Convict cichlids benefit from close proximity to another species of cichlid fish

The coexistence of species with overlapping resource use is often thought to involve only negative fitness effects as a consequence of interspecific competition. Furthermore, the scarce empirical research on positive species interactions has predominantly focused on sessile organisms. Here, I experimentally assessed the effect of close proximity of a potential brood predator and competitor on reproductive success of a neotropical cichlid fish. I demonstrate that convict cichlid (Archocentrus nigrofasciatus) broods have a higher survival rate near territories of the Nicaragua cichlid (Hypsophrys nicaraguensis), and that escape from predation and nest takeovers is the most likely explanation for the decreased offspring mortality.     

Brood parasitism of an open-water spawning cichlid by the cuckoo catfish

The cuckoo catfish Synodontis multipunctatus and S. grandiops are endemic to Lake Tanganyika and the only known nonavian vertebrates that exhibit obligate interspecific brood parasitism. Seven maternal mouth-brooding cichlid fish species are reported to be natural hosts of the parasitic catfish and share a common reproductive behaviour that the catfish exploits: cichlid females spawn eggs on the bottom, allowing the catfish female to place her eggs near the cichlid eggs, and the cichlid females collect the catfish eggs by mouth together with their own eggs. However, so far it has not been reported that the cuckoo catfish exploit different spawning behaviours. The genus Cyprichromis consists of five maternal mouth-brooding species endemic to Lake Tanganyika, most of which spawn and collect eggs in open water. This study reports that the cuckoo catfish also parasitizes the open-water spawning Cyprichromis coloratus, although it may not be a regular host.     

Testes Investment along a Vertical Depth Gradient in an Herbivorous Fish

Males are expected to adjust testes investment according to the varying level of sperm competition that they experience. Spatial and temporal variation in population density likely influences sperm competition. In herbivorous aquatic organisms, densities often decrease along a vertical depth gradient, because their food is photosynthetic and thus becomes less abundant in deeper regions where less light penetrates. This decrease should be dramatic on a steep slope, which allows testing of the association between density and testes investment at the within‐population level. We tested the effect in the socially monogamous herbivorous cichlid fish Variabilichromis moorii living on a steep slope in Lake Tanganyika. We examined competitor density and food abundance as ecological factors, territory defense behaviors and phenotypic traits (testes investment and somatic investment), and compared them between shallow (4–6 m depth) and deep habitats (10–13 m depth) separated by several dozen meters. We found that food availability drastically decreased with increasing depth and that V . moorii was much more abundant in shallower habitats. Males in shallower habitats were in better physical condition (based on fat and liver mass) despite experiencing greater costs in terms of territory defense. Testes investment differed in areas with different competitor density and food abundance along a vertical depth gradient, but competitor density was the most explanatory factor of the difference. This suggests that this herbivorous fish would change testes investment in response to population density.     

Species co‐occurrence patterns and dietary resource competition in primates

Diamond (Assembly of species communities. In: Cody ML, Diamond JM, editors. Ecology and evolution of communities. Cambridge: Belknap. p 342–444 ( 1975 )) argued that interspecific competition between species occupying similar niches results in a nonrandom pattern of species distributions. In particular, some species pairs may never be found in the same community due to competitive exclusion. Rigorous analytical methods have been developed to investigate the possible role that interspecific competition has on the evolution of communities. Many studies that have implemented these methods have shown support for Diamond's assembly rules, yet there are numerous exceptions. We build on this previous research by examining the co‐occurrence patterns of primate species in 109 communities from across the world. We used EcoSim to calculate a checkerboard (C) score for each region. The C score provides a measure of the proportion of species pairs that do not co‐occur in a set of communities. High C scores indicate that species are nonrandomly distributed throughout a region, and interspecific competition may be driving patterns of competitive exclusion. We conducted two sets of analyses. One included all primate species per region, and the second analysis assigned each species to one of four dietary guilds: frugivores, folivores, insectivores, and frugivore‐insectivores. Using all species per region, we found significantly high C scores in 9 of 10 regions examined. For frugivores, we found significantly high‐C scores in more than 50% of regions. In contrast, only 23% of regions exhibited significantly high‐C scores for folivores. Our results suggest that communities are nonrandomly structured and may be the result of greater levels of interspecific competition between frugivores compared to folivores. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

CLEANING BEHAVIOUR BETWEEN THE CICHLID FISH TILAPIA RENDALLI FENDALLI BOULENGER 1896 AND THE CYPRINID,LABEO CYLINDRICUS PETERS, 1852

SUMMARY

A case of interspecific cleaning behaviour is described between a cichlid host Tilapia rendalli rendalli and a Juvenile cyprinid Labeo cylindricus, in captivity. The host fish initiated the cleaning behaviour with a ‘head down’ display.     

Effect of Interspecific Competition and Herbivory on the Recruitment of an Invasive Alien Plant: Conyza sumatrensis

Most studies on the spread of a species have been carried out retrospectively. Conyza sumatrensis provides an exception; it has only been in Great Britain since 1984 and thereby provides the opportunity to follow an invasion from its early stages. Many different factors could lead to the exclusion of invading species from new habitats. Here we report results of a field experiment to determine the recruitment ability and population dynamics of C. sumatrensis within treatments of different levels of interspecific competition and herbivory over three years. Interspecific competition was manipulated using three cultivation treatments giving low, medium and high intensity competition. Factorial combinations of mollusc, insect and vertebrate (rabbit) herbivory were achieved using both chemical and physical exclusion techniques. We show that although C. sumatrensis recruitment occurs in areas where disturbance has caused low interspecific competition, maintenance of a population during secondary succession is unlikely. Effects of herbivory were dependent on the type of herbivory and the plant stage grazed. Rabbit grazing had strong negative effects on recruitment and survival of C. sumatrensis throughout the experiment. Insect herbivory, however, had no effect on any life stage. Mollusc herbivory showed a significant interaction with interspecific competitors, reducing recruitment only where competition was experimentally reduced. This revised version was published online in July 2006 with corrections to the Cover Date.     

The feeding habits of a group of herbivorous rock-dwelling cichlid fishes (Cichlidae: Perciformes) from Lake Malawi,Africa

Synopsis The feeding; habits of a group of tropical herbivorous rock-dwelling cichlid fishes from Lake Malawi, Africa, are investigated using stomach content analyses. The various species fed selectively on the periphyton of the rocky shores. Blue-green alga of the genus Calothrix was the most common item ingested by the group. Diatoms (Chrysophyta) also were abundant food items. Discriminant analysis showed that dietary items were good variables to identify species. Interspecific dietary differences showed a continuum from those species feeding primarily on Calothrix to those feeding primarily on diatoms. Algal resources exhibit distinct patterns of spatial variation. Diet was correlated with foraging behavior and trophic morphology. Interspecific differences in diet could possibly facilitate ecological coexistence among various species. Such coexistence would contribute to the maintenance of the high diversity fish faunas characteristic of the Great Rift Lakes of Africa.     

Optimizing canopy‐forming algae conservation and restoration with a new herbivorous fish deterrent device

The role of herbivorous fish in threatening marine forests of temperate seas has been generally overlooked. Only recently, the scientific community has highlighted that high fish herbivory can lead to regime shifts from canopy‐forming algae to less complex turf communities. Here, we present an innovative herbivorous fish deterrent device (DeFish), which can be used for conservation and restoration of marine forests. Compared to most traditional fish exclusion systems, such as cages, the DeFish system does not need regular cleaning and maintenance, making it more cost‐efficient. Resistance of DeFish was tested by installing prototypes at different depths in the French Riviera and in Montenegro: more than 60% of the devices endured several years without maintenance, even if most of them were slightly damaged in the exposed site in Montenegro. The efficacy of DeFish in limiting fish herbivory was tested by an exclusion experiment on Cystoseira amentacea in the French Riviera. In a few months, the number of fish bite marks on the seaweed was decreased, causing a consequent increase in algal length. The device here presented has been conceived for Mediterranean canopy‐forming algae, but the same concept can be applied to other species vulnerable to fish herbivory, such as kelps or seagrasses. In particular, the DeFish design could be improved using more robust and biodegradable materials. Innovative engineering systems, such as DeFish, are expected to become useful tools in the conservation and restoration of marine forests, to complement other practices including active reforestation, herbivore regulation, and regular monitoring of their status.     

Protected polymorphism in the two-locus haploid model with unpredictable fitnesses

 In an unpredictable environment, the distributions of alleles from which polymorphism can be maintained forever belong to a certain set, the C-viability kernel. Such a set is calculated in the two-locus haploid model, as well as the corresponding fitnesses at any time which make this maintenance possible. The dependence of the C-viability kernel on the set U of admissible fitnesses and on the recombination rate r is studied. Notably, the C-viability kernel varies rapidly in the neighborhood of equal fitness of AB and ab; it becomes empty when ab has a fitness below a certain function, which is delineated, of the recombination rate. The properties of the two-locus model under constraints, out of equilibrium and with unpredictable selection are thus presented. Received: 20 May 1999     

Prezygotic barriers to gene flow between <Emphasis Type="Italic">Taraxacum ceratophorum</Emphasis> and the invasive <Emphasis Type="Italic">Taraxacum officinale</Emphasis> (Asteraceae)

Prezygotic reproductive barriers limit interspecific gene flow between congeners. Here, I examine the strength of floral isolation and interspecific pollen-pistil barriers between an invasive apomictic, Taraxacum officinale, and the indigenous sexual alpine dandelion, Taraxacum ceratophorum. Experimental arrays of either native inflorescences or a mixture of native and exotic inflorescences were used to examine insect preference and to track movement of a pollen analog. Using hand-pollinations, conspecific and heterospecific pollen germination success on native stigmas was compared. To additionally test for interspecific pollen competition, T. ceratophorum plants received one of three possible hand-pollinations: control conspecific pollination, concomitant conspecific and heterospecific pollination (mixed), or conspecific pollen followed by heterospecific pollen 15 min later (staggered). Floral isolation was negligible as no insect preference was detected. On a presence/absence basis, florets on native inflorescences received slightly less pollen analog from heterospecific donors than from conspecific donors; however, the amount of dye particles transferred from either Taraxacum species to stigmas on recipient T. ceratophorum inflorescences was equivalent. In contrast to weak floral isolation, strong pollen germination and pollen competition barriers should reduce the potential for hybridization. Heterospecific T. officinale pollen exhibited reduced germination success on T. ceratophorum stigmas in comparison to conspecific pollen. Furthermore, a significant pollen-competition effect on the percentage of hybrid offspring was detected only when T. officinale preceded T. ceratophorum pollen by 15 min. This result indicates that conspecific pollen out-competes heterospecific pollen but further suggests that biotic and abiotic factors reducing pollen accrual rates may partially remove barriers to natural hybridization.     

Pale and dark dichromatism related to microhabitats in a herbivorous tanganyikan cichlid fish,Telmatochromis temporalis

Dichromatism and habitat utilization of a small herbivorous cichlid fish,Telmatochromis temporalis, were studied in a littoral rocky area of Lake Tanganyika. Individuals of both sexes had either pale or dark body coloration that did not change for long periods. Both sexes defended territories from consexuals, and a male had a harem of several females. Pale fish had territories in exposed areas and dark fish in shaded ones. Larger fish were dominant over smaller consexuals and occupied well-illuminated areas. When pale and dark fish were kept in areas with shaded and lighted backgrounds, respectively, they changed body colour within a few weeks. When pale fish were in well-illuminated areas and dark ones in shaded areas, they were cryptic. BecauseTelmatochromis temporalis are very vulnerable prey in coastal areas, dichromatism may function as antipredator camouflage.     

Cichlid-catfish mutualistic defense of young in Lake Malawi,Africa

Summary Bagrid catfish and cichlid parents engage in a mutualistic defense of their young from predators. Over 50% of the catfish broods observed contained cichlid young, primarily of three species: Crytocara pleurostigmoides, C. pictus and Rhamphocromis sp. Three catfish broods, monitored for over 50 days, had a survivorship rate 6 times greater during periods when cichlids were present than when cichlids were absent. During two and a half h of observations of catfish broods without cichlids, I observed 23 strikes by predators on catfish young. However, when cichlids were present no foraging attacks were observed upon the catfish, but 32 occurred against cichlids in two and a half hours of observations. When the catfish parents were experimently removed the cichlid young were consumed first then the catfish young. When cichlids were present the catfish young survived over 80% longer than those in broods without cichlids. It is concluded that the parental catfish increase the survival of their own young be allowing cichlids into the brood. Because of an asymmetry of costs between the two species, cichlid mothers are more likely to abandon these interspecific broods than are the catfish.     

Parental Investment and Division of Labor in the Midas Cichlid (Cichlasoma citrinellum)

The Midas cichlid (Cichlasoma citrinellum) is an aggressive, monogamous fish living in the Great Lakes of Nicaragua. Its breeding success rates are low due to intense competition for breeding sites and high levels of predation on the young. Male Midas cichlids devote a small portion of body weight to gonads and gametes compared with females. Males produce relatively small amounts of sperm perhaps because cichlid fertilization is very efficient and the male has a high certainty of paternity. While pair members invest equal amounts of time in parental care over the course of the breeding cycle, there is a clear division of labor. Males invest more in territorial protection than do females, whereas females provide more nurturance. Both parents are active over the course of the cycle but the male invests more intensely in the early stages of the cycle. About the time the eggs hatch, the burden of care shifts to the female and she continues to invest significantly more than the male over the remainder of the cycle. Females invest much more than do males when tissue investment and parental behavior are combined. Females also assume more of the burden of care as the brood matures. The male is not free to take advantage of this and leave his mate to initiate other broods because two parents are needed to defend the breeding site and brood. Monogamy with biparental care results.     

Resource control by territorial male cichlid fish in Lake Malawi

1. The rocky habitat communities of Lake Malawi contain a high diversity of ecologically similar, predominantly herbivorous, cichlid fish species. How so many species can coexist is still unknown.
2. Adult males of the majority of these species hold permanent territories which form dense multispecies mosaics across the shores.
3. The study examined six coexisting species of cichlids from the rocky habitat where males are known to control access to the algal food resources within their territorial space. These included four sibling species of the Pseudotropheus ( Tropheops ) species complex, which are specialized epilithic algal herbivores, and two sibling species of the trophically more generalist P . ( Maylandia ) species complex which feed upon both epilithic algae and plankton.
4. The hypotheses that both intraspecific and interspecific territoriality occur in these communities and that interspecific aggression initiated by territorial males is preferentially directed at species with the most similar diets to their own were tested.
5. It was found that males preferred to exclude conspecific intruders, while they tolerated intruders with different diets to their own. Also, male P . ( Tropheops ) preferentially excluded similar heterospecific dietary specialists, while male P. ( Maylandia ) tolerated similar heterospecific dietary generalists.
6. Based on this study, it is proposed that interspecific territoriality may be reducing competition between species with different diets and promoting their coexistence, while it may be enhancing competition between species with the same diet. Furthermore, it suggests that ecological generalism may be reducing the intensity of interspecific competition, while specializations for the same resources may be increasing competition.     

Reproductive strategy and interspecific competition in the Lake-living gobiid fish isaza,Chaenogobius isaza

Isaza,Chaenogobius isaza, is a small gobiid fish endemic to Lake Biwa. It lives offshore throughout almost the entire year, showing a remarkable diel vertical migration. In early spring, males and females migrate to lake shore to spawn under stones. Spawning season is limited to a very short span of time in early spring, late April to early May. During this short spawning season, the male is supposed to have only 2 brood cycles at maximum. At each brood cycle, the male is strictly monogynous, never accepting additional females. Males therefore show a marked mate choice, choosing a larger female regardless of the size of the male himself. Females also choose larger males. However, males are supposed to not waste time in male-male fighting in the natural spawning area. That this very short spawning season and its occurrence in early spring is primarily to avoid interspecific competition with another littorally reproducing goby Yoshinobori,Rhinogobius brunneus, is experimentally demonstrated.     

Duckling response to changes in the trophic web of acidified lakes

We reared American Black Duck (Anas rubripes Brewster) and Common Goldeneye (Bucephala clangula Linnaeus) ducklings on two Quebec laurentian lakes in which we manipulated brook trout populations (Salvelinus fontinalis Mitchill), lake acidity and lake productivity to relate waterfowl foraging to trophic status of lakes. We developed a preliminary model to assess the effects of lake acidity and productivity, fish predation and interspecific fish/duck competition in relation to available food (aquatic invertebrates). We then validated the model using a factorial analysis of the relationships between the variables pertaining to the diet of the fish and ducklings, and the environmental characteristics of the lakes (acidity, biological production and fish predation).The first factorial axis can be interpreted in terms of biological productivity, while the second axis illustrates the effect that fish have on the quantity and type of food available to ducklings. Two different trends appear to occur depending on whether the carrying capacity of the lake is reduced by acidification of the water or increase through liming or fertilization. In the first case, fish predation appears to have a marked effect on available food, whereas in the second case, interspecific fish/duck competition is apparently to blame for changes in the diet of ducklings. In both instances, but to a lesser extent, fish compete increasingly (exploitation and/or interference) with the ducklings, forcing them to feed to a greater extent in riparian sites that are less accessible to fish.     

Indispensable amino acid concentrations decrease in tissues of stomachless fish,common carp in response to free amino acid- or peptide-based diets

Summary. The premise that free amino acid or dipeptide based diets will resolve the nutritional inadequacy of formulated feeds for larval and juvenile fish and improve utilization of nitrogen in comparison to protein-based diets was tested in stomachless fish, common carp (Cyprinus carpio L.) larvae. We examined the postprandial whole body free amino acid (FAA) pool in fish that were offered a FAA mixture based diet for the duration of 2 or 4 weeks. We found that the total amount and all indispensable amino acids concentrations in the whole body decreased after a meal. We then fed juvenile carp with dietary amino acids provided in the FAA, dipeptide (PP), or protein (live feed organisms; brine shrimp Artemia salina nauplii, AS) forms. Histidine concentrations in the whole fish body increased in all dietary groups after feeding whereas all other indispensable amino acids decreased in FAA and PP groups in comparison to the AS group. Taurine appears to be the major osmotic pressure balancing free amino acid in larval freshwater fish which may indicate a conditional requirement. We present the first evidence in larval fish that in response to synthetic FAA and PP diets, the whole body indispensable free AA concentrations decreased after feeding. This study shows that amino acids given entirely as FAA or PP cannot sustain stomachless larval fish growth, and may result in depletion of body indispensable AA and most of dispensable AA. The understanding of these responses will determine necessary changes in diet formulations that prevent accelerated excretion of amino acids without protein synthesis.     

Mitochondrial DNA Phylogeny of the Family Cichlidae: Monophyly and Fast Molecular Evolution of the Neotropical Assemblage

A mitochondrial DNA (mtDNA) phylogeny of cichlid fish is presented for the most taxonomically inclusive data set compiled to date (64 taxa). 16S rDNA data establish with confidence relationships among major lineages of cichlids, with a general pattern congruent with previous morphological studies and less inclusive molecular phylogenies based on nuclear genes. Cichlids from Madagascar and India are the most basal groups of the family Cichlidae and sister to African–Neotropical cichlids. The cichlid phylogeny suggests drift-vicariance events, consistent with the fragmentation of Gondwana, to explain current biogeographic distributions. Important phylogenetic findings include the placement of the controversial genus Heterochromis basal among African cichlids, the South American genus Retroculus as the most basal taxon of the Neotropical cichlid assemblage, and the close relationship of the Neotropical genera Cichla with Astronotus rather than with the crenicichlines. Based on a large number of South American genera, the Neotropical cichlids are defined as a monophyletic assemblage and shown to harbor significantly higher levels of genetic variation than their African counterparts. Relative rate tests suggest that Neotropical cichlids have experienced accelerated rates of molecular evolution. But these high evolutionary rates were significantly higher among geophagine cichlids. Received: 18 September 1998 / Accepted: 16 December 1998     

Adjusting parental investment to changing environmental conditions: the effect of food ration on parental behaviour of the convict cichlid, Cichlasoma nigrofasciatum

Animals that care for their offspring may vary the amount of care provided for a particular brood in relation to environmental conditions. Food availablity is one factor that may affect the costs and benefits associated with parental investment. The convict cichlid, Cichlasoma nigrofasciatum, is a small, substrate-spawning cichlid from Central America. Both male and female provide parental care for eggs and fry. Paris were kept at one of three ration levels, high, medium or low. Time spent in parental fanning by females was positively related to ration. Males spent less time fanning than females and their parental behaviour varied considerably between individuals. Males on the high ration spent slightly more time fanning than those on the lower rations. The number of eggs produced per spawning and the post-spawning weight of both males and females were significantly and positively related to ration. Foraging frequency of both males and females was inversely related to ration. There was no significant effect of ration on the frequency of mouthing eggs and young or on intra-pair aggression. Eggs of low-ration fish hatched earlier than those of medium- and high-ration fish but there was no significant difference in the number of days that the young survived. These results suggest that the allocation of time and effort between parental and maintenance activities differs in relation to food supply. Parents may provide more care for the large brood produced when food is plentiful but place more emphasis on their own survival when food is short and broods are small.     

Dietary histories of herbivorous loricariid catfishes: evidence from δ<Superscript>13</Superscript>C values of otoliths

The ecology of many Neotropical fishes is difficult or often impossible to study during rainy seasons. Thus, ecological studies of tropical fishes are usually performed on fish captured only during dry seasons. Because otoliths preserve a record of life history, this study evaluated the utility of otolith stable isotope values for the investigation of trophic ecology of Neotropical fishes (specifically herbivorous loricariid catfish) throughout their lives. Because plant dietary materials have δ¹³C values that are determined by their photosynthetic pathways, metabolism and environmental conditions, different plants may impart different isotope values on fish otoliths that reflect consumption of these plants. The δ¹³C_(otolith) values of xylophagous Panaque nigrolineatus captured in the field were significantly lower than those of algivorous Hypostomus regani from a nearby region. A laboratory experiment wherein Hypostomus sp. had δ¹³C_(otolith) values that reflected the δ¹³C values of their plant diet and additional evidence indicate that δ¹³C_(otolith) values in loricariid catfish otoliths can record dietary history.