Freeze-dried egg yolk based extenders containing various antioxidants improve post-thawing quality and incubation resilience of goat spermatozoa

Evaluation of Cryopreserved Ram Sperm with Nano-Ozone Solution and Post-Thaw Life Span by Flow Cytometric Analysis

Ozone has been used as a therapy tool in medical science for conditions such as ulcers, peritonitis, wounds, and mostly joint problems. Ozone therapy strengthens the resistance to infections by kick-starting antioxidant, anti-inflammatory, and immune modulation systems. Ozone creates a defensive response against oxidative stress in membranes and protects metabolism against reactive oxygen species (ROS). Sperm membranes are one of ROS's main targets; therefore, the cells' cryopreservation process requires more defensive elements for better results. This study aimed to investigate the protective effect of nano-ozone solution (NOS) on ram sperm cryopreservation and the influence of the process on various sperm parameters for post-thaw (0 hour) and postincubation (6 hours) time points. Samples were collected from six Merino rams in the breeding season by electroejaculation five times at 3-day intervals. The study was conducted by cryopreservation of the samples using a tris citric acid-egg yolk-based extender. The samples were subjected to freezing in control and NOS (0.5, 1, and 2 μg/mL nano-ozone supplemented). Post-thaw motility, hypo-osmotic swelling test, acrosome (fluorescein isothiocyanate-conjugated Pisum sativum agglutinin [PSA-FITC]), and DNA integrities (terminal deoxynucleotidyl transferase dUTP nick end labeling [TUNEL]) were evaluated with a phase-contrast microscope. Mitochondrial membrane potential (MMP) assessments were conducted by JC1-PI dual staining with a flow cytometer. Malondialdehyde and glutathione (GSH) levels were measured by a spectrophotometer. Sperm kinematics were investigated by a computer-assisted sperm analyzer (CASA) at the post-thaw time point. Compared with the control, relatively low doses of NOS (0.5 and 1 μg/mL) yielded better results in many parameters (motility, membrane and acrosomal integrities, MMP, various sperm kinematics, and GSH levels) (p < 0.05). The addition of low ozone doses to cryopreservation extenders improved the results compared with the control group at post-thaw and postincubation time points. Despite the valuable potential of nano-ozone supplementation in ram sperm cryopreservation, this subject requires further investigations with fertility trials soon.

The effects of supplementation of vitamin D to the egg-yolk extender on cryopreservation of ram semen

OBJECTIVES

This study aimed to examine the effects of supplementation of vitamin D to the egg-yolk extender on characteristics of frozen-thawed ram semen.

METHODS

Semen samples obtained from adult rams were pooled and divided into five equal volumes. It was reconstituted with extenders containing different concentrations of vitamin D: 0 (control), 12.5 (VITD 12.5), 25 (VITD 25), 50 (VITD 50), and 100 ng/mL (VITD 100), and then they were frozen. Sperm motility parameters, plasma membrane functional integrity, acrosomal integrity, DNA fragmentation, and mitochondrial membrane potential of the groups were evaluated after sperm thawing.

RESULTS

Total motility and progressive motility were higher in VITD 50 than in all other groups (p < 0.05). Higher sperm straightness, linearity, and wooble were higher in VITD 50 than in the control group (p < 0.05). A similar pattern of VITD 50 was observed for plasma membrane integrity and mitochondrial membrane potential (p > 0.05).

CONCLUSIONS

In the study, it was observed that adding vitamin D to the extender had a beneficial effect on ram spermatological parameters. In addition, it was concluded that the use of the 50 ng/mL vitamin D in the extender provided more effective protection than the other doses.

Post-Thaw Parameters of Buck Semen Quality after Soy Lecithin Extender Supplementation with Fumaric Acid

The supplementation of cryopreservation media with antioxidants improves the post-thaw quality and fertilizing ability of spermatozoa. To maximize the fertility of frozen-thawed buck spermatozoa, further research is required to overcome obstacles that have yielded controversial results and standardize protocols. In the present work, the effect of adding fumaric acid (a well-described antioxidant) to a soy lecithin semen extender on certain quality parameters of spermatozoa following freezing and thawing was examined for the first time. Five sexually mature Skopelos bucks were used, and ejaculates were collected with an artificial vagina. The semen samples (98 samples, five replicates) were diluted (400 × 106 spermatozoa/mL) with OviXcell®, supplemented with fumaric acid (0 mM, 2.15 mM, 10 mM or 30 mM), equilibrated (5 °C; 3 h), packed (0.5 mL straws), frozen and stored (-196 °C) until further processing. After thawing, the spermatozoa total and progressive motility (CASA), viability (eosin-nigrosin), membrane functional integrity (HOST), acrosome integrity (SpermBlue®) and mitochondrial function (Rhodamine-123/SYBR-14/PI) were evaluated. Statistical analysis was performed with one-way ANOVA, followed by Duncan's test; significance was set at 0.05. The addition of 2.15 mM fumaric acid improved (p < 0.05) spermatozoa viability, membrane functional integrity, acrosome integrity and mitochondrial function compared to all other concentrations. The addition of 30 mM fumaric acid decreased (p < 0.05) spermatozoa viability and mitochondrial function compared to all other concentrations. These results indicate a beneficial effect of a 2.15 mM fumaric acid addition to a soy lecithin extender on post-thaw buck spermatozoa quality. Further research is required to evaluate the in vivo fertility of frozen-thawed buck spermatozoa treated with fumaric acid, as well as to elucidate the mechanism of action of fumaric acid in spermatozoa.

Methionine, cysteine, and butylated hydroxytoluene enhance cryosurvival of ram semen on post-thaw and post-incubation time points

Despite there have been many experiments conducted about antioxidants, the best sole or combination use of antioxidants to include as a standard ingredient to freezing extenders is yet to be found. This study was designed to investigate the different doses of methionine (2.5 and 5 mM), cysteine (1 and 2 mM), and butylated hydroxytoluene (BHT) (1 and 2 mM) for ram semen cryopreservation on post-thaw and post-incubation (6 h) time points over spermatological parameters. Semen samples were collected from Kivircik rams via electro-ejaculator in breeding season. After essential spermatological evaluations, appropriate samples were pooled then split into 7 equal aliquots to create study groups (antioxidant free control, 2.5 mM methionine, 5 mM methionine, 1 mM cysteine, 2 mM cysteine, 1 mM BHT, and 2 mM BHT). Semen samples were put into French straws (0.25 mL), and freezing procedure (two-step) was conducted via a programmable gamete freezer. At both time points, motility, HOST, PSA-FITC, and TUNEL assays were made to discover the impacts of cryopreservation and incubation process over sperm cells. Antioxidant supplemented groups yielded better results compared to the control groups in terms of various spermatological parameters not only at post-thaw time point but after incubation for 6 h of time. The study demonstrated that supplementing sperm freezing extenders with previous antioxidants may create new approaches to cryopreservation procedures, and through increasing success rate of freezing, fertility results may increase to better results in near future.

The replacement of fresh egg yolk by lyophilized egg yolk in Tris-base extender in cryopreserved Boer and Saanen semen

Egg yolk is a common cryoprotectant that can be used as a semen extender to protect the spermatozoa from damage during cryopreservation. Therefore, the aim of this study was to investigate the efficacy of fresh and lyophilized egg yolk, as a Tris-base extender, on the quality of cryopreserved goat semen. Semen from ten rams of two different breeds (Boer and Saanen) was collected using an artificial vagina. Each ejaculate sample was divided into four equal aliquots, which contained 20% of the fresh egg yolk (a control group), and then 10%, 15%, and 20% of the lyophilized egg yolk as a Tris-base extender. Sperm motility and kinematic parameters were determined using a computer assisted semen analyzer (CASA). The results showed that the addition of 20% of the fresh egg yolk in Tris-base extender exhibited significantly higher progressive motility, progressive fast motility, distance curve line (DCL), and beat cross frequency (BCF) parameters in the post-thaw Boer and Saanen goat sperm when compared with the addition of 10%, 15%, and 20% of the lyophilized egg yolk. The percentage of total motility, and immotile parameters in the post-thaw Boer and Saanen goat sperm were not significantly different between the control and 10%, 15% as well as 20% of the lyophilized egg yolk groups. Moreover, the percentage of viability parameter in the Boer and Saanen goat sperm was not significantly different between the control and 10% of the lyophilized egg yolk group, but showed significant difference between the control group and 15% and 20% of the lyophilized egg yolk groups. Furthermore, the interaction between the two breeds was significantly different in terms of head activity (HAC), and straightness (STR) parameter. In conclusion, the treatment with 20% of fresh egg yolk in Tris-base extender is superior to the lyophilized egg yolk. However, an addition of 10% of the lyophilized egg yolk in Tris-base extender presented the percentage of total motility and viability parameters showing no difference with 20% of fresh egg yolk. Therefore, 10% of the lyophilized egg yolk in Tris-base extender provided detail of the lyophilized egg yolk protocol in cryopreserved goat semen as an example of an alternative extender to 20% of fresh egg yolk for situations where an animal's origin represents a microbiological risk.

Positive effect of autologous platelet rich plasma on Saanen buck semen cryopreservation in non-breeding season

The objective of the current study was to evaluate the effect of autologous platelet-rich plasma (PRP) addition into soybean lecithin based extender on buck semen at post-thaw. Semen samples were collected from eight Saanen buck, and each semen sample was split into four equal aliquots and diluted with different concentrations of PRP supplemented extenders [no PRP (control), 0.5 × 10⁷/ml PRP, 1 × 10⁷/ml PRP, or 2 × 10⁷/ml PRP]. Motility, plasma membrane functional integrity, acrosome integrity, mitochondrial membrane potential, DNA integrity and malondialdehyde concentrations (MDA) were measured and analyzed at post-thaw. The results showed that 2 × 10⁷/ml PRP group had a positive effect on motility (62.41 ± 4.24), membrane functional integrity (71.11 ± 2.90), mitochondrial membrane potential (69.70 ± 1.99), DNA integrity (7.22 ± 0.93) and MDA levels (2.56 ± 0.73) at post-thaw (P < 0.05). The results of the study demonstrated that autologous PRP has a protective effect on cryopreservation of buck spermatozoa and the fertility effects are worthy of further study.

Effects of alpha-lipoic acid on ram semen cryopreservation and post-thaw life span

The aim of the present study was to evaluate the effects of an alpha-lipoic acid-supplemented extender on ram semen at a post-thaw stage and after incubation (6 hr). Semen samples were collected from five Kivircik Rams. Pooled semen was diluted with an egg yolk-based extender with different concentrations of alpha-lipoic acid (0.25 mmol L^-1 , 0.5 mmol L^-1 and 1 mmol L^-1 ) and without alpha-lipoic acid. Motility, plasma membrane functional integrity (HOST), acrosome integrity (FITC-Pisum sativum agglutinin) and DNA integrity (TUNEL) were assessed at post-thaw and 6 hr after incubation of the frozen-thawed semen. At the post-thaw stage, 0.25 mmol L^-1 alpha-lipoic acid had a positive effect on sperm motility and plasma membrane functional integrity compared to the control group (p < .05). At the post-incubation stage (6 hr), it was determined that the motility and plasma membrane functional integrity of the antioxidant groups were adversely affected compared to the control group (p < .05) and 1 mmol L^-1 dose of alpha-lipoic acid had a harmful effect on DNA integrity compared to the control group (p < .05). The results of the study demonstrated that alpha-lipoic acid has positive effects at post-thaw but have harmful effects on long term to ram semen.

Bayesian Analysis of the Effects of Olive Oil-Derived Antioxidants on Cryopreserved Buck Sperm Parameters

The present study evaluates the effect of olive oil-derived antioxidants, hydroxytyrosol (HT) and 3,4-dihydroxyphenylglycol (DHPG), on cryopreserved caprine sperm using Bayesian inference of ANOVA. For this proposal, sperm was collected, pooled and diluted in freezing media supplemented with different concentrations of HT, DHPG and the mixture (MIX) of both antioxidants. Sperm motility, viability, acrosome integrity, mitochondrial status, and lipid peroxidation (LPO) were assessed in fresh and frozen-thawed sperm samples. The results provided evidence that HT at low concentrations improves sperm motility and viability, and reduces the LPO. Contrastingly, DHPG and MIX exert a positive effect by reducing LPO values as concentration increases. Additionally, mitochondrial potential was reduced when samples were supplemented with HT at low concentrations and mixture of both antioxidants. Conclusively, the addition of olive oil-derived antioxidants (HT at 10 µg/mL and DHPG at 30 µg/mL) implements a protective effect in cryopreserved buck sperm. Bayesian analysis alternatives offer new possibilities to determine the repercussion of antioxidants on sperm, both quantitatively and qualitatively.

Impact of Moriamin Forte on Testicular and Epididymal Damage in Rats with Oligoasthenospermia

To investigate the effect and mechanism of action of Moriamin Forte (MF) on oligoasthenospermia (OA) in rats exposed to multiglycosides of Tripterygium wilfordii (GTW), forty male Sprague Dawley rats were randomly divided into four groups. Rats in the control group were treated with 0.5% sodium carboxymethyl cellulose. The remaining rats were administered GTW (30 mg/kg/d) for 40 d to establish an OA model. Concurrently, the groups were treated with normal saline and low-dose (100 mg/kg/d) and high-dose (200 mg/kg/d) MF, respectively. After treatment, the number and motility of sperm cells were examined. Testicular and epididymal histomorphology changes were observed. Antioxidant indicators (SOD, CAT, MDA, TAC, and Nrf2) in testicular and epididymal tissues were detected. Apoptotic and antiapoptotic indicators (Bax and Bcl2 expression) in the testicular tissue were measured by immunohistochemistry. GTW decreased sperm count and motility, damaged testicular and epididymis tissues, impaired antioxidase activity, and increased tissue MDA levels. Meanwhile, GTW upregulated the expression of Bax and downregulated the expression of Bcl2. Western blot analysis demonstrated a decrease in the Nrf2 expression in the model group. Treatment with MF improved sperm count and motility, as well as inhibited the rate of apoptosis in the rat reproductive system. Moreover, MF improved the activity of antioxidants and increased the relative expression of the antioxidant pathway-related protein Nrf2. In conclusion, MF may reverse the GTW-induced OA by modulating the expression of apoptotic and antioxidant pathway-related proteins. This study may provide a pharmacological foundation for the use of MF in OA treatment.

Comparison of spermatozoal RNA extraction methods in goats

RNA sequencing (RNAseq) has divulged newer role of spermatozoal RNA in male fertility. This study aimed to evaluate different sperm purification and RNA extraction methods for long-read RNA sequencing of poly(A) transcriptome in goat spermatozoa. Sperm samples were purified by swim-up separation using different purification medium. Spermatozoal RNA was extracted by seven different methods with additional supplementation of reducing agents in lysis buffer. poly(A) selected RNA was used for cDNA library preparation and long-read RNAseq in Nanopore sequencer. Sperm purification by 1 h swim-up resulted in higher recovery (89.20 ± 1.15%), motility (82.33 ± 1.53%), viability (88.10 ± 5.03%) and plasma membrane integrity (71.33 ± 4.51%) in sperm TALP (sp-TL) medium. A monophasic solution of GITC with phenol and DTT resulted in the highest yield of large sized RNAs (3.89 ± 0.46 ng/million cells) suitable for long-read RNAseq of poly(A) transcripts. RNAseq resulted in reads of length, ranging from 500bp to 2 Kb. A total of 123 transcripts were identified in goat spermatozoa by de novo assembly and included sperm-specific transcripts such as CATSPERG, PRM2, CYLC2, SPATA6, PLCZ1 etc. This study is the first report of long-read RNAseq of poly(A) transcriptome in goat spermatozoa.

Resveratrol supplementation and cryopreservation of buck semen

Resveratrol (Resv) was tested to assess its effects on buck semen freezability. Ejaculates of 4 bucks were collected, washed and diluted in a commercial extender at 30 °C. Extended semen was divided into 4 aliquots supplemented with increasing concentrations of Resv: 0 μM (control); 10 μM; 25 μM and 50 μM. Aliquots were cooled to 4 °C in 5h and frozen in LN₂. Thawing was performed at 37 °C for 30 s. At the 3 stages of the experiment (30 °C, 4 °C, thawing), motility (CASA), osmotic resistance (Hos test) and integrity of cytoplasm and acrosome membranes (PI/PSA staining) were assessed. Moreover, in thawed samples, the oxidative status (MDA assay) and early apoptosis (DNA fragmentation by TUNEL assay) were evaluated. Resveratrol supplementation did not affect most of the motility parameters analysed, except for total motility, ALH (lateral head displacement) and velocity distribution (P < 0.05). Functional and morphological integrity of membranes was not affected at any stage of the experiment (P > 0.05). In thawed spermatozoa, the oxidative status was not preserved by Resv (P > 0.05) while early apoptosis, was significantly decreased in the 50 μM Resv group (P < 0.05). Resveratrol did not improve buck semen freezability; the observed effects on motility and DNA were not dose dependent and not mediated by a potential anti-oxidant activity.

Positive effect of natural antioxidant oregonin from Alnus incana bark on ram semen quality stored at 5 °C for 48 h

The maintenance of high vitality and motility of ram's spermatozoa during storage at low temperatures has a crucial role for successful fertilization. This study evaluates the effect of the natural antioxidant oregonin on ram semen quality, stored at 5 °C for 48 h. Еighteen ejaculates (three repetitions for 6 ejaculates) from three local breed rams, collecting by artificial vagina, with volume > 1 ml, concentration > 1 × 10⁹/ml and mass motility >3.5 were used for chilling. Each ejaculate was separated in two equal parts, diluted with Tris-glucose-glycerol-egg yolk extender with no oregonin or supplemented with 100μМ oregonin until adjustment of the sperm concentration to 200 × 10⁶ cells/ml and stored at 5 °C for 48 h. The semen quality assessment was based on the main kinematic (by CASA analysis), morphological parameters (by BrightVit kit staining) and mitochondrial status (by MitoView staining) of the spermatozoa on 0, 24 and 48 h of storage, and on in vivo fertility test. Oregonin did not impair the morphology and kept sustained motility of ram spermatozoa stored at 5 °C for 48 h. The curvilinear velocity indicated faster movement of the oregonin treated sperms that corresponded with high percent of spermatozoa with active mitochondria in these samples. The fertilizing capacity of spermatozoa was preserved and pregnancy rate in the experimental group was 80% versus 60% in control. In conclusion, this study provides a new data about positive effect of the natural antioxidant oregonin, supplemented to the extender, on chilled ram semen quality, including fertilizing ability.

Butylated hydroxytoluene protects bull sperm surface protein-P25b in different extenders following cryopreservation

Aim

The aim of this study was to investigate the effects of different concentration of butylated hydroxytoluene (BHT) on sperm membrane surface protein "P25b" from cryopreserved bull semen in either lecithin based Bioxcell^® (BX) or two egg-yolk based extenders, tris-egg yolk (TEY), and citrate-egg yolk (CEY).

Materials and Methods

Forty-five semen samples, 15 each were extended with either BX, TEY, or CEY extender which contained different concentrations (0.0 - control, 0.5, 1.0, 1.5, 2.0, and 3.0 mM/mL) of BHT. The extended semen samples were frozen at a concentration of 20×10⁶/mL in 0.25 mL straws and stored in liquid nitrogen for 2weeks. The frozen samples were thereafter thawed, proteins extracted and analyzed for quantities of protein P25b through direct sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel densitometry. Peptides were confirmed by Western blotting (WB).

Results

Results showed that supplementation of BHT improved (p<0.05) quantity of protein P25b at concentrations of 0.5mM/mL for BX and at 1.0 mM/mL for TEY and CE when compared with the controls and other treatments.

Conclusion

BHT supplementation at 0.5 in BX and 1.0 mM/mL in TEY and CEY has protected bull sperm fertility marker protein P25b in frozen-thawed bull sperm.

Goat semen cryopreservation with rainbow trout seminal plasma supplemented lecithin-based extenders

The objective of this study was to determine the optimum concentrations of rainbow trout seminal plasma (RTS) supplemented extenders for goat semen quality at post-thaw and after incubation. Five sexually mature Saanen goat (Capra aegagrus hircus) were used for semen collection. Pooled semen was diluted with soybean lecithin-based extender without RTS (control) or supplemented with different concentrations of RTS (1%, 2%, 4% or 8%), at a final concentration of 150 × 10⁶ spermatozoon/ml. Sperm motility, plasma membrane functional integrity (HOST), damaged acrosome (PSA-FITC), mitochondrial activity (rhodamine123) and DNA integrity (TUNEL) were evaluated. Spermatological parameters were evaluated at post-thaw and after 6 hr incubation. RTS8 group preserved sperm motility, acrosomal integrity, plasma membrane functional integrity and mitochondrial function better than the control group (p < .05). The study demonstrated that RTS supplemented lecithin-based extenders have useful effects on goat spermatozoa. In addition, the results of the current study represented the positive effect of using 8% RTS supplemented extender.

Lycium barbarum and Laminaria japonica polysaccharides improve Cashmere goat sperm quality and fertility rate after cryopreservation

Cashmere goat is known for the highest cashmere yield and best fiber quality. Here, the effects of Lycium barbarum polysaccharide (LBP) and Laminaria japonica polysaccharide (LJP) on goat sperm quality were investigated. Results showed that the sperm motility, mitochondrial activity, and membrane and acrosome integrity were significantly higher with 4.0 mg/mL LBP and 1.0 mg/mL LJP supplementations than in the control (P < 0.05), respectively. Higher SOD, CAT, and GSH-Px levels were observed in 4.0 mg/mL LBP and 1.0 mg/mL LJP groups than control group (P < 0.05). Sperm characteristics with 2.0 + 1.0 mg/mL LBP + LJP supplementation significantly improved compared to that with other treatments (P < 0.05). Compared to the control treatment, the non-return rate (NRR) were higher in the LBP + LJP (2.0 + 1.0 mg/mL) group (P < 0.05). These results suggest that LBP and LJP enhance cryo-protective effects on goat spermatozoa, and that 2.0 + 1.0 mg/mL LBP + LJP addition to the extender during cryopreservation is beneficial to the Cashmere goat breeding industry.

Effect of sperm pooling with seminal plasma collected in breeding or nonbreeding season on Saanen goat sperm cryosurvival

The aim of this study was to determine the effects of both the removal of seminal plasma (SP) and the pre-freezing addition of seminal plasma collected during the breeding or nonbreeding season on goat sperm survival after thawing. Semen samples were pooled. One aliquot of pooled semen was used as a control group. Four aliquots were then centrifuged, and the SP was removed in Group I, pipetted but not removed in Group II, removed and then pooled for animals collected in the breeding season in Group III and removed and pooled for animals collected in the nonbreeding season in Group IV. Group samples were frozen and then were assessed for rates of sperm motility, plasma membrane functional integrity hypo-osmotic swelling test (HOST), defective acrosomes (FITC-PSA), DNA fragmentation (TUNEL) and mitochondrial membrane damage (Rhodamine 123). The results showed that pre-freezing addition of SP collected in breeding season maintained post-thaw sperm characteristics at 0 hr better than SP removal group, but removing seminal plasma showed positive effects on spermatozoa, as incubation time increased to 5 hr. In conclusion, the pre-freezing addition of seminal plasma did not maintain post-thaw goat sperm characteristics as successfully as in the groups with seminal plasma removed after an incubation period.

Extender Supplementation with Antioxidants Selected after the Evaluation of Sperm Susceptibility to Oxidative Challenges in Goats

This study aimed to detect the most deleterious ROS for goat sperm and then supplemented the extender with a proper antioxidant. For this, 12 adult goats (aged 1-7) were used. Fresh samples were submitted to challenge with different ROS (superoxide anion, hydrogen peroxide, and hydroxyl radical) and malondialdehyde (MDA-toxic product of lipid peroxidation). After experiment 1, sperms were cryopreserved in extenders supplemented to glutathione peroxidase (Control: 0 UI/mL; GPx1: 1 UI/mL; GPx5: 5 UI/mL, and GPx10: 10 UI/mL) and catalase (Control: 0 UI/mL; CAT60: 60 UI/mL; CAT120: 120 UI/mL, and CAT240: 240 UI/mL). Each sample was evaluated by motility, plasma membrane integrity (eosin/nigrosin), acrosome integrity (fast green/rose bengal), sperm morphology, assay of the sperm chromatin structure, mitochondrial activity (3,3-diaminobenzidine), and measurement of lipid peroxidation (thiobarbituric acid reactive substances [TBARS]). It was possible to observe a mitochondrial dysfunction (DAB-Class IV) and low membrane integrity after hydrogen peroxide action. However, the high rates of TBARS were observed on hydroxyl radical. CAT240 presents the lower percentage of plasma membrane integrity. It was possible to attest that hydrogen peroxide and hydroxyl radical are the more harmful for goat sperm. Antioxidant therapy must be improving perhaps using combination between antioxidants.