Invasive alien species are a major threat to long-term survival of local native species [1]. Deployment of control programs to limit the expansion of alien populations is one of the goals of the EC [2]. Gray squirrel is one of the 100 worst invasive alien species (IUCN list). This work, being part of the European project LIFE13 BIO/IT/000204 U-SAVEREDS, aimed at safeguarding the native red squirrel (Sciurus vulgaris) in central Italy. To this end, we studied a gray squirrel alien population using 45 female carcasses, 18 ovariectomized females and 24 orchidectomized males obtained from the 2016-2018 management activities. Traps were baited with hazelnuts and check two times per day, to minimize stress to captured animals [4]. Female animals were euthanized by CO2 inhalation, following EC and AVMA guidelines [4], while the males and females gonadectomized were anesthetized with dexmedetomidine ketamine and, as needed, maintained with sevoflurane in 100% O2. Individual fecundity, in terms of seasonal (spring, summer) and total (annual = spring + summer) litter size, was determined by counting the number of uterine-placental scars which are formed by the detachment of each embryo’s placenta at parturition, thus allowing to estimate the total number of young born from a single female during the entire reproductive season (spring, summer) [4]. Uterine scars were identified after staining which reveals dark pigments of macrophages involved in processes of repairing the endometrium after detachment of the hemochorial placenta [4]. Sixty-nine % of examined females produced litters (37.8 % a single litter, 31.2% two litters). Spring litters (3.55 ± 1.57 scars/female) were larger (P<0.007) than summer ones (2.14 ± 1.46 scars/female); annual fecundity was 4.52 ± 1.88 scars/female, ranging from 2 to 7 births. On ovaries collected from ovariectomized squirrels during a whole year, we always found graafian follicles. Spermatozoa were observed in the germinal epithelium of the seminiferous tubules along with a great number of sperm cells in the epididymis, with testes in scrotal position, attesting an active spermatogenesis. Taken together, our findings confirm that this gray squirrel population, having a high reproductive success due to a potential non-seasonal ovarian cyclic activity, is well adapted to the new environment and thus is greatly dangerous for the native red squirrel.
REPRODUCTIVE PATTERNS IN A POPULATION OF GRAY SQUIRREL (Sciurus carolinensis) IN CENTRAL ITALY: LITTER SIZE AND GENITAL TRACT MORPHOLOGICAL SEASONAL CHANGES
Maranesi M
;Mercati F;Bufalari A;Crotti S;Dall’Aglio C;Nannarone S;Petrucci L;Moretti G;Boiti C;Zerani M
2018
Abstract
Invasive alien species are a major threat to long-term survival of local native species [1]. Deployment of control programs to limit the expansion of alien populations is one of the goals of the EC [2]. Gray squirrel is one of the 100 worst invasive alien species (IUCN list). This work, being part of the European project LIFE13 BIO/IT/000204 U-SAVEREDS, aimed at safeguarding the native red squirrel (Sciurus vulgaris) in central Italy. To this end, we studied a gray squirrel alien population using 45 female carcasses, 18 ovariectomized females and 24 orchidectomized males obtained from the 2016-2018 management activities. Traps were baited with hazelnuts and check two times per day, to minimize stress to captured animals [4]. Female animals were euthanized by CO2 inhalation, following EC and AVMA guidelines [4], while the males and females gonadectomized were anesthetized with dexmedetomidine ketamine and, as needed, maintained with sevoflurane in 100% O2. Individual fecundity, in terms of seasonal (spring, summer) and total (annual = spring + summer) litter size, was determined by counting the number of uterine-placental scars which are formed by the detachment of each embryo’s placenta at parturition, thus allowing to estimate the total number of young born from a single female during the entire reproductive season (spring, summer) [4]. Uterine scars were identified after staining which reveals dark pigments of macrophages involved in processes of repairing the endometrium after detachment of the hemochorial placenta [4]. Sixty-nine % of examined females produced litters (37.8 % a single litter, 31.2% two litters). Spring litters (3.55 ± 1.57 scars/female) were larger (P<0.007) than summer ones (2.14 ± 1.46 scars/female); annual fecundity was 4.52 ± 1.88 scars/female, ranging from 2 to 7 births. On ovaries collected from ovariectomized squirrels during a whole year, we always found graafian follicles. Spermatozoa were observed in the germinal epithelium of the seminiferous tubules along with a great number of sperm cells in the epididymis, with testes in scrotal position, attesting an active spermatogenesis. Taken together, our findings confirm that this gray squirrel population, having a high reproductive success due to a potential non-seasonal ovarian cyclic activity, is well adapted to the new environment and thus is greatly dangerous for the native red squirrel.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
