Mercury biomagnification in the food web of Agami Pond, Kaw-Roura Nature Reserve, French Guiana.

Freshwater ecosystems are among the most important ecosystems worldwide, however, over the last centuries, anthropogenic pressures have had catastrophic effects on them. Mercury (Hg) is one of the main environmental contaminants which globally affect ecosystems and particularly freshwater wildlife. While Hg originates from natural sources, anthropogenic activities such as agriculture, biomass combustion, and gold mining increase its concentrations. Gold mining activities are the main drivers of Hg emission in tropical ecosystems and are responsible for up to 38% of global emissions. Once in its methylated form (MeHg), mercury biomagnifies through the trophic chain and accumulates in top predators. Due to the toxicity of MeHg, long-lived predators are even more subjected to chronic effects as they accumulate Hg over time. In the present study we quantified Hg contamination in two top predators, the Black caiman Melanosuchus niger and the Agami heron Agamia agami, and in their prey in the Kaw-Roura Nature Reserve in French Guiana and evaluated the biomagnification rate in the trophic chain. Our results show that despite a TMF in the range of others in the region (4.38 in our study), top predators of the ecosystem present elevated concentrations of Hg. We have found elevated Hg concentrations in the blood of adult Black caiman (2.10 ± 0.652 µg g-1 dw) and chicks of Agami heron (1.089 ± 0.406 µg g-1 dw). These findings highlight the need to better evaluate the potential impact of Hg in freshwater top predators, especially regarding reprotoxic effects.

Ontogeny of the Postcranial Axial Skeleton of Melanosuchus niger (Crocodylia, Alligatoridae).

This study proposes the description of the development of the postcranial axial skeleton, including vertebrae, gastralium, ribs, sternum, and interclavicle, in Melanosuchus niger. Six nests were marked and two eggs removed from each nest at 24-hr intervals until hatching. For posthatching evaluation, 30 hatchlings were kept in captivity and one exemplar was euthanized at three-day intervals. Samples were diaphanized using potassium hydroxide (KOH), alizarin red S, and Alcian blue. A routinely generally used method was applied for histological evaluation. It was difficult to define in which vertebrae the development of cartilaginous centers began, but it was possible to observe that this condensation advanced in the craniocaudal direction. The condensation started in the vertebral arches and was visibly stronger in the cervical and dorsal regions, advancing to the lumbar, sacral and, last, to the caudal region. The atlas showed a highly different morphology compared with the other cervical vertebrae, with a short intercenter, two neural arches, and a proatlas. The ossification process began in the body of cervical vertebrae III to VIII and alizarin retention decreased in the last vertebrae, indicating a craniocaudal direction in bone development, similar to cartilage formation. In the histological sections of gastralium and interclavicles of M. niger at several development stages, it was possible to observe that these elements showed intramembranous development. Anat Rec, 301:607-623, 2018. © 2017 Wiley Periodicals, Inc.

Ontogeny of the Appendicular Skeleton in Melanosuchus niger (Crocodylia: Alligatoridae).

The objective of the present study was to analyze chondrogenesis and the ossification pattern of the limbs of Melanosuchus niger in order to contribute with possible discussions on homology and the fusion pattern of autopodial elements and phylogeny. In the Reserva Extrativista do Lago Cuniã, Rondônia, Brazil, six nests were marked and two eggs removed from each nest at 24-hour intervals until hatching. Embryos were cleared using KOH; bone tissue was stained with alizarin red S and cartilage with Alcian blue. Routine staining with HE was also performed. In the pectoral girdle, the scapula showed ossification centers before the coracoid process. In the pelvic girdle, the ilium and the ischium were condensed as a single cartilage, although ossification took place through two separate centers, forming distinct elements in the adult. The pubis developed from an independent cartilaginous center with free end, which reflects its function in breathing. In the initial stages, the stylopodium and the zeugopodium developed from the condensation of a Y-shaped cartilage in the limbs, and differentiation of the primary axis and digital arch were observed. The greatest changes were observed in the mesopodia. In their evolution, Crocodylia underwent a vast reduction in the number of autopodial elements as a consequence of fusions and ossification of some elements. This study shows that the chondrogenesis and ossification sequences are dissociated. Moreover, the differences between M. niger and other species show clear variation in the patterns for these events in Alligatoridae.

Lesões pulmonares associadas ao parasitismo por Sebekia oxycephala (Pentastomida) em jacarés-açu (Melanosuchus niger Spix, 1825) oriundos de vida livre na Amazônia brasileira / Pulmonary lesions associated with parasitism by Sebekia oxycephala (Pentastomida) in free-ranging Black caimans (Melanosuchus niger Spix, 1825) from the Brazilian Amazon

O presente estudo objetivou descrever as lesões pulmonares macro e microscópicas associadas ao parasitismo por Sebekia oxycephala em 100 espécimes de jacarés-açu (Melanosuchusniger), abatidos na Reserva de Desenvolvimento Sustentável Mamirauá, situada no Estado do Amazonas, Brasil. Durante a avaliação macroscópica, exemplares dos parasitos encontrados no tecido pulmonar foram coletados individualmente em AFA (Álcool etílico - Formalina - Ácido acético glacial) e formol a 5% para avaliação parasitológica e classificação taxonômica. Amostras de tecido pulmonar de todos os animais, independentemente da ocorrência de lesões macroscópicas, foram fixadas em formol 10% e incluídas em parafina. Secções histológicas coradas por Hematoxilina-Eosina destas amostras foram avaliadas por meio de microscopia óptica. Macroscopicamente, 4 dos 100 animais (4%) apresentaram espécimes de pentastomídeos no parênquima pulmonar. Os parasitos foram classificados taxonomicamente como pertencentes à espécie Sebekia oxycephala. Nenhuma alteração macroscópicas foi observada, porém, microscopicamente, lesões pulmonares foram encontradas em 37% dos casos, sendo que, lesões inflamatórias associadas ao parasitismo corresponderam a 75,6% dos mesmos (28/37). Nestes, segmentos degenerados e ovos de S. oxycephala encontravam-se envolvidos por cápsula de tecido conjuntivo fibroso e infiltrado inflamatório predominantemente composto por células gigantes do tipo corpo estranho. Três espécimes apresentaram espessamento de septos alveolares e sete exemplares continham infiltrado inflamatório granulocítico multifocal no parênquima pulmonar. As lesões associadas ao parasitismo, de modo geral, apresentaram intensidade discreta e parecem não representar uma causa importante de doença pulmonar entre a população estudada. Esta é a primeira descrição de lesões pulmonares em M. niger associadas ao parasitismo por S. oxycephala na Amazônia brasileira.

The goal of this study was to describe gross and microscopic lung lesions associated with the parasitism by Sebekia oxycephala between 100 specimens of black caiman (Melanosuchus niger) slaughtered in the Mamirauá Sustainable Development Reserve, situated in the Amazonas State, Brazil. During the macroscopic evaluation, specimens of parasites found in the lung tissue were collected individually in AFA (ethyl alcohol - formalin - glacial acetic acid) and 5% formalin for parasitological evaluation and taxonomic classification. Lung tissue samples of all the animals, regardless of the occurrence of gross lesions, were fixed in 10% formalin and embedded in paraffin. Histological sections obtained from the samples stained by Hematoxylin-Eosin were evaluated by light microscopy. Grossly, 4 of the 100 animals (4%) presented pentastomid specimens in the lung parenchyma. These parasites were taxonomically classified as Sebekia oxycephala. No macroscopic alterations were observed, however microscopically pulmonary lesions were found in 37% of the cases, and inflammatory lesions associated with the parasitism corresponded to 75.6% of them (28/37). In these cases, degenerate segments and eggs of S. oxycephala were surrounded by a fibrous capsule and inflammatory infiltrate composed predominantly by foreign body giant cells. Three specimens exhibited thickening of the alveolar septa and seven specimens presented multifocal inflammatory granulocytic infiltration in the lung parenchyma. Generally, the associated parasitic lesions had mild intensity and did not appear to represent an important cause of lung disease in the studied population. This is the first description of lung lesions in M. niger associated with parasitism by S. oxycephala in the Brazilian Amazon.

Aggressive keloid-mimicking tumor in Melanosuchus niger in captivity / Queloide agressivo imitando tumor em Melanosuchus niger em cativeiro

The objective of this note is to describe a case of exuberant scarring formation, with keloid characteristics and pseudo-tumoral configuration in a male Black caiman (Melanosuchus niger), with an estimated age of 60 years, belonging to the Zoobotanical Park at the Emílio Goeldi Museum, located in Belém, Pará, Brazil. The alteration appeared on the right posterior limb involving two distal phalanges of the lateral digit and measured 12.4cm at the greatest width. The keloid tissue was surgically removed and samples were processed and analyzed histopathologically, revealing growth made up of fibrous connective tissue with the habitual morphology, which was structurally mature in the more central areas.

O objetivo do presente relato é descrever um caso de formação cicatricial exuberante, característica de queloide e configuração pseudo-tumoral em um jacaré-açu (Melanosuchus niger), macho, com idade estimada de 60 anos, pertencente ao Parque Zoobotânico do Museu Emílio Goeldi, situado em Belém, Pará, Brasil. A alteração manifestou-se no membro posterior direito, envolvendo as duas falanges distais do dedo lateral e mediu 12,4cm na maior largura. A neoformação foi removida cirurgicamente e amostras foram processadas e analisadas por histopatologia, que revelou crescimento constituído por tecido conjuntivo fibroso de morfologia habitual, estando estruturalmente maduro nas áreas mais centrais.

Description of embryonic stages in Melanosuchus niger(Spix, 1825) (Crocodylia: Alligatoridae)

The determination of embryonic stages is very useful in comparative and evolutionary anatomy, experimentalresearch and ecological studies. Although tables of development stages already exist for some crocodilianspecies, no table has yet been published for Melanosuchus niger. Therefore, the aim of this work is to monitorthe development of this species of Alligatoridae and characterize its stages based on the main morphologicaltransformations the embryo undergoes during the incubation process. Under natural conditions, two sampleswere collected daily in the Lake Cuniã Extractive Reserve in Rondônia, Brazil, making a total of 186 eggs.The incubation period was 90 days at an ambient temperature varying from 25.2 to 31.7 °C. We established24 embryonic stages between the formation of the pharyngeal arch and hatching. Primordia for the sensoryorgans and somites were observed in the early stages. The buds of the pelvic and thoracic limbs emergedsimultaneously, also in the early stages. An analysis of these structures showed evidence of considerableevolutionary modifications when compared with embryos of different species. In stage 12 we observed subtlepigmentation in the region of the head and, in stage 25, the pigmentation and striped pattern were typical ofthe newly hatched specimen. The eyetooth was visible in stage 18, disappearing within the first few weeks afterhatching. The vitellus was completely absorbed in the penultimate stage. Direct comparisons of the table ofembryonic stages were made between M. niger and other crocodilian taxa, and the main differences identifiedwere chronological variations.