Male Brood Research Articles

Sex allocation is color morph-specific and associated with fledging condition in a wild bird.

Melanin-based color polymorphism is predicted to evolve and maintain through differential fitness of morphs in different environments, and several empirical studies indicate that life history strategies, physiology, and behavior vary among color morphs. Sex allocation theory predicts that parents should adjust their sex allocation based on differential costs of raising sons and daughters, and therefore, color morphs are expected to modify their brood sex ratio decisions. In color polymorphic tawny owls (Strix aluco), the pheomelanistic brown morph is associated with higher energy requirements, faster growth, and higher parental effort than the gray morph. As hypothesized, we find that brown tawny owl mothers produced more daughters in early broods and more males in late broods, whereas gray mothers did the opposite. At fledging, daughters of early broods and of brown mothers were heavier than those of late broods or gray mothers. Hence, larger and more costly daughters appeared to benefit more than males from being born to brown mothers early in the season. Brown mothers breeding later in the season produced more cheap sons, while gray mothers face fewer challenges under limited resources and favor daughters. These findings suggest that environmental conditions influence brood sex allocation strategies of genetically determined color morphs differently.

Observation of interspecific feeding by White-browed Shrike-Babbler (Pteruthius aeralatus) of brood-parasitic nestlings of Chestnut-winged Cuckoo (Clamator coromandus) in a Nest of Greater Necklaced Laughingthrush (Pterorhinus pectoralis).

The occurrence of interspecific feeding events, involving non-obligate nest parasite species, is rare but has been documented in numerous avian species worldwide, particularly in Europe and North America. Our report presents an observation from southwest China, where we observed a Greater Necklaced Laughingthrush (Pterorhinus pectoralis) nest containing three laughingthrush nestlings and two nestlings of Chestnut-winged Cuckoos (Clamator coromandus). They were being fed by the adult laughingthrush and a male White-browed Shrike-Babbler (Pteruthius aeralatus). However, after the cuckoo nestling fledged, we did not observe the Shrike-Babbler feeding the laughingthrush nestlings remaining in the nest. Through a systematic examination of potential driving factors, we infer that the begging calls of the cuckoo nestlings likely played a crucial role in the misfeeding events observed in our study. However, it is essential to consider the potential influence of the male shrike-babbler's status, including mateless, brood loss or female incubation. We highlight the further observations using digital recordings (for both images and sounds) to document detailed information on interspecific feeding events.

Gonadotropic Activity of Pituitary Extract of African Catfish, Clarias gariepinus, in Mammals using Immature Wistar Rats as Models.

The pituitary glands normally produce and stores gonadotropic hormones (GnH) that are responsible for ovulation and spermiation in animals. However, whether fish pituitary extracts can elicit same effects in treated animals need elucidation as a prelude to their practical usage in animals. The aim of this study was to investigate the oestrus-inducing potential of the pituitary gland extract of the Africa Catfish (Clarias gariepinus) in immature Wistar rats. The experiment involved the use of 18 immature female Wistar rats and 10 male catfish brood stocks with the use of six Wistar rats per groups as follows: Group A had human chorionic gonadotropin (hCG) treatment. Group B had only normal saline treatment as the control whereas Group C had the C. gariepinus pituitary extract administration to induce oestrus with treatments occurring twice six hours apart in each group. There was an obvious expression of visible signs of heat and the presence of uterine horn oedema with significant (p < 0.05) increase in reproductive tract weight and uterine width and length. However, only progesterone levels increased significantly (p < 0.05) in the hCG and the C. gariepinus pituitary extract treated groups compared to other assayed hormones. These results showed that C. gariepinus pituitary extract has the capacity to induce oestrus in Wistar rats because of its gonadotropic effects, which needs further investigations at higher doses and for longer exposure periods for possible oestrus induction and synchronization in higher mammals. Further favourable results could herald the possible patent of the catfish pituitary extract for either experimental or commercial use in mammals.

Male guarding behavior and brood predators of invasive Bluegill in a Japanese lake

AbstractObjectiveThe Bluegill Lepomis macrochirus, which utilizes colony spawning, has been introduced globally, and in Japan it is considered one of the worst invasive species. However, a detailed examination of the factors driving male guarding behavior and brood predation in the invaded habitat is lacking. The removal of guarding males, a common management technique in Japan, is thought to be effective in controlling Bluegill. However, the colony spawning strategy may influence the effectiveness of selective male removal through brood protection from neighbor males.MethodsBluegill spawning was studied in Lake Nojiri, Nagano, Japan, using underwater video recording and experimental removal of guarding males.ResultBluegill were found spawning in shallow habitat during June–July, and nests were constructed in loosely aggregated colonies, with many solitary nests. Males utilized a variety of guarding behaviors, such as rim circling and predator chases, as well as paternal investment behaviors, such as tail fanning. Males that preyed upon their own eggs defended their nests less aggressively and invested less time in nourishing behaviors. Removal of guarding males revealed that brood predators were primarily conspecific Bluegill, but other fishes, such as invasive Smallmouth Bass Micropterus dolomieu and Largemouth Bass M. nigricans as well as native Japanese Dace Pseudaspius hakonensis, preyed on broods.ConclusionIn concurrence with the colony spawning theory, nests that were located closer to other nests with active guarding males experienced decreased brood predation and increased predator arrival time after male removal. In addition, nests where males had been guarding more aggressively prior to removal experienced reduced brood predation after male removal. These results provide insights into the factors driving male guarding behavior and brood predation of colony‐spawning Bluegill in an invasive habitat and indicate that the removal of guarding males—a common management strategy in Japan—may have reduced effectiveness due to colony spawning.

Induced Breeding of Endangered Labeo calbasu (Hamilton, 1822) Under a Hatchery System

Experiment was conducted on the effectiveness of two inducing hormones (Ovaprim and PG) on induced breeding of Labeo calbasu, an endangered Kalibaus species. From April to July of 2022, Labeo calbasu were bred artificially. For the purpose of induced breeding, male and female brood fish weighing between 1.2 kg and 2.0 kg for the male and 1.4 kg and 2.5 kg for the female were chosen, and the sex ratio was maintained at 1:1. PG and LHRH-A were used in the experiment’s design for the period of April, May, June, and July. Under controlled conditions, the impact of two hormones sources on L. calbasu ovulation, fertility, and hatching rate was studied. A single dose of Ovuline® (LHRH-A) (0.44 -0.50 ml/kg body weight) plus two doses of PG (an initial dose of 2.0 mg/kg body weight and a final dose of 4.0-4.5 mg/kg body weight) showed better results in this group of females. In the period of May and June, the ovulation, fertility, and hatching rate of L. calbasu were all better in both PG and LHRH-A. Ovuline® (LHRH-A) 0.15 ml/kg body weight and PG 2 mg/kg body weight provided as a single dose to males resulted in superior spermiation outcomes. Fish weighing 1.55±0.86 kg had the highest GSI value (22.82%) and fecundity (501301±9.96), whereas fish weighing 1.51±0.96 kg had the lowest GSI value (18.24%) and fecundity (350561±8.76). The treatment of PG showed the highest rates of fertilization (98.40±1.17%) and hatching (88.03±2.76%), whereas the treatment of LHRH-A showed the highest rates of fertilization (98.64±0.84%) and hatching (89.55a ±0.88%). According to the results of this experiment, PG and ovaprim are equally effective at causing L. calbasu ovulation, fertilization, and hatching. Both PG and LHRH-A could be applied by hatchery operators to enhance L. calbasu breeding performance by inducing better spawning.

The evolution of extra-pair paternity and paternal care in birds.

Extra-pair paternity (EPP) influences the relatedness between social parents and offspring. Therefore, one might expect the level of EPP to influence levels of paternal investment. Here, we investigated the effect of variation in EPP rates on male contributions to parental care within a phylogenetic framework of up to 271 primarily socially monogamous bird species representing 85 families. We used proportion of male provisioning and occurrence of male incubation and nestbuilding as measures of paternal care. We tested the relationship between EPP rates and different components of paternal care while controlling for various life-history traits, namely lifespan, clutch size, and body mass in a phylogenetic path analysis framework. EPP was significantly negatively associated with the occurrence (i.e., whether males participate or not) of male nestbuilding and incubation, but not with the relative amount (proportion) of nestbuilding or incubation performed by the male. Importantly, the proportion of provisioning and biomass delivery by males was clearly negatively associated with EPP. These analyses thus confirm that the effect of EPP on proportion of provisioning visits by males is similar to proportion of biomass delivery, an often assumed but rarely tested assumption. Analysing only Passerine species provided similar results, although only proportion of provisioning was significantly negatively associated with EPP. This study, therefore, provides the most comprehensive support to date of a negative relationship between EPP and paternal care across species. However, a causal relationship between EPP and paternal care cannot necessarily be concluded. We also identify key methodological improvements for future research within the topic.

Evaluation of carboxylated poly-l-lysine for cryopreservation of Labeo rohita sperm.

Carboxylated poly-l-lysine (CPLL) is an anti-freeze agent having pronounced non-permeating yet membrane stabilizing cryoprotective capabilities. The objective was to evaluate the CPLL supplementation in extender in terms of post-thaw quality (sperm), total anti-oxidant activity (milt) and fertilization potential of cryopreserved Labeo rohita sperm. For this purpose, male brood fish reared at a fish seed hatchery, Rawal Town Islamabad, Pakistan were captured from different rearing ponds and acclimatized in hatchery ponds for 6 h. The brooder was injected with Ovaprim (0.2 mL/kg), and milt was collected after 8 h in cooled sterilized falcon tubes, maintained at 4°C and evaluated for sperm motility. The milt collected from three brooders (n = 3) was diluted in extenders viz., modified Kurokura-2 extender having 10% methanol (control); experimental extenders with CPLL supplementation at the rate of 0.5%, 1% and 1.5%. Diluted milt was filled in 0.5 mL straws, exposed to liquid nitrogen vapours and cryopreserved. Cryopreserved milt was thawed at 25°C and assessed for post-thaw sperm quality. Sperm motility, motility duration, viability, total anti-oxidant capacity and DNA integrity was significantly higher (p < 0.05) in the extender having 1.5% CPLL than control. To evaluate the fertilization rates, male and female brooders were injected with Ovaprim at 0.2 mL/Kg and 0.5 mL/Kg body weight respectively. Fresh eggs and milt were collected through abdominal stripping. Batches of 10 g of eggs from each female (n = 2) were fertilized with one straw, each from frozen sperm with KE + methanol (control), KE + methanol + 1.5% CPLL and 50 μL fresh milt (negative control). After 1.5 h of fertilization, eggs were collected from all jars and a total of 200 eggs were counted. The fertilized eggs appeared clear and transparent while unfertilized eggs looked opaque with disintegrated nuclei. Sperm fertilization rate (%) was higher (p < 0.05) in extender KE + methanol + 1.5% CPLL (78.7 ± 0.5) compared to control (KE + methanol) (52.0 ± 0.4) however, it was lower compared to that of negative control, the fresh milt (85.2 ± 0.6). In conclusion, supplementation of carboxylated poly-l-lysine (1.5%) to modified Kurokura-2 extender having 10% methanol improves post-thaw motility, motility duration, viability, DNA integrity, anti-oxidant capacity (milt) and fertilizing ability of cryopreserved L. rohita sperm.

Influence of different feeding rates of polychaete worms, Eulalia viridis (Annelida, Polychaeta), on the gonad development of male Penaeus semisulcatus (Decapoda, Dendrobranchiata) under captive conditions

Abstract Penaeus semisulcatus is a large growing species, attaining a maximum size of about 250 mm in total length. It is more resistant to white spot syndrome virus (WSSV) than other cultivable penaeid shrimps, which makes it a potential candidate for culture. The present study evaluated the influence of a different feeding rate of polychaete worms on the gonad development of male P. semisulcatus under captive conditions. P. semisulcatus sub-adults were obtained in the wild. The shrimps were fed with three different concentrations of polychaete worms, viz., ad libitum (T1), 5% of body weight (BW) (T2) and 10% BW (T3), and fresh sardines were fed as a Control (C) diet, all for a period of 60 days. Sampling was done once in 15 days and the bio-growth parameters were recorded. The gonads were harvested for histological analysis. The maximum weight gain (10.19 g), mean weight gain percentage (85.20%), mean daily growth rate (DGR) (0.169833) and mean specific growth rate (SGR) (0.45) were found in shrimps fed with the polychaete worm diet at 5% BW. The estimated bio-growth parameter values were statistically significant when analysed using One way ANOVA (). Histological sections of the testis showed variations in the development of the gonad between the treatments with different feeding rates during the 60 days trials. Indeed in all aspects, the development was higher in shrimps fed with polychaete worms at 5% BW. It can be concluded that feeding polychaete worms at 5% BW created a regime able to improve growth rates, gonad maturation, and quality in the development of the captive male brood stock.

Measuring Embryonic Viability and Brood Size in Caenorhabditis elegans.

Caenorhabditis elegans is an excellent model organism for the study of meiosis, fertilization, and embryonic development. C. elegans exist as self-fertilizing hermaphrodites, which produce large broods of progeny-when males are present, they can produce even larger broods of cross progeny. Errors in meiosis, fertilization, and embryogenesis can be rapidly assessed as phenotypes of sterility, reduced fertility, or embryonic lethality. This article describes a method to determine embryonic viability and brood size in C. elegans. We demonstrate how to set up this assay by picking a worm onto an individual Modified Youngren's, Only Bacto-peptone (MYOB) plate, establish the appropriate timeframe to count viable progeny and non-viable embryos, and explain how to accurately count live worm specimens. This technique can be used to determine viability in self-fertilizing hermaphrodites as well as cross-fertilization by mating pairs. These relatively simple experiments are easily adoptable for new researchers, such as undergraduate students and first-year graduate students.

Prolactin and the evolution of male pregnancy

Prolactin (PRL) is a multifunctional hormone of broad physiological importance, and is involved in many aspects of fish reproduction, including the regulation of live birth (viviparity) and both male and female parental care. Previous research suggests that PRL also plays an important reproductive role in syngnathid fishes (seahorses, pipefish and seadragons), a group with a highly derived reproductive strategy, male pregnancy - how the PRL axis has come to be co-opted for male pregnancy remains unclear. We investigated the molecular evolution and expression of the genes for prolactin and its receptor (PRLR) in an evolutionarily diverse sampling of syngnathid fishes to explore how the co-option of PRL for male pregnancy has impacted its evolution, and to clarify whether the PRL axis is also involved in regulating reproductive function in species with more rudimentary forms of male pregnancy. In contrast to the majority of teleost fishes, all syngnathid fishes tested carry single copies of PRL and PRLR that cluster genetically within the PRL1 and PRLRa lineages of teleosts, respectively. PRL1 gene expression in seahorses and pipefish is restricted to the pituitary, while PRLRa is expressed in all tissues, including the brood pouch of species with both rudimentary and complex brooding structures. Pituitary PRL1 expression remains stable throughout pregnancy, but PRLRa expression is specifically upregulated in the male brood pouch during pregnancy, consistent with the higher affinity of pouch tissues for PRL hormone during embryonic incubation. Finally, immunohistochemistry of brood pouch tissues reveals that both PRL1 protein and PRLRa and Na+/K+ ATPase-positive cells line the inner pouch epithelium, suggesting that pituitary-derived PRL1 may be involved in brood pouch osmoregulation during pregnancy. Our data provide a unique molecular perspective on the evolution and expression of prolactin and its receptor during male pregnancy, and provide the foundation for further manipulative experiments exploring the role of PRL in this unique form of reproduction.

Vertical transmission of Renibacterium salmoninarum in cutthroat trout (Oncorhynchus clarkii).

Vertical transmission of Renibacterium salmoninarum has been well-documented in anadromous salmonids but not in hatchery-reared inland trout. We assessed whether the bacterium is vertically transmitted in cutthroat trout (Oncorhynchus clarkii) from a Colorado, USA hatchery, and assessed the rate of transmission from male and female brood fish. Adult brood fish were killed, tested for R. salmoninarum in kidney, liver, spleen, ovarian fluid, blood and mucus samples, then stripped of gametes to create 32 families with four infection treatments (MNFN, MNFP, MPFN, MPFP; M: male, F: female, P: positive, N: negative). Progeny from each treatment was sampled at 6 and 12 months to test for the presence of R. salmoninarum with an enzyme-linked immunosorbent assay and quantitative polymerase chain reaction. Our study indicated that vertical transmission was high and occurred among 60% of families across all infection treatments. However, the average proportion of infected progeny from individual families was low, ranging from 1% (MNFP, MPFN and MPFP treatments) up to 21% (MPFP treatment). Hatcheries rearing inland salmonids would be well suited to limit vertical transmission through practices such as lethal culling because any amount of transmission can perpetuate the infection throughout fish on a hatchery.

Induction Spawning of Endangered Kuria Labeo, Labeo gonius (Hamilton-Buchanan, 1822) under Hatchery System

Efficacy of two inducing hormones (PG and Ovaprim) was conducted on induced breeding of endangered Kalibaus (Labeo gonius). Induced breeding of L. gonius was carried out from April to July, 2022. Male and female brood fish weighing between 0.85±0.43kg and 0.88±0.50 kg in case of male and 0.97±0.641.4kg to 0.99±0.802.5kg in case of female were selected for the induced breeding and sex ratio were maintained 1:1 for the breeding purpose. The experiment was designed with the month of April, May, June and July with PG and LHRH-A. Two hormonal sources were tested to evaluate their efficacy on ovulation, fertility and hatching rate of L. gonius under controlled conditions. Double doses of PG (an initial dose of 1.5mg/kg body weight and final dose of 4.0mg/kg body weight) and single dose of Ovuline® (LHRH-A) (0.4 -0.45ml/kg body weight) showed better results in case of females. Bothe PG and LHRH-A had shown better results of ovulation, fertility and hatching rate of L. gonius in the month of May-June. Males were administered with a single dose of Ovuline® (LHRH-A) 0.15 ml/kg body weight and PG 1.5 mg/kg body weight showed better results of spermiation. Highest GSI value (22.24%) and fecundity (300411±7.16) were found in 0.90±0.80kg body weighted fish and the lowest value of GSI (20.01%) and highest fecundity (380822±9.11) were found in 1.10±0.96kg body weighted fish. The highest fertilization rates (98.40±1.17%), hatching rates (88.03±2.76%) were recorded in treatment of PG and highest fertilization rates (98.64±0.84%), hatching rates (89.55a±0.88%) were recorded in treatment of LHRH-A. This experiment recommends Ovaprim and PG both are efficient for inducing ovulation, fertilization and hatching of L. calbasu. The hatchery operators may be used both PG and LHRH-A for induction of spawning better performance of L. gonius breeding.

Independent evolution of sex chromosomes and male pregnancy-related genes in two seahorse species.

Unlike birds and mammals, many teleosts have homomorphic sex chromosomes and changes in the chromosome carrying the sex-determining locus, termed "turnovers", are common. Recent turnovers allow studies of several interesting questions. One question is whether the new sex-determining regions evolve to become completely non-recombining, and if so, how and why. Another is to test the prediction that evolutionary changes that benefit one sex will accumulate in the newly sex-linked region. To study these questions, we analyzed the genome sequences of two seahorse species of the Syngnathidae, a fish group in which many species evolved a unique structure, the male brood pouch. We find that both seahorse species have XY sex chromosome systems, and their sex chromosome pairs are not homologs, implying that at least one turnover event has occurred. The Y-linked regions respectively occupy 63.9% and 95.1% of the entire chromosome of the two species, and do not exhibit extensive sequence divergence with their X-linked homologs. We find evidence for occasional recombination between the extant sex chromosomes that may account for their homomorphic pattern. We argue that these Y-linked regions did not evolve by recombination suppression after the turnover. Instead, it can be explained by the ancestral nature of low crossover rate at the corresponding chromosome location. With such an ancestral crossover landscape, a turnover can instantly create an extensive Y-linked region. Finally, we investigate the adaptive evolution of male pouch related genes after they become Y-linked in the seahorse.

Evaluation of Population Parameters of Seahorses in Areas with and without Tourism in Federal Marine Protected Areas in Northeast Brazil

In Brazil, there is the tourist attraction of interacting with seahorses, which occurs through raft rides, during which the animals are captured and displayed in glass containers to be photographed and filmed by tourists. Two federal protected marine areas where this activity takes place were monitored, Jericoacoara National Park (monitored area of 600 m2 ), in the state of Ceará, and Environmental Protection Area (EPA) Delta do Parnaíba (monitored area of 547 m2 ), in the state of Piauí. Between 2011 and 2015, in both PMAs, the active search for animals was carried out by snorkeling during low tide, and the only species found was Hippocampus reidi, with 1286 sightings of seahorses in the National Park and 602 in the EPA. Results such as the mean height at formation of the male brood pouch (11.35 and 11.52 cm at EPA and National Park, respectively), size at first sexual maturity (14.2 and 14.7 cm, respectively) and reproductive period throughout the year were very similar between the populations of the two protected areas. All sites in both PMAs suffered a significant reduction in seahorse population during the study, except for the site P2 in EPA where the seahorse numbers remained stable throughout the study.

Effect of Different Doses of Pituitary Gland (PG) Hormone on Induced Breeding of Bheda/Meni (Nandus nandus) Fish

An experiment on induced breeding of Bheda/Meni fish (Nandus nandus) was carried out to determine the optimum dose of pituitary gland hormone during December 2018 to June 2019 at Floodplain Sub-station of Bangladesh Fisheries Research Institute (BFRI), Santahar, Bogura. In this experiment, PG was used as inducing agent for both male and female fish. For induced breeding, PG was administered at the rate of 1, 2 and 3 mg/kg body weight to male brood fish, and correspondingly 2, 4 and 6 mg/kg body weight to female brood fish that were considered as the treatments namely, T1, T2 and T3, respectively. Fifty pairs of male and female fish were collected from the Raktadaha beel from where forty-five pairs were selected for induced breeding and the average body weight of the male and female were 43.0±2.5 gm and 55.2±3.0 gm in T1, 45.1±2.9 gm and 56.0±2.8 gm in T2, and 40.3±2.4 gm and 52.6±3.2 gm in T3. The male-female ratio was maintained as 1:1 in the breeding hapa. It was observed that female and male brood fishes ejected eggs and milt, respectively at the contemporary times. Ovulation occurs naturally after 8-10 hours of injection. The fecundity of fish (body weight 45 to 60 gram each) varied from 7,232-27,546. The fertilized eggs were hatched within 16-20 hours. The hatchlings were reared in rearing tank up to 5 days. The fertilization rate of Nandus nandus were 76±4 %, 93±5 % and 57±3 %, in T1, T2, and T3, respectively and the hatching rate were 72±3 %, 86±2 % and 61±4 % in T1,T2 and T3, respectively. Both the fertilization and hatching rates were significantly higher (p&lt;0.05) in T2 treatment than T1 treatment followed by T3 treatment. The mean values of water temperature (°C) were 29.5±1.15, 30.0±2.03 and 30.8±1.76°C, pH was 7.4 ±0.46, 7.8±0.53 and 7.3±0.49 and dissolved oxygen (mg/L) were 5.5±0.61, 5.3±0.24 and 5.8±0.56 in brooder tanks, breeding hapa and larval hapa, respectively during the experiment and did not vary (P&gt;0.05) among them and were suitable for induced spawning of Nandus nandus. Based on the findings of the present experiment, it was revealed that T2 showed the best outcome in terms of fertilization rate (93±5%) and hatching rate (86±2%) among the three treatments under optimum water quality parameters where PG hormone were used at the rate of 2 and 4 mg/kg body weight for male and female fish, respectively. Therefore, the present findings could be used in induced breeding of N. nandus for the development of hatchery propagation. Further trials on rearing or culture of this endangered fish under different stocking densities or feedings might be conducted at on-station and on-farm levels in Bangladesh as well as elsewhere of this region to save the fish from extinction or for its conservation and rehabilitation.

Revisiting the hymenopteran diploid male vortex: a review of avoidance mechanisms and incidence

AbstractAll hymenopterans (bees, ants, wasps, and sawflies) have haplodiploid sex determination. Generally, this involves haploid males developing from unfertilized eggs and diploid females developing from fertilized eggs, but diploid male production (DMP) frequently occurs. Some species have complementary sex determination (CSD), in which heterozygotes of a csd locus or loci are diploid females, hemizygotes are haploid males, and homozygotes are typically sterile diploid males. These diploid males underlie the diploid male vortex (DMV), the phenomenon of inbreeding reducing csd allelic diversity and causing increasingly higher production of sterile diploid males until the population dies out. The DMV has been cited as an extinction risk for many species across the order and a danger to both human‐controlled and natural hymenopteran populations important in biological control, pollination, and endangered species conservation. However, it has been unclear how frequently it occurs. We review the known mechanisms for DMV avoidance. Many of these mechanisms are linked to lifestyle, and so we structure our investigation around eusocial lifestyle and non‐eusocial (solitary or gregarious) species. We also review documented DMV incidence to make an inference about its prevalence. There are many means to avoid inbreeding or diploid male production, including eusocial‐exclusive polygyny, polyandry, and diploid queen execution. For both eusocial and non‐eusocial species these include biological mechanisms such as multi‐locus CSD or non‐CSD sex determination, diploid male inviability or brood removal, partial diploid male fecundity, and mating avoidance of kin or diploid males; or population genetic mechanisms such as gene flow and dispersal, balancing selection of csd alleles (with some being more prominent in eusocial vs. non‐eusocial species). Documented cases of DMV are uncommon, and incidence is often tied to exacerbatory conditions such as habitat fragmentation and host declines. With this review we suggest that due to numerous avoidance mechanisms, DMV risk may not be as high as previously believed, and requires specific circumstances. In doing so we aim to better inform hymenopteran breeding and conservation efforts.

Male survivorship and the evolution of eusociality in partially bivoltine sweat bees.

Eusociality, where workers typically forfeit their own reproduction to assist their mothers in raising siblings, is a fundamental paradox in evolutionary biology. By sacrificing personal reproduction, helpers pay a significant cost, which must be outweighed by indirect fitness benefits of helping to raise siblings. In 1983, Jon Seger developed a model showing how in the haplodiploid Hymenoptera (ants, wasps and bees), a partially bivoltine life cycle with alternating sex ratios may have promoted the evolution of eusociality. Seger predicted that eusociality would be more likely to evolve in hymenopterans where a foundress produces a male-biased first brood sex ratio and a female-biased second brood. This allows first brood females to capitalize on super-sister relatedness through helping to produce the female-biased second brood. In Seger's model, the key factor driving alternating sex ratios was that first brood males survive to mate with females of both the second and the first brood, reducing the reproductive value of second brood males. Despite being potentially critical in the evolution of eusociality, however, male survivorship has received little empirical attention. Here, we tested whether first brood males survive across broods in the facultatively eusocial sweat bee Halictus rubicundus. We obtained high estimates of survival and, while recapture rates were low, at least 10% of first brood males survived until the second brood. We provide empirical evidence supporting Seger's model. Further work, measuring brood sex ratios and comparing abilities of first and second brood males to compete for fertilizations, is required to fully parameterize the model.

Reproductive Tract Morphometry and Evaluation of Fresh Wild African ‎Catfish (Clarias gariepinus) Milt from Lake Alau, Maiduguri, Nigeria‎

Reproductive morphometry of Clarias gariepinus (C. gariepinus) is essential in distinguishing different species that are closely related to it and adequate information is required regarding the seasonal variation of milt characteristic of wild species. This study was designed to document the reproductive tract morphometric dimensions and milt characteristics of wild C. gariepinus during spawning and non-spawning seasons in Lake Alau, Maiduguri, Nigeria. Sixty male brood stocks were used comprising thirty each for spawning and non-spawning seasons. The reproductive tracts were removed and their dimensions measured. The milt samples were collected, pooled and evaluated. Results of the study showed that the body weight, sperm concentration and testicular indices differed significantly (p˂0.05) between the two seasons of evaluation. In addition, a positive correlation (p˂ 0.05) between body weight of fish and milt volume (r = 0.656 and r = 0.646) was also observed in both seasons. It was concluded that the left testis of C. gariepinus is heavier, longer and thicker than the right. Nonetheless, the C. gariepinus had larger body weights and higher spermatozoa concentration in spawning season than in non-spawning season; those with larger body weights had higher volume of milt than those with lower body weights.

Local and overseas carp pituitary gland in the induced breeding of Cirrhinus mrigala (Hamilton 1822)

Stimulating hormone for artificial fish breeding in hatchery industry is very crucial for hatching operation, healthy fry and fingerling production, while overall fish production of a country. The present study was conducted to assess the effectiveness of using local and overseas Carp Pituitary Gland (CPG) in the induced breeding of Cirrhinus mrigala at Jashore district from April to May 2022. The first dose of hormone, both for male and female brood fishes were injected with local and overseas CPG at 0.5mg/kg body weight. After six hours of the first dose, only female brood fishes were injected with the second dose of PG at 5 mg/kg body weight. After 6 hours of second dose CPG injection of local and overseas PGs, brood fishes started spawning. The ovulation rates for both local and overseas PGs were estimated 100%. The fertilization rates were 93.5 % and 92.6 % for local and overseas PGs; while the hatching rates were 91.2% and 89.5%, respectively. However, local CPG is highly recommended to hatchery owners considering the rate of fertilization, hatching rate and availability. Asian J. Med. Biol. Res. 2022, 8 (3), 146-153

Seahorse brood pouch morphology and control of male parturition in Hippocampus abdominalis

IntroductionSyngnathids (seahorses, pipefishes and seadragons) are among the few vertebrates that display male pregnancy. During seahorse pregnancy, males incubate developing embryos embedded in a placenta within a fleshy brood pouch, before expelling fully developed neonates at parturition. The mechanisms underpinning seahorse parturition are poorly understood. MethodsWe examined the morphology of the brood pouch using microcomputed tomography and histological techniques, in combination with physiological assays, to examine how male pot-bellied seahorses (Hippocampus abdominalis) control labour. In female-pregnant vertebrates, nonapeptide hormones (such as vasopressin- and oxytocin-like hormones) produce contractions of gestational smooth muscle to produce labour. ResultsHistological analysis of the seahorse brood pouch reveals only scattered small smooth muscle bundles in the brood pouch, and in-vitro application of isotocin (a teleost nonapeptide hormone) to the brood pouch do not produce measurable muscle contractions. Micro-computed tomography shows differences in size and orientation of the anal fin assembly between male and female pot-bellied seahorses, and histological analysis reveals large skeletal muscle bundles attached to the anal fin bones at the male brood pouch opening. DiscussionWe conclude that seahorse parturition may be facilitated by contraction of these muscles, which, in combination with body movements, serves to gape open the pouch and expel the neonates. Future biomechanical studies are needed to test this hypothesis.