Journal of
Threatened Taxa | www.threatenedtaxa.org | 26 January 2019 | 11(1): 13114–13119
Functional sperm assessments of African Lion Panthera
leo (Mammalia: Carnivora: Felidae)
in field conditions
Thiesa Butterby Soler
Barbosa 1, Daniel de Souza Ramos Angrimani
2, Bruno Rogério Rui 3, João Diego de Agostini Losano 4, Luana de Cássia Bicudo 5, Marcel
Henrique Blank 6, Marcilio Nichi 7 &
Cristiane Schilbach Pizzutto
8
1---–8 Department of Animal Reproduction, School
of Veterinary Medicine and Animal Science, University of São Paulo, Av. Prof. Orlando Marques de Paiva, 87 - 05508-270, São Paulo, Brazil.
1 Department of Surgery, Division of Human
Reproduction, Federal University of São Paulo, Rua Embaú, 231, 04039-060- Vila Clementino
– São Paulo, Brazil.
1 tbsoler@gmail.com, 2
angrimani@gmail.com, 3 brunorogeriorui@gmail.com, 4
jdalosano@usp.br, 5 luanabicudo@usp.br 6 marcelblank@usp.br, 7
mnichi@usp.br (corresponding author), 8 crissp@usp.br
Abstract: Wild African Lion Panthera
leo populations are
decreasing due to inbreeding and reduced genetic variability. Thus, the use of assisted reproduction in the
species could one day become essential.
Before this is possible, however, studies need to be conducted on the
basic reproductive traits of
the species, especially those regarding sperm cells. This study aimed to analyze
the semen of African Lions in field conditions.
We included seven captive African Lions in our study. The animals were chemically restrained and
electro-ejaculated. Twenty sperm samples
were selected and analyzed for sperm motility and
progressive motility, sperm motility index, and sperm morphology. In addition, the samples were analyzed for membrane and acrosome integrity (hypoosmotic swelling test and fast green/rose Bengal dyes,
respectively) and assessed for cytochemical activity
of the mitochondria. We found that sperm
motility rate was 75.25%±2.03, progressive motility rate was 3.25%±0.10, and
sperm motility index was 70.12%±1.71. We
found morphologic abnormalities roughly at the expected rate with 34.61%±7.22
of the sperm cells having an intact plasma membrane and acrosome integrity of
92.27%±2.73; high mitochondrial activity was 54.26±4.88% and absence of
mitochondrial activity was 2.72±0.68% in the sperm cells. These findings show that conventional tests
for sperm motility and sperm morphology bring about the expected results for
lions according scientific literature.
Though a hypoosmotic swelling test may be performed using different
concentrations, it might lead to a higher number of sperm cells with membrane
damage. Fast green/rose Bengal stain and
3’3 diaminobenzidine assay, however, can be used in
sperm analysis of lions in field conditions.
Keywords: Mitochondrial activity, plasma membrane,
acrosome, sperm analysis.
doi: https://doi.org/10.11609/jott.4142.11.1.13114-13119
Editor: Ulrike Streicher, Cascades Raptor Center, Eugene, USA. Date of publication: 26 January
2019 (online & print)
Manuscript details: #4142 |
Received 20 March 2018 | Final received 07 January 2019 | Finally accepted 15
January 2019
Citation: Barbosa, T.B.S., D.D.R. Angrimani, B.R. Rui, J.D.D. Losano, L.D. Bicudo, M.H. Blank, M. Nichi
& C.S. Pizzutto (2019). Functional
sperm assessments of African Lion Panthera leo (Mammalia: Carnivora: Felidae) in field
conditions. Journal of Threatened Taxa 11(1): 13114–13119; https://doi.org/10.11609/jott.4142.11.1.13114-13119
Copyright: Barbosa et al. 2019. Creative Commons
Attribution 4.0 International License. JoTT
allows unrestricted use, reproduction, and distribution of this article in any
medium by adequate credit to the author(s) and the source of publication.
Funding: This study
was financed in part by the
Fundação de Amparo à Pesquisa do Estado de São Paulo
(FAPESP - 03/00642-0) and the Coordenação
de Aperfeiçoamento de Pessoal
de Nível Superior (CAPES).
Competing interests: The authors declare no competing interests.
Declarations: This experiment and study were as approved
by the Bioethics Committee of the School of Veterinary Medicine and Animal
Science at the University of São Paulo, São Paulo, Brazil (protocol no.
310/2003), and by the Brazilian Institute of Environment and Renewable Natural
Resources (process no. 0227.026090/2002-39 IBAMA). Unless otherwise mentioned, all chemicals
used were obtained from Sigma-Aldrich (St. Louis, MO, USA).
Author Details: Thiesa Butterby Soler Barbosa, DMV, MSc, PhD. Expert in
Reproduction of wild and domestic animals. Daniel
De Souza Ramos Angrimani, DMV, MSc, PhD.
Currently Postdoc degree student (PPGRA-FMVZ / USP). Expert
in Reproduction of wild and domestic animals. Currently
professor at Universidade São Judas Tadeu, São Paulo, Brazil. Bruno Rogério Rui,
DMV, MSc, PhD. Expert in Reproduction of wild and domestic animals. Currently professor at Universidade São
Judas Tadeu, São Paulo, Brazil. João Diego De Agostini Losano, DMV, MSc, PhD. Currently Postdoc degree
student (PPGRA-FMVZ / USP). Expert in Reproduction of wild
and domestic animals. Luana De Cássia Bicudo, DMV, MSc, PhD. Expert in Reproduction of
wild and domestic animals. Marcel
Henrique Blank, Bsbio, MSc. Currently PhD
degree student (PPGRA-FMVZ / USP). Expert in Zoology and Reproduction of wild
and domestic animals has skills in breeding ecology, reproductive
endocrinology, sperm, germ cells and cryopreservation. Marcilio Nichi, DMV, MSc, PhD, Postdoc. Professor at FMVZ/USP. Expert in Reproduction of wild and
domestic animals has skills in Andrology and cryopreservation. Cristiane Schilbach Pizzutto, DVM,
MSc, PhD, Postdoc. Professor at FMVZ/USP. Chairman of the Animal Welfare Committee of CRMV - SP. Member of
the International Environmental Enrichment Conference Committee and of REPROCON
research group.
Author Contribution: TBSB, DSRA, JDAL, MN and CSP were responsible for
conception and design of the study, acquisition of data, analysis and
interpretation of data, drafting the article, revising the article; BRR, LCB,
MHB were responsible for acquisition of data and revising the article.
Acknowledgements: This work was supported by
the Fundação de Amparo à Pesquisa do Estado de São
Paulo (FAPESP – 03/00642-0) and the
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior. Moreover, the authors thank
the Fundação Parque Zoológico de São Paulo and professor Marcelo Alcindo de Barros Vaz Gimarães (in memoriam).
Introduction
African Lion Panthera
leo is considered a
prolific species and may be used as an experimental model for other endangered
large felids (Gilmore et al. 1998; Borrego & Dowling 2016). Large successfully reproducing captive
populations provide a satisfactory number of animals for experimental studies
aimed at being replicated in wild populations.
Lion populations are decreasing in their native countries leading to
increased inbreeding and reduced genetic variability (Wildt et al.
1995; McDermid et al. 2017). Other endangered felids
such as Jaguar Panthera onca,
Tiger P. tigris, and
Snow Leopard P. uncia also face similar
problems (Caso et al. 2008; Jackson et al. 2008; Chundawat et al. 2011).
The study of the reproductive
parameters in lions is fundamental for the successful application of
reproductive technologies such as artificial insemination (Goeritz et
al. 2012) and cryopreservation (Luther et al. 2017). Although techniques of
assisted reproduction in humans and livestock species are well-established,
it is important to recognize that these cannot be applied universally without
species-specific studies (Howard et al. 1986).
Consequently, the knowledge of sperm features in lions is important for
the successful application of such techniques in wild felids.
Previous
studies demonstrated the possibility to predict sperm fertility after semen
analysis in humans (Nosrati et al. 2016), bovines (Utt 2016), and dogs (Hesser et
al. 2017). To our knowledge, however,
there is so far no study of this relationship in lions. Moreover, the combination of
conventional sperm analysis and sperm functional tests allows a more adequate
prediction of the fertility of semen samples (Shen
& Ong 2000; Aitken 2006). Today, there are several possibilities to
evaluate sperm functionality such as fluorescent probes (Singh et al. 2016),
computer sperm analysis (Barranco et al. 2017), and
the estimation of lipid peroxidation rates (Nichi et
al. 2017).
The
evaluation of sperm samples from wild felids should be focused on field
conditions since there are limitations in transporting the samples of some of
the endangered species to research centres that have the facilities to handle
the sperm cells (Hermes et al. 2013).
Therefore, the establishment of sperm function rates for lions in field
conditions can simplify future fieldwork and help develop reproductive
technologies applicable under field conditions.
The aim of this study was to
establish the standard rates of sperm evaluation by conventional and functional
assessments (i.e., mitochondrial activity, the integrity of acrosome, and sperm
plasma membrane) for African Lions under field conditions.
Materials and
Methods
Animals
We used seven captive adult lions between the ages of four and seven
years, which were housed individually at the Fundação
Parque Zoológico de São
Paulo (São Paulo, Brazil). According to
the reproductive records provided by the zoo, all males in this study were
proven to be breeders.
Semen collection
Semen
collections were made after electro-ejaculation under anaesthesia. The animals were anaesthetized with a
combination of Tiletamine and Zolazepam
(Zoletil 50, VirbacTM do Brasil, 10mg/kg, IM).
Electro-ejaculation was performed using the protocol described by Howard
(1993). Semen was collected in sterile
plastic tubes (15mL) and immediately evaluated.
Each animal was submitted to semen collection at least four times at intervals
of five weeks between the handling events.
In total, 28 collections were performed, out of which six were
interrupted due to problems during the procedure (e.g., anaesthesia or urine
contamination) and two samples did not reach the minimum standards.
Conventional sperm analysis
Immediately
after semen collection, the motility (0–100%) and progressive motility (0–5)
were measured, sperm morphology was examined, and sperm motility index (SMI)
was calculated. Motility and progressive
motility were assessed using 10µL of semen sample placed on a clean and
pre-warmed glass slide at 37°C, covered with a coverslip, and evaluated under a
microscope equipped with a hot stage to keep the slides at 37°C (100x and 400x
magnification, Nikon® E200, Japan).
The sperm motility index was calculated using the formula described by
Howard (1993) (motility + 20 x
progressive motility). Morphologic
alterations were evaluated fixing sperm samples in a 10% formalin buffer
solution (V/V) in wet mounts, which were observed under a phase contrast
microscope (1000x magnification, Nikon® E200, Japan). Abnormalities were classified according to
their locations in the sperm cell (Barth & Oko
1989).
Hypoosmotic swelling test
To
evaluate sperm membrane integrity, we used a hypoosmotic swelling
assay. To perform this technique, two
media of different osmolarities were prepared, one isoosmotic (300mOsm) and one hypoosmotic
(50mOsm). The isoosmotic
medium was prepared by mixing sodium citrate (50%) and fructose (50%) in 500ml
of distilled water in accordance with the technique described by Jeyendran et al. (1984).
One aliquot of 200µl of semen was added to the same volume of isoosmotic and hypoosmotic
media. The mixture was homogenized and
incubated in a water bath at 370C for 30min. The reactions were stopped
by adding 10µL of 10% formalin solution (V/V). In the hypososmotic
mixture, cells were
swelling aiming to establish equilibrium between the intra and extracellular
environment. Samples were evaluated in
wet mounts under an interference phase microscope (400x magnification, Leitz Dialux 20) by counting the
swollen sperm cells showing coiled tails (200 sperm in each medium), which
indicate biochemically active cells. As
a control group, the isoosmotic medium was used
aiming to evaluate tails that were abnormally coiled in the ejaculate. The percentage of sperm cells with intact
membranes was calculated by subtracting the percent
of cells with coiled tails in the hypoosmotic medium
from the percent found in the isoosmotic
medium. The results were expressed as
percentages (%).
Acrosome integrity analysis
Acrosome
integrity was analyzed using a single-stain solution
containing 1% (w/v) rose Bengal, 1% (w/v) fast green FCF, and 40% ethanol in McIlvaine’s citrate phosphate buffer (Pope et al.
1991). A mixture of 5μL of stain
solution and 5μL of semen was transferred on a pre-warmed slide (37oC)
and, a smear was made using a different slide after 60s. The smears were air-dried and at least 200
cells were counted under a light microscope (Nikon Eclipse E200, Japan) at a
1000× magnification. The results were
expressed as percentages (%). The
acrosome was considered damaged if the acrosome region remained unstained or
brighter than the post-acrosome area.
The acrosome was considered intact if the sperm acrosome region was
stained in purple or darker than the post-acrosome area.
Evaluation of mitochondrial activity
Semen
samples were analyzed for mitochondrial activity
using a 3’3 diaminobenzidine (DAB) assay (Hrudka 1987; Angrimani et al.
2017a). Therefore, the semen was diluted
(1:1) in 1mg/ml solution of DAB in PBS (Phosphate-buffered saline)
and incubated in a water bath at 37oC for one hour in the dark. Smears were then prepared on glass slides and
fixated in 10% formalin for 15min. These
were evaluated under the light microscope with oil immersion objective (Nikon
Eclipse E200, Japan) at 1000× magnification; 200 sperm cells were
evaluated. The results were expressed in
percentage (%). Sperm cells were
classified into four categories: high mitochondrial activity (100% of the
mid-piece stained – DAB Class I), medium mitochondrial activity (more than 50%
of the mid-piece stained – DAB Class II), low mitochondrial activity (less than
50% of the mid-piece stained – DAB Class III), and absence of mitochondrial
activity (absence of staining in the mid-piece – DAB Class IV).
Statistical analysis
In
total, 20 ejaculates exhibiting at least 60% of motility and progressive
motility greater than three (scale of 0–5) could be analyzed. All data were analyzed
using the SAS system for Windows (SAS Institute Inc., Cary, NC, USA). Descriptive analysis was performed using the
PROC MEANS. Results are reported as
untransformed means ± S.E.M. Spearman
correlation was used to calculate the relationship between the variables
studied. A probability value of p <
0.05 was considered statistically significant.
Results
Sperm
motility rates were 75.25±2.03%.
Progressive motility was 3.25±0.10 and sperm motility index averaged
70.12±1.71% (Fig. 1). Mean values of the
percentage of morphologic abnormalities observed in the acrosome, head,
mid-piece, and tail found in the unstained fixed samples were 2.42±0.95%, 3.89±0.70%,
9.5±2.58%, and 43.07±6.39%, respectively (Table 1).
The
percentage of sperm cells with intact membrane evaluated by HOST was
34.61±7.22% and the acrosome integrity rate was 92.27±2.73% in the sperm cells
(Fig. 2). High mitochondrial activity
(DAB – Class I) was shown by 54.26±4.88% of the sperm cells. Medium mitochondrial activity (DAB – Class
II) was shown by 36.7±3.92% and low mitochondrial activity by 6.25±0.88% of the
sperm cells. No mitochondrial activity
was shown by 2.72±0.68% of the sperm cells (Fig. 3).
Positive
correlations were found between the percentage of high mitochondrial activity
(DAB – Class I), intact plasma membrane (r=0.60, p=0.049), and acrosome
integrity (r=0.69, p=0.0041). No other
correlations were found in the variables evaluated.
Discussion
In this
study, we evaluated the spermatic features of African Lions by conventional
(i.e., motility and morphologic abnormalities) and functional (i.e.,
mitochondrial activity and plasma membrane and acrosome integrity) tests.
We
observed a high motility rate, progressive motility, and SMI values assessed by
conventional microscopy. Other authors
previously reported similar results (Gilmore et al. 1998; Luther et al. 2017). Our values for sperm morphologic
abnormalities were also in accordance with previous studies of lions (Lueders et al. 2012).
This shows that sperm parameters were within the expected range for the
species in the conventional evaluation.
It is important to verify that the sperm is of high quality for the
subsequent functional tests. Moreover,
it is noteworthy that with this motility and normal morphology rates, the
collected semen could be used in cryopreservation protocols (Luther et al. 2017).
Our
values for cells with intact membranes (34.61±7.22%), however, were low when
compared to other felines such as Tigrina Leopardus tigrinus (Angrimani et al. 2017a), Domestic Cat Felis
catus (Zambelli et al.
2010), and Clouded Leopard Neofelis nebulosa (Tipkantha et al.
2017). To our knowledge, this is a
pioneer study of the sperm cell membrane integrity in lions using hypoosmotic swelling tests.
Lueders et al. (2012) observed 66.3±10.1% of
sperm membrane integrity using vitality staining in lions. Thus, we believe that our result is
underestimated.
However
the sperm cells in this study showed a high motility; if this high percentage
of damaged membranes would be correct the efficient transduction of ATP through
the cell would be compromised, causing immobility or low motility rates (Amaral et al. 2013; Angrimani et
al. 2017b). The relation between a normal
mitochondrial function and membrane integrity was demonstrated in this study,
when we observed the positive correlation between high mitochondrial activity
and plasma membrane and acrosome integrity. In this scenario, we hypothesize
that may the hypoosmotic swelling test in the used
concentration of fructose and sodium citrate was deleterious for the sperm cells In fact, Comercio et al. (2013) observed modifications in sperm
response after different concentrations of fructose and sodium citrate in the hypoosmotic test in domestic cats. Therefore, further
studies with lions are recommended using different concentrations of solutes
for the hypoosmotic test, or another method of plasma
membrane integrity evaluation, such as eosin/nigrosin
stain which can be certainly used in field conditions (Daub et al. 2016).
In
contrast to the results on plasma membrane integrity, in the acrosome analysis
we found a higher number of cells with intact acrosomes. This membrane
endurance is pivotal for the sperm to tolerate post-ejaculation injuries and to
be able to bind to the oocyte (Bucci et al. 2017).
Thus, this result shows that fast green/rose bengal stain could be an option to field evaluation
of semen of African lions or even other wild felids.
Finally
the mitochondrial activity test that a high number of sperm cells had the
maximum mitochondrial functionality (high and medium activity – DAB Class I and
II), which is essential for the production of ATP and consequently for the
motility kinetics (Vicente-Carrillo et al. 2015). This was expected in our
study since the samples are fresh from animals in reproductive age and with
high motility rates (i.e. conventional tests). Besides, the low percentage of
DAB Class III and IV (low and absence of mitochondrial activity), was also a
predictable result, as high rates of this parameters are associated with
mitochondrial dysfunctions due to lesion in axonemal
proteins or decreased energy production (de Lamirande
and Gagnon 1992a; de Lamirande and Gagnon 1992b; Rui et al. 2017), which were both not found in this study.
In
conclusion, the results from conventional tests were as expected for the
species. Regarding the functional assessments, the hypoosmotic swelling test
did not show to be a good option to analyze plasma
membrane integrity in lion. On the other hand, fast green/rose bengal stain and 3’3 diaminobenzidine (DAB) assays appear to be a good optiosn for analyze the sperm
from African Lions P. leo in filed conditions.
Table 1. Mean, standard error of the
mean (SEM), and minimum (Min) and maximum values (Max) of sperm morphologic
abnormalities according to location in adult African Lion
Panthera leo sperm samples
Sperm morphologic abnormalities (%) |
Mean |
SEM |
Min |
Max |
Sperm head abnormalities |
3.89 |
0.70 |
1.0 |
11.0 |
Sperm mid-piece abnormalities |
9.5 |
2.58 |
0 |
46.0 |
Sperm tail abnormalities |
43.07 |
6.39 |
8.0 |
90.0 |
Sperm acrosome abnormalities |
2.42 |
0.95 |
0 |
17.0 |
For
images/figures -- click here
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