Coexistence of permanently territorial cichlids of the genus Petrochromis through male-mating attack

Coexistence mechanisms of permanently territorial fishes proposed hitherto have been mainly based on interspecific competition. To test the hypothesis of the coexistence through male-mating aggression (Kohda, 1995a), spacing patterns of feeding territories of three coexisting herbivorous cichlids, Petrochromis polyodon, P. trewavasae and P. famula, were investigated in a homogeneous habitat at a shallow rocky shore in Lake Tanganyika. All three species maintained individual feeding territories that were defended against both conspecifics and congenerics and rarely overlapped either intra- or interspecifically. Territories of three species were scattered and covered almost all rocky bottoms. Territorial attacks usually occurred near the border of feeding territories. But male P. polyodon, the largest and socially most dominant fish, attacked conspecific males far beyond their feeding territories, which were widely separated. Removal of some territory owners suggested that such attacks result in the separate distribution of male P. polyodon territories. The interstitial space between P. polyodon feeding territories resulting from their mating aggression can be occupied by subordinate congeneric fishes. Male-mating attack of dominant males of Petrochromis will facilitate the coexistence of other congeners.     

A comparative study of territoriality in intertidal and subtidal blennioids (Teleostei, Blennioidei)

This paper presents a comparative analysis of territoriality in three intertidal (Lipophrys pholis, Coryphoblennius galerita, Salaria pavo) and two subtidal (Tripterygion delaisi, Parablennius pilicornis) blennioid fishes. Focal-animal observations of males guarding eggs showed that: (i) intertidal species had smaller territories that were less frequently patrolled; (ii) in subtidal species feeding was limited to the territory, while in intertidal fishes a substantial proportion of the feeding acts occurred outside the defended area; (iii) intertidal species spent less time out of the nest and showed a lower level of locomotory activity; (iv) subtidal species were subjected to a higher number of territorial intrusions with more species intruding their territory, some of them potential egg predators; (v) subtidal species performed several water column displays that played a significant role in courtship, while in intertidal fishes these displays are almost absent. Signalling without the presence of a female was almost absent in intertidal species. It is argued that intertidal fishes minimize the time spent out of the nest and the loss of contact with the substrate, features that may be of high survival value in conditions of strong turbulence. Although intertidal species have a reduced time available for feeding, this may be compensated by lower levels of locomotory activity, territorial defense and risk of egg predation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Group foraging by the herbivorous cichlid fish,Petrochromis fasciolatus,in Lake Tanganyika

Group foraging of the algae eating cichlid,Petrochromis fasciolatus, was studied along a rocky shore in Lake Tanganyika, in an area occupied by the feeding territories of several herbivorous cichlid species. SolitaryP. fasciolatus or schools comprising a few members only were nearly always repelled from such territories, although larger schools (40–250 individuals) ofP. fasciolatus were able to overwhelm the defenses of territory owners and enable subsequent foraging. The frequency and duration of individual foraging sessions on the algal mats were positively correlated with group size, probably owing to individuals in large schools suffering fewer attacks from territory owners. Almost all of the foraging sites ofP. fasciolatus were inside the territories of other herbivorous cichlids, especially those ofNeolamprologus moorii (more than 80% of total), in which the algal density was more than 10 times that in territories of the other species.N. moorii territories included only 4% rocky substrate, indicating that schools ofP. fasciolatus selectively chose territories containing rich resources.     

Differences in motor unit behavior during isometric contractions in patients with diabetic peripheral neuropathy at various disease severities

The aim of this study was to determine whether HD-sEMG is sensitive to detecting changes in motor unit behavior amongst healthy adults and type 2 diabetes mellitus (T2DM) patients presenting diabetic peripheral neuropathy (DPN) at different levels. Healthy control subjects (CON, n = 8) and T2DM patients presenting no DPN symptoms (ABS, n = 8), moderate DPN (MOD, n = 18), and severe DPN (SEV, n = 12) performed isometric ankle dorsiflexion at 30 % maximum voluntary contraction while high-density surface EMG (HD-sEMG) was recorded from the tibialis anterior muscle. HD-sEMG signals were decomposed, providing estimates of discharge rate, motor unit conduction velocity (MUCV), and motor unit territory area (MUTA). As a result, the ABS group presented reduced MUCV compared to CON. The groups with diabetes presented significantly larger MUTA compared to the CON group (p < 0.01), and the SEV group presented a significantly lower discharge rate compared to CON and ABS (p < 0.01). In addition, the SEV group presented significantly higher CoV_force compared to CON and MOD. These results support the use of HD-SEMG as a method to detect peripheral and central changes related to DPN.     

Marking of host fruit by maleRhagoletis boycei Cresson flies (Diptera: Tephritidae) and its effect on egg-laying

MaleRhagoletis boycei flies (Cresson) have been shown previously to guard egg-laying punctures on host walnut (Juglans major) fruit. During their tenure,R. boycei males were observed to dip the posterior portion of their abdomen repeatedly toward the fruit surface. Closeup video analysis revealed that, during this dipping behavior, a clear viscous substance emanating from the cercus was deposited directly on the fruit. Laboratory assays indicated that the rate of abdomen-dipping was significantly higher on fruit bearing simulated egg-laying punctures than on control fruit and significantly higher in the area of the puncture than elsewhere on the fruit. In a final experiment, the occurrence of abdomen-dipping in the vicinity of a puncture was manipulated independently on separate punctures on the same fruit. On such fruit and in the absence of males, previously mated, reproductively mature females attempted oviposition significantly more often in or near a puncture exposed to males than in or near an unexposed control puncture. Possible functions of the putative male-marking behavior from the perspectives of both male and female are discussed.     

Exploring landscape structure effect on termite territory size using a model approach

The foraging territory of the Formosan subterranean termite, Coptotermes formosanus Shiraki, was simulated by using a lattice model in order to study how landscape structure affects the foraging territory. Three kinds of landscape were generated on lattice space: ideal, random and fractal landscape. Each lattice cell had a value ranging from 0.0 to 1.0, interpreted as transition probability, P_trans, which represents spatially distributed property of the landscapes. The heterogeneity of the fractal landscape was characterized by a parameter, H, controlling aggregation of lattice cells with higher value of P_trans. Higher H values corresponded to higher aggregation levels. The model made use of minimized local rules based on empirical data that determines the development of the foraging territory. Additionally, seasonal cycle (summer and winter season), and obstacles which hinder the growth of the territory were incorporated in the model as environmental variables. Territory size was largest in the ideal landscape while it was larger in the random landscape than in the fractal landscape. As obstacle density increased, the territory size decreased. In the fractal landscape, the territory size increased, decreased, and increased again as H increased.     

Direct benefits and costs for hybridizing Ficedula flycatchers

It is well understood that females may gain direct benefits from breeding with attractive males. However, the direct fitness effects of mate-choice are rarely considered with respect to mating between different species (hybridization), a field dominated by discussion of indirect costs of producing unfit hybrid offspring. Hybridizing females may also gain by the types of direct benefits that are important for intraspecific mate choice, and in addition may have access to certain benefits that are restricted to mating with males of an ecologically diverged sister-taxon. We investigate possible direct benefits and costs female Ficedula flycatchers gain from breeding with a heterospecific male, and demonstrate that hybridizing female collared flycatchers (F. albicollis) breed in territories that do not suffer the seasonal decline in habitat quality experienced by females breeding with conspecifics. We exclude the hypotheses that heterospecific males provide alternative food-types or assume a greater amount of the parental workload. In fact, the diets of the two species (F. albicollis and F. hypoleuca) were highly similar, suggesting possible interspecific competition over food resources in sympatry. We discuss the implications of direct fitness effects of hybridization, and why there has been such a disparity in the attention paid to such benefits and costs with regard to intraspecific and interspecific mate-choice.     

Evaluation of Habitat Suitability Models for Forest Passerines Using Demographic Data

ABSTRACT Habitat suitability is often used as a surrogate for demographic responses (i.e., abundance, survival, fecundity, or population viability) in the application of habitat suitability index (HSI) models. Whether habitat suitability actually relates to demographics, however, has rarely been evaluated. We validated HSI models of breeding habitat suitability for wood thrush (Hylocichla mustelina) and yellow-breasted chat (Icteria virens) in Missouri, USA. First, we evaluated HSI models as a predictor of 3 demographic responses: within-site territory density, site-level territory density, and nest success. We demonstrated a link between HSI values and all 3 types of demographic responses for the yellow-breasted chat and site-level territory density for the wood thrush. Second, we evaluated support for models containing HSI values, models containing measured habitat features (e.g., tree age, tree species, ecological land type), and models containing management treatments (e.g., even-aged and uneven-aged forest regeneration treatments) for each demographic response using model selection. Models containing HSI values received more support, in general, than models containing only habitat features or management treatments for all 3 types of wildlife response. The assumption that changes in habitat suitability represent wildlife demographic response to vegetation change is supported by our models. However, differences in species ecology may contribute to the degree to which HSI values are related to specific demographic responses. We recommend validation of HSI models with the particular demographic data of interest (i.e., density, productivity) to increase confidence in the model used for conservation planning.     

Pheromone deposition on leaf territories by male Caribbean fruit flies,Anastrepha suspensa (loew) (Diptera: Tephritidae)

Male Caribbean fruit flies apply everted anal membranes associated with pheromone glands to the substrate while on leaf territories. There is a peak in abdominal dipping at the onset of the photoperiod, followed by a decline and then a more extensive period of activity in the second half of the photoperiod. During peak signaling periods, most males had a distinct set of lateral abdominal phermone glands protruded for most of the time. However, the frequency of anal pheromone gland dipping varied considerably over time. Episodes of wing fanning (which may disperse pheromones) and abdomen dipping coincide during a male's tenure on a host leaf. Host-plant leaves were contained for 48 h with signaling males or immature females or kept without insects. Several, though not all, of the constituents of the pheromone were found on leaves within 1 h of removing signaling males. None of these compounds occurred on either type of control leaf. Mature virgin female flies were more likely to be found in contact with host leaves that had been previously exposed for 48 h to the activities of sexually mature males than with unexposed control leaves. There was no difference in the reaction of mature virgin female flies to unexposed control leaves or leaves previously exposed to the activities of other sexually immature female or male flies for 48 h. Presumably, the deposition of pheromones by mature males accounts for the difference in reactions.