Communal Spawning in the Common Frog Rana temporaria– Egg Temperature and Predation Consequences

Females of the common frog, Rana temporaria, spawn synchronously at communal breeding sites, forming a communal egg mass of individual spawn clumps. A total of four spawning sites were studied. In the centre of the communal egg mass, daily maximum temperature was higher and minimum temperature lower than further out. Spawn clumps in the centre of the communal egg mass developed faster than single spawn clumps. In the centre of the egg masses, some spawn clumps suffered almost total egg mortality. This was probably the consequence of a cold spell with sub‐zero temperatures in combination with a tendency for low minimum temperatures in the centre. In a laboratory study, worm leeches, Erpobdella spp., fed readily on eggs of common frog, while horse leeches, Haemopis sanguisuga, hardly ate any eggs. At the spawning sites, most worm leeches were found in single spawn clumps, far from the communal egg mass. Females which spawned late, when most of the spawning was over, preferred to spawn in the centre of the communal egg mass. This suggests that there is a net advantage for eggs in spawn clumps laid in the centre.     

River regulation and fish larvae: variation through space and time

1. Patterns in abundance and distribution of larval fish in a heavily regulated and a mildly regulated Australian lowland river were compared over four breeding seasons to gain some insight into how river regulation affects fish populations.
2. Larvae from a total of 13 species from nine families were recorded from the two rivers. The mildly regulated Broken River supported twice as many species as the heavily regulated Campaspe River. The two rivers shared three introduced species but only two native species. The dominant species in the Campaspe was not found in the Broken River.
3. The two most abundant species in the Campaspe were classified as `opportunists'. They are small, short-lived species, which spawn for up to 9 months, encompassing extremes in temperature and flow. The extended spawning period may place a subset of larvae in optimal conditions for recruitment and is hypothesised as being the key to the success of these species.
4. Most species spawned each year, despite large interannual variation in flow and temperature conditions. Poor recruitment over several decades, rather than a failure to spawn, is considered the most likely explanation for differences in the larval fish faunas between the two rivers.
5. The highly regulated section of the Campaspe River downstream of the regulating impoundment is thought to provide suboptimal habitat conditions for larvae relative to the less regulated downstream sections.
6. The timing of occurrence of larvae of the dominant species varied by breeding season and may be the result of flexibility in the timing of spawning.     

Free fatty acids and sterols in the benthic spawn of aquatic molluscs, and their associated antimicrobial properties

The free lipid content of extracts from the spawn of 17 molluscs were analysed by gas chromatography/mass spectrometry. These extracts encompass the encapsulated embryos and extraembryonic structures from benthic gelatinous egg masses and leathery egg capsules covering five taxonomic groups. Palmitic and stearic acids were the dominant saturated fatty acids and oleic acid was the principal unsaturated acid found in the spawn. Cholesterol was the dominant sterol and the only sterol found in the spawn from every species. Extracts from gelatinous egg masses were found to contain proportionally more fatty acids compared to leathery egg capsules. No unsaturated fatty acids were found in any of the leathery egg capsules, including five neogastropods and one littorinimorph. Unsaturated fatty acids were present in all of the gelatinous egg masses, including two other littorinimorphs. This is the first study to demonstrate that unsaturated fatty acids possess significant bacteriolytic activity against four aquatic pathogens. Encapsulated Anaspidea egg masses contain relatively high concentrations of these unsaturated fatty acids and a lipid mixture modeled on these extracts was strongly bacteriolytic at concentrations down to 0.0001 mg/ml. By comparison, lipid mixtures modeled on extracts from the spawn of four other molluscan taxa with higher proportions of saturated fatty acid and cholesterol, were only partially active against some of the bacteria at 0.1 mg/ml. Thus, unsaturated fatty acids could explain the antimicrobial activity previously reported in lipid extracts of some, but not most, molluscan spawn. MDS ordination and ANOSIM revealed significant taxonomic differences in the composition of free lipids from molluscan spawn, suggesting that lipid analyses may be useful in future systematic studies of the Mollusca.     

Allopaternal care in the tessellated darter,Etheostoma olmstedi (Pisces: Percidae)

Synopsis Large male tessellated darters, Etheostoma olmstedi, defend flat-bottomed rocks, the undersides of which serve as spawning substrates. Because females attach eggs directly onto bare stone, a spawning bout necessarily decreases the surface area available for further breeding at a nest. In apparent response to the female preference of ovipositing on rocks with the most bare surface, fathers abandon nests with their attached offspring to search for rocks with more uncovered surface. Egg abandonment also results after roving fathers intercept and spawn with ripe females and remain at a different rock to care for a new clutch. In essence, large males appear to maximize the number of eggs they fertilize by sequentially monopolizing breeding patches that are temporarily most desirable to females. The costs to a father of abandoning his eggs appear to be low for two reasons: (1) non-territorial males, created by a scarcity of suitable rocks, readily occupy vacant nests, and clean and aerate the abandoned eggs; and (2) after water hardening, eggs are less vulnerable to cannibalism. The maintenance of eggs by nonparental males may be both incidental to scrubbing the ceiling for their own breeding and adaptive in that viable eggs stimulate females to spawn; neither would appear to involve parental investment costs. Thus, allopaternal care in the tessellated darter may have evolved because it is performed in the selfish pursuit of spawning opportunities while entailing little, if any, of the costs normally subsumed within parental investment.     

Comprehensive Transcriptome Analysis of Gonadal and Somatic Tissues for Identification of Sex-Related Genes in the Largemouth Bass Micropterus salmoides

Marine Biotechnology - Largemouth bass (Micropterus salmoides) is an economically important fish. It can spawn many times during a breeding season, and there are no obvious morphological...     

Not All Offspring Are Created Equal: Variation in Larval Characteristics in a Serially Spawning Damselfish

The way organisms allocate their resources to growth and reproduction are key attributes differentiating life histories. Many organisms spawn multiple times in a breeding season, but few studies have investigated the impact of serial spawning on reproductive allocation. This study investigated whether resource allocation was influenced by parental characteristics and prior spawning history in a serial spawning tropical damselfish (Pomacentrus amboinensis). The offspring attributes of isolated parents of known characteristics were monitored over a 6-week breeding period in the field. Smaller females produced larvae of longer length and larger energy reserves at hatching. This finding is contrary to several other studies that found larger females produce offspring of greater quality. We found that resource allocation in the form of reproductive output was not influenced by the number of spawning events within the breeding season, with larger females producing the greatest number of offspring. Larval characteristics changed as spawning progressed. There was a general decline in length of larvae produced, with an increase in the size of the larval yolk-sac, for all females regardless of size as spawning progressed. This trend was accentuated by the smallest females. This change in larval characteristics may reflect a parental ability to forecast unfavourable conditions as the season progresses or a mechanism to ensure that some will survive no matter what conditions they encounter. This study highlights the importance of accounting for temporal changes in reproductive allocation in studies of reproductive trade-offs and investigations into the importance of parental effects.     

Effect of liquid mycelial culture used as a spawn on sawdust cultivation of shiitake (Lentinula edodes)

Mycelium of shiitake (Lentinula edodes) was cultured continuously in liquid medium. The liquid culture was carried out for the production of liquid spawn in the cultivation of this mushroom on synthetic sawdust substrate, and its performance was compared with that of the solid spawn. The initial colonization in culture bags was faster with the solid spawn than with the liquid spawn, but after this stage CO₂ production was higher with the liquid spawn than with the solid spawn. For harvesting sufficient amount of good quality mushrooms, 120 d of incubation in bags was needed with the solid spawn, but this was reduced to 90 d for the sawdust blocks using liquid spawn of less than 50 d old. If continuous culture of the liquid spawn was prolonged over 50 d, immature fruit-bodies or their initials formed during the period of bag incubation. The solid subcultures of the liquid spawns retained the fruiting characteristics acquired in the liquid culture. Liquid culture could be a useful tool for breeding of mushrooms.     

Are simple environmental indicators of food web dynamics reliable: Exploring the kittiwake–temperature relationship

This study examined the inter-relationships between kittiwake breeding success and sandeel abundance, Calanus copepods, chlorophyll and temperature. The validity of past proxies of sandeel prey (Calanus and temperature) suggested in the literature was also examined. Winter temperature was not found to be a reliable indicator of the abundance of sandeel or lower trophic levels, although the present study did support past evidence for a dependence of kittiwake breeding success on local sandeel abundance as, with the exception of two years, there was a linear relationship with log age-0 sandeel abundance. The abundance of sandeel was positively linked to the dates of predicted peak egg abundance in C. finmarchicus and C. helgolandicus. This supported earlier evidence that the match with prey timing is important to sandeel recruitment. Neither Calanus species was associated with temperature in the February to March period nor in the April–May period, which may explain the lack of a temperature effect that propagates through the trophic levels. Consequently, although kittiwake breeding success appears to show some sensitivity and specificity to changes in their prey, this responsiveness was not found to extend to the lowest trophic level (Calanus abundance) or to temperature. As such kittiwake breeding success was not a reliable indicator of climate-driven changes in the local food web.     

Postmetamorphic dispersal and recruitment of first breeders in a Bufo calamita metapopulation

The migratory capacity of metamorphs and their later integration into local breeding populations was studied in a Bufo calamita metapopulation inhabiting the northern Rhineland, Germany (1991–1994). A new tagging method allowed unequivocal distinction among metamorphs (n = 1,709), which originated either from the spring-breeding cohort in 1991 and 1992 or from the summer-breeding cohort in 1991. The life history of batch-marked individuals was followed until adulthood, focusing on postmetamorphic dispersal, choice of breeding locality and timing of adult reproduction. Almost all metamorphs left the patches used for breeding within a few weeks after emergence. They were found at about the same density in all favourable microhabitats in a radius of up to 2 km around their native patch. This demonstrates that even small toadlets (6–11 mm snout-to-vent length) migrate distances of several hundred metres within a short time and that they significantly help prevent local extinction in sink populations (rescue effect). Recaptures of reproductive adults originating from tagged metamorphs were limited to males belonging to the 1997 spring and summer cohorts. The absence of recaptured females was probably due to their greater vagility and later sexual maturation. First-breeding males (2 years old) without exception joined the breeding cohort from which they originated: early breeders originated from spawn of the spring cohort, mid-summer breeders from spawn of the summer cohort. This result is in accordance with the hypothesis that the integration of first breeders to a specific breeding cohort is genetically controlled in central European natterjacks. The exchange of individuals between different cohorts in the same patch is considerably less than the migratory exchange between the same breeding cohorts among local populations, as predicted from the allozyme data. Received: 28 October1996 / Accepted: 4 June 1997     

Spawning in Littorina littorea (L.) (Gastropoda: Prosobranchiata)

Data on the amount of ‘spawn’ of Littorina littorea (L.) held in the laboratory for varying periods of time during the breeding season have been used for an analysis of the pattern of egg production. It has been shown that there is good evidence for seasonality of breeding in the population studied, and that there are both diurnal and longer time scale fluctuations in spawn output. There is a strong indication of a lunar/tidal rhythm in spawning, but this is not conclusively proved. A limited number of experiments have failed to show any effect of temperature fluctuations on spawning, and there is no evidence of the entrainment of a rhythm when the snails are brought into the laboratory.     

人工饲料对稀有Ju鲫繁殖影响的研究

静水缸中稀有Ju鲫240天养殖试验显示,A型人工饲料的每对亲鱼产卵次数汉源种群和彭州种群分别为15.25和13.75次,相近于水蚯蚓为饲料的12次和14.5次;A型人工饲料产卵间隔天数分别为15.98天和17.46天,相近于水蚯蚓为饲料的20.86天和16.56天。循环水缸中稀有Ju鲫105天养殖试验显示,A型人工饲料的每对亲鱼产卵次数为12次,低于水蝗蚓为饲料的21.5次;产卵间隔天数为8.75天,长于水蚯蚓为饲料的4.88天。因此,用人工饲料可以实现静水缸和循环水缸中稀有Ju鲫的繁殖。静水缸5种饲料个体每次产卵量有显著差异（P＜0.05）,而鱼卵孵化率没有显著差异（P＞0.05）。A和B型饲料产卵量与水蚯蚓接近。循环水缸4种饲料个体每次卵量和鱼孵化率均有显著差异（P＜0.05）。     

Observations on the breeding habits of Clarias gariepinus (Burchell)

Clarias gariepinus (Burchell) can be stimulated to spawn in aquaria by hormonal treatment and the breeding habits could be observed. After pre-spawning activities such as the raising of dorsal fins and chasing of the female, the male folds around the head of the female and small batches of eggs are laid, followed by some gas bubbles. Eggs are distributed by the female over a wide area. This behaviour agrees with field observations. The final stimulant to spawning under natural conditions is thought to be a substance called petrichor dissolved in flood waters that have run over dry ground.     

Anther extrusion and plant height are associated with Type I resistance to Fusarium head blight in bread wheat line ‘Shanghai-3/Catbird’

Fusarium head blight (FHB) is a destructive wheat disease of global importance. Resistance breeding depends heavily on the Fhb1 gene. The CIMMYT line Shanghai-3/Catbird (SHA3/CBRD) is a promising source without this gene. A recombinant inbred line (RIL) population from the cross of SHA3/CBRD with the German spring wheat cv. Naxos was evaluated for FHB resistance and related traits in field trials using spray and spawn inoculation in Norway and point inoculation in China. After spray and spawn inoculation, FHB severities were negatively correlated with both anther extrusion (AE) and plant height (PH). The QTL analysis showed that the Rht-B1b dwarfing allele co-localized with a QTL for low AE and increased susceptibility after spawn and spray inoculation. In general, SHA3/CBRD contributed most of the favorable alleles for resistance to severity after spray and spawn inoculation, while Naxos contributed more favorable alleles for reduction in FDK and DON content and resistance to severity after point inoculation. SHA3/CBRD contributed a major resistance QTL close to the centromere on 2DLc affecting FHB severity and DON after all inoculation methods. This QTL was also associated with AE and PH, with high AE and tall alleles contributed by SHA3/CBRD. Several QTL for AE and PH were detected, and low AE or reduced PH was always associated with increased susceptibility after spawn and spray inoculation. Most of the other minor FHB resistance QTL from SHA3/CBRD were associated with AE or PH, while the QTL from Naxos were mostly not. After point inoculation, no other QTL for FHB traits was associated with AE or PH, except the 2DLc QTL which was common across all inoculation methods. Marker-assisted selection based on the 2DLc QTL from SHA3/CBRD combined with phenotypic selection for AE is recommended for resistance breeding based on this valuable source of resistance.     

Testis size depends on social status and the presence of male helpers in the cooperatively breeding cichlid Julidochromis ornatus

Cooperatively breeding animals, in which helpers may participatein reproduction with dominant breeders, are ideal species forexamining intraspecific variation in testis size because theyoften exhibit both monogamous breeding (low risk of sperm competition)and polyandrous breeding (high risk) within a population. However,little is known about testis investment as a result of spermcompetition in these animals. The substrate-brooding cichlidfish Julidochromis ornatus has a cooperatively breeding system,in which some males mate monogamously and other males reproduceas dominant breeders or helpers within cooperatively breedinggroups, in which male helpers frequently sire young. We examinedthe relationship between testis investment and male social statusin relation to the risk of sperm competition. As predicted fromsperm competition models, in groups with male helpers, boththe male breeders and the male helpers invested more in testesmass, compared to breeding males without male helpers. We alsofound a positive relationship between the testes mass of malebreeders and their male helpers, suggesting that males increasetheir investment in reproductive capability under the risk ofsperm competition. Sperm competition models also predict thatlarger testes are associated with increased siring success.Our paternity analysis supported this prediction; we found apositive relationship between testis investment by male helpersand the number of offspring they sired.     

Prediction of rates of inbreeding in populations selected on best linear unbiased prediction of breeding value

Predictions for the rate of inbreeding (DeltaF) in populations with discrete generations undergoing selection on best linear unbiased prediction (BLUP) of breeding value were developed. Predictions were based on the concept of long-term genetic contributions using a recently established relationship between expected contributions and rates of inbreeding and a known procedure for predicting expected contributions. Expected contributions of individuals were predicted using a linear model, u(i)(()(x)()) = alpha + betas(i), where s(i) denotes the selective advantage as a deviation from the contemporaries, which was the sum of the breeding values of the individual and the breeding values of its mates. The accuracy of predictions was evaluated for a wide range of population and genetic parameters. Accurate predictions were obtained for populations of 5-20 sires. For 20-80 sires, systematic underprediction of on average 11% was found, which was shown to be related to the goodness of fit of the linear model. Using simulation, it was shown that a quadratic model would give accurate predictions for those schemes. Furthermore, it was shown that, contrary to random selection, DeltaF less than halved when the number of parents was doubled and that in specific cases DeltaF may increase with the number of dams.     

Semelparous or iteroparous: resource allocation tactics in the ayu, an osmeroid fish

Ayu Plecoglossus altivelis is an annual osmeroid fish with a single breeding season. Its reproductive mode tends to vary such that large females spawn once, while small females spawn twice with an interval of some 2 weeks. The hypothesis was examined that certain female reproductive modes are governed by adequate resource allocation according to maternal body size, to maximize lifetime reproductive success. A series of rearing experiments revealed that immediately before spawning, larger females had relatively higher diversion from the soma and higher investment into the gonad, in contrast to smaller females which maintained higher protein synthetic activity for further reproduction. It was concluded that the extant plasticity in the reproductive mode that occurred in P. altivelis was an outcome of different tactics on the semelparity-iteroparity continuum rather than maladaptive deviation from the optimum.     

Age and size-dependent variation in the seasonal timing and probability of reproduction among mature female pumpkinseed,Lepomis gibbosus

Synopsis In this study, we used pumpkinseed,Lepomis gibbosus, populations in two east-central Ontario lakes to test for age and size-dependent effects on the probability and timing of reproduction of mature females. Pumpkinseed body size characteristics differed in the two lakes; Little Round Lake harbours a stunted population and Beloporine Lake does not. Age-class distribution of mature females was determined by a maturity assessment on fish collected just prior to spawning and at the mid-spawning period, combined with an early-season capture-mark-recapture survey. Spawning females were collected throughout the breeding season to assess age and size-related temporal trends, and to compare their age and size distribution with that of mature females at large. The proportion of age 2 females in Little Round Lake that actually spawned was considerably lower than the proportion of mature age 2 females at large. Furthermore, age 2 females that spawned in this lake did not do so until late in the breeding season. In contrast, the proportion of young/small females spawning in Beloporine Lake was comparable to the proportion of young/small mature females at large, and both small and large females spawned throughout the breeding season. Small mature females in Little Round Lake may have had no other option but to spawn late in the season because of their poor body condition. In Beloporine Lake, condition factor early in the breeding season in age 2–4 females was higher than that of Little Round Lake females, suggesting that limited energy reserves in the spring may have prevented young Little Round Lake females from early spawning. Our results show that the likelihood and timing of reproduction are both age and size-dependent in some populations. Small individuals that delay seasonal maturation and spawn late in the summer probably contribute little to the population due to the restricted growth and reduced overwinter survival of their progeny.To whom correspondence should be addressed     

Assessing the cost of helping: the roles of body condition and oxidative balance in the Seychelles warbler (Acrocephalus sechellensis)

In cooperatively breeding species, helping close relatives may provide important fitness benefits. However, helping can be energetically expensive and may result in increased generation of reactive oxygen species. Consequently, an oxidant/antioxidant imbalance can lead to higher oxidative stress susceptibility. Given the potential costs of helping, it may be that only individuals with a sufficiently good body condition and/or stable oxidative balance can afford to help. Knowledge about relationships between social status and oxidative balance in cooperatively breeding systems is still limited. Studying these relationships is important for understanding the costs of helping and physiological pressures of reproduction. Here we evaluate the relationship between helping behaviour, body condition and oxidative balance in a wild population of the cooperatively breeding Seychelles warbler (Acrocephalus sechellensis). In this species, some subordinate individuals help dominant birds with the rearing of young, while others refrain from any assistance. We assessed body condition and oxidative parameters of birds of different social status caught during different breeding stages. We found that, prior to breeding, female subordinates that did not subsequently help (non-helpers) had significantly lower body condition and higher ROMs (reactive oxygen metabolites) than helpers and dominants. During the later stages of breeding, body condition was low in dominants and helpers, but high in non-helpers. Differences in oxidative balance between individuals of different social status were found only during nest care: Dominant males occupied with guarding behaviours tended to have relatively high oxidative stress susceptibility. Furthermore, dominant and helper females showed elevated antioxidant capacity (measured as OXY) in the weeks just prior to egg-laying, possibly representing a change in their reproductive physiology. The results imply that an individuals' oxidative balance may be influenced by factors related to reproduction, which can differ with sex and--within cooperative breeding systems--social status.     

A comparison of the fecundities of two species of toad (Bufo bufo and B. calamita) from different habitat types in Britain

The fecundities of Natterjack toads, Bufo calamita , on a Cumbrian dune system and a relict heathland site in Hampshire were compared and contrasted with the fecundity of Common toads, B. bufo , on the Cumbrian dunes. For both species, fecundity was positively correlated with length, while in B. calamita length was also correlated with size of eggs produced, and age of the female. Bufo calamita was found to invest more energy exponentially in egg production with increasing length, and therefore age. This species also laid more than twice as many eggs as comparably-sized female B. bufo , and some probably produced two clutches of spawn per year in southern England. The enhanced fecundity of the species was believed to be an adaptation to living in areas with unpredictable spawning sites. Small female B. bufo on the dunes appeared to put more energy into egg production when small than individuals of the same species on other habitat types in Britain, possibly as a result of reduced life expectancy on the dune habitat. There was a link between old age and the production of non-viable spawn in B. calamita , and males of this species which spawned at the end of the prolonged breeding season were found to have reduced fertilization efficiency when spawning on consecutive evenings.