Biology ETDs

Publication Date

6-29-1972

Abstract

The reproductive cycles of Myotis volans, Lasionycteris noctivagans, and Lasiurus cinereus were investigated by examining representative sections of testes and epididymides from 254 males and serially sectioned reproductive tracts of 99 females. Specimens were collected primarily in New Mexico from late March through early October. Spermatogenesis begins in August in M. volans, October in L. noctivagans, and sometime after late September in L. cinereus. Apparently gonadotrophic secretion continues in M. volans until at least the onset of hibernation as numerous mitotic figures, small spermatogonia, and/or a few primary spermatocytes appeared in some males from September and October. During the winter, spermatogenesis is greatly depressed in M. volans, and L. noctivagans. In L. cinereus the depression is not as severe and is of shorter duration. Most spermatogenesis followed by spermiation occurred from May through August in M. volans, May through October in L. noctivagans, and from before May through at least October and possibly early November in L. cinereus. Peak spermiogenesis occurred during late July in M. volans, late August in L. noctivagans, and approximately early September in L. cinereus. The length of time required for most spermatogenesis to occur in each species directly reflects individual variation in reproductive condition and the time required for production of primary spermatocytes in an individual. Apparently, a relatively short time period is required for primary spermatocyte production in M. volans and L. noctivagans, and this appears to be an adaptation for hibernation. A longer time period is required in L. cinereus, and may reflect the distribution of these bats in warm climates or lower latitudes from late fall through early spring. Copulation started by 28 August in M. volans, late September in L. noctivagans, and 8 September in L. cinereus. Copulation may continue during the winter and spring in these species because sperm are stored in the cauda epididymides throughout most of the year. In M. volans from New Mexico, ovulation occurs from March through May, parturition from May through early August, and lactation from May through late August. Local environmental conditions may influence time of parturition. Vesicular follicles of hibernation develop in late August and September. In L. noctivagans ovulation occurs during April and May with a peak during late April and early May. Approximately 10 days elapse between ovulation and implantation. Gestation approximates 50 to 60 days. Thirty-six spring females had an average of 1.84 preovulatory eggs or embryos per female. Graafian follicles appear to be adapted for hibernation, but this must be confirmed in winter specimens. Most female L. cinereus are pregnant when they enter New Mexico in April. Lactation approximates 30 days. Mature vesicular follicles may not be adapted for hibernation, but additional data are needed. Most male and female L. cinereus and L. noctivagans apparently mature sexually during their first summer. Some female M. volans may mature during their first summer, but most if not all males mature as yearlings.

Language

English

Document Type

Dissertation

Degree Name

Biology

Level of Degree

Doctoral

Department Name

UNM Biology Department

First Committee Member (Chair)

James Smith Findley

Second Committee Member

Clifford Smeed Crawford

Third Committee Member

Marvin LeRoy Riedesel

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