The ultrastructure of spermatozoa of two species of Aegla (A. parana and A. quilombola) (Crustacea, Decapoda) endemic to Brazil.

The previously published ultrastructure of Aegla spermatozoa contributed to the phylogenetics of this unique taxon. The present study describes the spermatozoa of two additional aeglids, Aegla parana and A. quilombola. The spermatozoa consist of two hemispheres of the approximate same size and a bilayered acrosomal vesicle; both characteristics of the genus Aegla. The similarity of spermatozoa ultrastructure observed between A. parana and A. quilombola and the endemic Australian anomuran, Lomis hirta (Lomidae) reflects a sister group relationship, even though both are from different regions of the world and different environments today. Aeglid spermatozoa share the same organization with Lomis including the two equal size hemispheres separated by a membrane also two layers in the acrosomal vesicle with the external layer being surrounded by another membrane. The number of spermatozoa microtubular arms is unclear in Aegla, however, they are present in both the nucleus and cytoplasm. This observation does not agree with the presence of spermatozoa arms only in the nucleus, as an exclusive character for Aegla, as proposed previously. The presence of lipid-droplets and peroxisomes was observed only in the spermatozoa of A. quilombola. The greatly reduced number of spermatozoa observed in all specimens analyzed raises concerns about the conservation of several threatened species. In addition, the absence of any spermatophores seems to be a characteristic of the Aeglidae to date.

Male reproductive system of the freshwater prawn Macrobrachium brasiliense (Decapoda: Palaemonidae): Notes on spermatophore formation and sperm count.

Studies on the morphology of the reproductive system are essential for understanding the reproduction processes of species or even within genera or families. The present study aimed to describe the functional morphology of the male reproductive system, spermatophore formation, and sperm count of Macrobrachium brasiliense. The anatomy of the reproductive system consists of a pair of testes from which the vasa deferentia (VD) starts, extending to the fifth pair of pereopods. The VD is divided into three regions: proximal (PVD), middle (MVD), and distal (DVD). In the PVD, there is a prominent fold, the typhlosole, formed by columnar cells. The typhlosole disappears in the MVD, being incorporated into one of the faces of the VD wall, identified by its simple columnar epithelium while the remainder of the vessel wall is formed by squamous or simple cubic epithelium. Columnar cells produce type-II and III secretion. The epithelium in the DVD is made up only of cubic cells. Low sperm concentration was observed when compared to other species of the genus Macrobrachium. In conclusion, the typhlosole and columnar epithelium are responsible for the asymmetric spermatophore, which seems the pattern of Macrobrachium that is probably shared with other caridean shrimps.

The first zoeal stage of the deep-sea crab Tetraxanthus rathbunae (Brachyura: Pseudorhombilidae): a morphological description.

The description of the first zoea stage of Tetraxanthus rathbunae Chace, 1939, the third known zoea of Pseudorhombilidae and the first for Tetraxanthus, was carried out from laboratory hatched larvae. Their morphology differs from other pseudorhombilid species previously described primarily in the number and type of setae on the antennule, antennal exopod, maxilla, first maxilliped, and second maxilliped. These zoeae, however, share the same number of spines on the carapace (rostral, dorsal, and lateral), absence of the endopod on the antenna, long and well-developed spinose protopod, maxillary exopod with four marginal plumose setae and a robust posterior process, the absence of setae on the basis of the second maxilliped, and the presence of three lateral spines on each side of the furca. The results obtained in the present study are of great importance in being only the third known first stage pseudorhombilid zoea and the first for the Tetraxanthus, as well as in contributing to the identification of brachyuran planktonic zoea. Additionally, it also provides information that can help elucidate pseudorhombilid phylogeny.

Checklist of decapod crustaceans from the coast of the So Paulo state (Brazil) supported by integrative molecular and morphological data: V. Dendrobranchiata and Pleocyemata [Achelata, Astacidea, Axiidea, Caridea (Alpheoidea and Processoidea excluded), Gebiidea, Stenopodidea].

This checklist is the fifth and last compilation on the decapod crustaceans reported to So Paulo (Brazil) coastal area, resulting from long-term multidisciplinary projects, which combined morphological analyses and molecular techniques. The current research includes 75 decapod species, herein referred as shrimps/lobsters-like (shrimps, ghost-shrimps, lobsters, and related groups), reported to So Paulo coastal area. These species occur in marine, estuarine, and amphidromous habitats and are classified into 21 families as follow: Aristeidae (2 spp., 2 genera), Atyidae (4 spp., 2 genera), Axianassidae (1 sp., 1 genus), Callianassidae (1 sp., 1 genus), Callichiridae (6 spp., 4 genera), Crangonidae (1 sp., 1 genus), Glyphocrangonidae (1 sp., 1 genus), Luciferidae (2 spp., 2 genera), Nephropidae (4 spp., 2 genera), Palaemonidae (15 spp., 9 genera), Palinuridae (2 spp., 1 genus), Pandalidae (1 sp., 1 genus), Pasiphaeidae (1 sp., 1 genus), Penaeidae (10 spp., 6 genera), Sergestidae (3 spp., 3 genera), Sicyoniidae (4 spp., 1 genus), Scyllaridae (5 spp., 3 genera), Solenoceridae (4 spp., 3 genera), Stenopodidae (2 spp., 1 genus), and Upogebiidae (6 spp., 1 genus). We generated new sequences of cytochrome oxidase subunit I (barcode region) and 16S genes (51 and 54, respectively) of 54 species. Our examination concluded that 75 shrimps/lobsters-like species are reported to the So Paulo coast. We excluded Leander tenuicornis (Palaemonidae), Penaeus setiferus (Penaeidae), Philocheras gorei (Crangonidae), and Rhynchocinetes typus (Rhynchocinetidae) from this list.

Seminal fluid and spermatophore production in a western Atlantic invasive swimming crab, Charybdis hellerii, reveals a different pattern to Portunoidea.

The male reproductive system in Portunoidea is voluminous in order to produce the sperm plug, avoiding sperm competition. The portunid crab, Charybdis hellerii, is a successful invasive species, and this study describes the male reproductive system under light and electron microscopy and evaluates the gonadosomatic index and spermatophore dehiscence compared to other species that produce a sperm plug. The reproductive system is small, and its gonadosomatic index much lower than those of other Portunoidea that produce a sperm plug. The spermatophores are stored in the anterior part of the vas deferens, which is uncommon in Brachyura. Lateral outpocketings are found in the short, middle, and posterior parts of the vasa deferentia, where spermatophores are not found. The seminal fluid composition is different from the species that produce sperm plug. The usual portunid spermatophore wall is absent and the round coenospermic to even cleistospermic spermatophores are enclosed by secretions. This mucous-type spermatophore undergoes dehiscence in seawater or when passing through the gonopod. C. hellerii differ from other Portunoidea described regarding a low amount of seminal fluid production, spermatophore storage, and not show traits of producing sperm plugs. These different male reproductive features can lead to different female sperm storage in Portunoidea.

Checklist of decapod crustaceans from the coast of the São Paulo state (Brazil) supported by integrative molecular and morphological data: IV. Infraorder Anomura: Superfamilies Chirostyloidea, Galatheoidea, Hippoidea and Paguroidea.

This checklist is the fourth contribution resulting from a long-term multidisciplinary project which combined morphological analyses and molecular techniques (mitochondrial DNA markers) for accurate identification of marine and coastal decapod crustaceans of São Paulo State (Brazil). We provide a list of 63 species of the following 11 families of 4 superfamilies of Anomura: Albuneidae (4 spp.), Blepharipodidae (1 sp.), Chirostylidae (1 sp.), Diogenidae (18 spp.), Hippidae (1 sp.), Munididae (8 spp.), Munidopsidae (1 sp.), Paguridae (13 spp.), Parapaguridae (2 spp.), Porcellanidae (13 spp.), and Pylochelidae (1 sp.). Seven species previously reported from the region were neither collected nor found in museum collections during our study, including one (Sympagurus dimorphus) that we suggest to be removed from São Paulo coast fauna lists. We generated new sequences of cytochrome oxidase subunit I (barcode region) and 16S genes of 44 species. This anomuran inventory may serve as guideline for future studies on taxonomy, conservation, population genetics, biogeography, and phylogenetics, which might flag species that deserve further investigations and concerns.

Checklist of decapod crustaceans from the coast of the São Paulo state (Brazil) supported by integrative molecular and morphological data: III. Infraorder Brachyura Latreille, 1802.

This checklist is the third part of a series derived from a long-term multidisciplinary project on the biodiversity of decapod crustaceans from marine and coastal environments of São Paulo state (Brazil). We integrated molecular techniques (DNA markers) and morphological analyses of adult specimens for accurate identifications. We compilated 185 species from the literature, but we confirmed the presence of 168 species: 130 of which we sampled, analyzed and obtained sequences (COI and/or 16S totalizing 113 sequences) and 38 that were not directly collected but were confirmed by analyses. In addition, 27 had their distribution removed from São Paulo due to uncertainties, and absence of material as voucher. Five species were reported for the first time on the coast of São Paulo (Calappa ocellata, Neohelice granulata, Teleophrys pococki, Teramnonotus monodi, Tetraxanthus rathbunae) and one on the Brazilian coast (Pseudomedaeus agassizi). Most of the non-sampled species previously reported on the coast of São Paulo might be considered doubtful records stablished in the past by inaccurate analyses, which assumed extended distribution to the area and/or misidentifications. At this time and based on our refined compilation, we can estimate the brachyuran diversity on the coast of São Paulo in 168 species. This detailed inventory contributes to the knowledge on the local decapod fauna by checking available dataset, adding new species records in São Paulo and new sequences to GenBank database. These data may serve as baseline for future identifications and studies on conservation, population genetics, biogeography and phylogenetics, which might flag species that deserve further investigations and concerns.

Validation of Xiphopenaeus dincao Carvalho-Batista, Terossi, Zara, Mantelatto amp; Costa and Xiphopenaeus baueri Carvalho-Batista, Terossi, Zara, Mantelatto amp; Costa (Decapoda: Penaeidae) from western Atlantic.

Two species of Penaeidae shrimp from western Atlantic were described by Carvalho-Batista et al. (2019) as Xiphopenaeus dincao and Xiphopenaeus baueri. The descriptions and figures presented by Carvalho-Batista et al. (2019) and the posterior author's correction (Carvalho-Batista et al., 2020) characterize the species. However, the journal issue in which the description was published is online only, and the article with the new names did not include a Zoobank registration number (LSID), required for validation of new names in electronic-only publications (ICZN 2012). Thus, the names Xiphopenaeus dincao and Xiphopenaeus baueri, as published in Scientific Reports 9: 15281, is not available according the International Code of Zoological Nomenclature (ICZN 1999, 2012). Therefore, the present note serves to validate the names Xiphopenaeus dincao and Xiphopenaeus baueri by fulfilling ICZN conditions for nomenclatural availability. Type specimens of both species are deposited in Museu de Zoologia da Universidade de São Paulo (MZUSP), São Paulo, Brazil.

Ultrastructure and histochemistry of the male reproductive system of the genus Callinectes Stimpson, 1860 (Brachyura: Portunidae).

We described the ultrastructure and histochemistry of the reproductive system of five Callinectes species, and evaluate the seasonal variation in weight of the reproductive system and hepatopancreas by comparing annual changes of somatic indices. The somatic indices changed little throughout the year. In Callinectes, spermatogenesis occurs inside the lobular testes and, within each lobule, the cells are at the same developmental stage. Spermatogenesis and spermiogenesis follow the same development pattern in all Callinectes studied. Mature spermatozoa are released into the seminiferous ducts through the collecting ducts. Cells of the vas deferens are secretory as evidenced by rough endoplasmic reticulum, Golgi complex, and secretory vesicles that produce the seminal fluid. The anterior vas deferens shows two portions: proximal and distal. In proximal portion (AVDp), spermatozoa are clustered and embedded in an electron-dense, basophilic glycoproteinaceous secretion Type I. In the distal portion (AVDd), the spermatophore wall is formed by incorporation of a less electron-dense glycoproteinaceous secretion Type II. The secretion Type I change to an acid polysaccharide-rich matrix that separates the spermatophores from each other. The median vas deferens (MVD) stores the spermatophores and produces the granular glycoproteinaceous seminal fluid. The posterior vas deferens (PVD) has few spermatophores. Its epithelium has many mitochondria and the PVD seminal fluid changes into a liquid and homogeneous glycoprotein. Many outpocketings in the PVD and MVD help to increase the fluid production. Overall, the reproductive pattern of Callinectes is similar to other species that produce sperm plugs. The secretions of AVD, MVD, and PVD are responsible for the polymerization that forms the solid, waxy plug in the seminal receptacle. The traits identified here are common to all Portunidae species studied so far.

Size at onset of sexual maturity in Macrobrachium amazonicum (Heller, 1862) phenotypes: an integrative approach.

The size at the onset of sexual maturity (SOM) was determined in four hololimnetic populations of Macrobrachium amazonicum using morphometric, physiological and functional criteria. Male prawns from two populations analyzed had hypertrophied chelipeds and large body proportions, showing the presence of four morphotypes, i.e. large-size phenotype (LS). However, the other two populations showed smaller males without morphotypes, i.e. small-size phenotype (SS). The development of sexual weapons in males modulated the mating system and SOM in this species. It was verified that there is a synchrony between physiological and functional maturities in SS males. On the other hand, functional maturity in LS males occurred after physiological and morphological maturities. In females, we verified synchronization between morphological and functional maturities. The results obtained indicated that, in both sexes, physiological maturity anticipates the others criteria. There were no differences between the sequential scheme of sexual maturity for female phenotypes, being: physiological → functional morphological. However, the evaluation of sexual maturity in males must take into account the phenotype of population, since that was modulated by functional maturity. The sequential scheme for LS males is: physiological → morphological → functional, while for SS males it is: physiological = functional → morphological.

Author Correction: A multigene and morphological analysis expands the diversity of the seabod shrimp Xiphopenaeus Smith, 1869 (Decapoda: Penaeidae), with descriptions of two new species.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A multigene and morphological analysis expands the diversity of the seabod shrimp Xiphopenaeus Smith, 1869 (Decapoda: Penaeidae), with descriptions of two new species.

After being stable for nearly a century, the taxonomic history of the genus Xiphopenaeus has been marked by many changes in the last three decades. The taxonomic status of the Atlantic species has a low resolution, and many species are still undefined and grouped as cryptic species. Here we employed an integrative approach to define the species of Xiphopenaeus and the morphological characters needed to differentiate them. We combined the analyses of two molecular markers (COI and 16 S rDNA), scanning electron microscopy and light microscopy. Based on specimens from 17 localities from the Atlantic and Pacific oceans, we detected five divergent genetic groups, three in the Atlantic (A1, A2, A3) and two in the Pacific (P1, P2). Male secondary sexual characters were able to differentiate four out of the five genetic groups. Group A1 corresponds to X. kroyeri, and A2 and A3 correspond to new species. We redescribed the genus and two new species are described and illustrated: Xiphopenaeus dincao nov. sp. (A2) and Xiphopenaeus baueri nov. sp. (A3). Since the holotype of X. riveti was missing and the specimen analysed from group P2 was a female, the status of the species of Xiphopenaeus from the Pacific remains unresolved.

Integrative depiction of the male reproductive system of the commercial purple crab Homalaspis plana (Platyxanthidae): Structure and function.

The information available on structures and function of reproductive systems are female-biased in many animal groups and crabs are not an exception. However, knowledge about the male reproductive system can help us to understand evolutionary and ecological processes such as the mating system and mating behavior. This study focuses on an integrative description of the principal regions of the male reproductive system of the purple crab, Homalaspis plana, a commercially exploited crab from the southeastern Pacific. For this description a combination of morphological observation, gravimetric records, histological and histochemical techniques and biochemical analysis were used. Also, a gross description of the seminal receptacle of the female was performed. The male reproductive system of H. plana was highly extended and complex, with a great capacity to produce and store spermatophores and secrete, at least, two kinds of seminal fluids. Sperm production, sperm packaging in spermatophores, storage of spermatophores and seminal liquid secretion were functions localized in specific regions. The vasosomatic index was the highest recorded to date in crabs, symptomatic of a high investment in reproduction. All these traits allow identification of H. plana as an internal sperm plug producer, which matches well with the highly extensible seminal receptacle of females. The great quantity of seminal material transferred to females during mating indicates that males may be able to mate only one time in the reproductive season and thus this species could be vulnerable to sperm depletion in males and sperm limitation in females if the fishery substantively reduced the abundance of males in the populations.

Checklist of decapods (Crustacea) from the coast of São Paulo State (Brazil) supported by integrative molecular and morphological data: II. Infraorder Caridea: family Alpheidae.

This study is part of a series of checklists resulting from a long-term multidisciplinary project on the biodiversity of decapod crustaceans from the marine and coastal environments (including estuaries) of São Paulo State (Brazil). For that, we integrated molecular techniques (mitochondrial DNA markers) and morphological analyses of adult specimens for an accurate and detailed identification. The DNA markers were used when the morphological identification was doubtful, particularly in the recognition of cryptic species. This second manuscript presents a checklist of the Alpheidae caridean shrimps from the coast of São Paulo. We report the occurrence of Alpheus cf. paracrinitus and Synalpheus townsendi for the first time in the region. Based on our survey, 39 species of Alpheidae are known for this region: Alpheus (21 spp.), Athanas (2 spp.), Automate (2 spp.), Leptalpheus (1 spp.), Salmoneus (3 spp.), and Synalpheus (10 spp.). We collected 28 species and obtained cytochrome oxidase subunit I (barcode region) and/or 16S partial sequences of 26 of them. These sequences may be used for phylogenetic and populational analyses in further studies.

Checklist of decapods (Crustacea) from the coast of the São Paulo state (Brazil) supported by integrative molecular and morphological data: I. Infraorder Caridea: families Hippolytidae, Lysmatidae, Ogyrididae, Processidae and Thoridae.

The current checklist is the result of a long-term multidisciplinary project which combined molecular techniques (mitochondrial DNA markers) and morphological analyses of adult specimens for an accurate and detailed identification of the total biodiversity of decapod crustaceans from marine and coastal (including estuaries) environments of São Paulo State (Brazil). This is the first of a series of reports and providing a checklist of caridean shrimps of the families Hippolytidae (5 spp.), Lysmatidae (6 spp.), Ogyrididae (2 spp.), Processidae (5 spp.) and Thoridae (1 sp.). We collected material of 13 species out of 19 recorded, with sequences of cytochrome oxidase subunit I - barcode region and 16S generated from 10 species. The previous record of Lysmata cf. intermedia for São Paulo is actually L. jundalini, as the first record in São Paulo/South Atlantic waters. The molecular data were helpful to confirm the identification of some species, as the occurrence of L. wurdemanni which is confirmed in the South Atlantic Ocean based on morphological, color pattern and molecular data.

Ultrastructure of spermatozoa of spider crabs, family Mithracidae (Crustacea, Decapoda, Brachyura): Integrative analyses based on morphological and molecular data.

Recent studies based on morphological and molecular data provide a new perspective concerning taxonomic aspects of the brachyuran family Mithracidae. These studies proposed a series of nominal changes and indicated that the family is actually represented by a different number and representatives of genera than previously thought. Here, we provide a comparative description of the ultrastructure of spermatozoa and spermatophores of some species of Mithracidae in a phylogenetic context. The ultrastructure of the spermatozoa and spermatophore was observed by scanning and transmission electron microscopy. The most informative morphological characters analysed were thickness of the operculum, shape of the perforatorial chamber and shape and thickness of the inner acrosomal zone. As a framework, we used a topology based on a phylogenetic analysis using mitochondrial data obtained here and from previous studies. Our results indicate that closely related species share a series of morphological characteristics of the spermatozoa. A thick operculum, for example, is a feature observed in species of the genera Amphithrax, Teleophrys, and Omalacantha in contrast to the slender operculum observed in Mithraculus and Mithrax. Amphithrax and Teleophrys have a rhomboid perforatorial chamber, while Mithraculus, Mithrax, and Omalacantha show a wider, deltoid morphology. Furthermore, our results are in agreement with recently proposed taxonomic changes including the separation of the genera Mithrax (previously Damithrax), Amphithrax (previously Mithrax) and Mithraculus, and the synonymy of Mithrax caribbaeus with Mithrax hispidus. Overall, the spermiotaxonomy of these species of Mithracidae represent a novel set of data that corroborates the most recent taxonomic revision of the family and can be used in future taxonomic and phylogenetic studies within this family.

Biological associations of color variation in the Indo-Pacific swimming crab Charybdis hellerii.

A marine biological invasion is a natural process accelerated by human activities, and the crab Charybdis hellerii is an example of a globally widespread invasive species. This study evaluated color variation in C. hellerii and its relationship to the sex, size and sexual maturity of these crabs, and compared the efficiency of a freeware digital image-editing program with a commercially available program. The color of the individuals was analyzed using standardized digital images. The color pattern varied significantly with size; smaller and immature individuals were darker than larger and mature ones. The female abdomen changed in morphology and color with sexual maturity, becoming wider and orange-colored. There was no statistical difference in the color values between males and females and immature males did not show morphological or color differences in their abdomen. This study highlights the possible relationships of the color and physiological state of the reproductive system, which could help in future studies of behavior, avoiding the need to dissect and/or remove individuals from nature for assessment of sexual maturity. The freeware program showed the same efficiency in digital image analysis as a widely known commercial program.

Disulfide biochemistry in 2-cys peroxiredoxin: requirement of Glu50 and Arg146 for the reduction of yeast Tsa1 by thioredoxin.

2-Cys peroxiredoxin (Prx) enzymes are ubiquitously distributed peroxidases that make use of a peroxidatic cysteine (Cys(P)) to decompose hydroperoxides. A disulfide bond is generated as a consequence of the partial unfolding of the α-helix that contains Cys(P). Therefore, during its catalytic cycle, 2-Cys Prx alternates between two states, locally unfolded and fully folded. Tsa1 (thiol-specific antioxidant protein 1 from yeast) is by far the most abundant Cys-based peroxidase in Saccharomyces cerevisiae. In this work, we present the crystallographic structure at 2.8Å resolution of Tsa1(C47S) in the decameric form [(α(2))(5)] with a DTT molecule bound to the active site, representing one of the few available reports of a 2-Cys Prx (AhpC-Prx1 subfamily) (AhpC, alkyl hydroperoxide reductase subunit C) structure that incorporates a ligand. The analysis of the Tsa1(C47S) structure indicated that Glu50 and Arg146 participate in the stabilization of the Cys(P) α-helix. As a consequence, we raised the hypothesis that Glu50 and Arg146 might be relevant to the Cys(P) reactivity. Therefore, Tsa1(E50A) and Tsa1(R146Q) mutants were generated and were still able to decompose hydrogen peroxide, presenting a second-order rate constant in the range of 10(6)M(-1)s(-1). Remarkably, although Tsa1(E50A) and Tsa1(R146Q) were efficiently reduced by the low-molecular-weight reductant DTT, these mutants displayed only marginal thioredoxin (Trx)-dependent peroxidase activity, indicating that Glu50 and Arg146 are important for the Tsa1-Trx interaction. These results may impact the comprehension of downstream events of signaling pathways that are triggered by the oxidation of critical Cys residues, such as Trx.

Interaction between breeding habitat and elevation affects prevalence but not infection intensity of Batrachochytrium dendrobatidis in Brazilian anuran assemblages.

Chytridiomycosis, an infectious disease of amphibians, is caused by the fungus Batrachochytrium dendrobatidis (Bd) and has been linked to declining amphibian populations worldwide. The susceptibility of amphibians to chytridiomycosis-induced population declines is potentially influenced by many factors, including environmental characteristics, differences among host species and the growth of the pathogen itself. We investigated the effects of elevation and breeding habitat on Bd prevalence and individual infection intensity (zoospore loads) in 3 anuran assemblages of the Atlantic Coastal Forest of Brazil. Bd infection intensity was strongly influenced by elevation and breeding habitat, but we found no evidence of an interaction between those 2 variables in explaining the number of zoospores sampled from individual frogs. In contrast, Bd infection odds were predicted by elevation and by an interaction between elevation and breeding habitat, such that frogs had a higher probability of Bd infection in lotic habitats at low elevations. Our results indicate that Bd persists across a wide variety of habitats and elevations in the Atlantic Coastal Forest. Prevalence and infection intensity of Bd are highest at high elevations where overall environmental conditions for Bd are most favorable. In addition, at low elevations amphibian host habitat choice is also an important determinant of infection. Our study highlights the need to investigate interacting variables of host ecology and the environment simultaneously.

Toxin jararhagin in low doses induces interstitial edema and increases the metabolic rate and red blood cells in mice.

Jararhagin is a metalloproteinase from Bothrops jararaca responsible for hemorrhage, inflammation, necrosis and edema. Effects of low doses of the toxin were analyzed on the energy metabolism of mice as well as its physiological implications. Measures of O(2) consumption (VO(2)) were quantified after 4 and 24h of the jararhagin administration during four weeks. Hematocrit and histology of the lungs were also analyzed after the end of the treatment. Results showed that animals that received subcutaneous doses of jararhagin had significant increase in VO(2) from second (120 ng) and third weeks (60 ng) after 4 and 24h, comparing to control, as well as in the number of erythrocytes after four weeks. Histology of the lungs showed interstitial edema within the alveolar septum. Results suggest that the jararhagin toxin caused an increase in VO(2) and edema of intra-alveolar septum. The increase of the erythrocytes could be a physiological response to adjust the higher necessity of oxygen, due to diffusional abnormalities caused by the edema. Thus, low doses of jararhagin promote endothelial edema which lead to changes in several physiological conditions.