribution and abundance of a given taxon requires historical data. In the absence of long-term monitoring data collected throughout the range of a taxon, conservation biologists often rely on preserved museum specimens to determine the past or present, putative geographic distribution. Distributional data for the Houston Toad (Anaxyrus houstonensis) has consistently been confounded by similarities with a sympatric congener, the Dwarf American Toad (A. americanus charlesmithi), both in monitoring data derived from chorusing surveys, and in historical data via museum specimens. In this case, misidentification can have unintended impacts on conservation efforts, where the Houston Toad is federally endangered, and the Dwarf American Toad is of least concern. Previously published reports have compared these two taxon on the basis of their male advertisement call and morphological appearance, often with the goal of using these characters to substantiate their taxonomic status prior to the advent of DNA sequencing technology. However, numerous studies report findings that contradict one another, and no consensus on the true differences or similarities can be drawn. Here, we use contemporary recordings of wild populations of each taxon to test for quantifiable differences in male advertisement call. Additionally, we quantitatively examine a subset of vouchered museum specimens representing each taxon to test previously reported differentiating morphometric characters used to distinguish among other Bufonids of East-Central Texas, USA. Finally, we assemble and qualitatively evaluate a database of photographs representing catalogued museum vouchers for each taxon to determine if their previously documented historic ranges may be larger than are currently accepted. Our findings reveal quantifiable differences between two allopatric congeners with respect to their male advertisement call, whereas we found similarities among their detailed morphology. Additionally, we report on the existence of additional, historically overlooked, museum records for the Houston Toad in the context of its putative historic range, and discuss errors associated with the curation of these specimens whose identity and nomenclature have not been consistent through time. These results bookend decades of disagreement regarding the morphology, voice, and historic distribution of these taxa, and alert practitioners of conservation efforts for the Houston Toad to previously unreported locations of occurrence.