珠蚌科六种蚌的钩介幼虫形态比较研究

本文观察了背角无齿蚌、沼纹冠蚌、剑状矛蚌、圆顶珠蚌、刻裂丽蚌和洞穴丽蚌等６种蚌的育儿囊类型;用光镜和扫描电镜观察和研究了幼虫的形态特征。结果表明,前４种蚌的育儿囊属外鳃类的同生型,后２种的育儿囊属外鳃类的四生型;６种幼虫均为钩介幼虫,其中前４种为有钩型,后２种为无钩型;６种幼虫的大小、形态有别,并证明种间幼虫的壳钧和壳饰的亚显微形态显然有异。本文还就６种蚌在Ｓｉｍｐｓｏｎ分类系统中的地位与按它们的育儿囊和钩介幼虫类型得到的归类进行比较。结果表明,Ｓｉｍｐｓｏｎ对６种蚌中３种的分类与归类不妥。本文为研究我国淡水贝类的分类提供一条新的途径,并为建立珠蚌类的自然分类系统积累资料。     

Morphological and morphometrical description of the glochidia of Westralunio carteri Iredale, 1934 (Bivalvia: Unionoida: Hyriidae)

Most freshwater mussel (Bivalvia: Unionoida) larvae (glochidia in Margaritiferidae, Hyriidae and Unionidae) are fish parasites. Knowledge of the larval morphology and the mechanism of release in freshwater mussels is useful in species systematics and ecology. Westralunio carteri is the only unionoid from south-western Australia. Little information is available on its biology and its glochidia have never been described. The aim of this study was to describe the glochidia of W. carteri and method of their release. Glochidia within vitelline membranes were embedded in mucus which extruded from exhalent siphons of females during spring/summer; they then hatched from vitelline membranes but remained tethered by a larval thread and began characteristically “winking”. Shells (n=120) were subtriangular, 308 μm long (±0.83 SE), 251 μm high (±0.73 SE) and had a hinge length of 212 μm (±0.78 SE). Larval teeth were singular with interlocking cusps and convex or concave basal protuberances on opposing valves.     

Acquired resistance of bluegill sunfish Lepomis macrochirus to glochidia larvae of the freshwater mussel Utterbackia imbecillis (Bivalvia: Unionidae) after multiple infections

The effects of multiple infections on the host-parasite relationship between bluegill sunfish (Lepomis macrochirus) and parasitic glochidial larvae of the freshwater mussel Utterbackia imbecillis were examined. Na?ve, young-of-the-year bluegills were infected with glochidia and placed in individual observation chambers. Each day, water was drained from each chamber and the numbers of dead glochidia, live glochidia, partially metamorphosed glochidia, and fully metamorphosed juvenile mussels were counted. The same fishes were infected a total of 4 times. After 2 infections, the fish began to exhibit evidence of acquired resistance to glochidia. During the third and fourth infections, this resistance was clearly evidenced by the marked increase in the percentage of dead and live glochidia shed during the first 5 days of the infection and by the significant decrease in the success of metamorphosis. The total number of glochidia that successfully attached to the fish decreased significantly during the fourth infection relative to the first. The number of larvae attached to the host fish was positively correlated with the size of the fish during the first infection but was negatively correlated during all subsequent infections. Variance to mean ratios indicated that larvae were aggregated among host fishes during the infections. This study has important implications in propagation and conservation efforts of this endangered group of organisms.     

Subsocial behaviour in Oniticellus cinctus (Coleoptera, Scarabaeidae): effect of the brood on parental care and oviposition

ABSTRACT. In Oniticellus cinctus (F.) the nest chambers each contain about twenty brood balls. Females enlarge the brood balls during the egg and larval stages and remain in the chamber for the whole period of brood development (1 month); they then make a new nest after 1 week. The presence of the brood releases parental care and ensures that the mother remains in the nest: she repairs defects in the brood balls and the nest, and expels other O. cinctus females. A new ball is formed around a naked O. cinctus larva, but larvae of other species are killed. In addition, the brood inhibits oviposition: removal (or addition) of brood balls stimulates (or inhibits) egg laying. In inhibited ovarioles, existing follicles are resorbed and production of new ones ceases. Control of clutch size by the brood is an adaptation to the nest structure and life history of O. cinctus. It may have an important role in the reproductive strategy of other insects with parental care.     

Life‐history strategy,with ctenidial and pallial larval brooding,of the troglodytic ‘living fossil’ Congeria kusceri (Bivalvia: Dreissenidae) from the subterranean Dinaric Alpine karst of Croatia

Among freshwater bivalves, the brooding of embryos and larvae within the maternal ctenidia is well known. Exceptions to this generalization are the non‐brooding freshwater and estuarine species of Dreissena and Mytilopsis, respectively. It was reported that the freshwater troglodytic cousin, Congeria kusceri Bole, 1962, of these dreissenids does not brood either. It is herein demonstrated that C. kusceri undergoes one reproductive cycle each year. Sexes are separate, with an early male and later female bias. A small percentage (2.14%) of individuals is hermaphroditic. The gonads mature over summer from May to November. Spawning commences in September, when females release mature oocytes into their ctenidia and inhale sperm from mature males. Here the oocytes are fertilized, and develop within interfilamentary marsupia. Ctenidial tissues glandularize, and may provide a source of maternal nutrition for the embryos. At the late prodissoconch‐1 or prodissoconch‐2 stage (PR2, ~220 μm), larvae are released into the infrabranchial chamber via a birth channel along the outer edge of the ventral marginal food groove of both inner demibranchs. Here, they are brooded further in mantle pouches located beneath the inhalant siphon. Subsequently, after the PR2 stage (nepioconch/dissoconch), they are released from the inhalant siphon and assume an independent life as crawling juveniles. Such juveniles may be found amongst clusters of adults. Not only is C. kusceri unique amongst the Dreissenidae in possessing the capacity to brood internally fertilized ova, but it is also exceptional amongst the Bivalvia in possessing the described methods of brooding and birth. Explanations for both lie in its troglodytic lifestyle, decadal length longevity and habitat: that of byssal attachment to the hard surfaces of underground freshwater rivers, caves, pits, and sinkholes in the Tethyan arc of the Dinaric karst. Internal fertilization of a few large yolky eggs, lecithotrophic larvae, ctenidial brooding, and secondary pallial parental care represent relatively recent, Late Miocene, evolutionary adaptations from a Tethyan lentic ancestor.     

Influence of cortisol on the attachment and metamorphosis of larval Utterbackia imbecillis on bluegill sunfish (Lepomis macrochirus)

The larvae of unionid freshwater mussels (i.e., glochidia) undergo a parasitic stage requiring their attachment to the external epithelia of fish hosts, where they metamorphose into free-living juveniles. We describe the physiological effects in bluegill sunfish (Lepomis macrochirus) of infection with glochidia from the paper pondshell (Utterbackia imbecillis). Glochidia accumulation on bluegill increased dramatically at concentrations of 2000 glochidia liter(-1) and above, reaching a maximum attachment density of about 30 glochidia g(-1) fish at 4000 glochidia liter(-1). Plasma cortisol was the most sensitive indicator of biological effect to glochidial exposure, increasing significantly in hosts exposed to 2000 glochidia liter(-1) or greater. Glochidia were 31% more likely to undergo successful juvenile metamorphosis when attached to bluegill with elevated plasma cortisol, largely due to the enhanced survivorship of these larvae during the first 48 h after infection. We tested the hypothesis that glochidial attachment and juvenile metamorphosis were stimulated directly by plasma cortisol in fish hosts. Bluegill were given an intraperitoneal injection of cortisol, then infected with 1000 glochidia liter(-1) at 48 h after hormone supplementation. Cortisol-injected fish had a 42% increase in the number of attached glochidia g(-1) fish and a 28% increase in larval metamorphosis compared to sham-injected and control fish. We provide evidence that cortisol enhances glochidial metamorphosis on hosts by improving the retention of attached glochidia. This study gives insights into the influence of host physiology on glochidial attachment and juvenile mussel transformation.     

Effect of reduced pH on shells of brooded veligers in the estuarine bivalve Ostrea chilensis Philippi 1845

The oyster Ostrea chilensis develops in estuaries and incubates its embryos inside the pallial cavity. Reduced external salinity triggers valve closure and isolation of the brood chamber, which in turn alters conditions in the pallial fluid, including pH reductions ranging from 7.65 (SD = 0.05) to 6.97 (SD = 0.02) in non-brooding females and 6.96 (SD = 0.10) in brooding females after 12 h of isolation. Exposing veliger larvae to acidic pH's (5 and 3) decreased the thickness of the embryonic shell valves. Calcium, sodium, chlorine, tin, sulphur, and magnesium were the most important (> 99%) elements constituting the veliger shells. Calcium content in the pallial cavity fluid increased with continued isolation in both brooding and non-brooding females, but calcium remained as the primary component (about 94%) of embryonic shells and maintained its normal proportion with respect to the rest of the elements at all tested pH's. The increased calcium in the pallial fluid was identified mainly as coming from the shells of brooding females. If any neutralizing elements were coming from embryonic shell valves, all elements in those shells must have been solubilising to the same degree. Veligers ceased all further shell growth while isolated within the female's brood chamber. However, veliger shell growth resumed once females were returned to high-salinity seawater. Our study shows that female isolation of the mantle cavity, often considered an adaptive response to the periodically reduced salinities of estuarine waters, can in fact generate adverse effects on brooded embryos.     

Nest construction and larval behaviour of Bubas bison (L.) and Bubas bubalus (01.) (Coleoptera, Scarabaeidae)

Abstract.

• 1 Female beetles working alone or in cooperation with a male excavated vertical, tunnel-shaped brood chambers. Each chamber was filled with dung to form a cylindrical brood mass which contained two eggs, one near each pole.
• 2 To examine the possible relationship with other Onitini (which lay either one or several eggs per brood mass) factors that influence the two-egg programme were studied. Brood masses with only a single egg were formed if excavation was resumed prematurely. Conversely, when excavation was suppressed several oviposition programmes fused to produce a multi-egg brood mass.
• 3 The larvae repaired their chambers in the typical Scarabaeine manner by building a self-supporting wall formed from their own excrement. This behaviour also prevented direct contact and fighting between adjacent larvae in the same brood mass, and it allowed the larvae to survive inside artificial brood balls. Similar behaviour was observed in larvae of Onthophagus taunts and Ontho-phagus vacca (which develop in one-egg brood masses). The evolution of nesting habits that involve multi-egg brood masses or free-standing brood balls may depend on the pre-existence of this larval repair behaviour.

     

Comparative anatomical study of internal brooding in three anascan bryozoans (Cheilostomata) and its taxonomic and evolutionary implications

The anatomical structure of internal sacs for embryonic incubation was studied using SEM and light microscopy in three cheilostome bryozoans-Nematoflustra flagellata (Waters,1904), Gontarella sp., and Biflustra perfragilis MacGillivray, 1881. In all these species the brood sac is located in the distal half of the maternal (egg-producing) autozooid, being a conspicuous invagination of the body wall. It consists of the main chamber and a passage (neck) to the outside that opens independently of the introvert. There are several groups of muscles attached to the thin walls of the brood sac and possibly expanding it during oviposition and larval release. Polypide recycling begins after oviposition in Gontarella sp., and the new polypide bud is formed by the beginning of incubation. Similarly, polypides in brooding zooids degenerate in N. flagellata and, sometimes, in B. perfragilis. In the evolution of brood chambers in the Cheilostomata, such internal sacs for embryonic incubation are considered a final step, being the result of immersion of the brooding cavity into the maternal zooid and reduction of the protecting fold (ooecium). Possible reasons for this transformation are discussed, and the hypothesis of Santagata and Banta (Santagata and Banta1996) that internal brooding evolved prior to incubation in ovicells is rejected.     

Evolution of bilaterally asymmetrical larvae in freshwater mussels (Bivalvia: Unionoida: Unionidae)

Bilaterally asymmetrical glochidia (i.e. bivalved parasitic larvae bearing a large marginal appendage on a single valve) have been reported from five Asian freshwater mussel genera belonging to two separate subfamilies, the Gonideinae (i.e. Pseudodon, Solenaia, and Physunio) and Rectidentinae (i.e. Contradens and Trapezoideus). This classification requires that the bilaterally asymmetrical glochidium‐bearing mussels are not monophyletic, and suggests that this atypical larval morphology evolved twice in the same geographic region. Although homoplastic glochidium characters are known (e.g. marginal appendages and size), we hypothesized that bilaterally asymmetrical glochidia represent a novel morphological synapomorphy. We tested the monophyly of the mussels bearing bilaterally asymmetrical glochidia using a molecular matrix consisting of representatives from all six freshwater mussel families and three molecular markers (28S, 16S, and COI). Bayesian inference, maximum likelihood, and ancestral state reconstruction were employed to estimate the phylogeny and larval trait transformations. The reconstructed phylogeny rejects the monophyly of the asymmetrical glochidium‐bearing mussels and resolves two putative origins of asymmetrical glochidia; however, ancestral state reconstruction supports asymmetrical glochidia as a synapomorphy of only one supraspecific taxon of the Rectidentinae. In the Gonideinae, asymmetrical glochidia were autapomorphic of Pseudodon cambodjensis (Petit, 1865). That is, no other taxa resolved among the Gonideinae had bilaterally asymmetrical glochidia, including other Pseudodon species. We describe how the alleged intrageneric glochidial variation in Pseudodon, and in the other genera of the Gonideinae reported to have asymmetrical glochidia (i.e. Solenaia and Physunio), challenge the resolved convergence of asymmetrical glochidia. Our results are discussed in the context of freshwater mussel larval evolution, patterns in life‐history traits, and the classification of freshwater mussels generally. © 2015 The Linnean Society of London     

Comparative anatomy of internal incubational sacs in cupuladriid bryozoans and the evolution of brooding in free‐living cheilostomes

Numerous gross morphological attributes are shared among unrelated free‐living bryozoans revealing convergent evolution associated with functional demands of living on soft sediments. Here, we show that the reproductive structures across free‐living groups evolved convergently. The most prominent convergent traits are the collective reduction of external brood chambers (ovicells) and the acquisition of internal brooding. Anatomical studies of four species from the cheilostome genera Cupuladria and Discoporella (Cupuladriidae) show that these species incubate their embryos in internal brooding sacs located in the coelom of the maternal nonpolymorphic autozooids. This sac consists of a main chamber and a narrow neck communicating to the vestibulum. The distal wall of the vestibulum possesses a cuticular thickening, which may further isolate the brood cavity. The presence of this character in all four species strongly supports grouping Cupuladria and Discoporella in one taxon. Further evidence suggests that the Cupuladriidae may be nested within the Calloporidae. Based on the structure of brooding organs, two scenarios are proposed to explain the evolution of the internal brooding in cupuladriids. The evolution of brood chambers and their origin in other free‐living cheilostomes is discussed. Unlike the vast majority of Neocheilostomina, almost all free‐living cheilostomes possess nonprominent chambers for embryonic incubation, either endozooidal and immersed ovicells or internal brooding sacs, supporting the idea that internal embryonic incubation is derived. We speculate that prominent skeletal brood chambers are disadvantageous to a free‐living mode of life that demands easy movement through sediment in instable sea‐floor settings. J. Morphol., 2009. © 2009 Wiley‐Liss, Inc.     

Linking micromorphism,brooding, and hermaphroditism in brachiopods: Insights from Caribbean Argyrotheca (Brachiopoda)

In extant brachiopods, parental brooding of the larvae occurs exclusively within Rhynchonelliformea. Methods of larval protection range from simple retention of the larvae within the mantle cavity, to sophisticated brood care within highly specialized brood pouches found in Argyrotheca and Joania (Terebratulida, Megathyridoidea), Gwynia (Terebratulida, Gwynioidea), and all Thecideoidea (Thecideida). Previous studies on the reproductive biology of Argyrotheca yielded contrasting results on the epithelial origin of the brood pouches in this genus. Here, representatives of different species of Argyrotheca from the Belize Barrier Reef were examined using histological section series. Brood pouches of four species, A. cf. schrammi and Argyrotheca sp. 1–3, are of the same basic structure, formed by invaginations of the anterior body wall and connected to the visceral cavity via the metanephridia. The same four species are simultaneously hermaphroditic, suggesting that fertilization is achieved, at least partly, through selfing. One species, Argyrotheca rubrocostata, differs significantly from all others as it has no brood pouch and gonochoric gonads. Thus, the presence of brood pouches and simultaneous hermaphroditism are concluded to be correlated within Megathyridoidea and proposed to be homologous traits of Joania and several but not all species of Argyrotheca, questioning the monophyletic status of both genera. In contrast to the brood pouches of Thecideoidea, lophophoral epithelium is not involved in the formation of the pouches of Argyrotheca and Joania. Therefore, megathyridoid and thecideoid brood pouches are not homologous but evolved independently within rhynchonelliform brachiopods. All brachiopods with brood pouches share a micromorphic form and a short life span, limiting the space and time available for gamete and larval development. We suggest that the brood pouches and the hermaphroditic gonads of Argyrotheca spp. and Joania compensate these limitations by minimizing the loss of gametes and larvae, and by maximizing the chances of successful fertilization. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

Behavior and development of larvae in the sponge Haliclona amboinensis

Sponges play important roles in marine ecosystems by contributing to habitat complexity and benthopelagic coupling of nutrients. Yet, the reproduction and settlement behaviors of diverse sponge species are not well understood. Here, we examined the brooding demosponge Haliclona amboinensis, which is common on shallow reefs in Bolinao, northwestern Philippines. Gravid sponges were found between the months of May and August, coinciding with warmer sea surface temperature. Sponges released parenchymella larvae from brood chambers in the mid‐morning, suggesting that light and temperature may serve as cues to initiate hatching. Larvae immediately swam toward the surface upon emergence and migrated to the bottom of the tanks 1–2 hr after release. The presence of light and crustose coralline algae induced high larval settlement. Metamorphosis proceeded rapidly in vitro, with larval cells spreading laterally on the substrate. The osculum was first visible at 3 days after settlement. The short pelagic duration of larvae in H. amboinensis promotes local recruitment and may be important for the maintenance of sponge populations in the face of disturbances.     

Methods of DNA extraction and PCR amplification for individual freshwater mussel (Bivalvia: Unionidae) glochidia,with the first report of multiple paternity in these organisms

Freshwater mussels (Unionidae) are among North America's most imperilled organisms. Mussels produce small larvae (glochidia) that parasitize aquatic vertebrates. We modified the Epicentre QuickExtract protocol to extract DNA from a single glochidium, collected directly from the marsupium of a female mussel, to use as template in polymerase chain reactions (PCRs). Yield per glochidium in a 40 µL extraction volume provided enough DNA for ≥ 15 PCRs per individual. We were successful in using this DNA for microsatellite analysis of up to three loci per individual. Offspring from one female showed evidence for multiple paternity within her brood. Our results are the first documentation of this phenomenon in freshwater mussels.     

Early Colony Development in Aetea (Bryozoa)

External structures on the erect parts of zooids of Aetea havebeen demonstrated to be brood chambers by observation of release,settlement and metamorphosis of larvae from the chambers. Theancestrula is smaller than, but very similar to succeeding zooidsin the primary zone of astogenetic change, which do not showtubular connections. Sections through brood chambers and zooidsshow that part of the brood chamber wall may be slightly calcified.Brood chambers appear to be products of the external zooid walland not diverticula derived from the tentacle sheath.     

The effect of larval aggregation behaviour on larval growth of the spruce bark beetle Dendroctonus micans

1. The great spruce bark beetle Dendroctonus micans is a primary pest of spruce in Europe. It is unusual among Eurasian scolytids in that apparently healthy trees are attacked by solitary adults, but larvae feed en masse , in response to a larval aggregation pheromone.
2. The effect of brood size on larval growth was determined in experiments on detached bark, logs and living trees. A positive relationship was found between brood size and larval growth in experiments started with either eggs or larvae up to fifth instar. The relationship appeared to be independent of the effects of both preformed and induced defences in bark.
3. No evidence was found to support the hypothesis that larvae feeding in groups spend a greater proportion of time feeding. Addition of resin to egg chambers in detached bark pieces resulted in high mortality of first-instar larvae. A possible role for larval aggregation in minimizing the effects of host defences is discussed.     

Evolution of parental care and ovulation behavior in oysters

Approximately half of all living oysters brood offspring in the inhalant chamber of their mantle cavities; the remainder are broadcast spawners which do not engage in parental care of young. Ostreid ovulation involves a complex behavioral sequence that results in the countercurrent passage of newly spawned eggs through the gills (ctenidia) and into the inhalant chamber. We constructed molecular and combined-evidence phylogenetic trees to test hypotheses concerning the directionality of parental care evolution, and the evolutionary significance of the trans-ctenidial ovulation pathway, in the Ostreidae. Representatives of all three ostreid subfamilies, together with gryphaeid and nonostreoidean pterioid outgroups, were sequenced for a 941-nucleotide fragment of the 28S ribosomal gene. Our phylogenetic analyses indicate that (1) the Ostreidae are robustly monophyletic, (2) broadcast spawning and larval planktotrophy are ancestral ostreid traits, (3) trans-ctenidial ovulation predates the evolution of parental care in ostreid lineages, and (4) brooding originated once in the common ancestor of the Ostreinae/Lophinae, involved a modification of the final behavioral step in the ancestral ovulation pathway, and has been retained in all descendent lineages. Our data permit an independent test of fossil-based ostreid phylogenetic hypotheses and provide novel insights into oyster evolution and systematics.     

Ultrastructural differentiations in the developing follicle cortex of Locusta migratoria,with special reference to vitelline membrane formation

Summary Electron microscopic studies on developing follicles of Locusta migratoria show the vitelline membrane to be composed of two ultrastructurally distinguishable components: The vitelline membrane bodies (VMBs) and, in addition, fine granular material, cementing the VMBs together. VMBs form first in the oocyte-near zone within the oocyte-follicle cell space. Subsequently, the second vitelline membrane substance is secreted between the VMBs through apical protrusions of the follicle cells. The possible origin of the VMBs is discussed.Yolk uptake in Locusta seems to occur predominantly by pinocytosis. During oocyte development the oocyte membrane is enlarged by numerous microvilli and folds. In addition pinocytotic vesicles are pinched off. It is supposed that the latter loose their coat and eventually transform into large proteid yolk spheres.This work was supported by the Volkswagenstiftung, HannoverI wish to thank Prof. Dr. H. Emmerich, Techn. Hochschule Darmstadt, for valuable discussions     

The role of anchor-tipped larval hairs in the organization of ant colonies

The spatial organization within a social insect colony is a key component of colony life. It influences individual interaction rates, resource distribution, and division of labor within the nest. Yet studies of social insect behavior are most often carried out in artificial constructions, which may change worker behavior and colony organization. We observed how workers of the ant Pheidole rhea organized brood in nests with deep chambers and textured walls that were designed to mimic their natural constructions more closely. Instead of clumping larvae into piles on the chamber floor, workers suspended fourth-instar larvae from the vertical walls and ceiling of each chamber while young larvae and pupae were clumped at the base. Fourth-instar larvae possess five rows of anchor-tipped hairs on their dorsal side, and we predicted that these hairs functioned to attach larvae to the nest walls. We gave larvae "haircuts," where only the anchor-tipped hairs were removed, and then tested their ability to adhere to a textured surface raised to an angle of 90° and then 120° with respect to the horizontal plane. Larvae whose hairs had been clipped came unattached in almost all trials, while larvae whose hairs remained intact stayed attached. This confirmed that anchor-tipped hairs functioned to attach larvae to the walls of the nest. The presence of anchor-tipped hairs is widespread and has been documented in at least 22 genera from the ant subfamily Myrmicinae, including species that occur in a variety of environments and represent a broad range of nesting habits. Based on our results, it is likely that many species exhibit this larval hanging behavior, and this could impact colony characteristics such as spatial organization and the care of developing larvae by nurse workers.