Oviductal Eggs Research Articles

Reproduction in the Yuman Fringe-Toed Lizard,Uma rufopunctata(Squamata: Phrynosomatidae)

Information on the reproductive cycle of Uma rufopunctata is presented from a histological examination of specimens collected during May from Sonora, Mexico. The smallest reproductively active male (spermiogenesis in progress) was 81 mm in snout–vent length. Mean size of clutch for 20 females was 2.4 ± 1.0 SD, range = 1–5. The smallest reproductively active female was 63 mm in snout–vent length. Presence of oviductal eggs and concomitant deposition of yolk in one female during May indicated that U. rufopunctata may produce >1 clutch of eggs in the same reproductive season.Se presenta información del ciclo reproductivo de Uma rufopuncta medio de una examinación histológica de ejemplares colectados durante el mes de mayo en Sonora, México. El macho más pequeño reproductivamente activo (con espermogénesis en progreso) midió 81 mm de longitud de hocico a cloaca. El tamaño promedio de 20 puestas de huevos fue de 2.4 ± 1.0 DE, rango = 1 a 5. La hembra más pequeña reproductivamente activa midió 63 mm de longitud de hocico a cloaca. La presencia de huevos en el oviducto y la deposición de yema concomitante de una hembra durante de mayo indicaron que U. rufopunctata puede producir más de una puesta de huevos en la misma temporada reproductiva.

Reproduction of the Yellow-backed Spiny Lizard, Sceloporus uniformis (Squamata: Phrynosomatidae) from California

The reproductive cycle of Sceloporus uniformis was studied by a histological examination of gonads collected from five California counties: Inyo, Kern, Los Angeles, Riverside and San Bernardino. Males followed a testicular cycle in which sperm production (spermiogenesis) started in March and was completed by August. The smallesr reproductively active male measured 79 mm SVL. Females were reproductively active from March into July. Mean clutch size (n 5 21) was 6.48 6 2.2 SD, range 5 3–10. The smallest reproductively active female (enlarged follicles .5 mm) measured 78 mm SVL. Histological evidence is presented (oviductal eggs and concomitant yolk deposition) that multiple clutches are produced by some females of S. uniformis. The yellow-backed spiny lizard, Sceloporus uniformis Phelan and Brattstrom, 1955, occurs primarily in the Mojave and Great Basin Deserts of California, Nevada, Utah, and northwestern Arizona, as well as the Central Valley of California from near sea level to around 1,520 m (Conrad 2009). Schulte et al. (2006) elevated the subspecies Sceloporus magister uniformis to Sceloporus uniformis. Previous information on its reproductive cycle are one or more clutches of 4–19 eggs deposited from May to August (Conrad 2009). In Nye County, Nevada, a mean of 7.0 eggs was produced (Tanner and Krogh 1973). In southern Utah (Washington County), reproduction occurs from May to July with two clutches averaging 6.2, range 2–9 eggs (Tinkle 1976). Five adult S. uniformis females from the Providence Mountains, San Bernardino County, California collected between May 22 and June 11 contained enlarged ovarian follicles (Johnson et al. 1949). The purpose of this paper is to provide additional information on the reproductive cycle of S. uniformis from a histological examination of gonads. Categorization of the reproductive cycle including period of sperm production, timing of yolk deposition and number and sizes of clutches produced provides important information in formulating conservation policies for lizard populations (Gibbons 1994). Due to the difficulty in obtaining collecting permits for large collections of monthly lizard samples, utiliization of museum collections for obtaining reproductive data has become increasingly important. A sample of 239 S. uniformis consisting of 105 adult males (mean SVL 5 100.8 mm 6 9.6 SD, range: 78–124 mm), 51 adult females (mean SVL 5 91.5 mm 6 7.6 SD, range: 77– 108 mm), 75 juveniles (mean SVL 5 56.3 mm 6 10.6 SD, range: 37–56 mm) and eight neonates (mean SVL 5 32.1 mm 6 4.0 SD, range: 24–34 mm) collected 1921 to 1980 was examined from the herpetology collection of the Natural History Museum of Los Angeles County (LACM), Los Angeles, California, USA (appendix). The left gonad was removed and embedded in paraffin. Histological sections were cut at 5mm and stained by hematoxylin followed by eosin counterstain (Presnell and Schreibman 1997). Enlarged follicles . 5 mm length and oviductal eggs were counted. Histology slides were deposited in LACM. The snout-vent length (SVL) of each specimen was measured from the tip of the snout to the posterior margin of the vent. An unpaired Bull. Southern California Acad. Sci. 111(1), 2012, pp. 25–28 E Southern California Academy of Sciences, 2012

Reproductive strategy of male and female eastern spiny lizards Sceloporus spinosus (Squamata: Phrynosomatidae) from a region of the Chihuahuan Desert, México

We examined the reproductive strategy of male (n = 84) and female (n = 62) S. spinosus from a single population in San Luis Potosi, Mexico. The male reproductive cycle peaked in March and April and declined from May to September, and was not correlated with fat body mass, but was positively correlated with liver mass. The female reproductive cycle peaked in April and May and declined from June through November, and was not correlated with fat body mass, but was correlated with liver mass. Mean clutch size based on oviductal eggs was 17.5 ± 1.9 (n = 12), and was not correlated with female snout-vent length. Our results for S. spinosus are generally similar to those of other populations of the S. spinosus species group. However, there are differences in some traits (e.g., timing of the initiation of the female reproductive cycle; clutch size), suggesting that the S. spinosus group could serve as another model group within Sceloporus to explore ecological and evolutionary causes of among population life history variation.

The Annual Ovarian Cycle of the Reeves' Pond Turtle Chinemys reevesii (Reptilia: Geoemydidae) Based on Seasonal Variations in the Serum Vitellogenin Level and Follicular Growth

To demonstrate the annual ovarian cycle of a multiclutched turtle Chinemys reevesii, we quantified vitellogenin (VTG, a yolk-precursor protein) in the serum collected monthly from turtles kept in an outdoor enclosure. We also sacrificed wild adult females (one or two individuals per month) captured from a river site in Kyoto, Japan, and observed oviductal eggs and follicles assigned to five size classes: C1 to C5, in ascending order. The seasonal variation in the serum VTG level showed a sharp peak in late spring and a broad peak during autumn, indicating that vitellogenesis accelerated rapidly in spring, decreased in summer, increased slowly but steadily in autumn, and ceased in winter. From May to July, ovulations occurred in succession preceded by the C4-to-C5 growth of follicles, but without substantial growth of C1–C3 follicles. The vernal peak of vitellogenesis would therefore contribute largely to the sequential growth of the follicles prepared for the second and third clutches of the breeding season. In August, when the successive ovulations had been completed, no remarkable growth of C1–C3 follicles was observed anymore, reflecting the ovarian quiescence. Newly-formed C1 follicles appeared in September when C2 and C3 follicles markedly increased in number but C4 and C5 follicles were still absent. In October and November, C4 and C5 follicles were observed again, suggesting that the follicles for the first clutch of the next breeding season reached preovulatory size before hibernation. The production and remarkable growth of follicles occurring from September to November would account for the broad peak of vitellogenesis in autumn. Thus the observed seasonal variations in the serum VTG level and follicular growth were concordant with each other.

Notes on Reproduction of the Gold Dust Day Gecko, Phelsuma laticauda (Gekkonidae) from Hawaii

We studied the reproductive cycle of the introduced gecko, Phelsuma laticauda from a histological analysis of museum specimens from Hawaii. All adult males >40 mm SVL exhibited spermiogenesis in samples collected in January to April and in August. Females invariably produced clutches that contained two eggs. The presence of oviductal eggs and concomitant yolk deposition in some of the same females as well as the presence in the population of juveniles during both summer and winter months, indicate P. laticauda produces multiple clutches in Hawaii. The smallest reproductively active female (early yolk deposition) measured 46 mm SVL. Considering the potential negative effects on endemic Pacific island lizards, colonization by P. laticauda should be discouraged.

Notes on Reproduction of the Gold Dust Day Gecko, Phelsuma laticauda (Gekkonidae) from Hawaii

Abstract: We studied the reproductive cycle of the introduced gecko, Phelsuma laticauda from a histological analysis of museum specimens from Hawaii. All adult males >40 mm SVL exhibited spermiogenesis in samples collected in January to April and in August. Females invariably produced clutches that contained two eggs. The presence of oviductal eggs and concomitant yolk deposition in some of the same females as well as the presence in the population of juveniles during both summer and winter months, indicate P. laticauda produces multiple clutches in Hawaii. The smallest reproductively active female (early yolk deposition) measured 46 mm SVL. Considering the potential negative effects on endemic Pacific island lizards, colonization by P. laticauda should be discouraged.

The Annual Ovarian Cycle of the Reeves’ Pond Turtle Chinemys reevesii (Reptilia: Geoemydidae) Based on Seasonal Variations in the Serum Vitellogenin Level and Follicular Growth

To demonstrate the annual ovarian cycle of a multiclutched turtle Chinemys reevesii, we quantified vitellogenin (VTG, a yolk-precursor protein) in the serum collected monthly from turtles kept in an outdoor enclosure. We also sacrificed wild adult females (one or two individuals per month) captured from a river site in Kyoto, Japan, and observed oviductal eggs and follicles assigned to five size classes: C1 to C5, in ascending order. The seasonal variation in the serum VTG level showed a sharp peak in late spring and a broad peak during autumn, indicating that vitellogenesis accelerated rapidly in spring, decreased in summer, increased slowly but steadily in autumn, and ceased in winter. From May to July, ovulations occurred in succession preceded by the C4-to-C5 growth of follicles, but without substantial growth of C1–C3 follicles. The vernal peak of vitellogenesis would therefore contribute largely to the sequential growth of the follicles prepared for the second and third clutches of the breeding season. In August, when the successive ovulations had been completed, no remarkable growth of C1–C3 follicles was observed anymore, reflecting the ovarian quiescence. Newly-formed C1 follicles appeared in September when C2 and C3 follicles markedly increased in number but C4 and C5 follicles were still absent. In October and November, C4 and C5 follicles were observed again, suggesting that the follicles for the first clutch of the next breeding season reached preovulatory size before hibernation. The production and remarkable growth of follicles occurring from September to November would account for the broad peak of vitellogenesis in autumn. Thus the observed seasonal variations in the serum VTG level and follicular growth were concordant with each other.

Reproduction in the Baja California Collared Lizard, Crotaphytus vestigium (Squamata: Crotaphytidae)

Crotaphytus vestigium, a rock-dwelling species of the peninsular ranges of Baja California, occurs along the northern slope of the San Jacinto Mountains, Riverside County, California, south to the southern margin of the volcanic Magdalena Plain in Baja California Sur (McGuire 1996). Published information on the reproduction of C. vestigium consists of brief accounts by Lemm (2006), Ivanyi, (2009) and field observations by McGuire (1996), Grismer (2002) and Stebbins (2003). The purpose of this paper is to examine the reproductive biology of C. vestigium from a histological analysis of gonadal material from museum specimens, an often used method, see for example, Goldberg (1974). Information on the reproductive cycle such as timing of spermiogenesis, number of egg clutches produced and period of vitellogenesis may not only be helpful in determining phylogenetic affinities, but also provides essential life history data for implementing conservation management strategies of lizard species. We examined 61 C. vestigium consisting of 33 males (mean snout-vent length, SVL 5 96.5 mm 6 12.3 SD, range: 72–116 mm and 28 females (mean SVL 5 80.4 mm 6 8.6 SD, range: 54–93 mm) from Imperial, Riverside and San Diego Counties, California and Baja California and Baja California Sur, Mexico. Specimens were examined from the herpetology collections of the Natural History Museum of Los Angeles County (LACM), Museum of Vertebrate Zoology (MVZ), and San Diego Society of Natural History (SDSNH) (Appendix I). Lizards were collected 1934–1997. Histology slides were deposited at LACM, MVZ and SDSNH. The left testis was removed from males and the left ovary was removed from females for histological examination (Presnell and Schreibman 1997). Enlarged ovarian follicles (. 5 mm) and/or oviductal eggs were counted. Tissues were embedded in paraffin, sectioned at 5 mm and stained with hematoxylin followed by eosin counterstain. Ovary slides were examined for yolk deposition or corpora lutea. Testis slides were examined to ascertain the stage of the testicular cycle present. Mean SVL of male and female C. vestigium were compared using an unpaired t-test (Instat vers. 3.0b, Graphpad Software, San Diego, CA). The mean male SVL of C. vestigium significantly exceeded that of females (unpaired t test, t 5 5.82, df 5 59, P , 0.0001). Monthly stages in the testicular cycle of C. vestigium were shown in Table 1. Three stages were present: (1) Regression, the germinal epithelium was reduced to 1–3 cell layers in thickness and consists of spermatogonia and Sertoli cells; (2) Recrudescence, a proliferation of germ cells for the next period of sperm formation was underway. In early recrudescence, primary spermatocytes predominate, Bull. Southern California Acad. Sci. 109(3), 2010, pp. 153–156 E Southern California Academy of Sciences, 2010

Cyclical Reproduction in Females of the Cuban Lizard Anolis lucius (Polychrotidae)

Abstract We describe the gonadal and fat-body cycles and their relationship to environmental factors for Cuban female Anolis lucius (Polychrotidae). We obtained monthly samples of lizards from the karstic caves at Boca de Jaruco, Havana, Cuba. The lizards reached sexual maturity at 45.0 mm snout–vent length and at approximately 7 mo of age. Female A. lucius showed seasonal reproduction from March to August. The nonreproductive season occurred from September to February, as identified by the absence of active ovogenesis. Vitellogenic ovaries, and almost all females having one or two oviductal eggs, characterized the peak reproductive interval from May to August. In contrast, fat-body mass diminished from May to July and reached its highest values from September to January. The clutch size is one egg per oviposition, and oviposition events occurred from July to September. Increased photoperiod and environmental temperature induced ovarian activity.

Newly deposited maternal hormones can be detected in the yolks of oviductal eggs in the green anole lizard

Studies often examine egg yolks after oviposition with the goal of drawing conclusions about maternal allocation of gonadal steroid hormones and how it may affect offspring development. However, these hormones might originate from a few sources, including the ovary, blood plasma, or the embryo itself. The goal of this study was to investigate whether maternal steroids can enter oviductal eggs. In Experiment 1, gravid female green anole lizards were injected with 1 microCi 3H-T. Plasma, ovarian follicles (separated into yolking and non-yolking samples), and shelled oviductal eggs were collected at times ranging from 15 min to 24 hr after treatment. Main effects of tissue, time, and an interaction between them all existed on recovered 3H-hormone corrected for tissue mass. Of particular interest, there was a decrease in plasma with coincident increase in eggs. In Experiment 2, females were injected with doses ranging from 0.01 to 0.45 microCi of 3H-T per gram body weight. Across tissues, 3H-hormone levels corrected for mass were greater with increasing doses. Values also differed among tissues and an interaction was detected. Within each dose, plasma and non-yolking follicles generally had higher concentrations of 3H-hormone than did yolking follicles and oviductal eggs. However, at and after 6 hr, eggs had higher total radioactivity levels than both yolking and non-yolking follicles had (not corrected for mass). The results indicate that steroids can cross through relatively well-formed shells before oviposition, suggesting a way in which maternal hormones might influence developmental factors after yolk deposition.

Natural history of the lizard Enyalius perditus (Squamata: Leiosauridae) from an Atlantic forest remnant in southeastern Brazil

The natural history of the lizard Enyalius perditus was studied from August 2005 to July 2006, at Parque Estadual Nova Baden, in the municipality of Lambari, State of Minas Gerais, south-eastern Brazil. We found that E. perditus may be considered a semi-arboreal species, like other species in the genus, sleeping on vegetation (slim branches or large leaves) at night, possibly to minimize predation. Females with enlarged follicles or oviducal eggs were found from November to January and juveniles recruited at the end of the dry season and beginning of the rainy season, in October. The diet of this lizard is composed mainly of Lepidoptera larvae, Araneae and Formicidae. Females were larger than males, and juvenile coloration is similar to that of adult females.

Identification of the sperm motility-initiating substance in the newt, Cynops pyrrhogaster, and its possible relationship with the acrosome reaction during internal fertilization

Motility initiation is a key event during internal fertilization of female-stored sperm, although the underlying mechanisms remain unclear. In internally fertilizing urodeles, quiescent sperm initiate motility on the surface of the egg-jelly, a thick extracellular matrix that accumulates around the egg in oviduct. By immunizing mice with egg-jelly extracts, we successfully generated an alpha34 monoclonal antibody (mAb) which neutralized sperm motility-initiating activity in the egg-jelly of the newt, Cynops pyrrhogaster, in a dose-dependent manner. The alpha34 mAb recognized an unglycosylated 34 kDa protein in the outermost of the six layers that comprise egg-jelly. Under nonreducing conditions, immunoblotting with alpha34 mAb produced many bands in addition to the 34 kDa protein, suggesting that the 34 kDa protein associates not only with the jelly matrix itself, but also with additional substances present in the matrix. Our current results are compatible with the supposed features of sperm motility-initiating substance (SMIS), indicating that the 34 kDa protein itself, or a complex consisting of the 34 kDa protein and some other molecules, is the SMIS in C. pyrrhogaster. Immunofluorescence staining further indicated that SMIS was distributed in a dot-like pattern in the outermost jelly layer and was fully covered with acrosome reaction-inducing substance (ARIS). Immunocytochemical and scanning electron microscopic examinations of the outermost jelly layer strongly suggests that the 34 kDa protein localized in granules (2 microm) and that ARIS was distributed covering the granules and in the sheet-like structure above the granules. These data suggest that the initiation of sperm motility is mediated by the acrosome reaction.

Population Ecology and Reproduction of the Mexican Mud Turtle (Kinosternon integrum) in Tonatico, Estado de México

ABSTRACT. Ecological data directly from the field are important in understanding the life history strategies of kinosternid species in the tropics. Herein we summarize the basic population ecology and life history of Kinosternon integrum in the municipality of Tonatico (southeastern Estado de Mexico, Mexico). From October 2003 to November 2004, we marked a total of 204 turtles and recaptured 118 of them. Mean population size using the Jolly-Seber model was 197 (95% CI 128–416) individuals, with a sex ratio of 1:1.7, biased to females. Males were larger than females in carapace length and plastron length. The reproductive season starts in late June and finishes in late October. The smallest female with oviductal eggs was 122 mm in carapace length. Mean clutch size was 4 eggs (s = 1.77, range 1–8) and was significantly and positively related to body size. Mean egg length was 30.43 mm (s = 2.24, range 23.92–35.96), mean width was 16.35 mm (s = 1.01, range 12.99–18.30), and mean weight was 5.14 g (s = 0.60, r...

Reproduction and Sexual Dimorphism in the Whiptail Lizard Aspidoscelis gularis (Squamata: Teiidae) in Guadalcázar, San Luis Potosí, Mexico

Abstract We studied reproduction and sexual dimorphism of Aspidoscelis gularis from an arid environment in Guadalcazar, San Luis Potosi, Mexico. Males reached sexual maturity at a larger snout-vent length (55. 2 mm) than females (52. 4 mm). Males and females were similar in size, but males had larger heads and longer hindlimbs than females. Reproductive activity of both sexes was synchronous, similar to other species of the genus Aspidoscelis. Testicular recrudescence occurred February–March and maximum activity was March–October, and regression was in November. Vitellogenesis occurred February–September, with ovulation and fertilization occurring in June. Mean size of clutch of oviductal eggs was 3.0 ± 0.32. Size of clutch was not related to snout-vent length. Proximal factors influenced timing and intensity of reproduction in A. gularis.

SEVERE COSTS OF REPRODUCTION PERSIST INANOLISLIZARDS DESPITE THE EVOLUTION OF A SINGLE-EGG CLUTCH

A central tenet of life-history theory is that investment in reproduction compromises survival. We tested for costs of reproduction in wild brown anoles (Anolis sagrei) by eliminating reproductive investment via surgical ovariectomy and/or removal of oviductal eggs. Anoles are unusual among lizards in that females lay single-egg clutches at frequent intervals throughout a lengthy reproductive season. This evolutionary reduction in clutch size is thought to decrease the physical burden of reproduction, but our results show that even a single egg significantly impairs stamina and sprint speed. Reproductive females also suffered a reduction in growth, suggesting that the cumulative energetic cost of successive clutches constrains the allocation of energy to other important functions. Finally, in each of two separate years, elimination of reproductive investment increased breeding-season survival by 56%, overwinter survival by 96%, and interannual survival by 200% relative to reproductive controls. This extreme fitness cost of reproduction may reflect a combination of intrinsic (i.e., reduced allocation of energy to maintenance) and extrinsic (i.e., increased susceptibility to predators) sources of mortality. Our results provide clear experimental support for a central tenet of life-history theory and show that costs of reproduction persist in anoles despite the evolution of a single-egg clutch.

Mechanisms of egg contamination bySalmonellaEnteritidis

Salmonella Enteritidis (SE) has been the major cause of the food-borne salmonellosis pandemic in humans over the last 20 years, during which contaminated hen's eggs were the most important vehicle of the infection. Eggs can be contaminated on the outer shell surface and internally. Internal contamination can be the result of penetration through the eggshell or by direct contamination of egg contents before oviposition, originating from infection of the reproductive organs. Once inside the egg, the bacteria need to cope with antimicrobial factors in the albumen and vitelline membrane before migration to the yolk can occur. It would seem that serotype Enteritidis has intrinsic characteristics that allow an epidemiological association with hen eggs that are still undefined. There are indications that SE survives the attacks with the help of antimicrobial molecules during the formation of the egg in the hen's oviduct and inside the egg. This appears to require a unique combination of genes encoding for improved cell wall protection and repairing cellular and molecular damage, among others.

Natural History of the Vine SnakeOxybelis Fulgidus(Serpentes, Colubridae) From Brazil

Aspects of natural history of the vine snake Oxybelis fulgidus from the northern region of Brazil were inferred based on the analysis of 106 preserved specimens (55 males and 51 females), and from a review of records in the published literature. Males mature at smaller size than females. Differences in body length and shape were also found among adult females and males: adult females are larger in mean snout-vent length and have relatively larger heads and shorter tails. Females have an extended seasonal vitellogenic cycle from April to December (mainly throughout the dry season). Oviductal eggs and egg-laying were recorded from September to December, while births occurred from January to April. Fecundity varied from four to twelve eggs or vitellogenic follicles (n = 13), and was positively correlated with female body length. Testicle volume is significantly larger from February to July (mainly in April and May; end of the rainy season), however the deferent ducts diameter do not differ significantly throughout the year. We hypothesized that both males and females may have an associated reproductive pattern, both synchronized in the end of the rainy season. Oxybelis fulgidus feeds on lizards (mainly iguanian) and passerine birds. Apparently, females feed more frequently on birds than males.

Ecology of the Southeastern Crowned Snake,Tantilla coronata

There are very few comprehensive studies of the ecology of small-bodied snakes. Here, we describe the ecology and demography of the Southeastern Crowned Snake (Tantilla coronata) based on 1,640 captures on the Savannah River Site in the Upper Coastal Plain of South Carolina, USA from 1951–2007. Female T. coronata were significantly longer, heavier, and heavier-bodied than males but had relatively shorter tails. Clutch size based on oviductal eggs was positively correlated to maternal body mass and length. Snakes exhibited a unimodal seasonal activity pattern that peaked in summer. Pitfall captures were significantly male-biased from July–October, corresponding to the suggested mating period for this species in this part of its range. We identified three classes of animals in the population: neonates, second year animals, and older animals that included both non-reproductive subadults and reproductive adults. Longevity was at least five years for two recaptured males originally captured as mature adults. Centipede species were the exclusive prey identified from T. coronata collected on the Savannah River Site. Our study demonstrates that research on underrepresented species is possible and can contribute to understanding of snake ecology.

Reproductive cycle of the Namibian striped skink, Trachylepis sparsa (Squamata: Scincidae) from southern Africa

ABSTRACT The reproductive cycle of the Namibian striped skink is described from a histological examination of gonadal material from museum specimens. Males followed a seasonal testicular cycle in which sperm were produced primarily during spring and summer. Testes in regression were present mainly in March. Females with oviductal eggs or corpora lutea were present September to March and May to June. Not all females reproduced annually. Clutch (= litter size) for 23 females was 4.9 ± 0.97 S.D., range: 3–6.

Detection of Salmonella in Spent Hens and Eggs Associated with Foodborne Infections

About 16,000 spent hens from 23 farms in the northern area of Japan were purchased in 1996, 1997, 1998, and 1999 to isolate Salmonella in two poultry processing plants. Salmonella was detected in 12 of 23 farms (52.2%). In particular, the serotypes Enteritidis and Infantis were detected in four and three farms, respectively. The prevalence rates in the hens' ceca, immature eggs, and the yolk of mature eggs in oviducts were 14%, 7.2%, and 6.8%, respectively. A total of 23 serotypes were detected. The major serotypes of the strains were Enteritidis, Corvallis, Typhimurium, and Infantis, but most of the strains were untypable. In the same area during 1992 to 1996, Salmonella was detected in eggs associated with four outbreaks of Salmonella Enteritidis infection and one outbreak of Salmonella Infantis infection. The ratio of contamination was approximately 1%, and the level was estimated to be 93 MPN(most probable number)/100 g in one outbreak. In farms that produced the eggs associated with all of the five outbreaks of Salmonella, the serotype Enteritidis or Infantis was isolated from hens. Farms where Salmonella was not detected were not related to any of the outbreaks.