William A. Wimsatt

Some aspects of the comparative anatomy of the mammalian placenta

A s o u R knowledge of reproductive processes in animals has advanced the connotation of the word “placenta” has changed. In its original meaning the word denoted a functional union between fetal membranes and the uterus, and in this anatomically restricted sense a placenta was long thought to be peculiar to mammals. When homologous organs were later recognized in certain viviparous species of lower vertebrates it was only natural that the term be extended to these as well. Today, however, zoologists use the term in respect to the union between any fetal structure and any part of a parental organism (male or female) which mediates physiologic exchange; clearly the original anatomical implications of the term have become generalized, and its physiologic connotations predominate. We shall consider here, however, only the placenta of higher mammals (Eutheria), in which the original anatomical implications of the term are still apropos. Because of space limitations the treatment cannot be comprehensive. Rather, it will be selective, the general aim being to illustrate the nature of some significant variables in placental organization which provide bases for differences in functional pattern between

Transient Behavior, Nocturnal Activity Patterns, and Feeding Efficiency of Vampire Bats (Desmodus Rotundus) under Natural Conditions

During 5 netting nights, 99 vampire bats (Desmodus rotundus) (37 males, 57 females, five sex unrecorded) were taken in a mist net stretched before the entrance of a permanent cave roost in Tabasco. Each was banded; weight, sex, time of capture, and direction of passage (in or out of the roost) were noted; and the bat was then released. Because 33 individuals were recaptured one or more times, a total of 139 bats was handled. The repopulation of another roost during biweekly intervals following two successive removals of almost all bats present is recorded also. Analysis of these data suggest the following conclusions: 1) within a given population there may be multiple diurnal roosts among which individuals shift on a more or less daily and perhaps opportunistic basis (it has generally been assumed that vampires use a single home roost to which the same individuals return each day); 2) maximum foraging activity is restricted to the earlier hours of the evening; 3) vampires forage only after dark, the mean foraging time being estimated to be about 2 hours; 4) vampires seem not to utilize temporary nocturnal roosts in the usually Accepted sense, but return directly to a diurnal roost after foraging; 5) most individuals probably forage only once nightly; 6) heavy precipitation tends to suppress foraging activity; 7) differences in foraging pattern between the sexes were not apparent; 8) the amount of blood consumed may depend upon the length of the foraging period; 9) wild vampires probably consume not less than 20 per cent (of fasting body weight) more blood per diem than vampires in captivity, but variation from day to day apparently is great.

Renal function and its relation to the ecology of the vampire bat, Desmodus rotundus

Abstract 1. 1. Blood consumption in 7-hr experimental periods (blood available first 2 hr) averaged 37·4 per cent/body wt. 2. 2. Urine averaged 40·5 per cent/blood consumed, with 62 per cent voided in the first hour. 3. 3. At peak flow (4·0 ml/kg per min) osmotic concentration was 475 mOsm; 6 1 2 hr later the mean high was 4656 mOsm. 4. 4. Ratio urea/mOsm urine reached 0·73, or 68 per cent of total activity. 5. 5. Na and Cl diminished with concentration (90 per cent of activity in dilute urine, 9·5 per cent in concentrated urine), but Na/Cl ratio increased (240 mM Na/60 mM Cl at mean concentration of 4656 mOsm). 6. 6. Potassium (max. 42 mM/l) was uncorrelated with Na, Cl or osmotic concentration. 7. 7. Insensible losses (during 2 hr after feeding at ambient temperature 23·5–25°C) were 13·7 per cent (r.h. 40 per cent) and 8·5 per cent (r.h. 77 per cent) respectively.

Observations on the Feeding Capacities and Excretory Functions Of Captive Vampire Bats

Observations are presented on the feeding capacities of captive vampire bats ( Desmodus rotundus ) and on their excretory functions as these relate to the volume of blood ingested and the metabolic efficiency of blood utilization. The average daily intake of blood by individual members of two large groups of bats in which consumption records were kept for a full year was 15.3 ml and 15.6 ml; the range of variation was between 11.6 and 21.0 ml. The daily consumption average of isolated individuals tended to be somewhat higher. One non-pregnant female maintained in isolation for 17 days consumed blood in excess of her body weight (28 gm ) on 13 of them, and on two days the amounts ingested were as high as 47 and 52 ml respectively. Urine excretion is copious, and generally amounts to slightly less than 50 per cent by volume of the blood ingested over a 24 hour period. Urine flow begins promptly after feeding, and evidence is presented that the tubular stomach is a major site of fluid absorption. Based upon observation of a single bat over a 4-day period it is estimated that the animal ingested (on a dry weight basis) an average of 0.12 gm solids/gm body weight per day, and “utilized” metabolically about 73% of the solids ingested. Justification is presented for our estimate (probably conservative), that under natural conditions a single vampire may ingest nearly two gallons of blood a year, and that the total blood lost by the animal prey of vampires in countries (such as Mexico) where the bats are common may amount to many hundreds of thousands of gallons annually.

Studies on prolonged spermatozoa survival in chiroptera—I. The role of uterine free fructose in the spermatozoa storage phenomenon

Abstract 1. 1. The fructose content of the reproductive tracts of Myotis lucifugus and M. uelifer was recorded at intervals throughout the annual reproductive cycle. 2. 2. The data indicate that seminal fluid (particularly the ampullary glands) contributes to the uterine fructose content and that the uterus is also fructogenic. 3. 3. Preliminary experiments tested the role of steroids and of stress-related hormones on uterine fructose. 4. 4. Fructose was not present in the epididymides. 5. 5. While fructose of seminal and uterine origin probably plays a role in prolonged sperm survival, the possibility that other metabolizable substrates are present and of use for spermatozoa retention in the female reproductive tract should be investigated.

Care and Maintenance of the Common Vampire in Captivity

Conditions and procedures which have been utilized in our laboratory in the successful maintenance of the common vampire bat, Desmodus rotundus , in captivity over a period of several years are described, with the expectation that they may prove useful to other investigators. Also described is a cage design which helps minimize some of the special problems associated with the handling of vampires and making provision for their sanitation; the cage can also be used to advantage with other species of bats.

Responses of Captive Common Vampires to Cold and Warm Environments

When exposed to a cold environment (3°–5°C) common vampires quickly respond by increasing their food consumption and muscular activity. Both functions return promptly to normal levels when the ambient temperature is again raised. During relatively brief periods of cold exposure the animals remain normally alert and responsive, showing no evidence of induced torpor. They die, however, from within a few hours to three days when they are continuously exposed to temperatures of 3°–5°C. The great individual variation in the tolerance of cold observed among the experimental animals may indicate a capacity for physiological acclimation in captive specimens; nevertheless, the vampires inability to withstand prolonged periods of cold exposure undoubtedly places a physiological limitation on its capacity to extend its range into more temperate latitudes. Collectively the observations suggest that the vampire bat is homeothermic. It raises its heat production by increasing metabolism and muscular activity when exposed to cold. Incidental observations upon vampires in warm environments indicate that the upper critical environmental temperature lies in the range of 27°–30°C.