Sea snakes can dive deeply


This 2014 video says about itself:

In this exciting adventure, Jonathan travels to Manuk, a tiny, uninhabited volcanic island several hundred miles from the nearest populated island in Indonesia, on a mission to discover why the waters of this remote place are teeming with thousands of venomous sea snakes!

From the University of Adelaide in Australia:

Sea snakes make record-setting deep dives

April 2, 2019

Sea snakes, best known from shallow tropical waters, have been recorded swimming at 250 metres in the deep-sea ‘twilight zone‘, smashing the previous diving record of 133 metres held by sea snakes.

Footage of a sea snake swimming at 245 metres deep, and another sea snake at 239 metres has been provided to University of Adelaide researchers by INPEX Australia, an exploration and production company operating in the Browse Basin off the Kimberley coast of Australia. Both snakes appeared to belong to the same species.

Sea snakes are found in tropical waters of the Indian and Pacific Oceans and are typically associated with shallow water habitats like coral reefs and river estuaries.

“Sea snakes were thought to only dive between a maximum of 50 to 100 metres because they need to regularly swim to the sea surface to breathe air, so we were very surprised to find them so deep”, says Dr Jenna Crowe-Riddell, lead author of the study and recent PhD graduate at the University of Adelaide’s School of Biological Sciences.

Oceanic depths between 200 and 1000 metres encompass the mesopelagic zone, sometimes called the ‘twilight zone’ because only a small amount of light reaches that depth.

“We have known for a long time that sea snakes can cope with diving sickness known as ‘the bends’ using gas exchange through their skin,” says Dr Crowe-Riddell. “But I never suspected that this ability allows sea snakes to dive to deep-sea habitats.”

These record-setting dives raise new questions about the ecology and biology of sea snakes.

“In some of the footage the snake is looking for food by poking its head into burrows in the sandy sea floor, but we don’t know what type of fish they’re eating or how they sense them in the dark,” she says.

The snakes were filmed in 2014 and 2017 using a remotely operated vehicle or ‘ROV’ undertaking work for the INPEX-operated Ichthys LNG Project. …

Published in the journal Austral Ecology, the study is a collaboration between the University of Adelaide, the INPEX-operated Ichthys LNG Project, James Cook University in Australia, and The Royal Danish Academy of Fine Arts (KADK) in Denmark.

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Kangaroo rats against rattlesnakes


This 26 March 2019 video says about itself:

Kangaroo rat defensive kicking of rattlesnake while jumping

High speed recording of a desert kangaroo rat (Dipodomys deserti) defensively kicking away a sidewinder rattlesnake (Crotalus cerastes) in mid-air. The animals are free-ranging in their natural desert habitat at night, and filmed with high speed cameras using near-IR lights invisible to both species. The video is recorded at 500 frames per second, and playback is slowed down about 30 times. This clip shows the ability of kangaroo rats to avoid venom injection even when bitten by using a forceful mid-air kick to dislodge the snake and push it away. Scientific details of this study are published in Freymiller et al (2019, doi 10.1093/biolinnean/blz027). Find more information and additional bonus videos here.

See also here.

African sideways striking snake discovered


This 2008 video says about itself:

This is footage of a stiletto snake (Atractaspis microlepidota) striking and then eating a fuzzy mouse. These snakes are frequently confused with nonvenomous snakes and have caused bites to herpetologists who accidentally (or intentionally) pick them up.

From ScienceDaily:

New species of stiletto snake capable of sideways strikes discovered in West Africa

March 11, 2019

Summary: During surveys in the Upper Guinea forest zone of Liberia and Guinea, scientists discovered snakes later identified as a new to science species. It belongs to the stiletto snakes, spectacular for their unusual skulls, allowing them to stab sideways with a fang sticking out of the corner of their mouths. The discovery is further evidence supporting the status of the region as unique in its biodiversity.

Following a series of recent surveys in north-western Liberia and south-eastern Guinea, an international team of researchers found three stiletto snakes which were later identified as a species previously unknown to science.

The discovery, published in the open-access journal Zoosystematics and Evolution by the team of Dr Mark-Oliver Roedel from the Natural History Museum, Berlin, provides further evidence for the status of the western part of the Upper Guinea forest zone as a center of rich and endemic biodiversity.

Curiously, stiletto snakes have unusual skulls and venom delivery system, allowing them to attack and stab sideways with a fang sticking out of the corner of their mouths. While most of these burrowing snakes are not venomous enough to kill a human — even though some are able to inflict serious tissue necrosis — this behaviour makes them impossible to handle using the standard approach of holding them with fingers behind the head. In fact, they can even stab with their mouths closed.

The new species, called Atractaspis branchi or Branch’s Stiletto Snake, was named to honor to the recently deceased South African herpetologist Prof. William Roy (Bill) Branch, a world leading expert on African reptiles.

The new species lives in primary rainforest and rainforest edges in the western part of the Upper Guinea forests. Branch’s Stiletto Snake is most likely endemic to this area, a threatened biogeographic region already known for its unique and diverse fauna.

The first specimen of the new species was collected at night from a steep bank of a small rocky creek in a lowland evergreen rainforest in Liberia. Upon picking it up, the snake tried to hide its head under body loops, bending it at an almost right angle, so that its fangs were partly visible on the sides. Then, it repeatedly stroke. It is also reported to have jumped distances almost as long as its entire body. The other two specimens used for the description of the species were collected from banana, manioc and coffee plantations in south-eastern Guinea, about 27 km apart.

“The discovery of a new and presumably endemic species of fossorial snake from the western Upper Guinea forests thus is not very surprising,” conclude the researchers. “However, further surveys are needed to resolve the range of the new snake species, and to gather more information about its ecological needs and biological properties.”

Ecopassages save Canadian rattlesnakes’ lives


This 20 February 2019 video from Canada says about itself:

The Clever Idea That’s Reducing Rattlesnake Casualties

Ecopassages, which help snakes cross roads safely, have helped dramatically limit the number of snakes killed in Ontario. Here’s how they work.

How sea snakes avoid predators


This 2015 video says about itself:

Many people don’t realize that there are snakes that live in the ocean. And believe it or not, they’re actually considerably more venomous than land snakes! Jonathan travels to Australia and the Philippines to find these marine reptiles, and learns why they are almost completely harmless to divers.

From the University of Adelaide in Australia:

‘Seeing’ tails help sea snakes avoid predators

February 15, 2019

New research has revealed the fascinating adaptation of some Australian sea snakes that helps protect their vulnerable paddle-shaped tails from predators.

An international study led by the University of Adelaide shows that several species of Australian sea snakes can sense light on their tail skin, prompting them to withdraw their tails under shelter. The study has also produced new insights into the evolution and genetics of this rare light sense.

The researchers found that olive sea snakes (Aipysurus laevis) and other Aipysurus species move their tail away from light. They believe this is an adaptation to keep the tail hidden from sharks and other predators.

“Sea snakes live their entire lives at sea, swimming with paddle-shaped tails and resting at times during the day under coral or rocky overhangs,” says study lead author Jenna Crowe-Riddell, PhD candidate in the University of Adelaide’s School of Biological Sciences. “Because sea snakes have long bodies, the tail-paddle is a large distance from the head, so benefits from having a light-sense ability of its own.

“The olive sea snake was the only reptile, out of more than 10,000 reptile species, that was known to respond to light on the skin in this way.”

The researchers tested for light-sensitive tails in eight species of sea snakes, but found that only three species had the light-sense ability. They concluded the unique ability probably evolved in the ancestor of just six closely related Australian species.

“There are more than 60 species of sea snake so that’s less than 10% of all sea snakes,” says Ms Crowe-Riddell. “We don’t know why this rare sense has evolved in just a few Aipysurus species.”

The researchers used RNA sequencing to see what genes are active in the skin of sea snakes. They discovered a gene for a light-sensitive protein called melanopsin, and several genes that are involved in converting light into information in the nervous system.

“Melanopsin is used in a range of genetic pathways that are linked to sensing overall light levels around us. It is even used by some animals, including humans, for regulating sleep cycles and in frogs to change their skin colour as a camouflage,” says Ms Crowe-Riddell.

Lead scientist Dr Kate Sanders, ARC Future Fellow at the University of Adelaide, says: “We’ve confirmed the ability of olive sea snakes to sense light in their tails and found the same ability in two other species. We’ve identified a shortlist of genes that are likely to be involved in detecting light. But further study will be needed to target these genes before we can really understand the genetic pathways involved in this fascinating behaviour.”

Sea snakes don’t drink seawater


This 2014 video says about itself:

In this exciting adventure, Jonathan travels to Manuk, a tiny, uninhabited volcanic island several hundred miles from the nearest populated island in Indonesia, on a mission to discover why the waters of this remote place are teeming with thousands of venomous sea snakes!

And if you love sea snakes, check out our adventure with sea snakes in Australia:

From the University of Florida in the USA:

Sea snakes that can’t drink seawater

Zoology researchers solve mystery of how sea snakes quench their thirst

February 8, 2019

Summary: New research shows that pelagic sea snakes quench their thirst by drinking freshwater that collects on the surface of the ocean after heavy rainfall.

Surrounded by salty water, sea snakes sometimes live a thirsty existence. Previously, scientists thought that they were able to drink seawater, but recent research has shown that they need to access freshwater. A new study published in PLOS ONE on Feb. 7 and led by Harvey Lillywhite, professor of biology of the University of Florida, shows that sea snakes living where there is drought relieve their dehydration as soon as the wet season hits, and do so by obtaining freshwater from “lenses” that form on the surface of the ocean during heavy rain — events in which the salinity at the surface decreases enough for the water to be drinkable.

The yellow-bellied sea snake (Hydrophis platurus) is the only reptile in the order Squamata that lives on the open sea. It has one of the largest geographic ranges of any vertebrate species. Given its broad range and seafaring existence, during the dry season (6-7 months at the study site in Costa Rica) it has no access to freshwater. How they survive in regions of drought seems to hinge upon access to freshwater lenses, but little is known about how marine vertebrates react to or consume rainfall. “This study contributes to a fuller understanding of how pelagic sea snakes, and possibly other marine animals, avoid desiccation following seasonal drought at sea,” said Lillywhite.

The researchers captured 99 sea snakes off the coast of Costa Rica (interestingly, the snakes have never been observed in estuaries) and offered them freshwater in a laboratory environment. The team happened to be there just as six months of drought broke and the rainy season began. They found that only 13 percent of snakes captured after the rainfall began accepted the offer, compared to 80 percent of those captured before. The rainfall must have quenched their thirst.

The study continues many years of work by Lillywhite. The present paper was coauthored by Mark Sandfoss, Lillywhite’s current PhD student, Coleman Sheehy, his former student who is now the Collections Manager in Herpetology at the Florida Museum of Natural History, and then-Fulbright visiting scholar Jenna Crowe-Riddell.

“How these animals locate and harvest precipitation is important in view of the recent declines and extinctions of some species of sea snakes,” said Lillywhite. The question remains: How will climate change and its effects on precipitation impact the sea snakes?

How snakes lost their limbs


This February 2018 video says about itself:

90 million years ago, an ancient snake known as Najash had…legs. It is by no means the only snake to have limbs either. But what’s even stranger: we’re not at all sure where it came from.

From the Fundação de Amparo à Pesquisa do Estado de São Paulo in Brazil:

Research explains how snakes lost their limbs

The study is part of an effort to understand how changes in the genome lead to changes in phenotypes

February 6, 2019

Snakes and lizards are reptiles that belong to the order Squamata. They share several traits but differ in one obvious respect: snakes do not have limbs. The two suborders diverged more than 100 million years ago.

Identification of the genetic factors involved in this loss of limbs is a focus of the article “Phenotype loss is associated with widespread divergence of the gene regulatory landscape in evolution” published by Juliana Gusson Roscito and collaborators in Nature Communications.

Another equally interesting focus of the article is eye degeneration in certain subterranean mammals.

“We investigated these two cases in order to understand a much more general process, which is how genome changes during evolution lead to phenotype changes,” Roscito told.

Currently working as a researcher at the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden, Germany, Roscito has been a postdoctoral fellow in Brazil and a research intern abroad with São Paulo Research Foundation — FAPESP’s support. Her postdoctoral scholarship was linked to the Thematic Project “Comparative phylogeography, phylogeny, paleoclimate modeling and taxonomy of neotropical reptiles and amphibians,” for which Miguel Trefaut Urbano Rodrigues is the principal investigator under the aegis of the FAPESP Research Program on Biodiversity Characterization, Conservation, Restoration and Sustainable Use (BIOTA-FAPESP).

Rodrigues is a Full Professor at the University of São Paulo’s Bioscience Institute (IB-USP) in Brazil and supervised Roscito’s postdoctoral research. He is also a coauthor of the recently published article.

“The research consisted of an investigation of the genomes of several species of vertebrates, including the identification of genomic regions that changed only in snakes or subterranean mammals, while remaining unchanged in other species that have not lost their limbs or have normal eyes,” Roscito said.

“In mammals with degenerated visual systems, we know several genes have been lost, such as those associated with the eye’s crystalline lens and with the retina’s photoreceptor cells. These genes underwent mutations during the evolutionary process. Eventually, they completely lost their functionality, meaning the capacity to encode proteins. But that’s not what happened to snakes, which haven’t lost the genes associated with limb formation. To be more precise, the study that sequenced the genome of a snake did detect the loss of one gene, but only one. Therefore, the approach we chose in our research consisted of investigating not the genes but the elements that regulate gene expression.”

Gene expression depends on regulatory elements for the information the gene contains to be transcribed into RNA (ribonucleic acid) and later translated into protein. This process is regulated by cis-regulatory elements (CREs), which are sequences of nucleotides in DNA (deoxyribonucleic acid) located near the genes they regulate. CREs control the spatiotemporal and quantitative patterns of gene expression.

“A regulatory element can activate or inhibit the expression of a gene in a certain part of the organism, such as the limbs, for example, while a different regulatory element can activate or inhibit the expression of the same gene in a different part, such as the head. If the gene is lost, it ceases to be expressed in both places and can often have a negative effect on the organism’s formation.

However, if only one of the regulatory elements is lost, expression may disappear in one part while being conserved in the other,” Roscito explained.

Tegu lizard

From a computational standpoint, CREs are not as easy to identify as genes. Genes have a characteristic syntax, with base pairs that show where the genes begin and end. This is not the case for CREs, so they have to be identified indirectly. This identification is normally based on the conservation of DNA sequences among many different species.

“To detect the divergence of specific sequences in snakes, it’s necessary to compare the genomes of snakes with the genomes of various reptiles and other vertebrates that have fully developed limbs. Genome sequences for reptiles with well-developed limbs are scarce, so we sequenced and assembled the genome of the fully limbed tegu lizard, Salvator merianae. This is the first species of the teiid lineage ever sequenced,” the authors said.

“Using the tegu genome as a reference, we created an alignment of the genomes of several species, including two snakes (boa and python), three other limbed reptiles (green anole lizard, dragon lizard and gecko), three birds, an alligator, three turtles, 14 mammals, a frog, and a coelacanth. This alignment of 29 genomes was used as the basis for all further analyses.”

The researchers identified more than 5,000 DNA regions that are considered candidate regulatory elements in several species. They then searched the large database using ingenious technical procedures that are described in detail in the article and obtained a set of CREs the mutation of which may have led to the disappearance of limbs in the ancestors of snakes.

“There are several studies concerning a well-known regulatory element that regulates a gene that, when modified, causes various defects in limbs. Snakes have mutations in this CRE. In a study published in 2016, the mouse CRE was replaced with the snake version, resulting in practically limbless descendants. This was a functional demonstration of a mechanism that may have led to limb loss in snakes. However, this CRE is only one of the regulatory elements for one of several genes that control limb formation,” Roscito said.

“Our study extended the set of CREs. We showed that several other regulatory elements responsible for regulating many genes have mutated in snakes. The signature is far more comprehensive. An entire signaling cascade is affected.”