Pesq. Vet. Bras. 41:e06775, 2021 DOI: 10.1590/1678-5150-PVB-6775 Original Article Wildlife Medicine ISSN 0100-736X (Print) ISSN 1678-5150 (Online)
Ultrastructural and morphometric description of the ear skin and cartilage of two South American wild histricognate rodents (Dasyprocta leporina and Galea spixii)1 Alexsandra F. Pereira2*, Leonardo V.C Aquino2, Matheus B. Nascimento2, Ferdinando V.F. Bezerra3, Alana A. Borges2, Érika A. Praxedes2 and Moacir F. Oliveira3
ABSTRACT.- Pereira A.F., Aquino L.V.C., Nascimento M.B., Bezerra F.V.F., Borges A.A., Praxedes E.A. & Oliveira M.F. 2021. Ultrastructural and morphometric description of the ear skin and cartilage of two South American wild histricognate rodents (Dasyprocta leporina and Galea spixii). Pesquisa Veterinária Brasileira 41:e06775, 2021. Universidade Federal Rural do Semi-Árido, Av. Francisco Mota 572, Presidente Costa e Silva, Mossoró, RN 59625-900, Título Original Brazil. E-mail: [email protected] Skin and cartilage have been the main source for the recovery of somatic cells to be used in conservation strategies in wild mammals. In this sense, an important step for the [Título traduzido]. cryopreservation of these samples is to recognize the properties of the skin and cartilage. Thus, knowing that the skin may differ among species and aiming to contribute to the establishment of cryobanks, the study examined the differences in the ear skin and cartilage of wild rodents from South America, agouti (Dasyprocta leporina) and spix’s yellow-toothed Autores cavy (Galea spixii). Ultrastructural and quantitative methods were used to measure skin and
and proliferative activity. Although ultrastructural analysis revealed a similar pattern cartilagebetween thickness,species, morphometric density of collagen analysis and elastic of the fibers, skin and cell cartilagetype number showed and distribution, differences between agoutis and cavies regarding thickness of epidermis layers (corneum: 5.3±2.5µm vs. 3.9±0.6µm; intermediate: 16.4±6.2µm vs. 23.4±8.1µm; basal: 9.9±2.1µm vs. 4.8±0.5µm), dermis (183.1±44.0µm vs. 258.2±22.9µm), total skin (211.8±46.0µm vs. 290.3±23.7µm) and perichondrium (27.6±6.1µm vs. 10.5±1.8µm). A greater number of epidermal cells (61.7±15.2 vs. 24.8±7.6) and chondrocytes (32.7±9.0 vs. 27.5±4.7) were observed in agouti, while the cavy presented a greater number of melanocytes (12.6±4.7 vs. 29.9±6.2), keratinocytes (14.7±4.2
vs.to the 29.8±7.6), skin of agoutis.and fibroblasts Therefore, (103.6±24.7 there are vs. differences 112.2±11.3). between Moreover, agouti a andhigher cavy percentage for ear skin of collagen fibers and proliferative activity was observed in the skin of cavies, when compared INDEX TERMS: Wild rodents, , , ultrastructure, morphology, morphometry, and cartilage, requiring theDasyprocta establishment leporina ofGalea species-specific spixii cryopreservation protocols. ear skin, cartilage, cryobanks, wildlife animals.
RESUMO.- [Descrição ultraestrutural e morfométrica da de recuperação de células somáticas a serem utilizadas em pele e cartilagem auricular de dois roedores histricognatos estratégias de conservação em mamíferos silvestres. Nesse silvestres da América do Sul (Dasyprocta leporina e Galea contexto, uma importante etapa para criopreservação é spixii)]. A pele e cartilagem têm sido uma importante fonte conhecer, inicialmente, as propriedades que compõem a pele e cartilagem. Sabendo, então, que a pele pode diferir- 1 Received on December 6, 2020. se entre espécies e com o objetivo de contribuir para o Accepted for publication on December 26, 2020. estabelecimento de criobancos, o estudo evidenciou as 2 Laboratório de Biotecnologia Animal, Universidade Federal Rural do diferenças da pele e da cartilagem do pavilhão auricular apical Semi-Árido (UFERSA), BR-110 Km 47, Presidente Costa e Silva, Mossoró, RN de cutias ( ) e preás ( ) que são 599625-900, Brazil. *Corresponding author: [email protected] Dasyprocta leporina Galea spixii 3 roedores silvestres presentes na América do Sul. Para tanto, Rural do Semi-Árido (UFERSA), BR-110 Km 47, Presidente Costa e Silva, métodos ultraestruturais e quantitativos foram utilizados para Mossoró,Laboratório RN 599625-900, de Morfofisiologia Brazil. Animal Aplicada, Universidade Federal mensurar a espessura da pele e da cartilagem, densidade de
1 2 Alexsandra F. Pereira et al.
celulares e atividade proliferativa. Embora as propriedades ultrastructure and composition of the skin and cartilage of fibrasultraestruturais colágenas e emelásticas, cutias número e preás e tenham distribuição se mostrado dos tipos cartilagesthe South American of these two rodents’ species. agouti We specificallyand spix’s yellow-toothed examined the semelhantes, avaliações acerca da morfometria da pele e cavy, for the establishment of suitable biological resource da cartilagem demonstrou diferenças, especialmente nas banks for these species. camadas epidérmicas (córnea: 5,3±2,5µm vs. 3,9±0,6µm; espinhosa: 16,4±6,2µm vs. 23,4±8,1µm; basal: 9,9±2,1µm MATERIALS AND METHODS vs. 4,8±0,5µm), derme (183,1±44,0µm vs. 258,2±22,9µm), Except where indicated, all chemicals, media, and solutions were pele total (211,8±46,0µm vs. 290,3±23,7µm) e pericôndrio purchased from Sigma Chemical Co. (St. Louis/MO, USA), Gibco- (27,6±6,1µm vs. BRL (Carlsbad/CA, USA), and Labimpex (São Paulo/SP, Brazil). de células epidérmicas (61,7±15,2 vs. 24,8±7,6) e condrócitos All experimental protocols and animal care were approved by (32,7±9,0 vs. 27,5±4,7) 10,5±1,8µm). foram observados Além disso, em um cutias, número enquanto maior the Animal Ethics Committee of the “Universidade Federal Rural do Semi-Árido” (CEUA-UFERSA, no. 23091.001072/2015-92 and no. 23091.010566/2017-20), and the “Instituto Chico Mendes de em(103,6±24,7 preás um vs. maior 112,2±11,3) número foram de melanócitos evidenciados. (12,6±4,7 Ainda, emvs. Conservação da Biodiversidade” (ICMBio; no. 48633-2 and no. 604281). 29,9±6,2), queratinócitos (14,7±4,2 vs. 29,8±7,6) e fibroblastos Eight male agoutis proliferativa foram observadas quando comparadas a pele Animals, ear cartilage, and skin collection. (Dasyprocta leporina; 8 months old) and eight male spix’s yellow- preás,de cutias. uma Portanto,maior porcentagem existem diferençasde fibras colágenas entre cutias e da atividade e preás toothed cavy ( ; 8 months old) obtained from the Center para pele e cartilagem do pavilhão auricular, exigindo desta Galea spixii for Multiplication of Wild Animals (no. 1478912) were used in this forma um estabelecimento de protocolos de criopreservação study. The animals were previously anesthetized by intramuscular
TERMOS DE INDEXAÇÃO: Roedores silvestres, , São Paulo/SP, Brazil) and 1mg/kg xylazine hydrochloride (Rompun; específica para cada uma destas espécies.Dasyprocta leporina Galea spixii, ultraestrutura, morfologia, morfometria, pele auricular, Bayer,administration São Paulo/SP, of 15mg/kg Brazil), ketamine according hydrochloride to Castelo et (Ketalar; al. (2015). Pfizer, Ear cartilagem, criobancos, animais selvagens. margin tissues (1-2cm2) were obtained using pliers and transported
supplemented with 2% antibiotic-antimycotic solution (penicillin INTRODUCTION G,to streptomycin,the laboratory and in Dulbecco’s amphotericin modified B) at 37°CEagle’s for medium 1 h. (DMEM) Agouti (Dasyprocta leporina) and spix’s yellow-toothed In the laboratory, tissues were washed in 70% ethanol, and by using cavy (Galea spixii) are histricognate rodents belonging to a scalpel blade and a cutting mold, eight fragments (9.0mm3; 3 × 3 × the Dasyproctidae and Caviidae family, respectively, and 1mm) per individual per species were obtained and were equally and distributed throughout the Brazilian territory (Silva et al. randomly allocated for ultrastructural and morphometric analyses. 2017). These animals play different roles in the functionality of Processing and ultrastructural analysis. Initially, two fragments the environment that they inhabit and are models for rodents under the threat of extinction (Praxedes et al. 2018b), since from each individual were fixed in 2.5% glutaraldehyde solution in Reid 2016). In other species, the use of an experimental model andphosphate-buffered dehydrated with saline increasing (PBS) for concentrations five days. After of this ethanol period, (Ciena tissues et theirwith populationsa stable population are stable has (Catzeflis already et been al. 2016, and interestingEmmons & al.were 2017). post-fixed For scanning in 1% osmiumelectron microscopytetroxide diluted analysis, in distilled samples water were alternative and an important tool used in animal conservation conditioned in the drying equipment to the critical point of carbon research programs (Cardoso et al. 2020, Echeverry et al. 2020). dioxide (K850 Critical Point Dryer; Quorum Technologies, Lewes, Thus, in order to respond to this demand, for the study East Sussex, United Kingdom), placed in a stub, and metallized with of these species, skin and cartilage cryobanks have been gold. Finally, tissue ultrastructure was visualized using a scanning established in recent years (Praxedes et al. 2018a, Pereira et electron microscope (TESCAN VEGA3; Tescan Analytics, Fuveau, al. 2019), since skin and cartilage somatic cells can be used Bouches-du-Rhône, France). in the multiplication of individuals using cloning (Azuma Processing and morphometric analysis using histological et al. 2018), in regenerative medicine (Aliborzi et al. 2016), staining. and genetic (Comizzoli 2017) and morphological research 4% paraformaldehyde solution in PBS for a period of seven days. After this period,Initially, tissues six were fragments dehydrated from in each increasing individual concentrations were fixed in of a a skin and cartilage cryobank is to establish a protocol for (Mariotissue cryopreservation et al. 2018). The that first results step in in theminimal establishment cell damage of sectioned in 5.0µm, according to Costa et al. (2020). All morphometric analysesethanol, diaphanized were performed in xylol, using included a light and microscope embedded (Olympus in paraffin, CX and 31 skin and cartilage similarities and differences among the RBSFA; Tokyo, Japan) and ImageJ software (US National Institutes (Machadospecies is aet determining al. 2017). Therefore, step for choosing the identification the best method of ear of Health; Bethesda, Rockville, USA). for successful cryopreservation. Sections were stained with hematoxylin and eosin (HE) according In general, protocols used in wild mammals are developed in to Costa et al. (2020), and the following parameters were examined: phylogenetically close species. In 2020, our group established epidermal, dermal, and perichondrium thickness (in µm); thickness a protocol for cryopreserving the skin and cartilage of agoutis of epidermis layers; and number and distribution of melanocytes, keratinocytes, epidermal cells (Merkel and Langerhans cells), and ethylene glycol as cryoprotectants (Costa et al. 2020). usingThus, tovitrification establish a andcryopreservation a combination protocol of dimethyl for cavy sulfoxide tissues, using agouti as the reference species, we initially aimed to fibroblasts,Other sections and chondrocytes. were stained Forwith all Gomori analyses, trichrome 20 images (GT), per according animal recognize the similarities and differences of the skins and towere Borges acquired et al. in 400×(2017) magnification, for evaluation totaling of the 160 density images ofper collagen species.
Pesq. Vet. Bras. 41:e06775, 2021 Ultrastructural and morphometric description of the ear skin and cartilage of two South American wild histricognate rodents 3
and cell numbers were analyzed by Kruskal-Wallis and Dunn tests. fibers. Briefly, in each image, an area of the2 superficial dermis2), with and percentagecollagen fibers of collagen was selected (density) where calculated the following as total areaparameters with collagen were Significance was set at P<0.05.RESULTS evaluated and compared: image area (μm ), collagen area (μm Evaluation of ear skin and cartilage using ultrastructural al. 2017). For all analyses, 10 images per animal were acquired in fibers divided by the total area of the analyzed section (Morais et analysis Using scanning electron microscopy, the ultrastructural Moreover, sections were stained with Weigert-Van Gieson iron analysis of the ear skin of these rodents proved to be similar 400× magnification, totaling 80 images per species. hematoxylin (WG; basic resorcin-fuchsin) (Hernández-Morera et al. (Fig.1A,F). The structural pattern of the skin and cartilage
evaluation of this region in the present study. Thus, about the 2017) for visualization of the density of elastic fibers. For viewing, Finally, for assessment of the cell proliferative potential using the skintissue of couldagouti be and confirmed, spix’s yellow-toothed later, from the cavy, morphological the corneum argyrophilicone image per nucleolar animal wasorganizer acquired region in 1000× (AgNOR) magnification. method, sections were placed in silver solution prepared by mixing 1 part of 2% with constant cellular detachment, was shown evident in the gelatin in 1% aqueous formic acid and 2 parts of 50% aqueous silver epidermislayer, which (Fig.1B,G). is the most On superficial, the other hand,containing for the dead delimitation cells and nitrate solution, and the slides were incubated in the dark for 30 min (Queiroz Neta et al. 2018). Subsequently, the slides were washed hair follicles (Fig.1D,I) were observed, which are structural componentsof the dermis, of thethe presenceregion. While of fiber in the bundles cartilaginous (Fig.1C,H) tissue and of solution for 10 min each. For all analyses, 10 images per animal were in 3% sodium thiosulfate solution and 3% sodium metabisulfite sites of chondrocytes, cells responsible for maintaining the For the analyses of each slide, the AgNOR dots were counted in 100 cartilaginousthese small rodents, matrix gaps (Fig.1E,J). were identified that are the insertion acquired in 1000× magnification, totaling 80 images per species. AgNOR area/cell were calculated. Evaluation of ear skin and cartilage using morphometric fibroblastsStatistical by Imageanalysis. Pro-Plus Data were software expressed AgNOR as number/cellmean ± standard and analysis error (one animal/repetition) and analyzed using the GraphPad The skin is one of the largest organs and performs numerous software (Graph-Pad Software Incorporation; La Jolla, CA, USA). functions for mammals. In this organ it is possible to show cells of great biotechnological impact and for this reason it homoscedasticity by the Levene’s test. As the data regarding the has been constantly used in recent years as an alternative for All results were verified for normality by the Shapiro-Wilk test and were arcsine transformed. Data were analyzed by ANOVA (multiple and spix’s yellow-toothed cavy morphologically showed comparisons)density of collagen followed fibers by Tukey’s did not test.show The a normal results ofdistribution, AgNOR analysis, they similarscientific characteristics. studies. Based This on is this because principle, in both the species, skin of theagoutis skin
Fig.1. Ultrastructural analysis by scanning electron microscopy of the ear skin and cartilage derived from (A-E) agoutis and (F-J) spix’s yellow-toothed cavy. (A,F) Represent and overview of the skin with its layers and cartilaginous tissue. (A) Bar = 10µm, (F) bar = 200µm. Epidermis (EP), dermis (D) and cartilaginous tissue (CT). (B,G) Represent the corneum layer (arrows) of epidermis of skin. (B) Bar = 20µm, (G) bar = 100µm. (C,H C) Bar = 100µm, (H) bar = 5µm. (D,I) Representation of the hair follicle (HF) in the skin dermis. (D) Bar = 20µm, (I) bar = 200µm. (E,J) Represent the cartilaginous tissue, where lacunae (*) are observed. Bar = 20µm. ) Representation of dermal fiber bundles (FB). (
Pesq. Vet. Bras. 41:e06775, 2021 4 Alexsandra F. Pereira et al. was composed of two layers, the epidermis and the dermis (Fig.2B,E). Additionally, in the epidermis, the unviable part known as the corneum layer was also observed, in which it layers were observed, the basal and spinosum of which make consists of dead cells, without nucleus and with a keratin- (Fig.2A,D).up the viable Specifically, portion and in the contained epidermis different of these cell rodents, types, three such rich cytoplasm, and for this reason it is called a keratinized as melanocytes, keratinocytes, Merkel and Langerhans cells
stratified epithelium (Fig.2B,E).
Fig.2. Histological analysis using HE of the ear skin and cartilage derived from (A-C) agoutis and (D-F) spix’s yellow-toothed cavy. (A,D) Represent and overview of the skin layers. HE, obj.20x, bar = 50µm. (B,E) Represent the epidermis layers and dermis. HE, obj.40x, bar = 20µm. (C,F) Represent the cartilage. HE, obj.40x, bar = 20µm. Epidermis (E), dermis (D), cartilaginous tissue (CT), muscle tissue (MT), corneum layer (CL), spinosum layer (SL), basal layer (BL), keratinocyte (triangle), melanocyte (thick arrow), epidermal cell G) Measurement of the thickness of the skin and cartilage. Bars indicate standard deviation. a,b Values with different superscripts differ (P (fine arrow), fibroblast (F), chondrocyte (C) and perichondrium (P). ( <0.05). Pesq. Vet. Bras. 41:e06775, 2021 Ultrastructural and morphometric description of the ear skin and cartilage of two South American wild histricognate rodents 5
Regarding the dermis of the skin of agouti and spix’s yellow- for nutrition, oxygenation and elimination of cellular toothed cavy, it was possible to highlight the connective tissue that the structural pattern of the skin and cartilaginous tissue to observe a clear distinction between the papillary dermis, metabolitesof agoutis and has spix’s also beenyellow-toothed identified. cavyTherefore, were similarlyconfirming as richwhich mainly is made in collagenup of recesses fibers, that although increase it was the contactnot possible zone between the epidermis, and neither the reticular dermis, which For morphometric analysis of the skin and cartilage is thicker and deeper, constituted mainly by the sebaceous previouslytissue, initially identified differences in the wereultrastructural shown in evaluation.the thickness of and sweat glands. Additionally, although in the dermis of the epidermal layers of agouti and spix’s yellow-toothed cavy agoutis and spix’s yellow-toothed cavy other cell types have (corneum: 5.3±2.5µm vs. 3.9±0.6µm; spinosum: 16.4±6.2µm vs. 23.4±8.1µm; basal: 9.9±2.1µm vs. 4.8±0.5µm), dermis the main cell type in this region. Therefore, allowing from (183.1±44.0µm vs. 258.2±22.9µm), total skin (211.8±46.0µm notthis beenstructural found, pattern fibroblasts of the have skin, been to characterize identified which it as thin are vs. 290.3±23.7µm) and the perichondrium of the cartilage for both species. (27.6±6.1µm vs. 10.5±1.8µm) (Fig.2G). In addition, a greater Also, in somatic samples of agoutis and spix’s yellow-toothed number of epidermal cells (61.7±15.2 vs. 24.8±2.4) and cavy, a specialized form of connective tissue was also found that chondrocytes (32.7±9.0 vs. 27.5±4.7) in the skin and cartilage promotes numerous functions, but the coating and support of surfaces is one of its main, known as cartilaginous tissue although a greater number of melanocytes, keratinocytes and (Fig.2C,F). Thus, in the cartilaginous tissue, a cartilaginous agoutis were found when quantification was performed, cavy (Table 1). sites in which chondrocytes, the main cell type of this tissue fibroblasts was observed in the skin of spix’s yellow-toothed matrixresides. has Additionally, been identified, the perichondrium composed of that gaps is thatresponsible are the Regarding the density of fibers in the dermis of these two rodents (Fig.3A,B), a higher density of collagen fibers in the Table 1. Quantification of cell numbers in ear skin and cartilaginous tissue derived from agoutis (Dasyprocta leporina) and spix’s yellow-toothed cavies (Galea spixii) Melanocytes Keratinocytes Epidermal cells Fibroblasts Chondrocytes Rodent Mean ± SD Range Mean ± SD Range Mean ± SD Range Mean ± SD Range Mean ± SD Range D. leporina 12.6 ± 4.7a 0-29 14.7 ± 4.2a 6-29 61.7 ± 15.2a 29-132 103.6 ± 24.7a 43-171 32.7 ± 9.0a 16-69 G. spixii 29.9 ± 6.2b 10-93 29.8 ± 7.6b 7-93 24.8 ± 2.4b 14-40 112.2 ± 11.3b 29-187 27.5 ± 4.7b 6-48 Data are expressed as mean ± standard deviation (SD); a,b Within a column, values with different superscripts differ (P
<0.05).
Dasyprocta leporina) and spix’s yellow-toothed cavy (Galea spixii) ear skin using GT. (A) Represent agouti skin. GT, obj.40x, bar = 20µm. (B) Represent spix’s yellow-toothed cavy skin. GT, Fig.3.obj.40x, Quantification bar = 20µm. of collagen (C fibers matrix of the skin and cartilage of the agouti ( Bars indicate standard deviation. a,b Values with different superscripts differ (P ) Represent the percentage of collagen fibers present in the dermis of agoutis and spix’s yellow-toothed cavy. <0.05). Pesq. Vet. Bras. 41:e06775, 2021 6 Alexsandra F. Pereira et al. skin of spix’s yellow-toothed cavy compared to agoutis was (Fig.5). Thus, the proliferative potential was determined as of1.69±0.68 the skin and of 1.36±0.15spix’s yellow-toothed AgNOR/cell forcavy agoutis was quantified and spix’s observedhas not been (Fig.3C). performed In contrast, (Fig.4). low density of elastic fibers yellow-toothed cavy, respectively (Fig.5C). While the area of for bothFinally, species a higher were percentage identified, of which the proliferative is why quantification activity of AgNOR/cell was 3.15±1.57 and 1.01±0.13µm2 for agoutis and spix’s yellow-toothed cavy (Fig.5D). fibroblasts in the skin of agouti compared to the fibroblasts
Dasyprocta leporina) and spix’s yellow-toothed cavy (Galea spixii) ear skin stained with WG. (A) Represent agouti skin. WG, obj.100x, bar = 10µm. (B) Represent spix’s yellow-toothed cavy skin. WG, obj.100x, Fig.4. Visualization of the elastic fiber’s matrix in the agouti (
bar = 10µm. Elastic fiber (arrow).
Fig.5. Proliferative activity of ear skin derived from agouti (Dasyprocta leporina) and spix’s yellow-toothed cavy (Galea spixii). (A) Staining D. leporina). AgNOR, obj.100x, bar = 10µm. (B spix’s yellow-toothed cavy (G. spixii C of AgNOR number/cell.in the fibroblast (D from agouti ( ) Staining ofa,b AgNOR Values within the different fibroblasts superscripts from and differ (P ). AgNOR, obj.100x, bar = 10µm. AgNOR present in the fibroblast nucleus (arrow). ( ) Quantification ) Quantification of AgNOR area/cell. Bars indicate standard deviation. <0.05). Pesq. Vet. Bras. 41:e06775, 2021 Ultrastructural and morphometric description of the ear skin and cartilage of two South American wild histricognate rodents 7
DISCUSSION and the dermis is less developed when compared to thick In this study, using the structure of the agouti (Dasyprocta skin (Webster & Webster 1980, Robert et al. 2012, Arda et leporina) ear skin and cartilage as a reference, we examined al. 2014). In wild rodents, variations between thin and thick the spix’s yellow-toothed cavy (Galea spixii) to establish an skin have also been observed, such as common mole mice adequate cryopreservation protocol for their somatic cells. (Cryptomys hottentotus) and naked mole mice (H. glaber) Therefore, we compared the structural patterns of this (Daly & Buffenstein 1998). In addition, in swine (Moyo et al. cells and their proliferative activity and showed that they al. 2018) these skin variations from different regions could regionwere different. between This these study species, may quantifiedallow the understanding several types of 2018),also be fishingobserved. bat (Yin et al. 2011) and in humans (Khalfa et how the environment could have altered the histological Moreover, we observed that the thickness of the spinosum characteristics of the skin and cartilage. One factor that may layer in the epidermis of spix’s yellow-toothed cavy was have promoted these changes is the evolutionary relationships larger than that of the agouti, unlike the basal layer and the that have contributed to the physiological adaptations of each corneum, which were smaller. Despite these variations in the of these species. This is because a set of skin properties has been shown to change according to the physiological needs of of the epidermis between these two species was not evident, the species, even when present under the same environment thickness of the layers, significant differences in the thickness (Daly & Buffenstein 1998). Additionally, other factors such each species (Webster & Webster 1980). Variations in the as ultraviolet radiation (Oriá et al. 2003) can also change the demonstratingthickness of the the epidermal existence layers of specific of the characteristicsskin of the neck, in skin structure patterns of these small rodents. thorax, and carpus of male and female paca (C. paca) have Initially, the ultrastructural evaluation of agoutis and spix’s also been described in the study by Isola et al. (2013). yellow-toothed cavy allowed to characterize the ultrastructure These variations observed in the agouti and spix’s yellow- of the ear skin and cartilage. In this way, similar characteristics toothed cavy epidermis are important, since they will allow were shown for these two rodents. This is because the skin was determination of cryoprotective agents that should be used in the cryopreservation of the skin (Praxedes et al. 2020). In addition, an average of 29.9 melanocytes and 29.8 revealed,loosening, containing since it is the composed epidermis of anddead dermis. cells and Specifically, that are in keratinocytes was observed in the spix’s yellow-toothed cavy theconstant epidermis, renovation the corneal (Abdo layeret al. 2020).was observed Also, in superficially,the skin, the epidermis for each tissue area evaluated. This value diverged from what was found for agouti skin (12.6 melanocytes and 14.7 keratinocytes). However, epidermal cells, such as Langerhans presence2020). In of general, the dermis these was characteristics highlighted, containing were already the fibers expected that and Merkel cells, in spix’s yellow-toothed cavy were found givesince it the flexibility ear skin and for support mammals to the in adjacentgeneral presentstissues (Abdo the same et al. to be smaller. In general, different cellular proportions of the patterns of ultrastructural organization (Khavkin & Ellis 2011, epidermis have also been observed for other species, such as Biggs et al. 2020). Among the species that present the same rodents, felids and domestic mammals, such as the common ultrastructural patterns of the skin, there are pacas (Cuniculus mole rat (C. hottentotus), naked mole rat (H. glaber) (Daly & paca) (Isola et al. 2013), naked mole rat (Heterocephalus Buffenstein 1998), jaguar (Panthera onca) (Praxedes et al. glaber) (Menon et al. 2019) and mouse (Allen & Potten 2020), cats, dogs (Souza et al. 2009) and pigs (Navarro et 1976) stand out (Morita et al. 1995). Still, this same pattern al. 2001). This cellular variation observed both in agoutis was also observed in the skin of Cuban crocodile (Crocodylus and spix’s yellow-toothed cavy for other species may be rhombifer) (Szewczyk & Stachewicz 2020) and in the skin of associated with the need in the skin to protect itself from humans (Roger et al. 2019). In addition, in this study region, cartilaginous tissue and its gaps, which are the sites from which melanin synthesized from melanocytes of the epidermis chondrocytes, cells responsible for maintaining cartilage, were thehas thisenvironment, function (Khavkin specifically, & Ellis from 2011, ultraviolet Dolka et rays, al. 2014). since In addition, another explanation related to this process can presence of cartilaginous tissue is important because this type be associated with a chain of hormones responsible and alsoof specialized identified connective (Fox et al. tissue 2009, provides Akkiraju support, & Nohe rigidity2015). Theand regulating the proliferation and differentiation of melanocytes, shape for the entire structural architecture of the ear of these keratinocytes, Langerhans cells and Merkel (Scholzen et al. small rodents (Vanwanseele et al. 2002). 1998), among which the neuropeptide stands out stimulating Regarding the morphological analysis of the skin of agouti (Souza et al. 2015). in the epidermal region, the basal, spinosum and corneum. alpha-melanocyteIn both species, (α-MSH) the main that and triggers most different abundant skin cell reactions type in andWhile spix’s the yellow-toothedgranular and lucid cavy, layers only three were layers not distinguishable. were identified Characteristics were also observed in the skin dermis of these two rodents, where the presence of the papillary and reticular thecorroborating dermis was the fibroblasts. results regarding In addition, the collagen skin of andthe elastictail of layer was not evident. This is because we are evaluating thin fibersthe European in the skin beaver of these (Castor two fiber species) (Dolka were et also al. 2014) observed, and skin, where unlike thick skin it is not always possible to verify different regions of the skin of male and female paca (C. paca) the presence of the different layers that form the epidermis as (Isola et al. 2013). However, a greater amount of collagen well as the dermis (Browne 2004). In general, in mammals it was observed that the epidermal and dermal proportions of may be due to the number and collagen synthetic activity of the skin may vary due to the location of the body, as well as fibers was found in the cavy dermis compared to agoutis. This the genetic, physiological and epigenetic need of the species to (Khavkin & Ellis 2011), also justifying the greater thickness adapt to the environment, since on the thin skin the epidermis dermalof this region fibroblasts when in compared the skin ofto spix’sagouti. yellow-toothed cavy
Pesq. Vet. Bras. 41:e06775, 2021 8 Alexsandra F. Pereira et al.
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