Female genitalia,reproductive cycle and sperm storage in Armadillidium vulgare (Crustacea,Isopoda, Oniscidea)

Light and electron microscopic studies that we have published in the past have reported many aspects of the reproductive process in Armadillidium vulgare with particular emphasis on the reconstruction of female genitalia. Together this body of work provides an almost complete, albeit fragmented picture of these processes and include many data on sperm storage and sperm translocation. Females of A. vulgare have a pair of cuticular genitalia in the lumen of the oviduct. For insemination, these genitalia can receive the copulatory organs of males formed by the elongated tips of the first two pleon endopods. During transitions between reproductive (parturial) and non-reproductive (normal, non-parturial) moult cycles the genitalia undergo intriguing structural changes resulting in two types of genitalia. Throughout their reproductive lifetime, either type is reconstructed after each moult depending on the reproductive phase of the female. In this review, we integrate the events that occur during a reproductive cycle with particular emphasis on the genitalia reconstruction and sperm storage, and discuss functional aspects of the genitalia. Thereby, we provide a case model that can be useful for further studies on genitalia diversity and female reproductive strategies in terrestrial isopods.     

The role of invertebrates in seedling establishment in a heterocarpic plant,Atriplex sagittata

Seed heteromorphism is a marked character of many Chenopodioideae (Amaranthaceae). Seed morphs differ in dormancy, germination and seedling biology, but differences in their predation have not yet been studied. Atriplex sagittata produces small black dormant and large brown non‐dormant seeds. In this study, the timing of seed release and seedling establishment were ascertained, and their consumption by invertebrates (carabids, isopods and slugs) was studied. Seeds dispersed in the autumn passed the winter on the ground surface, protected from invertebrate predation by low temperatures. In the following vegetative season, ungerminated black seeds exposed to predation on ground surface were preferred by a large carabid species, Pseudoophonus rufipes. Some black and all brown seeds escaped predation by germinating in early spring. The seedlings were little endangered by carabids and isopods but were preferred by an invasive slug, Arion vulgaris, the feeding of which can exterminate seedlings at places in which slugs are abundant. Invertebrate predation is important factor of seed and seedling mortality of A. sagittata and seed heteromorphism modifies its intensity and timing.     

Bacterial symbionts in the hepatopancreas of isopods: diversity and environmental transmission

The midgut glands (hepatopancreas) of terrestrial isopods contain bacterial symbionts. We analysed the phylogenetic diversity of hepatopancreatic bacteria in isopod species from various suborders colonizing marine, semiterrestrial, terrestrial and freshwater habitats. Hepatopancreatic bacteria were absent in the marine isopod Idotea balthica (Valvifera). The symbiotic bacteria present in the midgut glands of the freshwater isopod Asellus aquaticus (Asellota) were closely related to members of the proteobacterial genera Rhodobacter, Burkholderia, Aeromonas or Rickettsiella, but differed markedly between populations. By contrast, species of the suborder Oniscidea were consistently colonized by the same phylotypes of hepatopancreatic bacteria. While symbionts in the semiterrestrial isopod Ligia oceanica (Oniscidea) were close relatives of Pseudomonas sp. (Gammaproteobacteria), individuals of the terrestrial isopod Oniscus asellus (Oniscidea) harboured either 'Candidatus Hepatoplasma crinochetorum' (Mollicutes) or 'Candidatus Hepatincola porcellionum' (Rickettsiales), previously described as symbionts of another terrestrial isopod, Porcellio scaber. These two uncultivated bacterial taxa were consistently present in each population of six and three different species of terrestrial isopods, respectively, collected in different geographical locations. However, infection rates of individuals within a population ranged between 10% and 100%, rendering vertical transmission unlikely. Rather, feeding experiments suggest that 'Candidatus Hepatoplasma crinochetorum' is environmentally transmitted to the progeny.     

Sex Biased State Dependence in Natal Dispersal in Desert Isoponds, Hemilepistus reaumuri

Differences in the emergence, movement, and settling patterns of individuals during natal dispersal can provide testable hypotheses about the costs and functions of movement. Emergence, movement, and settling patterns were studied in desert isopods, Hemilepistus reaumuri. The young of this semelparous, monogamous, crustacean emerge from their natal burrows each spring and search for sites to establish new burrows or gain acceptance as mates in occupied burrows. Dispersal was measured in a long, narrow corridor into which individuals marked after emergence were monitored. Females emerged slightly earlier than males with substantial overlap. Size or condition varied with time before settling differently in males and females. Isopods in good or poor condition did not differ in distance traveled, but males in good condition took more time before settling. Small males were more likely to start new burrows and took less time before settling, suggesting they might be acting in anticipation of losing contests for female-initiated burrows. Larger females and those in higher condition were more likely to start new burrows and took less time before settling. The pattern in females could reflect male choice or constraints or costs associated with burrow establishment in females, which should be tested. Measures of dispersal based on recaptures of traveling or recently settled individuals may differ from the distribution of successful reproduction. In this study travelers were observed at shorter average distances than settlers, but successful settlers traveled less far than unsuccessful ones.     

Olencira praegustator (Crustacea, Isopoda, Cymothoidae) parasitic on Brevoortia species (Pisces, Clupeidae) from the southeastern coasts of North America: review and re-description

The cymothoid isopod Olencira praegustator (Latrobe, 1802), the sole species of the genus Olencira Leach, 1818, has been the subject of several previous studies, but has remained incompletely described. This species is re-described and figured from the Atlantic menhaden Brevoortia tyrannus (Latrobe, 1802), the type host from the estuarine systems of the South Carolina coast, USA. The general morphology, mouthparts and appendages of the female, male and other stages of its lifecycle are described.

The geographical distribution and hosts recorded for O. praegustator are reviewed. Biological data are summarized and discussed. Areas that need additional studies include the infection process and the effect of the parasite on its host.     

罗氏沼虾中等足类AGH类似物的分离与鉴定

从2l30尾性成熟的雄性罗氏沼虾体内采集雄性腺体(AG),匀浆后,分离沉淀等电点为4.5左右的多肽,用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳法收集分子量从17kDa至l8kDa的多肽条带.进一步应用高效液相色谱、无胶筛分高效毛细管电泳、基质辅助激光解吸电离飞行时间质谱、高效液相色谱-电喷雾电离-质谱等技术进行分离与鉴定.结果显示,主要组分的分子量为17436±110u,在等电点4.5的条件下分离得到的罗氏沼虾AG组分中,以分子量17480u的多肽组分为主,与等足类ArmadillidiumvulgareAGH的分子量相似,暂称为等足HAGH类似物.     

Structure and foraging behavior in hypogean crustacean assemblages

Varying assemblages of three crustaceans and their behavioral interactions were studied in Rice Cave during eight visits over a two year period. The assemblages of crustaceans observed were seen to depend primarily on periodic invasions into the cave byGammarus troglophilus, low resource levels, habitat preference, the sensitivity ofCaecidotea stygia to disturbance, and subterranean adaptation by the troglobites.Both the troglophilG. troglophilus and the troglobite,C. stygia preferred mud and gravel bottomed pools. The more active and aggressiveG. troglopholus when at high densities eliminatedC. stygia from preferred habitat and baited food placed in it.Bactrurus brachycaudus, a troglobite, preferred riffles, but was able to compete for baited food withG. troglophilus by virtue of its larger size and similar behaviors. When onlyC. stygia was present at baited sites access to food was size-related with a rotation of large and small individuals on and off the bait occurring.     

Response of the waterlouse Asellus aquaticus to multiple stressors: effects of current velocity and mineral substratum

Experiments were performed to study theindividual and combined effects of currentvelocity and substratum composition on thewaterlouse Asellus aquaticus (L.). Bothfactors affected growth, mortality, behavior,and food consumption of A. aquaticus.Short-term effects of increasing currentvelocity depended on the type of substratum. Critical currentvelocity for detachment was almost the same onsand as on a polished surface whereas on gravelA. aquaticus could withstand highercurrent velocities by hiding in interstitialspaces. Long-term experiments with differentcombinations of current velocity and substratumcomposition showed that current velocity had agreater effect than substratum on survival andgrowth. Substratum, however, had a greaterinfluence on the distribution of individuals inthe experimental units. Since growth wasreduced at high current velocity and no changesin levels of food intake were observed it isconcluded that a substantial amount of energyis required for withstanding current at higherflow rates. Furthermore, mortality showed astrong inverse correlation to growth. Theinteraction of effects of natural habitatfactors may be better understood using anexperimental and modeling approach focusing onenergy budgets.     

Evidence for Permo-Triassic colonization of the deep sea by isopods

The deep sea is one of the largest ecosystems on Earth and is home to a highly diverse fauna, with polychaetes, molluscs and peracarid crustaceans as dominant groups. A number of studies have proposed that this fauna did not survive the anoxic events that occurred during the Mesozoic Era. Accordingly, the modern fauna is thought to be relatively young, perhaps having colonized the deep sea after the Eocene/Oligocene boundary. To test this hypothesis, we performed phylogenetic analyses of nuclear ribosomal 18S and 28S and mitochondrial cytochrome oxidase I and 16S sequences from isopod crustaceans. Using a molecular clock calibrated with multiple isopod fossils, we estimated the timing of deep-sea colonization events by isopods. Our results show that some groups have an ancient origin in the deep sea, with the earliest estimated dates spanning 232–314 Myr ago. Therefore, anoxic events at the Permian–Triassic boundary and during the Mesozoic did not cause the extinction of all the deep-sea fauna; some species may have gone extinct while others survived and proliferated. The monophyly of the ‘munnopsid radiation’ within the isopods suggests that the ancestors of this group evolved in the deep sea and did not move to shallow-water refugia during anoxic events.