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Mother Mature Naked

Milk glands, dissected out and collected from Glossina morsitans centralis (Machado) females, artificially inoculated at the third-instar larval stage with a virus suspension obtained from hypertrophied salivary glands of wild-caught virus-infected Glossina pallidipes (Austen), were processed for routine electron microscopy and examined for pathological changes. They were compared to milk glands dissected out from normal female G.m. centralis at the same stage of pregnancy cycle. Upon dissection there were notable physical differences between control and virus-infected milk glands. Histologically, some areas of the gland developed severe degeneration while other areas developed less severe pathological changes. Ultrastructural studies revealed the presence of virus particles in the secretory cell nuclei and within the cytoplasm and also showed that the nucleus was the site of virogenesis with mature naked virions budding through the nuclear membrane and acquiring the envelope from the nuclear membrane. Milk glands from normal females showed normal cellular organization of the secretory cells and secretory vesicles around the collecting gland lumen. The demonstration of virus particles in the secretory cell nuclei and cytoplasm suggests another mode of transmission of the virus from the infected mother to the larva in utero.

mother mature naked

Another relevant issue associated with the requirement of protection and care of offspring is related to the maturity it has at parturition (precocial vs. altricial young; selective vs. non-selective bond) [24]. According to this, altricial species such as canids, rodents, marsupials, cricetids, and felines [25], are those that are more immature at birth, unable to move without help, require continuous parental protection during the first weeks of life, and must be groomed and provided with food [25]. Canine puppies, for example, are typically born with non-functional ears and eyes and are severely limited in regards to mechanical movement [26], so they depend on the dam and on their maternal behavior to survive. In this species, some mothers form a nest in a safe place where the young (born with an immature musculoskeletal system) are safe from predators [14]. Sows have the peculiarity that, although the newborn piglet has one of the highest motor and sensory developments, the mother builds a nest and the litter remains there for approximately one week [25].

Neurodevelopmental differences between altricial, precocial, and semi-altricial species. According to the type of species, newborns from altricial, precocial, and semi-altricial females establish a different degree of bonding. In the case of precocial species, whose cerebral development starts during gestation, the time they require for maternal nursing is shorter since they can stand and move freely almost immediately after birth. In contrast, the maturation of sensorial systems in altricial species occurs during the postnatal period, where they are completely dependent on the mother to survive. Semi-altricial species are in between; while some of their senses are functional at birth, the mother nurses them until they are highly independent after several days after parturition.

In contrast, offspring from precocial species (e.g., bovines, goats, sheep, and equines) can feed themselves, and follow their mother after birth, which is associated with a rapid recognition process between the two [36]. They have a completely functional vision and hearing since birth, and a locomotor system that is sufficiently well-developed to allow them to stand effectively and start suckling [37]. They also have efficient thermoregulatory systems and may be quite independent at an early age [38,39]. In some cases, precocial species hide and do not follow their mothers; the mothers move approximately 100 m away from the young to graze and return to nurse them. As these young do not move, their energy requirements are minimal, so all the food they consume translates into rapid growth [40,41].

In the case of dogs, a sensitive period is considered to be established during the first two weeks of life, when they are highly dependent on their mother, and it is known that alteration in the maternal care or attachment during this period can negatively influence the behavior in adult dogs [63]. For kittens, a similar amount of time is considered the critical period, and during this time the mother is dedicated to nursing and feeding the newborns, only spending time away from the newborns when they become three weeks old [64].

For newborn rabbits, the nest is essential to survival during the first weeks of life due to the limited assistance of the mother at birth. The doe only feeds the pups once or twice per day for 4 to 5 weeks [98]. The suckling sessions have a duration of about 3 to 4 min. Therefore, the rest of the time the newborns huddle into the insulated nest material to save energy and prevent hypothermia [99].

Other species, such as marsupials, are born in an embryonic stage and immediately after birth reach the pouch and nipple of the mother to fully develop outside the uterus [27]. For these species, the role of a nest can seem less important; however, as Rowland et al. [100] studied in arboreal marsupials, tree hollows, instead of nest boxes, aid in the thermostability of neonate marsupials. According to the results, microclimates inside tree hollows provide a consistent thermal environment with temperatures no higher than 38 C, in comparison to the nest boxes where the highest recorded temperature was 52 C, a value that can trigger heat stress in the newborn.

Influence of pain and aversion on maternal behavior in altricial species. Although pain is a physiological trait in the parturition process, if dystocia occurs and the pain is prolonged in the mother, the activation of nociceptors (A-delta and C fibers) activates the sympathetic nervous system, and the consequent release of catecholamines and glucocorticoids. Moreover, the conscious recognition of pain in the somatosensorial cortex alters maternal behavior and reduces milk production, resulting in a negative trait for both the mother and the offspring. On the other hand, the activation of aversion pathways in non-parturient females prevents them from maternal responsiveness. However, in species such as rodents, short periods of pup exposure elicit similar responses in multiparous, parturient, and lactating animals. EPN: entopeduncular nucleus; LH: lateral hypothalamus; LHb: lateral habenula; LPO: lateral preoptic area; MS: medial septal nucleus; PFC: prefrontal cortex; VP: ventral pallidum; VTA: ventral tegmental area. 041b061a72


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