Extreme trophic segregation between sympatric fish species: the case of small sized body <Emphasis Type="Italic">Aphyocharax</Emphasis> in the Brazilian Pantanal

Interspecific differences in diet of the two sympatric fish species of the subfamily Aphyocharacinae were investigated. Both were sampled monthly (March 2000 to February 2001) during the rainy and dry season in North region of the Pantanal. Aphyocharax anisitsi was an invertivorous/insectivorous species, feeding mainly on aquatic insects during the rainy season and terrestrial insects in the dry season. Aphyocharax dentatus remained a piscivorous regardless of the hydrological season. Low feeding-overlap values, 0.079 in the dry season and no overlap in the rainy season were observed. The diet-breadth values for each species were low (less than 0.1) except for A. anisitsi in the lake during the dry season (0.4). A detrended correspondence analysis (DCA) summarized the diet similarity patterns: in DCA 1, it was observed that fish prey grouped A. dentatus in the lower scores, and insect prey grouped A. anisitsi in the higher scores. A two-way ANOVA showed that the diets differed significantly between the species. Our results show a clear trophic segregation between these species, supporting the niche concept that presumes that differences between sympatric species must exist, to allow their coexistence. Besides extreme segregation, it was clear that A. dentatus is a piscivorous fish, despite its low size (until 72 mm). This finding counteracts the current view about food web structure that poses a direct and positive relationship between body size and trophic position.     

Seasonality affects the parasitism levels in two fish species in the eastern Amazon region

Fish parasite communities have strong interactions with the environment, the host fish, and the aquatic invertebrate communities. Thus, factors directly involving their different life cycles, such as different host populations and environments, as well as seasonal fluctuations in water levels can cause different responses. The main factors structuring parasite communities may be the hydrodynamic variations, together with seasonal variations in the availability of infectious stages of parasites in the environment. The purpose of this study was therefore to investigate the influence of the rainy and dry seasons on parasite infracommunities in fish species in the Amazon River System of Brazil. Between October 2009 and April 2011, specimens of Colossoma macropomum and Colossoma macropomum × Piaractus brachypomus hybrids (tambatinga) were examined for the presence of parasites. The parasite communities were similar in these two species that both showed aggregate dispersion, although the hybrid specimens were less parasitized. For both hosts, the Brillouin diversity, species richness, evenness and Berger‐Parker dominance indices were similar in the rainy season and dry season, except that the Berger‐Parker dominance index for the C. macropomum × P. brachypomus hybrid was higher during the dry season. Ichthyophthirius multifiliis was the dominant parasite, followed by Piscinoodinium pillulare, in both hosts. However, C. macropomum had a higher prevalence and abundance in the dry season, while in the C. macropomum × P. brachypomus hybrid, only the I. multifiliis prevalence increased. The abundance of monogenean species (Anacanthorus spathulatus, Linguadactyloides brinkmanni, Mymarothecium and Notozothecium janauachensis) was higher during the dry season in the gills of C. macropomum. Despite overdispersion of the lernaeid Perulernaea gamitanae, a seasonal pattern was seen only in the C. macropomum × P. brachypomus hybrid, with higher prevalence in the rainy season. The low prevalence and abundance of the ectoparasites Tetrahymena sp., Trichodina sp. and Braga patagonica, as well as of the endoparasites Procamallalus (Spirocamallanus) inopinatus and Neoechinorhynchus buttnerae, were not affected by seasonality. This information is applicable in farming practice for these economically important fish, as it indicates the best time for prophylactic management and treatment against parasites, in order to prevent economic losses in fish farms.     

Influence of season on leaf litter ant (Hymenoptera: Formicidae) diversity in the locality of Minko'o (Southern,Cameroon)

Seasonality is known to influence ant activity in many tropical rain forests in the world such as South America and Africa. We surveyed ant fauna in the leaf litter in the locality of Minko'o. The work aimed to evaluate the effect of seasonal variation on the diversity and composition of litter ants. Ants were sampled from November 2015 to June 2017, using four sampling methods: visual capture, bait, pitfall trap and extraction. Species richness, Shannon diversity index and analysis of similarities were used to characterise diversity of ant communities between seasons. We collected 306 ant species, shared out between 56 genera and 11 subfamilies. Subfamilies Myrmicinae, Ponerinae, Dolichoderinae, Formicinae, Dorylinae, Cerapachyinae and Pseudomyrmecinae occurred in all the seasons. Species richness was highest in major dry season with 243 species followed by minor rainy season with 188, major rainy season with 177 species and finally minor dry season that recorded the lowest with 155 species. Kruskal–Wallis test showed that ant species richness did not differ between seasons (p > 0.05). Species diversity index indicated that diversity was the highest during minor dry season (H′ = 4.24), followed by the major dry season (H′ = 4.23), minor rainy season (H′ = 4.21) and lowest during major rainy season (H′ = 4.06). Eight most frequents ants have been recorded: Axinidris sp.1, Camponotus flavomarginatus, Monomorium guineense, Myrmicaria opaciventris, Odontomachus troglodytes, Carebara perpusilla, Paltothyreus tarsatus and Pheidole megacephala. Assessment of the seasonal effect on diversity reveals that dry season is richer and more diverse than rainy season and the season significantly influence the diversity of litter ants.     

Flaxseed oil modulates testicular biometrics,hormone, libido,antioxidant and semen profiles in endangered Teressa goat of Andaman and Nicobar Islands

Teressa goat is a unique goat breed in Andaman and Nicobar Islands (ANI) of India. Effects of Flaxseed oil (FSO) supplementation in body weight (BW), scrotal circumference (SC), testicular volume (TV) and testicular weight (TW), endocrinological profiles, sex behavioural profiles (SBPs), oxidative stress markers and semen production and its quality profiles in rainy and dry summer season were studied in Teressa goat. Male goats (n = 12) of 3–4 years old were equally divided into control and treated groups. Treated animals received 25 mL FSO per day. Oral drenching of FSO was done in the morning before feeding the concentrate ration. Body weight, scrotal circumference, TV and TW were measured in bucks of FSO treated and untreated during rainy and dry summer seasons. Blood follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone, thyroid stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), cortisol and prolactin, total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and malondialdehyde (MDA) were measured in bucks of FSO treated and untreated during rainy and dry summer seasons. Libido score (LS), mating ability score (MAS) and sex behavioural score (SBS) were estimated at time of semen collection in bucks of FSO treated and untreated during rainy and dry summer seasons. Semen samples (n = 100; 50 semen samples from each season; each 25 semen samples from control and treatment groups per season) were collected and analysed for semen quality profiles. One-way ANOVA (control rainy, control dry, treated rainy and treated dry) revealed that BW, SC, TV and TW, FSH, LH, testosterone, TSH, T3 and T4 were higher (P < 0.05) and cortisol and prolactin were lower (P < 0.05) in FSO treated bucks of rainy season followed by untreated bucks of rainy season, FSO treated bucks of dry summer season and were lower (P < 0.05) in untreated bucks of dry summer season. Similarly, TAC, CAT, SOD and GSH, LS, MAS and SBS, and volume, pH, sperm concentration, mass activity, total motility (TM), viability, acrosomal integrity (AcI), plasma membrane integrity (PMI) and nuclear integrity (NI) were higher (P < 0.05) and MDA and TSA were lower (P < 0.05) in FSO treated bucks of rainy season followed by FSO treated bucks of dry summer season, untreated bucks of rainy season and were lower (P < 0.05) in untreated bucks of dry summer season. The results of the present study indicated that the breeding bucks suffered physiological stress (higher cortisol), oxidative stress (higher MDA and deficiency of antioxidants), hormonal imbalance (higher prolactin and cortisol and deficiency of gonadotropins, gonadal hormone and thyroid hormones) and infertility due to poor libido and poor semen production and its quality profiles during dry summer season. Thus, dry summer was more stressful season compared to rainy season for the goat bucks. FSO supplementation mitigated these stresses and improved the scrotal and testicular biometrics, libido, antioxidants, hormones and semen quality profiles in Teressa goat bucks. The current study concluded that FSO effectively improved the hormones, libido, antioxidant profiles, and scrotal and testicular biometrics with cascading beneficial effects on semen quality profiles in Teressa goat bucks under humid tropical island ecosystem of Andaman and Nicobar Islands.     

Ecophysiological and species‐specific responses to seasonal variations in halophytic species of the chenopodiaceae in a Mediterranean salt marsh

Plants adopt different strategies in response to seasonal variations in their natural biotype. In this study, the responses of seasonal changes on the organic osmolyte contents, ionic homoeostasis, osmotic potential and succulence of native chenopods in a salt marsh of Egypt were studied. Five halophytic species of the chenopodiaceae were collected during the rainy and dry season: Atriplex halimus L., Halocnemum strobilaceum (Pall.), Salicornia fruticosa (L.), Suaeda pruinosa (Lange) and Arthrocnemum macrostachyum (Moric). Results showed that plants employ an osmoconformer strategy via species specificity of response to seasonal variations. The total ions accumulation in all species was higher during the rainy season compared with the dry season. In particular, during rainy season, A. halimus resulted the higher accumulator species, followed by H. strobilaceum. Conversely, S. fruticosa, S. pruinosa and A. macrostachyum were defined as low‐accumulator species. In each studied species, the effective salinity, biological absorption coefficient as well as leaf succulence were higher during the rainy season. In conclusion, the present study have pointed out the importance that should be accorded with the development of research directed towards agronomic aspects for the uses of halophytic chenopodiaceae in salt marsh. Further, data obtained indicate that the ions accumulator species should be considered for use in phytoremediation of degraded saline lands.     

Seasonal and size-related changes in the food of the short-finned eel,Anguilla australis in Lake Ellesmere,Canterbury, New Zealand

Synopsis An approximately monthly sampling programme in Lake Ellesmere, Canterbury, New Zealand, from January 1974 to April 1976 yielded 487 eels. The stomachs were fixed in 10% neutralised formalin and the contents examined. Preliminary analysis indicated that the mollusc Potamopyrgus antipodarum, the isopod Austridotea annectens, the mysid Tenagomysis chiltoni, the amphipod Paracalliope fluviatilis, the midge larva Chironomus zealandicus and the teleosts Retropinna retropinna, Galaxias maculatus and Gobiomorphus cotidianus together made up the bulk of the diet. The pre-ingested dry weight (i.e. the reconstructed weight) of the most important of these prey species was obtained by relating the length of a digestion resistant part to actual dry weight in field collected specimens. Regression equations for this relationship in each season enabled the reconstructed dry weight of each stomach item to be calculated. In some instances reconstructed weight was less than the actual digested dry weight of the prey specimen. In every case the larger value was used. This method is referred to as Combination Dry Weight (CDW) and is believed to be new. These data, used in conjunction with the energy content of the species concerned, enabled the caloric dietary contribution of each prey species to be determined. Comparison of relative contribution to eel diet between CDW and energy values calculated from CDW and bomb calorimetry revealed large differences. Marked variations in diet between ⩽40 cm, 40.1–50 cm, and>50.1 cm size classes were also shown. Eels ≤40 cm feed primarily on invertebrates and become progressively more piscivorous as they grow. Eels >50.1 cm are almost entirely piscivorous. Seasonal differences in diet also exist within each size class examined.     

Chimpanzee predation in the Mahale mountains from August 1979 to May 1982

Fifty-four episodes of predatory behavior of wild chimpanzees were recorded in Mahale, western Tanzania, from August 1979 to May 1982. The chimpanzees most frequently hunt in two seasons, during May, and from August to December. Longer-term fecal analysis indicates that predation frequency is significantly higher in the dry than in the rainy season. The seasonality of predation might be the result of the sum of various ecological factors, at least one of which is the birth season of the prey species. Most of the prey are juvenile blue duiker, bushbuck, bushpig, red colobus, and red-tailed monkeys. Sex difference is recognized in the prey selection and in the hunting method employed. Apparent local difference in the predatory behavior between Mahale and Combe chimpanzees (in Mahale,females hunt more frequently, and blue duiker is the most frequent prey) can be understood in terms of the difference either in the observation methods or in the faunal diversity and density. Other aspects of predatory behavior also are reported.     

Ecology of the growth of Anolis nebulosus (Squamata: Dactyloidae) in a seasonal tropical environment in the Chamela region,Jalisco, Mexico

Juvenile growth rates are thought to be restricted by available food resources. In animals that grow throughout the year, such as tropical lizards, growth is therefore predicted to be faster during the rainy season. We test this prediction using a population of Anolis nebulosusby describing the growth trajectories of both sexes using nonlinear regression models, and we then correlate the growth rates of individuals with food available in the environment, precipitation, and temperature. The Von Bertalanffy model fits the growth rates of the females better, while the logistic‐by‐length model fits the males better. According to both models, the males grew faster than females, reaching slightly smaller sizes at adulthood. Males reached sexual maturity when 35 mm long, at an age of seven months, and females matured at 37 mm (SVL), taking nine months to reach this size. In 1989, juvenile males and females grew more in both seasons (rainy and dry) than adults; for 1990, there were no differences by season or between age classes. These results are interesting since in the 1989 and 1990 rainy seasons, practically the same orders of prey and the greatest abundance of prey available in the environment were registered. A possible explanation could be that predation was more intense in 1990 than in 1989. There is little evidence that food, temperature, and humidity affect growth rates of A. nebulosus, refuting our predictions. This is mainly due to the low variation in growth observed in 1990. Therefore we think that the growth of this species reflects a complex combination of ecological and genetic factors.     

Diversity of parasites in Cichlasoma amazonarum Kullander, 1983 during rainy and dry seasons in eastern Amazon (Brazil)

This study investigated the influence of the rainy and dry seasons on the parasite communities of Cichlasoma amazonarum (Kullander, 1983) in a tributary of the Amazon River system, northern Brazil. Of 112 fish examined, 95.5% were parasitized by Ichthyophthirius multifiliis, Piscinoodinium pillulare, Gussevia disparoides, Posthodiplostomum sp., Procamallanus (Spirocamallanus) inopinatus, and Echinorhynchus paranensis, as well as by the Glossiphoniidae leech. Ichthyophthirius multifiliis and P. pillulare were the dominant parasite species, with I. multifiliis the most prevalent and abundant; the leech (Glossiphoniidae) was the least prevalent and least abundant. Parasites presented an aggregate dispersion pattern and seasonal variations in infestation levels, influenced by the environmental conditions in the rainy season. Variation in the parasite dynamics created overall changes in the parasite communities, characterized by greater diversity, species richness and evenness during the rainy season. However, there was a high similarity (99.8%) in the parasite community structure between the rainy and dry seasons. During the dry season the hosts had predominantly 1–3 parasite species compared to 3–4 parasites in the rainy season. Some parasites in the eastern Amazon undergo population changes relating to seasonality. These results thus indicate the correct season to apply adequate prophylactic measures to reduce negative impacts of parasites in this wild ornamental fish when captured.     

Host‐plant associated genetic divergence of two Diatraea spp. (Lepidoptera: Crambidae) stemborers on novel crop plants

Diatraea lineolata and Diatraea saccharalis (Lepidoptera: Crambidae) are moths with stemboring larvae that feed and develop on economically important grasses. This study investigated whether these moths have diverged from a native host plant, corn, onto introduced crop plants including sorghum, sugarcane, and rice. Diatraea larvae were collected from these four host plants throughout the year in El Salvador and were reared on artificial diet until moths or parasitoids emerged. Adult moths were subsequently identified to species. Amplified fragment length polymorphisms (AFLPs) and mitochondrial DNA cytochrome oxidase I (COI) were used to examine whether or not there was genetic divergence of D. lineolata or D. saccharalis populations on the four host plants. Percent parasitism was also determined for each moth on its host plants. D. lineolata was collected from corn in the rainy season and sorghum in the dry season. D. saccharalis was most abundant on sugarcane in the rainy season and sorghum in the dry season. The AFLP analysis found two genetically divergent populations of both D. lineolata and D. saccharalis. Both moths had high levels of parasitism on their dominant host plant in the rainy season, yet had low levels of parasitism on sorghum in the dry season. The presence of two genotypes of both Diatraea spp. on sorghum suggest that host‐associated differentiation is occurring on this novel introduced crop plant.     

Seasonal diet composition of Fundulus lima (Cyprinodontiformes: Fundulidae) in two oasis systems of Baja California Sur, Mexico

Fundulus lima inhabits river drainage systems and is threatened after the introduction of cichlids in the area. To support conservation programs, the spatial and temporal variation of the diet composition of this endangered killifish, was determined in two oasis systems of Baja California Sur, Mexico (San Ignacio and La Purisima river drainages), during rainy and dry seasons. F. lima was captured by using passive and active capture techniques. A total of 192 stomach contents of F. lima was analyzed. The contribution of each prey item in the diet composition was quantified by means of the indices of occurrence frequency (% OF), numerical (% N) and volume (% V) percentages. The relative importance of each prey item was determined according to the percentage of the Relative Importance Index (% RII). The similarity of the diet was calculated between hydrological basins (populations combined by basin), seasons (rainy versus dry months), sexes and size classes, by using Schoener's resource overlap index. We used two ecological indices to determine the type of feeding strategy exhibited by the fish: (1) niche breadth of Levins and (2) proportional similarity of Feisinger. Sand was the most abundant item in the stomach content of killifishes from both drainages (39% and 47%, respectively). Diet composition was similar for both drainages (74%) as well as among their respective size classes; however, it was different between sexes. In both drainages, F. lima predated mainly on diatom algae, dipterous and trichopteran larvae, and fish scales during the dry season; while it preferred dipterous larvae, filamentous algae and ostracods in the rainy season. A feeding strategy of opportunist type was exhibited by F. lima during the rainy season, changing to specialist type during the dry season. This information will be the basis for future investigations related to the conservation of this endangered species and its habitat.     

Food habits of the otter (Lutra lutra) in two habitats of the Doñana National Park, SW Spain

Food habits of otters Lutra lutra were studied in two localities of the Doñana National Park (SW Spain) 16 km apart. These were the lowest stretch of Arroyo Rocina, a eutrophic stream where American red-swamp-crayfish were introduced in 1976, and at Lucio Bolín, an artificial pond 150 m in diameter, situated on the border of the Guadalquivir marshes. In all, 598 spraints were analysed between 1979 and 1984. Crayfish, occurring in 80% of the spraints, was the dominant food item in Arroyo Rocina, where other common foods were fish (63%), insects (55%) and amphibians (18%). Fish, occurring in 94% of the spraints, were by far the most abundant food item in Lucio Bolin, followed by insects (32%) and amphibians (28%). Seasonal differences in diet were small but interesting: reptiles were eaten more often in the dry season (April-September) and insects and crayfish in the rainy season (October-March). Among fish, eels were more commonly eaten in the rainy period and the remaining species in the dry period. This pattern of seasonal variation is opposite to the usual in temperate Europe. Mean size of the captured eels was statistically higher in Lucio Bolin than in Arroyo Rocina. A large amount of very small fish such as Gambusia was eaten. A comparison of prey consumed with estimates of prey abundance reveals a strong preference for eels. The diet of Mediterranean European otters seems to be more diverse than that of northern European ones, including more insects, amphibians and reptiles.     

Variation of diet and food consumption of the scaldfish Arnoglossus laterna(Walbaum, 1792)

Although Arnoglossus laterna (Walbaum, 1792) is a common benthic fish in Portugal, several aspects of its feeding ecology remain incomplete. In this study, diet was examined and the food consumption estimated on inshore waters in the central coast of Portugal. The diet of the scaldfish included mainly mysids, amphipods and polychaetes, while the decapod Philocheras bispinosus Hailstone was the most frequent prey. Variation in the diet according to fish size (two size‐classes), sex and spawning/non‐spawning seasons was examined. Significant differences in diet composition were found between seasons, whereby the most frequently consumed prey in the non‐spawning season were crustaceans, while polychaetes and nemerteneans comprised most of its diet in the spawning season. The average value of the vacuity index was very similar between seasons (24.7% non‐spawning season and 25.0% spawning season). Diet overlap between size‐classes and sexes was high, but low between the two seasons. Food consumption of A. laterna was estimated based on diet characterization and evacuation rate. The estimate of the daily food consumption was 1.15 mg dry weight for the non‐spawning season and 1.67 mg dry weight for the spawning season. Significant differences in consumption rates were found between size‐classes and sexes. Larger individuals showed a higher consumption rate than smaller individuals. Females consumed more food than males in the non‐spawning season, while in the spawning season males consumed more than females.     

Dietary overlap and seasonality in three species of mormoopid bats from a tropical dry forest

Competing hypotheses explaining species’ use of resources have been advanced. Resource limitations in habitat and/or food are factors that affect assemblages of species. These limitations could drive the evolution of morphological and/or behavioural specialization, permitting the coexistence of closely related species through resource partitioning and niche differentiation. Alternatively, when resources are unlimited, fluctuations in resources availability will cause concomitant shifts in resource use regardless of species identity. Here, we used next‐generation sequencing to test these hypotheses and characterize the diversity, overlap and seasonal variation in the diet of three species of insectivorous bats of the genus Pteronotus. We identified 465 prey (MOTUs) in the guano of 192 individuals. Lepidoptera and Diptera represented the most consumed insect orders. Diet of bats exhibited a moderate level of overlap, with the highest value between Pteronotus parnellii and Pteronotus personatus in the wet season. We found higher dietary overlap between species during the same seasons than within any single species across seasons. This suggests that diets of the three species are driven more by prey availability than by any particular predator‐specific characteristic. P. davyi and P. personatus increased their dietary breadth during the dry season, whereas P. parnellii diet was broader and had the highest effective number of prey species in all seasons. This supports the existence of dietary flexibility in generalist bats and dietary niche overlapping among groups of closely related species in highly seasonal ecosystems. Moreover, the abundance and availability of insect prey may drive the diet of insectivores.     

Feeding habits and trophic morphology of inshore lizardfish (Synodus foetens) on the central continental shelf off Veracruz, Gulf of Mexico

The inshore lizardfish, Synodus foetens, is one of the most common coastal demersal predators on the continental shelf of the Gulf of Mexico (GOM), but the biology and feeding ecology of this species is virtually unknown. Between November 2001 and January 2003 (10 collections), 603 individuals of S. foetens ranging from 112 to 420 mm standard length (SL) and 13 to 630 g (wet weight) were collected from the continental shelf of Alvarado, Veracruz, Mexico. About 60% of the individuals had empty stomachs with the stomach fullness of the remaining individuals being distributed as follows: 5% full (24.8%), 50–75% full (13.5%), and completely full (1.7%). The mean (± SD) wet weight of stomach contents was 12.1 ± 10.8 g during the rainy season, and 19.0 ± 13.0 g during the nortes season. Seventeen prey items were identified, with the majority thereof being fish. The most important prey items were Upeneus parvus, Loligo pealei, Engyophrys senta, Trachurus lathami, and Anchoa hepsetus. Seasonal changes in the diet were observed, with U. parvus and L. pealei being the most important prey during the nortes season, whereas E. senta and L. pealei were the main items during the rainy season. Prey size selection was evident among size classes of S. foetens, although no trophic overlap was observed among size classes (C_ik ≤ 0.004). High trophic level values were determined for all size classes by season (rainy season = 4.67, nortes season = 4.84), and indicated this species belongs to the piscivorous trophic guild that preys upon both demersal and pelagic species.     

Feeding habits of the Pacific bearded brotula Brotula clarkae Hubbs, 1944 (Ophidiidae) along the Pacific coast of Costa Rica,Central America

The present study analyzed the diet composition, ontogenetic shifts and dietary overlap of Brotula clarkae in relation to stage of maturity and sex. Samples were collected from the trawling fishery along the Pacific coast of Costa Rica (2011–2012) at depths ranging from 41.4 to 168.3 m; however, over 80% of the sampled fish were obtained at depths between 50 and 75 m. Size ranged from 14.4 to 98.4 cm total length. Of the 323 analyzed stomachs, 44.3% were from males, 86% were from immature individuals, and 49.8% had at least one prey item. According to the prey‐specific index of relative importance (P_SIRI), decapod shrimps were the most important prey (57.6% P_SIRIi) followed by teleosts (28.2% P_SIRIi), stomatopods (10.8% P_SIRIi), and crabs (3.3% P_SIRIi). Male and female B. clarkae exhibited a high dietary overlap (C_H = 0.94). Immature B. clarkae consumed primarily shrimps and crabs (71.5% of stomachs from immature specimens contained shrimps, which accounted for over 66.0% P_SIRIi); mature individuals consumed a large proportion of teleosts and stomatopods, which together contributed to over 91.0% P_SIRIi. Both immature and mature B. clarkae overlapped spatially with the commercial trawling fishery grounds along the Pacific coast of Costa Rica. However, juveniles feed predominantly on shrimps, suggesting that immature B. clarkae may be subjected to high fishing pressure as by‐catch, making them particularly vulnerable to overexploitation.     

Environmental influences on the replenishment of lizardfish (family Synodontidae) in Caribbean Panama

Lizardfish (family Synodontidae) are little studied despite their potentially important predatory role in epibenthic coral reef communities. The present study documented the temporal and spatial larval supply patterns of five Caribbean lizardfish species together with environmental variables (solar radiation, rainfall, water temperature, onshore-offshore winds, alongshore winds and wind-induced turbulence) to examine: (1) whether species within the same family respond differently to their developmental environment and (2) if larval supply in year-round warm waters is influenced by climatic changes. To address these questions, late-stage larvae of Synodus foetens, Synodus intermedius, Synodus poeyi, Saurida suspicio and Saurida brasiliensis were collected in replicate light traps in three different reef habitats (back-reef, lagoon and exposed) in the San Blas Archipelago, Panama, over 18 consecutive lunar months. Although replenishment of lizardfish occurred year-round, the temporal and spatial supply patterns were species-specific: S. foetens, S. intermedius and S. poeyi were most abundant during the dry season while S. suspicio and S. brasiliensis were most prevalent during the wet season. When seasons were analysed separately, water temperature explained 39 and 26% of the variance in light trap catches of S. foetens and S. intermedius, respectively, in the dry season while wind-induced turbulence accounted for 25% of the variability in S. suspicio and S. brasiliensis catches during the wet season. These findings stress the importance of analysing larval supply in conjunction with environmental data at a high taxonomic resolution to better understand the mechanisms that drive replenishment in reef systems at low latitudes.     

Feeding habits of Schizothorax oconnori Lloyd, 1908 in the Yarlung Zangbo River,Tibet

Seasonal, ontogenetic and sexual feeding habits of Schizothorax oconnori in the Yarlung Zangbo River were studied using percentages by number, weight and index of relative importance (IRI). The Schoener overlap index was applied to compare diets related to season, fish size and sex. The feeding intensity exhibited seasonal trends, with a minimum food intake in summer. Overall, 103 prey taxa belonging to seven prey categories (diatoms, green algae, cyanophytes, other algae, small invertebrates, macroinvertebrates and remains) were identified in 136 guts. Highest feeding diversity and evenness were recorded in summer, while lowest values of both indices occurred in autumn. S. oconnori fed almost exclusively on periphyton. Diatoms were the most important prey in terms of number, weight and IRI, followed by macroinvertebrates; other prey were also occasionally ingested. S. oconnori is a generalized and opportunistic feeder relying upon a wide trophic spectrum, but mainly feeds on diatoms as they are the most prevalent periphyton. There were high diet overlaps among seasons, fish sizes and between sexes. S. oconnori showed no dietary preference for any of the other prey available in the periphyton community.     

Histology,ultrastructure, and seasonal variations in the bulbourethral gland of the African straw-colored fruit bat Eidolon helvum

We studied the morphological characteristics and seasonal changes of the bulbourethral gland of Eidolon helvum in a typical African tropical environment. Forty-eight bulbourethral glands were examined using gross anatomical, histological, histochemical, and ultrastructural techniques during the early rainy, late rainy, and peak dry seasons. The pear-shaped bilateral bulbourethral glands were located extra-abdominally in the inguinal region. Trabeculae from the capsule divided the parenchyma into numerous lobules of tubuloalveolar glandular acini. The mucosa was covered by a simple columnar epithelium consisting up of principal secretory cells, columnar dense cells and basal cells, which were progressively pronounced during the dry season. The principal cells contained eosinophilic granules, which were PAS positive while the dense cells did not show affinity for the stains. The mean gross weights, acini diameters, and epithelial heights were greater during the rainy season than the dry season. Ultrastructural evaluation showed that the cytoplasm of the principal cells contained well-developed Golgi complexes, rough endoplasmic reticulum, mitochondria, and secretory vesicles of varying electron densities and sizes. The secretory vesicles were numerous during the early rainy season, decreased during the late rainy season and were scanty during the peak dry season. The simple columnar epithelium observed during the rainy season was replaced by an undefined stratified epithelium during the dry season, and this was associated with cellular degenerations and regenerations. In conclusion, E. helvum has a typical mammalian bulbourethral gland, with a unique cell type, the dense cell whose functions are not well-understood. The gland exhibits cyclical seasonal variation in structure and secretory activity; being active during the early rainy season (breeding season), and showing the lowest activity during the dry season (non-breeding season). Glandular epithelial cell renewal occurs during the dry season in preparation for the next breeding season.