Sperm Translocation Research Articles

No fitness effects of same-sex copulations in male red flour beetles.

Same-sex sexual behavior occurs in diverse animal taxa, yet its evolutionary maintenance is poorly understood as such behavior seems to be costly and does not directly increase reproductive success. We used male Tribolium castaneum beetles, which frequently engage in same-sex copulations, to test if same-sex sexual behavior influences future male mating behavior and reproductive success of males. Furthermore, we tested whether same-sex sexual behavior has benefits via indirect sperm translocation. We conducted a series of mating trials demonstrating that males exposed to same-sex behavior did not sire less offspring compared to control males that did not engage in same-sex behavior. This suggests that same-sex copulations did not lead to fitness costs in subsequent mating interactions. In addition, we found no evidence that indirect sperm translocation via an intermediate male occurs in T. castaneum. Taken together, these results imply that same-sex sexual behavior in males is associated with no costs in terms of lower mating rate and reduced siring success and does not seem to entail benefits. Moreover, our data conform to the hypothesis that sexual indiscrimination is prevalent in this species, which may explain the relatively high frequency of same-sex sexual behavior in T. castaneum.

Demographic Traits and Behavior of Hetaerina cruentata (Odonata: Calopterygidae) in Ecosystems of the Andean Region of Colombia

Demography and territorial behavior of Hetaerina cruentata was studied along three lowland streams located at Norte de Santander department in the Colombian Andean region. Adult damselflies (N: 278) were individually marked, and using their recapture histories we estimated survival, longevity, sex ratio, age groups and population size at each location. We found no evidence for survival differences between ages and sexes. However, the proportion of resighted individuals was lower for females, and the sex ratio was male-biased in all populations. Although we recorded few reproductive events, a high number of male-male agonistic interactions were registered around midday. During reproductive behavior, we observed brief wing displays as signals between males and females, and the formation of the tandem position, followed by the intra-male sperm translocation and copulation (mean duration 11.3 min). After copulation, the pair in tandem looked for suitable sites to oviposit, and then the male broke tandem and perched on the vegetation while the female laid eggs partially or completely underwater. The recapture probability was time-dependent, which suggests that the alternation of rainy and sunny days during the study may be generating differences in the demography of the three H. cruentata populations.

Variation in intraspecific sperm translocation behaviour in a damselfly and its consequences for sperm viability

Sperm quality and viability affect both male and female fitness. Most dragonfly and damselfly males translocate sperm from the testis to the seminal vesicle before each copulation, a behaviour known as intramale sperm translocation (ST). However, some published observations indicate that odonate males can occasionally skip ST prior to copulation. Our aim was to determine the circumstances under which males skip ST and how this might affect sperm viability. We allowed males of the damselfly Ischnura graellsii to perform ST (interrupting the copulation at this stage) and we studied ST behaviour during subsequent copulation. Males were randomly assigned to four treatments, which consisted of allowing the experimental male to copulate again 15 min or 1–3 days after his last ST. Fertility of females mated with the experimental males was analysed as a proxy for sperm viability. All males used the sperm that they translocated previously when the second mating took place 15 min after the manipulation, while the proportion of males that repeated ST increased steadily over time. Both treatment (time elapsed since last ST) and the interaction between treatment and ST (yes/no) had a significant effect on fertility, which decreased only in males that did not perform ST immediately before copulation. Additional experiments with damselflies of the genus Calopteryx showed also that males did not repeat ST when the time to the next copulation was less than a day. Our results suggest that sperm quality decays over time in odonates, and that males can choose whether to keep and reuse the sperm in the seminal vesicle or to discard it. We conclude that the special anatomical disposition of odonate males might increase selective pressures to maximize sperm viability and/or repeated intramale ST behaviour. • Males reused vesicle sperm when copulating 15 min after sperm translocation (ST). • The proportion of males that repeated ST increased over time. • Female fertility decreased with increasing time between ST and copulation. • Males seem to be able to detect whether their sperm vesicle is full or not.

Regulation of boar sperm functionality by the nitric oxide synthase/nitric oxide system

PurposeNitric oxide (NO) is a free radical synthesized mainly by nitric oxide synthases (NOSs). NO regulates many aspects in sperm physiology in different species. However, in vitro studies investigating NOS distribution, and how NO influences sperm capacitation and fertilization (IVF) in porcine, have been lacking. Therefore, our study aimed to clarify these aspects.MethodsTwo main experiments were conducted: (i) boar spermatozoa were capacitated in the presence/absence of S-nitrosoglutathione (GSNO), a NO donor, and two NOS inhibitors, NG-nitro-L-arginine methyl ester hydrochloride (L-NAME) and aminoguanidine hemisulfate salt (AG), and (ii) IVF was performed in the presence or not of these supplements, but neither the oocytes nor the sperm were previously incubated in the supplemented media.ResultsOur results suggest that NOS distribution could be connected to pathways which lead to capacitation. Treatments showed significant differences after 30 min of incubation, compared to time zero in almost all motility parameters (P < 0.05). When NOSs were inhibited, three protein kinase A (PKA) substrates (~ 75, ~ 55, and ~50 kDa) showed lower phosphorylation levels between treatments (P < 0.05). No differences were observed in total tyrosine phosphorylation levels evaluated by Western blotting nor in situ. The percentage of acrosome-reacted sperm and phosphatidylserine translocation was significantly lower with L-NAME. Both inhibitors reduced sperm intracellular calcium concentration and IVF parameters, but L-NAME impaired sperm ability to penetrate denuded oocytes.ConclusionsThese findings point out to the importance of both sperm and cumulus-oocyte-derived NO in the IVF outcome in porcine.

The evolution and diversity of intra-male sperm translocation in Odonata: a unique behaviour in animals

Behavioural diversity is a basic component of biodiversity, with implications in ecological interactions at the intra- and interspecific levels. The reproductive behaviour of Odonata (dragonflies and damselflies) is unique among insects and conditioned by the anatomical separation between the male’s reproductive organs and the intromittent organ. Prior to mating, males must translocate sperm from the genital pore in the ninth abdominal segment to the seminal vesicle located ventrally in the second abdominal segment. This behaviour, exclusive to odonates, is known as intra-male sperm translocation (ST). Here, we review the literature on ST and use phylogenetic comparative analyses to investigate the evolution of ST within the Odonata. Information on ST was compiled for 176 species, with the commonest variant being ST once per mating, after tandem formation (66%). Other variants found were ST involving precopulatory genital touching (10%), ST by the male alone before tandem (16%) or after copulation (5%), and repetition of ST during the same copulation (3%). The precopulatory genital touching might have evolved to detect female receptivity. ST before tandem formation might be favoured when mating opportunities are scarce and copulations are brief. ST after mating might be favoured if males need to be ready to copulate fast. Finally, repeated ST could have evolved through postcopulatory sexual selection in males with limited sperm removal ability, as a means to improve their sperm competition. The most plausible scenario for the evolution of ST is that the ancestors of the Odonata produced a spermatophore and attached it to the body, leading towards the evolution of the secondary genitalia in males. Our study emphasises the role of behavioural diversity to understand behavioural evolution. Unique behaviours are exclusive of a few individuals, populations and/or species. The intra-male sperm translocation (ST) of dragonflies and damselflies is a unique behaviour in animals: before mating, males need to transfer sperm from the primary to the secondary genitalia, which are anatomically separated. Thus, the viability and quality of sperm (i.e. fertility) will depend on the timing of ST relative to copulation. Our literature review found a variety of ST variants, being ST in tandem and before copulation the ancestral strategy. We discuss putative evolutionary routes for all the variants found and emphasise the importance of retrieving detailed observations of such unique behaviours in the field, which could help to better understand behavioural evolution in this insect group. Behavioural diversity is rarely addressed by conservation strategies, despite unique behaviours being at a higher risk of extinction.

&lt;b&gt;Breeding behaviour of the Coromandel Damselfly &lt;I&gt;Ceriagrion coromandelianum&lt;/I&gt; (Fabricius) (Zygoptera: Coenagrionidae) in central India: copulation&lt;/b&gt;

The Coromandel Damselfly Ceriagrion coromandelianum can be easily identified because of its bright yellow abdomen, greenish thorax and eyes. In females, the abdomen is darker with light brown colouration extending to dark brown towards the terminal end. The documentation of the reproductive behaviour of Ceriagrion coromandelianum was carried out at the botanical garden of Hislop College, Nagpur, India. The males of C. coromandelianum arrive early in the morning by 07:00hr at the ovipositing site. They belong to “sit and wait” type of mate-location. While perched and waiting for the female to arrive they at times exhibit abdominal bobbing, and oviposition posture. The territorial area of male C. coromandelianum is very small, within a range of about 45cm around his perch. There is no precopulatory courtship display and the male move toward the arriving receptive female and directly tries to form a tandem link. The other males of the group follow the pair. The tandem pair flies towards the safety of the surrounding vegetation to copulate. Before copulation, the male fills his penis vesicle with sperm material by the process of “intra male sperm translocation” which lasts for 30±8 seconds. The female curves her abdomen ventrally forward so that her gonopore which is located between the eighth and ninth sternite comes to lie before the secondary copulatory apparatus of the male and forms a strong genital link, to form the copulatory wheel. The copulation duration can be long (34–55 min) or short (12–15 min). Two stages of copulation depending upon the pumping movement of the couple can be differentiated. During the first stage, the male rhythmically and forcefully depresses and stretches the first two abdominal segments, vigorously pumping the penis inside the female vagina which accounts for 72% of the copulation duration. The second stage starts with rapid short thrusting movement which are not forceful but exhibit shallow movements of the first two abdominal segment of the male. The tandem pairs after copulation may directly move for oviposition or settle around the surrounding foliage and exhibit “post-copulatory resting” (PCR) behaviour. It is noted that 23.3% females immediately commence oviposition, 53.4% exhibit brief, while 23.3% display prolonged PCR behaviour.

Kinesins in spermatogenesis.

Kinesins are essential for the proper function of many types of polar cells, including epithelial cells, neurons, and sperm. Spermatogenesis is closely associated with many different kinesins. These kinesins participate in several fundamental processes, including mitotic and meiotic division, essential organelle transport, and the biogenesis of peculiar structures for the formation of mature sperm. Kinesin-13, kinesin-8, and the chromokinesin families cooperate to ensure normal sister chromatid congression and segregation. The kinesin-8 family motor KIF18A, kinesin-12 motors PAKRP/kinesin12A and PAKRP1L/kinesin12B, and other kinesin-like motors are essential in the process of homologous chromosome pairing and in the separation to create haploid gametes. During spermiogenesis, the responsibility of a handful of kinesin members lies in the maturation of spermatids into mature, motile, and intact spermatozoa. Such roles are completed upon the release of viable and functional sperm into the lumen of seminiferous tubules. In this process, KIFC1, KIF5C, KRP3A, and KRP3B may be involved in acrosome biogenesis; KIFC1, KIFC5, CHO2, KIF17b, and KIF3A probably contribute to nuclear shaping; KIF17b, KIF3A, and KLC3 are implicated in the tail formation process; and KIF20 and KRP3 likely participate in sperm translocation. KIF17b also exhibited postmeiosis transcriptional activities that are critical for the dramatic alterations observed in nuclear and cytoplasmic structures. This review summarizes the roles of kinesins during mitosis, meiosis, and spermiogenesis, and proposes several important issues for further investigation.

Chromosomal segregation in sperm of Robertsonian translocation carriers

To study meiotic segregation patterns of Robertsonian translocations in sperm of male carriers and to assess the frequencies of unbalanced sperm formation. FISH with combination of probes to detect all the variants of meiotic segregation was performed on decondensed sperm nuclei of 5 carriers of der(13;14), 3 carriers of der(14;21) and one carrier of a rare der(13;21) translocation. The frequency of sperm with alternate segregation and normal/balanced chromosomal complement ranged from 68% to 94.4% (mean 79.2 ± 8.4). Adjacent segregation was detected in 17.9 ± 7.3% of sperm (from 5.6% to 29%). No significant differences in frequencies of gametes with nullisomies and disomies of chromosomes involved in translocations were observed. The mean frequency of 3:0 segregation products was 2.5 ± 1.4%. All analyzed patients showed homogenous segregation pattern with clear predominance of alternate segregation resulting in normal/balanced sperm production. Still, from 5.8-32% (mean 20.4 ± 8.3%) of sperm was unbalanced, which is the evidence of the increased risk of unbalanced offspring in carriers of Robertsonian translocations. Our results highlight the importance of genetic counseling of Robertsonian translocation carriers prior to ICSI or IVF.

The chromosomal risk in sperm from heterozygous Robertsonian translocation carriers is related to the sperm count and the translocation type

To study the chromosomal risk in sperm from Robertsonian translocation (RobT) carriers as a function of the sperm count and translocation type. Prospective study. Departments of reproductive biology, cytogenetics, gynecology, and obstetrics. A total of 29 RobT patients (8 normozoospermic and 21 oligozoospermic) and 20 46,XY patients (10normozoospermic and 10 oligozoospermic). Sperm fluorescence in situ hybridization with probes for translocation malsegregation and chromosome 13, 18, 21, X, and Y probes for studying the interchromosomal effect (ICE). Translocation malsegregation and ICE aneuploidy rates. In RobT carriers, the sperm translocation malsegregation rate was significantly lower in normozoospermic patients (9.7%) than in oligozoospermic patients (18.0%). Considering only oligozoospermic patients, sperm malsegregation rates were significantly lower for rob(14;21) than for rob(13;14) (11.4% vs. 18.9%). In turn, the rates were significantly lower for rob(13;14) than for rare RobTs (18.9% vs. 25.3%). In sperm from normozoospermic RobT, an ICE was suggested by higher chromosome 13 and 21 aneuploidy rates than in control sperm. Conversely, chromosome 13 and 21 sperm aneuploidy rates were lower in oligozoospermic RobT patients than in oligozoospermic 46,XY patients, but higher than in control subjects. Both translocation type and sperm count influence the RobT malsegregation risk. Of the chromosomes analyzed (13, 18, 21, X, and Y), only chromosomes 13 and 21 were found to be associated with an ICE. Relative to the RobT effect, idiopathic alterations in spermatogenesis in 46,XY patients appear to be more harmful for meiosis.

Testing multiple hypotheses for the maintenance of male homosexual copulatory behaviour in flour beetles

Diverse animal groups exhibit homosexual interactions, yet the evolutionary maintenance of such behaviours remains enigmatic as they do not directly increase reproductive success by generating progeny. Here, we use Tribolium castaneum flour beetles, which exhibit frequent male homosexual copulations, to empirically test several hypotheses for the maintenance of such behaviours: (1) establishing social dominance; (2) practice for future heterosexual encounters; and (3) indirect sperm translocation. We found no evidence that Tribolium males use homosexual copulations either to establish dominance or to practice behaviours that increase their subsequent heterosexual reproductive performance. Our results provide limited support for the hypothesis of indirect sperm translocation: when males from two genetic strains mated with females immediately following a homosexual copulation, females produced progeny sired not only by the directly mating male, but also by that male's homosexual partner. However, this phenomenon was detected in only 7% of homosexual pairs, and in each case such indirectly sired progeny accounted for < 0.5% of females' total progeny. Direct observations indicated that mounting males often released spermatophores during homosexual copulations. These observations suggest that homosexual copulations may be a behavioural mechanism that allows males to expel older, potentially low-quality sperm. Additional work is needed to test this new hypothesis, and to determine whether sperm release during homosexual copulations occurs in other groups.

Does fertilization by proxy occur in Tribolium beetles? A replicated study of a novel mechanism of sperm transfer

Sperm competition is a fundamentally important component ofpostcopulatory sexual selection, and direct removal of rival malesperm from the female reproductive tract has been documented inat least three insect orders: Odonata, Orthoptera and Coleoptera(e.g. Siva-Jothy 1987; Ono et al. 1989; Gage 1992; Simmons 2001).Haubruge et al. (1999) reported a novel twist on sperm removal,a process they termed fertilization by proxy, in the red flour beetleTribolium castaneum. This study suggested that not only do malesremove previously stored sperm from females, but that males alsotranslocate rival males’ sperm when they subsequently mate withnew females. The mechanism they proposed was rival spermremoval by an array of chitinous spines located on the matingmale’s aedeagus, followed by translocation of these still viablesperm when this male subsequently mated with another female.Empirical evidence for this novel phenomenon was based ona physiological paternity marker involving resistance to the insec-ticide malathion, which in T. castaneum is due to a spontaneousmutation in a carboxylesterase enzyme that confers malathion-specific resistance (Dyte & Rowlands 1968; White & Bell 1988;Haubruge et al. 2002; Arnaud et al. 2005). The experimental designincludedthreeconsecutivecrosses:(1)amalathion-resistantvirginmalewasmatedwithamalathion-susceptiblevirginfemale,(2)thesame susceptible female was mated with a susceptible virgin maleand (3) the same susceptible male was mated with a new suscep-tible virgin female. Adult progeny collected from the two matedfemales were subjected to an insecticide-exposure bioassay(contact with 1% malathion in acetone) for 3 h. Paternity wasassigned based onwhether progeny died (indicating they had beensired by the directly mating, susceptible male) or survived(presumed to be sired indirectly by the resistant male). Haubrugeet al. (1999) reported that fertilization by proxy was quite common(occurring in 22% of sequential matings), and that in such cases,a surprisingly high percentage (53% on average) of offspring weresired by translocated sperm.To date, this study by Haubruge et al. (1999) remains the onlyevidence for rival sperm translocation, a phenomenon that couldpotentially counteract any fitness advantages that males may gainfrom sperm removal. As pointed out recently by Kelly (2006),replication studies traditionally have been undervalued in behav-ioural ecology, and consequently both confirmatory and contra-dictory results may be difficult to publish. However, verification ofkey empirical results should be standard operating procedure torigorously test any novel evolutionary hypotheses. Based on theimportant evolutionary implications of the phenomenon of spermtranslocation, we conducted a partial replication of the study byHaubruge et al. (1999), in which we exactly duplicated mostexperimental procedures but used a different paternity marker todifferentiate between the two potential sires.

Genetic variation affects de novo translocation frequency.

Translocation is one of the most frequently occurring human chromosomal aberrations. The constitutional t(11;22)(q23;q11), which is the only known recurrent non-Robertsonian translocation, represents a good model for studying translocations in humans. Here we demonstrate polymorphisms of the palindromic sequence at the t(11;22) breakpoint that affect the frequency of de novo translocations in sperm from normal males. A typical allele consists of a perfect palindrome, producing ~10-5 de novo t(11;22) translocations. Alleles with an asymmetric center do not form the t(11;22). Our data show the importance of genome sequence on chromosomal rearrangements, a class of human mutation that is thought to be random.

Unexpectedly high rate of de novo constitutional t(11;22) translocations in sperm from normal males.

Junction fragments from the constitutional t(11;22)(q23;q11) translocation have previously been cloned and sequenced. Here we report a high incidence of translocation-specific PCR products in sperm DNA from normal individuals. Somatic DNA from these and other normal individuals or from people with chromosomal breakage syndromes do not yield PCR junction fragments, indicating that this translocation originates during meiosis.

Fertilization by proxy: rival sperm removal and translocation in a beetle

Competition between diierent males’ sperm for the fertilization of ova has led to the evolution of a diversity of characters in male reproductive behaviour, physiology and morphology. Males may increase sperm competition success either by enhancing the success of their own sperm or by negating or eliminating the success of rival sperm. Here, we ¢nd that in the £our beetleTribolium castaneum, the second male to mate gains fertilization precedence over previous males’ sperm and fertilizes approximately two-thirds of the eggs. It is not known what mechanism underlies this pattern of last-male sperm precedence; however, the elongate tubules of the female sperm storage organ may encourage a‘last-in, ¢rst-out’sperm use sequence. Here we present an additional or alternative mechanism of sperm precedence whereby previously deposited sperm are removed from the female tract by the mating male’s genitalia. In addition to providing evidence for sperm removal inT. castaneum, we also show that removed, non-self sperm may be translocated back into the reproductive tracts of new, previously unmated females, where the translocated sperm go on to gain signi¢cant fertilization success.We found that, in 45 out of 204 crosses, sperm translocation occurred and in these 45 crosses over half of the oispring were sired by spermatozoa which had been translocated between females on the male genitalia. In the natural environment of stored food, reproductively activeT. castaneum adults aggregate in dense mating populations where copulation is frequent (we show in three naturally occurring population densities that copula duration and intermating intervals across three subsequent matings average 1^2min). Selection upon males to remove rival sperm may have resulted in counter-selection upon spermatozoa to survive removal and be translocated into new females where they go on to fertilize in signi¢cant numbers.

Dose response study for 1,3-butadiene-induced dominant lethal mutations and heritable translocations in germs cells of male mice

Butadiene (BD) and its metabolites have extensively been studied in the EU sponsored research project `Multi-endpoint analysis of genetic damage induced by 1,3-butadiene and its major metabolites'. Within this project a dominant lethal test and a heritable translocation test were performed with male mice to study the dose-response relationships for the respective endpoints. BD concentrations of 130 and 500 ppm were tested in the dominant lethal assay by exposing male mice on 6 h/day for five consecutive days resulting in doses of 3900 and 15 000 ppmh, respectively. Males were mated for four consecutive weeks at a ratio of 1:2 to untreated females. A positive dominant lethal effect was observed in the first mating week in the experiment with 15 000 ppmh but no dominant lethality was found with the lower dose of 3900 ppmh. The present dominant lethal data have to be viewed together with the data already published for a BD dose of 39 000 ppmh (1300 ppm at 6 h/day on 5 consecutive days) [1]. The main difference between results with the highest and the middle dose is that mating weeks one and two (sperm and late spermatids) showed an effect at 39 000 ppmh while only mating week one (sperm) showed an effect at 15 000 ppmh. In the heritable translocation assay, males mice were exposed with a BD dose of 15 000 ppmh and mated for one week to untreated females. Among 434 F 1 offspring, we found 5 translocation carriers (1.15% vs. 0.05% in the historical control, p<0.001). In the previous heritable translocation experiment with a BD dose of 39 000 ppmh of DB exposure, 2.7% of the offspring carried a reciprocal translocation [2]. These data can be used for quantification of genetic risk. The dose response for BD-induced heritable translocations in sperm and late spermatids of mice was linear ( Y=0.05+6.9×10 −5 X) and a doubling dose of 725 ppmh could be calculated.

P XIV C.17 - P XIV C.17 Neocarzinostatin-induced chromosome translocations in human sperm and peripheral blood lymphocytes

P XIV C.17 - P XIV C.17 Neocarzinostatin-induced chromosome translocations in human sperm and peripheral blood lymphocytes

Detection of neocarzinostatin-induced translocations in human sperm chromosomes using fluorescence in situ hybridization of chromosome 2

Mature sperm and late spermatid are known to be sensitive stages to clastogens in mammalian spermatogenesis. Certain types of chromosomal damage induced in these stages will pass to successive generations as heritable translocations. In the present study, we employed whole chromosome 2 painting with the fluorescence in situ hybridization (FISH) technique to detect the chemically induced translocations in human sperm. Mature human sperm were treated in vitro with an antitumor drug, neocarzinostatin (NCS), and fertilized in vitro with golden hamster oocytes. Sperm pronuclear chromosomes slides were prepared at the first cleavage metaphase. To compare the characteristics of translocations between somatic and germ cells, human lymphocytes in peripheral blood treated with NCS in vitro were analyzed at first round metaphase after PHA-stimulation. From the analysis of translocations by whole chromosome 2 painting, frequencies of the haploid genomic translocations ( F hG) were predicted for both sperm and lymphocytes At 1.0 μg/ml, the actual percentages of sperm and lymphocytes with chromosome 2 translocations were almost identical (11.9% and 12.0%). At the same dose, however, the F hG of the sperm (1.15) was considerably higher than that of the lymphocytes (0.58), indicating that complex translocations having two or more rearranged sites were induced by NCS more frequently in sperm than in lymphocytes.

Male disturbance, repeated insemination and sperm competition in the damselflyCoenagrion scitulum(Zygoptera: Coenagrionidae)

Before mating, all male odonates translocate sperm from the testes (IX segment) to the penis (II segment), but inCoenagrion scitulumthis behaviour is repeated up to six times during copulation. The aim of this study was to find an explanation for this unusual behaviour. Copulation behaviour consists of three to seven cycles, each of which includes one intra-male sperm translocation, one stage I and one stage II (i.e. the complete copulatory sequence typical of zygopterans). The duration of pre-copulatory tandem and cycle 1 of copulation was negatively correlated with time of day and positively with male disturbance. Males captured during stage I of any copulatory cycle always had the seminal vesicle full of sperm, thus indicating that they do translocate sperm during sperm translocation behaviour. Females were inseminated at stage II. The volume of ejaculate in females in the field interrupted during stage I of the first copulatory cycle was not significantly different from the volume stored by pre-copula females indicating that males cannot remove a significant amount of sperm from the female's genital tract at this stage. Spines on the horns of the penis, which in other damselflies help remove the sperm stored by females, are, however, absent inC.scitulum. Experiments with virgin females that received up to five inseminations indicated that the sperm are progressively packed, and therefore the volume is not directly proportional to the number of inseminations. MaleC.scitulumthus has a poor sperm removal ability and multiple intra-male sperm translocation and insemination of the female during the same copulatory act seems to be a mechanism of sperm competition by which the male achieves a greater fertilization success.

In Ascaris sperm pseudopods, MSP fibers move proximally at a constant rate regardless of the forward rate of cellular translocation.

Computer-assisted methods have been employed to obtain a high resolution description of pseudopod expansion, cellular translocation, and the subcellular dynamics of MSP fiber complexes in the motile sperm of the nematode Ascaris suum. Although Ascaris sperm translocating in a straight line or along a curved path do not retract their pseudopod or significantly alter pseudopod shape, they move in a cyclic fashion, with an average period between velocity peaks of 0.35 +/- 0.05 min, which is independent of the forward velocity of sperm translocation. Expansion is confined to a central zone at the distal edge of the pseudopod for sperm translocating in a straight line and to a left-handed or right-handed lateral zone in the direction of turning, for sperm translocating along a curved path. For cells translocating in a straight line, the branch points and kinks of MSP fiber complexes move in a retrograde direction in relation to the substratum at an average velocity of 11 microns per min which is independent of the forward velocity of sperm translocation. The distal (anterior) end of a fiber complex, however, moves distally at the speed of sperm translocation when it emanates from the expansion zone, but when it is displaced to a nonexpanding surface of the pseudopod, it stops moving distally. When a cell is anchored to the substratum and is, therefore, nonmotile, the velocity of fiber complexes moving in a retrograde direction doubles. The unique aspects of pseudopod and MSP fiber complex dynamics in Ascaris are compared to the dynamics of pseudopod formation and actin filament dynamics in traditional actin-based amoeboid cells, and the treadmill model for MSP polymerization is reassessed in light of the discovery that fiber complex branch points move proximally (posteriorly) at a fixed rate.

Mating behaviour of the water mite Arrenurus manubriator (Acari: Arrenuridae)

Water mites of the genus Arrenurus vary in male sexual dimorphism and in sperm transfer behaviour. Although it is a very large genus (≈800 spp.), mating behaviour has been described for only a few species. Here sperm transfer behaviour is described for the first time in a North American species, Arrenurus manubriator. Behaviour patterns can be divided into pre‐pairing (readiness posture and cauda presentation), pre‐deposition (high vertical jerking, low vertical shaking, striking/stroking and slow lateral waving), spermatophore deposition, sperm translocation, post‐deposition (striking/stroking. slow lateral waving, ‘tick‐rock’, shuttling, violent shaking), and separation. Males deposited 8–21 spermatophores in a mating. Pairs remained together for up to 31/2h. Possible adaptive functions of male courtship behaviour are discussed, including the hypothesis that male intromittant organs evolved in Arrenurus to circumvent female choice.