The sperm of Matsucoccus feytaudi (Insecta,Coccoidea): Can the microtubular bundle be considered as a true flagellum?

In the present work the spermiogenesis and sperm structure of Matsucoccus feytaudi, a primary pest of the maritime pine in southern eastern Europe, is studied. In addition to the already known characteristics of coccid sperm, such as the absence of the acrosome and mitochondria, and the presence of a bundle of microtubules responsible for sperm motility, a peculiar structure from which the microtubule bundle takes origin is described. Such a structure – a short cylinder provided with a central hub surrounded by several microtubules with a dense wall – is regarded as a Microtubule Organizing Centre (MTOC). During spermiogenesis, quartets of fused spermatids are formed; from each spermatid, a bundle of microtubules, generated by the MTOC, projects from the cell surface. Each cell has two centrioles, suggesting the lack of a meiotic process and the occurrence of parthenogenesis. At the end of the spermiogenesis, when the cysts containing bundles of sperm are formed, part of the nuclear material together with the MTOC structure is eliminated. Based on the origin of the microtubular bundle from the MTOC, the nature of the bundle as a flagellum is discussed.     

Team swimming in ant spermatozoa

In species where females mate promiscuously, competition between ejaculates from different males to fertilize the ova is an important selective force shaping many aspects of male reproductive traits, such as sperm number, sperm length and sperm–sperm interactions. In eusocial Hymenoptera (bees, wasps and ants), males die shortly after mating and their reproductive success is ultimately limited by the amount of sperm stored in the queen''s spermatheca. Multiple mating by queens is expected to impose intense selective pressure on males to optimize the transfer of sperm to the storage organ. Here, we report a remarkable case of cooperation between spermatozoa in the desert ant Cataglyphis savignyi. Males ejaculate bundles of 50–100 spermatozoa. Sperm bundles swim on average 51% faster than solitary sperm cells. Team swimming is expected to increase the amount of sperm stored in the queen spermatheca and, ultimately, enhance male posthumous fitness.     

Marked sperm dimorphism in the ground beetle Scarites terricola: a novel type of insect sperm polymorphism

Sperm polymorphism describes the phenomenon of male ejaculates containing two or more distinct types of sperm. In insects, four types of sperm polymorphism are recognized in species from the orders Diptera, Hemiptera, Hymenoptera, Lepidoptera and Coleoptera. The present study describes dimorphic sperm of the ground beetle Scarites terricola (Coleoptera: Carabidae) as a novel type of sperm polymorphism in insects. Sperm from the spermatophore and male seminal vesicles are examined at the light‐microscopic level, and both display marked dimorphism. One type has sperm formed into bundles, in which the head of numerous spermatozoa are ‘glued’ together, with tails free‐moving. The other type are free as single spermatozoa and have a disproportionately large‐sized head and an elongated tail. Both types are motile in Ringer's solution. The adaptive and phylogenetic importance of these findings is discussed.     

Ultrastructure and function of long and short sperm in Cicadidae (Hemiptera)

The cicada, Graptopsaltria nigrofuscata, produces two distinct sizes of sperm, as determined by either nuclear volume of early spermatids or nuclear length of mature sperm. Between both sperm, there is no difference in location of the acrosome and flagellum during spermiogenesis. The acrosome is covered by an anteacrosomal bleb, which is inserted in a common mass, spermatodesm, derived from cyst cells. Both kinds of sperm linked to the spermatodesm form sperm bundles, respectively. During copulation, the sperm bundles are transported from the vesicula seminalis of the male to the bursa copulatrix of the female. Morphometric analyses of the nuclear length revealed that the two kinds of sperm reach the bursa copulatrix in the same condition as that found in the vesicula seminalis. Once transferred inside the latter, the sperm bundles disintegrated to individual sperm within a few hours, and the tail components, such as the axoneme and mitochondrial derivatives, become separated from each other over time. The tail completely splits from the sperm nucleus 24 h after copulation. Fertile sperm accumulate in the spermatheca, the final storage organ, where only long sperm survived for any length of time. Fertilized eggs examined by vital staining contain only sperm with long nuclei.     

Ultrastructural studies on euspermatozoa and paraspermatozoa in Mantispidae (Insecta, Neuroptera)

Previous studies have demonstrated the presence of sperm dimorphism in the Mantispidae Perlamantispa perla. We extended the study on several other mantidflies. In all the examined species the occurrence of euspermatozoa (typical) and paraspermatozoa (atypical) was established. The euspermatozoa are characterized by the presence of a cylindrical nucleus surrounded by an envelope that fans out laterally into two thin wings of different length. The acrosome seems to be missing. The nucleus is surrounded by extracellular material. The flagellum is provided with a 9 + 9 + 2 axonemal pattern; the accessory tubules contain 16 protofilaments and the intertubular material has the distribution typical of the taxon. Two elongated accessory bodies flank partially the axoneme and connect this structure with the mitochondrial derivatives. The flagellar axoneme of paraspermatozoa consists of an axoneme and two giant mitochondrial derivatives filled with large globular units. The axoneme exhibits a 9 + 9 + 2 pattern, in which the central 9 + 2 units have a normal structure, in that the microtubular doublets are provided with both dynein arms and radial links. On the contrary, the nine accessory microtubules have a large diameter and their tubular wall consists of 40 protofilaments. This comparative study provided evidences about the uniformity of sperm ultrastructure in Mantispidae. The function of non-fertilizing giant sperm in mantidflies is discussed.     

Effects of 20-hydroxyecdysone on sperm release from the testes of the Mediterranean flour moth,Anagasta kuehniella (Zeller)

Abdominal injection of 1 μg aqueous 20-hydroxyecdysone into Anagasta kuehniella, anytime prior to the initiation of sperm release from the testes, prevents the impending release of eupyrene sperm bundles. Apyrene sperm release is not prevented and there is complete recovery of eupyrene release by the following cycle 24 hr later. If 20-hydroxyecdysone is administered on consecutive days, no eupyrene bundles are released and although apryene sperm release continues, it diminishes with time. The effect of 20-hydroxyecdysone in preventing eupyrene release is dose dependent. Administration of decreasing 20-hydroxyecdysone dosages results in increasing numbers of eupyrene bundles released. When a single injection of 20-hydroxyecdysone is administered to isolated abdomens, recovery time of eupyrene sperm release is slower than in whole moths and total recovery is not seen even by 5 days after administration. Apyrene sperm release is also affected to a greater extent than in whole moths, and in some cases, no apyrene release was detected at all. Treatment with 20-hydroxyecdysone prevents cupyrene bundles from passing through the testicular basilar membrane into the vasa efferentia, thus causing a build up of bundles near the basilar membrane but no disintegration of these eupyrene sperm bundles.     

In vitro cultivation of spermatocysts to matured sperm in the silkworm Bombyx mori

Bombyx spermatogonia are bipotential, producing nucleate eupyrene sperm and anucleate apyrene sperm. An in vitro cultivation of spermatocysts of Bombyx mori from spermatocytes to matured sperm was established. The present experiment made clear that: (i) spermatocysts must be isolated; (ii) constant shaking at 45 r.p.m. was necessary; and (iii) the addition of Bombyx hemolymph (BH) was indispensable for successful cultivation. In the absence of BH, spermatogenesis proceeded normally for 2 or 3 days and, thereafter, spermatocytes and sperm bundles began to degenerate. The best results for normal eupyrene spermatogenesis were obtained when culture medium containing BH of the corresponding stage was used in every exchange of the medium at 72 h intervals. None or only a small number of apyrene sperm bundles was produced by this culture system when spermatocysts from larval testes were used, although eupyrene spermatogenesis proceeded normally to form matured, or squeezed, sperm bundles.     

Roles of actin networks in peristaltic squeezing of sperm bundles in Bombyx mori

Two types of sperm are produced in the silkworm, Bombyx mori. Nucleate eupyrene sperm is an ordinary sperm that contributes to fertilization, while anucleate apyrene sperm is considered to play important roles in assisting eupyrene sperm. At the very late stage of spermatogenesis, a phenomenon called "peristaltic squeezing" occurs in both types of sperm, whereby cytoplasm of the eupyrene and nuclei of the apyrene sperm are discarded from the posterior end, forming matured sperm. In this study, rhodamine-phalloidin staining for actin was applied to sperm bundles. Before the start of peristaltic squeezing, actin filament networks are spread on the cyst cells and constrictions by the networks appear in several places of the bundles. Actin particles, which are later recognized as circlets, are localized within the bundles. Squeezing action by the networks occurs from the anterior region and transfers toward the posterior, eliminating cytoplasm together with circlets from the posterior end. It seems that actin filaments contribute to the peristaltic squeezing of the sperm bundles in Bombyx mori.     

Effect of constant light on male sterility in the cotton leafworm Spodoptera littoralis

Females of the cotton leafworm (Spodoptera littoralis) reared in long day conditions (LD 16:8 h) and mated to males kept throughout the whole period of development in continuous light (LL) oviposit very small numbers of mostly sterile eggs. It was found that in control males reared from the first larval instar in long day conditions there was a large accumulation of euperene sperm bundles in their testes on day 1 after imaginal moult. On day 10 of adult life the number of the sperm bundles was very small. In males kept from the first instar in continuous light there was also high number of sperm bundles on day 1 after imaginal moult but it did not decrease significantly on day 10 as was observed in controls. Transfer of different developmental stages of S. littoralis from long day conditions to continuous light resulted in a big difference in the density of eupyrene sperm bundles in their testes. In control insects reared through the whole of their development in long day conditions there was a significant decrease in the density of eupyrene sperm bundles on day 10 of adult life. By contrast, in males in continuous light, regardless of their developmental stage when transferred, there was either no change in density of sperm bundles in day 10 adults or there was a significant increase in comparison with day 1 adults. The highest density of eupyrene sperm bundles was observed in day 10 adults when they were transferred to continuous light shortly before moulting to the last instar (as day 4 larvae in the last stadium or day 1 pupae). Generally, the density of eupyrene sperm bundles on day 10 of adult development was about 2–2.5 times higher in males in continuous light then those under long day conditions. The results presented here indicate that the last larval instar and the pupa are the stages most sensitive to constant light treatment, which greatly reduces the amount of eupyrene sperm bundles released from the testes.     

Ultrastructure of spermiogenesis and spermatozoa in Marchalina hellenica (Gennadius) (Hemiptera: Sternorrhyncha,Marchalinidae)

The spermiogenesis, the sperm structure and the sperm motility of Marchalina hellenica (Gennadius) were examined. In the early spermiogenesis a centriolar apparatus was identified, but this structure is not involved in the production of the sperm flagellum. As in other Coccoidea, the flagellar axoneme originates by the activity of the thickened tip of the numerous microtubules surrounding the nuclear anterior region close to the periphery of the cell. This region pushes against a narrow cytoplasmic layer, giving rise to a papilla. In this region a novel structure, consisting of a regular network of thin filaments, arranged orthogonally to the bundle of microtubules, is visible. The sperm flagellum consists of a series of about 260 microtubules, regularly arranged in rings around the axial nucleus. This latter extends in the middle part of the sperm length. As usual in scale insects, sperm form a bundle, which in M. hellenica is composed of 64 sperm cells, surrounded by somatic cyst cells. The sperm bundle has an helicoidal array, with a cap of dense material at its apex, lending the anterior and the posterior region of the sperm bundle with a different structural organization. This difference is responsible of the different speed gradient observed in the helical wave propagating along the sperm bundle.     

Black goby territorial males adjust their ejaculate's characteristics in response to the presence of sneakers

In many species, males can rapidly adjust their ejaculate performance in response to changing levels of sperm competition, an ability that is probably mediated by seminal fluid adaptive plasticity. In the black goby, Gobius niger, territorial males attach viscous ejaculate trails to the nest roof, from which sperm are slowly released into the water during the long-lasting spawning events. Sneaker males release their sperm in the vicinity of the nest, and territorial males try to keep them at a distance by patrolling their territory. We show here that territorial males'' ejaculate trails released a higher proportion of their sperm in the presence of a single sneaker, but this proportion decreased when there were three sneakers, an effect that is most likely mediated by a change in the seminal fluid composition. Field observations showed that when multiple sneaking attempts occurred, territorial males spent more time outside the nest, suggesting that ejaculation rate and territory defence are traded-off. Altogether, these results suggest that the adjustment of sperm release from the ejaculate may be strategic, guaranteeing a more continuous concentration of the territorial male''s sperm in the nest, although at a lower level, when he is engaged in prolonged territory defence outside the nest.     

The giant sperm of a minute beetle

The mature sperm of Ptinella aptera is a helically coiled, flagellate gamete ca. 1.4 mm long—twice the length of the beetle itself. The rod-like acrosome, comprising the anterior part of the sperm, is 0.4 μm thick but is expanded as a flange around the nucleus and the base of the tail, increasing the diameter of the sperm to 2 μm. The bulk of the tail consists of a pair of bodies with a characteristic ultrastructure of longitudinal tubules beneath a lamellar cortical layer. These bodies are probably homologous with the mitochondrial derivatives of other insect sperm. The axoneme is helically coiled and is flanked by a single accessory body. One of the ‘structured bodies’ is connected to the acrosome and the other to the accessory body. The sperm move actively in the female reproductive tract. The functional significance of this behaviour and of the evolution of the large gamete itself is discussed in relation to existing hypotheses.     

Sperm storage by spermatodoses in the spermatheca of Trioza alacris (Flor, 1861) hemiptera,psylloidea, triozidae: A structural and ultrastructural study

Female insects generally store sperm received during mating in specific organs of their reproductive tract, i.e., the spermathecae, which keep the sperm alive for a long time until fertilization occurs. We investigated spermatheca morphology and ultrastructure in the psylloidean insect Trioza alacris (Flor, 1861 ) in which spheroidal sperm packets that we refer to as ‘spermatodoses’ are found after mating. The ectoderm‐derived epithelium of the sac‐shaped spermatheca that has a proximal neck, consists of large secretory and flat cuticle‐forming cells. Secretory cells are characterized by a wide extracellular cavity, bordered by microvilli, in which electron‐dense secretion accumulates before discharge into the spermathecal lumen. The cuticle‐forming cells produce the cuticular intima of the organ and a peculiar specialized apical structure, through which secretion flows into the lumen. At mating, the male transfers bundles of sperm cells embedded in seminal fluid into the spermathecal neck. Sperm cells proceed towards the spermathecal sac lumen, where they are progressively compacted and surrounded with an envelope that also encloses secretions of both male and female origin. We describe the formation of these sperm containing structures and document the contribution of the female secretion to spermatodose or female‐determined spermatophore construction. We also discuss the choice of the term ‘spermatodose’ for T. alacris and suggest it be used to refer to sperm masses constructed in the female reproductive organs, at least when they involve the contribution of female secretion. © 2011 Wiley Periodicals, Inc.     

Eupyrene sperm migrates to spermatheca after apyrene sperm in the swallowtail butterfly, Papilio xuthus L. (Lepidoptera: Papilionidae)

When swallowtail butterflies, Papilio xuthus, are mated by the hand-pairing method, both types of sperm, eupyrene and apyrene sperm, are transferred from the male to the spermatheca via the spermatophore in the bursa copulatrix. This mechanism is demonstrated by two different kinds of experiments. The first set of experiments employed interrupted copulation, and the second set was examination of the sperm in the spermatophore and spermatheca after the termination of copulation. The sperm was transferred 30 min after the start of copulation. The eupyrene sperm was still in the bundle; the number of the bundles ranged from 9 to 108 (mean, 42.7; n = 27). The bundles were gradually released after the completion of copulation, and the free eupyrene spermatozoa then remained in the spermatophore at least 2 h before migrating to the spermatheca. On the other hand, about 160 000 apyrene spermatozoa were transferred to the spermatophore and remained there for more than 1 h. We observed 11 000 apyrene spermatozoa in the spermatheca 12 h after the completion of copulation, but most of this type of sperm disappeared shortly thereafter. In contrast, the eupyrene sperm arrived in the spermatheca more than 1 day after the completion of copulation and remained there at least 1 week. Therefore, these findings suggest that apyrene sperm migrate from the spermatophore to the spermatheca earlier than eupyrene sperm. Accordingly, if females mated multiply, the time difference might avoid the mixing of sperm. In addition, the predominance of sperm from the last mating session may occur not in the bursa copulatrix but in the spermatheca. Received: January 7, 2000 / Accepted: May 24, 2000     

Comparison of flagellated and nonflagellated sperm in plants

Differences among flagellated and nonflagellated sperm in land plants are striking, but close examination reveals similarities in pattern of cytoskeleton and in nuclear structure. The microtubular cytoskeleton of flowering plant sperm consists of microtubule bundles arranged obliquely around the nucleus, terminating in cellular extensions. Microtubules are linked into bundles that branch and rejoin along the axis of the sperm cell, forming a cytoskeleton that determines cell shape but does not actively participate in cell movement. Generative cells and sperm share a pattern of microtubules not found in somatic cells. This pattern is initiated in the generative cell, one division before sperm formation, a situation parallel to spermatogenous cell development in vascular plants with flagellated sperm. Chromatin in flagellated and nonflagellated sperm is condensed by specialized histones.     

Physiological basis for sterilizing effects of constant light in Lymantria dispar

ABSTRACT Females of gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae), mated to males kept in constant light (LL) as pharate adults fail to oviposit. In males, a rhythm of sperm release from the testis that occurs in light-dark (LD) cycles is abolished in LL, and the total amount of sperm released from the testis is approximately half of that of LD males. Moreover, any sperm that may be released from the testis of LL males tend to remain in the vasa deferentia instead of moving into the duplex as in LD males. Consequently, in LL very few sperm bundles are transferred to the bursa copulatrix during mating; furthermore, these bundles fail to disperse into spermatozoa and sperm do not reach the spermatheca. The presence of a spermatheca filled with sperm must play an important role in controlling oviposition because their removal from mated females prevents egg-laying. Our results indicate that the rhythm of sperm release from the testis is essential for the ability of sperm to migrate in male and female reproductive tracts. The rhythms may help to synchronize final stages of sperm development with the activity of phagocytic and secretory cells lining the reproductive tract.     

二种寄生蜂寄生抑制小菜蛾精巢生长和精子束形成的比较研究

我们曾发现菜蛾盘绒茧蜂Cotesia vestalis和半闭弯尾姬蜂Diadegma semiclausum寄生严重阻碍小菜蛾Plutella xylostella幼虫的精子发生。本研究着重比较2种蜂寄生对小菜蛾精巢生长和精子束形成的影响, 以探明寄生因子对昆虫生殖调控的作用途径。 采取过寄生和假寄生方法, 对2种蜂各自寄生后的小菜蛾精巢生长体积, 精子发生和形成过程中生精细胞、精子束的显微形态变化进行了比较。 结果表明: 茧蜂和姬蜂寄生均明显降低小菜蛾精子束的数量, 严重阻碍了寄主幼虫的精子发生和精子形成. 姬蜂寄生造成小菜蛾精巢畸形, 而茧蜂则造成小菜蛾精子束畸形, 且茧蜂对小菜蛾精巢生长的抑制程度明显强于姬蜂。过寄生造成寄主寄生性去势程度加剧, 茧蜂和姬蜂过寄生后的小菜蛾精巢体积分别为0.005 mm³和0.008 mm³, 仅为各自只寄生1次后精巢体积的33.1%和36.3%。假寄生后, 发现只有寄生蜂母代物质存在的前提下, 对小菜蛾精巢生长的抑制程度基本模拟了正常寄生时的状态, 说明多分DNA病毒（polydnavirus, PDV）和毒液发挥了主要作用。 由此推断分属姬蜂属PDV和茧蜂属PDV的2类PDV功能基因对小菜蛾精巢生长发育的调控机制可能存在较大差异。     

Sperm co-operation in the Fishfly, Parachauliodes japonicus

1. Males of the Fishfly Parachauliodes japonicus (McLachlan) produce sperm in bundles. Each bundle consists of hundreds of sperm with their heads agglutinated. At copulation, on average 500 bundles are packed in a single spermatophore which is attached externally to the female genitalia. The bundles swim forward by synchronous flagellate movements in viscous seminal fluids and finally enter a spermatheca of the female. Females detach the spermatophore without guarding by the male; males guard the spermatophore for 5 h.
2. In this study, the effects of sperm-bundle size and medium viscosity on their swimming velocities were examined. As sperm-bundle mass increased, the amount of time it took to move a unit length decreased. As viscosity increased, those sperm-bundles with greater mass moved faster than sperm-bundles with less mass.
3. The distance sperm move seems to be longer in P. japonicus than in most other insects that ejaculate directly or place the spermatophore internally in the female storage organs. Thus, large sperm-bundles may be an advantage for sperm of P.japonicus who move over a long distance in a viscous environment.     

Structure and development of sperm bundles in the dragonfly Aeshna juncea L. (Odonata)

A re-examination of the origin and development of sperm bundles in aeshnid dragonflies (Odonata, Anisoptera) was carried out using light and electron microscopy. During their elongation, intracyst spermatids of the testis of the dragonfly Aeshna juncea L. form a slender cytoplasmic protrusion, the acrosomal conicoid, beyond the nucleus and acrosome rodlet. Gathering and parallel alignment of the transforming spermatids into a tight bundle take place inside the cyst. The original, rigid spermatid foreparts eventually associate, initially by becoming adhesive and swelling progressively to intertwine, and thus come to constitute a cap that binds together all sperm heads within a cyst in a spermatodesma. The development of the spermatodesma seems to occur disjunct from somatic cyst cells. Bundled in this form, the sperms are transferred to the intratestis canal and moved down the spermiduct to the seminal vesicle. They are then forwarded to the male copulatory apparatus, from which they are transmitted to the female. Individual, fully formed sperms are seen to be liberated from the bundle when in the female receptaculum seminis. The remnant of the cytoplasmic acrosomal conicoid, which is considered an envelope of the acrosome rodlet, is then dissolved. The spermatodesmata are large sperm aggregates that constitute efficient vehicles for transmission of amounts of filamentous sperm to the female. J. Morphol. 235:239–247, 1998. © 1998 Wiley-Liss, Inc.