Average Egg Size Research Articles

Fecundity of Lake Sturgeon (Acipenser fulvescens, Rafinesque) in Lake Winnebago, Wisconsin, USA

Summary Sturgeon species are known for their relatively high fecundity, with some reported to carry as many as 7.7-million eggs. However, the fecundity of lake sturgeon (Acipenser fulvescesn Rafinesque) has not been thoroughly studied, with limited information available primarily in gray literature and agency reports. Our objectives were to quantify (1) the fecundity and gonadosomatic index (GSI) of female lake sturgeon in a winter F4 stage of development; 2) the average size and weight of F4 lake sturgeon eggs; and 3) relationships between lake sturgeon fecundity and fish weight, length, and age. Total length, weight, age, gonad weight, fecundity, egg diameter, and egg weight were sampled from 14 female lake sturgeon in an F4 stage of egg development in February 2005 from the Lake Winnebago System in Wisconsin. Mean fecundity was 383,529 eggs and the mean GSI was 22.9. Egg diameter averaged 2.74 mm and egg weight averaged 17.34 mg. Weight was the best predictor of fecundity (r 2 = 0.66). Fecundity data for lake sturgeon larger than 35 kg are needed to allow better estimation of fecundity for larger fish.

Biology and Breeding Ecology of the East Asiatic Water Rail on Shunkunitai Island, Hokkaido, Japan

Research on the Water Rail (Rallus aquaticus indicus) was conducted on Shunkunitai Island, Nemuro, Hokkaido, Japan in July 1998. A total of 23 Water Rail individuals or pairs responded to playbacks of Water Rail calls. All observed Water Rails inhabited wet hollows between long, low dune ridges. We recorded 11 different call types, captured 21 Water Rails, and banded 16 of them. Seven adults showed new feather growth; six showed brood patches. All captured adults had black-and-white barred under-tail coverts. The average number of black-and-white barred outer median and lesser wing-coverts on the left wing (dorsal surface) was 14. We found eight different types of vegetation in the 23 Water Rail territories and around seven nests. Vegetation height was 1.17 m on average (excepting Utricularietum intermediae and Alnetalia japonicae). Fresh water in the wet hollows was above the average sea level because of natural barriers and dense vegetation; the depth of water or (floating) root bed was 4-60 cm. The acidity (pH) of the surface water was 5-8. Phragmites australis was a dominant cover vegetation. We found three nests that contained egg clutches. The average water depth around nests was 10 cm; average nest height, 17 cm; average outside diameter of nests, 22 cm; average diameter of the nest bowl, 12 cm; average egg size, 38.2×26.4 mm; and average egg weight, 14 g. The median maximum nest bowl depth was 6 cm. Breeding occurred from May to July. Plant species used as nest materials were those found in the immediate vicinity of the nest. Wind-dried nest material from four nests weighed 95 g on average.

Reproductive Ecology of Tibetan Partridge Perdix hodgsoniae in Lhasa Mountains, Tibet

Data on the breeding ecology of Tibetan Partridges (Perdix hodgsoniae) were collected in shrub environments near Lhasa, Tibet, during 1999-2001. Partridge flocks broke up in mid-March and individuals typically formed socially monogamous pair bonds. During daily activities the both members of the pair were close to each other, with 73.5% of observed individual distances less than 2m. The egg-laying period extended from late May to late June. Average egg size was 16.1 (±SE=0.2) g in mass and 39.2 (±0.1)×28.1(±0.1) mm in dimension. Average clutch size was 8.3 (±0.8, range 5-12) The partridge produced larger eggs and smaller clutches than its two congener species, Grey Partridge (P. perdix) and Daurian Partridge (P. dauuricae). Incubation lasted about 23 days, and 44.4% of clutches successfully hatched. Vegetation characteristics were the most important determinants of partridge nest-site choice, with patches of low, sparse, and secondary cover being preferred. Nest-sites were also significantly closer to paths than random sites.

An Endemic Human Infection with Heterophyes nocens Onji et Nishio 1916 at Mikkabi-cho, Shizuoka, Japan.

Human Heterophyes nocens infection was confirmed in 2 areas of Mikkabi-cho, Shizuoka Prefecture where high prevalence of Metagonimus yokogawai infection had been reported. The total prevalence showed 9.6% by stool examination. Among the patients, the older age's males predominated, and the infection within the same family was often observed. Adult worms were collected from stool samples of the patients after treatment with praziquantel. The worms were identified as H. nocens with morphological characteristics. The average size of eggs (27.8×16.1 μm) appeared in stools of the patients was slightly larger than that reported earlier, and rather equivalent to eggs of M. yokogawai. Questionnaire study revealed a correlation of a habit of eating raw fish, mullet in particular, and the trematode infection in Hamana Lake.

Oviposition Site Preference and Factors Influencing Egg Mass Characteristics of the Saw-Combed Fishfly (Megaloptera: Corydalidae) in Southern Maine

We surveyed microsite conditions in the oviposition location used by female saw-combed fishflies (Nigronia serricornis) to investigate the relationship between egg hatching success and egg mass features and oviposition site selection. Egg-laying females showed a significant tree species preference at two of three sites sampled. Leaves used as ovipositon sites differed in length, width, area, and height among sites, but differences in oviposition site characteristics were attributable to stream habitat conditions, not preference. Egg hatchmg rates were very high (ca. 95%) and did not differ between streams. Egg mass size was sipficantly different among sites, but average egg size was not. Egg size was not correlated with egg mass size, but hatching rate was significantly correlated with egg mass size. Recruitment estimates ranged from <25 to >95 hatchlings per m2. Although leaf height, leaf length, and stream site were significant in predicting egg mass size, females showed great plasticity in selection of oviposition sites and no correlations were found between hatching success and microsite conditions.

Parasitism, water temperature and life history characteristics of the freshwater fish Gobiomorphus breviceps Stokell (Eleotridae)

Abstract – Life history traits can vary among populations of the same fish species in response to selective pressures exerted by the local environment. Here we used inter‐population comparisons to investigate the effects of parasitism and variability in water temperature on life history traits in a New Zealand freshwater fish, the upland bully. Although age and size at maturity varied among populations, they were not significantly related to either temperature regime or average parasite load. Trade‐offs between egg size and clutch size were only apparent in one of the seven populations when populations were analyzed separately but became clear when all data were pooled. However, neither average population clutch size or egg size was related to the population’s mean parasite load or the local temperature regime. Although the latter two parameters may influence other life history variables, such as the number of clutches produced per season and the partitioning of eggs among clutches, there was no evidence that they influenced life history strategies of the upland bully populations investigated here.Note

Monthly variation in recruitment, infection, size, fecundity and mating of Naobranchia variabilis (Copepoda : Naobranchiidae) parasitic on the gills of toadfish Tetractenos hamiltoni from Moreton Bay, Australia

Naobranchia variabilis on the gills of Tetractenos hamiltoni were sampled monthly from July to June. Recruitment began in August, peaked in October, and was low from January. Most late juveniles occurred in November. Numbers of subadults declined from July, with none in October; intensity peaked during November–December. Adult prevalence and intensity declined from August, to consist only of large, mature individuals in October with many large eggs and with a large percentage of these adults shedding eggs. Adult prevalence and intensity peaked in January; average adult size and number of eggs were consistent after January. The presence of small adults from November reduced the average number and size of eggs. Adults produced at least two batches of eggs, and eggs were produced and shed all year round. At least 75% of the female N. variabilis had no male attached, but numbers of males and females in each age class were correlated. Most males on late-juvenile and subadult females occurred during the period of greatest recruitment, but was later for adult females because of the preference of males for pre-adult stages.

Relationships between Maternal Size, Egg Size, Clutch Size, and Hatchling Size in European Lacertid Lizards

The interspecific relationships among female size, clutch size, egg size, and hatchling size were examined for 64 European lacertids. The eggs of all species increased linearly in both linear dimensions and mass during incubation. Across species initial egg mass was positively correlated with juvenile mass, with an allometric relationship exponent of 0.87. Initial egg mass across species increased proportionally with female mass to the power of 0.57. Moreover, an increase in maternal mass was also accompanied by an increase in clutch size. The number of eggs per clutch across species scaled with female mass to the power of 0.39. Removing the effect of female mass resulted in a negative correlation between egg mass and clutch size. Species for which the average egg size was lower than expected on the basis of female mass, tended to have larger relative clutch size. The total egg mass per clutch was about one third of female mass (exponent 0.94).

BIOECOLOGY OF DIORYCTRIA ABIETELLA DENIS AND SCHIFF. A PEST OF CONIFERS IN THE NORTH-WESTERN HIMALAYA

Cones and seeds of conifers, such as Pinus roxburghii, P. wallichiana, P. gerardiana, Cedrus deodara, Abies pindrow and Picea smithiana are seriously damaged by Dioryctria abietella Denis and Schiff. (Lepidoptera : Pyralidae) in the North-Western Himalayan region of India. Bioecological studies carried out during 1991 - '92 revealed that the females laid whitish, elliptical eggs singly on the depressed surface of the young cones. The average egg size was 1.00 ± 0.11 x 0.60 ±0.08 mm and this stage lasted for 3 - 5 days. The larval stage passed through five instars. All the instars differed in appearance, size and duration and larvae became full-fed in an average of 24.8 ± 1.9 days. The full-fed larva spun a cocoon around itself, sealed it with white papery membrane and pupated inside the cone or any other outside protected place. The prepupal and pupal periods lasted for 7-8 and 10-14 days, respectively. The pupa was dark brown, 13.8 ± 0.07 mm in length. Total period from egg to adult varied from 46 to 59 days (52.7 ±4.8 days). Adults were dirty brown in appearance and were 13.59±0.115 mm long with an average wing expanse of 29.0 ± 1.00 mm. They lived for 4 to 5 days. Under laboratory conditions, the pest completed two generations per year and full-fed larvae of 3rd generation overwintered during September - October. Two larval parasites belonging to order Hymenoptera and Diptera, and a fungal pathogen (Fusarium sp.) were found associated with this pest. The detailed biology, nature and extent of damage, along with its distribution have been discussed and methods of control suggested. Key Words: Insect biology, Insect ecology, Dioryctria abietella, Coniferae, North-Western Himalaya, Forest pests

Allometric Engineering: A Causal Analysis of Natural Selection on Offspring Size

Techniques of offspring size manipulation, "allometric engineering," were used in combination with studies of natural selection to elucidate the causal relation between egg size and offspring survival of lizards. The results experimentally validate premises underlying theories of optimal egg size: fecundity selection favoring the production of large clutches of small eggs was balanced by survival selection favoring large offspring. However, large hatchlings did not always have the highest survival, contrary to most theoretical expectations. Optimizing selection on offspring size per se was the most common pattern. Moreover, matches between average and optimal egg size were qualitative, not quantitative, perhaps reflecting known functional constraints on the production of large eggs.

Effects of Egg Size and Density on Metamorphic Traits in Tadpoles of the Natterjack Toad (Bufo calamita)

Effects of Egg Size and Density on Metamorphic Traits in Tadpoles of the Natterjack Toad (Bufo calamita)

Adaptive, genetically based differences in life history between estuary and freshwater threespine sticklebacks (Gasterosteus aculeatus L.)

Life history theory predicts that migratory fishes should delay reproduction, be larger at maturity, and have higher fecundities than nonmigrants. We tested this hypothesis by comparing life histories of laboratory-reared estuary and freshwater threespine sticklebacks (Gasterosteus aculeatus L.) from the Navarro River, California. We also estimated phenotypic correlations and genetic variance (broad-sense heritabilities) for reproductive characteristics of these fish. The more migratory estuary sticklebacks delayed reproduction, were larger at first reproduction, and had higher fecundities than the freshwater fish. We found no significant differences in interclutch interval or average size of eggs. The body size – fecundity relationship did not differ among these populations, unlike the findings in previous reports comparing anadromous and freshwater threespine sticklebacks. We found significant levels of genetic variance for age and size at first reproduction in both populations, and for fecundity in the freshwater population. The estuary and freshwater sticklebacks did not differ in average number of fin rays, gill rakers, or lateral plates, indicating that differentiation in life history has not been accompanied by significant changes in these characteristics. These results provide evidence of genetic divergence between these populations with respect to life histories, and the nature of these differences suggests that adaptation to different migratory life-styles has occurred.

Some observations on the life cycle and population dynamics ofTalitroides topitotum(Burt) (Amphipoda: Talitridae) in Hong Kong

A study on the life cycle and population dynamics of a terrestrial amphipod Talitroides topitotum in Hong Kong revealed that T. topitotum was semelparous with an average life span of ten months, and had three to four generations per year. Talitroides topitotum could produce up to two broods during its life time with an average brood size of 3·4 eggs, and an average egg size of 0·15 mm3. The male/female ratios were significantly less than unity in April. We suggest that the biased sex ratios could be a result of a difference in longevity between the sexes. The possible adaptive significance of this was discussed.

Food Supply and Reproductive Performance of the American Oystercatcher in Virginia

The relationship between food supply and reproductive performance was determined in a 3-year study of the American Oystercatcher, Haematopus palliatus, in Virginia. Clutch size, clutch-initiation dates, interclutch intervals, fledging success, distance to food, and quality and density of food were examined for 41 territories. Food supply varied more among territories than did clutch size, clutch-initiation dates, or interclutch intervals. Annual and interannual fledging success was extremely variable. Although no measure of food supply contributed significantly to variation in clutch size, the size of nearby feeding areas was positively correlated with average egg size and fledging success and was negatively correlated with the date of first clutch initiation. Earlier laying females had greater fledging success. Of the measures of food supply only the size of the nearby feeding area contributed significantly to variation in fledging success. Growth rates and rates of provisioning young were similar among broods of different sizes. In general, the match between food supply and reproductive performance was poor. As predation was the major cause of chick losses, I suggest that better territories for oystercatchers are those that allow parents to watch for predators of the young, and forage at the same time.

Seven cases of Diphyllobothrium latum infection

Seven cases of Diphyllobothrium latum infection were proved by collection of worms after praziquantel treatment between October, 1986 and July, 1987. The patients were all males aged 20-44 years residing in Seoul or Ulungdo, Kyungpook Province. All of them had the history of eating several kinds of raw marine fishes, and they had never been to abroad. One of them experienced abdominal pain and 6 experienced natural discharge of a chain of worm segments, but none revealed any sign of anemia. Total 12 worms (1-3/patient) were collected after praziquantel treatment. The worms were 85-423 cm in length, and revealed the characteristic rosette-shape uterus in their gravid proglottides. The average egg size varied 61.0-65.3 x 41.7-46.1 microns. The eggs were yellowish-brown, and ovoid to elliptical. Including the present 7 cases, the total number of human D. latum infections proven by worms in Korea becomes 28 cases.

Reproduction in an Irish lake population of the crayfish Austropotamobius pallipes (Lerehoullet)

SUMMARY. 1. Mature crayfish were collected in 1984 from an alkaline Irish lake before and after the mating season.2. There was some correlation between frequency of mating and decrease in vasa deferentia weight in captive males, but in the field vasa deferentia weight losses were highly variable. The data indicate that one third of adult males may not have mated in the wild.3. All females appear to have spawned, whether or not mated, with an average 85% reduction in ovary weights over the season.4. Pleopodal egg counts directly after laboratory spawning were on average 81% of ovarian counts; in the field, an estimated 50 days after spawning, they were only 61% of estimated ovarian egg numbers.5. Average ovarian egg size was positively correlated with female size. Also, larger crayfish had a wider range of egg sizes than smaller crayfish.6. It is suggested that aggression and competition for shelter among brooding females may result in a progressive loss of eggs.

Studies on the Metagonimus fluke in the Daecheong reservoir and the upper stream of Geum river, Korea

The prevalences of the fluke belonging to genus Metagonimus have been reported along the upper stream of inhabitants by several workers since 1980, however the taxonomical problems of the fluke was not yet settled. The larval flukes; cercaria and metacercaria as well as their intermediate hosts, and adult were studied in order to identify the Metagonimus in the areas. The results obtained are summarized as follows: The snails, Semisulcospira globus were collected from the three different localities along the upper stream of the River. The cercariae were found from 125(7.2%) out of 1,730 snails by natural emerging method, and were identified into 5 species including Metagonimus sp. (3.7%), Pseudexorchis major(1.4%), Cercaria nipponensis (0.9), Cercaria incerta (0.6%) and Cercaria yoshidae(0.6%). Cercariae of Metagonimus species had four to five oral spines on its anterior of the first line. The cercariae of Metagonimus were experimentally exposed to goldfish. Infection rate was 22.9% out of 105 goldfish, and the encysted metacercariae were found in fins(86.7%) and on scales (13.7%) of the fishes, but not in their muscle, head or visceral organs. Seven species of fish were caught in the Daecheong reservoir and the upper stream. Infestations with metacercaria of Metagonimus were found 100% in Opsariichtys bidens and the parasitized numbers of the metacercariae were observed from 250 to 2,400 per fish. In the upper stream, Zacco temmincki, Z. platypus and Pseudogobio esocinus were infected 100% with the metacercaria, on the other hand, the fishes caught in the reservoir showed the lower infestation rates, and a few metacercariae found in the fishes Carassius carassius and Cyprinus carpio in the reservoir and the stream. The majority of metacercariae was detected only on the scales of fishes. In order to know the infectivity and the distribution patterns in the intestine of hosts, rats and dogs were infected with the metacercariae obtained from O. bidens and Z. platypus. In addition the metacercariae obtained from Z. temmincki, P. esocinus and goldfish were given to the rats. The recovery rates of the worms in the small intestine of dogs were higher (63.3-65.8%) than those of the rats (3.5-31.6%). The flukes were found mostly in the middle and the lower part of small tntestine of the rats and the dogs, but no worm was collected in the upper part of the intestine of rats. The size of adult flukes varied by the hosts. In the adult flukes, oral sucker was smaller than ventral sucker, and the right and left testes were located diagonally, the uterine tubules circled around the upper left testis. The average egg size was 29.1 x 17.7 micro-meter. According to the above results, the flukes belonging to genus Metagonimus distributed along the Geum River was concluded to be identical with Miyata type of M. yokogawai as that Saito had proposed.

Clutch Initiation Dates, Clutch Size, and Egg Size of the American Oystercatcher in Virginia

AbstractThe timing of egg laying, clutch size, and egg size of the American Oystercatcher (Haematopus palliatus) were studied over six consecutive breeding seasons in Virginia. Synchrony of laying dates occurred in each of five localities of the study area in at least one year. Mean clutch size was 2.8 eggs (mode = 3) in first clutches and 2.4 eggs (mode = 2) in replacement clutches. Individual females laid replacement clutches of the same size and laid eggs of similar average volume in all years. A change in mate had little effect on the date on which females initiated their first clutches in successive years. The average egg size in a clutch was correlated with the size of the laying female. Egg-size ordering occurred within clutches, the first-laid egg being smaller than the second egg and about equal in volume to the third. We propose that the second egg is largest because it has the highest probability of hatching, and the resulting sibling hierarchy reduces the frequency of sibling competition.

Five Cases Of Diphyllobothrium Latum Infection

Five cases of Diphyllobothrium latum infection were proved by collection of worms after treatment with bithionol, niclosamide or praziquantel, during 1975~1983. The patients were 4 males and one female aged 10-64 years residing in Seoul or Wando-gun, Chollanam-do, Korea. All of them remembered the history of eating several kinds of raw marine fish and 2 persons said they ate the raw flesh of perch, Lateolabrax japonicus. Three among them experienced abdominal pain, 2 natural discharge of a chain of segments, but none revealed any sign of anemia. The average egg size in stool varied 59-67 x 41~48 micrometer according to cases. The eggs were characterized by ovoid to elliptical shape, terminal operculum, and distinct abopercular protuberance. One naturally discharged segment (30 cm) and 4 complete strobilae (320~680 cm) with scolices obtained after treatments were examined. The morphological characters of proglottids such as rosette-form uterus with 3~6 loops, vaginal pore included in the cirrus sac, separated seminal vesicle from cirrus sac etc. were all compatible with D. latum. These are the 7th~11th cases of D. latum infection proved by worms in Korea.

Embryonic development of the camel tickhyalomma dromedarii(ixodoidea: ixodidae)

Abstract The embryology of Hyalomma dromedarii was investigated by studying serial sections of softened chorion eggs. Embryo size changes were recorded. Cleavage began within 3 hrs after oviposition and was indicated by vitellophages of different sizes. Average egg size (AES) during cleavage was 0.98 × 0.97 mm. Mitotic division and nucleus migration continued for 8 days until blastoderm formation (AES 1.06 × 0.93 mm). Primordia and layers formed on day 10 when the egg became spherical (AES 1.07 × 1.07 mm). Differentiation of the germ band to capitulum, ambulatory and opisthosoma segments was on day 12 (AES 1.32 × 1.1 mm). During this stage the embryo enlarged. Nervous system tissues became apparent on days 14–15; the differentiated germ band elongated and the embryo size was reduced (AES 1.04 × 0.96 mm). The digestive system, rectal sac, and anus appeared on day 16 after oviposition and the embryo became elongated (AES 1.38 × 1.08 mm). On day 17–18, the appendages, nervous tissues, and rectal sac were for...