Large Ova Research Articles

English

This study investigates some biological characters (oocyte diameter, fecundity, histological and ultra structural features) of female Mugil cephalus ovaries collected from three different natural habitats: marine (MW), brackish (BW) and fresh (FW) water. Monthly gonadosomatic index (GSI) values clearly showed that the time period of reproductive activity in female M. cephalus from marine and brackish water habitats was from early September to late November. No peak value of GSI in females collected from freshwater was observed throughout the year. Analysis of ovum diameter for M. cephalus in the two habitats revealed that, there are small diameter ova (less than 0.3 mm) and large ova (larger than 0.35 mm). The percentage of small ova diameter was 5±1% in marine habitat, while 27±3% for brackish water habitat. The mean oocyte diameters in fresh water fish were less than 350 µm. The oocytes did not develop enough to be differentiated into small and large diameter ova. The total number of ripe ova in marine fish varied between 0.84 ± 0.05 to 4.14±1.01 x106 for a total length ranging between 35 and 52 cm, respectively; whereas, the total number of ripe ova in brackish water fish ranged from 0.57±0.14 to 3.81±0.59 x106 for the same length groups. There was highly significant correlation (p>0.01) between the number and length of ripe ova in 37 and 50 cm length group from the two habitats. Yolky nucleus or Balbiani’s body and interstitial epithelial cells are a characteristic feature of oocytes at maturing stage, which is clearly detected in marine water fish with isolated follicular and active organelles. In brackish and fresh water fish ovary, the cytoplasm was compacted without accumulation of active organelles. Ultra structurally vacuolized oocyte wall in marine fish showed the presence of the fifth layer (cortical alveoli) while no cortical alveoli formation was observed in oocyte of brackish or fresh water females. The percentage of atretic oocytes in late vitellogenic ovary of marine water fish was about 2.5%, while in brackish water fish it was about 92±2%. In both brackish and fresh water fishes the initial stage of oocytes atresia degeneration was observed. In conclusion, the comparative study shows that ovary of marine and brackish M. cephalus morphologically overlaps from ripening to re-sorption stages. With the histological and fine structure characteristics, it was possible to understand the functional relationship between oocyte size and stage of fish maturation. This knowledge is of huge importance in establishing the reproductive status of the fish which is related to the functional expression of the folliculogenesis in female individuals.   Key words: Ova, Mugil cephalus, marine, brackish and fresh water fish. &nbsp

Reproductive biology of the sand dollar, Peronella lesueuri (L. Agassiz, 1841) (Echinoidea: Clypeasteroida: Laganidae), in south-western Australia

The reproductive biology of the sand dollar Peronella lesueuri was studied between 2009 and 2011 in Cockburn Sound, a large coastal embayment in south-western Australia. Individuals of P. lesueuri did not display sexual size-dimorphism, and the population was found to have a sex ratio of 1:1. Maturity occurred over the range of 80–115 mm with all sand dollars larger than 115 mm having distinct gonads. Monthly histological analysis of gonads and changes in oocyte proportions over time indicated that P. lesueuri has an annual reproductive cycle; gametogenesis occurs in spring and spawning in summer. Differences in the rate of gametogenesis between 2009/2010 and 2010/2011 may have been influenced by higher temperatures experienced in 2010/2011. P. lesueuri have large ova (mean = 210 μm), which suggests the species has lecithotrophic larval development.

Structure of sperm, spermatozeugmata and ‘lateral organs’ in the bivalveArthritica(Galeommatoidea: Leptonidae)

The position and structure of paired ‘lateral organs’ in the foot of Arthritica semen and Arthritica bifurca might indicate a chemosensory function. In both species part of the organ is also glandular. In A. semen the glandular epithelium is detached piecemeal and, probably by means of the foot, is moved to and grafted upon the gills of the same individual. The transferred epithelia appear as disk-shaped actively secretory ‘gill bodies’ which, attached to the abfrontal side of the inner demibranch, replace the ordinary unciliated gill epithelium. The secretion is liberated into the suprabranchial chamber, which serves as a marsupium, but its function is uncertain. Arthritica semen is a protandric hermaphrodite and produces very large ova that undergo a direct development that results in a non-planktonic lecithotrophic crawling juvenile stage. The sperm cells have filiform nuclei that are straight in the euspermatozoa and more or less helicoidal in what is considered to represent paraspermatozoa. By a process of aggregation, spermatozeugmata are formed which consist exclusively either of euspermatozoa or paraspermatozoa. Spermatozoa are stored in the oviduct in A. semen but in paired seminal receptacles in A. bifurca.

Linking migratory patterns and diet to reproductive traits in female brown trout (Salmo trutta L.) by means of stable isotope analysis on ova

Abstract – Many populations of vertebrates display alternative reproductive strategies involving delays in maturation processes and migrations to more productive habitats. Notably for females, migratory patterns and diet could influence reproductive traits such as ova size and number. To test this hypothesis, we targeted anadromous and freshwater‐resident female brown trout of various sizes during their return to spawn in tributaries, and carried out stable isotope analyses (δ15N and δ13C) on ova to identify their feeding areas and diet. The study was performed in the Oir River (France), a small coastal system where trout migrations to sea and within the river basin have been monitored for the last 20 years. General trends were observed in reproductive traits, such as the positive correlation between female fork length, fecundity and ova size. Fecundity was size‐dependent whatever the migratory origin of females, but major divergences were seen for ova size and isotopic ratios. Freshwater residents displayed a constant increase in ova size and a 15N‐enrichment in ova, suggesting an investment in larger ova and a shift to piscivory as the fish become larger and older. Conversely, anadromous females had smaller ova compared with freshwater‐resident females of similar body size and achieved higher fecundity as they grew bigger. Our results suggest the existence of a continuum of reproductive traits for freshwater‐resident females whereas anadromous females clearly show a break with this continuum. This major dissimilarity could be explained by the difference in growing environments in terms of food availability and quality.

The Evolution of Parental Care in the Context of Sexual Selection: A Critical Reassessment of Parental Investment Theory

Males and females are often defined by differences in their energetic investment in gametes. In most sexual species, females produce few large ova, whereas males produce many tiny sperm. This difference in initial parental investment is presumed to exert a fundamental influence on sex differences in mating and parental behavior, resulting in a taxonomic bias toward parental care in females and away from parental care in males. In this article, we reexamine the logic of this argument as well as the evolutionarily stable strategy (ESS) theory often used to substantiate it. We show that the classic ESS model, which contrasts parental care with offspring desertion, violates the necessary relationship between mean male and female fitness. When the constraint of equal male and female mean fitness is correctly incorporated into the ESS model, its results are congruent with those of evolutionary genetic theory for the evolution of genes with direct and indirect effects. Male parental care evolves whenever half the magnitude of the indirect effect of paternal care on offspring viability exceeds the direct effect of additional mating success gained by desertion. When the converse is true, desertion invades and spreads. In the absence of a genetic correlation between the sexes, the evolution of paternal care is independent of maternal care. Theories based on sex differences in gametic investment make no such specific predictions. We discuss whether inferences about the evolution of sex differences in parental care can hold if the ESS theory on which they are based contains internal contradictions.

Sperm dimorphism and spermatozeugmata in the commensal bivalve Pseudopythina macrophthalmensis (Galeommatoidea, Kelliidae)

The bivalve Pseudopythina macrophthalmensis (Galeommatoidea) is a commensal with the crab Macrophthalmus convexus (Ocypodidae) in Okinawa Prefecture, Japan. It is a protandric hermaphrodite which incubates the 65-µm large ova in the suprabranchial cavity. The species produces two types of sperm, which were studied with the electron microscope. The euspermatozoon has an elongate 2.8-µm-long, pointed acrosome, a slender 12- to 13-µm-long nucleus and a middlepiece containing several closely packed mitochondria arranged as a 5.5- to 6.0-µm-long sheath around the basis of the flagellum. The paraspermato- zoon is vermiform, 220-µm-long and up to 5-µm-broad. Anteriorly there is a ca 7-µm-long bullet-shaped acrosome followed by a subcylindrical 3.0- to 4.7-µm-long nucleus. Adjacent to the nucleus occurs a bundle of 26–42 40-µm-long flagella. The cytoplasm is packed with spherical lipid droplets and ovoid granules of unknown composition. Sperm of both types aggregate to form spermatozeugmata, which were found in the posterior mantle cavity or in paired seminal receptacles. Within the receptacles the euspermatozoa dissociate themselves from the spermatozeugma and become attached to the epithelial lining of the receptacle whereas the paraspermatozoa presumably disintegrate. The possible significance of the two types of sperm is discussed in the light of their presumed functions in gastropods.

The cypris larvae of the parasitic barnacle Heterosaccus lunatus (Crustacea, Cirripedia, Rhizocephala): some laboratory observations.

Heterosaccus lunatus parasitizes the portunid crab, Charybdis callianassa in Moreton Bay, Australia. With the host crabs maintained at 22.5 degrees C this sacculinid rhizocephalan released larval broods every 6-7 days. During July-August 1996 and particularly August 1999 such broods showed the change-over from male only larvae in the early broods to females only in the later broods. As the host crabs were maintained under similar aquarium conditions in both years it is concluded that the light/dark cycle is the principal cue triggering this larval sex reversal. Oogenesis in the parasite externa is somehow controlled to produce two different sized ova - male larvae develop from large ova and females from small ova. A working hypothesis outlining how sex is probably determined for the larvae of sacculinids is erected. H. lunatus is considered the ideal sacculinid for the further experimental work necessary to verify the proposed sex-determining mechanism and its control processes. Measurements of the maximum swimming speeds of H. lunatus male and female cyprids showed the larger males to be the faster in absolute terms (27.95 compared with 17.60 mm s(-1), respectively), however, the calculated relative speeds were almost identical at approximately 90 body lengths s(-1). Settlement experiments confirmed that female H. lunatus cyprids settle only on the gills of C. callianassa; these cyprids needed to be at least 2 days old before they were able to settle.

Egg strings in Euchirella pseudopulchra (Aetideidae) and comments on constraints on egg brooding in planktonic marine copepods

Abstract Adult female Euchirella pseudopulchra Park, 1976 from the California Current System bear a pair of unusual linear ovisacs or “egg strings.” Each membrane-bound, single file row of eggs contains 11–14 relatively large ova. Calculations suggest that the geometric arrangement of single file rows of eggs could facilitate oxygen diffusion in O 2 -deficient waters. The presence of ventrally carried egg masses in E. pseudopulchra and other members of the Calanoida appears to be associated with evolutionary loss of the fifth swimming legs (P5) in the adult female. We hypothesize that loss of the female P5 would improve hydrodynamic thrust during escape responses and reduce the probability of loss of ventrally brooded ova. We re-examine the relationship between egg size and body size for planktonic marine calanoid and cyclopoid copepods from the mesopelagic and epipelagic zones and compare the advantages of brooding versus broadcast-spawning life histories. The size distribution of adult females of 43 egg-brooding copepod species is bimodal, comprising a number of small-bodied species and large-bodied species, with only one intermediate-sized species (between 10–100 μg C). The size distribution of 75 broadcast spawners includes a large number (41) of intermediate-sized species. The interrupted size distribution of the egg-brooding species probably reflects enhanced predation risk to intermediate-sized copepods of carrying attached egg masses in the epipelagic zone.

Sharks caught in the protective gill nets off Natal, South Africa. 6. The copper shark Carcharhinus brachyurus (Günther)

Between 1978 and 1990,1 800 copper sharks Carcharhinus brachyurus were caught in the shark nets that protect the swimming beaches of Natal. The species constituted 9,6 per cent of the total shark catch. Annual catches and catch rates fluctuated widely about a mean of 138 sharks and 3,5 sharks·km net−1 respectively. Most sharks were caught at the southern beaches during the annual Natal sardine run in June and July, when shoals of pilchard Sardinops ocellatus move into the waters off southern Natal. Catches were dominated by sharks >140 cm pre-caudal length PCL. Mature males (generally ≥ 175 cm PCL) were present for much of the year, but mature females (generally ≥ 190 cm) and immature sharks were only abundant in June and July. Gonad indices in males were highest in March and April, whereas high gonad indices and large ova were recorded in females in June and July. Mating appears to take place after July and parturition about 12 months later, both occur south of the netted region. The smallest of 50 pregn...

THE GENETIC BASIS OF LIFE-HISTORY CHARACTERS IN A POLYCHAETE EXHIBITING PLANKTOTROPHY AND LECITHOTROPHY.

The polychaete Streblospio benedicti is unusual in that several field populations consist of individuals that exhibit either planktotrophic or lecithotrophic larval development. Planktotrophy in this species involves production of many small ova that develop into feeding larvae with a two- to three-week planktonic period. Lecithotrophy involves production of fewer, larger ova that develop into nonfeeding larvae that are brooded longer and have a brief planktonic stage. Reciprocal matings were performed to investigate genetic variance components and the correlation structure of life-history traits associated with planktotrophy and lecithotrophy. Our objective was to better understand persistence of this developmental dichotomy in Streblospio benedicti, and among marine invertebrates in general. Substantial additive genetic variation (75-98% of total) was detected for the following characters at first reproduction: female length; position of the first gametogenic setiger and first brood pouch; ovum diameter; three traits related to fecundity (numbers of ova per ovary, larvae per brood pouch, and larvae per brood); median larval planktonic period and the presence of larval swimming setae; but not for total number of brood pouches; larval length; larval feeding; and larval survivorship. Based on the unusual geographic distribution of development modes in this species, we hypothesize that the developmental traits have evolved in allopatry and have only recently come into contact in North Carolina. The high additive contribution to variance observed for many traits may be inflated due to (a) nonrandom breeding in nature, and (b) examination of only one component of an age-structured population at one time. Nuclear interaction variance and maternal variance accounted for 84% of the total variation in larval survivorship. This observation supports other empirical studies and theoretical predictions that nonadditive components of variance will increase in importance in individual traits that are most closely tied to fitness. A network of life-history trait correlations was observed that defines distinct planktotrophic and lecithotrophic trait complexes. Negative genetic correlations were present between fecundity and egg size, between fecundity and position of the first gametes, and between larval survivorship and median planktonic period. Positive genetic correlations were detected between fecundity and female size at first reproduction and between planktonic period and the presence of swimming setae. Intergenerational product-moment correlations were negative for larval length and fecundity, planktonic period and egg size, female size and larval survivorship, and fecundity and larval survivorship. If the genetic correlation structure observed in the laboratory persists in the field, it may constrain responses of individual characters to directional selection, and indirectly perpetuate the dichotomies associated with planktotrophy and lecithotrophy.

Life history tactics of darters (Percidae: Etheostomatiini) and their relationship with body size, reproductive behaviour, latitude and rarity

Patterns of covariation of life history traits of darters in the genus Etheostoma are reviewed. The primary pattern is associated with body size. Large darters grow faster, mature at a larger size, produce bigger clutches, and have longer reproductive and life spans, and shorter spawning seasons, than do small darters. When the effects of size are removed statistically, the dominant secondary pattern matched the r‐K continuum from fast‐growing, short‐lived, primarily semelparous species with many small ova and a high reproductive effort (r‐species) to slow‐growing, long‐lived, iteroparous species with few large ova and a low reproductive effort (K‐species). Variation in life history traits is also influenced by reproductive behaviour, latitude, and rarity (as measured by geographic range). There are significant differences in the primary and secondary life history patterns among reproductive guilds. Latitude and rarity are not correlated with these primary and secondary patterns. Instead, they account for variation of tertiary patterns. Rare species may not match the reproductive performance of more common and widely distributed species. Future studies of life history traits in darters should focus on species whose reproductive behaviour differs from that of the species reviewed in this study, and on the demographic characteristics of rare or declining populations.

Aspects of the Life History of the Slender Madtom Noturus exilis in Northeastern Oklahoma (Pisces: Ictaluridae)

The ictalurid, Noturus exilis, was studied from 13 February 1981 to 23 May 1982 in Flint and Cloud creeks in northeastern Oklahoma. Current speed, depth and substrate type in areas occupied by N. exilis were compared with frequency distributions of habitat availability. Noturus exilis were selective in their choice of current speed and substrate type; however, depths were used in the same proportion they were available. Slender madtoms in Flint Creek consumed ephemeropteran naiads and dipteran larvae most frequently by number (57.8% and 25.9%, respectively) and these organisms also occurred in proportionally more stomachs (66.1% and 57.6%, respectively). Compared with N. exilis in Green Creek, Illinois (studied by R.L. Mayden and B.M. Burr): (1) Flint Creek N. exilis were smaller at a given age; (2) Flint and Cloud creek N. exilis had a higher percentage of females that were mature in their 1st summer of life (age 0 +); (3) Flint and Cloud creek N. exilis had significantly fewer ova per gram adjusted body weight, and (4) Cloud Creek N. exilis had significantly larger ova and Flint Creek N. exilis nearly so.

The reproductive output of frogs Rana temporaria (L.) with particular reference to body size and age

Measurements were made on 274 spawn clumps and 271 adult frogs in three consecutive years at breeding sites in the west of Ireland. Mean clutch size was 1008 ± 20 ova, mean egg diameter was 2·32 ± 0·01 mm, and mean clutch weight was 11·62 ± 0·37 g. At any particular body length, larger clutch sizes were associated with smaller egg sizes and vice versa. Clutch size, egg size and clutch weight all increased allometrically with body size. The bigger females produced more and smaller eggs and a heavier clutch, relative to their body size, than smaller ones. Egg size and clutch weight also increased allometrically with female age. Age‐specific clutch weight increased during the first two years of maturity and declined slightly thereafter. Age‐specific egg size increased with age throughout life. At any age, bigger females produced more but not larger ova, and at any length, older females contained larger but fewer eggs. Both bigger and/or older females exhibited greater variability in the reproductive parameters than smaller and/or younger ones.Laboratory mating experiments showed that egg fertility was positively correlated with absolute male length and with the relative male/female length in amplexus. The fertilizing ability of males, however, declined with mating frequency, irrespective of male length, clutch size or the time interval between successive matings. In the wild, egg fertility ranged from 24–100%, although over 90% fertility was common.

Life History Traits of the Florida Sand Darter Ammocrypta bifascia, and Comparisons with the Naked Sand Darter Ammocrypta beani

The life history of Ammocrypta bifascia was studied using collections taken from five localities in the Blackwater River drainage, Okaloosa and Santa Rosa counties, Florida, between 1974 and 1977. Ammocrypta bifascia reproduced from April-July or early August. All females were sexually mature by 38 mm SL; and by 43 mm SL, all males were mature. Adult males were significantly larger than adult females. The number of mature ova in 10 females 39.5-52.5 mm SL ranged from 19-85 and was highly correlated with female size. Mean mature ovum diam for nine females were 0.88-1.24 mm (x= 1.08?0.04 mm); individual ova were 0.80-1.33 mm diam. There was no significant correlation between mean female ovum diameter and SL. The maximum life span was ca. 3 years. Individuals matured at about 1 year. Comparisons were made with Ammocrypta beani based on previous work. Ammocrypta bifascia from the Blackwater River drainage of Florida differed from A. beani from the Jourdan River drainage of Mississippi in a number of life history traits. Ammocrypta bifascia matured at a larger size, attained a larger size, reproduced for a shorter period of time, and lived longer. Ammocrypta btfascia females produced fewer but larger ova. INTRODUCTION Published data on the natural history of the Florida sand darter Ammocrypta bifascia are scarce. Williams (1975) provided limited information on the life history of A. bifascia when he described the species. He also discussed the distribution, habitat and common species associates. Bailey et al. (1954) described the habitat and species associates of A. beani ( = A. bifascia) in the Escambia River drainage, Florida. There is no other published information on the natural history of A. bifascia. Herein I present a study of the life history of A. bifascia and compare life history traits of A. bifascia and A. beani based on previous work (Heins and Rooks, 1984). Ammocrypta bifascia is a member of the beani species group in the subgenus Ammocrypta (Williams, 1975; Page, 1981). It occurs in streams of the Gulf Coastal plain of southern Alabama and northwestern Florida from the Perdido River drainage E to the Apalachicola River system (Williams, 1975; Starnes and Starnes, 1979). Ammocrypta bifascia typically is collected in moderate to large streams with shifting sand substrates in moderate current at depths of 2-4 ft; however, it also may be taken in small streams, in streams with swift current, and at depths between 6 inches and 5 feet (Williams, 1975). MATERIALS AND METHODS Collections of Ammocrypta bifascia were taken from five localities in the Blackwater River drainage, Okaloosa and Santa Rosa counties, Florida. The Blackwater River was sampled at two locations. Big Coldwater Creek and the East and West Forks of Big Coldwater Creek each were sampled at one location. The collections were made from 1974-1977 with a 3-m long, 4.8-mm Ace-mesh seine. Specimens were preserved in 10% formalin and stored in 43% isopropyl alcohol. Collections of A. bifascia are deposited in the Florida State Museum at the University of Florida. Climatic and daylength records for the nearest recording stations (Milton Experiment Station and Pensacola, Fla.) were obtained from the National Climatic Center, Asheville, North Carolina, and the Naval Observatory, Washington, D.C., respectively.

MULTIPLE PATTERNS OF DEVELOPMENT INSTREBLOSPIO BENEDICTIWEBSTER (SPIONIDAE) FROM THREE COASTS OF NORTH AMERICA

Streblospio benedicti Webster, a small tube-dwelling polychaete common in Pacific, Gulf of Mexico, and Atlantic estuaries of North America, exhibits both lecithotrophic and planktotrophic modes of larval development. In lecithotrophic forms females produce few (9-50) large ova (100-200 µm diam.). These develop in dorsal pouches into 9-12 setiger larvae, competent to settle at release. Females of planktotrophic forms produce large broods (100-548) of small ova (70-90 µm), brood larvae in dorsal pouches or beneath dorsal branchiae, and release 3-7 setiger larvae which bear long swimming setae and feed in the plankton for 1-5 weeks before settling. Lecithotrophy is reported for S. benedicti populations on all three coasts of N. America, planktotrophy from the Atlantic and Gulf coasts only. Reproductive differences observed in the field are maintained by laboratory cultures reared under constant (20°C) conditions, though individuals from planktotrophic and lecithotrophic populations are interfertile. Developmental variations observed in the field are believed to generate different patterns of dispersal, recruitment, population growth (r), and mortality. Poicilogony, the occurrence of multiple development modes, may account for the considerable success of S. benedicti in N. America.

The Partitioning of Reproductive Energy between Ova and Protective Capsules in Marine Gastropods of the Genus Conus

The physical strength and energetic cost of egg capsules belonging to 10 species of Hawaiian Conus were determined in the laboratory. Capsular material was found to contain 5442 cal/g as opposed to 6238 cal/g for ova. Capsules accounted for up to 50% of total reproductive energy devoted to capsules and ova. Both the puncture resistance of capsules and the proportional energy allocation to capsules increased with increasing development time. Development time was found to be positively correlated with egg size. Strong capsules produced by species with large ova may have evolved as a result of selection for improved protection of embryos from predation and physical stress during a protracted period of development. The increasing allocation of reproductive energy to capsules as a function of egg size reflects the cost of producing stronger capsules.

Ontogenetic Energetics in Ambystoma

The magnitude and effects of intrapopulational variability in the sizes of eggs produced by the salamanders Ambystoma maculatum, A. opacum, and A. tigrinum have been investigated by calorimetric and respirometric procedures. It has been found that some females produce eggs with as many as 29.0 cal while others in the same population at the same time produce eggs with as few as 16.5 cal. Significant differences in the dry weight-specific energy content of ova have been found at the species, population, and individual levels, but the contribution of this variability to the variability in total energy content of ova is relatively low. All embryos regardless of species or temperature use 1.45 cal in order to hatch. Development to the feeding stage is more efficient for embryos that develop from larger ova and at warmer temperatures, offering an explanation for altitudinal and latitudinal variation that is often seen in egg size in amphibians. The effects of a fluctuating temperature environment are shown to b...

Study on the Metagonimus sp. in Gum river basin, Chungchung-nam Do, Korea

This study was undertaken to elucidate the status of Metagonimus species infection and to demonstrate the first and the second intermediate hosts of the fluke at the several localities along the Gum river, Chungchung-nam Do, Korea from March 1979 to October 1980. The results are summarized as follows: 1. Total 790 stool specimens of inhabitants from 6 localities along Gum river were examined by the combination of cellophane thick smear technique and formalin-ether concentration technique. The positive rate of intestinal helminths was 80.3 %, and the egg positive rate of Metagonimus sp. was 21 % from a total of 790 specimens examined. In the age bracket of 20~49, the positive rates of Metagonimus sp. were 31.1~36.5 %, and the males (26.8 %) were infected three times higher than females (8.9 %). By the area of the river, Gumsan which is located upper stream showed the highest positive rate (40.5 %) of the fluke, whereas the rates decreased gradually toward upper part of river (Muju) or the descending lower area of the river. The most lower area of river (Gangkyeong and Nonsan), no positive Metagonimus infection case was found. 2. The infection rate of Clonorchis sinensis in 790 was 37.3 %, and the status of mixed infection of Metagonimus with C. sinensis was found 127 cases (76 %) out of 166 cases with Metagonimus infection. 3. The result of measurement of ova from 166 cases of Metagonimus infection, large ova were found in 41.1 %, small size ova in 31.9 % and the mixed type in 27.1 %, respectively. The adult worms were recovered from the 6 cases after treatment with niclosamide, and the measurements of the worms showed similar morphological characteristics of the Metagonimus yokogawai. 5. Twenty-two species in 5 families of fresh water fish were caught. Out of 22 species of fish, 18 species were found infected with metacercaria of Metagonimus. In order to observe the distribution of metacercariae in the body and the rate of infection of the individual host, a total of 94 Pseudogobio esocinus were examined. Total 84 (89.4 %) out of 94 fish were infected with the metacercariae and the rates of distribution of the metacercaria were observed in the following order: on scale; 93.4 %, in gill; 3.2 %, head part; 2.9 %, but a few metacercaria was found in muscle and visceral organs. 6. The development of the metacercariae which were isolated from the scale of Pseudogobio esocinus were experimentally traced in the albino rat host from one day to 30 days after infection. At the 6th day, several eggs were visible in the uterine tubule of the some worms, on the 10th day, worms became 326.0 x 208.0 micrometer in size, however the bodies of worms grew no more until the 30th day after infection. The oral sucker was larger in size than the ventral sucker during early stage of the worms, but the 7th day after infection, it reversed. The ventral sucker situated on the ventral right side of the body. Right side of testis laid somewhat toward, and uterus and vetellaria extended to the posterior margin of the right testis. 7. Snails(Koreanomelania nodifila var. ovulum) were collected in the river, Buri-Myeon, Gumsan-Gun, and found the natural emerging ophthalmo-pleurophocercus cercaria. From the above result, the prevalence of Metagonimus species infection showed relatively higher rates from the inhabitants along the middle to upper localities of the river. Even though no sweetfish was caught in the surveyed areas, Gum river basin is the one of the new endemic foci of metagonimiasis in Korea.

Reproductive Cycle and Fecundity of White Bass in Lewis and Clark Lake

Abstract Fecundity and seasonal changes in ova size and development, fish condition, and percentages of body weight contributed by gonads and mesenteric fat were studied for white bass (Morone chrysops) from Lewis and Clark Lake on the Missouri River, in 1969 through 1971. Spawning occurred in late May and early June; the average length of the season was 25 days. Females spawned only about 50% of their ova; large ova were shed during spawning and smaller ova were retained and resorbed by late July or early August. Maturation of new ova for the following year's spawning began in early August, when only primary oocytes were present in the ovaries. The number of ova produced by fish of a given length declined progressively from 1969 through 1971. Fecundity was more directly related to length than to age of fish. Condition factors for both sexes were highest in November, remained high through May, declined after spawning, and reached an annual low in August. Percentages of total weight contributed by gonads w...

Contributions to the concepts of reproductive cycles and the systematics of the scalaris group of the lizard genus Sceloporus

The concept of parity type is proposed as a criterion of relation- ship among members of the Sceloporus aeneus-scalaris complex, with members of S. aeneus being regarded as and those of S. scalaris, as oviparous. The S. goidmani is regarded as a relative of S. aeneus , and S. a. subniger is not regarded as intermediate between S. scalaris and S. aeneus. The proposal by Davis and Smith that S. a. aeneus is oviparous and specifically distinct (as S. aeneus) from S. a. bicanthalis (as S. bicanthalis) is rejected. S. aeneus is hypothesized to have a biennial reproductive cycle. S. scalaris slevini auctorum is segregated into two subspecies: S. s. samcolemani subsp. nov. in the Sierra Oriental (northern end), and S. s. slevini sensu stricto in the Sierra Occidental (also northern end) of Mexico and of the adjacent United States. The systematics and phylogenetic history of the scalaris group of Sceloporus has long been viewed as enigmatic, beginning with the statement of the quandary by Smith (1939: 347-348) in explanation of the allocation of the northwestern member, slevini , to the species scalaris despite some contrary evidence. However, Smith and Pog- layen (1958: 13-15) allocated slevini to the species aeneus after another population exhibiting certain features of intermediacy be- tween the two polytypic species scalaris and aeneus was described (S. a. subniger) . Neither of the preceding accounts placed any overt emphasis upon parity types. Smith (1939: 332) made a passing comment that both oviparous and 4 'ovo viviparous species occur in the group. Evi- dence now available makes it certain that members of the scalaris complex are oviparous, and we here postulate that members of the aeneus complex are (a broader term, more certainly ap- plicable than ovoviviparity, which has come to imply absence of placental structures, whereas euviviparity implies their presence; both conditions exist in reptiles and only by microscopic techniques can they be determined). Anderson (1962) has demon- strated that slevini is oviparous, and accordingly its allocation with the scalaris complex is correct. The most critical doubt cast upon this hypothesis is the proposi- tion by Davis and Smith (1953: 102) that S. a. aeneus is oviparous, whereas S. a. bicanthalis is incontrovertibly (Smith, 1939: 356, and personal data). On this basis these taxa were elevated to specific status ( S. aeneus , S. bicanthalis) . The data provided in Davis and Smith, however, strongly suggest that in S. a. aeneus viviparity does occur, but on a two-year cycle. Ten of 28 females collected from 25 July to 15 August contained from 3 to 5 (average 4) large ova,