Long-beaked echidna


Zaglossus, known as the long-beaked echidnas make up one of the two extant genera of echidnas: there are three extant species, all living in New Guinea. They are medium-sized, solitary mammals covered with coarse hair and spines made of keratin. They have short, strong limbs with large claws, and are powerful diggers. What separates the 3 long-beaked echidna species is mainly location in New Guinea. Other signifying characteristics include skull morphology, color and density of fur and spines, body size, and number of toes and claws. They are a highly primitive species, with many characteristics derived from reptiles.
The extant species are:
The Eastern species is listed as vulnerable, while the Attenborough's and western long-beaked echidna species are listed as Critically Endangered by the IUCN.
A number of extinct species were known in the genus, but they are currently treated as members of their own genera, such as Murrayglossus and Megalibgwilia.

Anatomy and morphology

The long-beaked echidna is larger-bodied than the short-beaked and has fewer, shorter spines scattered among its coarse hairs. In comparison to short-beaked echidnas, long-beaked echidna spines are not as heavily rooted, and so they rip out easier. Adult long-beaked echidnas weigh approximately 6.5 kg and juveniles approximately 4.3 kg. Z. attenboroughi is the smallest of the 3 species. The snout is two-thirds of the head's length and curves slightly downward. Females are generally longer, heavier and have longer beaks than their male counterparts. None of these features can determine age, and they are also not reliable for determining sex. Echidna necks are not prominent.
They also lack teeth, although earlier fossil records suggest that they once did have teeth. Long beaked echidnas have keratinous spines on the bottom of their tongue that they use to grind and digest their prey. Echidnas are of few mammals that don’t have a mandibular meniscus, likely because they use their tongue and palate to grind food, rather than their jaw.
Like the other species of echidna, long-beaked echidnas have spurs on their hind legs. These spurs are vestigial; part of a repressed venom system akin to the one on the platypus. Juveniles have a sheath covering their spurs, one of the only determining traits of young. Male spurs are nonfunctional and females usually lose their spurs as they age. However, this is not a reliable way of determining sex.
The Z. attenboroughi and the Z. Bartoni usually have 4, sometimes 5, clawed toes on each foot. The Z. bruijni has 4 toes on each foot, but only 3 of the 4 toes are clawed.
Monotremes are very different from many animals in the ways that they reproduce. All other mammals either lack a cloaca entirely, or in the case of marsupials, don’t retain it into adulthood. Rather than descending externally into a scrotum or inguinal canal, their testes stay in the abdominal canal. Their sperm travels in bundles rather than individually. Their penis is only used for reproduction, as their cloaca excretes waste. Male echidnas have a four-headed penis, where only 2 of the 4 glans can become erect at a time. Being able to switch between the two could allow for more success in mating.
The breeding female develops a temporary abdominal brood patch, in which her egg is incubated and in which the newborn young remains in safety as it feeds and develops. Most of the development occurs after birth in the mothers pouch, much like marsupials. The long-beaked echidna has a short weaning period, approximately 12 days. During this time milk is their only source of nutrition and protection for the hatchlings; they are altricial and immunologically naive. Although laying eggs that are incubated outside of the body is primarily a reptilian trait, all monotremes are considered mammals because they lactate to feed their young. Additionally, the sex of the young cannot be determined based on physical traits.
Many mammals have protective antibodies in their milk to enhance survival rates. For echidnas, EchAMP provides young with antibacterial protection through lactation. Monotremes are especially at high risk of contracting bacterial infections due to the fact that most of their development takes place after birth, as well as the lack of nipples for puggles to latch onto.
Monotremes are more basal, or "primitive" compared to other mammals, retaining features found in many non-mammalian synapsid and reptile groups. Despite having features in common with reptiles, monotremes are more closely related to other mammals than to reptiles. Non-mammalian synapsids thrived during the Permian and early Triassic periods, before the evolution of dinosaurs. All echidnas have retained reptile-like skull features and shoulder girdles. Although, their brain size is more comparable to placental mammals.
The long-beaked echidna's limb posture is sprawled, similar to extant reptiles like lizards and crocodilians. Although the stances between the animal groups are similar, the way the limbs move are very different between the clades. The echidna swings its limbs at a 45 degree angle while a lizard's is more horizontal. They walk with two legs on one side of the body moving in unison.
The long-beaked echidna's walk presents multiple differences from a lizard's. An echidna's walking pattern is more upright than a lizard's, this represents a pattern closer to a parasagittal kind of therian. Echidnas and therians both have a dynamic equilibration rather than a static one.
Monotremes are some of the only mammals that have retained mobile cervical ribs. Studies have also shown an overlap in epicoracoid cartilage, which has also been found in amphibians. These studies suggest there is a possible correspondence with epicoracoid overlap and limb preferences, but further research is needed.
Fossils of extinct echidnas, Z. robustus and Z. hacketti, show many similarities with long-beaked echidnas. By this time, their toothless beaks and hemispherical cranium have already been developed.
Monotremes most likely originated during the Jurassic or late Triassic periods. Fossil records suggest that the monotremes began diversifying during the cretaceous period. It is widely agreed that the echidna's lineage diverged from the Ornithorhynchus anatinus due to the fact that platypus fossils can be dated back much farther than echidna fossils. However, the number of differences between the two species would suggest that they evolved from a common ancestor. In the beginning of the split, scientists can see that each species had developed different dental and skull features. Many believe both species are incomparable to the original monotremes. In a study done on EchAMP, it had shown that a partial peptide sequence PlatAMP was 94% the same as a partial peptide sequence of EchAMP. The study did not include the final sequence because of a lack of research done on PlatAMP. Although, long beaked echidnas are the only species that have the same diploid number as the common ancestor of monotremes, 2=64. Oxford did a recent study on the genome of echidnas, going into detail of the DNA mutations that caused the speciation of echidnas and platypus.
The beak of long beaked echidnas are more slender and curved downward than those of small-beaked echidnas. The cranium of short beaked echidnas are shorter and rounder than long-beaked echidnas. Long beaked echidnas also have a more prominent occipital condyle, allowing for a wider range of head movements, but reducing the ability to lift a pry things with their beak. Long beaked echidnas have a longer lower jaw than short beaked echidnas. All living monotremes have 7 cervical vertebrates. Long beaked echidnas have 17 thoracic vertebrae with associated ribs, four lumbar vertebrae, three vertebrae fused to form the sacrum, and 11 caudal vertebrae. The iliac crest is more pointed in long beaked echidnas than in short beaked echidnas. Only males in both long and short beaked echidnas have an os calcaris bone, the bone that the spurs rest on. This is likely the reason why the female spurs disappear in adulthood.

Behavior

Little is known about the life of these rarely seen animals, but it is believed to have habits similar to those of the short-beaked echidna; unlike them, however, the long-beaked echidnas feed primarily on earthworms rather than ants, as they live in much more humid environments than the smaller Tachyglossus echidna.
Their cognitive behaviors and the complexity of these behaviors show many similarities with large-brained placentals.
These echidnas are primarily nocturnal; foraging for its insect food on the forest floor and in rotting logs with their snout and forelimbs. The beaks of the attenboroughi species can leave foraging holes up to 14.8 cm deep and 6.6 cm wide. They use their forelimbs by cracking open logs and feeding on wood-boring vertebrates. These animals are not usually found foraging in the daylight. Their foraging behaviors are most easily found after rainfall.
They use electroreception along with highly specialized olfactory pathways to find prey. It is likely that long-beaked echidnas have a stronger electroreception sense than short-beaked echidnas. However, they have a very poor sense of hearing.
The long-beaked echidna establish and are commonly found in dens or burrows. Their dens are most often underground, but occasionally they will burrow at a cliff face or under deep vegetation. The latter dens are most often occupied by juveniles. Their burrows were approximately 2.7 meters long and 0.48 meters underground. They are often found on slopes, most likely to prevent flood runoff. They usually move to a different den every night and rarely return to the same den, except in some cases many years later. Burrows in use often have footprints surrounding them, accompanied by a strong scent of echidna waste.
A study published in 2015 shows that Zaglossus spp. in captivity exhibited "handedness" when performing certain behaviors related to foraging, locomotion, and male-female interactions. The results of this study suggest that handedness in mammals is a basal trait rather than one derived several times in extant mammals. It is believed this trait developed with the development of the hemispherical cranium.
They can live up to 60 years old in captivity. The Taronga Zoo in Sydney Australia had two long-beaked echidnas in their care. One female, brought in in 1963, that passed away in 2015, making her at least 53 years old. One male, brought in in 1968, making him at least 57 years old today, although some believe he is closer to 60 years old. There were many attempts at breeding long-beaked echidnas in captivity, but no efforts were successful.