Total Reproductive Potential Research Articles

Transfer of the fittest: using preimplantation genetic testing for aneuploidy to select embryo(s) most likely to lead to live birth

Preimplantation genetic testing for aneuploidy (PGT-A) was developed to identify euploid embryos from a cohort of embryos with unknown ploidy produced during an invitro fertilization (IVF) cycle. In recent years, the ability of PGT-A to improve IVF outcomes has come into question. The goal of this review was to summarize the major randomized controlled trials (RCTs) and nonselection studies evaluating the benefit of PGT-A to improve the live birth rates (LBRs). We argue that the LBR per transfer is more relevant to the individual patient than the cumulative LBR as a means to minimize the burden of IVF by reducing futile transfers, pregnancy losses, and ongoing aneuploidy. The early RCTs demonstrate improved implantation rates and LBRs with PGT-A for embryo selection vs. traditional morphology. However, these studies are limited by the small sample size and a bias toward good-prognosis patients. Further studies using next-generation sequencing found more variable results but did confirm an improvement in the LBRs per transfer in an older population with a higher baseline risk of aneuploidy. The largest RCT to date showed similar cumulative LBRs in the PGT-A and control groups after biopsy and sequential transfer of up to 3 blastocysts with a significant reduction in the cumulative clinical pregnancy loss rate in the PGT-A group. Nonselection studies evaluating pregnancy outcomes after transfer of euploid vs. aneuploid embryos demonstrate near-perfect negative predictive value for an aneuploid result to predict live birth. Putative mosaic embryos had similar LBRs compared with euploid embryos. The available RCTs and nonselection studies support the practice of using PGT-A to identify euploid embryos for transfer, especially in an older population, while simultaneously selecting against aneuploid embryos, without negative impact on the total reproductive potential of the cycle.

Spatial and Temporal Variation in Annual versus Biennial Reproductive Cycles in Eastern Bering Sea Snow Crab Chionoecetes opilio

AbstractThe stock assessment model currently used for the management of the fishery for snow crab Chionoecetes opilio in the eastern Bering Sea assumes an annual reproductive cycle. However, temperatures below 1°C can extend the snow crab reproductive cycle to 2 years, which could depress the total reproductive potential of the stock. Our objective was to determine the prevalence of snow crab in the eastern Bering Sea on a biennial reproductive cycle, relative to latitudinal and thermal gradients, and evaluate whether available bottom temperature data could be used to predict the proportions of biennial spawners. Mature female snow crab were collected on the annual National Marine Fisheries Service eastern Bering Sea bottom trawl survey during 2014–2018. Bimodality in the frequency distribution of oocyte area suggests that oocyte area can likely be used to distinguish annual and year‐1 biennial spawners from year‐2 spawners. In 2014, the highest rates of biennial reproduction were found in northern, colder areas in the eastern Bering Sea. In 2015–2018, very low rates of biennial reproduction coincided with warm temperatures across the eastern Bering Sea. This work could help in the estimation of female reproductive potential and allow the development of female‐based reference points for the eastern Bering Sea snow crab fishery.

Формы существования предкавказской кумжи - Strutta caucasicus (Дорофеева, 1967) Каспийского бассейна

A morphological analysis of brooks trout in Dagestan showed that each spawning herd is morphologically unique and differs from the rest in a certain set of characters. However, all of them, when comparing the age composition, spawning conditions, the extent of spawning migrations in rivers, etc. have a lot in common. All of them meet the definition of a population as a group of individuals united by panmixia, a single territory and isolated to one degree or another from similar groups within the species. The morphological characteristics of trout in the upper of rivers Avar, Andi, and Kara-Koysu further confirms the validity of this approach. Presumably, the structure of trout populations is in continuous change and the differences in morphological indicators are phenotypic in nature and reflect the biotic and abiotic conditions prevailing in this region. The interaction of variability and selection in the population maintains a mobile equilibrium of biological properties forms the passing (brown trout) and residential (trout) forms.
 The trout of Sulakriver breaks up into several local herds (trout of Avar Koysu, Andi Koysu, Kara-Koysu, etc.) with a specific and limited range of its migrations. To a certain extent, differing from neighboring ones, each of the herds maintains its integrity and does not mix with the rest. Thus, the brooks trout of Dagestan seem to combine two functions - the self-reproduction of local settled populations and generating migrant individuals in the Caspian trout (Terek, Samur, Kara-Su rivers, etc.).
 In the rivers of the Kara-Su system, regardless of the place of fishing and the season, trout is represented by almost 100% males. Naturally, the question arises: who ensures the reproduction of trout herds in the absence of females? At the same time, the Salmo truttacis caucasicus (Dorofeyeva, 1967) comes to spawn in these rivers, and its livestock is represented exclusively by females (70-80%). Therefore, brooks trout of the Kara-Su system rivers and the Salmo truttacis caucasicus, coming here to spawn, should be considered as a single reproduction fund. Eggs, laid by either a brown trout female or a trout female, can leave individuals, that roll into the sea and turn into a passing trout, and individuals that remain in the river will be called brooks trout.
 The total reproductive potential of small rivers of the Dagestan coast of the Caspian Sea is currently no less than in native salmon rivers (Terek, Samur). That is why small rivers play an important role in the natural reproduction of trout and brown trout. Among the small salmon rivers of Dagestan, the greatest fishery value have tributaries of the Sulak river, rivers of the Kara-Su system, Shura-ozen, Manas-ozen, etc. Significant differences in the climatic features of these areas inevitably affect the biology of trout inhabiting them.

Current clinical applications of antimullerian hormone.

Determine if literature supports the use of anti-Müllerian hormone (AMH) as a useful biomarker of reproductive potential when cumulative live birth rates (CLBRs) per retrieval are used as the outcome variable. Advances in technology used in in-vitro fertilization (IVF) permit the use of single embryo transfer to achieve expected pregnancy success rates. Many IVF cycles result in the creation of more than a single embryo suitable for transfer per oocyte retrieval. Cryopreservation permits subsequent use of other embryos with no loss in total reproductive potential from single retrievals. Therefore, an emerging concept in IVF is the CLBR per retrieval as an indicator of the patient's reproductive potential. Using the total reproductive potential from a single retrieval may help patients decide on IVF. As such, any predictor of success that relies upon the live birth rate for a single transfer, as opposed to CLBR per retrieval, is inadequate to estimate the true reproductive potential for patient. AMH has been proposed as a biomarker for reproductive potential, but most studies have correlated an AMH value to a single embryo transfer. A more appropriate way to use AMH levels may be to correlate the AMH with CLBR per retrieval. AMH may thus prove to be a useful biomarker when counseling patients about what to expect from their treatment.

Fishing and fecundity: The impact of exploitation on the reproductive potential of a deep-water fish, orange roughy (Hoplostethus atlanticus)

To assess the impact of exploitation on the fecundity and reproductive potential of orange roughy, historic biological data from when exploitation began (1987–1992) is compared with a current day assessment (2010) of the eastern Tasmanian stock. Findings highlight that fecundity was negatively related to stock size (r2=0.95, F=80.11, P<0.05), with length standardised fecundity increasing from 41,145±1363 in 1992 to 59,236±1047 eggs in 2010. This density dependent increase suggests that from the onset of the fishery (1987) length standardised fecundity has increased by 73%. Modelling this increase based on the 2006 stock assessment showed that the female spawning stock biomass was at 19% of virgin levels, whereas the total reproductive potential was markedly higher and estimated to be at 32% of virgin levels. The biological mechanisms of this compensatory effect were also investigated and showed fecundity was not related to ovarian atresia levels but was positively related to body condition, liver condition and ovarian lipid levels. The implications of these findings for stock recovery and management are discussed and suggest that the stock is in a better position to recover from overexploitation than would be expected if only spawning stock biomass were considered

The status of public reporting of clinical outcomes in assisted reproductive technology

To assess the transparency of assisted reproductive technology (ART) surveillance reports published by the Centers for Disease Control and Prevention (CDC) and by the Society for Assisted Reproductive Technologies (SART). Retrospective analysis. Private clinical ART and research center. We analyzed ART data for the years 2005-2010, which were reported under federal mandate to the CDC (818,927 completed cycles) and voluntarily to SART (812,400 initiated cycles). None. Initiated cycles excluded from final outcome reporting were used to evaluate transparency. Only SART, but not CDC, reported initiated cycles, allowing analysis of excluded cycles. Excluded cycles increased significantly from 3.3% to 7.4% between 2005 and 2010. By 2010, 13/341 (3.8%) ART centers accounted for 50% of excluded cycles, representing an average of 37.3% of their cycles. These 13 clinics reported significantly better pregnancy and cancellations rates than national averages and collectively increased by 19.9% their share of U.S. ART cycles. Our data indicate decreasing transparency in public ART reporting in the United States, likely due to changes in practice and reporting patterns. A few clinics accounted for the majority of excluded cycles, leading to improved reported clinical outcomes and increasing market share. CDC and SART should ensure that all ART clinics publicly report the outcomes of all initiated cycles including embryo-banking cycles. ART surveillance and quality of care may be improved by prospectively tracking the total reproductive potential of each initiated cycle.

The Reproductive Aspect of Tropical Abalone (Haliotis asinina L.) in the Waters of Tanakeke Islands at South Sulawesi

The objective of research was to analyze the reproductive aspect of abalone ( Haliotis asinina L.) which included the beginning of gonad maturity, the peak of spawning season, the comparison of male and female abalone caught in the nature, the reproductive potential, and abalone fecundity. Research was located at the waters of Tanakeke Islands, Takalar District, South Sulawesi. Method of research was field survey. Sampling stations were determined based on the distribution of coral reef in the islands. Result of research indicated that male abalone reached the beginning of gonad maturity at shell length of 64.50 mm, while female abalone reached it at shell length of 64.09 mm. Abalone had spawned throughout year with two peaks of spawning season, precisely at the beginning of dry season and rainy season. The comparison of male and female abalone primes was 1:1. Abalone group with shell length of 60-70 mm contributed more than 70 % to the total reproductive potential of the population. Total fecundity of the tropical abalone at research was ranging from 255,900 to 756,200 egg s .

Can the Society for Assisted Reproductive Technology Clinic Outcome Reporting System (SART CORS) be used to accurately report clinic total reproductive potential (TRP)?

To assess whether total reproductive potential (TRP), the chance of a live birth from each fresh cycle (fresh cycle plus frozen transfers), could be calculated from the national Society for Assisted Reproductive Technology Clinic Outcome Reporting System (SART CORS) database and whether information not available in SART CORS resulted in significant changes to the TRP calculation. Retrospective study using SART CORS and clinic data. Three assisted reproductive technology clinics. Women undergoing ART. None. Two- and three-year TRPs for 2005 and 2006 were calculated according to patient age at cycle start by linking fresh to frozen cycles up to first live birth. Clinic records were used to adjust for (remove) frozen cycles that used more than one fresh cycle as a source of embryos and for any embryos donated to other patients or research or shipped to another facility before a live birth. TRP was higher than fresh per-cycle rates for most ages at all clinics, although accuracy was compromised when there were fewer than 20 cycles per category. Two- and 3-year TRPs differed in only 2 of 24 calculations. Adjusted TRPs differed less than three percentage points from unadjusted TRPs when volume was sufficient. Clinic TRP can be calculated from SART CORS. Data suggest that calculations of clinic TRP from the national dataset would be meaningful.

Can the Society for Assisted Reproductive Technology clinic outcomes reporting system (SART CORS) be used to accurately report clinic total reproductive potential (TRP)?

OBJECTIVE: Total Reproductive Potential (TRP) is the chance of at least one live birth (LB) from each egg harvest (fresh plus frozen transfers). This pilot study assessed the utility of SART CORS in calculating TRP. The extent to which adjustments for information not available in SART CORS (number of cycles thawed, embryos donated or shipped to other centers) resulted in changes in the TRP calculation was also determined.DESIGN: Retrospective analysis from both SART CORS and clinic records.MATERIALS AND METHODS: Clinic data from 2005-2008 were downloaded from SART CORS at 2 clinics: small rural (A), intermediate urban (B). Two and three year TRP were calculated for fresh cycles from 2005 or 2006 by linking fresh to frozen cycles for each patient over 2 or 3 years up to first LB. Clinic records were used to adjust for (remove pt from calculation) frozen cycles that used more than one fresh cycle as a source of embryos and for any embryos either donated to other patients or research, or shipped to another facility prior to a LB. Calculations were performed on the basis of patient age. IRB approval was obtained at each site.Tabled 12 Year TRP3 Year TRPFresh Cycle YearLB/Cycle (N)UnadjustedAdjustedUnadjustedAdjustedCLINIC A200531.5%(54)37.0%38.5%37.0%38.5%200642.9%(56)46.4%48.1%46.4%48.1%CLINIC B200547.9%(119)48.7%49.2%48.7%49.2%200650.8%(132)56.1%57.8%56.1%57.8%Age groups of 35-37, 38-40 and > 40 yo were also analyzed. Rates were not different in the 2 versus the 3 year TRP at either clinic. Adjusted rates differed by 1-2 percentage points. Open table in a new tab CONCLUSION: TRP can be calculated from SART CORS. Three year TRP did not add value over two year TRP. Addition of clinic data resulted in only minor adjustments to TRP suggesting that calculations of clinic TRP from the national dataset would be meaningful. OBJECTIVE: Total Reproductive Potential (TRP) is the chance of at least one live birth (LB) from each egg harvest (fresh plus frozen transfers). This pilot study assessed the utility of SART CORS in calculating TRP. The extent to which adjustments for information not available in SART CORS (number of cycles thawed, embryos donated or shipped to other centers) resulted in changes in the TRP calculation was also determined. DESIGN: Retrospective analysis from both SART CORS and clinic records. MATERIALS AND METHODS: Clinic data from 2005-2008 were downloaded from SART CORS at 2 clinics: small rural (A), intermediate urban (B). Two and three year TRP were calculated for fresh cycles from 2005 or 2006 by linking fresh to frozen cycles for each patient over 2 or 3 years up to first LB. Clinic records were used to adjust for (remove pt from calculation) frozen cycles that used more than one fresh cycle as a source of embryos and for any embryos either donated to other patients or research, or shipped to another facility prior to a LB. Calculations were performed on the basis of patient age. IRB approval was obtained at each site. Age groups of 35-37, 38-40 and > 40 yo were also analyzed. Rates were not different in the 2 versus the 3 year TRP at either clinic. Adjusted rates differed by 1-2 percentage points. CONCLUSION: TRP can be calculated from SART CORS. Three year TRP did not add value over two year TRP. Addition of clinic data resulted in only minor adjustments to TRP suggesting that calculations of clinic TRP from the national dataset would be meaningful.

Impact of male age on the outcome of assisted reproductive technology cycles using donor oocytes

This study assessed the influence of the age of the male partner on the outcome of oocyte donation cycles. A total of 408 couples participating in 519 consecutive anonymous oocyte donation cycles were examined. Main outcome measures were fertilization rate, embryo quality, clinical pregnancy, implantation, miscarriage and live birth rates, as well as the total reproductive potential, which estimates the outcome from fresh and cryopreserved-thawed embryo transfers. A total of 241 cycles resulted in clinical pregnancy (48.5% of transfers). The mean embryo score for transferred embryos (ESTE) was higher in cycles resulting in pregnancy (P=0.003). Semen volume (P<0.001), sperm motility (P<0.001) and fertilization rate (P=0.04) decreased significantly with advanced male age, which did not correlate with mean ESTE or implantation rate. Fertilization rate was the only predictor of ESTE (B=16.066, P=0.012), whereas inseminated/retrieved egg ratio was the only predictor of implantation rate (B=0.555, P=0.039). Pregnancy was only predicted by ESTE (Exp(B)=1.023, P<0.001), which also was the only predictor of live birth (Exp(B)=1.017, P=0.009). There was no predictor of miscarriage (47 cycles, 9.1%) identified. Although semen volume, sperm motility and fertilization rate decreased with advanced male age, embryo quality, clinical pregnancy, implantation, miscarriage and live birth rates were not affected.

Continuous quality improvement and assisted reproductive technology multiple gestations: some progress, some answers, more questions

The past decade has seen a fall in the number of embryos transferred accompanied by a reduction in the rate of higher order multiple pregnancies occurring from U.S. assisted reproductive technology (ART) cycles, which is temporally related to voluntary adherence to embryo transfer guidelines. The twin rate has remained relatively constant. The ability to continue the reduction in multiple pregnancies while maintaining advocacy positions for both patient couples and offspring will best occur with attention to scientific, sociologic, economic, and provider issues.

Reproductive biology and strategies of nine meloid beetles from Central Europe (Coleoptera: Meloidae)

The reproductive biology of meloid species from Central Europe is investigated by means of laboratory breeding experiments. They show that the total reproductive potential of meloids, with up to 40,000 eggs, largely exceeds prior data. Furthermore, the number of laid eggs strongly relates to the way by which the triungulins find their host. Clutch size correlates significantly with the size of the beetle, while egg size is independent of this. Both clutch size and egg size decrease with each oviposition. For some species, reproductive data are used to demonstrate how they have adapted to their habitat and to point out existing trade‐offs. Based on the obtained results and on an evaluation of the relevant literature, three types of reproductive strategy can be distinguished within the meloids: (1) very high reproductive rates of open field species with phoretic larvae; (2) average reproductive rates of forest populations of species with phoretic larvae and of species the larvae of which search the nests of their hosts actively; and (3) small to average reproductive rates of those species depositing their clutches in the immediate proximity of their hosts' nests.

O3 2 Cumulative delivery rate from a single oocyte harvest

Background. There is an urgent need to evaluate the cumulative delivery rate (DR) from a single oocyte harvest after both fresh and frozen embryo transfers (ET). Elective single embryo transfer (eSET) in combination with embryo cryopreservation has reduced the multiple delivery rate (MDR) compared with transfer of two embryos (DET), but the effect of frozen embryo transfers (FET) on cumulative DR and multiple DR has not been evaluated. In cases of imminent risk of ovarian hyperstimulation syndrome (OHSS) fresh ET is not performed and all embryos are cryopreserved. However, little is known about the DR after later frozen ETs from these OHSS cycles.The aim was to find out the total reproductive potential from a single oocyte harvest i.e. DR after fresh transfer and one or several frozen embryo transfers performed after an unsuccesful fresh transfer.The FET cycles performed during 1.3.1998–30.6.2004 were as follows: in the eSET group 907 FETs, in eDET 516 FETs and in no ET 161 FETs. In FET cycles one or two embryos were transferred in the eSET group. The mean number of embryos transferred in FET cycles was 1.5/1.6/1.5 respectively.Methods. All OPU‐cycles with ET and/or cryopreservation during 1998–2003. Type of transfer SET eSET* DET eSET + cryo eDET + cryo No ET + cryo Number 260 10 197 791 608 66 Mean age 33.6 36.2 34.5 32.3 34.1 31.9 mean n of cryo 0 0 0 6.4 3.4 12.4 embryos (range) (1–31) (1–24) (1–39) no cryopreservation due to poor quality of the other embryo Findings. Type of transfer SET eSET* DET eSET + cryo eDET + cryo No ET + cryo DR in fresh cycles 15.4% 20.0% 23.5% 29.0% 30.9% 0 MDR 2.5% 0 10.9% 1.3% 26.6% 0 DR in FET cycles 0 0 0 24.9% 18.8% 24.2% Cumulative DR 15.4% 20% 23.5% 52.6% 42.8% 54.5% Cumulative MDR 2.5% 0 10.9% 6.7% 25.0% 16.7% no cryopreservation due to poor quality of the other embryo Interpretation. Delivery rate in OPU cycles without cryopreservation was lower than in cycles with cryopreservation. In OPU cycles with cryopreservation the DR was not effected by the number of embryos transferred, but more twins were seen in cycles with eDET than with eSET (26.6% compared to 1.3%). The cumulative DR in the group with eSET in the fresh cycle exceeded that with eDET (52.6% vs 42.8%). In the eSET group only 6.7% of the deliveries were multiples compared to 25% in the group with eDET. Elective SET and cryopreservation is an effective tool not only to achieve a good cumulative delivery rate, but also to reduce multiple births. The possibility to cryopreserve all embryos in case of risk for OHSS is associated with good DR from frozen cycles, since at least one delivery has been achieved in 54.5% of these cycles.

Factors associated with an optimal pregnancy outcome in an oocyte donation program.

To identify donor and recipient variables that may have a significant impact on pregnancy outcome in order to optimize results of an oocyte donation program. Retrospective analysis through a Generalized Estimating Equation (GEE) approach to clustered and binary clustered data, linear mixed effects model, scatter plot smoothing functions, and receiving operator characteristics (ROC) curves. University-based center. None. Pregnancy and implantation rates. 257 donation and transfer cycles. Overall results were as follows: clinical pregnancy rate, 47%; implantation rate, 22%; abortion rate, 19%; and overall multiple pregnancy rate, 35%. The total reproductive potential was 60%. Implantation and pregnancy rates were not significantly related to any variable from donors or recipients. Abortion rate increased significantly with donors' increased basal serum LH. Pregnancy rate was significantly enhanced with improved embryo quality. In donors stimulated more than once, the pregnancy rate was 84%. Although no single or combined donor or recipient variable(s) could be identified as predictor(s) of pregnancy, the data suggest that donors < or = 33 years of age with basal cycle day 3 serum levels of FSH 4-8 IU/L, LH < 8 IU/L, and E2 < 70 pg/mL had an optimal outcome. Transfer of two selected embryos on day 3 yields a favorable pregnancy outcome while significantly decreasing the occurrence of multiple pregnancies. These policies, in addition to embryo cryopreservation, were associated with optimal pregnancy outcome in oocyte donation.

Vegetative and Reproductive Characteristics of Two Species of Batophora (Chlorophyta, Dasycladaceae) from Chetumal Bay, Quintana Roo, Mexico

Measurements on vegetative and reproductive structures from plants of the genus Batophora J. Agardh were made. Plants possessed spherical or ovoid gametophores, corresponding to Batophora oerstedi and B. occidentalis species, respectively. Both species coexist in the Chetumal Bay estuarine system. The species present different vegetative and reproductive characteristics compared to Batophora species from other parts of the world. The two species have different positive relationships between gametophore area and number of gametangia, and between reproductive thalli distance and number of gametophores. Gamete release was assayed applying two treatments to gametangia. Gamete release was significantly greater in B. occidentalis than in B. oerstedi. Both species showed the highest percentage of gamete release at between 100 and 150 μmol m−2 s−1 radiation. Reproductive potential per plant was estimated in July 1999 to be similar for both species; however, the difference in the number of reproductive plants per unit area of the Bay provided a greater total reproductive potential for B. occidentalis than for B. oerstedi. The reproductive differences may permit the two Batophora species to coexist in sympatry in Chetumal Bay. The reddish-brown pigmentation of gametophores exhibited by both species invalidates the diagnosis of B. occidentalis var. largoensis, a variety that has been separated on the basis of its color.

Potential Fecundity of Landlocked Sea Lamprey Larvae, Petromyzon marinus, with Typical and Atypical Gonads

Lampreys produce a fixed number of oocytes early in larval life, which represents their total reproductive potential or potential fecundity (Beamish and Thomas, 1983). In the landlocked sea lamprey of the Great Lakes, considerable oocyte atresia is thought to occur in postlarval stages (Hardisty, 1965b, 1969) such that actual fecundity may be appreciably less than potential fecundity (Applegate, 1950; Vladykov, 1951; Hardisty, 1965b). In the anadromous sea lamprey, the actual fecundity of adults and potential fecundity of larvae are similar (Hardisty, 1964). The much lower actual fecundity of the landlocked sea lamprey is thought to be directly related to the smaller adult body size (Hardisty, 1964; Beamish and Thomas, 1983). Sex differentiation in landlocked sea lamprey is typically complete when larvae reach total lengths of approximately 100 mm (Hardisty, 1965a, 1965b; Docker, 1992). Females are characterized by a large horseshoe-shaped ovary with fingerlike lobes, each containing two rows of oocytes greater than 60 xum in diameter (Hardisty, 1965b; Docker, 1992). Stromal tissue is scarce between the germinal elements, and there are few undifferentiated germ cells (Docker, 1992). Undifferentiated, or primordial, germ cells develop into oocytes through two growth phases. During the first growth phase, occurring in larvae 80-100 mm, cells increase synchronously in size (12-40 ,xm diameter) and are called first-stage oocytes (Hardisty, 1971). A second growth phase follows, with oocytes synchronously increasing in diameter to 80 ,Im. These second-stage oocytes are typically found in larvae greater than 110 mm total length (Hardisty, 1971). Males have an angular-shaped testis without lobes (Docker, 1992). Oocytes may be present but are few in number and usually less than 18 uxm in diameter (Docker, 1992). Stromal tissue is abundant, and clusters of germ cells are present (Hardisty, 1965b). Our recent observations (unpubl.) on landlocked sea lamprey larvae from the Great Lakes basin have revealed highly atypical patterns of gonadal development. Gonads of larvae with atypical gonads exhibit varying degrees of male and female characteristics. For example, gonad morphology may be similar to a female; however, primordial germ cells may be abundant. Oocytes may be asynchronous in their development, such that both firstand second-stage oocytes are present, or a high proportion of atretic oocytes may be present. The present study was undertaken to compare potential fecundity of typical and atypical larvae collected from streams tributary to the Great Lakes. The present study also compared current estimates of potential fecundity with those made several decades earlier (Hardisty, 1964) before larval abundance was regularly reduced in streams by chemical treatment.

Cryopreservation: a simplified method of evaluation.

A theoretical model is presented by which a true expression of pregnancy rate resulting from stimulated cycles can be calculated. This includes the transfer of both fresh and cryopreserved embryos. It is concluded that the total reproductive potential of a single cycle of stimulation can only be evaluated by including pregnancies arising from all fresh and frozen embryo transfers resulting from that cycle.

Mineral waters and hydrogeothermal resources in Bulgaria

Thermal mineral waters and extractable geothermal energy are an important and still underestimated natural wealth of Bulgaria. Their diversity is due to the complex geological structure, intense neotectonic activity, and the resulting complex character of meteoric water circulation. Reproductive hydrogeothermal systems with low-mineralized thermal waters of meteoric origin and resrvoir temperatures ranging between 30 and 100 (maximum 120) °C occur in the southern and north-eastern part of the country. Their total reproductive potential is estimated at 14–15 m3s−1. In the northern part (Moesian platform), regional hydrogeothermal reservoir with connate (marine) and mixed (marine and meteoric) mineral waters and brines are identified, the temperatures varying from 40 to 140 (maximum 150) °C. Huge resources of geothermal energy with commercial importance are accumulated in them. The hydrogeothermal wealth of Bulgaria provides as important basis for the development of balneological and multi-seasonal tourism, bottling industries, geothermal heating of buildings and greenhouses, aquaculture and other related activities.

Cryopreservation: the problem of evaluation.

A simple evaluatory formula for reporting pregnancy rates involving cryopreserved material has so far remained elusive. It is highly desirable to have a method which would allow not only an evaluation of cryotechnology per se, but also an evaluation of the role of cryotechnology in enhancing the total reproductive potential of a single cycle. In this paper, nine separate formulae are described which can be used for the evaluation of cryopreservation. It is concluded that none of the existing formulae used alone expresses the total potential of cryopreservation, and that while each formula provides information regarding some aspect of the role of cryopreservation, the most comprehensive evaluation requires the answer to five different equations. The other four formulae, while often used, are regarded as providing information which is unsubstantiated or does not allow complete evaluation.

Growth, reproductive performance and resource allocation of the herbaceous obligate seeder Gompholobium marginatum R. Br. (Fabaceae).

Perennial species have evolved several strategies to survive fire, with resprouters and seeders forming two major categories. Gompholobium marginatum is a herbaceous seeder legume occurring in the Western Australian jarrah (Eucalyptus marginata) forest which since 1961 has been subjected to burns every sixth year. Such frequent fires potentially endanger the survival of seeder species like G. marginatum, whose establishment and reproductive achievement is, therefore, the subject of this study. Sexual reproduction commenced in the second growing season and reached peak reproductive capacity (136 ovules per plant) and success (38 seeds per plant) in the 3rd year of growth. This ovule production represented more than 30% of the total reproductive potential (455 ovules per plant) recorded during the normally observed 6-year life span. Maturation of several generations of reproductive units occurred consecutively over 5 months with approximately 75% of initiated flowers setting fruit. Almost 30% of all initiated ovules, i.e. 132, matured to seeds during 6 years of undisturbed growth. P and N emerged as elements most limiting to plant growth and reproduction and proved to be the best indicators of reproductive costs. In contrast to many other seeder species, the phenorythmics of G. marginatum is compatible with a high fire frequency. While its intrinsically low growth rate may be viewed as a factor responsible for poor competitiveness with cohabiting understorey species, the high investment in early reproduction at the expense of vegetative growth can be interpreted as an evolved response to the opening of the habitat after fire. Whether the tendency to senescence of plants older than 3 years has its origin mainly in unfavorable environmental conditions (e.g. canopy closure, water or nutrient competition) or in a genetically induced decline in fecundity remains to be determined.