BackgroundThe red brocket deer, Mazama americana, has at least six distinct karyotypes in different regions of South America that suggest the existence of various species that are today all referred to as M. americana. From an evolutionary perspective, the red brockets are a relatively recent clade that has gone through intense diversification. This study sought to prove the existence of post-zygotic reproductive isolation in deer offspring between distinct chromosome lineages. To achieve this, inter-cytotype and intra-cytotype crosses were performed, which resulted in both F1 hybrid (n = 5) and pure offspring (n = 3) in captivity.ResultsF1 females were analyzed in terms of their karyotypes, ovarian histology, estrous cycles and in vitro embryo production. Pure females presented parameters that were similar to those previously reported for M. Americana; however, the parameters for hybrid females were different. Two hybrids were determined to be sterile, while the remaining hybrids presented characteristics of subfertility.ConclusionsThe results support the existence of well-established reproductive isolation among the most distant karyotype lineages and elucidates the need to define all karyotype variants and their geographical ranges in order to define the number of species of red brocket.

The red brocket (Mazama americana) is a South American deer with a wide geographical distribution that presents different chromosomal variants depending on their location. At least six different cytotypes belonging to two distinct evolutionary lineages have been described. This study aimed to verify the existence of postzygotic reproductive isolation between cytotypes of M. americana by comparative evaluation of pure and hybrid males. Seven 18-month-old bucks were submitted to seminal collection and evaluation and testicle histological evaluations. The pure males showed normal parameters for sperm quality and testicular histology. Hybrids from the same evolutionary lineage (≤3 chromosomes different from the progenitors) showed similar results to pure males, except for the reduced ratio of round spermatids to pachytene spermatocytes. Hybrids between cytotypes of different evolutionary lineages (≥10 chromosomes different from progenitors) presented azoospermia and evidence of testicular degeneration. Despite the striking morphological similarities, we can conclude that populations with more distinct karyotypes possess an effective reproductive barrier; moreover, there is evidence that reproductive isolation mechanisms exist between some closer karyotypes, corroborating the hypothesis that M. americana is best characterized as a superspecies. Thus, the future description of several new species for this taxon is expected, since the tendency is to establish efficient mechanisms of postzygotic reproductive isolation, preventing the introgression and fusion of genomes from different populations through chromosome variation.

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In recent years the concept of genomic resource banks has grown as a way of maintaining the genetic variability of populations, while the quality of cryopreservation of the gametes determines the effectiveness of such banks. However, the absence of basic knowledge regarding the physiology of species and their semen characteristics hampers the establishment of reproductive biotechnologies. Thus, this paper aimed to determine certain physicochemical (volume, colour, appearance, pH and osmolarity) and microscopic characteristics (mass movement, motility, vigour, concentration, and sperm morphology and morphometry) of semen of the species Mazama americana. To achieve this, five males of the species were used, and three semen samples per buck (electroejaculation) were collected at intervals of 2 weeks. The volume, pH and osmolarity of the ejaculate were 0.39 ± 0.14 mL, 6.90 ± 0.74 and 297.74 ± 19.10 mOsm/kg, respectively, while the values obtained for mass movement, motility, vigour and concentration were 3.33 ± 0.82; 69.6 ± 8.92%; 3.53 ± 0.50, and 244.07 ± 98.65 × 107/mL, respectively. Regarding the colour of the ejaculate, five samples were classified as ivory, two as yellowish, two as whitish and six as white. Regarding appearance, seven samples were considered creamy and eight, milky. Morphology was analysed in a humid chamber under phase contrast microscopy and 73.50 ± 5.57% of cells presented normal morphology, 8.37 ± 3.15% presented major defects and 18.13 ± 6.46% presented minor defects. To determine sperm morphometry, an optical microscope (Leica DM 5000B) and the Leica Qwin image analyser program were used, resulting in 8.09 ± 0.40, 4.65 ± 0.30, 2.81 ± 0.44 and 30.25 ± 3.02 μm for length, largest width, smallest width and area, respectively.

This study aims to evaluate the ovulation rate and the presence of functional corpora lutea after treatment by three different protocols designed to cause superovulation in brown brocket deer. Six female received an intravaginal device containing 0.33 g of progesterone (CIDR®) for 8 days, followed by 0.5 mg injection of estradiol benzoate at the time of insertion and 265 µg of cloprostenol at the time of removal. Afterwards, the hinds were divided into three groups (n = 2): Treatment A received injection of 600 IU eCG on Day 4 after CIDR® insertion; Treatment B received injection of 300 IU eCG at the same time; and Treatment C received injection of 250 IU FSH dissolved in PVP, also on Day 4 post-insertion. The treatments were crossed over with 44-48 day intervals after CIDR® removal, such that all the deer were submitted to all three treatments. The mean ovulation rate (Treatment A = 3.40 ± 0.68, Treatment B = 1.40 ± 0.24, Treatment C = 0.80 ± 0.49), total ovarian stimulation (Treatment A = 4.80 ± 1.02, Treatment B = 1.80 ± 0.37, Treatment C = 1.40 ± 0.60), and mean CL diameter (Treatment A = 7.33 ± 0.76 mm, Treatment B = 3.94 ± 0.19 mm, Treatment C = 2.18 ± 0.49 mm) in Treatment A were significantly higher than the mean ovulation rates, total ovarian stimulation, and mean CL diameter in Treatments B and C. The mean fecal progesterone metabolites at the luteal phase in Treatment A (6,277.94±2,232.47 ng/g feces) was significantly different from Treatment C (1,374.82±401.77 ng/g feces). Thus, although fertility was not evaluated directly, Treatment A proved capable of induce superovulation in the species Mazama gouazoubira, presenting the greatest mean ovulation rates, with the formation of functional corpora lutea.