Mature Females Research Articles

Reproductive features of data-deficient yellowfin snapper, Lutjanus xanthopinnis (Actinopterygii: Eupercaria: Lutjanidae), from east-coast of Peninsular Malaysia: Implications for sustainable fisheries management

Understanding the reproductive biology of fishes is crucial to making accurate and scientifically sound recommendations for fisheries management. The presently reported study is the first to report the reproductive characteristics of the data-deficient and recently described yellowfin snapper, Lutjanus xanthopinnis Iwatsuki, Tanaka et Allen, 2015, collected from the eastern South China Sea, Malaysia. A total of 572 fish specimens were sampled monthly from March 2022 to April 2023 using a gillnet and a trawl net. Subsequently, these specimens were measured and weighed. Their total length (TL) ranged from 15.3 to 26.8 cm (19.25 ± 2.04 cm; mean ± SD). Their body weight (WB) ranged from 53.5 g to 279.7 g (114.5 ± 40.3 g; mean ± SD). For the reproductive biology study, the following parameters were determined: the sex ratio, gonadosomatic index (GSI), hepatosomatic index (HSI), spawning period, fecundity, condition factor (K), length at maturity, and the gonadal maturity stages. In the sex ratio, males (M) were significantly dominant over females (F) (M:F = 1:0.75) (χ2 = 11.18). Consequently, the monthly mean GSI of pooled sex revealed a consistent trend from January to August, indicating spawning seasons with peak periods in March and April. The batch fecundity of 67 mature females (16.0–25.2 cm TL; 64.5– 279.3 g W), was determined to range from 16 405 to 94 357 oocytes. The fecundity increased with gonad weight in contrast to weight and length. The length at first maturity of females and males was 14.53 and 20.56 cm, respectively. Females matured earlier than males. Macroscopic and histological examination of gonads revealed monthly variation in the ratio of gonad stages for males and females. This study offers crucial data on the reproductive biology of L. xanthopinnis, which will help with sustainable fishery management in this area and can be used as a reference for the management of similar fish populations in other regions of the world.

Impacts of horticultural environments on Rhinella arenarum (Anura, Bufonidae) populations: exploring genocytotoxic damage and demographic life history traits.

Horticulture poses a significant ecological risk, as agrochemicals are applied more frequently and in larger quantities per unit of production compared to extensive crop fields. The native amphibian Rhinella arenarum serves as a reliable bioindicator of environmental health. This study aimed to assess genocytotoxic damage and demographic life history traits of R. arenarum inhabiting horticultural environments. Sampling was conducted in suburban sites in central Argentina: H1 and H2 (sites associated with horticultural activity) and a reference site, RS. Environmental parameters were recorded, and the frequency of micronuclei (Mn), nuclear abnormalities (ENA), and indicators of cytotoxic damage were determined in tadpoles and adults. Demographic variables (age at maturity, longevity, potential reproductive lifespan, size at maturity, modal lifespan) were calculated. The highest nitrate and phosphate values, along with low dissolved oxygen values, were recorded at sites H1 and H2. Organisms inhabiting horticultural environments exhibited higher frequencies of Mn and ENA, surpassing those recorded in previous studies on tadpoles from sites with extensive crop production. Size at maturity and age at maturity of females, as well as size at maturity, longevity, mean age, and mean adult SVL of males, were lower in horticultural sites. The results support the hypothesis that anuran populations inhabiting horticultural environments demonstrate a diminished health status attributed to subpar environmental quality. Monitoring endpoints at different biological levels provides information on the ecotoxicological risk for amphibians and human populations inhabiting nearby areas.

CRISPR-mediated germline mutagenesis for genetic sterilization of Anopheles gambiae males.

Rapid spread of insecticide resistance among anopheline mosquitoes threatens malaria elimination efforts, necessitating development of alternative vector control technologies. Sterile insect technique (SIT) has been successfully implemented in multiple insect pests to suppress field populations by the release of large numbers of sterile males, yet it has proven difficult to adapt to Anopheles vectors. Here we outline adaptation of a CRISPR-based genetic sterilization system to selectively ablate male sperm cells in the malaria mosquito Anopheles gambiae. We achieve robust mosaic biallelic mutagenesis of zero population growth (zpg, a gene essential for differentiation of germ cells) in F1 individuals after intercrossing a germline-expressing Cas9 transgenic line to a line expressing zpg-targeting gRNAs. Approximately 95% of mutagenized males display complete genetic sterilization, and cause similarly high levels of infertility in their female mates. Using a fluorescence reporter that allows detection of the germline leads to a 100% accurate selection of spermless males, improving the system. These males cause a striking reduction in mosquito population size when released at field-like frequencies in competition cages against wild type males. These findings demonstrate that such a genetic system could be adopted for SIT against important malaria vectors.

Developmental remodeling repurposes larval neurons for sexual behaviors in adult Drosophila

Most larval neurons in Drosophila are repurposed during metamorphosis for functions in adult life, but their contribution to the neural circuits for sexually dimorphic behaviors is unknown. Here, we identify two interneurons in the nerve cord of adult Drosophila females that control ovipositor extrusion, a courtship rejection behavior performed by mated females. We show that these two neurons are present in the nerve cord of larvae as mature, sexually monomorphic interneurons. During pupal development, they acquire the expression of the sexual differentiation gene, doublesex; undergo doublesex-dependent programmed cell death in males; and are remodeled in females for functions in female mating behavior. Our results demonstrate that the neural circuits for courtship in Drosophila are built in part using neurons that are sexually reprogrammed from former sex-shared activities in larval life.

New Insights on the Male and Female Reproductive Organs of Centrorhynchus globocaudatus (Acanthocephala), Intestinal Parasite of Birds of Prey.

Acanthocephalans are dioecious parasites that gain sexual maturity in the alimentary canal of their definitive hosts (gnathostome vertebrates). This initial survey by light and transmission electron microscopy was conducted on the functional organization of the ovarian balls and uterine bell in mature females and on Saefftigen's pouch and the copulatory bursa in males. We studied these structures via the example of Centrorhynchus globocaudatus (Palaeacanthocephala) in Falco tinnunculus and Buteo buteo, from the Province of Ferrara (Northern Italy). Our study confirms that the ovarian balls have surface microvilli and consist of a multinucleate supporting syncytium and a cellular region with oogonial syncytium, single germ cells, zygotes, and shelled eggs. Germ cells are embedded in the supporting syncytium. The ultrastructural features of these components and data on fertilization, shell formation, and release from the ovarian ball, alongside insights into the likely egg sorting function of the uterine bell, are provided. We also present light and electron microscopy observations of Saefftigen's pouch and a suggestion regarding its hydrostatic functioning in the eversion of the copulatory bursa.

Gametic selection favours polyandry and selfing.

Competition among pollen or sperm (gametic selection) can cause evolution. Mating systems shape the intensity of gametic selection by determining the competitors involved, which can in turn cause the mating system itself to evolve. We model the bidirectional relationship between gametic selection and mating systems, focusing on variation in female mating frequency (monandry-polyandry) and self-fertilisation (selfing-outcrossing). First, we find that monandry and selfing both reduce the efficiency of gametic selection in removing deleterious alleles. This means that selfing can increase mutation load, in contrast to cases without gametic selection where selfing purges deleterious mutations and decreases mutation load. Second, we explore how mating systems evolve via their effect on gametic selection. By manipulating gametic selection, polyandry can evolve to increase the fitness of the offspring produced. However, this indirect advantage of post-copulatory sexual selection is weak and is likely to be overwhelmed by any direct fitness effects of mating systems. Nevertheless, gametic selection can be potentially decisive for selfing evolution because it significantly reduces inbreeding depression, which favours selfing. Thus, the presence of gametic selection could be a key factor driving selfing evolution.

The Effects of Different Feed Ration Levels on Growth, Welfare Rating, and Early Maturation in Juvenile Atlantic Salmon (Salmo salar)

To investigate the possible effect of different feed ration levels on the growth, welfare, and early maturation of juvenile Atlantic salmon, 450 salmon parr with a mean (±standard error) initial weight of 51.6 g (±0.8) were reared in triplicate under three different feed ration levels for five months. The control group (100r) was fed every day, the 50r group was fed every other day, and the 33r group was fed every third day. In every group, 75 fish (half of the group) were individually tagged for monitoring of growth. The number of fin wounds was used as the welfare indicator, and to inspect the development of maturation, all fish were euthanized, and development of the gonads was monitored by visual inspection at the termination of the trial. The control group (100r) showed a significantly higher specific growth rate (0.90% day−1) compared to the lower fed groups (50r, 0.67% day−1 and 33r, 0.49% day−1); however, the growth difference was 21–24% less than expected solely on the difference in the amount of feed given to each group. The 100r group showed the highest welfare rating, and the 33r group the lowest possible, indicating more aggressive behaviour and fin biting due to feed restriction in the 33r group. No difference (p > 0.45) was found in the development of maturation in females, but the combined numbers of males in maturity stages 2–5 showed an overall trend towards slower maturation in the 33r group compared to the 100r group. Although the present findings on the development of sexual maturation were subtle due to the limited time frame of the trial, the findings offer a foundation for future investigation into the relationship between the feed ration level and the development of sexual maturation in the rearing of juvenile Atlantic salmon.

Initial investigations into the production of triploid sunshine bass using temperature shock

AbstractObjectiveThe sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) is an important food fish raised in U.S. aquaculture. Spawning is performed by manually stripping and fertilizing White Bass eggs with Striped Bass sperm. Embryos hatch in approximately 48 h. Mature sunshine bass females can become fertile and produce viable eggs, which is problematic in commercial food‐fish production; therefore, triploid fish are desired.MethodsThe present nonreplicated study incorporated three warm and three cold temperature shocks, along with three postfertilization initiation times and three exposure times for each temperature, during initial stages of incubation to induce triploidy. After exposure to temperature shocks, fertilized eggs were incubated in experimental hatching systems. The best performing cold and warm temperatures and times (and an ambient diploid control) were then used to incubate fertilized eggs in a commercial‐scale trial using standard industry practices with a single batch of eggs. Larvae were stocked at about 185,000 larvae/ha (75,000 larvae/acre) in newly filled and fertilized ponds. Fry were sampled weekly and harvested at 30 days.ResultThere were 15 survivors from the pond containing fish derived from cold‐shocked fertilized eggs; these individuals were tested via Coulter Counter, and no triploids were detected. Testing of 50 survivors from the pond containing fish derived from warm‐shocked fertilized eggs indicated that 14% were triploid.ConclusionTherefore, initial trials indicate that warm temperature shock is preferable to cold shock for inducing a greater percentage of triploid sunshine bass.

Mean size at sexual maturity of female Cynoscion reticulatus along the Pacific coast off Mexico

Drums and croakers (Sciaenidae) are important to the species composition of coastal catches in the Gulf of California, Mexico. Among these species, the striped corvina (Cynoscion reticulatus) stands out because of its high fishery potential, high demand, and increased market value. The striped croaker has been under constant fishing pressure over the past 20 years. Still, there needs to be current biological information or reference points to allow the establishment of management measures for fisheries. The objective of the present study was to estimate the mean standard length at sexual maturity (SL50) of females using various models and to suggest a minimum catch size (MCS) for C. reticulatus off the southern coast of Sinaloa. Monthly samplings of coastal fishery landings were done from December 2020 to December 2021 on the south coast of Sinaloa. The SL50 was evaluated based on 3 candidate models (Gompertz, Lysack, and White) through a binomial approach. Confidence intervals for SL50 were estimated using likelihood profiles and contours, and Akaike’s information criterion (AIC) was used to select the best model. A total of 284 individuals were examined, of which 131 were used in calculations. White’s model was the most adequate; however, based on AIC weights, all 3 models performed similarly, and SL50 (24.48 cm; C.I. 95% 12.9–70 36.0 cm) was estimated as their average. As a management measure, we propose a precautionary MCS of 36 cm SL for C. reticulatus off southern Sinaloa.

Daily activity rhythm of the African stingless bee Hypotrigona gribodoi (Hymenoptera: Meliponini) in the dry season, with notes on nest structure and colony composition

We studied 18 colonies of Hypotrigona gribodoi (Magretti) nesting in the tubing of a disused horticultural sprinkler system during the late dry season in Ghana, West Africa. Flight activity began around dawn (about 06:00), rising to a peak in the half-hour starting 07:30 and gradually declining to end around dusk (about 18:00). Bees returning with pollen showed a more extended peak from 07:30 to 09:00. Dissection of 18 nests showed a mean inner volume of 466.5 ml, while 17 active colonies had a mean number of 851 adults. Colony size is positively correlated with nest size. It is likewise positively correlated with the fraction of fully mature adult females. Several nests had branching entrance tubes with an angle of roughly 30⁰ between branches. In each of three such nests studied, there was a marked division in the use of the two branches, such that one served mainly as an exit and the other as an entrance.

Identification of candidate genes associated with host-seeking behavior in the parasitoid wasp Diachasmimorpha longicaudata

BackgroundDiachasmimorpha longicaudata is a hymenopteran fruit fly endoparasitoid. Females of this species find their hosts for oviposition by using complex sensorial mechanisms in response to physical and chemical stimuli associated with the host and host habitat. Ecological and behavioral aspects related to host-seeking behavior for oviposition have been extensively studied in D. longicaudata, including the identification of volatile organic compounds acting as attractants to females. In this sense, molecular mechanisms of chemoreception have been explored in this species, including a preliminary characterization of odorant-binding proteins (OBPs), chemosensory proteins (CSPs) and odorant receptors (ORs), among other proteins. Functional assays on OBP and CSP have been conducted as a first approach to identify molecular mechanisms associated with the female host-seeking behavior for oviposition. The aims of the present study were to identify the D. longicaudata sensory gene repertoire expressed in the antenna of sexually mature and mated individuals of both sexes, and subsequently, characterize transcripts differentially expressed in the antennae of females to identify candidate genes associated with the female host-seeking behavior for oviposition.ResultsA total of 33,745 predicted protein-coding sequences were obtained from a de novo antennal transcriptome assembly. Ten sensory-related gene families were annotated as follows: 222 ORs, 44 ionotropic receptors (IRs), 25 gustatory receptors (GRs), 9 CSPs, 13 OBPs, 2 ammonium transporters (AMTs), 8 pickpocket (PPKs) receptors, 16 transient receptor potential (TRP) channels, 12 CD36/SNMPs and 3 Niemann-Pick type C2 like proteins (NPC2-like). The differential expression analysis revealed 237 and 151 transcripts up- and downregulated, respectively, between the female and male antennae. Ninety-seven differentially expressed transcripts corresponded to sensory-related genes including 88 transcripts being upregulated (87 ORs and one TRP) and nine downregulated (six ORs, two CSPs and one OBP) in females compared to males.ConclusionsThe sensory gene repertoire of D. longicaudata was similar to that of other taxonomically related parasitoid wasps. We identified a high number of ORs upregulated in the female antenna. These results may indicate that this gene family has a central role in the chemoreception of sexually mature females during the search for hosts and host habitats for reproductive purposes.

The reproductive biology of Ellochelon vaigiensis from the Vietnamese Mekong Delta.

The Squaretail mullet, Ellochelon vaigiensis, is a commercial fish species distributed throughout the Indo-Pacific region. This species tolerates wide variations in salinity, having been reported from both freshwater and marine habitats. Although economically significant, there is little information on its reproduction, especially in the Vietnamese Mekong Delta (VMD), where it is heavily extracted. Our study elucidates the breeding pattern, seasonality, first length at maturity, as well as potential and relative fecundity of this species. Fish specimens were collected by trawl nets from November 2020 to October 2021 at four estuarine sites within the VMD. We found this species to be a synchronous spawner, with peaks in reproductive activity from June to September. In the populations we surveyed, there was significant dominance of males (1.26:1.00) based on 942 fish samples (526 males and 416 females). The length at 50% maturity for females was significantly higher than for males at all sites and ranged from 10.6 to 19.3 cm. The diameter of the eggs examined for this species exhibited slight variation, from 0.43 to 0.54 mm. The potential fecundity ranged from 246,254 ± 35,878 to 411,970 ± 54,370 eggs, corresponding to female length and weight of 26.7-32.6 cm and 102.97-234.19 g, respectively. Relative fecundity values were highest at Thanh Phu, Ben Tre (6388 ± 605 eggs), and Dong Hai, Bac Lieu (6461 ± 637 eggs), followed by Tran De, Soc Trang (4729 ± 408), and were found to be lowest at Duyen Hai, Tra Vinh (3117 ± 223 eggs). Information on reproductive behavior in this species has far-reaching impacts on sustainable extractions, stock conservation, and aquaculture.

Influence of environmental factors on reproduction of the invasive Gulf toadfish Opsanus beta (Teleostei: Batrachoididae) in a subtropical estuary

A hallmark of biological invasion is the rapid reproduction of invasive species. However, we still do not have an adequate understanding of how fluctuations in environmental factors affect the reproduction of invasive species, particularly in estuarine habitats. In this study, we evaluated the reproduction of the Gulf toadfish Opsanus beta and its relationships with temperature and rainfall in the Paranaguá estuary, a subtropical region in southern Brazil. This species was likely introduced into the Brazilian ecosystems through the discharge of ballast water. Since invasion, which was first reported in port areas, the species has rapidly spread along the Brazilian coast line. We collected specimens monthly from October 2011 to September 2012 and from October 2019 to September 2020, to give us insight into the seasonal and temporal changes in the reproduction of this species. We found that O. beta population uses the estuary throughout its life cycle, including during spawning. Females and males spawned throughout almost the entire sampling period and spawning was specified as partially. Peak reproductive activity occurred in periods of lower temperature and was also related to rain. The length of first maturation in females (10cm) was considered early, indicating reproductive activity in smaller individuals. Our results demonstrate that the reproductive strategy used by the invasive species supports its ability to successfully colonize new environments.

Little evidence for color- or size-based mating preferences by male strawberry poison frogs (Oophaga pumilio)

While there are many studies documenting female mating preferences across taxa, male mate choice remains relatively understudied. Male mate choice often develops when there is variation in female quality and thus the fitness benefits of mating with particular females. Specifically, males tend to prefer females with traits that confer direct fitness benefits such as large body size, which may be linked with high fecundity. Prior work has shown that females of the strawberry poison frog, Oophaga pumilio, prefer males bearing certain coloration (most often the female’s own color), and that this preference can be learned through maternal imprinting. Females have been shown to prefer larger males as well. Here we test whether similar mate preferences for color and size exist in males of this species using two-way choice tests on captive bred male O. pumilio. In each test focal males were placed in an arena with two stimulus females: either both of the same size but differing in color, or both of the same color but differing in size. We found only weak evidence for behavioral biases toward particular colors and no evidence for biases toward larger females, suggesting that males of O. pumilio do not predictably choose mates based on these female traits. Despite several aspects of their natural history that suggest males have reasons to be choosy, our findings suggest that the cost of mate rejection may outweigh any fitness benefits derived from being selective of mates. Studies of additional populations, ideally conducted on wild individuals, are needed to better understand the range of conditions under which males may exhibit mate choice and the types of traits on which they base these choices.Significance statementTo fully understand the fitness landscapes and evolutionary trajectories that result from sexual selection, we need to understand when and how the mate preferences of the two sexes act and interact. While female mate choice has been widely studied, male mate choice remains poorly understood. To help bridge this gap, we studied male mate preferences in the strawberry poison frog Oophaga pumilio, a small brightly colored frog for which female preferences for male color and size have been well-documented. We found no evidence that male O. pumilio exhibit mate preferences based on female size and little evidence for male mate preferences based on female color. This is surprising given that larger females are often more fecund, male O. pumilio are known to exhibit color-based behavioral biases in the context of male-male competition, and both sexes provide parental care.

Functional importance of groups I and II chitinases, CHT5 and CHT10, in turnover of chitinous cuticle during embryo hatching and post-embryonic molting in the red flour beetle, Tribolium castaneum

Chitinases (CHT) comprise a large gene family in insects and have been classified into at least eleven subgroups. Many studies involving RNA interference (RNAi) have demonstrated that depletion of group I (CHT5s) and group II (CHT10s) CHT transcripts causes lethal molting arrest in several insect species including the red flour beetle, Tribolium castaneum, presumably due to failure of degradation of chitin in their old cuticle. In this study we investigated the functions of CHT5 and CHT10 in turnover of chitinous cuticle in T. castaneum during embryonic and post-embryonic molting stages. RNAi and transmission electron microscopic (TEM) analyses indicate that CHT10 is required for cuticular chitin degradation at each molting period analyzed, while CHT5 is essential for pupal-adult molting only. We further analyzed the functions of these genes during embryogenesis in T. castaneum. Real-time qPCR analysis revealed that peak expression of CHT10 occurred prior to that of CHT5 during embryonic development as has been observed at post-embryonic molting periods in several other insect species. With immunogold-labeling TEM analysis using a fluorescein isothiocyanate-conjugated chitin-binding domain protein (FITC-CBD) probe, chitin was detected in the serosal cuticle but not in any other regions of the eggshell including the chorion and vitelline membrane layers. Injection of double-stranded RNA (dsRNA) for CHT5 (dsCHT5), CHT10 (dsCHT10) or their co-injection (dsCHT5/10) into mature adult females had no effect on their fecundity and the resulting embryos developed normally inside the egg. There were no obvious differences in the morphology of the outer chorion, inner chorion and vitelline membrane among eggs from these dsRNA-treated females. However, unlike dsCHT5 eggs, dsCHT10 and dsCHT5/10 eggs exhibited failure of turnover of the serosal cuticle in which the horizontal chitinous laminae remained intact, resulting in lethal embryo hatching defects. These results indicate that group I CHT5 is essential for pupal-adult molting, whereas group II CHT10 plays an essential role in cuticular chitin degradation in T. castaneum during both embryonic hatching and all of the post-embryonic molts. CHT10 can serve in place of CHT5 in chitin degradation, except during the pupal-adult molt when both enzymes are indispensable to complete eclosion.

Chemical control of the polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) and Fusarium euwallaceae in American sweetgum (Liquidambar styraciflua)

The polyphagous shot hole borer beetle (PSHB, Euwallacea fornicatus) is a pest of global significance. PSHB is an ambrosia beetle which, together with its mutualistic fungi (including Fusarium euwallaceae), can cause the death of more than 100 tree species in invaded ranges. Management of PSHB mostly relies on the removal of infested plant material. Chemical control options have been investigated only in the USA and Israel and only on a few tree species. This study evaluated four chemical treatments for the therapeutic control of PSHB on American sweetgum (Liquidambar styraciflua) in South Africa (1) bifenthrin + surfactant (alcohol ethoxylate), (2) cypermethrin + surfactant (vitamin E) + salicylic acid, (3) emamectin benzoate, and (4) propiconazole. Trees were inoculated with F. euwallaceae and mature PSHB females using a novel technique to document fungal lesion development and PSHB colony establishment success. The bifenthrin and cypermethrin treatments reduced additional PSHB colonisation attempts on treated trees by ca. 40%, while the other treatments had no effect. Colony establishment success was reduced in all treatments by between 20 and 40%. Fungal growth was inhibited only after the application of propiconazole by ca. 36%. Gallery length and the number of PSHB individuals in successful colonies were unaffected by any of the chemical treatments. These results indicate that chemical control of PSHB is only partially effective. Successful PSHB management will likely depend on a combination of chemical control options and other control strategies in an integrated pest management program.

(−)‐myrtenol and (−)‐α‐pinene: Aggregation pheromone components of the cypress bark beetle Phloeosinus aubei

AbstractThe cypress bark beetle, Phloeosinus aubei, is of increasing concern in the European market of scale‐leafed conifers. Neither the reproductive behaviour nor the chemical ecology have been studied in detail so far, and no specific attractant traps are available to monitor the flight of adults. We established that stridulation by males is crucial for acceptance by calling females. To unravel the chemical communication, hindgut extracts from unmated females were analysed by GC‐EAD, using male antennae. Gut extracts and Thuja occidentalis leaf extracts were analysed by GC/MS. Two antennally active compounds from gut extracts were identified as (−)‐myrtenol and (−)‐α‐pinene by enantioselective GC/MS. (−)‐Myrtenol was shown to be female‐specific, while (−)‐α‐pinene was found as a 2:1 mixture with the (+)‐enantiomer also among the volatiles of the host tree, T. occidentalis. To prove that the production of the above compounds in the beetles is related to reproduction, we treated females with JHIII. The gut extracts from these sexually mature females showed elevated levels of (−)‐α‐pinene compared to untreated control groups. Synthetic enantiomers of myrtenol and α‐pinene were tested separately by electroantennography, and all were found to be electrophysiologically active. The attractiveness of different mixtures of these compounds was compared using 4‐arm olfactometer tests: 4:1 mixtures of racemic α‐pinene with either (−)‐ or (+)‐myrtenol were significantly attractive to males and females, respectively. In field tests, multifunnel traps baited with a 5:1 mixture of (−)‐α‐pinene and (−)‐myrtenol caught significantly more males and females than unbaited control traps. We concluded that (−)‐α‐pinene and (−)‐myrtenol are components of a female‐produced aggregation pheromone. EAD activity and behaviour assays indicated that α‐pinene from Thuja is used by the beetles as part of a host plant kairomone. The complex communication system of P. aubei is discussed in a chemoecological context.

Divergent warning patterns influence male and female mating behaviours in a tropical butterfly.

Traits under divergent ecological selection that also function during mating can be important in maintaining species boundaries. Few studies have considered mutual mate choice, where both males and females base mating decisions on the same trait. Wing colouration in Heliconius butterflies evolved as a warning signal but also functions as a mating cue. We investigated the contribution of visual preference to assortative mating in an aposematic butterfly Heliconius cydno in the context of reproductive isolation with its sympatric, visually distinct relative Heliconius melpomene. Heliconius cydno have conspicuous white bands on their forewings, whereas those of H. melpomene are red in colour. We predicted that both sexes of H. cydno contributed to assortative mating by exhibiting visual preference towards conspecific wing colouration. We analysed published and new data from preference experiments, in which males were presented with conspecific and H. melpomene females. We also recorded female responses and mating outcomes in choice experiments, involving conspecific males with either the original white or artificially painted red forewing bands. Both sexes of H. cydno responded more positively towards the conspecific colouration, and males strongly preferred females of its own colours. In contrast, male colouration did not predict mating outcomes in female choice experiments. As courtships are initiated by males in butterflies, our findings suggest that female visual preference might be of secondary importance in H. cydno. Our data also suggest that the contribution of visual preference to reproductive isolation might be unequal between H. cydno and its sympatric relative H. melpomene.

State of the Siberian sturgeon population in the Middle Lena in summer

The purpose: to obtain modern data on the distribution, abundance, size composition and biological state of the sturgeon in the middle reaches of the Lena River.Material: data of scientific accounting survey using bottom drift nets in summer 2022.The results: Siberien sturgeon is dstributed irregularly on a 400‑kilometer stretch of the river from the city of Yakutsk to the Vilyui River, with the highest average density near the Vilyui River mouth 163 ind./km2, while sturgeon densities in the areas of Yakutsk and the Aldan River mouth were 71 and 44 ind./km2 respectively. The highest density of fish with the smallest average size in the area near the Vilyui mouth indirectly indicates the presence of a separate herd in the Vilyui River. The average density of fish over the entire 400‑km area was 93 ind./km2. The sturgeon length to the end of the middle rays (ac) was from 21 to 86 cm; on average 43.4 ± 10.7 cm. The modal size class for the sturgeon in catches in 2022 was 41–50 cm (44% of the total catch). The fish weight ranged from 40 to 3800 g. The average weight of individuals was 0.557. More than 80% of fish from all catches weighed up to 700 g. The weight of fish with a length ac 62–71 cm ranged from 0,400 to 1.415 kg, on average 1.0 kg. There were only 2.5% of commercial individuals in the total harvest. Sexually mature females were noted only near the Aldan mouth, where their share was 11% that may indicate the presence of spawning grounds in its channel. In the sample of fish that underwent a complete biological analysis (one third of the catches), sexually mature males were not observed. Estimated number of sturgeon: in Yakutsk city area — 17000 ind., in the Aldan mouth area — 47000 ind., in the Vilyui mouth area — 55000 ind. The total number of Siberian sturgeon on a 400‑kilometer stretch of the Lena River was at least 120000 ind. The state and structure of sturgeon population corresponds to the average statistical retrospective data.Practical value: the results obtained will improve the efficiency of assessing the distribution and stock of sturgeon in the Lena River.

Testing ‘bigger is better’ and maternal effects hypotheses in hatchlings of the sexually dimorphic spiny softshell turtle (Apalone spinifera)

Abstract The ‘bigger is better’ hypothesis (BIBH) predicts that fitness increases with body size. Eastern spiny softshell turtles (Apalone spinifera) exhibit sexual size dimorphism (SSD) at maturity, and the much larger female body size is attributed to selection favouring greater reproductive output. Hatchlings exhibit sexually dimorphic markings, but hatchling SSD has not been investigated. The BIBH predicts that hatchlings will not exhibit SSD because reproductive benefits to larger, mature females drive size dimorphism at maturity, but selection on hatchlings relates only to survival. We tested this prediction with A. spinifera hatchlings (N = 2630) incubated in controlled conditions to avoid confounding environmental effects on phenotype. Hatchling mass was similar between sexes, suggesting similar nutritional allocation to male and female offspring. Hatchling size (carapace length) was also similar between sexes. Hatchling mass and body size varied among clutches and were positively related to maternal size, suggesting morphological constraints on egg size. Surprisingly, clutch size was related only weakly to maternal size. Taken together, our results suggest that hatchling size in A. spinifera is consistent with the BIBH and that offspring quality increases with maternal age, but that maternal effects drive a large proportion of the variation in clutch size and offspring quality.