Morphology and reproduction of the cavefish Trichomycterus chaberti and the related epigean Trichomycterus cf. barbouri

Hypogean and epigean populations of Trichomycterus catfishes inhabit streams from different environments (cave, headwater, canyon and valley) in the Torotoro National Park in the Andes, Bolivia. A significant reduction in the diameter of the eyes and in the surface area of the mesencephalon was observed in subterranean populations, along with an increase in the surface area of the telencephalon. Contrary to expectations, the barbel did not appear to be longer in hypogean populations. The observed pattern of modification of the other variables (pigmentation, eye asymmetry, surface area of the cerebellum and rhombencephalon, fecundity and egg diameter) corresponded to a gradient of values from valley to canyon, headwater and subterranean populations. This result argues not for a simple distinction between epigean and hypogean populations but for an adaptation to an environmental gradient of constraints in which caves correspond to an extreme situation.     

Population ecology of Trichomycterus itacarambiensis, a cave catfish from eastern Brazil (Siluriformes, Trichomycteridae)

The population ecology of the trichomycterid catfish, Trichomycterus itacarambiensis, from the Olhos d'Àgua Cave, Itacarambi Co., Minas Gerais, eastern Brazil, was investigated by the mark-recapture method during the dry season of 1994 (April to October). The cave is subject to a pronounced seasonality, and is flooded during part of the rainy period. All individuals captured along the 5000 m long stream gallery (divided in 50 sections) were marked by tattooing, measured and examined for the degree of pigmentation reduction. About one third of the population is truly albinic; the remainder may exhibit partial depigmentation. After five bimestrial collections, 583 specimens have been marked, of which 150 were recaptured at least once. Estimated population size was 1500–2000 individuals longer than 20 mm SL. The total population size of T. itacarambiensis is considered small when compared to those of epigean trichomycterids and of other studied cavefishes as well. Mean population density was 0.15–0.20 individuals m^-2 throughout the dry season; it increased with the distance to the stream resurgence, probably due to the higher food availability upstream. This population density may be considered intermediate to those of other troglobitic fishes. Most recaptures (66%) were done in the same section as the previous capture. Active movements, both upstream and downstream, were recorded up to distances of 600 m; a few possibly passive, downstream movements covered distances from 900 to 1500 m. T. itacarambiensis catfishes move more frequently and for longer distances than the Brazilian blind pimelodids, Pimelodella kronei. Individual growth in T. itacarambiensis probably occurs in pulses, during the rainy seasons; interruption of growth in the dry season is attributed to the pronounced food shortage. The mean longevity was estimated as seven years. Differences between pigmented and albino individuals include a higher frequency of downstream movements and slightly higher growth rates in the latter.     

Feeding ecology and habitat preferences of the catfish genus Trichomycterus in low‐order streams of the Colombian Andes

Six lower order streams in the south‐west of Colombia were sampled on a monthly basis in order to determine the status of Trichomycterus species in relation to their food supply (macroinvertebrates), and physico‐chemical habitat. Fishes were sampled by electrofishing and samples taken for dietary analysis. Macroinvertebrates were collected using a Surber sampler. Trichomycterus spp. populations were present in all streams in habitats ranging from soft to hard substrata and from relatively stagnant waters to fast flowing streams. The average density of the fishes ranged from 0·06 to 1·14 individuals m⁻² with peaks in population corresponding to recruitment of individuals of <1 g. Trichomycterus spp. were found to be benthic carnivores with a diet mostly of aquatic insects. The index of relative importance for the dietary items was 35·0, 10·5, 1·9 and 7·8% for Chironomidae, Trichoptera, Ephemeroptera and Oligochaeta respectively. Combined with physical habitat data, ordinations of fishes and macroinvertebrate data suggested that differences in abundance among sites were driven by stream size and flow regime, indicating dominance of the physical habitat, although a high correlation between Trichomycterus spp. and Chironomidae abundances ( r  = 0·81, P  = 0·049) was also recorded.     

Spawning season, ovarian development and fecundity of female Trichomycterus corduvense (Osteichthyes, Siluriformes)

We studied female reproductive biology of Trichomycterus corduvense. The study was carried out in the Anizacate River (Córdoba, Argentina). Samples were collected throughout one year on a monthly basis. Seven oocyte phases were identified. Five ovarian stages were described based on the macroscopic analysis of the oocyte phases. The spawning season for the species ranges from October to February; it was determined based on variations in GSI and the existence of mature females. The dynamics of oocyte development of T. corduvense, indicated the asynchronism of maturation. The correlation coefficient between fecundity and the individual weight was very low. Therefore, we suggest that this coefficient cannot be used to predict T. corduvense fecundity.     

Pterocryptis buccata, a new species of catfish from western Thailand (Teleostei: Siluridae) with epigean and hypogean populations

Pterocryptis buccata sp. nov. is described from the vicinity of Sai Yok, Kanchanaburi Province, western Thailand. It can be distinguished from all other congeners by its prominent mandibular muscles causing the cheeks to appear inflated and the following unique combination of characters: 54–61 anal-fin rays, 7 pelvic-fin rays, 50–52 vertebrae, 4 mandibular barbels and vomerine teeth present in 2 separate patches. An achromatic population inhabits the Sai Yok Noi cave. This is the first report of a cavedwelling catfish from Southeast Asia.     

Sex ratio and sexual dimorphism of the anchovy Anchoa januaria (Actinopterygii, Engraulidae) in a tropical bay in south-eastern Brazil

Sex ratio and morphological traits of a very abundant anchovy Anchoa januaria were described in a tropical bay in south-eastern Brazil. The aim was to test the hypothesis that sexual dimorphism occurs due to the different reproductive roles of the sexes. A fish sampling programme was carried out between September 1998 and August 1999 at six sites: four sandy beaches and two lower-river sites. Population structure at river sites comprised adults only, ranging from 60 to 80 mm total length ( L _T), while at sandy beaches both juveniles and adults were found, ranging from 32 to 80 mm L _T. Well-balanced 'spawning school' at river sites during reproduction were detected, while female-dominated schools occurred in the bay feeding areas. Males had relatively longer pectoral fins, slightly larger hearts and more somatic mass than females. Females outnumbered males at sizes >67 mm L _T and had significantly longer intestines and heavier livers than males. The largest size reached by females was probably related to a higher growth rate as they have a larger intestinal absorbing area for nutrients. The prediction of higher energetic investment in reproduction by females that should have larger organs associated with food acquisition and processing to produce energy-rich eggs was confirmed for A. januaria in Sepetiba Bay.     

The Serra da Mantiqueira, south-eastern Brazil, as a biogeographical barrier for fishes

Aim  To present a fish fauna survey from rivers draining the south-western region of the Serra da Mantiqueira, and to investigate the effectiveness of that mountain range as a biogeographical barrier isolating the fish faunas of the Paraíba do Sul basin and the upper Paraná river.
Location  Six drainages from the south-western portion of the Serra da Mantiqueira in the region of Campos do Jordão, Brazil, were studied. They included three drainages belonging to the Paraíba do Sul basin (Piracuama, Grande and Buenos), and three belonging to the Sapucaí basin, Rio Paraná system (Sapucaí-Mirim, upper Sapucaí and Santo Antônio).
Methods  The survey was conducted in two sampling trips supplemented by examination of specimens preserved in museum collections. Parsimony analysis of endemicity (PAE) was used to detect the hierarchy of relationships among the six drainages.
Results  A total of 47 species of fishes was recorded in the six drainages. The main watershed divide is an effective barrier between the two basins, with 28 species occurring exclusively in the Paraíba do Sul versant, and 15 occurring exclusively on the slope of the Sapucaí basin. The PAE of 18 species with cladistically informative distributions and unproblematic taxonomic diagnoses produced a single area cladogram, with complete congruence among 14 species.
Main conclusions  The main Mantiqueira watershed divide is an effective biogeographical barrier isolating the fish faunas of the Paraíba do Sul and the Sapucaí basin (upper Paraná system). Previous hypotheses of a past connection between the upper Paraná and the Paraíba do Sul are not supported by extant species distributions in the Serra da Mantiqueira region. Within-basin drainage differentiation, however, is relatively low.     

Allozyme differentiation and relationships within Hypostomus Lacépède, 1803 (Osteichthyes: Loricariidae) from the upper Paraguay River basin, Brazil

Nine hypostomine populations from Manso Reservoir (Rio Manso and Rio Cuiabá, upper Paraguay River basin, Brazil) were surveyed using allozyme electrophoresis. Three, sampled at the same sites, were not identified to the species level and were designated as Hypostomus sp. 1, Hypostomus sp. 2 and Hypostomus sp. 3. The survey resulted in 25 loci from 14 scored enzyme systems. Allozyme data allowed diagnostic marker recording for all species analyzed, including the undescribed taxa. Mean expected heterozygosity values were quite variable, ranging from 0.029 to 0.079. Hypotheses to explain this variation are discussed. The allelic frequencies and Nei's genetic identity values showed that Hypostomus sp. 1, Hypostomus sp. 2 and Hypostomus sp. 3 should be considered true biological species, and distinct from the other five Hypostomus species and Pterygoplichthys anisitsi.     

Population ecology ofPimelodella kronei,troglobitic catfish from Southeastern Brazil (Siluriformes,Pimelodiae)

Synopsis Pimelodella kronei, a cave derivative of the pimelodid catfishP. transitoria, has been found in five caves of the Ribeira River valley, SE Brazil. I investigated the ecology of the most conspicuous population, that from Areias Caves, by capture-mark-recapture. During the two-year study, 170 specimens ofP. kronei were marked, 81 were recaptured at least once, multiple recaptures were frequent. These blind catfishes tended to be recaptured in the same site where they were marked, suggesting a sedentary life and possibly territoriality. The home range was 200 m along the stream, or more where food was scarcer.P. kronei population size in 800 m of permanent stream was 150–200 individuals.P. transitoria also inhabits the cave, at a density ten times lower. The growth rate ofP. kronei was less than 0.1 cm × month^–1, and longevity was 10–15 years. These data, and evidences of an infrequent reproduction, indicate a K-selected life cycle, probably as a consequence of food scarcity.     

Dry soil determines the pseudoviviparous reproduction in Comanthera nivea (Eriocaulaceae) in the Campos Rupestres in south-eastern Brazil

Pseudovivipary is an asexual reproduction strategy correlated with extreme environments. Comanthera nivea occurs in habitats with low water retention. This study investigated the effect of soil moisture availability on C. nivea pseudoviviparous reproduction and flowering. We established four permanent plots (1 × 1 m), two in a shaded area, in which we marked 15 rosettes in each plot, and two in a full-sun area, in which we marked 10 rosettes in each plot. We made monthly observations from August 2016 to January 2017, to quantify the number of flower heads and of pseudoviviparous ramets per rosette, and measured soil moisture. Our results showed a high correlation between soil moisture and flowering. Flowering in C. nivea occurs in periods of increased soil moisture, whereas pseudoviviparous reproduction occurs in the driest period. The advantages of a pseudoviviparous canopy-forming strategy in habitats with scarcity of water in the soil are discussed.     

Systematics and distribution of Thorea (Thoreaceae, Rhodophyta) from central Mexico and south-eastern Brazil

Thirteen populations of Thorea were analyzed from central Mexico and south‐eastern Brazil. All populations were considered as belonging to a single species [Thorea hispida (Thore) Desvaux], with wide variation of morphological features. Secondary branches varying in frequency were observed in several populations with an overlapping in the range of branch density for Thorea violacea Bory and T hispida (0–9 and 11–41 per 30 mm, respectively). As this is the most distinguishing character and on the basis of the overlapping (within a same population or even a single plant), we regarded T. violacea as a synonym of T hispida.‘Chantransia’ stage in culture, as well as gametophyte and carposporophyte were described in detail. We confirmed tine coexistence of asexual monosporangia with sexual reproductive structures (carpogonia and spermatangia) and carposporangia. Size, content, arrangement and chromosome number were the most distinctive characteristics among spermatangia, carposporangia and monosporangia. Monosporangia can be promptly differentiated from spermatangia by their granulated content and larger size but they are similar to carposporangia in shape and size; however, monosporangia are not arranged in fascicles. Structures resembling bisporangia were observed in female plants of some populations. Chromosome numbers were n = 4 for spermatangia and fascicle cells, and 2n ca 8 for gonimoblast filaments, carpospores and the ‘Chantransia’ stage cells. The populations of Thorea from central Mexico and south‐eastern Brazil corroborated the known world distribution for T. hispida, consisting dommantly of tropical to subtropical rainforests, sometimes extending into warm temperate areas. Thorea hispida occurred in warm (temperature 17.6–28.O°C), neutral to alkaline (pH 7.0–8.0), high ion content (specific conductance 59–2140 μS cm^?1), moderate flowing (current velocity 17–43 cm/s) and shallow waters (depth <50cm); these data are essentially similar to previous reports.     

The end of regressive evolution: examining and interpreting the evidence from cave fishes

The evolution of hypogean fauna in general and hypogean fishes in particular has been controversial. Explanations regarding the reduction or loss of phenotypic characters such as eyes and pigmentation range from neo‐Lamarckism to neutral mutations, with 'regressive evolution' being a catch‐all characterization for such processes. The assumptions required for special evolutionary mechanisms underlying the evolution of cave dwellers have been based on generalizations about the animals and their environments drawn from relatively few observations. The evidence offered for notions such as pre‐adaptation of colonizing fauna and the purported impoverished nutrients in all caves is examined and it appears that the generalizations cannot be supported. Some major accomplishments in field and laboratory studies of hypogean fishes are summarized, including work highlighting developmental phenotypic plasticity. At the end, it is argued that evolution of hypogean fauna can be explained by well‐known mechanisms within the current context of evolutionary biology.     

Comparative trophic ecology of two sympatric guitarfishes Pseudobatos (Chondrichthyes,Rhinobatidae) from Southeast Brazil,southwestern Atlantic

The present study compares the trophic ecology of two guitarfishes (Pseudobatos percellens and Pseudobatos horkelii) from the continental shelf of the São Paulo State, Brazil, caught by the bottom pair trawls between 2007 and 2009. These two sympatric species are under different threat categories, “Vulnerable” and “Critically Endangered,” respectively, according to Brazilian agencies. Thus, any study considering trophic ecology parameters is pivotal in understanding the trophic ecology role of such species in the ecosystem. The authors analysed 500 stomachs of P. percellens and 108 of P. horkelii, quantifying with dietary indexes: numerical (%N), gravimetric (%W), frequency of occurrence (%FO) and the prey-specific index of relative importance (%PSIRI). For P. percellens and P. horkelii, 26 and 14 different prey items were found, respectively. Crustacea and Teleostei were the most important prey items for both species, indicating a specialist feeding behaviour due to their low niche amplitude. The results provide evidence related to ontogenetic dietary shift in P. percellens and individual-level diet specialization in both species. These two benthic-demersal elasmobranchs are important mesopredators (3,7 for P. percellens, and 3,5 for P. horkelii) in the study area, with high trophic-level values.     

Locomotor activity rhythms in cave fishes from Chapada Diamantina, northeastern Brazil (Teleostei: Siluriformes)

Previous studies on the locomotor activity of troglobitic (exclusively subterranean) species have shown that circadian rhythmicity may be reduced in populations evolving in the absence of zeitgebers such as daily cycles of light and temperature; therefore, circadian activity rhythms, although not infradian nor ultradian rhythms, seem to have been selected by external, ecological factors. We studied the locomotor activity of a highly specialized Heptapteridae catfish (undescribed genus and species) from Chapada Diamantina, NE Brazil, compared to another specialized Brazilian troglobitic heptapterid, Taunayia sp. Locomotor activity was continuously measured in the laboratory with an infra-red photocell system. Seven specimens of the new genus were tested, each one during 14 consecutive days according to the following schedule: three days in DD → seven days in LD (12:12 h) → four days in DD. Data were submitted both to fast Fourier transform periodogram followed by Siegel's test of significance and Lombs - Scargle periodogram techniques in order to identify spectral composition of the time series. In general, results were similar to those obtained for Taunayia sp.: (a) for most specimens, absence of significant circadian components in locomotor activity under DD; (b) for all specimens, significant circadian components under LD, with higher levels of activity during the dark phase, as expected for species belonging to nocturnal epigean taxa; (c) for most specimens, no residual oscillations recorded when free-running conditions were reinstalled. Circadian locomotor activity detected under LD may thus be interpreted as a direct, masking effect of the LD cycle. This suggests a pattern for highly specialized troglobitic species, isolated for a long time in the subterranean habitat, with a progressive reduction of circadian time-keeping mechanisms. Our studies also demonstrate the potential of subterranean organisms for investigation of the origin, evolution, functioning and genetics of circadian rhthmicity.     

Diapause, pupation sites and parasitism of the horn fly, Haematobia irritans, in south-eastern Brazil

In order to verify the occurrence of diapause, preference for pupation sites and hymenopteran parasitism, the pupae of the horn fly, Haematobia irritans (Diptera: Muscidae), were collected from undisturbed cattle dung pats in pastures, and adults of the fly were sampled from cattle in São Paulo State, south-eastern Brazil, from April 1993 to July 1994. Diapause was verified in 7.7% of pupae sampled from pastures in June and July of 1993 and in 9.9% of those sampled in May, June and July of 1994 (overall rate of 9.1%). Approximately 8.3% of the pupae were parasitized by microhymenopterans, mostly Spalangia nigroaenea and S.cameroni (Hymenoptera: Pteromalidae). Horn fly pupae were found almost exclusively inside the pat or in the soil immediately beneath and adjacent to it, and very few were collected elsewhere. Pupa mortality was 54.4% and did not change significantly during the year, but mortality was greater among pupae collected in pastures when compared to those obtained from experimental pats, lacking natural enemies.     

Epigean and subterranean ichthyofauna from the São Domingos karst area, Upper Tocantins River basin, Central Brazil

In a survey of epigean and cave streams in the São Domingos karst area, 38 species were present in the stream reaches, including 10 characiforms, 19 siluriforms, seven gymnotiforms and two perciforms. One species of Astyanax and the new armoured catfish species Parotocinclus were the most common epigean fishes in São Domingos. The most conspicuous non-troglomorphic cave fishes were Hoplerythrinus unitaeniatus , Astyanax sp., Brycon sp. and two species of Imparfinis , with I. hollandi being the most common fish in most caves. São Domingos karst area has the most diverse and abundant Brazilian cavefish fauna, not only in terms of troglobitic species but also in general fish richness, with 22 non-troglomorphic species recorded in caves in addition to five troglobitic ones. Most fishes examined for stomach contents had at least partially full stomachs. The studied fishes were carnivorous, feeding primarily on aquatic insects. Fishes with developed gonads recorded in caves were I. hollandi , Rhamdia quelen , Pseudocetopsis plumbeus , Hoplerythrinus unitaeniatus and Cichlasoma araguaiensis , indicating a potential for reproduction in the subterranean habitat.     

Fossil record of a silurid catfish from the Middle Miocene Sanuki Group of Ohkawa, Kagawa Prefecture, Japan

A fossil specimen identified as a silurid catfish (92.5 mm SL) was collected from the Middle Miocene Sanuki Group (15.8±0.9 Ma) of Ohkawa, Kagawa Prefecture, Japan. This is the oldest certain record of a silurid catfish. Morphological characteristics of the specimen are as follows: 52 or 53 vertebrae, 61 or 62 anal fin rays, a stout, short spine (11%SL) and 10 or more soft rays of the pectoral fin, 8 or more pelvic fin rays, 8 or more branchiostegal rays, head length of ca. 24%SL, and most probably not forked caudal fin. The fossil specimen is clearly distinct from three extant silurids in Japan, and probably belongs to an undescribed form considering its geological age.