U is for Ultraviolet Fluorescence

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As a part of the A-Z Photographic Glossary of Biological Terms challenge, today it is U for Ultraviolet Fluorescence as illustrated by this pair of Brown Bark Scorpions (Centruroides gracilis; Butidae; female below, male above) photographed under UV light, from the Sittee River Wildlife Reserve, Stann Creek.

With the exception of some species of the family Chaerilidae, as far as is known all other species of scorpion fluoresce under UV light.

Scorpions are nocturnal animals, feeling vulnerable in the daylight. When exposed to ultraviolet (UV) their exoskeletons glow blue-green, but scientists aren’t exactly sure why. There are a number of theories but the consensus now seems to be that their glow helps scorpions find shelter in their dark environments.

While we normally associate UV light with daylight, the rays responsible for tans and sunburn, at night a certain amount of UV light is reflected off the sun onto the moon (the moon’s glow is “borrowed” light) and can fluoresce scorpions that are exposed in the open at night.

This pointed the way for a team at the University of Oklahoma, led by Doug Gaffin, to investigate what happened when scorpions’ eyesight was blocked in the presence of UV light. The results of their work showed that fluorescence under UV light helped scorpions detect whether they were under shelter or exposed at night. They determined that their exoskeleton functions as a whole-body photon collector allowing scorpions to detect shelter.

The same female Brown Bark Scorpion pictured above, but in normal light:

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and the the male under normal light:

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T is for Thermogenesis

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As a part of the A-Z Photographic Glossary of Biological Terms challenge, today it is T for Thermogenesis as illustrated by the Sacred Lotus (Nelumbo nucifera), photographed in the National Aquatic Gardens, Washington DC.

Quite simply put, thermogenesis is as the etymology suggests, the creation of heat, and in the natural world we associate that process with warm-blooded animals like humans and other mammals and with birds that can maintain a stable body temperature by regulating metabolic processes. However, in our example today we find that certain plants like the Sacred Lotus as well as many in the arum family (Araceae) possess this ability too.

In the case of the lotus, the process of thermogenesis and thermoregulation (keeping the temperature stable) takes place in the flowers. Temperatures inside the flowers generally remain between 30-36°C (86-96°F) despite changes in environmental temperatures between about 10-45°C (50-113°F). Thermogenesis begins in the bud, when the petals are tightly closed, continues through a day when the petals open slightly to reveal the stigmas, and ends as the flower opens widely to expose the stamens and this period of thermogenesis and regulation coincides with when the flower is most receptive to pollination.

There is some evidence to show that this strategy might be a reward to insect pollinators that would benefit from a high body temperature while remaining in the flower.

S is for Sequential, Serial bidirectional, and Simultaneous Hermaphroditism

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As a part of the A-Z Photographic Glossary of Biological Terms challenge, today in fact we have three terms! S for Sequential hermaphroditism, S for Serial bidirectional hermaphroditism, and S for Simultaneous hermaphroditism as illustrated by the Creole Wrasse (Clepticus parrae) and the Indigo Hamlet (Hipoplectrus puella), from Bonaire in the Dutch Caribbean.

In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both partners can act as the “female” or “male”.

Such is the case with reef fishes in the Caribbean. The most common form is the “sequential hermaphrodite” when a fish is born one gender then changes to another- this could be what is termed “protandry” (proto -first, androus -male) where the fish is born as a male and then changes sex to a female, such as the Snook (Centropomus undecimalis); or as “protogyny” (proto -first, gyno -female) where the fish is born as a female and then changes sex to a male, such as wrasses, parrotfish, and groupers. Protogynous sequential hermaphroditism is the most common form and occurs in about 70% of all reef fish- and of course an important consideration here is that when fishing is allowed to harvest increasingly smaller fish (ie. mostly females) this practice will seriously adversely affect population reproduction and recovery.

With this Creole Wrasse (Clepticus parrae) pictured above, the initial phase is made up exclusively of females who change into terminal males when they reach a length of about 6 inches; this individual has just started to change from the all blue female, and the increasing yellow color will soon be joined by lavender, orange and magenta when it is finally male.

There are some fish that possess both male and female organs and engage in “serial bi-directional” sex change, where a species is capable of switching back and forth between male and female depending on the situation, as is the case with many species of goby.

Then there is another form called “simultaneous hermaphroditism” as exemplified by the Indigo Hamlet pictured below. All the hamlets are unique in that they too possess both male and female organs simultaneously but when one discovers a mate it can choose which role to play; in most cases pairs take turns between which one acts as the male and which acts as the female through multiple matings!

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R is for Repugnatorial Gland

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As a part of the A-Z Photographic Glossary of Biological Terms challenge, today it is R for Repugnatorial gland as illustrated by this Desert Stink Beetle (Eleodes sp.; Tenebrionidae), from the Franklin Mountains State Park in El Paso, Texas.

Repugnatorial glands are also described as “stink glands” or “odoriferous glands” or more properly “ozadenes,” from which an arthropod (primarily insects and myriapods) can emit a foul-smelling and often toxic secretion or vapor, used in defensive situations to repel predators.

In this example, the Desert Stink Beetle will often stand on its head to allow for a more effective spraying of its noxious secretion however certain of their predators, like Grasshopper mice who are already adept at disabling venomous scorpions and centipedes, get around this problem by grabbing the beetle, jamming its behind into the sand, and then eating it head first, similar to this mouse’s strategy when dealing with a scorpion.

Now based in Belize, there are a number of arthropods here that utilize repugnatorial glands including many species in the Pentatomidae family of stink bugs like this one (probably Peromatus sp.) found in Unitedville, Cayo District

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and this polydesmidan (“flat-backed”) millipede found in Alta Vista, Stann Creek District, which secretes hydrogen cyanide gas to both deter predators (including humans!) and knock their prey dead!

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Q is for Queen

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A-Z Photographic Glossary of Biological Terms challenge!

Just like the letter J, finding a biological term starting with Q proved to be rather difficult, and using a wildlife photo to illustrate either an elementary particle within a neutron (quark) or the structure of certain proteins (quaternary) is pretty much impossible!

So today it is Q for Queen as illustrated by this Queen Angelfish (Holacanthus ciliaris) from Bonaire in the Dutch Caribbean, “All Hail the Queen!”

This angelfish gets its name for the “crown” visible on its forehead; although quite large (this one was about 15″ long) they are quite shy, emerging from behind branching corals when defending their territory or in search of the algae and sponges that make up most of their diet; they also feed on tunicates, jellyfish, and corals as well as plankton. Juveniles serve as “cleaners” and feed on the parasites of larger fish at cleaning stations.

The adults are found in pairs year round forming long-term monogamous bonds. The pairs reproduce by rising up in the water, bringing their bellies close together, and releasing clouds of sperm and eggs. The female can release anywhere from 25 to 75 thousand eggs each evening and as many as ten million eggs during each spawning cycle. The eggs are transparent and buoyant and float in the sea, hatching after about 15-20 hours into larvae and about 48 hours later, having absorbed their yolk sac, the larvae develop the normal characteristics of free swimming fish and start to feed on plankton. The larvae grow rapidly and about 3–4 weeks after hatching the 2cm long juveniles settle on the bottom.

P is for Photoreceptor

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As a part of the A-Z Photographic Glossary of Biological Terms challenge, today it is P for Photoreceptor as illustrated by this male Eastern Carpenter Bee (Xylocopa virginica) from Maryland in the US.

“I’ve got my eyes, all five of them, on you!” This bee does indeed have five eyes: three ocelli (simple or single lens) which provide information on light intensity; and two compound eyes. Compound eyes are the principle visual organs of most insects; they are found in nearly all adults and in many immatures. As the name suggests, compound eyes are composed of many similar, closely-packed facets called ommatidia which are the structural and functional units of vision. The number of ommatidia varies considerably from species to species: some worker ants have fewer than six while some dragonflies may have more than 25,000. Each omatidium contains a photoreceptor cell which refracts incoming light down onto visual pigment which in turn absorb certain wavelengths of light and generate nerve impulses through a photochemical process similar to that of vertebrates and within a few milliseconds, sends it’s view of the image to the brain of the bee.

The brain combines all the images of these thousands of photoreceptor cells and forms a detailed picture of it’s subject in a sort of mosaic composition. Since insects cannot form a true (i.e. focused) image of the environment, their visual acuity is relatively poor compared to that of vertebrates but with each of these thousands of photoreceptor cells sending images to the brain, their ability to sense movement, by tracking objects from ommatidium to ommatidium, is superior to most other animals.

For more detailed information of photoreceptors in insects, take a deep breath and then jump into this article from North Carolina State University.

O is for Opisthoglyphous

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As a part of the A-Z Photographic Glossary of Biological Terms challenge, today it is O for Opisthoglyphousas illustrated by this pair of Small-spotted Cat-eye Snakes (Leptodeira septentrionali polysticta; Colubridae) from the Sittee River Wildlife Reserve in Stann Creek District, Belize.

The common name, Cat-eye, comes from this beautiful snake’s vertical pupils. It is a semi-arboreal species and a mildly venomous hunter of frogs and toads and their eggs and tadpoles. Bearing in mind that all snakes, in fact all wild animals, should only be handled in very specific circumstances and only by someone with the proper experience and expertise, this is a very calm and docile animal when being handled.

It poses very little threat to humans because unlike the venomous elapids (including coral snakes) with forward-grooved fangs (proteroglyphous) and the venomous vipers (lanceheads like the Fer-de-Lance, rattlesnakes, bushmasters, and pit vipers) with pipe-grooved fangs (solenoglyphous), this species is what is known as “opisthoglyphous” or rearward-grooved.

In opisthoglyphous snakes, their venom is injected by a pair of enlarged teeth at the back of the jaws which normally angle backwards and are grooved to channel venom into the puncture. Since these fangs are not located at the front of the mouth this arrangement is vernacularly called “rear-fanged”. In order to envenomate prey, an opisthoglyphous snake must move the prey into the rear of its mouth and then penetrate it with its fangs, presenting difficulties with large prey, although they can quickly move smaller prey into position.

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