Spermatheca Size Research Articles

Comparison of reproductive traits of foundresses in a native and an invasive hornet in Europe

The population dynamics of annual social hymenoptera such as vespids depend largely on the fertility of the foundresses, which, in turn, is a key factor in the context of biological invasions. The native European hornet Vespa crabro (Vc) and the invasive Asian hornet Vespa velutina (Vv) have generally similar ecological traits, e.g. nesting and feeding habits, although they differ in colony size, which is higher in Vv. Furthermore, in contrast to Vc, Vv is more specialized in its predatory habits, intensively hunting honey bees at the hive. Comparing the morphological and reproductive traits of two closely related species occupying the same ecological niche, one of which is a native species and the other an alien, can help us to gain an understanding of the invasion process. To this end, we here compare reproductive (ovarian size and maturation, fat level, spermatheca size and sperm stock, fecundity) and morphological traits (head size, weight) of the foundresses of these two hornet species. We observed that ovarian maturation began approximately one month earlier in Vv than in Vc, and that the fat level in the former was lower. We found twice the number of sperm in the mated foundresses of Vv than in those of Vc (more than 100 × 103 and less than 50 × 103 sperm, respectively), in a 16% smaller spermatheca in Vc. Furthermore, the sperm of Vv was found to be 65% shorter than that of Vc. The precocity and higher potential fecundity of Vv queens may have favoured this species over Vc in terms of predatory behaviour, and thereby contributed to its invasiveness.

Queen traits and colony size of four bumblebee species of China

Bumblebee pollination efficiency is significantly affected by colony size, which differs among different bumblebee species. Bumblebee colonies are initiated by a single queen; thus queen traits have an important influence on colony development. To make better use of native bumblebee species and select bumblebee species for commercial rearing, queens from four bumblebee species in China, Bombus terrestris, B. lantschouensis, B. patagiatus and B. ignitus, were reared and studied to determine whether differences in queen traits and colony size occur at the interspecific level. In our study, the four bumblebee species differed significantly in colony size, queen body length, spermatheca size and sperm quantity. The queens of the four species mated only once. Among these four bumblebee species, the species with more sperm in the queen’s spermatheca usually exhibited a larger colony size. The quantity of sperm in the queen’s spermatheca might serve as an indicator for selecting bumblebee species with commercial rearing potential. However, our study involved only four bumblebee species; more bumblebee species are needed to confirm the correlation between queen sperm quantity and colony size.

One size fits all? Determinants of sperm transfer in a highly dimorphic orb-web spider.

The evolutionary significance of widespread hypo-allometric scaling of genital traits in combination with rapid interspecific genital trait divergence has been of key interest to evolutionary biologists for many years and remains poorly understood. Here, we provide a detailed assessment of quantitative genital trait variation in males and females of the sexually highly dimorphic and cannibalistic orb-weaving spider Argiope aurantia. We then test how this trait variation relates to sperm transfer success. In particular, we test specific predictions of the one-size-fits-all and lock-and-key hypotheses for the evolution of genital characters. We use video-taped staged matings in a controlled environment with subsequent morphological microdissections and sperm count analyses. We find little support for the prediction of the one-size-fits-all hypothesis for the evolution of hypo-allometric scaling of genital traits, namely that intermediate trait dimensions confer highest sperm transfer success. Likewise, our findings do not support the prediction of the lock-and-key hypothesis that a tight fit of male and female genital traits mediates highest sperm transfer success. We do, however, detect directional effects of a number of male and female genital characters on sperm transfer, suggesting that genital trait dimensions are commonly under selection in nature. Importantly, even though females are much larger than males, spermatheca size limits the number of sperm transferred, contradicting a previous hypothesis about the evolutionary consequences of genital size dimorphism in extremely size-dimorphic taxa. We also find strong positive effects of male body size and copulation duration on the probability of sperm transfer and the number of sperm transferred, with implications for the evolution of extreme sexual size dimorphism and sexual cannibalism in orb weavers.

Morphometric Identification of Queens, Workers and Intermediates in In Vitro Reared Honey Bees (Apis mellifera).

In vitro rearing is an important and useful tool for honey bee (Apis mellifera L.) studies. However, it often results in intercastes between queens and workers, which are normally are not seen in hive-reared bees, except when larvae older than three days are grafted for queen rearing. Morphological classification (queen versus worker or intercastes) of bees produced by this method can be subjective and generally depends on size differences. Here, we propose an alternative method for caste classification of female honey bees reared in vitro, based on weight at emergence, ovariole number, spermatheca size and size and shape, and features of the head, mandible and basitarsus. Morphological measurements were made with both traditional morphometric and geometric morphometrics techniques. The classifications were performed by principal component analysis, using naturally developed queens and workers as controls. First, the analysis included all the characters. Subsequently, a new analysis was made without the information about ovariole number and spermatheca size. Geometric morphometrics was less dependent on ovariole number and spermatheca information for caste and intercaste identification. This is useful, since acquiring information concerning these reproductive structures requires time-consuming dissection and they are not accessible when abdomens have been removed for molecular assays or in dried specimens. Additionally, geometric morphometrics divided intercastes into more discrete phenotype subsets. We conclude that morphometric geometrics are superior to traditional morphometrics techniques for identification and classification of honey bee castes and intermediates.

Correlation of queen size and spermathecal contents and effects of miticide exposure during development

Normal mating of honey bee (Apis mellifera L.) queens and drones results in extreme polyandry. Larger queens are reported to produce more brood, but do they also store more semen? Measurements of queen weight, spermatheca weight and volume, and numbers of sperm in the spermatheca were made on normally reared queens and queens exposed to miticide from early larval stage to emergence. In the normally reared group, larger queens had more sperm in spermathecae of greater volume and weight. The presence of miticide during queen development skewed the relationship of queen weight to spermatheca size and the number of sperm stored such that they were not correlated. This sublethal effect of miticide in the colony has an unknown impact on queen performance.

Sexual Maturity Time and Spermatheca Size of the Bumblebee Bombus ignitus at Mating for Artificial Insemination

We investigated the mating age for sexual maturity of the bumblebee Bombus ignitus queens and males. In the mating age of sexual maturity of queen, mating rate was 1.1% at 3 days of emergence, peaked 24.7% at 20 days of emergence, and decreased thereafter. In case of mating age of sexual maturity of male, mating rate was 3.3% at just emergence and 20.0% to 43.3% at 6 days to 20 days of emergence. The colony development at aging of B. ignitus queen and male was a similar tendency to the mating age of sexual maturity. The age and copulation times of B. ignitus male were older and more, the copulation duration was longer. In case of multiple mating, B. ignitus was mated by 4 times, mating was mostly showed a peak at 9 to 11 AM, which was 70.5%. The number of ovum per ovariole in ovarium in non‐ mated and mated queens was 4.13 and 4.29, respectively at 10 days of emergence, and decreased thereafter. The number of ovum per ovariole of mated queens was a little more than that of non‐ mated queens. The size of spermatozoa of B. ignitus queen was a similar tendency to the number of ovum per ovariole. Our results indicate that period favorable for artificial insemination of B. ignitus was from 6‐10 days after emergence for queen and 9‐20 days after emergence for male.

Clinal nature of the frequencies of ovarioles and spermathecae in Cape worker honeybees,Apis mellifera capensis

It was determined that 300 Cape workers, Apis mellifera capensis (collected from each of 6 colonies at each of 5 localities about 200 km apart along an 800 km transect in the Western and Eastern Cape Provinces, South Africa) was the sample size required to statistically estimate the proportions of workers with spermathecae at each location at 95% confidence levels. Because of the extremely clinal nature of this honeybee population, we tested the hypotheses that (1) ovarian number and development of the spermatheca covary in Cape workers, and (2) covary clinally as well. A regression analysis revealed that the frequencies of bees with spermathecae significantly decreased from west to east, with Stellenbosch having the highest and Grahamstown the lowest frequencies. Spermatheca size also significantly decreased from west to east. A multiple regression analysis revealed that the number of ovarioles significantly decreased from west to east and also differed significantly between workers with and without a spermatheca. Moreover, the number of ovarioles was significantly correlated with the size of the spermatheca and workers without it had significantly fewer ovarioles. Both hypotheses are confirmed. The outcomes of these measurements will provide a more quantitative basis for estimates of effective social parasitism among these bees along a geographic continuum.

Evolution of specialized spermatheca morphology in ant queens: Insight from comparative developmental biology between ants and polistine wasps

In many ant species, the queens can keep spermatozoa alive in their spermatheca for several years, which goes along with unique morphological characteristics of the queen's spermatheca. The relative spermatheca size in ant queens is prominently larger than that in social wasps. Furthermore, the epithelium lining the spermatheca reservoir of ants consists of columnar cells in the hilar region and squamous cells in the distal region, whereas it is formed by columnar cells only in social wasps. To study the evolution of the unique spermatheca morphology in ant queens, we compared the various processes during spermatheca development between two ponerine ant species of the genus Pachycondyla (= Brachyponera) and three polistine wasp species of the genus Polistes. From histological observations, we can define four developmental events in the ant queens: (1) invagination of the spermatheca primordium, (2) the reservoir wall thickness becomes unequal, (3) the reservoir diameter doubles as the lining epithelial cells become flattened except for the hilar region, and (4) the increase in thickness of the reservoir epithelium is limited to the hilar region which doubles in thickness. In polistine wasps, the second and the third developmental events are absent and the entire epithelium of the spermatheca wall becomes thick in the final step. We therefore conclude that for ant queens the second and third steps are crucial for the enlargement of the spermatheca size, and that the second to the fourth steps are crucial for the specialization of the reservoir wall structure.

Inheritance of Traits Associated with Reproductive Potential in Apis mellifera capensis and Apis mellifera scutellata Workers

When workers of the thelytokous Cape honeybee, Apis mellifera capensis, come into contact with colonies of the neighboring arrhenotokous subspecies Apis mellifera scutellata, they can become lethal social parasites. We examined the inheritance of 3 traits (number of ovarioles, number of basitarsal hairs, and size of spermatheca) that are thought to be associated with reproductive potential in A. m. capensis workers. To do so, we produced hybrid A. m. scutellata/A. m. capensis queens and backcrossed them to either A. m. capensis or A. m. scutellata drones. We then measured the 3 traits in parental, hybrid, and backcross offspring. We show that the 3 traits are phenotypically correlated. We also show that the expression of ovariole number, basitarsal hairs, and size of spermatheca is influenced by the genotype of the individual and the rearing environment but that the influence of the rearing environment is less important to the number of ovarioles. We hypothesize a single recessive allele (l), present at high frequency in natural A. m. capensis populations, which when homozygous causes larvae to elicit more food. This increased feeding as larvae causes resulting adult workers to develop more queen-like morphology and increased reproductive potential. The number of ovarioles, in contrast, appears to be under independent genetic control.

Quantitative genetic correlation between trait and preference supports a sexually selected sperm process.

Sperm show patterns of rapid and divergent evolution that are characteristic of sexual selection. Sperm competition has been proposed as an important selective agent in the evolution of sperm morphology. However, several comparative analyses have revealed evolutionary associations between sperm length and female reproductive tract morphology that suggest patterns of male-female coevolution. In the dung beetle Onthophagus taurus, males with short sperm have a fertilization advantage that depends on the size of the female's sperm storage organ, the spermatheca; large spermathecae select for short sperm. Sperm length is heritable and is genetically correlated with male condition. Here we report significant additive genetic variation and heritability for spermatheca size and genetic covariance between spermatheca size and sperm length predicted by both the "good-sperm" and "sexy-sperm" models of postcopulatory female preference. Our data thus provide quantitative genetic support for the role of a sexually selected sperm process in the evolutionary divergence of sperm morphology, in much the same manner as precopulatory female preferences drive the evolutionary divergence of male secondary sexual traits.

Expandable spermatheca influences sperm storage in the simultaneously hermaphroditic snail Arianta arbustorum

Summary In many simultaneously hermaphroditic land snail species, the sperm storage organ (spermatheca) is highly structured, suggesting that the female function might be able to influence offspring paternity. Physical properties of the sperm storage organ, including its initial size and sperm storage capacity, may also affect fertilization patterns in multiply mated snails. We examined the structure, volume and tubule length of empty spermathecae in the land snail, Arianta arbustorum, and assessed differences in spermatheca size following a single copulation. The number of spermathecal tubules ranged from 2–7, but was not correlated with the volume of empty spermathecae. The volume of sperm stored in the spermatheca after a copulation was correlated with neither the number of spermathecal tubules nor copulation duration. Mean spermathecal volume more than doubled between two and thirty-six hours after sperm uptake, but the length of the spermathecal tubules did not change. Interestingly, the volume of sperm stored in the spermatheca seems not to be related to the size of the spermatophore and thus not to the number of sperm received (= allosperm). The amount of allosperm digested in the bursa copulatrix was highly variable and no significant relationship with the size of the spermatophore received was found. These findings suggest that numerical aspects of sperm transfer are less important in influencing fertilization success of sperm in A. arbustorum than properties of the female reproductive tract of the sperm receiver.

Apis mellifera capensis: an essay on the subspecific classification of honeybees

The history of the classification of Apis mellifera capensisis traced. The distributions of the traits thelytoky, ovariole number and spermatheca size of workers are given. Thelytoky in workers extends over 240 000 km 2 and the ratio of female/male progeny in laying worker offspring is clinal. Ovariole numbers are also clinal but spermatheca size is not. Allozymically, southern African honey- bees are homogeneous; but differ in mtDNA haplotypes and nuclear DNA diversity. Morphometric analyses yield three distinct morphoclusters (A. m. capensis, m. scutellata, and unnamed mountain bees). Conventional morphometric classification is incongruous with the mode of parthenogenesis and distribution of mtDNA and nuclear DNA diversity in the honeybees of southern Africa. The terms A. m. and A. m. are only meaningful if the precise geographical origins of the bees are specified. Apis mellifera capensis / Apis mellifera scutellata / classification / biogeography / thelytoky

Spermatheca size differentiation between queens and workers in primitive ants

Spermatheca size differentiation between queens and workers in primitive ants

Spermatheca Size Differentiation Between Queens and Workers in Primitive Ants

Spermatheca Size Differentiation Between Queens and Workers in Primitive Ants