The relationship between humidity, light and the activity pattern of a velvet worm, Epiperipatus sp. (Onychophora: Peripatidae), from Bahía Drake, South Pacific of Costa Rica / A relação entre a humidade, luz e o padrão de atividade de um peripato, Epiperipatus sp. (Onychophora: Peripatidae), de Bahia Drake, Pacífico Sul da Costa Rica

Abstract Even though the Onychophora represent a whole phylum, observations of their activity pattern in nature are almost non-existent. Here we report on the relationship between humidity and light and activity pattern of a new species of velvet worm, genus Epiperipatus, from four years of field observations in the South Pacific of Costa Rica. We found that most activity occurs during the driest and darkest nights of the year, in contrast with theoretical predictions.

Resumo Onychophora constituem um filo de animais. Não obstante, as observações do comportamento sazonal das espécies de "peripatos" na natureza são praticamente inexistentes. Com base em quatro anos de observações em campo, nós demostramos a relação entre umidade e luz, e padrão de atividade diária de uma nova espécie no gênero Epiperipatus, do Pacífico Sul da Costa Rica. Descobrimos que a maioria das atividades ocorre durante as noites mais secas e mais escuras do ano, em total contraste com as previsões teóricas.

The relationship between humidity, light and the activity pattern of a velvet worm, Epiperipatus sp. (Onychophora: Peripatidae), from Bahía Drake, South Pacific of Costa Rica.

Even though the Onychophora represent a whole phylum, observations of their activity pattern in nature are almost non-existent. Here we report on the relationship between humidity and light and activity pattern of a new species of velvet worm, genus Epiperipatus, from four years of field observations in the South Pacific of Costa Rica. We found that most activity occurs during the driest and darkest nights of the year, in contrast with theoretical predictions.

The relationship between humidity, light and the activity pattern of a velvet worm, Epiperipatus sp. (Onychophora: Peripatidae), from Bahía Drake, South Pacific of Costa Rica

Abstract Even though the Onychophora represent a whole phylum, observations of their activity pattern in nature are almost non-existent. Here we report on the relationship between humidity and light and activity pattern of a new species of velvet worm, genus Epiperipatus, from four years of field observations in the South Pacific of Costa Rica. We found that most activity occurs during the driest and darkest nights of the year, in contrast with theoretical predictions.

Resumo Onychophora constituem um filo de animais. Não obstante, as observações do comportamento sazonal das espécies de peripatos na natureza são praticamente inexistentes. Com base em quatro anos de observações em campo, nós demostramos a relação entre umidade e luz, e padrão de atividade diária de uma nova espécie no gênero Epiperipatus, do Pacífico Sul da Costa Rica. Descobrimos que a maioria das atividades ocorre durante as noites mais secas e mais escuras do ano, em total contraste com as previsões teóricas.

Disparity, decimation and the Cambrian "explosion": comparison of early Cambrian and present faunal communities with emphasis on velvet worms (Onychophora).

The controversy about a Cambrian "explosion" of morphological disparity (followed by decimation), cladogenesis and fossilization is of central importance for the history of life. This paper revisits the controversy (with emphasis in onychophorans, which include emblematic organisms such as Hallucigenia), presents new data about the Chengjiang (Cambrian of China) faunal community and compares it and the Burgess Shale (Cambrian of Canada) with an ecologically similar but modern tropical marine site where onychophorans are absent, and with a modern neotropical terrestrial onychophoran community. Biovolume was estimated from material collected in Costa Rica and morphometric measurements were made on enlarged images of fossils. Cambrian tropical mudflats were characterized by the adaptive radiation of two contrasting groups: the vagile arthropods and the sessile poriferans. Arthropods were later replaced as the dominant benthic taxon by polychaetes. Vagility and the exoskeleton may explain the success of arthropods from the Cambrian to the modern marine and terrestrial communities, both in population and biovolume. Food ecological displacement was apparent in the B. Shale, but not in Chengjiang or the terrestrial community. When only hard parts were preserved, marine and terrestrial fossil deposits of tropical origin are even less representative than deposits produced by temperate taxa, Chengjiang being an exception. Nutrient limitations might explain why deposit feeding is less important in terrestrial onychophoran communities, where carnivory, scavenging and omnivory (associated with high motility and life over the substrate) became more important. Fossil morphometry supports the interpretation of "lobopod animals" as onychophorans, whose abundance in Chengjiang was equal to their abundance in modern communities. The extinction of marine onychophorans may reflect domination of the infaunal habitat by polychaetes. We conclude that (1) a mature ecological community structure was generalized during the Cambrian, and even biodiversity and equitability indices were surprisingly close to modern values; (2) the morphological diversity and geographic distribution of onychophorans indicate a significant pre-Cambrian evolutionary history which does not support the "explosion" hypothesis; (3) disparity among phyla was not as important as the explosion-decimation model predicts, but in the case of onychophorans, disparity within the phylum was greater than it is today and its reduction may have been associated with migration into the sediment when large predators evolved.

The effects of methodological limitations in the study of butterfly behavior and demography: a daily study of Vanessa atalanta (Lepidoptera: Nymphalidae) for 22 years.

Normally, butterfly behavior and population size are studied intensively for brief periods or occasionally for long periods, not in detail for long periods, producing an incomplete view in both cases. How time limitation affects studies has been unknown for a long time. This paper analyses this problem based on an intensive long term study of Vanessa atalanta (L.) that covered nearly 8000 days, most of them consecutive, for 22 years (April 15, 1977-April 14, 1999), in a subtropical habitat near Orlando, Florida. There is no evidence that ethological studies are affected by their normally brief duration (one year or less), but the analysis of yearly values hid the associations of number of individuals and arrival time with climate. In small areas, isolated population counts lasting less than two weeks are not reliable, according to this study. We found no difference in number of visitors for El Niño years. The daily number of visitors was inversely correlated with temperature and precipitation, but arrival time of the first visitor was positively correlated with both. The number of visitors reaches a peak near the end of Winter. The activity period span is greater than in more seasonal climates. Individuals were active even at 10 degrees C and with 9 m/s winds. Individuals with fresh wing condition were most common from January to June. There were 82 atypical cases of individuals arriving before 12:00 hr. Aerial interactions were seen whenever there was more than one individual in the site (i.e. 41% of days, N = 7634 total days). Only once in these 22 years was predation seen.

Ultrastructure of the bacteria Campylobacter and Helicobacter: implications for the phylogeny of mammal gastric bacteria.

Negative staining, thin sections, and surface replica methods were used to produce ultrastructural descriptions of curved-shaped, flagelated bacteria Campylobacter jejuni, Helicobacter pylori, and H. muridarum, the last one from the ileon of mice. The former has nude monotrichous flagella, the others have the sheated lobotrichous type. H. muridarum presents 10-12 periplasmic fibers. A cladogram of some gastric bacteria, based on the evolutionary history of the mammal hosts, hypothesizes that (1) the genus Helicobacter evolved about 65 million years ago and that (2) primate parasites such as H. pylori and H. nemestrinae are close relatives, as are parasites of carnivores which include H. mustelae, H. felis and H. acynonyx.

Thirty-five years of Tropical biology: a quantitative history.

Citation indices are inappropriate measures of scientific output and impact. For that reason, nonparametric statistics were preferred to analyze 35 years of publication on Tropical biology in the Revista de Biología Tropical. The most frequent subjects are animal taxonomy, human biology-including medicine- ecology and animal behavior. Botany papers are less frequent and mainly deal with morphology and taxonomy. Applied studies are not predominant. In that period, only one case of unethical experimentation with humans was discovered in a paper of Mexican origin. The proportion of foreign institutions publishing in the journal has increased from 23% (1953-1963) to 50% in the last decade; similarly, the number of studies done in the Neotropics is on the rise. English and Spanish are equally frequent, although English is the basic language of ethology and evolution and Spanish predominates in papers on animal morphology and parasitology. Most Costa Rican authors publish in Spanish, in contrast with many of their Latin American colleagues. In recent years, there is a tendency to publish shorter papers written by more than one author. The Revista de Biología Tropical, covered by 18 data bases, accounts for most exchanges and sales in the Universidad de Costa Rica and has worldwide distribution.