Traditional and Geometric Morphometry Analyses of Lutzomyia cruciata (Diptera: Psychodidae: Phlebotominae) Populations of Chiapas, Mexico

Geometric morphometric analysis of plastinated brain sections using computer-based methods: Evaluating shrinkage and shape changes

BACKGROUND

Plastination preserves biological specimens for long-term and geometric morphometry analyzes shape differences with advanced statistical methods. This study primarily aimed to statistically quantify shrinkage in brain sections following plastination. The secondary goal was to present the shrinkage occurring in both tissues and cavities of specific anatomical structures using geometric morphometry.

METHODS

Fourteen sections from each of nine male bovine brains underwent silicone plastination using the standard technique, which involves four stages: fixation, dehydration, forced impregnation, and curing. The shrinkage percentage in plastinated sections was measured using ImageJ, while geometric morphometry was used for shape analysis. Correlation analysis was performed to reveal the relationship between ventricle area and shrinkage percentage.

RESULTS

Significant shrinkage was observed in each brain section. A positive correlation was observed between the shrinkage on the sections and ventricular area. However, with the exception of sections number 2, 5, 9, 12 and 13, this correlation was not statistically significant for the remaining sections. Using geometric morphometric, shrinkage, and associated shape variations in specific anatomical regions within the serial brain sections were illustrated with visual graphics. Shape analysis revealed the most pronounced shrinkage in the sulcus coronalis, sulcus suprasylvius rostralis, ventral surface of the thalamus, and the third ventricle. Additionally, the cornu ammonis (hippocampus) exhibited the most significant shrinkage and shape variation. While morphometric analyses did not reveal significant shrinkage in cavity-like structures, geometric morphometric analyses demonstrated significant shrinkage in the third ventricle.

CONCLUSIONS

This study is unique in that it is the first to comprehensively demonstrate, using geometric morphometry, the morphological changes that occur in brain tissue during plastination. The findings, when combined with graphical and statistical data analysis, emphasize the effectiveness of geometric morphometry as a powerful tool for elucidating shape changes in plastination research.

Hidden diversity in anthropophilic sand flies of the Monticola Series (Diptera, Psychodidae)

The Monticola series comprises two anthropophilic and widely distributed species in Brazil: Pintomyia (Pifanomyia) monticola (Costa Lima, 1932) and Pintomyia (Pifanomyia) misionensis (Castro, 1959). They mainly occur in the Atlantic Rainforest, and it is known that Pi. monticola comprises at least two well-structured genetic lineages regarding a fragment of the cytochrome c oxidase subunit I (COI) gene. Here, we aim to elucidate the taxonomic status of this group using integrative taxonomy tools. Collections were performed in nine localities of four Brazilian states, and COI fragments were sequenced and merged with publicly available data. Several single-locus species delimitation algorithms, genetic distance metrics, phylogenetic trees, and haplotype networks were used to uncover cryptic diversity and population structure within Pi. monticola and Pi. misionensis. The resulting genetic clusters were then tested for morphological differences through linear and geometric morphometry of several characters. We analyzed 152 COI sequences, comprising 48 haplotypes. The maximum intraspecific p distances were 8.21% (mean 4.17%) and 9.12% (mean 4.4%) for Pi. monticola and Pi. misionensis, respectively, while interspecific ones ranged from 10.94 to 14.09% (mean 12.33%). Phylogenetic gene trees showed well-supported clades for both species, with clear structuring patterns within them. Species-delimitation algorithms split our dataset into at least three putative species for each taxon. Moreover, population structure analysis showed a strong correlation between Atlantic Forest areas of endemism as sources of molecular variation in Pi. monticola. Morphometric analyses were significant for wing shape variation and some linear measurements (mainly of the head) when comparing specimens of different genetic clusters for both taxa. These results indicate strong genetic structuring of Monticola series species, confirmed by morphometry, indicating two possible cryptic species complexes.

Morphometric analysis of the supraorbital region for sexual dimorphism: A study on Brazilian adult dry skulls

Introduction

Pelvis, long bones, and skull are good indicators of sexual dimorphism. In the skull, the supraorbital region is considered a highly sexually dimorphic part. Thus, the present study aimed to analyze the sexual dimorphism of Brazilian adult dry skulls using conventional and geometric morphometry.

Materials and Methods

Conventional morphometry was performed on 179 skulls, through the analysis of six linear measurements. For geometric morphometry, 89 skulls (right side) were selected and seven landmarks were considered. Generalized procrustes analysis, principal component analysis, and linear discriminant analysis were then carried out.

Results

All linear measurements presented differences between both sexes. Geometric morphometry showed that 77.05% of the sample variation could be explained by the first three principal components. Moreover, considering the centroid size, there was a difference in shape between the sexes. Geometric morphometry classified sex correctly in 77.32% of the skulls and conventional morphometry from 60.89% to 73.74%.

Conclusions

According to the analyses, the supraorbital region presents significant sexual dimorphism in Brazilian adult dry skulls. Moreover, it can be analyzed efficiently by both conventional and geometric morphometry, although the latter seems to be slightly more accurate.

Molecular and morphometric study of Brazilian populations of Psychodopygus davisi

In this study, we analysed the molecular and morphometric differences of several populations of the putative sand fly vector Psychodopygus davisi (Root, 1934) (Diptera, Psychodidae, Phlebotominae) in Brazil. We amplified the 658 base pair fragments of the DNA barcoding region-cytochrome c oxidase subunit 1 (COI) gene-for 57 specimens of P. davisi and three specimens of Psychodopygus claustrei (Abonnenc, Léger & Fauran, 1979). We merged our data with public sequences of the same species available from GenBank. Then, the combined dataset-87 sequences and 20 localities-was analysed using population structure analysis and different species delimitation approaches. Geometric morphometry of wings was performed for 155 specimens of P. davisi populations from the North, Midwest and Southeast Brazilian regions, analysing the differences in centroid sizes and canonical variates. Molecular analysis indicated high intraspecific genetic distance values for P. davisi (maximum p distance = 5.52%). All algorithms identified P. davisi and P. claustrei as distinct molecular taxonomic units, despite the low interspecific distance (p distance to the nearest neighbour = 4.79%). P. davisi sequences were split into four genetic clusters by population structure analysis and at least five genetic lineages using intermediate scenarios of the species delimitation algorithms. The species validation analysis of BPP strongly supported the five-species model in our dataset. We found high genetic diversity in this taxon, which is in agreement with its wide geographic distribution in Brazil. Furthermore, the wing analysis showed that specimens from the Southeast Region of Brazil are different from those in the North and the Midwest. The evolutionary patterns of P. davisi populations in Brazil suggest the presence of candidate species, which need to be validated in future studies using a more comprehensive approach with both genomic data and morphological characters.

Morphometrics of the Tropical Bed Bug (Hemiptera: Cimicidae) From Cape Coast, Ghana

Bed bugs, Cimex lectularius (L.) (Hemiptera: Cimicidae) and Cimex hemipterus (F.), have become established worldwide in recent years largely due to the development of insecticide resistance. However, limited attention has been given to ongoing morphological and macroevolutionary changes within the species and their populations, which could have implications for their control. Here, we evaluated whether bed bugs of the species C. hemipterus inhabiting different communities in Cape Coast, Ghana are undergoing segregation, which could lead to possible speciation. We also aimed to provide a morphometric description of all nymphal stages. Nine-bed bug populations of C. hemipterus were field-collected in Cape Coast and were subjected to geometric morphometric analysis. The multivariate parameters applied distinguished various populations from each of the locations, indicating the presence of morphologically distinct subpopulations of C. hemipterus. Shape-based segregation and shape changes associated with the insect pronotum (which is an important taxonomic character in the Cimicidae) were evident across the populations. Through this comparative study of C. hemipterus, we showed that possible subpopulations of this bed bug are being spread from Ghana. The nymphal stages (first-fifth) of C. hemipterus were distinguished by the length of the last three antennal segment and pronota width; such information contributes to the taxonomic knowledge of the species.

The Head of Fannia pusio (Fanniidae: Diptera) as A Novel Source of Morphometric Data for Assessing of Variation Along Geographic and Biological Lines

Fannia Robineau-Desvoidy, 1830 is the most diverse genus in the family Fanniidae (Diptera), with 288 species, many of which are include many of sanitary, economic and legal interest. The morphological homogeneity within the genus often makes species determination difficult. The best option for correct identification is to combine molecular and morphological analyses. The variation in the shape of a selection of body characters can be assessed by Geometric Morphometrics using the head as an innovative structure. Sex must be accounted for as a key covariate in this kind of study, since Fannia, as many other Diptera, has a sexually dimorphic head structure, with holoptic males and dicoptic females. Firstly, we analysed a set of Fannia sp. specimens sampled across the Iberian Peninsula (2012-2015), of which Fannia pusio (Wiedemann, 1830) was found to be the most abundant species. Our analyses provide significant morphological information. Fannia pusio exhibits clear intraspecific morphometric variation along an Iberian-wide East-West axis. A similar pattern emerged when comparing a laboratory-bred colony and wild samples.

Hidden Evolutionary Units and Its Implications on Conservation in a Vulnerable Species of a Freshwater Fish

Brycon is a fish genus in the order Characiformes, distributed from southern Mexico to the La Plata River in Argentina. Several of its species, including Brycon nattereri, are threatened with extinction or considered vulnerable because they are highly sensitive to anthropogenic factors. The decline of these species may be related to the growth of agriculture and mining in the Brazilian Cerrado region, thus their recovery requires management plans. In this study, we use morphological, chromosomal, and genetic analysis to suggest that two distinct evolutionary units exist under the same denomination B. nattereri, indistinguishable by the descriptive morphological characters of the species until the present moment and show that the population of the São Francisco River is more diverse than that of the upper Paraná River basin. These results may help with future management and conservation programs of Brycon species in the Paraná and São Francisco river basins, two major Brazilian hydrographic basins.