Size of nesting female Broad-snouted Caimans (Caiman latirostris Daudin 1802) / Tamanho de fêmeas nidificantes do jacaré-de-papo-amarelo (Caiman latirostris Daudin 1802)

Abstract The southern distribution of the Broad-snouted Caiman (Caiman latirostris Daudin 1802) in Argentina occurs in Santa Fe Province, where its population has been under management by "Proyecto Yacaré" since 1990. From 1997 to 2016, we captured 77 nesting female Broad-snouted Caimans in Santa Fe Province. Our results suggest that previously defined size classes for Broad-snouted Caiman do not adequately describe the reproductively mature female segment of the population. Here we propose to change size ranges for general size classes for Broad-snouted Caiman. In addition, we have observed that reintroduced reproductive females by Proyecto Yacaré represent about 32% of captured females. These results indicate that reintroduced females by the management program are surviving and reproducing in the wild at least up to 20 years.

Resumo Na Argentina, a distribuição mais austral do jacaré-de-papo-amarelo (Caiman latirostris Daudin 1802) ocorre na Provincia de Santa Fe, sendo que suas populações são manejadas pelo "Proyecto Yacaré" desde 1990. Entre os anos de 1997 e 2016, nós capturamos 77 fêmeas nidificantes do jacaré-de-papo-amarelo em Santa Fe. Nossos resultados sugerem que as classes de tamanho definidas para o jacaré-de-papo-amarelo não representam a realidade dos animais capturados no presente estudo. Portanto, propõe-se uma alteração nas classes de tamanho para o jacaré-de-papo-amarelo. Nós também observamos que as fêmeas reintroduzidas pelo "Proyecto Yacaré" representaram 32% das fêmeas capturadas. Estes resultados indicam que fêmeas reintroduzidas pelo programa de manejo estão sobrevivendo e reproduzindo na natureza por, pelo menos, 20 anos.

Nesting of Morelet's crocodile, Crocodylus moreletii (Dumeril and Bibron), in Los Tuxtlas, Mexico / Nidificação de crocodilo do Morelet, Crocodylus moreletii (Dumeril e Bibron), em Los Tuxtlas, México

Abstract We evaluated the nesting by Crocodylus moreletii in Lago de Catemaco, Veracruz, southeastern, Mexico. During the nesting and hatching seasons, we searched for nests along the northern margins of the lake and small associated streams. We investigated egg mortality by weekly monitoring each of the nests found, recording sign of predation (tracks and holes dug into the nest) and the effect of water level fluctuations. We not found differences to nest between inland or flooded zones. However, we found that egg size varied among nests. In nests built inland, predation was the major cause of egg mortality whereas flooding resulted in more deaths of eggs in the flooding zone. Flooding killed 25% of eggs monitored in this study. We suggest that to increase nest success in the Morelet's crocodile it is necessary to promote conservation of nesting areas around the lake, recently occupied by urban or tourist developments.

Resumo Nós avaliamos a nidificação numa população de Crocodylus moreletii no Lago de Catemaco, Veracruz, sudeste, México. Durante as temporadas de nidificação e eclosão buscamos ninhos ao longo das margens situadas ao norte do lago e pequenos riachos associados. Estabelecemos a mortalidade de ovos por semana monitorando cada ninho achado, registrando qualquer sinal de predação (rastros e buracos cavados no ninho) e o efeito das flutuações no nível da agua. Não achamos nenhuma preferência para aninhar na terra ou em áreas inundadas. Por outro lado, achamos que o tamanho de ovo foi significativamente diferente entre os tipos de ninho. Em ninhos construídos na terra, a predação foi a principal causa da mortalidade de ovos enquanto que nas áreas inundadas, inundação foi um fator importante na morte dos ovos. Em comparação com depredação, a ruptura acidental e colonização fúngica, as inundações mataram 25% de ovos monitorados. Nós sugerimos que para aumentar o sucesso de aninhamento do crocodilo do Morelet é preciso promover a conservação das áreas de nidificação ao redor do lago, recentemente ocupadas pelo desenvolvimento urbano ou turístico.

Ecología de la anidación de Crocodylus acutus (Reptilia: Crocodylidae) en Bahía Portete, La Guajira, Colombia / Nesting ecology of Crocodylus acutus (Reptilia: Crocodylidae) in Bahia Portete, La Guajira, Colombia

ResumenEn Colombia, C. acutus se encuentra catalogada en peligro crítico. Durante julio 2007, agosto 2008, junio y agosto 2009 y entre marzo y agosto 2010 y 2011, la población en Bahía Portete fue estudiada para evaluar la anidación y obtener la información necesaria para el ajuste de un programa de manejo acorde con la biología de la especie. Este estudio asumió la vinculación de la comunidad indígena Wayuü para emplear el modelo de acuerdo de conservación. Se realizaron transectos en toda la costa de la bahía para la búsqueda de nidadas. En la determinación de las áreas de importancia para la anidación, se registraron las características biométricas de los nidos, la biometría de huevos y crías, la fertilidad de huevos y eventos reproductivos. Como resultado se recorrieron 55.12 km, se determinaron cuatro zonas de importancia para la anidación, la de mayor importancia fue la isla Juyui. En todas las áreas de anidación, variables como la anidación colonial o gregaria y las variables ambientales fueron factores que afectaron el éxito de eclosión. El 37 % de los nidos estuvieron orientados hacia el norte y el 48 % fueron construidos en cercanía de Stenocereus griseus. La isla Juyui presentó los mayores porcentaje de arena (71.9 %, 71.44 %). El promedio de huevos por nido fue 28.42 ± 6.63. Los huevos presentaron un diámetro mayor promedio de 71.84 ± 3.54 mm y peso 81.54 ± 9.99 g. Las crías presentaron un promedio de longitud total de 25.47 ± 1.16 cm. El período reproductivo para este sector de Colombia, se inicia en marzo y culmina en agosto. Las pocas áreas de anidación y la fertilidad del 95 % sugieren la ejecución de un programa conservación para C. acutus en Bahía Portete.

Abstract:C. acutus is cataloged in critical danger in Colombia. We studied its population at Bahia Portete, in order to survey the nesting activities and to obtain valuable information for a conservation management program. This study was undertaken with the participation of the Wayuü community using the Agreement Conservation Model, and took place during July 2007, August 2008, June and August 2009, and March to August 2010 and 2011. Sampling surveys were made by the use of transects along the coast, in order to find nests. For each nesting area found, we recorded the nests biometrics, eggs and hatchlings, fertility of the eggs and reproductive events. We explored a total of 55.12 km, and determined four nesting areas. Colonial nesting and the environmental variables were factors that affected the hatchling success. From the total of nests found, 37 % were oriented towards North, and 48 % were built next to Stenocereus griseus. Juyui island substrate was mostly constituted by sand (71.9 %, 71.44 %). The average number of eggs by nest was 28.42 ± 6.63, the largest egg diameter was 71.84 ± 3.54 mm, the average nest weight was 81.54 ± 9.99 g, and the hatchlings presented an average length of 25.47 ± 1.16 cm. For this specific site in Colombia, the reproductive period begins in March and ends in August. The few areas of nesting and the 95 % fertility suggest the performance of a conservation management program for this species at Bahía Portete. Rev. Biol. Trop. 65 (1): 211-228. Epub 2017 March 01.

Vocal patterns of adult females and juveniles Caiman yacare (Crocodilia: Alligatoridae) in Brazilian Pantanal wetland / Patrones de vocalización de jóvenes y hembras adultas de Caiman yacare (Crocodilia: Alligatoridae) en el Pantanal de Brasil

The Paraguayan caiman (Caiman yacare) is the main Caimaninae species occurring in the Brazilian Pantanal Wetland. Despite the relative availability of works focused on biology and conservation of the Paraguayan caiman, almost nothing is known about its vocal structure and behavior. We recorded aggressive calls of adult caiman females guarding nests and, afterwards, the distress calls of the new born juvenile caimans in seasonally flooded areas of the Nhecolândia (Southern Pantanal). The results of both observations and sonographic analyses diverged from studies with other crocodilian species. Aggressive vocalization of adult females of the Paraguayan caiman was longer and more complex than the same vocalization of larger Alligatoridae species. Vocalizations of the young caimans presented interspecific differences with other crocodilian offsprings. Moreover, we found statistically significant intraspecific variation in the distress call structure among different pods, even separated by few kilometers. Differences in distress call structure were tested by Canonical Discriminant Analysis (CDA). We obtained the squared Mahalanobis distances between the acoustic multivariate spaces of each pod provided by the CDA and compared with the geographic distance between the bays of origin of each pod through Mantel Test. The geographic distance by itself did not explain the differences found in the structure of the vocalization of young caimans from different pods. The adult females of Paraguayan caiman positively responded to playbacks of calls from juvenile caimans from pods of other regions, as well as to rough imitations of distress call. Since the adult caimans showed protective responses to quite heterogeneous vocalizations of distress by juveniles, we hypothesized that the variation in the distress call pattern may be associated to a low specificity in sound recognition by adult caimans.

Poco se conoce sobre la estructura vocal del Caiman yacare del Pantanal brasileño. Llamadas agresivas de hembras adultas que cuidaban de los nidos fueron registradas durante enero y febrero y llamadas de socorro de caimanes jóvenes, en abril de 1992. Hembras adultas de C. yacare presentaron una vocalización agresiva más larga y compleja que en otras especies más grandes de Alligatoridae. Las vocalizaciones de los jóvenes caimanes también presentaron diferencias interespecíficas con otros cocodrilos y variaciones intraespecíficas entre grupos separados por pocos kilómetros. Se utilizó la Prueba de Mantel para comparar las distancias de Mahalanobis entre la estructura de las vocalizaciones de los jóvenes de acuerdo con sus grupos y las distancias geográficas donde ellos estaban. La distancia geográfica en sí no explica las diferencias en las vocalizaciones de jóvenes de diferentes grupos. Hembras adultas de C. yacare han respondido a grabaciones de llamadas de caimanes de grupos de otras regiones, así como a imitaciones de llamada de socorro. Se postula que las variaciones en las llamadas de socorro pueden estar asociadas con una baja especificidad en el reconocimiento de sonido por caimanes adultos que han respondido de la misma forma protectora a las más heterogéneas expresiones de peligro de los jóvenes.

Skeletogenesis of the pectoral girdle and forelimbs in embryos of Caiman yacare (Daudin, 1802) (Crocodylia, Alligatoridae)

Embryos of Caiman yacare were collected and subjected to the bone clearing and staining protocol in orderto analyze the ontogenetic patterns of ossification of the pectoral girdle and forelimb skeleton. The osseousstructure of the girdle and forelimbs of C. yacare begins to ossify starting at 30 days of incubation, withthe presence of dye retention in the scapula, coracoids, humerus, radius and ulna bones. During embryonicdevelopment, the autopodio of C. yacare has four bones in the carpus, the radial, ulnar, pisiform and carpaldistal 4+5 bone. Their ossification begins at 39 days of incubation with the radial, followed by the ulnar, and at54 days, the pisiform and the distal carpal 4 + 5. Each mesopodio has 5 metacarpi and are present 15 phalanges,two in digits I and V, three in digits II and IV, and four in digit III (phalangeal formula 2:3:4:3:2). Ossificationof the metacarpi starts at 27 days of incubation, following the sequence MCII=MCIII=MCIV>MCI>MCV.The first phalanges begin the process of ossification on day 36, continuing up to the last day of incubation.The sequence of ossification of the proximal phalanges is PPI=PPII=PPIII>PPIV=PPV, that of the medialphalanges is MPII>MPpIII>MPdIII>MPIV, and that of the distal phalanges is DPI>DPII>DPIII>DPV>DPIV.The ontogenetic pattern of the bones of the forepaw of C. yacare generally differs from that of other reptiles,although there are some similarities.

A systematic study of the brain base arteries inbroad-snouted caiman (Caiman latirostris)

The objective of this study was to describe and systematize the encephalic arterial vascularization of this reptile,by providing a standard irrigation model with its major variations. Thirty broad-snouted caiman heads andtwo whole specimens were used. The arterial system was filled with red-colored latex. Only a single source ofblood supply was observed in caimans and it originated from the left aortic arch. This vessel is called the azygoscarotid artery. At the caudal base of the skull, ventral to the first cervical vertebrae, it divided into two internalcarotid arteries. The internal carotid arteries divided into a rostral branch and a short caudal branch at thehypophysis level, which continued naturally as the caudal cerebral artery. The short caudal branch gave off itsmedium-caliber portion which, gave off the mesencephalic and the ventral rostral cerebellar arteries. Then thiscaudal branch anastomosed with its contralateral counterpart, forming the basilar artery. This artery followedthe ventral median fissure of the medulla oblongata, giving off the ventral caudal cerebellar and dorsal spinalarteries, and abandoning the cranial cavity through the foramen magnum as the ventral spinal artery. Therostral branch gave off the middle cerebral, rostral cerebral and rostral communicating arteries. The middlecerebral artery arose from a network originated from one to five collateral branches of the rostral branch of theinternal carotid artery. It was observed that the cerebral arterial circle was rostrally and caudally closed and,therefore, the cerebral blood supply was exclusively made by the carotid system.

Distribution patterns, population status and conservation of Melanosuchus niger and Caiman yacare (Crocodylia, Alligatoridae) in oxbow lakes of the Ichilo river floodplain, Bolivia

Caiman yacare (lagarto) and Melanosuchus niger (black caiman), sympatric species in the Bolivian Amazon basin, have been severely overexploited in the past. We present the results of a standardized survey of C. yacare and M. niger populations in order to evaluate their actual population status in twelve oxbow lakes of the Ichilo River floodplain. Additionally we explored the effect of environmental and anthropogenic variables on caiman distribution patterns. The average density of C. yacare and M. niger in the shoreline of floodplain lakes was of 6 and 1 ind/km, respectively. For both species, the population was composed mainly of juvenile individuals. We used regression tree analysis (RTA) to assess patterns of M. niger and C. yacare densities with eight environmental and two anthropogenic variables. The RTA analysis showed that the variation in the densities of both C. yacare (52.4 %) and M. niger (36.8 %) was related to water conductivity. For C. yacare, higher densities occurred at higher values of water conductivity, while M. niger densities followed an opposite trend, resulting in relatively well spatially segregated populations of the two species. After excluding conductivity, Lake-River Distance (LRD) was shown to be the main splitting variable in the RTA analysis. The observed distribution patterns may be the result of the historical post-hunting situation, in combination with differences in habitat selection by the two species, and competitive exclusion processes between the two species. M. niger, a species reported to be recovering slowly from previous low population levels, appears relatively well protected in the Ichilo river floodplain. Rev. Biol. Trop. 56 (2): 909-929. Epub 2008 June 30.

Caiman yacare (lagarto) y Melanosuchus niger (caiman negro), son dos especies simpátricas para la cuenca amazónica Boliviana que han sido severamente sobreexlotadas en el pasado. El objetivo de la presente investigación es el de evaluar el estado actual de su población en doce lagunas meándricas de la planicie del río Ichilo. Se realizaron conteos nocturnos de ambas especies entre octubre y diciembre de 1999 y diciembre del año 2000. La perturbación antropogénica fue medida como el número de días por año por pescador que visitan las lagunas. El promedio de individuos observados en las orillas de las lagunas estudiadas fue de de 6 ind./km para C. yacare y de 1 ind./km para M. Níger. Para ambas especies la población estuvo compuesta mayormente por jóvenes. Los análisis de correspondencia canónica (CCA) separaron las lagunas que se encontraron cerca del río, dominadas por C. yacare, de las remotas, dominadas por M. níger. El "Análisis de Árboles de Regresión" (RTA por las siglas en inglés) de ocho variables ambientales y dos antropogénicas explicó un 52.4% de la variación de la densidad de C. yacare y un 36% de M. niger con la conductividad del agua. La alta conductividad coincidió con densidades mayores de C. yacare (lo opuesto para M. niger). Si se excluye la conductividad, la distancia de la laguna al río es el principal predictor. Factores históricos y humanos podrían estar jugando un papel importante en los patrones de distribución y abundancia de ambas especies en combinación con diferencias en la selección de habitats y/o procesos de competición exclusiva entre las dos especies. La especie M. niger se recupera muy lentamente de los bajos niveles de densidad poblacional previos y está protegida en lagunas alejadas del canal principal del Río.

Variabilidad espacio-temporal de las comunidades de plantas acuáticas en un humedal de los Llanos de Venezuela / Spatial-Temporal variability of aquatic plant communities in the Venezuelan Llanos

The richness and abundance of aquatic plant communities were studied in 14 habitats of the Venezuelan "llanos" (07 degrees 35'-07 degrees 55' N-68 degrees 50'-69 degrees 00' W, Apure) during an annual cycle. Annual means were 27 degrees C, 115 mm rainfall and 77% relative humidity. A permanent transect was set in each habitat (ten consecutive square meter quadrats from the shore to the water). The plants and the area they covered in each quadrat were recorded monthly for a year. The total richness was 69 species. Alatalo and Alatalo's diversity analysis indicates that season, and its correlate, water level, influence species diversity and abundance more than habitat (spatial factor: geometric index-Euclidean distance).

A fin de describir la variabilidad espacio temporal de las comunidades de plantas acuáticas en un humedal de los Llanos de Venezuela, se estudiaron su riqueza y abundancia, en 14 hábitat, durante un ciclo anual. En los transectos de estudio se identificó un total de 69 especies. Según el análisis de diversidad con interacción de Alatalo y Alatalo el aspecto temporal, es decir el régimen anual de lluvia-sequía y la consecuente variación del nivel del agua, es el factor que ejerce mayor influencia sobre la riqueza de especies, en relación al aspecto espacial, o tipo de hábitat. Según el índice geométrico de las distancias euclídeas, se concluye igualmente que la variación en la abundancia de especies se debe más a las fluctuaciones hidrométricas (estacionalidad) que al hábitat considerado.

Allometry of reproduction in broad-snouted caiman (Caiman latirostris)

In the present study regression equations are established between broad-snouted caiman (Caiman latirostris) captive reproductive females snout-vent length (SVL) and body mass (BM) and the following clutch characteristics: egg mass, egg "length" (maximal diameter), egg "width" (minimal diameter), hatchling BM, hatchling SVL, clutch size (number of eggs), clutch mass and relative clutch mass (clutch mass/female BM). Female body-length presented a positive correlation with egg mass, egg length, egg width, hatchling BM and hatchling SVL. No clear correlation was found between female SVL and clutch size. Female BM showed a significantly positive correlation with egg mass, egg-length, egg-width, hatchling BM, hatchling SVL and clutch mass. A highly significant negative correlation was found between female BM and the relative clutch mass. No clear correlation was found between female BM and clutch size

Observations on the thermal selection of the pantanal caiman (Caiman crocodilus yacare) hatchlings (Crocodylia: Alligatoridae)

Three options of water temperatures in a thermal gradient that changed from 22 to 35 C were offered to Pantanal caiman (Caiman croocodilus yacare) hatchlings. Animals from two nests were submitted to temperatures during 19 days (Nest 1 - 20 caimans caught in the nature hours after hatching), corresponding to 1 to 7 observations periods, and 13 days (Nest 2 - 20 animals obtained by artificial incubation) relative to observation period 8. Caimans remain fasting during experimental period. Hatchlings were allocated in a enclosure containing three styrofoam boxes (120 L) disposed side by side enclosed by wire netting and filled with water to the top. Thus, the animals were free to access the boxes, which temperatures were changed at the end of each observation period to avoid position effects. Air temperature was keep close to 22 C by air conditioning and water temperature was controlled by thermostats. The trial was divided in three phases determined by elimination of the less frequented temperature and its substitution by another temperature. In a first phase of the experiment that contained 1, 2 and 3 observation periods, the thermostats were regulated to 22 C (BoxD), 26 C (BxC) and 32 C (BxA). In phase 2 to 26 C, 29.5 C (BxB) and 32 C, including 4, 5 and 6 periods. In the third phase that included 7 and 8 periods, the thermostats were adjusted to 29.5 C, 32 C and 35 C (BxE). The number of caimans in each box was recorded two to three times a day (8:00, 14:00 and 17:00h) before pointed water temperature. Mean water temperatures (+ standard deviation) and respective caiman frequency means by box/temperature were: Phase 1 (BxD/22.3 1.2 C - 10.3 percent; BxC/27.0 2.4 C - 32.0 percent and BxA/31.2 1.1 C - 57.6 percent); Phase 2 (BxC/26.6 2.8 C - 13.3 percent; BxB/29.3 2.2 C - 27.7 percent and BxA/31.3 1.2 C - 59.0 percent) and Phase 3 (BxB/29.5 3.6 C - 23.7 percent; BxA/31.0 2.2 C - 31.9 and BxE/34.0 2.2 C - 44.4 percent). Observing that in the phases 1 and 2 the box with hottest water (CxA) was more frequented. In the phase 3, the difference between higher and smaller frequency straiten to 20.7 percent, in relation to almost 46.5 percent in phases 1 and 2, indicating that water temperatures between 29.5 and 35 C resulted in body temperatures more next to the comfort zone, in the experimental conditions

Neuropeptide control of the cardiovascular system in fish and reptiles

Accumulating evidence shows the involvement of neuropeptides in cardiovascular control in mammals as well as non-mammalian species. Our own immunohistochemical studies indicate a sparse innervation only in cyclostomes, holostean fish and lungfish, a more extensive variation and distribution in elasmobranchs and teleosts, and a rich and varied innervation of the cardiovascular system in crocodiles and lizards. Vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), gastrin releasing peptide (GRP) and tachykinins are present in most vertebrate groups. VIP is vasodilatory in the Atlantic cod (Gadus morhua) as in most mammalian species, but increases gut vascular resistance in the spiny dogfish (Squalus acanthias). NPY potentiates the effect of noradrenaline on skate (Raja rhina) coronary vessels, suggesting an interaction between adrenergic mechanisms and NPY early in evolution, but studies in the spiny dogfish and the crocodile also demonstrate different mechanisms for the action of NPY and adrenaline in some species. Bombesin/GRP increases flow to the gut in the spiny dogfish by an increase in somatic vascular resistance, while visceral resistance remains unchanged. In the caiman (Caiman crocodylus crocodylus) bombesin causes a shunting of blood from the lung to the gut. Substance P and other tachykinins in general increase flow to the gut, and on some occasions also increase somatic blood flow. Flow in the anastomosis of the crocodile (Crocodylus porosus) gut is increased by substance P. The results presented here are a review of several published and unpublished studies.