Number Of Spermatophores Research Articles

Effect of X-ray irradiation on the biological parameters of Xestia c-nigrum.

The sterile insect technique (SIT) is widely used to control Lepidopteran pests by inducing inherited sterility. The noctuid moth Xestia c-nigrum is a polyphagous pest whose subterranean larvae severely injure cereals and some vegetables. The goals of this study were to assess the impact of X-ray irradiation on the development and survival of X. c-nigrum and use the data to select suitable sterilizing doses for potential future use in pest management. Batches of male pupae were exposed to 0 (control), 10, 30, 50, 100, 200, 300, or 400Gy of X-rays, approximately 24h before adult emergence. Exposure of late-stage pupae to 10-200Gy of radiation had no significant effect on adult emergence, but all doses (10-400Gy) reduced adult longevity, the number of spermatophores in mated females, and the number of eggs laid per female in the irradiated parental generation compared with the controls. Exposure to 10 and 30Gy had no significant effects in the F1 generation on 1) the rate of egg hatch, 2) the duration of larval or pupal development, or 3) adult longevity. However, exposure to 50Gy reduced the rate of egg hatch in the F1 generation, and when male pupae were exposed to 100Gy only 1% of the F1 eggs hatched. Also at 100Gy, the developmental durations of larvae and pupae were significantly prolonged, and longevity of adult moths was reduced. There were no significant differences between the control group and any treatments in 1) the sex ratio of the F1 adults, 2) the duration of F1 pre-oviposition or oviposition periods, or 3) the number of eggs laid per F1 female. Our findings indicate that a dose of 100Gy can effectively slow pest development and reduce larval survival in the F1 generation. In addition, F1 adults from lines treated with 100Gy were able to mate and lay eggs, but all F2 eggs failed to hatch. Our results suggest that use of X-ray irradiation has potential to control this polyphagous pest at the regional level.

Multiple paternity in the invasive spotted lanternfly (Hemiptera: Fulgoridae).

In biological invasions, multiple paternity can preserve genetic diversity over time and space and contribute to invasion success. Therefore, knowledge on the mating system of invasive species is essential to develop adequate management practices to mitigate their impact on ecosystems. The spotted lanternfly, Lycorma delicatula (White, 1845), is an invasive pest that has colonized more than 10 eastern US states in less than 10 yr. Multiple paternity may contribute to its success, but little is known about spotted lanternfly's mating system. We explored the mating system using mated females and female-egg mass pairs sampled in the field. First, we assessed the existence of multiple mating by counting the number of spermatophores in the genital tract of all females. Second, we searched for genetic evidence for multiple paternity within egg masses by genotyping the female-egg mass pairs at 7 microsatellite loci. Third, we assessed whether multiple mating was correlated with female traits and distance from the introduction site. One to 3 spermatophores per female were found during dissections, confirming the existence of polyandrous female spotted lanternfly. We found genetic evidence for a minimum of 2 fathers in 4 egg masses associated with polyandrous females, validating multiple paternity in spotted lanternfly. Multiple paternity was associated with egg mass size, and multiple paternity was highest in populations closest to the original introduction site and decreased toward the invasion front. Multiple paternity may contribute to the invasion success of spotted lanternfly, and control efforts should consider the mating system and the implications of its spatial patterns.

Reproductive Biology of the Golden Cuttlefish Sepia esculenta (Cephalopoda, Sepiida)

The golden cuttlefish Sepia esculenta is the one of most abundant cuttlefish species around south-east Asia and has a high commercial value. Despite its wide distribution and high commercial value, its reproductive biology is still poorly understood. This study was based on 25 males and 6 females. The potential fecundity (PF) of females was 1701–3719 oocytes, which was an increase, as compared to the previously known values. The oocyte resorption reached up to 13.2% of fecundity. The ovulation pattern was group-synchronous, with a predominance of previtellogenic oocytes. The pre-meiotic and primary growth oocyte phases were absent in mature females. The number of spermatophores carried by an individual male was 146–1698 (length 9–20 mm). The spermatophores were characterised by a cement body consisting of conical oral and cylindrical aboral parts. The ontogenetic changes in the spermatophores and their parts were recorded for the first time in the order of Sepiida. Their sperm content and their adhesive abilities also increased during ontogenesis. The data obtained in the present study significantly increased and corrected the existing knowledge of S. esculenta biology. Moreover, these data help to explain the general patterns of reproductive biology in cuttlefish, as well as in Cephalopoda as a whole.

Cytopathological and ultrastructural changes in the male reproductive organs of freshwater crab Paratelphusa jacquemontii (Rathbun) exposed to nurocombi.

Accumulation of pollutants in the aquatic system has a high impact on the reproductive physiology of crustaceans. The objective of the present study was to assess the possible histopathological effects of combined chlorpyrifos and cypermethrin (nurocombi) exposure on reproductive tissue in male freshwater crab Paratelphusa jacquemontii using light and electron microscopy. The testis of experimental crabs showed disorganization of testicular lobules, increased inters cellular space, necrosis, and cellular damage in both germinal cells and Sertoli cells. The treated vas deferens exhibited epithelial degeneration, misshaped spermatophores, decline in the number of spermatophores, and dehiscence of spermatophore wall. These clinical manifestations expressed in crabs following the exposure of nurocombi significantly reduce the testicular activity and substantially inhibits the seminal secretions, which ultimately lead to impairment of reproduction.

Criopreservación espermática de Ambystoma mexicanum (Shaw & Nodder, 1798)

Ambystoma mexicanum is in danger of extinction in free-living, due to anthropogenic actions; sperm cryopreservation for captive breeding can help in its ex-situ conservation. This research aimed to identify the viability of fresh and post-thawing sperm from different spermatophores. During the breeding season, spermatophores releasing was induced in nine specimens by reducing water temperature. The mean concentration per spermatophores was 2.6 ± 0.6 x104 sperm. A reduction of 30 % of living sperms and an increase of 15 % of abnormal morphology were determined in fresh and post-thawing sperm. With the WGA and PNA lectins bounded to FITC, two different fluorescence patterns were determined in each one, which showed the membrane presence and distribution of N-acetyl glucosamine, sialic acid, and mannose respectively. Sperm percentages in each fluorescence pattern showed differences associated with the number of spermatophores in each release. Differences in sperm viability from releases with different numbers of spermatophores were determined. The sperm collection and cryopreservation protocol of A mexicanum were efficient as tools for using cryopreserved semen for ex situ reproduction.

Artificial extrusion of spermatophores for insemination of the narrow-clawed crayfish Pontastacus leptodactylus (Eschscholtz, 1823)

The extrusion of spermatophores using electrical stimulation and dissection techniques from the vas deference was performed to test the feasibility of artificial insemination in Pontastacus leptodactylus. The electrical stimulation to males showed a significant success of 66.6%. The rate of spermatophore ejaculation was affected by male size (P < 0.05). Higher number of spermatophores and percentage of spermatophore ejaculation were observed in large (> 6.5cm carapace length) males (1.4 ± 0.1; 92.3%) compared to medium (5.5–6.5 cm carapace length) (1.1 ± 0.1; 75%) and small (< 5.5 cm carapace length) males (0.6 ± 0.2; 33.3%). It was found that the extrusion technique did not affect spermatozoa viability (P > 0.05). Viability was 80.4 ± 2.2% and 83.8 ± 1.9% for electrical stimulation and dissection techniques, respectively. The spawning rate was 100% in inseminated females using spermatophores obtained from the dissected males. Using electrical extrusion, not enough spermatozoa were obtained to induce spawning in female P. leptodactylus. Further studies are needed to improve the outcome of the electrical extrusion technique. The present study represents a step forward for the development of artificial insemination in P. leptodactylus.

Anti‐insect defenses of Achnatherum robustum (sleepygrass) provided by two Epichloë endophyte species

AbstractMany pooid grasses (Poaceae) harbor Epichloë species (Hypocreales), endophytic fungi that often produce toxic alkaloids which may provide anti‐insect protection for their hosts. Two natural populations of Achnatherum robustum (Vasey) (sleepygrass), in the Lincoln National Forest, Cloudcroft, and Weed (NM, USA), are infected with the endophyte species Epichloë funkii (KD Craven &amp; Schardl) JF White and Epichloë sp. nov. We tested whether: (1) these endophytes affect survival, growth, and development of the insect herbivore Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) (fall armyworm), (2) larval diets alter adult fecundity (assessed as number of larvae or eggs produced by females and number of spermatophores that males transfer to females when enclosed in pairs within each feeding group), and (3) infections affect leaf consumption in larval no‐choice and choice experiments. Individual larvae were reared on Epichloë infected vs. uninfected clipped leaves from the Cloudcroft and Weed population plants. Overall, armyworm survival was not affected when fed infected sleepygrass from either population. However, larvae that fed on Weed‐infected plants were smaller and had longer development than larvae that fed on uninfected and Cloudcroft‐infected plants. Males fed on Weed‐infected leaves had reduced mating success. Interestingly, pupal mass increased when larvae fed on either the infected leaf types. However, heavier females from both infected diets did not lay more eggs than lighter females from uninfected diets. In a no‐choice test, larvae on Weed‐infected plants diet consumed more leaf biomass than larvae from three other groups. In choice tests, larvae avoided feeding on leaves infected with either of the endophytes relative to uninfected leaves. Thus, the two Epichloë may provide direct protection to sleepygrass from insect herbivory by deterrence. The Weed population endophyte may provide stronger indirect protection than the Cloudcroft endophyte by reducing insect fitness or increasing risks of predation and parasitism through delayed development, even though larvae may consume more leaf biomass.

Seasonal changes in reproductive traits and paternity in the Japanese pygmy squid Idiosepius paradoxus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 582:121-131 (2017) - DOI: https://doi.org/10.3354/meps12338 Seasonal changes in reproductive traits and paternity in the Japanese pygmy squid Idiosepius paradoxus Noriyosi Sato1,2,* 1Graduate School of Fisheries Science and Environmental Studies, Nagasaki University, Nagasaki, Japan 2Present address: Oki Marine Biological Station, Shimane University, Shimane, Japan *Corresponding author: norico3000@gmail.com ABSTRACT: Sperm production in males and sperm storage in females can change over an individual’s reproductive timespan. This implies that the strength of sperm competition may also change with time. The seasonal pattern of reproductive traits and paternity in the Japanese pygmy squid, which has 2 life-history types (large and small types having long and short reproductive periods, respectively), were compared among 3 reproductive periods: early and late reproductive period of the large type and middle reproductive period of the small type. Although the gonad somatic index (GSI) decreased during one of the reproductive periods in males, the number of spermatophores and the spermatophoric complex somatic index (SCSI) increased. The GSI was higher in large-type males, whereas the SCSI was higher in the small type. Multiple paternity was detected in all egg masses, and on average about 10 males were estimated to be sires in a single egg mass. Paternity numbers differed significantly between life-history types, whereas there were no significant differences between the early and late reproductive periods in the large type. These results imply that the Japanese pygmy squid is polyandrous and exposed to a very high level of sperm competition risk. Paternity numbers did not change during reproductive periods even when the reproductive traits changed between these periods. Seasonal changes in reproductive traits may have a minor effect on paternity in promiscuous animals. However, 2 life-history strategies were observed: large-type males, invested in transferring more sperm to one female, and small-type males that stored more spermatophores to copulate with many females. KEY WORDS: Cephalopod · Microsatellites · Parentage · Multiple paternity · Seasonal change Full text in pdf format PreviousNextCite this article as: Sato N (2017) Seasonal changes in reproductive traits and paternity in the Japanese pygmy squid Idiosepius paradoxus. Mar Ecol Prog Ser 582:121-131. https://doi.org/10.3354/meps12338 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 582. Online publication date: November 06, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Biology and reproductive traits of Drymoea veliterna (Druce, 1885) (Lepidoptera: Geometridae)

Despite the urban and landscape impact caused by Drymoea veliterna (Druce, 1885) (Lepidoptera: Geometridae) larvae on trees of the genus Croton L. (Euphorbiaceae) in the Neotropics, there is no information about its biology and reproductive traits. In this study, we describe the life cycle and reproductive traits of this species. Its life cycle lasts approximately 56 days, the larvae develop during 24 days on average and the longevity of the females is 7 days on average. Females have an average fecundity of 207 eggs. Regarding their reproductive system, the presence of previtellogenic eggs in the reproductive tract of the females is emphasized. The bursa copulatrix and a highly sclerotized signum is depicted. The number of spermatophores found in the reproductive tract of the females was quantified. Male and female genitalia were schematized.

Do Male Cook Strait Giant Weta Prudently Allocate Sperm?

Sperm production is costly and so males are expected to prudently allocate sperm to matings in a manner that maximizes their fitness. Sperm competition hypotheses predict that when facing increased sperm competition risk males should increase their investment in ejaculates. In contrast, when facing high future mating opportunities, males are expected to decrease their sperm investment in the current mating. This is because males should keep in reserve an amount of sperm proportional to their expected future mating opportunities. We experimentally tested whether male Cook Strait giant weta (Anostostomatidae: Orthoptera: Deinacrida rugosa) phenotypically adjust their investment in ejaculates in relation to their perceived risk of sperm competition and future mating opportunities. D. rugosa is a large flightless orthopteran insect in which males pass multiple spermatophores to females during a day-long mating bout. Contrary to expectation, we found that low female availability (i.e. increased sperm competition risk) had no effect on male resource allocation to sperm (i.e. number of spermatophores) compared to controls whereas, contrary to expectation, males experiencing high female availability increased their ejaculate investment by transferring significantly more spermatophores to their mates. Our results might be a consequence of males being insensitive to increased presence of rival males, reducing their allocation to sperm under increasingly risky circumstances, or due to females prolonging copulations when their perceived future mating opportunities are low.

Growth and maturity of the spider crab Halicarcinus planatus (Brachyura: Hymenosomatidae) females in the southwestern Atlantic Ocean. Can these parameters be influenced by the population sex ratio?

ABSTRACTThe Halicarcinus planatus populations of the southwestern Atlantic Ocean show a highly variable sex ratio and a large size overlapping between females in the last immature instar (ADO) and mature (MAT) females. We hypothesized that these facts are related and that female impregnation has a central role in this relation. Non-impregnated ADO females delay maturity and would continue to grow, leading to size overlapping. This scenario is most probable in populations with a scarcity of males and could affect the growth, maturity and population structure. The sex ratio and female size distribution of several populations of the southwestern Atlantic Ocean were analysed. Growth and maturity were studied in two populations with different sex ratios (Camarones, a population with males, and Rada Tilly, a population where no males were found). Size overlapping was not related to the population sex ratio. Size overlapping was due to a variable moult increment and, to a lesser extent, to delayed maturity. Females mated before terminal moult in both populations. However, in Camarones, physiological maturity was not related to impregnation, while in Rada Tilly, vitellogenic oocytes were observed only in impregnated females. Also, differences in the number of spermatophores in female spermathecae were related to the sex ratio. Our results showed that the morphological maturity pattern of females was not influenced by the population sex ratio. However, physiological maturity was related to female impregnation and sex ratio. Also, the variation in the number of spermatophores suggests differences in the mating system related to the sex ratio.

The effect of predation risk on spermatophore deposition rate of the eriophyoid mite, Aculops allotrichus.

Eriophyoids are minute herbivores in which males deposit spermatophores on a substrate while females, independent of the presence of males, pick up sperm (sex dissociation). Their most dangerous enemies are phytoseiid mites. Eriophyoids can successfully avoid the predation by, e.g., forming galls in which they live, by inhabiting narrow spaces on plants, or by climbing up leaf trichomes for the time of quiescence. All these behaviours, however, are fixed and independent of the actual risk of predation. The aim of this study was to examine whether eriophyoids can respond to the cues of predation risk and how this could affect their spermatophore deposition rate. Aculops allotrichus is a vagrant eriophyoid which inhabits leaves of the black locust tree, Robinia pseudoacacia. On leaf arenas with injured conspecifics (pierced with a fine needle which simulated the attack of phytoseiids), single males of Ac. allotrichus deposited a similar number of spermatophores as on control, ‘clean’ leaves. They did not respond to the cues left by the non-enemy, yeast-fed acarid mite Tyrophagus putrescentiae either. However, they deposited significantly fewer spermatophores on leaf arenas previously exposed to the presence of the eriophyoid-fed phytoseiid mite Amblyseius swirskii. This is a first report indicating that eriophyoids can respond to the cues left by predators and change their reproductive activity accordingly. The ultimate and proximate factors that may influence the behaviour of Ac. allotrichus males are discussed.

Indicators of recent mating success in the pipevine swallowtail butterfly (Battus philenor) and their relationship to male phenotype

A key determinant of the intensity of sexual selection acting on a trait is how variation in that trait is related to variance in reproductive success of individuals. This connection compels efforts to assess lifetime mating number and how it varies among individuals in a population. In the Lepidoptera, female mating success can be assessed relatively easily by counting by the number of spermatophores in the female’s copulatory sac but male mating success in the field can often only be documented by observing copulations. Here we report a method for identifying whether or not males have recently mated that relies on the effect of mating on the appearance of the male’s reproductive tract in the pipevine swallowtail, Battus philenor. In this species laboratory experiments reveal that during mating, components of a male’s reproductive tract become shorter, decrease in mass, and change in appearance, irrespective of male age. These changes persist for at least two days after mating. After documenting these indicators of recent mating, we examined the reproductive tract of 68 field-caught males and found that twelve (17.6%) showed strong evidence of having mated recently. We found that older males were more likely to have recently mated. In addition, the color of the dorsal hindwing, a feature that females use in mate choice, was significantly greener in males, that according to our criteria, had recently-mated than in males that had not.

INFLUENCE OF LARVAL FOOD ON NUMBER OF SPERMATOPHORES, FECUNDITY AND SOME BIOCHEMICAL PARAMETERS OF THE SPINY BOLLWORM, Earias insulana (BOISD.)

Experiments were carried out to study the effect of larval food types (cotton bolls, okra pods and artificial diet) on number of spermatophores, fecundity and total soluble protein, lipid and carbohydrate contents of the spiny bollworm, Earias insulana (Boisd.). The obtained results showed that the larvae reared on artificial diet gave the highest weight, while, those collected from cotton bolls gave the lowest weight. The lowest pupal mortality percentage and the highest adult emergence percentages, number of eggs/female and hatchability percentages recorded for the larvae obtained from artificial diet followed by those collected from okra pods and cotton bolls. Pupal duration, pre & post- oviposition periods and male longevity were differed insignificantly as affected by feeding larvae on okra pods, cotton bolls and artificial diet. The newly emerged female moths from larvae collected from cotton bolls were recorded the lowest mean number of the eggs/ovariol and spermatophores, while, those emergence from larvae obtained from artificial diet was recorded the highest one. The highest value of total soluble protein, lipid and carbohydrate contents were recorded in larvae obtained from artificial diet followed by those collected from okra pods and cotton bolls.

Histological alterations of a combination of Chlorpyrifos and Cypermethrin (Nurocombi) insecticide in the fresh water crab, Paratelphusa jacquemontii (Rathbun)

Chlorpyrifos (CPF) and Cypermethrin (CPM) are toxic and subject to long-term in vivo accumulation in different aquatic species throughout the world. The purpose of the present study was to examine the combined CPF/CPM (Nurocombi) exposure on histology in various tissues of Paratelphusa jacquemontii. The crabs were exposed to combined CPF/CPM concentrations of 0.0187ppm and 0.0374ppm (sub lethal) for 28days with parallel untreated control. The experimental gill tissue exhibited epithelial lifting, edema, necrosis, fusion of secondary lamellae and hemorrhage. The deceased hepatopancreas revealed infiltration, formation of large lumen and disappearance of haemocytes. The pathologic symptoms like atrophy, necrosis, wavy appearance, accumulation of granular material in between muscle fibers, fragmentation, loss of muscle structure, appearance of basophilic deposits were displayed in the muscle tissue. The vas deferens showed remarkable epithelial vacuolar degeneration, irregular appearance of spermatophore matrix associated with reduction in the number of spermatophores and dehiscence of most of the spermatophores. It is concluded that histological biomarkers provide reliable and discriminatory data to augment pesticide pollution and therefore, long-term monitoring is necessary to assess the eco-health of the mangrove system.

Estimates of female lifetime fecundity and changes in the number and types of sperm stored with age and time since mating in the monandrous swallowtail butterfly, Battus philenor (Lepidoptera: Papilionidae) in the Arizona desert

The role of apyrene sperm in monandrous species after sperm migration to the spermatheca has not been studied, though in polyandrous species these sperm reduce re-mating receptivity. We studied the relationship between apyrene sperm numbers and age, mating history, and fecundity in females of the monandrous pipevine swallowtail butterfly, Battus philenor (L.) that were collected in the desert of central Arizona. The number of spermatophores in the bursa copulatrix and the eggs in the ovaries were counted and their relationship to female age (as indicated by wing wear) was examined. The mean number of spermatophores in the oldest females was 1.4, confirming that this species is monandrous. Average female fecundity was estimated at 430 from counts of eggs in the ovaries. Recently mated females stored many more eupyrene sperm in the spermatheca than the number of eggs in the ovaries. Apyrene sperm were also found in the spermatheca of the females with a long period elapsed after the mating, as indicated by a collapsed spermatophore. The potential role of apyrene sperm and the effect of body size on the fecundity in monandrous species is mentioned.

Spermatophore production as a function of food abundance and age in the calanoid copepods, Acartia tonsa and Acartia hudsonica

Lifetime spermatophore (sperm packet) production, which can provide valuable information about male energetics and mating, is not known for any species of copepod. Spermatophore production could limit reproduction in species in which females require multiple matings to remain fertilized and in populations that often have adult sex ratios highly skewed toward females. Spermatophore production rates were measured in the laboratory for two species of calanoid copepods, Acartia tonsa and Acartia hudsonica, from time of maturation until death, and under three food regimes (high, low, and no food). Rates of spermatophore production in A. tonsa were independent of food treatment. By contrast, in A. hudsonica, spermatophore production was significantly greater under high food than in low or no food. Spermatophore production decreased significantly with age in both species and the majority of males ceased producing spermatophores halfway through their adult lives. This pattern occurred regardless of food treatment, except for in A. hudsonica under low-food conditions: low production rates in younger males were compensated by continued reproduction into old age. Therefore, there was no difference in the total lifetime number of spermatophores produced by males of A. hudsonica fed at high- or low-food conditions. In the absence of food, however, significantly fewer spermatophores were produced. In A. tonsa, there was no difference among food treatments in the total number of spermatophores produced over a male’s life. The effect of these low rates of spermatophore production on fertilization was evident in the field. During 2 years of weekly collections, at no point in time were all females in the population fertilized. We conclude that low rates of spermatophore production over a lifetime and the short reproductive period of males contribute to the low frequencies of mated females in field populations.

Mating opportunities in Sangalopsis veliterna females: costs and benefits.

In nature, females of several animal taxa exhibit considerable variation in their mating system, and this variation involves different balances of costs (e.g., energetic, reproductive) and benefits (e.g., increased net reproductive rate of the female, increased longevity). Many studies have focused on discovering the potential advantages and disadvantages that females could have when increasing their mating rate and the possible evolutionary consequences that may result. Butterflies and moths are an ideal study system because it is easy to determine and to manipulate experimentally their mating frequency. In this study, the effect of continuous availability of different numbers of males (1, 2, 4, 8) on female mating rate and fitness components was estimated by comparing the number of spermatophores in the corpus bursa (an estimate of the number of copulations, but not of the number males involved in these copulations), female longevity, lifetime number of laid eggs (fecundity), and proportion of hatching eggs (fertility) in the moth Sangalopsis veliterna Druce (Lepidoptera: Geometridae). The results showed that there were no significant differences in either fertility or fecundity when treatments were compared, but longevity and in some cases fecundity increased when females had several matings.

Male reproductive system and spermatophores production and storage in Histioteuthis bonnellii (Cephalopoda: Histioteuthidae): A look into deep-sea squids׳ reproductive strategy

Coleoid cephalopods go through a single breeding period in their life cycle, i.e., they are semelparous, although a great flexibility has been observed in their reproductive strategies, which range from simultaneous terminal spawning over a short period at the end of the animal׳s life to continuous spawning over a long period of the animal׳s life. So far, the information available on deep-sea species reproductive strategies is still poor and most of our knowledge about squid reproduction relates to females. In particular, not much is known on what strategy male squids have evolved to store sperm into spermatophores and adapt to semelparity. In this study an investigation of male reproductive strategy of the deep-sea umbrella squid Histioteuthis bonnellii (Férussac, 1835) is presented. The reproductive system was examined in 119 males caught in the Sardinian waters (Central Western Mediterranean) and is described for the first time. Results indicate that this species produces and stores spermatophores over a considerable period of time. The total number of spermatophores found in the reproductive system ranged between 12 and 3097 and the size of spermatophores stored by a single individual varied greatly, up to over 300%. Spermatophore length (SpL) gradually decreased towards the distal end of the reproductive system, so that spermatophores found in the proximal part of Needham׳s Sac were larger than those found in the terminal organ. Body size and SpL of spermatophores from the proximal part of Needham׳s Sac were positively correlated. Both indices of the sperm mass and of the ejaculatory apparatus decreased with the increase of SpL, while the cement body index increased, indicating that larger spermatophores contain less sperm and are equipped with larger cement bodies. Up to 64 spermatangia were found, exclusively in the terminal organ. The large size range of mature males (ML: 60.0–198.0mm; TW: 113.50–2409.00g) and the variation in spermatophore number and size indicate that in H. bonnellii males the allocation and storage of sperm start early in the individual life and extends in time, while animals continue to grow and produce spermatophores presumably more successful in attaching to female tissues. This pattern enlarges the time window available for reproduction and likely maximizes the percentage of mating success as the animals grow older and chances of mating events become comparatively lower, due to the basic low density of specimens in the deep-sea environment. Both aspects are potentially indicative of adaptation to the deep sea.

Male–male competition leads to less abundant but more attractive sperm

Males employ complex strategies to optimize their reproductive success when faced with male-male competition; for instance, they can adjust the ejaculate characteristics. In copulating species, a male may also strategically adjust his ejaculate expenditure according to female quality. Quantifying the relative contribution of ejaculate plasticity in male reproductive success is often difficult, especially when females exert postcopulatory cryptic choice. One way to quantify the functional significance of ejaculate plasticity is offered by mating systems in which the reproductive partners do not meet each other during insemination. In the collembolan Orchesella cincta, males deposit their ejaculates (spermatophores) irrespective of the presence of females. We tested whether Orchesella males adjust spermatophore number when exposed to the presence of another male and whether changes in spermatophore production influence female choice. We found that Orchesella males display plasticity in spermatophore allocation. Males decreased the spermatophore number when exposed to a rival male. Moreover, females preferentially took up spermatophores of males that were exposed to a competitor. The reduction in spermatophore number suggests, besides an adaptive response to the risk of ejaculate removal by rival males, an optimization strategy owing to the costs of more attractive spermatophores.