Hammerhead sharks, new research


This 2016 video from Mexico is called Face to face with huge smooth hammerhead in Cabo San Lucas.

From Nova Southeastern University in the USA:

New shark research targets a nearly endangered species

September 15, 2020

They are some of the most iconic and unique-looking creatures in our oceans. While some may think they look a bit “odd”, one thing researchers agree on is that little is known about hammerhead sharks. Many of the 10 hammerhead shark species are severely overfished worldwide for their fins and in need of urgent protection to prevent their extinction.

To learn more about a declining hammerhead species that is data-poor but in need of conservation efforts, a team of researchers from Nova Southeastern University’s (NSU) Save Our Seas Foundation Shark Research Center (SOSF SRC) and Guy Harvey Research Institute (GHRI), Fisher Finder Adventures, the University of Rhode Island and University of Oxford (UK), embarked on a study to determine the migration patterns of smooth hammerhead sharks (Sphyrna zygaena) in the western Atlantic Ocean. This shark, which can grow up to 14-feet (400 cm), remains one of the least understood of the large hammerhead species because of the difficulty in reliably finding smooth hammerheads to allow scientific study.

To learn about smooth hammerhead behavior, the research team satellite-tagged juvenile hammerhead sharks off the US Mid-Atlantic coast and then tracked the sharks for up to 15 months. The sharks were fitted with fin-mounted satellite tags that reported the sharks’ movements in near real-time via a satellite link to the researchers.

“Getting long-term tracks was instrumental in identifying not only clear seasonal travel patterns, but importantly, also the times and areas where the sharks were resident in between their migrations,” said Ryan Logan, Ph.D. student at NSU’s GHRI and SOSF SRC, and first author of the newly published research. “This study provides the first high resolution, long term view of the movement behaviors and habitats used by smooth hammerhead sharks — key information for targeting specific areas and times for management action to help build back this depleted species.”

The researchers found that the sharks acted like snowbirds, migrating between two seasonally resident areas — in coastal waters off New York in the Summer and off North Carolina in the Winter. Their residency times in these two locations coincided with two environmental factors: warmer surface water temperatures and areas with high productivity — indicative of food-rich areas.

“The high-resolution movements data showed these focused wintering and summering habitats off North Carolina and New York, respectively, to be prime ocean “real estate” for these sharks and therefore important areas to protect for the survival of these near endangered animals,” said Mahmood Shivji, Ph.D., director of NSU’s GHRI and SOSF SRC, who oversaw the study.

Identifying such areas of high residency provides targets for designation as “Essential Fish Habitat” — an official title established by the US Government, which if formally adopted can subsequently be subject to special limitations on fishing or development to protect such declining species.

The tracking data also revealed a second target for conservation. The hammerheads spent a lot of resident time in the winter in a management zone known as the Mid-Atlantic Shark Area (MASA) — a zone already federally closed for seven-months per year (January 1 to July 31) to commercial bottom longline fishing to protect another endangered species, the dusky shark. However, the tracking data showed that the smooth hammerheads arrived in the MASA earlier in December, while this zone is still open to fishing.

“Extending the closure of the MASA zone by just one month, starting on December 1 each year, could reduce the fishing mortality of juvenile smooth hammerheads even more,” said Shivji. “It’s particularly gratifying to see such basic research not only improving our understanding of animal behavior in nature but also illuminating pathways for recovery of species and populations that have been overexploited so we can try and get back to a balanced ocean ecosystem.”

The tracks of the smooth hammerheads (and other shark species) can be found here.

Shark and bony fish evolution, new research


This 9 September 2020 video from England says about itself:

410-Million-Year-Old Fish Fossil Virtual 3D CT Scan

Virtual three-dimensional model of the braincase of Minjinia turgenensis generated from CT scan.

Credit: Imperial College London/Natural History Museum

From Imperial College London in England:

Ancient bony fish forces rethink of how sharks evolved

September 7, 2020

Sharks’ non-bony skeletons were thought to be the template before bony internal skeletons evolved, but a new fossil discovery suggests otherwise.

The discovery of a 410-million-year-old fish fossil with a bony skull suggests the lighter skeletons of sharks may have evolved from bony ancestors, rather than the other way around.

Sharks have skeletons made of cartilage, which is around half the density of bone. Cartilaginous skeletons are known to evolve before bony ones, but it was thought that sharks split from other animals on the evolutionary tree before this happened; keeping their cartilaginous skeletons while other fish, and eventually us, went on to evolve bone.

Now, an international team led by Imperial College London, the Natural History Museum and researchers in Mongolia have discovered a fish fossil with a bony skull that is an ancient cousin of both sharks and animals with bony skeletons. This could suggest the ancestors of sharks first evolved bone and then lost it again, rather than keeping their initial cartilaginous state for more than 400 million years.

The team published their findings today in Nature Ecology & Evolution.

Lead researcher Dr Martin Brazeau, from the Department of Life Sciences at Imperial, said: “It was a very unexpected discovery. Conventional wisdom says that a bony inner skeleton was a unique innovation of the lineage that split from the ancestor of sharks more than 400 million years ago, but here is clear evidence of bony inner skeleton in a cousin of both sharks and, ultimately, us.”

Most of the early fossils of fish have been uncovered in Europe, Australia and the USA, but in recent years new finds have been made in China and South America. The team decided to dig in Mongolia, where there are rocks of the right age that have not been searched before.

They uncovered the partial skull, including the braincase, of a 410-million-year-old fish. It is a new species, which they named Minjinia turgenensis, and belongs to a broad group of fish called ‘placoderms‘, out of which sharks and all other ‘jawed vertebrates’ — animals with backbones and mobile jaws — evolved.

When we are developing as foetuses, humans and bony vertebrates have skeletons made of cartilage, like sharks, but a key stage in our development is when this is replaced by ‘endochondral’ bone — the hard bone that makes up our skeleton after birth.

Previously, no placoderm had been found with endochondral bone, but the skull fragments of M. turgenensis were “wall-to-wall endochondral.” While the team are cautious not to over-interpret from a single sample, they do have plenty of other material collected from Mongolia to sort through and perhaps find similar early bony fish.

And if further evidence supports an early evolution of endochondral bone, it could point to a more interesting history for the evolution of sharks.

Dr Brazeau said: “If sharks had bony skeletons and lost it, it could be an evolutionary adaptation. Sharks don’t have swim bladders, which evolved later in bony fish, but a lighter skeleton would have helped them be more mobile in the water and swim at different depths.

“This may be what helped sharks to be one of the first global fish species, spreading out into oceans around the world 400 million years ago.”

Prehistoric big shark Megalodon, how big?


Palaeoartist reconstruction of a 16 m adult Megalodon. Credit: Reconstruction by Oliver E. Demuth

From the University of Bristol in England:

True size of prehistoric mega-shark finally revealed

September 3, 2020

To date only the length of the legendary giant shark Megalodon had been estimated. But now, a new study led by the University of Bristol and Swansea University has revealed the size of the rest of its body, including fins that are as large as an adult human.

There is a grim fascination in determining the size of the largest sharks, but this can be difficult for fossil forms where teeth are often all that remain.

Today, the most fearsome living shark is the Great White, at over six metres (20 feet) long, which bites with a force of two tonnes.

Its fossil relative, the big tooth shark Megalodon, star of Hollywood movies, lived from 23 to around three million years ago, was over twice the length of a Great White and had a bite force of more than ten tonnes.

The fossils of the Megalodon are mostly huge triangular cutting teeth bigger than a human hand.

Jack Cooper, who has just completed the MSc in Palaeobiology at the University of Bristol’s School of Earth Sciences, and colleagues from Bristol and Swansea used a number of mathematical methods to pin down the size and proportions of this monster, by making close comparisons to a diversity of living relatives with ecological and physiological similarities to Megalodon.

The project was supervised by shark expert Dr Catalina Pimiento from Swansea University and Professor Mike Benton, a palaeontologist at Bristol. Dr Humberto Ferrón of Bristol also collaborated.

Their findings are published today in the journal Scientific Reports.

Jack Cooper said: “I have always been mad about sharks. As an undergraduate, I have worked and dived with Great whites in South Africa — protected by a steel cage of course. It’s that sense of danger, but also that sharks are such beautiful and well-adapted animals, that makes them so attractive to study.

“Megalodon was actually the very animal that inspired me to pursue palaeontology in the first place at just six years old, so I was over the moon to get a chance to study it.

“This was my dream project. But to study the whole animal is difficult considering that all we really have are lots of isolated teeth.”

Previously the fossil shark, known formally as Otodus megalodon, was only compared with the Great White. Jack and his colleagues, for the first time, expanded this analysis to include five modern sharks.

Dr Pimiento said: “Megalodon is not a direct ancestor of the Great White but is equally related to other macropredatory sharks such as the Makos, Salmon shark and Porbeagle shark, as well as the Great white. We pooled detailed measurements of all five to make predictions about Megalodon.”

Professor Benton added: “Before we could do anything, we had to test whether these five modern sharks changed proportions as they grew up. If, for example, they had been like humans, where babies have big heads and short legs, we would have had some difficulties in projecting the adult proportions for such a huge extinct shark.

“But we were surprised, and relieved, to discover that in fact that the babies of all these modern predatory sharks start out as little adults, and they don’t change in proportion as they get larger.”

Jack Cooper said: “This means we could simply take the growth curves of the five modern forms and project the overall shape as they get larger and larger — right up to a body length of 16 metres.”

The results suggest that a 16-metre-long Otodus megalodon likely had a head round 4.65 metres long, a dorsal fin approximately 1.62 metres tall and a tail around 3.85 metres high.

This means an adult human could stand on the back of this shark and would be about the same height as the dorsal fin.

The reconstruction of the size of Megalodon body parts represents a fundamental step towards a better understanding of the physiology of this giant, and the intrinsic factors that may have made it prone to extinction.

Pike against Swedish algae problem


This 3 December 2018 video is called Pike React to Fish in a Bottle.

From the University of Groningen in the Netherlands:

How sticklebacks dominate perch

Analysis reveals waves of stickleback domination along the Baltic coast

August 27, 2020

A research project on algal blooms along the Swedish coast, caused by eutrophication, revealed that large predators such as perch and pike are also necessary to restrict these blooms. Ecologist Britas Klemens Eriksson from the University of Groningen and his colleagues from Stockholm University and the Swedish University of Agricultural Sciences, Sweden have now shown that stickleback domination moves like a wave through the island archipelagos, changing the ecosystem from predator-dominated to algae-dominated. Their study was published on 27 August in the journal Communications Biology.

Eriksson experimented with the effects of nutrients on algal blooms while working as a postdoctoral researcher in Sweden. When he added nutrients to exclusion cages in the brackish coastal waters, algae began to dominate. This was no surprise. However, when he excluded large predators, he saw similar algal domination. ‘Adding nutrients and excluding large predators had a huge effect,’ he recalls, 10 years later.

Food web

The big question that arose from these results using small exclusion cages was whether the results would be the same for the real Swedish coastal ecosystem. This coast consists of countless archipelagos that stretch up to 20 kilometres into the sea, creating a brackish environment. Here, perch and pike are the top predators, feeding on sticklebacks, which themselves eat the small crustaceans that live off algae.

To investigate how this food web developed over the past 40 years, Eriksson (who had moved to the University of Groningen in the Netherlands) connected with his colleagues at Stockholm University and the Swedish University of Agricultural Sciences to gather data on fish abundances and to carry out a series of field studies. They were inspired by recent suggestions that regime shifts can occur in closed systems such as lakes and wondered whether algal blooms in the Baltic sea could also be a consequence of such a regime change.

Grazers

Eriksson and his colleagues sampled 32 locations along a 400-kilometre stretch of coastline. ‘We visited these sites in the spring and autumn of 2014 and sampled all levels of the food web, from algae to top predators.’ These data were subsequently entered into a food web model, which helped them to find connections between species. The models showed that the small sticklebacks were important for the reproduction of the larger predators. And a local increase in sticklebacks means that a lot of the grazers in the ecosystem are eaten, which drives algal domination.

‘If you just look at the abundances of fish, you find a mixed system in which different species dominate,’ Eriksson explains. But looking at the changes in these fishery data over time showed an increase in sticklebacks that started in the late 1990s, initially in the outer parts of the archipelagos. ‘This is presumably caused by a reduction in the number of large predators. The reduction is the combined result of habitat destruction, fishing and increased predation by cormorants and seals.’ Sticklebacks migrate from the outer archipelagos inwards to reproduce, linking coastal and offshore processes.

Predation

Reduced predation increases the survival of sticklebacks, while both eutrophication and warming help to increase their numbers even further. As the sticklebacks reduced the number of grazers, algae began to replace seagrass and other vegetation. Furthermore, the sticklebacks also fed on the larvae of perch and pike, thereby further reducing their numbers. ‘This is a case of predator-prey reversal,’ explains Eriksson. Instead of top predators eating sticklebacks, the smaller fish strongly reduced the number of perch and pike larvae.

Over time, the stickleback domination moved inwards like a wave: regional change propagated throughout the entire ecosystem. This has important consequences for ecosystem restoration. ‘To counter algal blooms, you should not only reduce the eutrophication of the water but also increase the numbers of top predators.’ It means that those organizations that manage fisheries must start working together with those that manage water quality. ‘We should not look at isolated species but at the entire food web,’ says Eriksson. ‘This is something that the recent EU fishery strategy is slowly starting to implement.’

Furthermore, the propagation of local changes throughout a system has wider implications in ecology, especially in natural ecosystems that have complex interaction and information pathways. ‘And we know this from politics and human behaviour studies. A good example is the Arab Spring, which started locally and then propagated across the Middle East.’

Asian fish can walk on land


This 2015 video says about itself:

The Hillstream Loach is not just cool and interesting, its also very popular in the aquarium hobby with many variants available.

Common/Trade Name: Hillstream Loach, Butterfly Loach
Scientific Name: Sewellia lineolata
Family: Balitoridae
Location: Southeast and East Asia
Max. size: 3 inches / 8 – 9 cm
PH range: 6.0 — 7.4
Temperament: Peaceful. Good candidate for a community fish tank
Temperature range: 68 – 75° F
Care level: Well acclimated specimens are quite hardy. Smaller individuals are quite tolerant of each other but will become more territorial as they grow. This fish prefers well-oxygenated water with plenty of hiding spots. They will scavenge dry and frozen foods. They love water movement, so a circulating powerhead is ideal for keeping these fish happy.

From the New Jersey Institute of Technology in the USA:

Key to fish family’s land-walking abilities revealed in study of Asia’s hillstream loaches

August 26, 2020

Summary: A new genetic and morphological study of South Asia’s hillstream loach (Balitoridae) family is shedding new light on the fishes’ unusual land-walking capabilities, including that of the family’s strangest relative — Cryptotora thamicola — a rare, blind cavefish from Thailand with an uncanny ability to walk on land and climb waterfalls using four limbs that move in salamander-like fashion.

In a study published in the Journal of Morphology, a team of researchers from New Jersey Institute of Technology (NJIT), Florida Museum of Natural History, Louisiana State University and Thailand’s Maejo University have successfully pieced together the ancestral relationships that make up the family tree of hillstream loaches (Balitoridae), detailing for the first time a range of unusual pelvic adaptations across the family that have given some of its members an ability to crawl, or even walk as salamanders do, to navigate terrestrial surfaces.

The team’s DNA-based comparative analysis of the fish family, known to currently encompass more than 100 species native to South and Southeast Asia, is the first of its kind to include Cryptotora thamicola — the only living species of fish known to walk on land in a step pattern similar to tetrapods, or four-limbed vertebrates such as reptiles and amphibians.

The results have revealed that three dominant variations of pelvic anatomy in the family, notably including key variations of a robust pelvic girdle and elongated sacral rib among many loaches, which researchers expect are central in explaining the different degrees of land-walking behavior exhibited by the fishes. The team says that the family’s modified pelvic features enabling terrestrial locomotion, which were found most pronounced in Cryptotora thamicola, may have been adapted to enhance their odds of survival in rivers and other fast-moving water environments that many Balitoridae inhabit today.

“The modified morphology of these Balitoridae, particularly the enlarged sacral rib connecting the pelvic plate to the vertebral column, is a big part of why studying this family is so exciting,” said Callie Crawford, the study’s corresponding author and Ph.D. candidate at NJIT’s Department of Biological Sciences. “These loaches have converged on a structural requirement to support terrestrial walking not seen in other fishes. What we’ve discovered is three anatomical groupings that have major implications for the biomechanics of terrestrial locomotion of these loaches, and the relationships among these fishes suggest that the ability to adapt to fast-flowing rivers may be what was passed on genetically, more than the specific morphology itself.”

“Now that we have revealed a spectrum of pelvic morphologies among these fishes, we can compare the extent of skeletal support with the walking performance in a species,” said Brooke Flammang, the study’s lead principal investigator and assistant professor of biology at NJIT. “This will allow us to measure the mechanical contribution of robust hips to terrestrial locomotion.”

Unlike most living fishes that feature pelvic fins located more anteriorly and attached to the pectoral girdle, balitorids typically boast a skeletal connection between the pelvic plate (basipterygium) and the vertebral column via a modified sacral rib and its distal ligament. These modifications are understood to help generate force against the ground useful for navigating land. The most extreme example emerged in 2016 with the discovery of Cryptotora thamicola in the fast-flowing aquatic conditions of the Tham Maelana and Tham Susa karst cave systems in northern Thailand. NJIT researchers then first identified that the rare species used a robust pelvic girdle attached to its vertebral column to walk and climb waterfalls with a salamander-like gait.

“This trait is likely key to helping these fishes avoid being washed away in the fast-flowing environment that they live in,” said Zach Randall, co-author of the paper and biological scientist at Florida Museum of Natural History. “What’s really cool about this paper is that it shows with high detail that robust pelvic girdles are more common than we thought in the hillstream loach family.”

“The sacral ribs allow forces from the fins pressing against the ground to be transferred to the body so that every time the fin pushes down during a step, the body is pushed up and forward,” explained Flammang. “The increased surface area of the more modified sacral ribs also offers more room for muscle attachment, so fishes such as Cryptotora thamicola can rotate their hips during walking, producing a salamander-like gait.”

River Loach Family Factions

To better understand the evolution of the river loach family, the team conducted a broad sampling of ?CT-scan data taken from 29 representative specimens, analyzing and comparing skeletal structures, muscle morphology as well as sacral rib shape across 14 of the 16 balitorid genera. The team also sampled genomic datasets of 72 loaches across seven families to reconstruct the evolutionary relationships in the Ballitoridae tree of life. “We were able to use a large survey of museum specimens and CT scanning to incorporate data even from specimens that didn’t have tissue or genetic data intact,” noted Randall.

The results showed that the loaches fall into three distinct morphotypes, which are expected to correlate to how well they are able to maneuver on land: species with a long, narrow rib that meets the pelvic plate; species with a thicker, slightly curved rib meeting the pelvic plate; and species with a robust crested rib interlocking with the pelvic plate. Of the species sampled, eleven fell into the third category with advanced land-walking abilities, such as Cryptotora thamicola, displaying the most robust sacral rib connection between the basipterygium and vertebral column.

“Our analysis showed that the morphotypes are not grouped by closely related taxa, but instead appear spread out across the phylogeny. That indicates to us that the extent of the modification of these features is less reflecting shared ancestry and more likely a product of adaptation to the flow regimes of their environments,” explained Crawford. “To better understand how and why these distinct morphotypes developed, we need more knowledge of the habitat of each species, including water flow rates, substrate types and how the rivers and streams change between rainy and dry seasons.”

Crawford and colleagues now aim to further investigate the stability physics and muscular forces at play that allow certain species to push their bodies off their ground as they walk. The team, including a recent Rutgers University graduate, Amani Webber-Schultz, recently completed fieldwork in Thailand earlier this year to collect more balitorid specimens, which they are studying using high-speed videos of the fishes walking.

“This will allow us to study details of their walking kinematics and gain even more insight into how walking performance might change between species with different pelvic morphologies,” said Crawford.

The study was supported by the National Science Foundation’s Understanding the Rules of Life Grant # 1839915 to BE Flammang, P Chakrabarty, and LM Page.

Sharks and rays of Florida, USA


This 29 July 2020 video says about itself:

For the third straight year, we have had the privilege of filming giant hammerhead sharks hunting blacktip sharks off the beaches in Florida. The average size of a blacktip shark is 6ft in length, with an estimated weight of around 80lbs. The hammerhead sharks are much larger, measuring over 14ft in length and weighing well over 1000lbs. We filmed some incredible footage with our drone of giant hammerhead sharks hunting and eating blacktip sharks within the beach’s swimming distance.

From Florida Atlantic University in the USA:

Scientists catalogue shark and ray distribution in Florida lagoon

August 25, 2020

Summary: A study is the first long-term, in-depth analysis of the elasmobranch community in Florida’s Indian River Lagoon and develops capacity to understand how these species may respond to further environmental changes. From 2016 to 2018, researchers caught 630 individuals of 16 species, including two critically endangered smalltooth sawfish. Results showed that many elasmobranchs use the southern Indian River Lagoon throughout their life histories and the area may serve as an important nursery habitat for multiple species.

Many elasmobranch species, which include sharks, skates, and rays, use estuaries as nurseries, for birthing, and as foraging grounds. Florida’s Indian River Lagoon is one of 28 estuaries designated as an “estuary of national significance” by the Environmental Protection Agency’s National Estuary Program. In recent decades, this estuary has experienced many environmental impacts, such as habitat degradation and harmful algal blooms resulting in degraded water quality and fish kills. Currently, there is a substantial data gap surrounding the status of elasmobranchs in this estuary system.

Researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute conducted a fishery-independent survey to characterize the elasmobranch community and understand distribution patterns and habitat use in the Indian River Lagoon from Sebastian to St. Lucie Inlet. This study provides the first long-term, in-depth analysis of the elasmobranch community in the southern Indian River Lagoon and develops capacity to understand how these species may respond to further environmental changes.

Results of the study, published in Estuaries and Coasts, the journal of the Coastal and Estuarine Research Foundation, showed that many elasmobranchs use the southern Indian River Lagoon throughout their life histories and the area may serve as an important nursery habitat for multiple species.

From 2016 to 2018, researchers caught 630 individuals of 16 species, including two critically endangered smalltooth sawfish (Pristis pectinata). They characterized the species composition and distribution of elasmobranchs, examined spatial and temporal variability in the elasmobranch community, and assessed how temperature, salinity, dissolved oxygen, depth, water clarity, distance to an inlet, and distance to a freshwater source affect elasmobranch community composition. The two most commonly caught species were bull sharks and Atlantic stingrays, the only two species to each comprise greater than 20 percent of the catch. The remaining 14 species comprised 53 percent of the catch.

Researchers also observed size and compositional differences by region and season; for example, bull sharks were most abundant in Vero Beach and the St. Lucie River, and both bull sharks and Atlantic stingrays were more abundant in the fall than in the spring and summer. Clearer, relatively deeper, and higher salinity waters farther from freshwater sources and closer to inlets resulted in a more diverse community; while bull sharks and Atlantic stingrays dominated shallower, less clear waters closer to freshwater sources and further from inlets.

“As global human populations increase and environmental pressures on estuaries become more widespread, it is essential to continue to monitor changes in elasmobranch communities in order to effectively manage and conserve these populations,” said Grace Roskar, M.S., lead author, current Knauss Fellow with NOAA Fisheries and former graduate student working with Matt Ajemian, Ph.D., co-author and an assistant research professor at FAU’s Harbor Branch. “Establishing updated records of the diversity and distribution of elasmobranchs in the Indian River Lagoon is a critical first step to understand how varying environmental and pollution impacts may affect these species, which are integral to the fish community of the lagoon and surrounding habitats.”

The interconnected nature of abiotic parameters such as distance to freshwater sources or inlets and salinity that influenced elasmobranch distributions suggest important implications for future hydrological changes in the Indian River Lagoon.

“If freshwater discharges into the Indian River Lagoon increase in duration and/or volume, the elasmobranch community could shift even further to bull shark and Atlantic stingray dominance. Less tolerant species may be driven closer to the inlets or even out of the estuary to nearshore ocean habitats,” said Ajemian. “These community shifts could result in both decreased elasmobranch diversity and biodiversity of the estuary as a whole, possibly altering the dynamics of prey populations as well. Moreover, displaced species may face increased risks of predation or competition as well as declines in habitat quality or prey availability.”

The researchers emphasize the importance of continuing the survey for additional years to yield greater sample sizes and allow for the formulation of standardized relative abundance indices that will be useful in the stock assessment process, which is essential to fisheries management.

Quadruped evolution and Australian lungfish


This 11 July 2020 video is called Australian Lungfish Release – lake Gkula. it says about itself:

The lake is finally ready for the Lung Fish population. Snail, mussel and eel grass beds are established allowing plenty of food for these endemic species to thrive. The ecology of Lake Gkula is well advanced in such a short time (at this publishing it has been running for 8 months). We look forward to snorkeling to visit the Lung Fish and will keep you updated on their growth and progress.

From the University of Konstanz in Germany:

Lungfish fins reveal how limbs evolved

August 19, 2020

Summary: New research on the fin development of the Australian lungfish elucidates how fins evolved into limbs with hands with digits. The main finding is that in lungfish a primitive hand is already present, but that functional fingers and toes only evolved in land animals due to changes in embryonic development.

The evolution of limbs with functional digits from fish fins happened approximately 400 million years ago in the Devonian. This morphological transition allowed vertebrates to leave the water to conquer land and gave rise to all four-legged animals or tetrapods — the evolutionary lineage that includes all amphibians, reptiles, birds and mammals (including humans). Since the nineteenth century several theories based on both fossils and embryos have been put forward trying to explain how this transformation unfolded. Yet, exactly how hands with digits originated from fish fins remained unknown.

An international team of biologists based at the University of Konstanz (Germany), Macquarie University in Sydney (Australia) and the Stazione Zoologica Anton Dohrn in Naples (Italy) has determined how limbs have evolved from fins using embryos of the Australian lungfish (Neoceratodus forsteri) for their study. The Australian lungfish is the closest living fish relative of tetrapods and is often considered a “living fossil” as it still resembles the fishes that were around at the time when the first four-limbed vertebrates began to walk on land. For these reasons the fins of lungfish provide a better reference to study the evolutionary transition of fins into limbs than any other extant fish species.

The team’s research, which is reported in the latest issue of Science Advances, shows that a primitive hand is present in lungfish fins but at the same time suggests that the unique anatomy of limbs with digits only evolved during the rise of tetrapods through changes in embryonic development.

Insights from embryonic development: limb “architect” genes

To solve the puzzle of how limbs emerged from fins during evolution researchers have focused on embryonic development. “During embryogenesis, a suite of ‘architect’ genes shapes an amorphous group of precursor cells into fully grown limbs,” explains Dr. Joost Woltering, first author on the study and an assistant professor in the Evolutionary Biology group at the University of Konstanz led by Professor Axel Meyer. The very same “architect” genes also drive fin development. However, because evolutionary changes have occurred in the activity of these genes, the developmental process produces fins in fish and limbs in tetrapods.

To compare this process in fins and limbs, the team studied such “architect” genes in the embryos of the Australian lungfish. “Amazingly, what we discovered is that the gene specifying the hand in limbs (hoxa13) is activated in a similar skeletal region in lungfish fins,” explains Woltering. Importantly, this domain has never been observed in the fins of other fish that are more distantly related to tetrapods. “This finding clearly indicates that a primitive hand was already present in the ancestors of land animals.”

Developmental patterns: differences and similarities

The lungfish “hand,” in spite of this modern genetic signature, only partially resembles the anatomy of tetrapod hands because it lacks fingers or toes. To understand the genetic basis for this difference the team went on to analyse additional genes known to be associated with the formation of digits, finding that one gene important for the formation of fingers and toes (hoxd13 — a “sister gene” to the above-mentioned hoxa13) appeared to be switched on differently in fins.

During tetrapod limb development, the hoxd13 gene is switched on in a dynamic manner. It first becomes activated in the developing pinky finger and then expands all the way throughout the future hand towards the thumb. This process coordinates the correct formation of all five fingers. While Joost Woltering’s team observed a similar activation pattern of this gene in lungfish fins, it did not show this expansion but only remained activated in exactly one half of the fin. Additional differences were found for genes that are normally switched off in digits. In lungfish fins these genes remain active, but on the opposite side of the domain where hoxd13 is activated.

Old hypotheses — future directions

“All of this goes to show that while lungfish fins unexpectedly have a primitive hand in common with tetrapods, the fins of our ancestors also needed an evolutionary ‘finishing touch’ to produce limbs. In this sense it looks as if the hand was there first, only to be complemented with digits later during evolution,” says Woltering. One influential hypothesis regarding the evolution of limbs first put forward by early 20th-century palaeontologists Thomas Westoll and William Gregory, and in the 1980s famously developed further by Neil Shubin, postulates that fingers and toes arose through an expansion of the skeletal elements on one side of the fins of the tetrapod ancestor. This inferred expansion of fin elements corresponds exactly to the differences the team found in the expansion of the digit genes between lungfish fins and tetrapod limbs. The team’s observations on the activation and deactivation of limb “architect” genes in lungfish fins thus provides evidence in support of this classical transformational model.

In the future, to fully understand what causes this domain to expand, making our limbs so different from fish fins, the researchers plan to conduct further analyses on the development of fins and limbs, using lungfish but also more modern fish species such as cichlids as their embryos are easier to investigate using techniques like CRISPR. “To complete the picture of what happened in our fish ancestors that crawled onto land hundreds of millions of years ago, we really rely on currently living species to see how their embryos grow fins and limbs so differently,” concludes Woltering.

Background

– A new study by an international team of researchers from the University of Konstanz (Germany), Macquarie University in Sydney (Australia) and the Stazione Zoologica Anton Dohrn in Naples (Italy) provides an evolutionary model of how hands with digits emerged from fish fins.

– Studying the embryos of Australian lungfish (Neoceratodus forsteri), the closest extant fish relative of tetrapods, the researchers identified similarities and differences in the way lungfish fins and tetrapod limbs form during embryonic development.

– The presence of a primitive hand domain common to fins and limbs is revealed by the expression of a gene responsible for the specification of the hand in limbs (hoxa13). This gene becomes activated in similar skeletal domains in tetrapods and lungfish.

– One of the main morphological differences between fins and limbs, namely the absence of digits, can be explained by differences in the activation (hoxd13) and de-activation (alx4, pax9) of genes involved in digit development. This suggests that limbs with digits evolved from fish fins through changes in the activation of digit specific genes within a primitive hand domain.

How pregnant male seahorses feed embryos


This 29 March 2020 video from Ireland says about itself:

Seahorse Mating Dance

Filmed at Seahorse Aquariums in Dublin. Shortly after putting away the camera the female started laying eggs into the male’s pouch – typical! Three types of seahorse appear in the video and if you look carefully you will see a baby seahorse floating through the water.

Music Royalty free from: Kevin MacLeod (incompetech.com)

From the University of Sydney in Australia:

Who’s your daddy? Male seahorses transport nutrients to embryos

Male seahorse pregnancy could be as complex as female pregnancy

August 13, 2020

New research by Dr Camilla Whittington and her team at the University of Sydney has found male seahorses transport nutrients to their developing babies during pregnancy. This discovery provides an opportunity for further comparative evolutionary research.

Seahorses and their relatives are the only vertebrates that have male pregnancy. The expectant fathers incubate developing babies inside a pocket called a “brood pouch.” We know a male seahorse can have more than a thousand embryos in the pouch at once but until now, researchers had limited understanding of how the babies are fed.

“This work adds to the growing evidence that male pregnancy in seahorses could be as complex as female pregnancy in other animals, including ourselves,” said Dr Whittington, from the School of Life and Environmental Sciences. “We now know that seahorse dads can transport nutrients to the babies during pregnancy, and we think they do this via a placenta. It’s not exactly like a human placenta though — they don’t have an umbilical cord, for example. We need to do further histological work to confirm this.”

Seahorses are emerging as important model species for understanding the evolution of live-bearing reproduction, said Dr Whittington.

“We can draw some parallels between seahorse pregnancy and human pregnancy,” she said. “Seahorse dads seem to do some of the same things that human mums do, including transporting nutrients and oxygen to developing embryos, and immune modulation to protect the babies from infection.”

The research published in Journal of Comparative Physiology B was led by University of Sydney Honours student Zoe Skalkos in collaboration with Dr James Van Dyke at La Trobe University.

The study builds on previous genetic evidence suggesting that male seahorses might transport nutrients to developing embryos. This new study confirms, in the first experimental evidence of ‘patrotrophy’ (nutrient transport from dad to babies). It also identified one of the classes of nutrients being transported: energy-rich fats.

“My team is using a range of techniques to investigate the biology of seahorse pregnancy,” Dr Whittington said. “We want to understand more about the seahorse pouch and the ways it protects and supports the baby seahorses.”

Honours student Zoe Skalkos, who led the research, said: “It’s really exciting because it’s a big step in understanding the relationship between dad and baby in male pregnancy.”

Key Points:

  • Seahorses and their relatives are the only vertebrates that have male pregnancy. Dads incubate developing babies inside a pocket called a “brood pouch.”
  • Male seahorses transport nutrients, including fats, to developing babies during pregnancy. The babies use these energy-rich fats for growth and development.
  • The new results raise the question of whether seahorse embryos can influence how much nutrition they can get from dad while they are in the brood pouch.

Nestlé corporation accused of killing many fish


Dead fish in the Aisne river in France, photo by Fédération de pêche des Ardennes

Translated from Dutch NOS radio today:

Nestlé sued for thousands of dead fish in French river

A French fishing federation is suing food corporate giant Nestlé after finding thousands of dead fish in a river near a Nestlé factory. “Everything is dead over a length of seven kilometers,” says the fishing federation.

The dead fish were spotted on Sunday night in the river Aisne near the village of Challerange, between Reims and Verdun. According to local authorities, the fish died from a lack of oxygen in the water. The Ardennes fishing federation estimates the damage at several thousand euros and wants this to be paid by Nestlé France, the owner of the factory in Challerange. Where milk powder is made for in coffee cups.

“Fourteen fish species have been affected,” the federation told AFP news agency. “Including the protected eel and the lamprey.” Volunteers from the Fish Federation and the Fire Department have been working all week to remove dead fish that have washed up. At least 1 ton of fish has already been removed. The banks of the Aisne are off-limits until further notice because there are still many fish that are decomposing by the heat.

The factory says that a liquid was indeed accidentally spilled into the river on Sunday evening. …

It is still being investigated what exactly was in the water.

Pink catfish discovered in Venezuelan cave


This 10 August 2020 video from Venezuela says about itself:

Pink Catfish Discovered In Mountain Cave | The Dark: Nature’s Nighttime World | BBC Earth

This tiny pink catfish is a welcome surprise for the team. It has never seen daylight or an ocean. The crew inspect it closely and document their discovery.