Some insects and other arthropods you should not confuse

Untrustworthy and sensational news about insects and arthropods are constantly shared through social networks, spreading tergiversated data and confusing amateur users. As a result, this usually leads to misidentifications and unnecessary alarmism toward harmless organisms.

Here we bring you a brief list of some insects and other arthropods that are usually confused and how to tell them apart. Don’t get tricked!

Spiders VS ‘Anything resembling them’

Spiders (Order Araneae) probably are some of the most feared arthropods among users for two main reasons: they are venomous and there are a lot of other arachnids that resemble them. So, it is quite understandable some people have serious doubts when finding an organism with eight long legs and a grim face.

However, most of these spider-like organisms are harmless and  unable to weave webs:

Harvestmen: unlike other arachnids, harvestmen or daddy longlegs (Order Opiliones) don’t have their body divided into two parts (prosoma and opisthosoma) by a thin waist, so they remind off a ‘ball with legs’. Also, they only have a pair of central eyes very close to each other. They neither have venom glands nor silk glands, so they can’t bite nor weave webs. They live in moist places, caves and near to streams and harvests. They are usually confused with spiders of the Pholcidae family because of their long legs.

Pholcus phalangioides (Pholcidae) (Picture by Olaf Leillinger, CC 2.5)

Harvestman (Picture by Dalavich, CC 3.0)

Solifugae: also known as camel spiders, Solifugae is an order of tropical arachnids characterized for having a segmented body and a pair of conspicuously large chelicerae forwardly projected. However, and despite their menacing appearance, they aren’t venomous (even though they bite can be very painful) nor weave webs. They inhabit desert and arid places, some of them are nocturnal and the diurnal ones move quickly looking for shadows to escape from sunlight.

Camel spider (Picture by Swen Langel, CC 2.0).

Amblypygi: also known as whip spiders or tailless whip scorpions, Amblypygi is an order of tropical arachnids that are neither spiders nor scorpions. Despite their menacing appearance, as it happens with camel spiders, whip scorpions don’t have venom glands. They have a pair of big thorny pedipalps ended in a pincer for grabbing preys, while the first pair of legs, which are filiform and segmented, act as sensory organs (not for walk). They don’t weave webs and have nocturnal habits.

Amblypygi (Picture by José Eugenio Gómez Rodríguez on Flickr, CC 2.0)

Pill bugs VS Pill millipedes

When playing in a park or in some natural place as a kid, you some time probably found a small animal, full of legs that rolled up when being touched.

These organisms are commonly known as woodlice. Woodlice belong to the suborder Oniscidea, a group of terrestrial crustaceans within the order Isopoda. They have a tough, calcarean and segmented exoskeleton, and inhabit moist places.

Armadillidium vulgare, Oniscidea (Picture by Franco Folini, CC 2.5)

Woodlice of the family Armadillidae, also known as pill bugs, are usually confused with pill millipedes (Subphylum Myriapoda, Class Diplopoda, Superorder Oniscomorpha), both groups with a similar external appearance and able to roll up into an almost perfect sphere as a defensive mechanism (convergent evolution).

Glomeris marginata, Oniscomorpha (Picture by Stemonitis, CC 2.5).

To tell them apart, you have to count the total number of legs per segment: if it has only a pair of legs per segment (one at each side of the segment), it is a pill bug; if it has two pairs, it is a pill millipede.

Bees and wasps VS Hoverflies

We talked widely about the main differences between bees and wasps (Order Hymenoptera) in this post. This time, we introduce you the hoverflies or syrphid flies (Order Diptera, Suborder Brachycera, Family Syrphidae), which resemble a lot to bees and wasps.

Resemblance of hoverflies to bees, wasps and bumblebees is a clear example of Batesian mimicry, which we explained widely in this post about animal mimicry. Moreover, hoverflies mimicry goes even further, since some of them also imitate the flight and the hum of these hymenopterans.

Hoverfly (Public domain picture, CC0).

Honey bee (Picture by Andy Murray on Flickr, CC 2.0)

To tell them apart, you have to pay attention to their eyes, antennae and wings: since they are flies, hoverflies have a pair of big compound eyes that occupy almost all their head, very short antennae with eight or less segments and a single pair of wings (the second pair has evolved into small equilibrium organs, the halteres), while wasps, bees and bumblebees have smaller compound eyes that occupy only the sides of the head, longer antennae with ten or more segments and two pairs of functional wings. Moreover, female hoverflies don’t have the abdomen ended in a stinger, so they are completely harmless.

Ladybugs VS Pyrrhocoris apterus

If you look for ladybugs pictures on Internet, you’d probably find a picture of this insect:

Public domain picture (CC0)

This is Pyrrhocoris apterus, a very common insect in the Palearctic area (from Europe to China) and recorded to the USA, Central America and India. You can find it on common mallows (Malva sylvestris), from which they eat seeds and sap, and they usually congregate in big groups because of their gregarious behavior.

Ladybugs are coleopterans (Order Coleoptera) with a more or less globular shape; they are carnivorous (with a diet based mainly on the intake of aphids) and can fly. Their first pair of wings are hard (elytra) and form a kind of shield that encloses the second pair of membranous wings.

Ladybug Coccinella septempunctata (Public domain picture, CC0)

On the other hand, Pyrrhocoris apterus is a bug (Order Heteroptera) with a depressed body, phytophagous habits and, unlike ladybugs and other bugs, it is unable to fly. Moreover, it doesn’t have a hardened shield.

Mantises VS Mantidflies

Mantises (Order Dyctioptera), which were widely addressed in this post, are very alike to this insect:

Mantispa styriaca (Picture by Gilles San Martin on Flickr, CC 2.0)

This insect belongs to the family Mantispidae (Order Neuroptera), also known as mantidflies or mantispids. This group is very well represented in tropical and subtropical countries, and just a few species are known from Europe. They have a pair of raptorial legs like those of Mantodea which they use for grabbing their preys.

Neuropterans, like mantidflies, green lacewings and antlions, have two pairs of similar sized wings with a very complex and branched venation. In Mantodea, the first pair of wings are smaller and harder than the second one, which are membranous and functional for flying; also, this second pair doesn’t have such a complex venation like that of neuropterans.

Mantodea (Picture by Shiva shankar, CC 2.0)

Mantidflies of the genera Climaciella and Entanoneura have a body coloration like that of some wasps, but they are totally harmless.

Climaciella brunnea (Picture by Judy Gallagher on Flickr, CC 2.0)

Mosquitoes VS Crane flies

Have you ever seen a giant mosquito and dreaded its bite? Well, you can stop being afraid of it.

These giant ‘mosquitoes’ (Order Diptera), which are commonly known as crane flies or daddy longlegs (Family Tipulidae), are totally inoffensive (and somewhat clumsy). They are distributed all over the world and inhabit moist places, like meadows and streams. Adults feed on nectar or don’t feed; in any case, they don’t suck blood!

Females have the abdomen ended in a kind of stinger; however, it is only their sharp ovipositor (not a stinger like those of bees or wasps).

Female crane fly (Picture by Irene Lobato Vila)

Dragonflies VS Damselflies

Both groups belong to the Order Odonata and have very similar appearance and behavior, being very common near sitting waters and lakes.

Two thirds of the Odonata are dragonflies (suborder Anisoptera), while the other third are damselflies (suborder Zygoptera). An easy way to tell them apart is by paying attention to their wings at rest: in dragonflies, wings are held flat and away from the body, while in damselflies they are held folded, along or above the abdomen.

On the other hand, eyes of dragonflies are large and touch in the vertex of the head, of which they occupy most of its surface, while those of dragonflies are smaller and are usually located on the sides of the head.

Dragonfly (Public domain image, CC0)

Damselfly (Picture by Xosema, CC 4.0)

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If you know about any other insect or arthropod that can be confused, let us know it by leaving a comment!

References

• Capinera, J. L. (Ed.). 2008. Encyclopedia of entomology. Springer Science & Business Media.
• Resh, V. H. & Cardé, R. T. (Eds.). 2009. Encyclopedia of insects. Academic Press.
• Cooke, F. 2004. The encyclopedia of animals: a complete visual guide. University of California Press.

Sleep tight, don’t let the bed bugs bite!

Have you ever felt uncomfortable when hearing this expression or feared to find your bed infested with bed bugs? Yes, bed bugs exist. However, good news is that not all insects known as ‘bugs’ sting nor live inside our bed sheets.

What bugs really are? Are all of them harmful? Where can we find them? Find out their diversity through this post, and give up thinking that bugs are dangerous!

Which insects are called ‘bugs’?

When talking about ‘bugs’, people are unconscious about the true diversity of these organisms. Bugs, and more exactly true bugs, belong to the Heteroptera suborder, which includes more than 40,000 species worldwide; in fact, they are the largest group of insects with simple metamorphosis. Their most ancient fossil, Paraknightia magnífica, which was found in Australia, has been dated from the late Permian (260-251 MA).

The Heteroptera belong to the Hemiptera order, inside which we can find other suborders which were formerly classified as a single suborder (‘Homoptera’). Some of the suborders once classified as ‘Homoptera’ include some well-known organisms, such as cicadas (Cicadidae) and aphids (Aphididae).

How can we recognize them?

Heteropterans appear in different forms and sizes. The tiniest specimens belong to the Anthocoridae, Microphysidae, Ceratocombidae, Dipsocoridae, Aepophilidae and Leptopodidae families, which are barely visible to the naked eye. Among the largest members there are some species of the Belostomatidae family, such as Lethocerus indicus (6.5-8 cm length). Despite this, they appear as a monophyletic group according to molecular data.

They show at least three synapomorphies:

1. Piercing-sucking mouthparts, long, forming a stylet.

   

   Mouthparts of the predator Arilus cristatus (Reduviidae). Picture property of John Flannery on Flicker (CC 2.0).

2. Paired odoriferous glands.
3. Four-segmented antennae.

Furthermore, they have forewings (formally known as hemelytra) with both membranous and hardened portions, which gives its name to the group (Heteroptera, from the Ancient Greek ‘hetero’, different; ‘-pteron’, wings).

Pentatomidae. The proximal part of forewings is hardened, while the distal one is membranous. Picture property of Mick Talbot on Flickr (CC 2.0).

Ecology

Life cycle

Heteropterans undergo a simple metamorphosis, so youths or nymphs and adults almost show no differences and cohabit in the same habitat. After hatching, nymphs molt several times until reaching the last nymphal molt, known as imaginal molt, through which they reach adulthood.

Life cycle of heteropterans. Picture property of Encyclopedia Britannica, Inc. (link).

Adults differ from nymphs on having wings, a new disposition of odoriferous glands openings, a different number of tarsal (legs) and antennal segments, ocelli, ornaments (spines and glandular hairs), sexual traits on the terminal abdominal segments and sometimes a different coloration, besides a bigger size and a way harder tegument.

Nezara viridula nymph (Pentatomidae), still wingless. Picture property of S. Rae on Flickr (CC 2.0)

Communication and defense

Specimens of the same species emit volatile pheromones produced by their odoriferous glands as a way of communication. So, they can expel aggregation pheromones and sexual pheromones to gather in a point or to find a mate, respectively. In some species, it has also been documented the emission of sounds produced by stridulation, that is, producing sounds by rubbing together certain body parts.

Heteropterans develop passive and active defense mechanisms:

• Among passive mechanisms, we can highlight the own body shapes (e. g., smooth and rounded structures which difficult their capture by predators), the inactivity as a way to go unnoticed by other organisms, and the crypsis or mimicry. Some examples of crypsis or mimicry are 1) color mimesis (homocromy) 2) shape mimesis (homotopy), through which they imitate structures of their environment, either plants or animals (e. g. ant-mimicry or myrmecomorphy) and 3) disruptive mimesis, that is, their outlines get blurred with the environment, so it gets difficult for predators to find them.

Leptoglossus occidentalis (Coreidae), with their wide tibiae that look like leaves. Picture property of Giancarlodessi (CC 3.0).

Myrmecoris gracilis (Miridae), a clear example of ant-mimicry or myrmecomorphy. Picture property of Michael F. Schönitzer (CC 4.0).

• Some active mechanisms are 1) escaping, 2) biting, 3) the detachment of some appendices to confuse predators and 4) the emission of stink or irritating substances by their odoriferous glands, which in most of cases they acquire from plants they feed on. Others emit stridulating sounds.

Life forms and diversity

Even though most people know something about heteropterans due to the famous bed bugs, feeding on blood is far from being the only life form among true bugs.

• Terrestrial

Most heteropterans inhabit terrestrial environments, either on plants or on the ground as phytophagous (they feed on vegetal fluids) or predators of other insects. There are also some terrestrial heteropterans that feed on roots or on fungi that develop under tree bark. Some examples of terrestrial phytophagous families are Pentatomidae and Coreidae. Among predators, which use their stylet to inoculate proteolytic agents inside their preys to dissolve their content and then suck it, there are a lot of members from Reduviidae family.

• Aquatic and semiaquatic

Aquatic and semiaquatic forms have special adaptations to live in water, like hydrofuge hairpiles which repel the water. Most of them live in lakes and rivers, either on their surface (semiaquatic) or submerged.

Semiaquatic species usually have long legs and long antennae, which together with the hydrofuge hairpiles let them to stand on water. Water striders (Gerridae), which are very abundant in Europe, are a clear example of this life form.

Water striders (Gerris sp.). Picture property of Webrunner (CC 3.0)

Aquatic species usually have a pair of legs adapted to swim. A good example of this are the members of the family Notonectidae or backswimmers, which have the hind legs fringed for swimming.

Notonecta sp. (Notonectidae). Picture property of Jane Burton/Bruce Coleman Ltd. (link).

Despite living in water, aquatic heteropterans need surface air to breath, so they go out of water periodically. They present different strategies to absorb oxygen, such as swallowing air that goes directly to the respiratory or tracheal system through a siphon (Nepidae) or capturing air bubbles with their hydrofuge hairpiles (Nepidae). Other simply get covered of a tiny air layer using their hydrofuge hairpiles.

• Hematophagous

Finally, there are heteropterans that feed on blood and live as bird and mammal parasites. This is the case of the Cimicidae family (e. g. Cimex lectularius, the bed bug) and some groups of Reduviidae, such as the members of the subfamily Triatominae, which are also known for being vectors of the Chagas disease in the center and south of America (being Triatoma infestans its main vector).

Cimex lectularius or bed bug nymph. Public domain.

Triatoma sp. (Triatominae). Picture property of Bramadi Arya (CC 4.0).

Scientific interest

• They help to regulate some wood and crop pests, having an important role in integratative pest management. This is the case of some predator heteropterans from the Reduviidae, Anthocoridae, Miridae, Nabidae and Geocoridae families. However, some phytophagous heteropterans can act as pests too.
• They have been an interesting scientific model for the study of insect physiology.
• They are an important element on human diet in some countries, being Pentatomidae one of the most consumed families. Some aquatic heteropterans, such as Lethocerus sp. (Belostomatidae) are very appreciated as food in some Asiatic countries, like Vietnam and Thailand.

Lethocerus sp. Picture property of Judy Gallagher on Flickr (CC 2.0).

• Some of them are disease vectors or a cause of discomfort. The most classic example is the bed bug (Cimex lectularius), which has become a frequent pest in temperate regions; some Cimidae are also a threat for free range chickens and other farm birds. In America, Triatominae are vectors of different diseases, being the most famous the Chagas disease (transmitted by a protozoan, Trypanosoma cruzi).

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All organisms on Earth are necessary for some reason: you only need to investigate about them. Even the true bugs!

References

• Goula M., Mata L. 2015. Orden Hemiptera: Suborden Heteroptera. Revista IDE@ – SEA, 53: 1–30.
• https://www.britannica.com/animal/heteropteran
• Schuh R. T., Slater J. A. 1995. True Bugs of the World (Hemiptera:Heteroptera): Classification and Natural History. Cornell University Press.

Main picture property of Pavel Kirillov on Flickr, with license  Creative Commons 2.0. (link).

Animal mimicry: now you see me…

What do you see in the picture above? Maybe snakes… or maybe not? All animals try to enhance their survival rates, and one of the most effective ways to achieve this goal is by looking similar to some environmental elements, either by camouflaging or by imitating traits from other organisms. Mimicry is a complex and surprisingly phenomenon present in almost every animal taxa acting as an evolutionary driving force. Do you know what types of mimicry exist and which animals do perform each one? Are you ready to read more about this topic? If that’s the case, keep reading!

Mimicry vs camouflage (or crypsis)

The word mimicry (that derives from the Greek term mimetikos = “imitation”) was firstly being used to describe people who have the ability to imitate. From 1851 on, its use extended to other life forms.

Sometimes, the term mimicry is used as a synonym of “camouflage or crypsis”. Although these two words are sometimes confused and used equally, from a biological point of view they are well differentiated terms:

• Mimicry: the ability an organism develops to imitate one or more traits from another organism (with which it’s unrelated) so that it can obtain some benefit.

• Camouflage (or crypsis, from the Greek word kryptos = “hidden”): the ability an organism has to be unnoticed by its predators (or prays) by copying some environmental traits or by developing a disruptive coloration that allows it to hide.

Some authors consider that camouflage includes only to the ability an animal has for imitating morphological traits from some environmental elements, such as different natural surfaces, plants or even sessile animals (i.e. immobile animals) like corals and sponges (as you can see on the picture below). On the other hand, mimetic animals go further and try to imitate not only morphological traits, but physiological and behavioral, looking for a response from other animals.

Can you see the camouflaged seahorse? (Picture by Stephen Childs, CC).

To sum up: the main objective of mimetic animals is to trick the senses (e.g. sight, hearing, smell…) of the other organisms they live with, in order to induce them a specific behavior that gives mimetic animals a benefit in return.

Types of mimicry

There are different ways to classify the different types of mimicry, but I will show you two main groups of mimicry, in which we will see different subtypes: defensive mimicry and non-defensive mimicry.

Defensive mimicry

The defensive mimicry is specially performed by animals that have lots of predators, so their survival rates depend on avoiding their predators.

BATESIAN MIMICRY

Venomous and poisonous animals tend to develop flashy traits (especially flashy morphological traits, like coloration and menacing sounds) which alert other animals about their danger. This phenomenon is known as aposematism (when an animal has a flashy coloration we talk about aposematic coloration). In the Batesian mimicry, the mimetic organism (that is usually harmless and edible) copies the flashy traits of a venomous or poisonous organism present in its habitat in order to make predators think it’s a harmful species. Thus, the mimetic organism avoids being caught and eaten by predators.

Poisonous Coral Snake (on the left) and non-poisonous Scarlet King Snake or False Coral Snake (on the right). The second one imitates the aposematic coloration of the first one (Source: oakdome.com).

 

MÜLLERIAN MIMICRY

Sometimes, there are various poisonous or venomous species coexisting at the same time in the same habitat that are all being very hunted by predators (and sometimes by the same predator). In some of these cases, even when only one of these species has an aposematic trait to dispel predators, the rest of them try to mimic it and develop this trait (or traits). In contrast with de Batesian mimicry, in this model all species are harmful at some degree.

Try to think that all these species finally develop the same aposematic coloration: when predators prey on one of these species and are harmed in result, probably they won’t attack again any species that has the same coloration pattern. Thus, predation pressure will be distributed within the species matrix.

Different geographical forms of both Heliconius erato (top row) and Heliconius melpomene (bottom row). Heliconius melpomene is a widespread neotropical species well known for its geographic diversity in color pattern. Throughout its range, H. melpomene is co-mimetic with Heliconius erato (which is generally less abundant than H. erato). Both have a disgusting flavor when being eaten (source: heliconius.org).

 

MERTENSIAN MIMICRY

This is an unusual type of mimicry (only a few cases in snakes are known), and it occurs when a harmful species copies an aposematic trait (e.g. coloration) of a less dangerous organism. What could this mechanism be useful for?

In the picture above, we can see that predators that feed on a harmful organism die (e.g. because it’s poisonous), so that the information “this animal is poisonous and mortal, don’t eat it!” won’t be transmitted to the rest of the predator population nor the next generations of predators. Thus, this harmful prey will remain preyed by predators. On the other hand, predators that feed on a less harmful prey and stay alive will have the chance to transmit this information to the rest of the population, so that predators will stop feeding on this prey.

In light of this situation, what do the most harmful organisms do? they try to imitate the aposematic traits of less harmful organisms (like coloration or shape) so that predators that feed on these less harmful organisms and stay alive, learn that all organisms with the same traits are dangerous. So, the predation pressure will fall for all preys.

Non-defensive mimicry

One of the most important types of mimicry within the non-defensive mimicry is the Peckhammian mimicry.

AGRESSIVE OR PECKHAMIAN MIMICRY

Unlike defensive mimicry, in this case are predators (or parasites) the ones that develop the traits of a more or less harmless species (or even of a beneficial one) in order to be unnoticed by their preys or hostages.

Plagiotremus rhinorhynchos (on the right) is an aggressive mimetic species that imitates another fish known as Laborides dimidiatus or bluestreak cleaner wrasse. Plagiotremus rhinorhynchos (family Blenniidae) imitates youth specimens of Labroides dimidiatus (family Labridae) both morphologically and behaviorally. Many species of fishes enter corals in order to be cleaned from parasites by Labroides dimidiatus. Taking advantage of this situation, P. rhinorhynchos get close to these coral fishes by mimicking the bluestreak cleaner wrasse in order to feed on their tissues (Pictures: the left one by Karelj, CC  and the right one by JennyHuang, CC).

Aggressive mimicry can be confused with some camouflage or crypsis mechanisms, as sometimes these two terms can be overlapped or maybe show no evident differences. This is the case of some abyssal fish species which have one or more filaments of their dorsal fins transformed into lures (sometimes these lures are bioluminescent). These lures sometimes mimic the shape of the abyssal fish’s preys, so those preys feel strongly attracted by them. Some authors propose that preys could be the model organisms and that abyssal fishes would modified their dorsal fin through an evolutionary process.

Abyssal fish on a photogram from the film ‘Finding Nemo’ (© Pixar, 2003).

Abyssal fish…a way more real than the one showed above (with its luminescent lure) (Image source: http://www.bogleech.com/nature/).

A curious case: the automimicry

The automimicry (also known as intraspecific mimicry) is a special case of mimicry that takes place when an organism transforms some part of its body in order to seems like another part of its own body or even of the body of another member of its species (e.g. a male that mimics a trait from females). The objectives of this type of mimicry are to obtain some benefit from other organisms or maybe to be unnoticed by their predators or preys.

The northern pygmy owl (Glaucidium californicum) has two big dark spots behind its head which remind of two big eyes (picture by Michael Durham).

Mimicry makes animals to evolve!

Mimicry is one of the processes that makes animals to evolve faster (do you want to learn more about evolutionary processes? Enter this link!).

These changes may occur in a higher or lower speed. So, what about those animals that mimic other organisms? Mimetic animals are in constant selective pressure to look more like their models in order to go unnoticed and improve their survival, but at the same time imitated organisms (the models) are also under selection to sharp their ability to discern between models and imitators.

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Thus, mimicry is an incredible evolutionary engine: a perpetual struggle between mimetic organisms and imitated ones in order to improve their respective survivals.

REFERENCES

• Bone Q., More R. Biology of fishes. 3a ed. Taylor & Francis.
• Campbell, N.A., Reece J. B. 2007. Biología. Ed. Médica Panamericana.
• Cheneya K.L., N. Justin M. 2009. Mimicry in coral reef fish: how accurate is this deception in terms of color and luminance?. Behavoural ecology, Oxford Journals. Vol 20. P. 459-468.
• Harper D. Online Etymology Dictionary.
• Kashyap H. V. 2001. Advanced Topics In Zoology. Ed. Orient Blackswan.
• Sarmiento O.F., Vera F., Juncosa E. J. 2000. Diccionario de ecología: paisajes, conservación y desarrollo sustentable para Latinoamérica. Ed. Abya Yala.

Main picture source: www.yedirenkhaber.com.

Danger, poisonous mammals!

We usually associate snakes, spiders, jellyfish, etc. as venomous animals par excellence, but did you know that there are poisonous mammals? In this article we will discover who are they and the nature and use of their poisons.

THE PLATYPUS

The platypus (Ornithorhynchus anatinus) is the most famous among the poisonous mammals, and not just for this feature. With a peak like a duck and oviparous (laying eggs), when it was discovered some scientists thought it was a fraud.

Platypus (Ornithorhynchus anatinus). Photo by Jonathan Munro

They belong to the order monotremes, which means “one hole” in reference to the cloaca, the end of the digestive and reproductive systems. Some evolutionary biologists refer to them as the “missing link” between reptiles and mammals, as they have characteristics of both groups. Monotremes are the only mammals that lay eggs, but his body is covered with hair and the young are fed with breast milk. They are distributed by Australia, Tasmania and New Guinea.

Platypuses have a spur on the hind legs, which only in the case of males, release poison produced by femoral glands (located in the leg). The male uses it mainly to defend their territory and establish their dominance during the mating season, although if it is bothered also uses it as a defense. This poison can kill small animals, including dogs, and cause severe pain and swelling in humans. This pain can last days or months.

Spur on the hind leg of a platypus. Photo by E. Lonnon

Toxins are four proteins, three of which are unique to the platypus. They are like the defensins (DLP, defensin-like proteins). These are globular proteins, small and compacted, involved in the activation of pain receptors. Understanding how these toxins act it has special interest because they cause a lasting and severe pain; it may open new chances in the synthesis of analgesic drugs.

Short-beake echidna (Tachyglossus aculeatus). Photo de Tony Britt-Lewis

Echidnas (family Tachyglossidae) complete the order of monotremes with the platypus; consequently they are also oviparous. The family consists of four species, with the common characteristic of having the body covered with dense hair and spines. They are mainly insectivores specializing in ants and termites.

Like the platypus, they also have spurs behind the knees, but their secretions are not poisonous. The substances are used to mark their territory, according to the recent studies.

SLOW LORIS

As we saw in a previous post, lorises are primates in the prosimians suborder. They are nocturnal, arboreal and feed primarily on insects, vegetables and fruits. The slow lorises (Nycticebus) living in Southeast Asia, are the only poisonous primate. They possess poison glands on the elbows (brachial gland), and poison their body with arms and tongue, which can also join saliva and be transmitted by bitting.

Pygmy slow loris (Nycticebus pigmaeus). Photo by Ch’ien C. Lee

In this case the poison is used as a defense against predators, causing them pain, inflammation, necrosis (cell death) in the area of the bite, hematuria (blood in urine) or in some cases anaphylactic shock (allergic reaction) which can lead to death, even in humans (some are threatened by the illegal pet trade and traditional Chinese medicine). The poison also serves as protection for the young, they are licked by their parents and the poisonous secretion is distributed throughout the coat. Being poisonous, unusual among primates, can help counteract the disadvantages of its slow movements. Exudate from glands, as in echidnas, can also give olfactory information of range and territory between individuals of loris (Hagey et al., 2007).

Kayan loris (Nycticebus kayan). Photo by Ch’ien C. Lee

Toxins are polypeptides (generated when glandular secretion is mixed with saliva) and an unidentified steroid. Secretion is similar to the allergen Fel d 1 which is in the domestic cat and cause allergies in humans (Hagey et al., 2006; Krane et al., 2003).

It is believed that slow lorises even have converged evolutionarily with cobras, for his defensive behavior when threatened, whistling and raising his arms around his head. (Nekaris et. al, 2003).

Mimicry between loris and cobras. 1. Javan slow loris, 2 y 3. Spectacled cobra, 4. Bengal slow loris. Photo by Nekaris et. al.

In the following video a lazy lori is disturbed and hisses like a snake while trying to bite:

SOLENODON OR ALMIQUI

They are small and nocturnal mammals, basically insectivores, that live in the West Indies. The Hispaniolan solenodon (Solenodon paradoxus), also known as the Dominican solenodon, Haitian solenodon or agouta, lives on the island de La Española (Dominican Republic and Haiti) while The Cuban solenodon or almiqui (Solenodon cubanus) is distributed throughout Cuba. They are considered living fossils because they have similar characteristics to primitive mammals of the end of the Mesozoic Era (kingdom of the dinosaurs).

Hispaniolan solenodon (Solenodon paradoxus). Photo by Eladio M. Fernández.

Unlike other poisonous mammals, toxic saliva is produced under the jaw (submandibular glands), which is transported by pipes to the front of the mouth. The second incisor teeth have a groove where toxic saliva accumulates to promote their entry into the wounds. They are the only mammals that inject venom through its teeth, similar to the way snakes do.

Paradoxus Solenodon lower jaw incisor showing the groove. Photo by Phil Myers

The main function of this venom is to immobilize prey, as well as insects they can hunt small vertebrates such as reptiles, amphibians and birds.

Cuban solenodon (Solenodon cubanus). Photo by Julio Genaro.

This poison may have been developed to keep alive but immobilized prey during times of shortage, to aid in digestion, minimize energy expenditure in the struggle for hunting and face prey even twice as big as them. This venom is not deadly to humans.

SHREWS

The northern short-tailed shrew (Blarina brevicauda), the Eurasian water shrew (Neomys fodiens) and the Mediterranean water shrew (Neomys anomalus) also have submandibular glands similar to solenodons. They are distributed by North America (northern short-tailed shrew) and Europe and Asia (water shrews), including the Iberian Peninsula.

The northern short-tailed shrew (Blarina brevicauda). Photo by Gilles Gonthier.

The short-tailed shrew can consume up to three times its weight in food per day. Their saliva is the most poisonous and uses it to paralyze their prey, to eat them or keep them alive in times of shortage. The water shrews also store its immobilized prey under rocks.

Mediterranean water shrew (Neomys anomalus). Photo by Rollin Verlinde.

These animals attack from behind and bite the neck of its prey so that the poison acts more quickly, affecting the central nervous system (neurotoxins). The respiratory and vascular system is also affected and causes seizures, incoordination, paralysis and even death of small vertebrates.

Eurasian water shrew (Neomys fodiens). Photo by R. Altenkamp.

Its teeth don’t have grooves as the solenodons do, but a concave surface to store the toxic saliva.

Lower jaw of Neomys anomalus. Photo by António Pena.

It is suspected that other mammals also produce toxic saliva similarly, as the European mole (Talpa europaea) and other species of shrew, but there are no conclusive studies.

MANED RAT

The maned rat or crested rat (Lophiomys imhausi), lives in Africa and  uses his poisoned hair to protect themself from predators.

Maned rat (Lophiomys imhausi). Photo by Kevin Deacon

Unlike other mammals that produce their own poison, the crested rat gets toxin (called ouabain) from the bark and roots of a tree (Acokanthera schimperi). Chews the bark and the mixture of saliva and toxins are distributed on the body. Their hairs are cylindrical whith a perforated microscopic structure, which favors the absorption of venom. In case of danger, it bristles and shows his brown coat with white stripes, warning of its potential danger. This strategy of persuasion based on brightly colored warning is known as aposematism present in many animals, such as bees.

In this BBC video you can see a crested rat and a hair under the microscope absorbing ink, showing its porous structure:

It is unknown how it is immune to the toxin, since it is the same substance used by some African tribes for hunting such large animals like elephants.

Ouabain is a glycoside which controls the heartbeat, causing infarcts if absorbed in large quantities. The study of the mechanisms that protect the crested rat of a substance that regulates the heartbeat, can help develop treatments for heart problems.

European hedgehogs (Erinaceus europaeus) have similar behavior (smearing the body with foreign poison), but it is not established whether the objective is defensive because it does not scare away predators.

In conclusion, strategies, practices and nature of the poison in mammals are varied and their study may have important medical implications for drug development and increase awareness of the evolutionary relationships between different groups of living animals (reptiles-mammals) and their ancestors.

REFERENCIAS

• Platypus poison
• Scientists discover the function of the echidna’s spur
• Los primates venenosos existen
• El único primate venenoso del mundo ya no está solo
• “Venom” of the slow loris: sequence similarity
  of prosimian skin gland protein and Fel d 1 cat allergen
• Venomous Slow Loris May Have Evolved To Mimic Cobras
• La rata que se unta con veneno para defenderse
• ¿Es cierto que los erizos se embadurnan de veneno?
• Pequeños pero feroces: mamíferos venenosos
• Are slow lorises really venomous?
• Encuentro con un “fósil viviente” en R. Dominicana
• Imagen de portada de Dave Watts

Maratus sp.: The spider that wants to be a peacock

If I told you that there exists a 5 millimeters Australian peacock, would you believe me? Although we can find a large number of incredible animals in this country, scientists haven’t yet discovered such a small bird. However, we can find a small peacock-like animals: the peacock spiders (Maratus sp. Salticidae Family, also known as jumping spiders), whose ‘abdomen’ or opisthosoma (the posterior part of the body in some arthropods, including arachnids) have a flap-like extensions that they can unfold to the sides of its body as real peacocks do.

The last month we introduce you these organisms at our different websites (Facebook and Twitter). Through this article, you will learn its most relevant characteristics and you’ll find out the hidden function of its drop down opisthosoma.

JUMPING SPIDERS

Peacock spiders are a part of Salticidae family, whose members are also known as ‘jumping spiders’. This family has up to 5000 species (probably, they form the largest and diverse group of spiders known nowadays), and they’re located all over the world (they can be found even at the top of Mount Everest; this is the case of Euophrys omnisuperstes). Even so, most of them inhabit tropical forests.

¿HOW CAN WE DISTINGISH THEM FROM OTHER SPIDERS?

MAIN TRAITS

Usually, spiders from Salticidae family get to be a size of few millimeters as adults (normally they don’t exceed 10mm long). From an anatomical point of view, the members of this group are characterized by its two big, simple front eyes flanked by two smaller ones, plus four eyes more located over them. The size and the position of these eyes give them an excellent vision in comparison with other spiders, and even compared to other group of arthropods its vision is extraordinary.

Look at these big eyes! Can you resist them?

Specimen of Paraphidippus auranticus (Picture by Thomas Shahan (c)).

Besides its excellent vision, these organisms have the ability to cover a distance of 50 times its length in one jump, because of what they received the nickname ’jumping’. Thus, their ability to travel long distances in just one leap and their extraordinary vision are the main traits that make these spiders being excellent predators: they hunt by stalking their prey without making spider webs or silk traps. Moreover, some of their legs tend to be longer than the others, letting them to catch preys way better.

Jumping spider predating a specimen of Diaea evanida or pink flower spider (Picture by James Niland on Flickr, Creative Commons).

Spiders of this family usually present a noticeable sexual dimorphism (that is, remarkable physiognomic differences between males and females). Jumping spider males have bigger oral appendixes (or pedipalps) than females, which they use during mating dance and copulation as much for attracting the attention of females as for giving females their spermatophore (capsule or mass containing spermatozoa) during mating.

Sitticus fasciger male (with dark big pedipalps) (Picture by sankax on Flickr, Creative Commons).

Sitticus fasciger female (Picture by sankax on Fickr, Creative Commons).

In addition to these developed pedipalps, males of some species of jumping spiders have a colorful, and even iridescent, opisthosoma (the posterior part of the body in some arthropods, including arachnids). Some of them even have an opisthosoma that can reflect UV radiations which are detected by females thanks to their extraordinary vision (as some studies suggest). In contrast, females use to be more cryptic or darker colored than males (but not always).

Male (right) and female (left) of Maratus mungaich. Male has a blue and red colored ‘abdomen’ or opisthosoma (Picture by Jurgen Otto on Flicker, Creative Commons).

The flashy opisthosoma of males attracts the attention of females, and this is complemented with mating dances composed by different dance moves: they vibrate their opisthosoma and their pedipalps or move their anterior legs, they move from one side to the other, etc. Usually, these mating dances tend to be very complex.

NOW, JUST AS A MATTER OF INTEREST…

There exist some jumping spider genera that mimic ants. This phenomenon is known as ‘myrmecomorphia’, term used to describe the fact that some animal imitate ants or also the organisms that accomplish the mimic (‘myrmecomorph’).

Some of the most famous species resembling to ants are inside the Myrmarachne genus.

Specimen of Myrmarachne sp. (Picture by Jean and Fred on Flickr, Creative Commons).

With this example, and what has been explained above, it becomes clear that the Salticidae family is a very diverse group at various levels.

MINIATURE PEACOCKS: THE PEACOCK SPIDERS

At the end of XIX century, the reverend and zoologist Octavius Pickard-Cambridge, who loved spiders, discovered a surprising organism: a small spider just over 5mm whose males have a flamboyant opistosoma.

Maratus volans male (Foto de Jurgen Otto a Flickr, Creative Commons).

According to this definition, there seems not be any difference between jumping spiders and these new organisms. But the true is that these miniature spiders have an ace in the hole: the opisthosoma of males has lateral and flexible flap-like extensions that they can unfold like wings to the sides of their bodies and over their prosoma (that is, the anterior part of the body in arachnids). Finally, when its function ends they can be folded again.

‘Abdomen’ or opisthosoma of a Maratus mungiach male (1,2,3-Different degrees of expansion of the lateral flaps) (Otto and Hill, 2011).

So, due to its colored and expansible opisthosoma this new spider was named ‘peacock spider’.

Probably, the most famous peacock spider is Maratus volans, one of the first species called as ‘peacock spider’. To date there have been identified up to 30 species of peacock spiders, and each presents subtle variations in the patterns of its opisthosoma. All of them are included in Maratus genus, whose members (but M. furvus) are endemic to Australia. Moreover, Jurgen Otto and David Hill have recently identified two new species of the Maratus genus in Queensland: Maratus jactatus and Maratus sceletus.

Maratus amabilis male (Picture by Jurgen Otto on Flickr, Creative Commons).

Maratus harrisi male (Picture by Jurgen Otto on Flickr, Creative Commons).

Maratus volans male (Picture by Jurgen Otto on Flickr, Creative Commons).

Although in the beginning it was been suggested that these flap-like expansions let them fly (because of what they were called ‘flying peacock spiders’ at first place), later studies revealed that these expansions have a more ‘romantic’ function. Let’s discover it in the next section.

A SURPRISING COURTSHIP

As well as male peacock do when they see a female, these Australian spiders use their opisthosoma in order to impress the females during courtship (that usually takes place on september-november).

Throughout this process, males perform a mating dance which is a little different from the ones performed by other jumping spiders: at the first place, they make vibrate their opisthosoma and their pedipalps; then, they raise their third pair of legs and shake them vigorously in order to attract nearby females; finally, they raise their opisthosoma and unfold the lateral flap-like extensions showing its colored pattern. Then, they make vibrate their opisthosoma to show its iridescence and they begin to move from one side to the other while shaking their legs.

But, as everybody knows, an image is better that any word, so I invite you to see the next video (made by Jürgen Otto) where you can see a male of Maratus volans dancing for his ladies:

As you have been able to appreciate while reading this article, two animals that belong to a not related groups (peacocks and spiders) have developed a quite similar courtship strategy. And it seems to yield good results in both cases. Nature is surprising us again!

 

REFERENCES

• Lim M.L.M, Li D. (2005). Extreme ultraviolet sexual dimorphism in jumping spiders (Araneae: Salticidae). Biological Journal of the Linnean Society 89: 397–406.
• Otto J.C., Hill D.E. (2015). Two new peacock spiders of the calcitrans group from southern Queensland (Araneae: Salticidae: Euophryinae: Maratus). Peckhamia 121.1: 1-34.
• Otto J.C., Hill D.E. (2014). Spiders of the mungaich group from Western Australia (Araneae: Salticidae: Euophryinae: Maratus), with one new species from Cape Arid. Peckhamia 112.1: 1-35.ç
• Otto J.C., Hill D.E. (2011). An illustrated review of the known peacock spiders of the genus Maratus from Australia, with description of a new species (Araneae: Salticidae: Euophryinae).
• Salticidae, Jumping spiders.
• Two New Species of Peacock Spiders Discovered in Australia. Sci-knews.com.
• The extraordinary courtship dance of Australia’s peacock spider. The Guardian.

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