Comparative quantitative investigations on brains of wild cavies (Cavia aperea) and guinea pigs (Cavia aperea f. porcellus). A contribution to size changes of CNS structures due to domestication

Intraspecific allometric calculations of the brain to body size relation revealed distinct differences between 127 (67; 60) ancestral wild cavies and 82 (37; 45) guinea pigs, their domesticated relatives. The dependency of both measures from one another remained the same in both animal groups but the brains of guinea pigs were by 14.22% smaller at any net body weight. Consistent with results in other species the domestication of Cavia aperea is also characterized by a decrease of brain size. Fresh tissue sizes of the five brain parts medulla oblongata, cerebellum, mesencephalon, diencephalon and telencephalon were determined for 6 cavies and 6 guinea pigs by the serial section method. Additionally the sizes of 16 endbrain structures and those of the optic tract, the lateral geniculate body and the cochlear nucleus were measured. Different decrease values resulted for all these structures concomitant with domestication as was calculated from the amount of total brain size decrease and average relative structure values in the wild as well as the domesticated brain. The size decrease of the entire telencephalon (−13.7%) was within the range of the mean overall reduction as similarly was the case for the total neocortex (−10.7%) whereas the total allocortex (−20.9%) clearly was more strongly affected. The size decrease of the olfactory bulb (−41.9%) was extreme and clearly higher than found for the secondary olfactory structures (around −11%). The primary nuclei of other sensory systems (vision, audition) were decreased to less extent (lateral geniculate: −18.1%; cochlear nucleus: −12.6%). Mass decreases of pure white matter parts were nearly twice as high in contrast to associated grey matter parts (neocortex white versus grey matter; tractus opticus versus lateral geniculate body). The relatively great decrease values found for the limbic structures hippocampus (−26.9%) and schizocortex (−25.9%) are especially notable since they are in good conformity with domestication effects in other mammalian species. The findings of this study are discussed with regard to results of similar investigations on wild and domesticated gerbils (Meriones unguiculatus), the encephalization of the wild form, the special and species-specific mode and duration of domestication and in connection with certain behavioral changes as resulted from comparative investigations in ethology, socio-biology, endocrinology and general physiology.     

Comparative allometric investigations on the skulls of wild cavies (Cavia aperea) versus domesticated guinea pigs (C. aperea f. porcellus) with comments on the domestication of this species

Bivariate allometric calculations were performed to quantitatively compare skulls of wild cavies with domesticated guinea pigs. Descendents of wild caught Cavia aperea from eastern regions of the species’ distribution area were used, as well as unselected domesticated breeds of guinea pigs differing in outer appearance. The individuals of both groups were kept under similar environmental conditions. Altogether 19 parameters on the skulls and the body weights were used for the analyses. These parameters were studied in relation to greatest skull length and to body size. As a general result the diverse parameters are in most cases significantly different between both groups which is interpreted as a special result of unconsciously selected and genetically determined intraspecific changes concomitant with domestication. The skull does not change in total under the domestication process but in a mosaic manner. However, for the mosaic changes of the diverse parameters in relation to skull length a different picture is valid as related to body weight. This is caused by the fact that the skull of guinea pigs is around 5% shorter independent of the body size, a common effect of domestication also described for other species. Thus, skull length is not an appropriate parameter for body size with respect to such intraspecific investigations, although normally used for the characterization of species in interspecific comparisons of museum materials.Altogether in relation to body weight most of the parameters describing the fascial portion of the skull are shorter in the guinea pig, especially the palatine, the diastema and the mandible but also the nasalia and frontalia lengths as well as the breadth of the rostrum and the zygomaticum are smaller. Most of the occipital skull measures are additionally smaller in the guinea pigs. This is clearly the case for the length and the breadth of the braincase and for the tympanic bulla. The braincase volume is 16.2% smaller, a value only slightly different when compared with the degree of brain size decrease due to domestication as reported for this species in other investigations.     

Variability of branching of the a. coeliaca (truncus coeliacomesentericus) in the guinea pig (Cavia aperea f. porcellus)

The authors studied branching of the a. coeliaca (the truncus coeliacomesentericus) in a group of Peruvian short-haired guinea pigs, with special reference to its variability. After the animals had been anaesthetized, their arterial bed was injected with red-dyed latex, fixed and dissected. In all 30 guinea pigs (100%), blood was supplied to the unpaired organs of the abdominal cavity by a truncus coeliacomesentericus arising from the aorta abdominalis at fundus ventriculi level. In 53.3% of the cases, the truncus coeliacomesentericus divided into a truncus gastrolienalis sending out an a. gastrica sinistra and an a. lienalis, and to a truncus hepatomesentericus which split up into an a. hepatica communis and a. mesenterica cranialis. An a. coeliaca (tripus Halleri) was found in only one guinea pig (3.3%), as a branch of the truncus coeliacomesentericus. In the remaining cases, the truncus branched in the most varied ways. The a. gastrica sinistra was most frequently (60%) a branch of the truncus gastrolienalis. In 21 cases (70%) there was a single a. gastrica sinistra and in nine cases (30%) it was doubled. In 29 cases (96.7%) the a. hepatica communis arose from the truncus hepatomesentericus. The classic type of division of the a. hepatica communis to an a. hepatica propria and an a. gastroduodenalis was observed in every case (100%). In 100% of the cases, the a. hepatica propria terminated in a r. dexter and a r. sinister to the liver. An a. cystica, as a direct branch of the a. hepatica propria, was formed in 28 cases (93.3%). In every case (100%) the a. pancreaticoduodenalis cranialis was a branch of the a. gastroduodenalis. An a. gastrica dextra was recorded in only eight cases in the series (26.7%)--in 23.3% as a branch of the a. hepatica propria and in 3.3% as a branch of the a. cystica. Duplication of this artery was found in one case (3.3%). An a. lienalis was found in 28 cases (93.3%), as a direct branch of the truncus gastrolienalis; in two cases (6.7%) it was doubled. An a. gastroepiploica sinistra and a. gastroepiploica dextra were present in 100% of the cases. Inter-organ arterial anastomoses were found in 22 guinea pigs (73.3%)--between the spleen and the stomach (36.7%), between the pancreas and the stomach (10%), between the stomach, spleen and pancreas (10%) and, in the remaining cases, as various combinations of these connections.(ABSTRACT TRUNCATED AT 400 WORDS)     

Origin of the v. portae and variability of its tributaries in laboratory animals. II. The guinea pig (Cavia aperea f. porcellus)

The authors investigated the origin of the v. portae and variability of its main tributaries in 30 adult guinea pigs (Cavia aperea f. porcellus). The venous bed was visualized by means of blue-dyed latex. The v. portae was formed the most frequently - in 17 cases (56.7%) - by the confluence of three veins - the v. mesenterica cranialis, the v. lienalis and the v. gastroepiploica dextra; less often it was formed from four or five tributaries and in one case only it was formed by union of the v. mesenterica cranialis and the v. lienalis. The v. gastrica sinistra was a tributary of the v. lienalis in 24 cases (80.0%). It arose on the ventral and the dorsal surface of the stomach, in the region adjacent to the curvatura minor ventriculi. In 21 cases (70.0%) it was joined by an independent v. cardiaca. The v. lienalis originated in the hilus lienis, usually as a result of the union of two venous trunks. Inter-organ anastomoses were found in 26 cases (86.7%); in 10 cases (33.3%) they occurred simultaneously between the spleen and the stomach and between the spleen and the pancreas, while in 16 cases (53.3%) they connected the superior pole of the spleen with the stomach. An independent v. gastroepiploica dextra was present in 19 cases (63.3%) as a tributary of the v. portae. In 22 cases it was joined by the v. pylorica. A v. pancreaticoduodenalis cranialis was present in 27 cases (90.0%). In 18 cases (60.0%) it united with the v. gastroepiploica dextra to form a common trunk, the v. gastroduodenalis, which joined the v. portae; in two cases (6.7%) it was an independent tributary of the v. portae. In six cases it was connected with the v. lienalis and in three cases (10.0%) it was replaced by a few vv. pancreaticae emptying into the v. lienalis. A typical v. pancreaticoduodenalis caudalis, as a tributary of the a. mesenterica cranialis, was found in 19 cases (63.3%). In two cases, together with the v. pancreaticoduodenalis cranialis, it formed a single trunk (the v. pancreaticoduodenalis communis). A comparison of the v. portae and its tributaries in the guinea pig and the cat has so far not brought to light any significant morphological differences relative to their different zoological classification and their different modes of life.     

Age at maturity in cavies and guinea-pigs (Cavia aperea and Cavia aperea f. porcellus): influence of social factors

Age at maturity, a particularly important parameter in the life history of small mammals, contributes greatly to fitness. Social influences on age at maturity have been demonstrated for altricial rodents, in particular, mice. Nothing is known about such effects in precocial small mammals. Wild cavies Cavia aperea are born in a highly precocial state and mature early in life, briefly after weaning. We investigated whether the wild cavy C. aperea and the domestic guinea-pig Cavia aperea f. porcellus reach maturity earlier in the presence of adults of the opposite sex. Juvenile females kept in pairs without males showed first vaginal opening (=oestrus) when 59 days old in cavies and at about 40 days in the guinea-pig. However, in the company of adult males, cavy females kept in pairs reached maturity when about 30 days old, and guinea-pig females when 26 days old. Most cavy females experienced successful pregnancy following first vaginal opening. In cavies, female mass at birth and at first oestrus was not correlated with age at first oestrus. In guinea-pigs, birth mass predicted age at maturity only when a male was present. The growth rate from birth to first oestrus related to age at first oestrus. In the wild cavy, the presence of a male appeared to influence maturation more between days 25 and 30 than earlier in life. Male C. aperea matured and had fully descended testes when about 65–70 days old. All male cavies produced abundant motile sperm from day 75. First successful copulations occurred at about the same age. Surprisingly, the priming effect of the presence of an adult male on female maturation proved stronger in these highly precocial caviomorphs than in altricial rodents investigated so far.     

Immunoglobulin genomics in the guinea pig (Cavia porcellus)

In science, the guinea pig is known as one of the gold standards for modeling human disease. It is especially important as a molecular and cellular biology model for studying the human immune system, as its immunological genes are more similar to human genes than are those of mice. The utility of the guinea pig as a model organism can be further enhanced by further characterization of the genes encoding components of the immune system. Here, we report the genomic organization of the guinea pig immunoglobulin (Ig) heavy and light chain genes. The guinea pig IgH locus is located in genomic scaffolds 54 and 75, and spans approximately 6,480 kb. 507 V(H) segments (94 potentially functional genes and 413 pseudogenes), 41 D(H) segments, six J(H) segments, four constant region genes (μ, γ, ε, and α), and one reverse δ remnant fragment were identified within the two scaffolds. Many V(H) pseudogenes were found within the guinea pig, and likely constituted a potential donor pool for gene conversion during evolution. The Igκ locus mapped to a 4,029 kb region of scaffold 37 and 24 is composed of 349 V(κ) (111 potentially functional genes and 238 pseudogenes), three J(κ) and one C(κ) genes. The Igλ locus spans 1,642 kb in scaffold 4 and consists of 142 V(λ) (58 potentially functional genes and 84 pseudogenes) and 11 J(λ) -C(λ) clusters. Phylogenetic analysis suggested the guinea pig's large germline V(H) gene segments appear to form limited gene families. Therefore, this species may generate antibody diversity via a gene conversion-like mechanism associated with its pseudogene reserves.     

Urethral catheterization of the male guinea pig (Cavia porcellus)

Urethral catheterization of the male guinea pig has potential diagnostic, therapeutic, and research applications. Urethral catheter placement requires an understanding of the unique anatomy of the lower urinary tract in order to avoid iatrogenic injury to the urethra and to ensure successful catheterization.     

Urethral catheterization in the female guinea pig (Cavia porcellus)

Urethral catheterization of the female guinea pig has potential diagnostic, therapeutic and research applications. Urethral catheter placement in the female guinea pig is relatively easy to carry out and has fewer potential complications than does catheter placement in male guinea pigs.     

True pregnancy toxemia (preeclampsia) in the guinea pig (Cavia porcellus)

In this study, normal nonpregnant, normal full-term pregnant, fasting ketotic and spontaneous pregnancy toxemic guinea pigs were compared to define the mechanism of this disease. In addition to conventional clinical, laboratory and pathologic studies, arterial blood pressure (thoracic and abdominal aortic) measurements and angiography were used. The results showed that in spontaneous cases of pregnancy toxemia, there is an aortic compression just caudal to the renal arteries. This compression reduced the aortic diameter by 22% of prerenal level as compared to 10% for fasting ketotic and normal pregnant guinea pigs. The aortic compression also resulted in a 30% postcompression reduction in blood pressure. No pressure differences were seen in the other groups. The postulated etiology for true toxemia of pregnancy in guinea pigs is, therefore, similar to that of man where aortic compression produces uterine ischemia and the resultant syndrome.     

阿根廷淡水大米草沼泽中野生豚鼠的种群统计和微生境的利用

本文研究了秋冬季节淡水大米草(Spartina densiflora)沼泽中野生豚鼠(Cavia a perea)的丰度、繁殖和微生境利用,以及其对当地植被和棉鼠类(Sigmodontine)啮齿动物的影响。野生豚鼠喜好S.densiflora覆盖度高的生境。繁殖个体(成体)主要利用矮草为主的斑块,幼体则主要利用禾本科植物为主的斑块。结果说明,野生豚鼠微生境的利用受捕食风险和食物种类的影响。在淡水沼泽中,野生豚鼠的丰度、繁殖、体重和微生境利用没有季节性变化,它们对植物的取食和活动跑道的建造对植被结构和同域的啮齿类动物没有负面影响。通过对具有中度季节性变化的淡水生境中的豚鼠种群和具有高度季节变化的草地和路边中的豚鼠种群进行比较,表明野生豚鼠的种群动态以及豚鼠种群对植被和与其共生的啮齿动物群落的影响都受到冬季植被盖度的限制。     

Sexual dimorphism in the craniofacial growth of the guinea pig (Cavia porcellus)

Variation between the sexes during ontogeny is frequently overlooked in discussions of the phylogenetic patterns of adult sexual dimorphism. Different growth trajectories can produce identical degrees and direction of adult dimorphism and the possibility exists that similarities in adults may be the result of differing growth patterns, suggesting independent evolutionary pathways among species to the seemingly identical adult morphology. We quantified the sexual dimorphism in craniofacial skeletal growth of Cavia porcellus, the guinea pig, using longitudinally collected radiographs. Guinea pigs have male-biased sexual dimorphism in size and in growth parameters, despite literature reports to the contrary. These results, analyzed with equivalent data for five species of rodents, and two outgroups representing similarly sized mammals, a rabbit and a marsupial, indicate that some aspects of sexual differences in growth follow phylogenetic lines, while others are a function of whether the species has male- or female-biased dimorphism.     

Ontogenesis of the electroretinogram in a precocial mammal, the guinea pig (Cavia porcellus)

1. Ontogenesis of the electroretinogram, the mass electrical response of the retina to flash light stimuli, was studied in the guinea pig (Cavia porcellus), a precocial species with visual function at birth. 2. a-Wave components, b-wave, oscillatory potentials, slow PIII, and c-wave responses to flash stimuli developed between 55 and 64 days of gestation (full term is 68-69 days). 3. a-Waves attributable to photoreceptor functions were fully mature at 60 days. 4. ERG development lagged behind the reported critical milestones in retinal development; its prenatal onset indicates that no history of light entrainment is required for initiation of a mature ERG response.     

Mandibular movement and muscle activity during mastication in the guinea pig (Cavia porcellus)

Optoelectronic analysis of mandibular movement and electromyography (EMG) of masticatory muscles in Cavia porcellus indicate bilateral, unilateral, and gnawing cycles. During bilateral and unilateral cycles, the mandibular tip moves forward, lateral, and down during the lingual phase of the power stroke to bring the teeth into occlusion. EMG activity is generally asymmetric, with the exception of activity of the temporalis muscle during bilateral cycles. During gnawing cycles, the mandible moves in an anteroposterior direction that is opposite that during bilateral and unilateral chew cycles. Bilateral and unilateral cycles of pellets were significantly longer than carrot. With the exception of the width of bilateral cycles, the magnitude of cycle width, length, and height during the mastication of carrots was greater than that during the mastication of pellets. Significant differences exist between EMG durations during mastication of pellets and carrots. The lateral pterygoid displays continuous activity during gnawing cycles. Significant differences also exist in the durations of EMG activity between the working and balancing side during all three cycle types. High level activity of balancing side temporalis and anterior belly of digastric (ABD) during bilateral cycles occurs during rotation and depression of the mandible during the power stroke. The temporalis apparently provides a ?braking”? or compensatory role during closing and power strokes. Differences between Cavia masticatory patterns and those shown by Rattus and Mesocricetus are apparently due to differences in dental morphology, occlusal relationships, and, possibly, the poorly developed temporalis in Cavia. The large number and wide diversity of rodent groups afford students of mammalian mastication an opportunity to investigate and compare different masticatory specializations.     

Ancient and modern steps during the domestication of guinea pigs (Cavia porcellus L.)

To test whether there are differences between living lineages of domestic guinea pigs Cavia porcellus , we studied 118 specimens from six breeds collected along six Andean countries as well as 15 from the wild cavy species ( Cavia tschudii ). The mean weight and body length of 15 adult wild cavies (295±31 g, 242±8.3 mm) were significantly smaller than 25 creole guinea pigs from Bolivia and Chile (639±157 g, 287±23.7 mm, respectively). Eighteen laboratory/pet guinea pigs (including the English Pirbright breed) were also smaller (900±173 g, 308±21 mm) than 25 improved ones from Peru (Tamborada breed, 1241±75.4 g, 317±12 mm) and Ecuador (Auqui breed, 1138±65.5 g, 307±8 mm). Similar size increases appeared in the first axis of a principal component analysis of six skeletal measurements, recovering 84% of total variation. Phylogenetic and haplotype analyses of complete cytochrome b gene sequences consistently joined all 22 domestic individuals (13 shared unambiguous substitutions, 100% bootstrap in 1000 replicates), probably from a single first ancient domestication in the western Andes. Six laboratory/pet sequences were also joined within a common branch (six shared substitutions, 96% bootstrap), probably from a documented European second phase. By contrast, those from improved Auqui joined a northern creole subgroup (one shared substitution, 84% bootstrap), and those from Nativa and improved Tamborada clustered together and with a southern creole subgroup (four shared substitutions, 86% bootstrap); this suggests at least two independent modern events during a more complex third phase, producing two improved guinea pigs selected for size and meat. Cavia tschudii sequences showed some unexpected geographic variation.