Midventral Gland Research Articles

The Effect of Photoperiod Duration on Humoral Innate and Humoral Adaptive Immune Responsiveness in Campbell’s Dwarf Hamster

We studied the humoral innate immune responsiveness (HII), i.e. a hemolysis of rabbit erythrocytes by complement proteins, and adaptive humoral (antibody production) immune responsiveness (AHI) to SRBC, morphological and hormonal reproductive characteristics and stress level in male Campbell hamsters kept under long-day (LD; 16D: 8N) and short-day (SD; 8D: 16N) photoperiods. The results indicate lower HII, but not AHI in SD. In SD males we observed body mass, anogenital distance, midventral gland size and level of testosterone in the peripheral blood (but not the level of cortisol) decreased. Comparison of SD non-responders, SD responders and LD individuals demonstrated a statistically significant increase of HII in SD photosensitive hamsters, but not in non-responders compared to LD. There was no link between HII and AHI, which indicates an independent photoperiodic responsiveness of different branches of the immune system in Campbell’s hamster.

On the winter enhancement of adaptive humoral immunity: hypothesis testing in desert hamsters (Phodopus roborovskii: Cricetidae, Rodentia) kept under long-day and short-day photoperiod.

We tested the winter immunity enhancement hypothesis (WIEH) on male desert hamsters (Phodopus roborovskii) kept under long-day (LD) and short-day (SD) photoperiods. We assumed that under SD in a laboratory, the adaptive humoral immune responsiveness to the antigenic challenge would be enhanced due to the lack of winter physical stressors and food shortages and/or because of the action of an endogenous winter bolstering mechanism, while under LD the immune responsiveness would be suppressed by the activity of the reproductive system. The results support the WIEH in part. We did not find a difference in antibody production in response to sheep erythrocytes between SD and LD hamsters, but SD males had the lower number of granulocytes and the higher number of lymphocytes in white blood cell counts. Reproductive activity was lower in SD males. These males demonstrated an increase in their mass-specific resting metabolic rate, their mass-specific maximal metabolic rate and their level of cortisol. The result of a generalized linear model analysis indicates the negative effect on secondary immunoresponsiveness to sheep erythrocytes of mid-ventral gland size, the organ characterizing individual reproductive quality, and designates a tradeoff between antibody production and reproductive effort. The mass-independent maximal metabolic rate also negatively affected antibody production, indicating a tradeoff between maximal aerobic performance and the adaptive immune function. The higher stress in SD males seems to be the most likely reason for the lack of the effect of daylight duration on antibody production.

Chemical Signals of Conspecifics and Their Role in Seasonal Relationships in the Mongolian Hamster (Allocricetulus curtatus) (Cricetinae, Rodentia)

Abstract—The hormonal response of Mongolian hamster Allocricetulus curtatus males to the urine and midventral gland secretion (MVGS)) of conspecific females during several seasons was studied. The animals were kept under natural photoperiod and temperature. In autumn no significant changes in the testosterone level in the blood of males in response to any of the exposed signals were observed. In winter and summer, this parameter increased in response to the diestrous female odors of urine and MVGS . In the spring the urine of conspecific estrous females stimulated a significant increase in the levels of both testosterone and cortisol. Moreover, the cortisol level did not increase in response to exposure of the odors of diestrous females in any season of the year. The level of progesterone significantly increased only when MVGS was exposed in the spring and summer periods, and the absolute values of this parameter were significantly higher in spring than in summer. Differences in responses to chemical signals in two closely related species (Eversmann’s and Mongolian hamsters) are discussed in connection with the peculiarities of the intraspecific social relationships.

Seasonal Changes in the Hormonal Response of Male Eversmann’s Hamsters (Allocricetulus eversmanni, Cricetinae, Rodentia) to Olfactory Signals from Conspecific Females

Reproductive success demands both the male and female reaching a particular physiological status, which is usually stimulated in rodents by certain olfactory signals. The hormonal response of male Eversmann’s hamster (Allocricetulus eversmanni) to the natural excretions (urine, midventral gland secretion (MVGS) of conspecific females was studied during several seasons of the year, with the animals kept in conditions of natural lighting and temperature. In the fall, no reliable changes in the testosterone level in males in response to any signal presented were noted. In the winter and spring, a reliable (P< 0.05) increase in the testosterone level was caused by the female MVGS odor. In the summer, a similar reaction only to conspecific female urine (P< 0.05) was noted. Moreover, in the summer and fall, males showed a reliable decrease in the cortisol level in response to the odor of female urine (P< 0.05). In the winter and spring, a similar result was caused by exposure to both odors. The progesterone level in males reliably (P< 0.05) increased upon exposure to both female urine and MVGS in all seasons of the year, except for the female MVGS in the summer. Therefore, the decreased cortisol level in combination with the simultaneously increased testosterone and progesterone levels allow the males of the species under study to achieve their maximum reproductive success, despite the high degree of their intraspecific aggression.

ХИМИЧЕСКИЕ СИГНАЛЫ КОНСПЕЦИФИКОВ И ИХ РОЛЬ В СЕЗОННЫХ ВЗАИМООТНОШЕНИЯХ У МОНГОЛЬСКОГО ХОМЯЧКА (ALLOCRICETULUS CURTATUS) (CRICETINAE, RODENTIA)

The hormonal response of males of the Allocricetulus curtatus hamster to the natural excreta (urine and midventral gland secretion [MVGS]) of conspecific females during several seasons of the year was studied when the animals were kept in the conditions of natural light and temperature. In the autumn, no significant changes in the testosterone level in the blood of males for any of the signals presented were observed. In the winter and summer, there was a trend of increasing this indicator in response to the smells of urine and MVGS of females in their diestrus state. In the spring, presentation of the urine of conspecific females in their estrous state led to a significant increase in the levels of both testosterone and cortisol, and the level of cortisol did not increase in response to exposure of the smells of females in their diestrus state in any season of the year. The level of progesterone significantly increased only when MVGS was presented in the spring and summer periods, and the absolute values of this indicator were significantly higher in the spring than in the summer. Differences in the responses to chemocommunication signals in two closely related Eversmann species (the Eversmann and Mongolian hamsters) are discussed in connection with intraspecific social relation peculiarities.

Immunocompetence and reproductive characteristics of Campbell’s dwarf hamster males selected for low and high humoral immune response on sheep red blood cells (SRBC): Testing the immunocompetence handicap hypothesis

Characteristics of innate (nonspecific) and acquired T-cell immunity, resting metabolic rate, hormonal and reproductive status, morphological traits of maturation and aggressive behavior were studied in two sample groups of Campbell’s dwarf hamster males (Phodopus campbelli Thomas, 1905) selected in three generations for high and low humoral immune response to sheep red blood cells (SRBC). The groups of males with low and high immune responses (LIR and HIR, respectively) to SRBC did not differ statistically in the intensity of delayed-type hypersensitivity cutaneous response to phytohemagglutinin (T-cell immunity test), the activity of the peroxidase-endogenous hydrogen peroxide system of neutrophils (characteristic of the innate immunity state), the white blood cell counts, the resting metabolic rate, body weight, anogenital distance at the age two months, testosterone level in the blood before immunization and at the peak of secondary immune response to SRBC, or the blood cortisol level in response to social conflict (encountering). LIR males had a significantly higher background blood cortisol level and were less aggressive (reaction to the stranger male). The midventral sebaceous gland was less developed in them at the age of two months. We observed no differences in the time of first litter birth after uniting LIR and HIR males in pairs with intact females; however, females in pairs with LIR males had smaller numbers of pups in the litter. The results of comparison do not favor the immunocompetence handicap hypothesis, which assumes the existence of a trade-off between the immunocompetence and reproductive effort.

Seasonal peculiarities of female hormonal response of females to conspecific chemical signals of the male in two species of the genus Phodopus

Changes in diestrous female blood plasma progesterone, estradiol, and cortisol in response to odors of urine and midventral gland secretion (MVGS) of conspecific males during different seasons have been studied in the desert hamster (Phodopus roborowskii and Djungarian hamster (Phodopus sungorus). In desert hamster females, a statistically significant (p < or = 0.05) increase in the plasma hormonal level was observed: for progesterone in response to conspecific male MGVS in all seasons except winter, and to conspecific male urine in spring and summer; for cortisol in response to male MVGS and urine in all seasons except spring; and for estradiol in response to male MGVS in autumn. Djungarian hamster females demonstrated a statistically significant increase in the plasma progesterone level in response to conspecific male MVGS and urine in winter and summer, and no response to the estradiol and cortisol level for both odors in all seasons.

On noninvasive assessment of the reproductive status of male Campbell’s dwarf hamsters (Phodopus campbelli) using digital images

The possibility of estimating the reproductive status of males using computer analysis of the contours of testes and midventral gland (MVG) in digital images was tested in Campbell’s dwarf hamsters (Phodopus campbelli). Relationships between the anogenital distance (AGD) and the diameters of testes and MVG were analyzed. The Pearson coefficient of correlation between the actual size of testes and that estimated from their visible contours proved to depend on the amount of white fat and varied from 0.9 in low-fat to 0.67 in high-fat hamsters. A strong correlation was revealed between the AGD and the diameter of testes in digital images. Both these parameters proved to be significantly greater in the reproductive period than in the non-reproductive (winter) period, while the diameter of MVG remained unchanged. These results agree with data on the winter ecology of Campbell dwarf hamsters and confirm that the above method can be used for assessing seasonal changes in the reproductive status of males.

Phylogeny and character evolution in Grania (Annelida, Clitellata)

De Wit, P., Rota, E. & Erseus, C. (2011) Phylogeny and character evolution in Grania (Annelida, Clitellata). —Zoologica Scripta, 40, 509–519. In this study, DNA sequences from six loci of twenty species are combined with a 54-character morphological matrix coded for all 72 described species of the marine clitellate genus Grania (Enchytraeidae) in the first ever attempt to illuminate the phylogeny of the group. The data are found to be inadequate for resolving the phylogeny of the entire genus, but a well-supported, fully resolved phylogeny of the subset of twenty species for which DNA data are available is found through both Bayesian inference and maximum parsimony. Using well-supported nodes from the Bayesian analysis, we investigate the morphological character evolution using parsimony ancestral state reconstruction. We find that most morphological characters used in standard species descriptions are homoplasious. Morphological characters that are found to be homological within clades (although not globally) include chaetal characters, midventral glands, penial stylets, coloration and possession of a head organ. Surprisingly, the head organ is strongly suggested as having evolved at least twice within the genus, but an alternative hypothesis is that this structure is an ancestral feature of the genus that has been secondarily lost, or simply has not been optically detected, in some lineages. Also, the geographical distributions of the Grania species used in the DNA analysis tend to follow the phylogeny, indicating limited dispersal capabilities.

Individual Recognition and Odor in Rat-Like Hamsters: Behavioral Responses and Chemical Properties

Individual recognition has been studied across a number of taxa and modalities; however, few attempts have been made to combine chemical and biological approaches and arrive at a more complete understanding of the use of secretions as signals. We combined behavioral habituation experiments with gas chromatography-mass spectrometry of glandular secretions from the left and right flank gland and midventral gland of the rat-like hamster, Tscheskia triton. We found that females became habituated to one scent and then could discriminate individuals via another scent source from the same individual only when familiar with the scent donor. However, this prior social interaction was not required for females to discriminate different individuals in single-stimulus habituation-dishabituation tests. Chemical analyses revealed a similarity in volatile compounds between the left and right flank gland and midventral gland scents. It appears that individually distinctive cues are integratively coded by a combination of both flank gland and midventral gland secretions, instead of a single scent, albeit animals show different preferences to the novel scent. Our results suggest that odors from the flank and midventral glands may provide information related to individuality and aid individual recognition in this species and confirm that prior interaction between individuals is a prerequisite for rat-like hamsters to form multi-odor memory of a particular conspecific.

Comparison of the activity of some phosphatases in the midventral gland and nonspecific sebaceous glands of the neck in the Campbell hamster (Phodopus campbelli)

Many skin glands of animals are a source of various olfactory signals. On some skin areas, these glands increase in size and fuse to form large sebaceous acini separated by connective-tissue septa. An example of such glands is the specific midventral gland, which is characteristic of many rodent species. In the neck area, hair sebaceous glands increase in size but never fuse into acini, even at elevated testosterone concentrations in blood. This type of glands is regarded as nonspecific. The role of these glands in life of animals remains obscure. The phenomenon of marking with specific skin glands has long been drawing attention of researchers [1]. It is known that the functional activity of a gland depends on the specific metabolic situation at a given stage of ontogeny [2, 3]. It was established that the parameters of various skin glands in the same animal correlate both with one another and with the parameters of sex glands [4]. However, the relationship between marking behavior and the functional state of glands involved in marking remains to be elucidated. Scent marks left by different animals are important elements maintaining the social structure of populations. In nature, these marks serve for both passive territorial defense and for creating an “informational field” optimizing intrapopulation processes [5]. Comparative histochemical studies have been long used for analyzing the structural‐chemical organization of functionally analogous organs [6]. The diversity of specific differentiation variants is based on respective metabolic modifications, which ultimately determines the functional state of skin glands whose parameters undergo age-related, seasonal, and other changes. Data on the correlation between enzymatic activity in different types of glands and their marking activity in rodent ontogeny are scanty. The goal of this study was to demonstrate the enzymatic specificity of sebaceous glands of the neck and to determine the correlation between this specificity and the histochemical characteristics of the midventral gland at certain stages of

Olfactory Responses of Neotropical Short-Tailed Singing Mice, Scotinomys teguina, to Odors of the Mid-Ventral Sebaceous Gland: Discrimination of Conspecifics, Gender, and Female Reproductive Condition

We examined the olfactory communication of the Neotropical short-tailed singing mouse, Scotinomys teguina, by investigating whether S. teguina responded to odors produced by the mid-ventral sebaceous gland of conspecifics. Females spent significantly more time investigating male odor than an odorless stimulus or a female odor. Males spent significantly more time investigating female odor than an odorless stimulus, but not that of a male odor. This latter result does not seem to be explained by differences in age or sexual experience of test subjects, but may be influenced by reproductive condition of the female odor donor. Male S. teguina spent significantly more time (1) investigating and (2) in total proximity to odors of estrous than non-estrous females. Males spent more time (1) investigating and (2) in total proximity to odors of males than non-estrous females. Finally, given the choice between odor of males vs proestrous females, males showed no preference. Thus, the mid-ventral gland in S. teguina seems to convey information about conspecifics, sex, and female reproductive condition. Male odor, compared with proestrous female odor, is equally interesting to males, suggesting that the gland also plays an important role in male-male communication. Sexual dimorphism in the size of the gland and in the amount of secretion produced by the gland may be related to either male-male competition or female choice.

Scent, social status, and reproductive condition in rat-like hamsters ( Cricetulus triton)

This study investigated the interrelations among scent glands, social status, and reproductive conditions in male rat-like hamsters ( Cricetulus triton), along with differential attraction of estrous females to conspecific males with different social status and reproductive condition. First, there were positive correlations between testes weights and flank glands and midventral glands. Second, castrated males were dominated by both intact males and castrated males treated with testosterone. Third, estrous females were less attracted to the scents from flank glands and midventral glands of castrated males. Moreover, dominant males had heavier testes and higher levels of circulating testosterone, and estrous females were more attracted to dominant males' scents. Our results indicated that estrous females were able to discriminate between the odors of two strange males with differences in reproductive conditions or social status.

Development of Species Preferences in Two Hamsters, Phodopus campbelli and Phodopus sungorus: Effects of Cross‐Fostering

Experiments were conducted to investigate species‐specific preferences in two closely related species of hamsters, Phodopus campbelli and Phodopus sungorus. Male hamsters that were raised with conspecifics spent more time investigating an anaesthetized conspecific male than a heterospecific male, and also spent more time investigating odours of conspecifics than those of heterospecifics (midventral gland, urine, and saccular secretion). Cross‐fostered P. sungorus males reversed their normal preferences, spending more time investigating stimuli (anaesthetized males and all three odours) of the foster species. Cross‐fostered P. campbelli males also investigated an anaesthetized male of the foster species more than a male of their own species, but did not show a preference for odours alone. Social experience during the 15 d immediately following weaning also influenced these preferences. If exposures during and after nesting were to heterospecifics the preference for heterospecifics was strengthened; if either period of experience was with a conspecific, this eliminated the preference for heterospecifics in P. sungorus but did not influence the lack of a preference in P. campbelli. Thus, early experience during both the nestling stage and the 15 d after weaning influenced responses to species‐typical cues in both species, but it had a more pronounced effect in P. sungorus.

Odors Providing Sexual Information in Djungarian Hamsters: Evidence for an Across-Odor Code

Experiments were conducted to determine the repertoire of odors that are involved in sexual recognition and communication about reproductive state in Djungarian hamsters (Phodopus campbelli). By examining the preferences of males for odors of females over those of males, it was found that some odors support preferences across female reproductive states, other odors induce preferences only during estrus, and yet other odors do not elicit sexual preferences. Similarly, female preferences for male odors was restricted to just some scents. Males were also tested for their preferences for female odors from different reproductive states (diestrous, day before parturition, post-partum estrus). Four different odors were found to vary in attractiveness with these reproductive states, and there were three different patterns of change: (1) mouth and urine odors were attractive just during post-partum estrous; (2) midventral gland was most attractive the day before parturition; (3) vaginal secretions showed a graded pattern of attractiveness, peaking at post-partum estrus. These results show that different odors provide some redundant and some different information, and they suggest that an across-odor code could be used to provide very precise information about a female's reproductive state.

Individual Odors in Djungarian Hamsters (Phodopus campbelli)

AbstractThe sources of scent in Djungarian hamsters (Phodopus campbelli) that may be individually discriminated were investigated using an habituation paradigm. Male Djungarian hamsters were exposed to five presentations of a particular scent from one individual, and then to the same scent from a novel individual. Increased investigation of the scent from the novel individual indicated discrimination of scents from different individuals. Male hamsters distinguished individual differences in scents of other males from the midventral gland, urine, feces, mouth, and the corner of the mouth, which includes the sacculi; they did not discriminate among odors of different individuals when the scents were from the genital region, hindfeet, fur from behind ears or fur from the back. The results indicate that Djungarian hamsters have a repertoire of individually distinctive scents that are located in specific places on the body; these scents are not actively distributed to, nor passively picked up on, other parts of the body. The fact that scents from some areas do not contain individually distinctive information suggests that some sources may be specialized for producing individually distinctive scents.

The Role of Midventral Gland Secretion in Individual Discrimination by Djungarian Hamster (Phodopus camphelli Thomas, 1905) Females

AbstractTwo experiments were conducted to investigate discrimination of individual male Djungarian hamsters by conspecific females. In the first experiment, it was shown that females reacted differently to two anaesthetized males ‐ their mate and an unfamiliar male ‐ by showing more aggressive behaviour toward the unfamiliar male. In the second experiment, females were more aggressive toward an unfamiliar, awake male than a familiar partner. Furthermore, aggression toward the mate was increased by scenting him with midventral gland secretion from an unfamiliar male. Aggression toward an unfamiliar male was reduced by scenting him with the mate's ventral gland secretion. Thus, the midventral gland scent is an important signal for individual recognition in Djungarian hamsters.

Effects of hormones and gonadal status on the midventral gland of the grasshopper mouse Onychomys leucogaster.

A midventrally located fusiform sebaceous gland is found in the northern grasshopper mouse Onychomys leucogaster. Microscopically, the gland consists of numerous multilobular units. Copious secretory material collects in the central duct of each unit and is extruded to the outside. The gland is larger in the male than in the female. Castration causes an involution of the gland in both sexes. Testosterone propionate (1.0 mg/0.1 cc olive oil, subcutaneously every other day for 4 weeks) restores the gland to full activity in castrates of both sexes. Estradiol benzoate (0.1 mg/0.1 cc olive oil, subcutaneously every other day for 4 weeks) has no effect on the midventral gland of ovariectomized females. A long photoperiod (18 L/6 D) leads to the development of testes, ovaries, and uteri that are significantly heavier than those of animals from a short photoperiod (6 L/18 D) regime. Midventral glands in animals of both sexes from the long photoperiod are larger and more active than glands from animals from the short photoperiod. The secretions of the midventral gland of Onychomys are probably used for communications such as territorial marking, advertisement of gonadal status, or pup identification.

Gruczoły brzuszne u Tatera indica i Rattus meltada

Kumari S. & Prakash I., 1983: The mid-ventral gland of the Indian gerbil, Tatera indica and soft-furred field rat, Rattus meltada. Acta theriol., 28, 28: 425—438 [With 3 Tables, 2 Figs. & Plates XIV—XV] The ventral scent marking gland occurs in about 91 and 72 per cent male Tatera indica and Rattus meltada respectively. It is absent in the females of the latter species but is present in about 5.8 per cent female T. indica residing in urban areas and 10.3 per cent female residing in desert grasslands. The gland size is positively and significantly correlated with body weight. The growth of the gland is a continuous process throughout the life of the rodents. No relationship has been found between the gland size and the home range of the rodents. The sebaceous alveoli in the gland of both the species are of typical holocrine type and the epidermal stratified epithelium in T. indica is smooth whereas in R. m. pallidior it is papillaeform. [Coordinating & Monitoring Centre for Rodent Research and Training, Central Arid Zone Research Institute, Jodhpur-342 003, India]

Characterization of a sex pheromone in the jird (Meriones tristrami)

The Israeli jird (Meriones tristrami) is a semidesert crecitid rodent found throughout the Mid-East. Jirds use a midventral sebaceous gland to scent-mark objects, the ground, and conspecifics. Volatile compounds from the male gland extract were found to containn-aliphatic acetates by thin-layer chromatography, gas chromatography, and mass spectroscopy. In a digital olfactometer, female jirds demonstrated preference for male glandular extract and many of then-aliphatic acetates. Other biologically important odors were also presented to the female jirds. Behavioral observations combined with olfactory bioassays implicate the involvement of the ventral sebaceous gland in jird sexual behavior.