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The Revelation of Gustavo

The Revelation of Gustavo

Gustavo and his horde of relatives invaded Nectandra Reserve completely undetected.  What snagged our attention was the defoliation of one tall Wercklea insignis tree (related to the Hibiscus family) with the dinner-plate size leaves.  Under subterfuge, Gustavo and clan were eating the foliage nightly, but vanished by daylight.  At first, the consumption was insignificant but gradually increased exponentially. Over the next two weeks, the culprits had become veritable feeding machines.  The leaves were mowed at an astounding rate each night, but now the thieves were leaving an impressive amount of droppings on the ground by morning. Caterpillars! Judging from the size and appearance of the frass (insect poop), we knew they were from large moths, but which moth? There are some 5000 known ones in Costa Rica. Flightless, how could caterpillars disappear so completely each night? Easy. Hide in plain sight.

Once fingered, our caterpillars were spotted even in daylight.  I felt utterly foolish and blind for missing them in the first place. There were many dozens of caterpillars of the same species, large as cigars, all aligned and with the exact coloration of the tree trunk! Immobile after their nocturnal feeding frenzy high up near the canopy, their striking tentacles were like beacons once we knew what to look for. Intrigued, my co-worker decided to adopt three selected specimens from the dozens. We wanted to follow the development to the end of their metamorphosis to identify them. Moths are identified morphologically from the adult and not the caterpillar stage. After transferring them to a large plastic container, the caterpillars were presented with fresh Wercklea leaves each night. Then we watched.

Naming the study subjects is a double-edged sword — a no-no among scientists for fear the anthropomorphism would cloud the observers’ judgment — but we couldn’t help ourselves. The handsomest of the three, we named Gustavo.  He was already 10 cm in length (4in) not including his impressive head gear when we spotted him. He had 4 pink-black-white banded head tentacles on his head and one black-tipped pink (absolutely charming) curlicue on the tail segment.  The photo of Gustavo below was taken on the first day (D1) of our study. Judging by its large size, Gustavo was probably already nearly full-grown.

We also chose two other fellow caterpillars to hedge against mortality during captivity. Jorge (right upper in photo below) was chosen because he had one distinctive broken left-head tentacle and Freddy was smallest in size. We needed a way to tell them apart.

By Day 11, Gustavo grew only slightly, but his spots were lighter in color, larger, sharper and more noticeable. 

Left. Gustavo on D11 Right upper. Jorge with a broken tentacle
Right lower. Freddy

Four days later, D15, Gustavo shed its cuticle (skin) with the tentacles attached.  He now looked very different. Its retractable head was beginning to enlarge, his spots fused and the triangular green patches faded. He was also acquiring a layer of fine facial hair.  Jorge and Freddy in the meantime had not yet molted (photos below).  The typical moth or butterfly sheds its skin 4-5 times.  The stage in between each molt is known as an instar.  The fourth or fifth instar is usually the final instar before it turns into a pupa if it is a moth, or chrysalis if it is a butterfly.

Things were now moving faster. By D18, Gustavo and Freddy were no longer eating. Both were shrinking in girth and length. Only Jorge still had his tentacles, was still feeding and growing. 

The photo of Gustavo on D27 revealed the classic body of caterpillars (next photo). First the head on the left is connected to the thin 3-segmented thorax, behind which is the thicker 10-segmented abdomen. The first three thoracic segments have three pairs of pointy, true legs, one pair per segment. These true legs help position the head while rasping the leaf during feeding. Thoracic segments 3,4,5,6,10 are equipped with pairs of prolegs (not jointed as the true legs). The muscular prolegs are equipped with clawed hooks for grasping. Anyone who has tried to dislodge caterpillars from their food plants knows how tenaciously the subjects can cling to the leaves.

Caterpillars have six single-lens eyes on each lower side of the head. These eyes can sense light intensity but do not form images. For respiration, they have a system of internal tubes and valves that end in spiracles (valves) on each side of the thoracic segment for gas exchanges (black dots in photo above visible on each segment). Inter-caterpillar communication is by deposition and emission of chemical trails. The caterpillars’ sensitivity to plant aromatics is incredibly efficient. I once witnessed a coordinated U-turn by a pack of 3 dozens caterpillars within seconds after I introduced fresh food plant within 15 cm (6 in ) of the lead caterpillar.

The next photograph (D27) below show the variation among their siblings not in captivity, still clinging to the tree. The narrow range in size indicated they were likely all hatched from eggs laid about the same time. Note the individual coloration and markings that allowed them to blend in the tree trunk —another example of the art of concealment mentioned in my previous blog. After all, they are sitting “ducks” at this stage, completely vulnerable to predation from birds, bats and parasitoid insects.

D 27. Wild cousins of Gustavo on the tree branches

The formation of the pupae was pretty mysterious. Gustavo stopped feeding altogether shortly after D28. By D47, it has shrunk and hardened, but still with recognizable segments and prolegs. The photo below shows all three in the prepupa stage: Jorge was still caterpillar in form, whereas Freddy has started to pupate. Gustavo is still shrinking. By this point, the caterpillars had consumed enough nutrients and conserved enough water to last them through a complex series of transformation events to reach the terminal moth stage, most of which are not yet fully known.

The next image shows all three on D67. Gustavo was clearly a pupa showing hints of internal structure underneath the translucent exoskeleton, Freddy in the intermediate and Jorge in the semi-pupa stage.

At this point, not knowing the identity of our subjects meant we had to guess how to maintain the three pupae alive. Moth pupae are of two types: 1) naked pupae, usually found among leaves or soil or 2) in silk or spun cocoon. Since ours were of the first type, we put them in individual pots of loose soil and leaves. We then waited, and waited, and waited…

A full eight months later in October, resplendent Gustavo slowly and carefully emerged from the 5 cm pupa. Finally, we know what it is — a moth in the Saturniidae family, Arsenura batesii .

Gustavo emerged

Gustavo had an impressive 13 cm (5in) wing span. Its body and wings were elegantly and spectacularly furry. The hair on moths are not truly hair, but modified scales that are also found on butterflies. The scales serve multiple functions, for thermoregulation, sex appeal, camouflage, and as expendable body structures during attacks. Nocturnal predators such as bats have been known to end up with mouthful of fur but not the prey.

This is where the decision to name our study subjects comes home to roost. Gustavo should have been named Gustava, a female, based on the thread-like antennae. The roving male saturniids have complex, feathered antennae, better to sniff out the mostly stationary, pheromones advertising females. Saturniids moths do not eat and have reduced mouth-parts. They only need to stay alive a couple of weeks — long enough to find a mate, and lay their eggs.

What is the benefit of metamorphosis? The most obvious is that the caterpillar and the adult moth occupy totally different niches. No competition between the old and the young. The two use different food sources, are totally different in forms, locomotions and phase duration. They are not subject to the same risks and vulnerabilities.

Our little exercise revealed only the stages between the last instar and pupa. We were not privy to the mysterious events behind the exoskeleton of pupae before moth emergence. The totally cloaked metamorphic events are just beginning to be unraveled. Thanks to micro-CT scanning adopted for the purpose of imaging interior events, we soon will have much more information of this astounding process.

It took us nearly a year’s observation to document one single caterpillar-moth pair. Imagine the colossal work of Dan Janzen (U of Pennsylvania) on 9000 moths in the last three decades in Costa Rica, not just their biology (photo below), but also DNA barcoding for final identification .

Dan Janzen’s investigations on moth metamorphosis, using plastic bags housing for caterpillars with their food sources. The photo was taken in one of Dr.Janzen’s several growing sheds in Guanacaste, Costa Rica, on my visit in 2011.
Curious Tidbits on Cloud Forest Superbirds

Curious Tidbits on Cloud Forest Superbirds

Brrrrr…. It’s 52 °F in our cloud forest this morning. Not cold by northern-latitudes standard, but downright frigid for the tropics, especially for the two dozen species of Nectandra hummingbirds (of some 50 in Costa Rica).

Imagine the challenge in thermoregulation for an average size (4 in) hummingbird such as the Rufous-tailed hummer pictured below with a body weighing as little as a single grape (0.18 oz).

As most birds, it must maintain body temperatures between 100-108 °F to stay active.  For these birds, foraging for food means to be able to keep heartbeats around 1200 beats/min to sustain wingbeats of 50-70/sec to fly at average speed of 34 mph.  This flight ability allows the hummingbirds to hover about the flowers for nectar during feeding, and even to fly backward — unique acrobatic locomotion among avifauna.  (Human: 60-100 heartbeats/min and jogging speed of 4-6 mph )

Anatomically, the hummingbirds have the largest relative heart to body size.  The rufous-tailed’s heart constitutes 2.4% of its body weight (compared to ~0.5% of average human ).  Its need for oxygen during flight translates into higher red blood cell density of 6.59 million/ml (~5 million/ml for humans).

To stay fit, hummingbirds must eat and drink a lot  — more than half its body weight each day in nectar and twice in water, the equivalent of some 1000 flowers/day (favorite examples among many blossoms at Nectandra in photos below).  

Top left to right: Columnea microphylla, Guzmania spp, Sobralia virginalis
Bottom left to right: Elleanthus robustus, Justicia aurea, Besleria notabilis

Critical protein, fat and mineral supplements come from small insects, fruit flies, spiders, larvae, insect eggs, etc. (examples on Sobralia orchid, photo top right).  These food items are extra-critical during egg laying and feeding of average clutch of two young birds (when the mother birds themselves do not eat).

In addition to the extra caloric need during motherhood, some hummers must store fat (about 0.1 oz), enough for 24-26 hr of long flights (longer than the 22 hr limit for Boeing 777 non-refueling flight).   For example, the Ruby-Throated hummingbirds migrate across the 500 miles Gulf of Mexico.  They can clock at 25 mph or 650 miles maximum, enough to cross the Gulf of Mexico non-stop with energy to spare.  Rufous hummingbirds can migrate 1865 miles (with stops) between Mexico and Alaska/Canada.

The high metabolic rate creates interesting physiologic challenges. For one, the high caloric intake must be metabolized, channeled and expended fast enough not to overheat. As result, the hummingbirds have vastly efficient sugar digestion, increased tissue gas transport and matched respiration rate. To give an idea of what it takes to achieve the same high level of metabolism, an average human would have to consume 100 lb. of pure glucose per day.  The corresponding human metabolism, however, would generate lethal body temperature equivalent to ~752 °F .

The tiny-bodied hummingbirds must work at marginal and exquisitely tuned energy balance.  For example, to counteract the risk of overheating, hummingbirds do not have down feathers, even for those in the temperate-zone during winters. Instead, they rather conserve energy over long period, as during sleep, by going into a short hibernation state known as torpor — a lowering of body temperature to a steady minimum of around 60-70 °F, dropping 60-90% of its metabolic rate and >30% water loss in this torpor state. 

Hummingbirds, in sum, are superbirds. Their rapidly adjusting metabolic rates, the highest of any animals, allow them to withstand great ambient temperature swings. They may be the smallest but have the largest heart, the greatest appetite and the sweetest tongues.  They can fly the fastest and longest, besting the newest and longest range jet plane without refueling.  They can hover and fly backward like no other, birds or machines.

Most of all, hummingbirds are undeniably among the most beautiful of birds with their flashy, iridescent plumage.  Their feathers are wonders to behold — a topic worthy of another conversation.  Please join me on a eye opening chin-to-tail hummingbird feather inspection in the next blog.

The Art of Concealment

The Art of Concealment

By recent estimate, there are at least 500,000 fauna species in Costa Rica, of which 493,000 are invertebrates (insects, spiders, molluscs, crustaceans, crabs).  By comparison the entire US has fewer than one third the number of invertebrate species but 300X the land size of tiny Costa Rica — an effective difference of 1000 fold.

Most visitors to Nectandra Reserve have heard about the extraordinarily high biodiversity of the wet montane cloud forest.   On arrival, they expect to see a tropical jungle, teeming with animals and hopping with insects, in full view as in a zoo without cages.  Yet, all they see is the lush, thick, tangled, green vegetation behind the mist. They see few things with legs or wings, certainly not in a number or density that would impress. 

Puzzled, my visitors would politely ask “Do you have any animals?” As their guide for the day, I never get tired of seeing their eyes gradually widen in the course of our interpretive hike as they slowly realize the beauty of nature’s astounding subtlety.  It isn’t the quantity or furriness, but the compelling impact of the sightings that will convince them there is more to it than meets the eyes. By the time they leave, most visitors can grasp the phenomenal biodiversity with minimal help from me. Yes, the animals are here, thousands of them.  Many are in plain view, but only if our mind is prepared for the encounter.  One such example is captured in the photo below of a small fallen branch on the ground.

With so many animal species living in the same space, they become interdependent in a most efficient but cruel way possible.  Every species is food for other species.  To survive, every prey’s overpowering instinct is to hide, physically or visually, or both.  One most obvious way to conceal is to stay in the dark, and out of sight.  This is true for the smallest to the largest, from gnats to jaguar.  That explains why the majority of the invertebrates, reptiles, amphibians and mammals are nocturnal.   For many of the diurnal organisms, invisibility through camouflage — the ability to blend in the surroundings — is vital to survival. 

Let’s go back to the photo above. Look again with these three clues: 1) It’s in the left half of the photo, 2)  It’s in a patch of leafy plant,  3)  It’s green with 6 legs and two long antennae.  Still not visible?  If not, inspect the blow-up below of the same photo.  A katydid (Haemodiasma spp) is now revealed, perfectly camouflaged in the patch of liverwort, a cousin of the mosses. The next photo is an even closer shot of the head.

Close-up of head of katydid Haemodiasma spp

Not to be outdone, other members of this Tettigoniidae family (katydids, grasshoppers and crickets) are equally remarkable in the myriad of ways they can blend into their environment.  Take this close up photo of a dry leaf for example.  Note the pigmentation, the areas of discoloration, the flecks of tissue damage and randomly attached green vegetation. How faithfully would you guess a katydid can imitate this leaf ?

The answer is — absolutely perfectly — because the above “dried leaf” is actually a cropped view of the leaf katydid below.

Here is another example of the high art of concealment of another species of katydid. The green leaf katydid on the left is almost perfectly matched to the begonia leaf on the right.

The fierce competition for food sources in the wild tropics means every organic and proteinaceous scrap is consumed almost instantly.  Nothing is left to waste. Carcasses are rare finds.   The next photo is of such a rare item — a pair of wings from a dismembered katydid. 

A pair of detached leaf katydid wings

At first glance, when found on the ground, they were indistinguishable from the other dried leaves nearby.  On inspection, however, that they were of two perfectly mirrored “leaves”, including discoloration and holes, left no doubt they were not of natural leaves.  The symmetry was too perfect, the ribbing and veining (see photo below), even down to every blemish.  Had we found only one wing, only a biochemical or DNA test could confirm its insect origin.

As perfect as the cryptic coloration of the katydids (at least to the human eyes), one false move is all it takes to become someone’s meal. Witness, in the photo below, the unfortunate katydid that came too close to the spider web of the orb weaver Eriophora fuliginea. In spite of the size difference, the larger katydid was no match for the stickiness and strength of multi-stranded spider silk. It was all over for the katydid within mere seconds.

Concealment as a defense tactic comes in as many forms as there are organisms. Nature is an infinitely large repository of supremely clever solutions for as many problems. It behooves us humans to learn from them.

Please join us at Serendips.net next month for more adventures and examples.

Parachutist’s views of the Nectandra Cloud Forest

Parachutist’s views of the Nectandra Cloud Forest

I am inaugurating this blog series with a virtual visit to Nectandra Cloud Forest, to set the stage for an introduction to an ecosystem that’s is rapidly shrinking. Thirty years ago, when the scientists first described what is a cloud forest, they estimated around 3% of the world tropical rain forests to be cloud forests — forests that are immersed in cloud most of the year. Today, it is estimated that only 1.5% is left and disappearing. At today’s rate of climate change, most of it will be gone before we know it.  Rather than lament its impending loss, I would like to use the time and opportunity to celebrate this Garden of Eden and to share with you our experiences, the highlights and the sense of wonderment living in such an environment.

Imagine yourself dangling from a parachute, floating straight down on Nectandra forest looking down through your feet at 150 m (500ft) in the air.

You are about to land on what appears to be an immense head of broccoli where each tree constitutes a floret. But unlike the florets, the trees in the canopy are not clones. No two look alike because they are likely to be of different species. They come in all shades of green, each with a different texture and coarseness.

In the image above, the tightly packed tree canopy shows hardly any gaps between trees and even less between foliage. Tree branches are not visible.  In fact, the degree of gaps in the forest can be taken as an inverse measure of the density of the forest.  The denser the trees, the less gap areas in the canopy. Scientific computer software can count the black or gap pixels per unit screen area as a way to measure and monitor forest growth in drone images .

Drop down another 50 m and look ahead to get a different view. 

The trees appear now more varying in shapes, in heights and no longer pure green.  Under the oblique light, some of the trees definitely take on a brownish hue.  Leaves changing color? Dying trees? Look closer and you will note that the brownish green is not foliage, but thick mats of plants on the branches and trunks of trees.  The brownish growth are hundreds of intergrowing species of the liverworts and mosses — the tiny iconic plants of the cloud forest known collectively as the bryophytes.

A startling different view emerges as you descend to about 15m from the ground. You are now just below the upper canopy, looking through the tangles of the branches.  The presence of the bryophytes is overwhelming.

The accumulating bryophytes and plant detritus provide the necessary nutrients and loamy support for other epiphytic flora (plants that grow on other plants). Add the steady, constant misting during the day all year to the mix, plants with aerial roots can now grow and thrive.  Well known examples are the bromeliads (air plants), orchids, ferns, lianas, even begonias, to name just a few. Shown in the photo immediately below are impressive inflorescence of hanging orchids Oncidium sp. (see inset) on the left and an endemic Columnea macrophylla on the right (in the same family as african violets). Visitors on the ground are likely to miss this floral hanging garden because of the altitude.

From this height another striking, eye-catching group of cloud forest iconic trees are the tree ferns. The dozen species of tree ferns at Nectandra are beauties to behold, with their majestically large fronds (~1.5m) and great stature (up to 10-15 m).

Let’s drop down to the forest floor. Now look up. The view is typically through thick foliage of understory plants, and through epiphytes-laden branches. From this vantage point, nearly every surface is layered with bryophytes and epiphytes.

Look down, more bryophytes, on tree trunks, branches, leaves, rocks and soil…

Zoom in on the tree trunks, now the moss (below left) can be distinguished from the intermingling liverworts on the right, two representatives species among hundreds on the reserve.

We have come to the end of our vertical tour. On your future visits, I hope to introduce you to many more forest features and riveting fellow residents. Please check in for our next blog for more unconventional virtual tours of the Nectandra Cloud Forest.

Join us at Nectandra

Join us at Nectandra

to experience Serendips!

What is a serendip?

…..a chance encounter, an unexpected discovery, a happy accident, a startling fluke, an unforeseen experience, a fortuitous involvement, an unintended contact, a sudden insight, and so many more . . .

Serendips challenge our mind’s readiness for discovery. They often give no warning, and do not advertise. Our ability to detect and experience them rests on our mind’s readiness and alertness.

Cigar-sized caterpillar of Automeris moth

Just as all irrepressible children with their memorable discoveries, we at Nectandra want to share the excitement of our numerous serendips with the family members, friends and anyone who share our love for Nature and her profoundly beautiful living creations.

Starting this August, we will post any unusual findings and observations on subjects of tropical nature in general, and of cloud forest in specific with readers of our blog serendips.net The articles will be short and entertaining (we hope) and definitely informational.  Please subscribe to register your interest in becoming a Serendipper at Nectandra — the realm of furry plants and mossy animals .