The functional significance of lateral line canal morphology on the trunk of the marine teleost Xiphister atropurpureus (Stichaeidae)

We investigated the filter properties of the highly branched trunk lateral lines of the stichaeid Xiphister atropurpureus and compared them to the filter properties of simple lateral line canals. For this purpose artificial canals were constructed, some of which were fitted with artificial neuromasts. In still water, the response of a simple canal versus two types of Xiphister-like canals to a vibrating sphere stimulus were similar, as was the decrease in the responses as a function of sphere distance. Also comparable was the mechanical coupling between neighboring parts of the main canal. However, compared to the simple canal, the Xiphister-like canals showed a lower spatial resolution. Equipping artificial lateral line canals with artificial neuromasts revealed that Xiphister-like canals, i.e., lateral lines canals with tubuli that contained widely spaced pores, improve the signal-to-noise ratio in a highly turbulent environment. Even though a reduced spatial resolution is the price for this improvement, Xiphister may compensate for this compromise by having four instead of the usual single trunk lateral line canal. We suggest that lateral line canals with tubuli that contain widely spaced pores and multiple lateral line canals on each body side are an adaptation to a highly turbulent aquatic environment.     

The growth and degeneration of the hydroid Sertularia perpusilla,an obligate epiphyte of leaves of the seagrass Posidonia oceanica

The hydrorhizae of Sertularia perpusilla colonies that originate from stolon attachments initially grow up and down Posidonia leaves. After a short time the distal hydroid tissue degenerates concurrently with the downward growth of the proximal hydrorhiza onto younger sections of the leaves. Consequently the hydroids move down the leaves which grow upward from a basal meristem. In situ inversion of leaves had no effect on either the orientation or the rates of growth and degeneration. This indicates that orientation may be in response to age related features of leaf tissue rather than to light, gravity or water movement, the directions of which were reversed by inverting the leaves. However, orientation of growth of new hydroids from attached stolons is immediate, probably before the hydroid colony is long enough to be able to detect an age gradient. This paradox could be explained if initial orientation were based on the direction of gravity or light but subsequent growth were directed along the age gradient. For hydroids in the size range studied there was a relation between growth rate and number of hydranths. Thus growth rate may be limited by food rather than by there being only one growing tip of the hydrorhizae.     

An invasive ant species able to counterattack marabunta raids

In the Neotropics where it was introduced, the invasive ant Pheidole megacephala counterattacked raids by the army ants Eciton burchellii or E. hamatum. The Eciton workers that returned to their bivouac were attacked and spread-eagled and most of them killed by their outgoing colony mates. Little by little the zone where returning and outgoing Eciton workers encountered one another moved away from the Pheidole nest which was no longer attacked, so that most of the colony was spared. Using a water-based technique rounded out by bioassays, we show that Pheidole compounds were transferred onto the Eciton cuticle during the counterattacks, so that outgoing workers do not recognize returning colony mates, likely perceived as potential prey. Because P. megacephala is an introduced African species, this kind of protection, which cannot be the result of coevolutive processes, corresponds to a kind of by-product due to its aggressiveness during colony defence.     

Recognition in a Social Symbiosis: Chemical Phenotypes and Nestmate Recognition Behaviors of Neotropical Parabiotic Ants

Social organisms rank among the most abundant and ecologically dominant species on Earth, in part due to exclusive recognition systems that allow cooperators to be distinguished from exploiters. Exploiters, such as social parasites, manipulate their hosts’ recognition systems, whereas cooperators are expected to minimize interference with their partner’s recognition abilities. Despite our wealth of knowledge about recognition in single-species social nests, less is known of the recognition systems in multi-species nests, particularly involving cooperators. One uncommon type of nesting symbiosis, called parabiosis, involves two species of ants sharing a nest and foraging trails in ostensible cooperation. Here, we investigated recognition cues (cuticular hydrocarbons) and recognition behaviors in the parabiotic mixed-species ant nests of Camponotus femoratus and Crematogaster levior in North-Eastern Amazonia. We found two sympatric, cryptic Cr. levior chemotypes in the population, with one type in each parabiotic colony. Although they share a nest, very few hydrocarbons were shared between Ca. femoratus and either Cr. levior chemotype. The Ca. femoratus hydrocarbons were also unusually long–chained branched alkenes and dienes, compounds not commonly found amongst ants. Despite minimal overlap in hydrocarbon profile, there was evidence of potential interspecific nestmate recognition –Cr. levior ants were more aggressive toward Ca. femoratus non-nestmates than Ca. femoratus nestmates. In contrast to the prediction that sharing a nest could weaken conspecific recognition, each parabiotic species also maintains its own aggressive recognition behaviors to exclude conspecific non-nestmates. This suggests that, despite cohabitation, parabiotic ants maintain their own species-specific colony odors and recognition mechanisms. It is possible that such social symbioses are enabled by the two species each using their own separate recognition cues, and that interspecific nestmate recognition may enable this multi-species cooperative nesting.     

Physoschistura chindwinensis, a new balitorid loach from Chindwin basin, Manipur, India (Teleostei: Balitoridae)

Physoschistura chindwinensis, a new balitorid species, is described from the Chindwin basin, Manipur, India. It is easily distinguished from congeners by the combination of characters: a dorsal fin with three simple and 8? branched rays; body with 13–17 dark-brown bars on the sides, and 11–16 dark-brown saddles; interorbital space with a rectangular dark-brown shield-like mark; a caudal fin with 8?+?8 branched rays; a moderately developed axillary pelvic lobe; males with a suborbital flap; preoperculomandibular canal with seven pores; and an air bladder with a well-formed free posterior chamber.     

Associative Nitrogen Fixation by Klebsiella spp.: Adhesion Sites and Inoculation Effects on Grass Roots

Adhesion sites on grass roots for Klebsiella strains carrying type 3 or type 1 fimbriae or both were determined. Adhesion of the strains to the roots of Poa pratensis and Festuca rubra was highly localized; the bacteria adhered strongly to root hairs and with a markedly lower efficiency to the surface of the zone of elongation and to the root cap mucilage. No adhesion to the epidermal cells between root hairs was observed. The adhesion sites were identical for the type 3- and 1-fimbriated bacteria and for P. pratensis, F. rubra, and Trifolium pratense. Inoculation of P. pratensis seedlings with Klebsiella pneumoniae strain As resulted in morphological changes in plant roots. The roots of infected plants were heavily covered with root hairs, which often were deformed and branched.     

Foraging tempo in two woodland and species

Running speeds of Myrmica punctiventris and Aphaenogaster rudis workers were measured, and a good correspondence between laboratory and field behaviour was obtained. In the laboratory, foraging tempo and foraging efficiency were calculated for two colony sizes and five patterns of prey availability. Running speeds were strongly dependent on colony size for both species; when retrieving prey, foragers from large colonies ran significantly faster than those from small colonies. In addition, ants searching for prey ran more slowly than those returning to the nest with prey. Efficiency, measured as the propensity to return to the nest in a straight line, was most strongly a function of distance from the nest. Finally, no relationship between an ant's speed and its efficiency of return was found.     

Ceramides: Branched alkyl chains in the sphingolipid siblings of diacylglycerol improve biological potency

The synthesis of a small number of ceramide analogues containing a combination of linear and highly branched alkyl chains on either the d-sphingosine or the N-acyl core of the molecule is reported. Regardless of location, the presence of the branched chain improves potency relative to the positive control, C2 ceramide; however, the most potent compound (4) has the branched side chain as part of the d-sphingosine core. The induction of apoptosis by 4 in terms of Annexin V binding and DiOC₆ labeling was superior to that achieved with C2 ceramide.     

Interaction of the tracheal tubules of Scutigera coleoptrata (Chilopoda,Notostigmophora) with glandular structures of the pericardial septum

Notostigmophora (Scutigeromorpha) exhibit a special tracheal system compared to other Chilopoda. The unpaired spiracles are localized medially on the long tergites and open into a wide atrium from which hundreds of tracheal tubules originate and extend into the pericardial sinus. Previous investigators reported that the tracheal tubules float freely in the hemolymph. However, here we show for the first time that the tracheal tubules are anchored to a part of the pericardial septum. Another novel finding is this part of the pericardial septum is structured as an aggregated gland on the basis of its specialized epithelium being formed by hundreds of oligocellular glands. It remains unclear whether the pericardial septum has a differently structure in areas that lack a connection with tracheal tubules. The tracheal tubules come into direct contact with the canal cells of the glands that presumably secrete mucous substances covering the entire luminal cuticle of the tracheal tubules. Connections between tracheae and glands have not been observed in any other arthropods.     

Genetic modification of the inner ear lateral semicircular canal phenotype of the Bmp4 haplo-insufficient mouse

In the mouse, development of the lateral semicircular canal of the inner ear is sensitive to Bmp4 heterozygosity. In the C57BL6 background 30% of the heterozygotes display circling behavior, 66% have a specific defect in the vestibular part of the inner ear, namely the constriction, interruption or absence of the lateral semicircular canal. Only mice having both ears affected display circling behavior. In the (C57BL6xCBA)N1 background, the penetrance of the canal phenotype is greatly reduced, and bilateral lateral canal defect is not sufficient to induce circling. We found association of the canal phenotype with the genotype of markers on chromosome 14 and 4, co-localizing with Ecs and Eclb identified in the Ecl mouse with similar lateral canal defects. Candidate genes to contain the causal mutation are Bmp4 on chromosome 14, and Rere on chromosome 4.     

Cephalic lateral line systems in the Far Eastern species of the genus Phoxinus (Cyprinidae)

The cephalic lateral line systems of seven Far Eastern Phoxinus species (P. phoxinus, P. kumgangensis, P. semotilus, P. lagowskii, P. oxycephalus, P. perenurus, and P. czekanowskii) were investigated. In this genus, the infraorbital canal is not connected with either the supraorbital canal or the preoperculomandibular canal. Phoxinus phoxinus is unique for having an underdeveloped condition, such as canal formation or remaining as uncovered. A unified supraorbital canal was observed in all species, but the infraorbital canal of both P. perenurus and P. czekanowskii was not unified into a single canal throughout their development. Unification between both sides of the supratemporal canal occurred in larger individuals of P. lagowskii, P. oxycephalus, and P. czekanowskii. The preoperculomandibular canal of P. kumgangensis, large P. lagowskii, and large P. oxycephalus was unified. The pore number of each part of the canal system also varied depending on the species. Intraspecific variations were observed between Korean and Japanese specimens of P. lagowskii in the unification of the supratemporal canal and the preoperculomandibular canal, and the number of pores of the supratemporal canal. It was inferred that the specific characteristic patterns of their cephalic lateral line systems reflected the following two factors: different environmental requirement for their microhabitat and different maximum body size.     

Construction and Use of a Nonradioactive DNA Hybridization Probe for Detection of Pseudomonas syringae pv. Tomato on Tomato Plants

Pseudomonas syringae pv. tomato, the causal agent for bacterial speck of tomato, produces the phytotoxin coronatine. A 5.3-kilobase XhoI fragment from the chromosomal region controlling toxin production was cloned into the plasmid pGB2, and the resulting recombinant plasmid, pTPR1, was tested for its ability to serve as a diagnostic probe for P. syringae pv. tomato. In a survey of 75 plant-associated bacteria, pTPR1 hybridized exclusively to those strains that produced coronatine. The detection limit for this probe, which was labeled with the Chemiprobe nonradioactive reporter system, was approximately 4 × 10³ CFU of lesion bacteria. During the 1989 growing season, a total of 258 leaf and fruit lesions from nine tomato fields were screened for P. syringae pv. tomato by using pTPR1 and the culture method of detection. The best agreement between the two methods, 90%, occurred early in the season with samples taken from relatively young (5-week-old) plants. Young plants also had a higher percentage of P. syringae pv. tomato-positive lesions. P. syringae pv. tomato was the only coronatine producer recovered from the nine tomato fields. All 244 P. syringae pv. tomato strains isolated during this study reacted strongly with the probe. The P. syringae pv. tomato population of healthy field tomato leaves was determined by a pTPR1 colony hybridization procedure. Every probe-positive colony that was isolated and characterized was identified as P. syringae pv. tomato. The pTPR1 probe should expedite disease diagnosis and facilitate epidemiological studies of this pathogen. It also should aid in screening transplant seedlings for bacterial speck infestation.     

Probabilistic transition from unstable predator-prey interaction to stable coexistence of Dictyostelium discoideum and Escherichia coli

Predator-prey interactions have been found at all levels within ecosystems. Despite their ecological ubiquity and importance, the process of transition to a stable coexistent state has been poorly verified experimentally. To investigate the stabilization process of predator-prey interactions, we previously constructed a reproducible experimental predator-prey system between Dictyostelium discoideum and Escherichia coli, and showed that the phenotypically changed E. coli contributed to stabilization of the system. In the present study, we focused on the transition to stable coexistence of both species after the phenotypic change in E. coli. Analysis of E. coli cells isolated from co-culture plates as single colony enabled us to readily identify the appearance of phenotypically changed E. coli that differed in colony morphology and growth rate. It was also demonstrated that two types of viscous colony, i.e., the dense-type and sparse-type, differing in spatial distribution of both species emerged probabilistically and all of the viscous colonies maintained stably were of the sparse-type. These results suggest that the phenotypically changed E. coli may produce two types of viscous colonies probabilistically. The difference in spatial distribution would affect localized interactions between both species and then cause probabilistic stabilization of predator-prey interactions.     

Formation of the paratomic fission zone in freshwater oligochaetes

Oligochaetes Nais communis and Pristina longiseta are capable of paratomy, i.e., asexual reproduction of the cross division type, when division proceeds across the long body axis and daughter organisms retain the maternal axes. Paratomy is represented by two forms: slow and rapid. Slow paratomy is accompanied by the formation of chains from no more than two zooids (N. communis), while rapid paratomy leads to the formation of chains from many zooids (P. longiseta). Analysis of the appearance and development of the zone of paratomy (constriction) has shown that when its cephalogenic part is formed, only head segments appear and are formed simultaneously, while in the somatogenic part, trunk segments appears successively. Dedifferentiated cells of the integumental epithelium appear to serve as a source of newly formed structures. It was shown using mathematical statistics that constriction is laid down in the zone defined by a system of coordinates formed by unknown factors. Although the constriction is laid down in the middle of a segment, its subsequent growth is not related to the transformation of adjacent areas of the segment.     

The Evolution of Extreme Polyandry in Social Insects: Insights from Army Ants

The unique nomadic life-history pattern of army ants (army ant adaptive syndrome), including obligate colony fission and strongly male-biased sex-ratios, makes army ants prone to heavily reduced effective population sizes (N _e). Excessive multiple mating by queens (polyandry) has been suggested to compensate these negative effects by increasing genetic variance in colonies and populations. However, the combined effects and evolutionary consequences of polyandry and army ant life history on genetic colony and population structure have only been studied in a few selected species. Here we provide new genetic data on paternity frequencies, colony structure and paternity skew for the five Neotropical army ants Eciton mexicanum, E. vagans, Labidus coecus, L. praedator and Nomamyrmex esenbeckii; and compare those data among a total of nine army ant species (including literature data). The number of effective matings per queen ranged from about 6 up to 25 in our tested species, and we show that such extreme polyandry is in two ways highly adaptive. First, given the detected low intracolonial relatedness and population differentiation extreme polyandry may counteract inbreeding and low N _e. Second, as indicated by a negative correlation of paternity frequency and paternity skew, queens maximize intracolonial genotypic variance by increasingly equalizing paternity shares with higher numbers of sires. Thus, extreme polyandry is not only an integral part of the army ant syndrome, but generally adaptive in social insects by improving genetic variance, even at the high end spectrum of mating frequencies.     

Development of the stratified squamous epithelium of the human tympanic membrane and external canal: the origin of auditory epithelial migration

The development of the stratified squamous epithelium of the tympanic membrane and external canal was studied in 167 embryonic, fetal, and postnatal human ears. It originates as a tube derived from the epithelium of the fundus of the primary external canal (zone 1). The tube is composed of a thin, flat epithelium on the medial side (zone 2), continuous with a thicker one (zone 3) on the lateral side; zone 3 thereafter merges with the external epithelium of the primary external canal (zone 4). Proliferative activity, as indicated by a thickened epithelium, with rete ridges in later fetal life, is present mainly in zones 1 and 3. Cornification at 18 weeks gestation is followed by clearing of keratinous debris to the exterior. Subsequently the canal widens, zone 1 now covering the pars flaccida region, a tongue-shaped area passing inferiorly from it and a part of the postero-superior deep canal adjacent to it; zone 2 covers the pars tensa and zone 3 most of the deep external canal. On the basis of the original embryonic growth, migratory epithelial movement throughout life is postulated to be generated in zone 1 by mitotic interposition and then to pass to zone 2. It then moves en masse through to zone 3, where unilateral progression by mitotic means takes the epithelium up to the cartilaginous canal. Such a pathway is approximately that seen in the marked, living eardrum and canal.     

Colony-size effects on task organization in the harvester ant Pogonomyrmex californicus

Colony size is a fundamental attribute of insect societies that appears to play an important role in their organization of work. In the harvester ant Pogonomyrmex californicus, division of labor increases with colony size during colony ontogeny and among unmanipulated colonies of the same age. However, the mechanism(s) integrating individual task specialization and colony size is unknown. To test whether the scaling of division of labor is an emergent epiphenomenon, as predicted by self-organizational models of task performance, we manipulated colony size in P. californicus and quantified short-term behavioral responses of individuals and colonies. Variation in colony size failed to elicit a change in division of labor, suggesting that colony-size effects on task specialization are mediated by slower developmental processes and/or correlates of colony size that were missing from our experiment. In contrast, the proportional allocation of workers to tasks shifted with colony size, suggesting that task needs or priorities depend, in part, on colony size alone. Finally, although task allocation was flexible, colony members differed consistently in task performance and spatial tendency across colony size treatments. Sources of interindividual behavioral variability include worker age and genotype (matriline).     

Incorporation of labelled dietary n-alkanes into cuticular lipids of the grasshopper Melanoplus sanguinipes

Dietary hydrocarbons are incorporated into cuticular lipids of the grasshopper Melanoplus sanguinipes. Dietary secondary alcohols and ketones, however, are not incorporated into the cuticular lipids. In typical experiments from 8 to 28 per cent of the fed labeled n-alkanes are recovered in the cuticular lipids. Most of the radioactivity recovered from feeding the C₂₃ n-alkane and a significant amount from the C₂₅ was found as a secondary alcohol in the form of a wax ester. The C₂₉ and C₃₁ n-alkanes were recovered primarily unchanged as the n-alkane. Eighty-five per cent of injected acetate incorporated into the hydrocarbon fraction is in the branched hydrocarbons. These results show that the insect synthesizes its branched hydrocarbons, whereas a large part of the normal hydrocarbons can be dietary.     

Cladophialophora abundans,a novel species of Chaetothyriales isolated from the natural environment

A novel species of Cladophialophora is described from the natural environment of the mangrove land crab (Ucides cordatus) along the coast, and from plant sources in Brazil. It is morphologically very similar to Cladophialophora bantiana, though with moderately melanized conidia produced in strongly coherent and poorly branched chains which arise directly from undifferentiated hyphae, but deviates unambiguously on the basis of molecular phylogeny. The species has a maximum growth temperature of 36 °C and seems to be a strict saprobe.