Semi-aquatic Predator Research Articles

Barreirosuchus franciscoi, um novo Crocodylomorpha Trematochampsidae da Bacia Bauru, Brasil

A big semi-aquatic predator from the Bauru Basin, Adamantina Formation (Upper Cretaceous, Turonian-Santonian), in Brazil, was described in this study. The new trematochampsid presents several synapomorphies with the Itasuchus genus, and its autapomorphies are: presence of a groove in the region of the lachrymal-jugal suture; frontal with a cuneiform distal projection slightly inclined anteroposteriorly; the dorsal surface of the squamosal is not arched and a finger-like projection occurs in its posterior dorsal portion; basicranium almost vertical and only posteriorly exposed, the supraoccipital is not exposed dorsally; basioccipital wider than high; and the posterior border of the pterygoids towards the posterior margin of skull roof. These discoveries widen the knowledge about the cretacic Neosuchia and provide subsidies to paleoenvironments proposals to the Bauru Basin.

Acetaminophen as an oral toxicant for Nile monitor lizards (Varanus niloticus) and Burmese pythons (Python molurus bivittatus)

Context. Invasive species are a growing global problem. Biological invasions can result in numerous harmful impacts on local ecologies, and non-native herpetofauna are frequently ignored. Nile monitor lizards (Varanus niloticus) and Burmese pythons (Python molurus bivittatus, recently reassessed as Python bivittatus bivittatus), have become established in southern Florida. Both are large, semi-aquatic predators that pose serious threats to a variety of threatened and endangered species, as well as to the unique ecology of the area. Aims. Acetaminophen (CAS#103-90-2), a lethal oral toxicant for the invasive brown treesnake (Boiga irregularis) on Guam, was investigated as a possible toxicant in juvenile Burmese pythons and Nile monitors. Methods. Dead neonatal mouse (DNM) baits containing 0, 10, 20, or 40 mg acetaminophen were force-fed to Nile monitors, whereas DNM containing doses of 0, 20, 40, or 80 mg were freely consumed by Burmese pythons. Subjects were frequently observed post-treatment for general condition and position, with special attention paid to activity (if any), behaviour, respiration, bleeding, emesis, ataxia, and mortality. Key results. In Nile monitors, acetaminophen doses of 10, 20, or 40 mg resulted in 0, 50 and 100% mortality, respectively. In Burmese pythons, doses of 20, 40, or 80 mg resulted in 14.3, 85.7 and 100% mortality, respectively. No mortality was observed in control individuals of either species. A negative correlation between dosage (mg kg–1) and time-to-death was observed in both species. Dosages ranging from 522 to 2438 mg kg–1 and 263 to 703 mg kg–1 were uniformly lethal to monitors and pythons, respectively. Neither species exhibited signs of pain or discomfort following acetaminophen treatment. Conclusions. Acetaminophen is an effective toxicant in juvenile Nile monitors and Burmese pythons. Further investigation into acetaminophen toxicity in adults of these species is merited. Implications. Although further investigation into adult lethal dosages and strategies to optimise bait deployment while minimising secondary hazards is required, acetaminophen may have a role to play in the control of these invasive species in Florida.

Structure and Function of the Mouthparts and Salivary Gland Complex of the Giant Waterbug, <I>Belostoma lutarium</I> (Stål) (Hemiptera: Belostomatidae)

Belostoma lutarium (Stal) is semiaquatic predator common to vegetated ponds, lakes, and bayous throughout eastern North America. We used scanning electron microscopy and histological cross sections to show that the morphology of the feeding structures of B. lutarium agrees with the general hemipteran feeding plan. Slight deviations from the previously reported observations for other Nepomorpha include the structure of the triturating devices, feeding stylets, and the efferent salivary duct. Furthermore, interrupted feeding trials indicate that B. lutarium is able to feed on large prey for over 2 h and not deplete its supply of salivary enzymes. All three productive components of the salivary gland (main, lateral, and accessory glands) empty most of their salivary products during the first 2 h of feeding, and begin regenerating their secretions during the feeding process. Essentially, no latency period for saliva production exists in this species. The structure and function of the mouthparts and salivary gland are adapted for the predaceous feeding habits of Belostomatidae.

Neurology: an ancient sensory organ in crocodilians.

Crocodilians hunt at night, waiting half-submerged for land-bound prey to disturb the water surface. Here I show that crocodilians have specialized sensory organs on their faces that can detect small disruptions in the surface of the surrounding water, and which are linked to a dedicated, hypertrophied nerve system. Such 'dome' pressure receptors are also evident in fossils from the Jurassic period, indicating that these semi-aquatic predators solved the problem of combining armour with tactile sensitivity many millions of years ago.

The adaptive significance of endothermy and salt excretion amongst the earliest archosaurs

Evidence, amongst Triassic thecodonts, of energetic upright postures and advanced bipedalism (or the vestiges of such characteristics) reveals that both endothermic and ectothermic thecodonts were descended from warm-blooded archosaurs with rapid metabolisms. Arboreal and aquatic adaptations in bipedal iguanians, and in extinct thecodonts, suggest that the emergence of reptilian bipedal locomotion is related to an arboreal-aquatic existence. But endothermy-required obligatory bipedalism could not have arisen in fauna-poor freshwater environments. The possible existence, in faunivorous thecodonts, of functional (or vestigial) cranial salt glands may suggest that the earliest semiaquatic archosaurs originated in fauna-prolific marine environments. If archosaurs were originally semiaquatic (marine) predators, then the existence of archosaurian endothermy could have initially emerged as an adaptation to increase metabolic heat production under the enhanced thermal cold stresses of the marine hydrosphere, while concurrently augmenting the rate of metabolic water production within saltwater environments inherently lacking in palatable freshwater resources.