Foraging activity and behaviour of two goatfish species (Perciformes: Mullidae) at Fernando de Noronha Archipelago, tropical West Atlantic

The goatfishes (Mullidae) include about 50 bottom-foraging fish species. The foraging activity of the yellow goatfish, Mulloidichthys martinicus, and the spotted goatfish, Pseudupeneus maculatus, was studied comparatively at Fernando de Noronha Archipelago, off coast of Northeast Brazil tropical West Atlantic. Pseudupeneus maculatus fed over a larger variety of substrate types, had lower feeding rate, roamed more per given time, spent less time in a feeding event, and displayed a more diverse repertoire of feeding modes than M. martinicus. The differences in the foraging activity and behaviour between the two species possibly minimize a potential resource overlap, as already recorded for other sympatric mullids. Pseudupeneus maculatus had lower feeding rate most likely because it feeds on larger items, and roamed over greater distance per time. Possibly this is because it foraged over a greater variety of substrate distributed over a larger area than that used by M. martinicus. Notwithstanding the overall morphological and behavioural similarity of goatfishes in general, they do differ in their substrate preferences and foraging activity, which indicates that these fishes should not be simply considered generalized bottom foragers.     

A comparative study of cleaning activity of two reef fishes at Fernando de Noronha Archipelago,tropical West Atlantic

Cleaner fishes are usually classified as obligate or facultative cleaners according to their diet and the extent to which their nutritional requirements in the different ontogenetic stages are gained from cleaning. While obligate cleaners clean throughout their lives and ingest mainly food taken from the clients’ body surface, facultative cleaners clean only as juveniles and have a broader diet. In addition, some facultative cleaners may experience a relatively higher predation risk, and thus rarely interact with piscivorous fishes. Despite these acknowledged differences, there are very few studies that compare cleaning activity of obligate and facultative cleaners within the same area. Cleaning activity of the obligate cleaner goby Elacatinus cf. randalli and the facultative cleaner wrasse Thalassoma noronhanum were comparatively examined at Fernando de Noronha Archipelago, tropical West Atlantic. The client assemblage attended by the two cleaners differed, as the goby attended a slightly greater diversity of species (22), mostly piscivores and zoobenthivores, and the wrasse attended fewer species (19), mostly planktivores. Chromis multilineata was the most common client species of both cleaners, although body size (which is expected to be positively correlated to clients’ ectoparasite load) of C. multilineata individuals attended by the goby was larger than that of the individuals attended by the wrasse. Despite such differences, T. noronhanum showed a surprisingly species-rich client assemblage when compared with other cleaners of the genus Thalassoma. In addition, the frequency and time spent on cleaning interactions, as well as the number of client species attended per 10-min period, was similar for both cleaner species, which indicate that they have important yet complimentary ecological roles in the reef community at Fernando de Noronha Archipelago.     

Reef fish community structure of the Fernando de Noronha Archipelago (Equatorial Western Atlantic): the influence of exposure and benthic composition

We studied the reef fish assemblage of eight reefs within the oceanic archipelago of Fernando de Noronha, off northeastern Brazil. In a total of 91 belt transects (20 × 2 m) we recorded 60 species from 28 families. The 25 most abundant species accounted for about 98% of all fish recorded in this study and most of these species are widely distributed in the Western Atlantic. The majority of fish counted were planktivores (37.0%), followed by mobile invertebrate feeders (28.5%), territorial herbivores (11.3%), roving herbivores (10.5%), omnivores (7.1%), macrocarnivores (6.5%) and sessile invertebrate feeders (0.03%). In terms of biomass, roving herbivores were the most representative (41.8%), followed by mobile invertebrate feeders (19.9%), macrocarnivores (14.3%), omnivores (14.0%), piscivores (8.3%), planktivores (1.4%), territorial herbivores (0.3%), and sessile invertebrate feeders (0.03%). Overall, density and biomass of fishes were positively correlated with coral cover and depth, and negatively correlated with wave exposure. These relationships are probably a response to the habitat complexity provided by the higher coral cover in deeper reefs (>10 m) of the archipelago or to the lower water turbulence below 10 m deep. Carnivores and mobile invertebrate feeders were mainly influenced by depth and non-consolidated substratum, planktivores and omnivores by wave exposure and herbivores by algal cover. Although our results suggest that habitat characteristics may play a role in determining the distribution of some fish species, we also found several habitat generalists, suggesting that the community is dominated by versatile species.     

Assessing trophic interactions between pelagic predatory fish by gut content and stable isotopes analysis around Fernando de Noronha Archipelago (Brazil), Equatorial West Atlantic

The objective of this study was to analyse the feeding habits and trophic interactions between four oceanic predatory fish around the Fernando de Noronha Archipelago (FNA), Brazil, in the western equatorial Atlantic (3.86°S/32.42°W), internationally recognized as an environment of high economic and ecological value. For this purpose, biological samples of yellowfin tuna (Thunnus albacares), wahoo (Acanthocybium solandri), barracuda (Sphyraena barracuda) and dolphinfish (Coryphaena hippurus) were collected for stomach content and stable isotope analysis. Values of the index of relative importance revealed varied diets, with a strong presence of teleost fishes (Diodontidae and Exocoetidae) for all species, with yellowfin tuna having a greater diversity of food items. Despite being generalists/opportunists, the feeding strategy of these predators showed a tendency towards a specialized diet in the use of the available resources around the FNA. They presented a narrow trophic niche width (Levin's index, Bi < 0.6) and low overlap between species, except between barracuda and wahoo (MacArthur and Levin's, R₀ = 0.72). Isotopic compositions had broad values of δ¹³C and δ¹⁵N, and were significantly different between species. Our results provide information about the four species' trophic organization and suggest that the predators avoid competition by preying on different prey, thus allowing their coexistence.     

The Archipelago of Fernando de Noronha: An Intriguing Malformed Toad Hotspot in South America

Malformed anurans raise concern among scientists, because deformities may relate to the recent global crisis among amphibian populations, although declining populations also may be associated with other causes (e.g., diseases, over-exploitation, and land use/land cover change). We examined a sample of toads (Rhinella jimi, Bufonidae) from an introduced population in the Archipelago of Fernando de Noronha, Brazil where malformations of anurans were thought to be high. Our sample of 159 specimens from the site revealed that 44.6% of all specimens had one or more malformations. Incidence of malformed toads on the mainland sites was substantially lower: 10.5% at Itamaracá, and 3.7% at Propriá. We describe the malformations observed, including six undescribed types of malformation of anurans, and we pose possible hypotheses to explain this high incidence of malformed toads. In addition to existing hypotheses, we suggest for the first time the hypothesis that lack of predation pressures contributes to numbers of malformed toads. We indicate the need of specific studies to understand the causes of malformations in the R. jimi population of Fernando de Noronha, which is thought to be extreme foci of malformed amphibians in the world. Our results may improve local conservation action plans as this is an alien population that may be affecting endemic fauna, and may affect populations in other parts of the world, because toad species of the genus Rhinella are recognized as exceptional colonizers. More importantly, unknown variables in these toads’ environment are evidently affecting toads during development, which should be a concern for all species that inhabit the area, perhaps even humans.     

Karyological study of Amphisbaena ridleyi (Squamata, Amphisbaenidae), an endemic species of the Archipelago of Fernando de Noronha, Pernambuco, Brazil

The karyotype of Amphisbaena ridleyi, an endemic species of the archipelago of Fernando de Noronha, in State of Pernambuco, Brazil, is described after conventional staining, Ag-NOR impregnation and fluorescence in situ hybridization (FISH) with a telomeric probe. The diploid number is 46, with nine pairs of macrochromosomes (three metacentrics, four subtelocentrics and two acrocentrics) and 14 pairs of microchromosomes. The Ag-NOR is located in the telomeric region of the long arm of metacentric chromosome 2 and FISH revealed signals only in the telomeric region of all chromosomes. Further cytogenetic data on other amphisbaenians as well as a robust phylogenetic hypothesis of this clade is needed in order to understand the evolutionary changes on amphisbaenian karyotypes.     

Seroprevalence of Toxoplasma gondii in domestic and wild animals from the Fernando de Noronha, Brazil

Fernando de Noronha is an archipelago of 21 islands and islets in the Atlantic Ocean, state of Pernambuco, Brazil, which has a varied biodiversity including alien species or sinantropic animals. The objective here was to determine the seroprevalence of Toxoplasma gondii in domestic and wild animals from Fernando de Noronha archipelago, Brazil. Between July 2007 and May 2010, blood samples were collected from 764 animals (533 domestic and 231 wild animals). Sera were tested by the indirect fluorescence antibody test (IFAT) or the modified agglutination test (MAT), or by both. Antibodies to T. gondii were found in 80 (80.0%) of 100 chickens ( Gallus domesticus ), 3 (3.0%) of 100 cattle ( Bos taurus ), 59 (60.8%) of 97 sheep ( Ovis aries ), 9 (81.8%) of 11 goats ( Capra hircus ), 7 (43.7%) of 16 horses ( Equus caballus ), 70 (59.3%) of 118 cats ( Felis catus ), 36 (39.6%) of 91 dogs ( Canis familiaris ), 13 (38.2%) of 34 black rats ( Rattus rattus ), and 157 (79.7%) of 197 cattle egrets ( Bubulcus ibis ). Results indicate endemic infection by this zoonotic parasite among the animal and avian fauna in this archipelago from Brazil.     

Prey selection by two benthic fish species in a Mato Grosso stream, Rio de Janeiro, Brazil

Key to understand predator choice is the relationship between predator and prey abundance. There are few studies related to prey selection and availability. Such an approach is still current, because the ability to predict aspects of the diet in response to changes in prey availability is one of the major problems of trophic ecology. The general objective of this study was to evaluate prey selection by two species (Characidium cf. vidali and Pimelodella lateristriga) of the Mato Grosso stream, in Saquarema, Rio de Janeiro, Brazil. Benthos and fishes were collected in June, July and September of 2006 and January and February of 2007. Fish were collected with electric fishing techniques and benthos with a surber net. Densities of benthic organisms were expressed as the number of individuals per/m2. After sampling, the invertebrates were fixed in 90% ethanol, and, in the laboratory, were identified to the lowest taxonomical level. Approximately, seventy individuals from each species were selected randomly in each month. Fishes were fixed in 10% formalin in the field and transferred to 70 degrees GL ethanol in the laboratory. Fishes had their stomachs removed for subsequent analysis. Fish diet was described according to the numeric frequency method. The Manly Electivity Index was applied in order to verify prey selection. The most abundant families in both benthos and diet of both fish species were the same, indicating that these species consume mainly most abundant prey in the environment. We concluded that prey selection occurs even for preys that had small abundance in the environment. However, it is the availability of the macroinvertebrate resources that determines the major composition of items in diet of fish, demonstrating that the abundance is the factor that most influences the choice of prey.     

Apparently contradictory routes in the expansion of two fish species in the Eastern Atlantic

One specimen of the boreal Clupea harengus (Clupeidae) was caught southerly, in the Gulf of Cádiz (southern Spain), whereas a specimen of the subtropical Epinephelus aeneus (Serranidae) was caught northerly, in Galician waters (north-west of Spain). These catches represent a new southernmost record in the eastern Atlantic for C. harengus and the second northernmost for E. aeneus. The co-occurrence of warm and cold affinity fishes in temperate latitudes is unusual, but the existence of anomalies in the temperature of the Atlantic waters could be behind these findings.     

Significant range extensions for two fish species at Pitcairn Island,South Pacific

A baited videographic survey at Pitcairn Island has significantly extended the known range for two reef‐fish species: blue‐lined triggerfish Xanthichthys caeruleolineatus and greater amberjack Seriola dumerili, with an additional minor extension noted for giant trevally Caranx ignobilis. This highlights the importance of further research in this remote, poorly studied island group and provides evidence supplementing the understanding of oceanographic patterns in the South Pacific.     

Morphological and genetic description of Octopus insularis, a new cryptic species in the Octopus vulgaris complex (Cephalopoda: Octopodidae) from the tropical southwestern Atlantic

A medium-sized Octopus species is described based on materialcollected in shallow equatorial waters around the oceanic islandsof Fernando de Noronha Archipelago, Rocas Atoll, St Peter andSt Paul Archipelago and the mainland of northeastern Brazil.The new species, Octopus insularis, is described morphologically,and also characterized by the large mitochondrial subunit ribosomalRNA gene (mt 16S rDNA). The new species has relatively shortand stout arms, rugose reddish brown skin in preserved specimens,8 to 11 gill lamellae on the outer demibranchs, small ligula,characteristic symmetrical radula, spermatophore and beak, smalleggs and high fecundity (213,000 oocytes under 1.5 mm diameter).The habitats and skin patterns of living animals are brieflydescribed. The new species differs both morphologically andgenetically from Octopus vulgaris in the Mediterranean, Venezuelaand southern Brazil. (Received 10 November 2006; accepted 19 October 2007)     

Length–weight relationships of four freshwater fish species from two Atlantic coastal drainage areas in Brazil

Length–weight relationships (LWRs) were determined for four fish species from two drainage areas, those of the Itapemirim and Jucu River, in the state of Espírito Santo, southeastern Brazil. Fishes were collected between May 2015 and November 2016, with gill nets, casting net, dip net, and sieve. Herein are presented LWRs for Astyanax lacustris, Astyanax taeniatus, Hyphessobrycon bifasciatus and Oligosarcus acutirostris.     

横断山区两种菊科植物的核型研究

对横断山区两种菊科植物圆齿狗娃花和细叶亚菊进行了染色体数目报道和核型研究,其中圆齿狗娃花为首次报道,2n=18=2x=18m(2SAT);而细叶亚菊的为新的染色体数目,2n=72=8x=56m+16sm,与之前报道的36不同。研究结果发现菊科植物这两个属在横断山及其它地区同时存在二倍体与多倍体。     

Stress response of two coral species in the Kavaratti atoll of the Lakshadweep Archipelago, India

Frequent occurrences of coral bleaching and the ensuing damage to coral reefs have generated interest in documenting stress responses that precede bleaching. The objective of this study was to assess and compare physiological changes in healthy, semi-bleached and totally bleached colonies of two coral species, Porites lutea and Acropora formosa, during a natural bleaching event in the Lakshadweep Archipelago in the Arabian Sea to determine the traits that will be useful in the diagnosis of coral health. In April 2002, three “health conditions” were observed as “appearing healthy,” “semi-bleached” and “bleached” specimens for two dominant and co-occurring coral species in these islands. Changes in the pigment composition, zooxanthellae density (ZD), mitotic index (MI) of zooxanthellae, RNA/DNA ratios and protein profile in the two coral species showing different levels of bleaching in the field were compared to address the hypothesis of no difference in health condition between species and bleaching status. The loss in chlorophyll (chl) a, chl c and ZD in the transitional stage of semi-bleaching in the branched coral A. formosa was 80, 75 and 80%, respectively. The losses were much less in the massive coral P. lutea, being 20, 50 and 25%, respectively. The decrease in zooxanthellar density and chl a was accompanied by an increased MI of zooxanthellae and RNA/DNA ratios in both the species. There was an increase in accumulation of lipofuscin granules in partially bleached P. lutea tissue, which is an indication of cellular senescence. Multivariate statistical analyses showed that colonies of P. lutea ranked in different health conditions differed significantly in chl a, chl c, ZD, RNA/DNA ratios, and protein concentrations, whereas in A. formosa chl a, chl c, chl a/c, phaeopigments and MI contributed to the variance between health conditions.     

Top-down control of a meiobenthic community by two juvenile freshwater fish species

Top-down control of prey assemblages by fish predation has been clearly demonstrated for zooplankton and macroinvertebrates. However, in the benthic communities of freshwater ecosystems, the impact of fish predation on meiofaunal assemblages is nearly unknown. In this study, the predation effects of juvenile carp (Cyprinus carpio) and gudgeon (Gobio gobio) on meiofaunal abundance, biomass, community structure, and the diversity of nematodes were examined using microcosms that were sampled repeatedly over 64 days. Significant differences in abundance and biomass were found between the two fish treatments (carp and gudgeon) and their respective controls for nematodes, oligochaetes, and crustaceans (copepods, harpacticoids, ostracods, and cladocerans), but not for rotifers. These changes were consistent with top-down control of the freshwater meiofaunal assemblages in the microcosms over time. By contrast, small-bodied meiofauna was more abundant, suggesting indirect facilitation. Neither the species richness nor the diversity of the nematode community was affected by fish predation. The results indicate that predation by juvenile freshwater fish depresses the overall abundance and biomass of meiofaunal assemblages, except for rotifers, and alters the size structure of the meiofaunal community. Therefore, the meiofaunal assemblages of freshwater ecosystems may be influenced by bottom-feeding juvenile fish, e.g., carp and gudgeon, through top-down control of meiofaunal populations.     

Weight–length and length–length relationships for reef fish species from the Cape Verde Archipelago (tropical north‐eastern Atlantic)

This study reports weight–length and length–length relationships for selected coastal reef fish species of the Cape Verde Archipelago (tropical north‐eastern Atlantic). Specimens were caught with different types of gear (long‐lines, hand‐lines, purse‐seines and traps) during commercial fishing activities and sampled during fish market operations. A total of 8328 individuals were sampled, representing 29 species from 14 Families. This study provides the first references on weight–length and length–length relationships for five and 23 fish species worldwide, for 10 and 24 species for the Eastern Atlantic and for 12 and 26 species for Cape Verde Archipelago, respectively. Additionally, it provides revised weight–length relationships for 11 species from Cape Verde waters.     

Spatio-temporal microhabitat use by two co-occurring species of scorpions in Atlantic rainforest in Brazil

With the increasing devastation of the tropical rain forest, there is a critical need to understand how animal forest communities are structured and how habitat degradation will affect these communities. We conducted a field survey to investigate the microhabitat preferences of two co-occurring species of scorpions (Tityus pusillus and Ananteris mauryi) in a fragment of Atlantic rainforest, as well as their abundance and their ecological niche, during both the dry and rainy seasons. Behavioural aspects related to the use of the environment and the proportions of juveniles and adults are also described. The occurrence of intra- and interspecific coexistence was assessed by active search. In addition, pitfall catches were used to assess the structure of the population in the dry and rainy seasons. The differential patterns of spatial distribution in the litter layers provided evidence of partial niche partitioning between the two coexisting scorpion species depending on age and climatic conditions. Abundance, foraging behaviour and age structure (juveniles and adults) were seasonally influenced. We conclude that the diverse and subtle behaviours involved in interaction and habitat use may facilitate species coexistence. Resource partitioning and refuge sharing on a temporal and/or spatial scale, as well as predation pressure, may drive the dynamics and spatial distribution of scorpion species in the rain forest environment.     

B chromosomes in two fish species, genus Rhamdia (Siluriformes, Pimelodidae)

Specimens belonging to two fish species genus Rhamdia were cytogenetically analysed from seven localities in Brazil and Argentina. In addition to the 58 chromosomes of the basic karyotype, one to five metacentric B chromosomes were observed carrying conspicuous heterochromatic blocks on the distal regions of both chromosome arms. These B chromosomes are mitotically stable and, in the two best-sampled populations in R. hilarii (Lobo and 29 reservoirs), they showed frequency distributions fitting a binomial distribution, though Bs were more frequent in the latter. The presence of B chromosomes with the same appearance in R. quelen suggests an ancient origin for these B chromosomes, presumably prior to speciation from a common ancestor.