Outside of the realm of Biological Sciences, one rarely pays attention to arthropods and when it does, such a glimpse comes with a high charge of scorn and usually takes the poor lost creature to an inescapable death. I don’t exclude myself from being one of the giant, mean, and ugly creatures called humans that once took advantage of its power and, without any plausible reason, took a life. A life that, however insignificant it may seem, is no less valuable than any other.
As the name suggests, invertebrates are all those spineless animals that, according to several sources on the internet, comprehend approximately 80% of all animal species on Earth. The chitin-based hard exoskeleton is largely responsible for the group’s success. This provides defense against mechanical shock, dehydration, and disease prevention for insects, arachnids, and crustaceans. Terrestrial arthropods consume an enormous amount of organic matter, including plants, other animals, and even themselves. They are also a very important food resource for most part of ecological communities.
In Brazil, there are research papers published as early as 2003 pointing out that some terrestrial arthropods and other invertebrates were declining. Even so, according to the last Brazilian Red List of Threatened Fauna (published in 2018), only 3% (about 3,300 species) of the known invertebrates in the country were evaluated regarding their conservation status. This means that the situation of the remaining 97% is unknown. Additionally, some members of this group (which may vary from hundreds to thousands of species) can literally be on the brink of extinction or, since the book was published in 2018, may already have vanished from their natural environments.
It has been demonstrated that habitat fragmentation negatively affects several groups of biodiversity. Dung beetles, for example, respond sharply in terms of abundance and species richness to this kind of disturbance. Coleoptera order (beetles) is the most diverse insect order in the world. Such diversity is often reflected in morphological aspects of its species that vary from tiny bright colored to rhinoceros beetles, which can reach an impressive 19 cm in length (source: London Natural History Museum). The variety of ecosystem services provided by them is comparable to their diversity. As these animals manipulate and feed on others’ excreta, they also contribute to seed dispersal, nutrient cycling, and parasite suppression. Thus, beetle diversity decline may harm the whole ecosystem balance.
Besides being an important base component in the food chain, several invertebrates act as predators in their own tiny world. Robber flies (family Asilidae) are natural predators of other insects, usually associated with tropical Savannas (such as the Cerrado in Brazil). Besides their important role in controlling other natural insect populations, they have been also considered a viable option for the use as pesticides in crops (controlling potential pests). Unfortunately, the biome where these and other flies reach an exceptional richness is also one of the most threatened in Brazil, mainly due to the uncontrolled expansion of agribusiness itself, which was undeniably supported by Brazil’s recently deposed ruler.
A little further up the food chain (although the situation can be reversed in some cases), arachnids are almost as diverse as they are relevant to the ecosystems they occupy. Spiders, which can reach the size of rats, can prey on animals as large as birds or small mammals. Tarantulas of the Atlantic Forest are usually much more modest in terms of body size when compared to their Amazonian relatives but, they are terrific. I had the pleasure to photograph some of these beauties when releasing those captured in the traps I used in my last research project (see “Life sciences and ecotourism in the Atlantic Forest in Brazil”, published in the 33rd volume of Paws Trails Explorer). It’s impossible not to notice how wronged these animals are when you’re dealing with them directly. Virtually all the tarantulas I dealt with, were extremely docile animals that never showed any aggressive reaction (at least when they weren’t being cornered). I was even able to witness what I consider the greatest of heartwarming behaviors, a huge female of Vitalius wacketi caring for its offspring.
On the other hand, being a gentle giant has never been an advantage in a world dominated by narcissistic creatures (most human beings, with the exception of those who recognize the ecological importance of arthropods for nature conservation). Due to the “selfish fascination” of some and disregard of the authorities, tarantula trafficking currently represents a major threat to their natural populations. Apart from the fact that keeping them in captivity represents an act of cruelty, some of these spiders end up escaping from their captivity and become invasive species that have a major impact on local ecosystems.
Not so friendly but also not less interesting than their close relatives, scorpions are on my list of favorite subjects in macrophotography. The two genera with which I have been in most contact were Tityus (Yellow scorpion) and Bothriurus (Black scorpion) since both were very abundant in the study area where I have conducted the fieldwork of my Ph.D. (see “The Santa Bárbara Ecological Station: An Island of Cerrado Biodiversity”, published in the 36rd volume of Paws Trails Explorer). The latter is much less dangerous than the former and the sting is as painful as that of a wasp (without major repercussions.
Species of the genus Tytius (Yellow scorpion) have received considerable attention from venom and health researchers due to their medical importance, particularly T. serrulatus, which is considered the most dangerous scorpion in Brazil. In addition to presenting a highly toxic venom, the species is extremely adaptable to the urban environment and human habitations (urban scorpions feed mainly on cockroaches, present parthenogenetic* reproduction, and do not present predators in this type of environment), which enhance contact with human beings and thus, lead to a great number of accidents. In spite of its great defensive capacity, the role of scorpion weaponry goes far beyond defense against humans and their predators.
The stinger (telson) and pincers (chelae) can be used for both capturing and handling scorpions’ prey, as during sexual contests (male combats aiming to ensure mates or territory). Scorpions are known to present a generalist feeding which means they may include a wide variety of prey (including even spiders) in their diets. In the reproductive context, male-male interactions may include different phases of antagonistic behaviors, such as alert (visual signaling) and physical contest (grab dispute which aims to flip the opponent). Males can also use their chelicerae (mouth parts) and sting in the courtship.
A recent study (published in the Journal of Arid Environments by Lira and colleagues), conducted in the most arid Brazilian Biome, the Caatinga, showed there is a negative relationship between some of the landscape attributes (shrub and tree densities) and the total number of scorpions found. Even the species composition varied in function of these attributes. As said before, scorpions consume a wide variety of organisms in their respective ecosystems, thus, it seems unlikely that the removal of species or even part of individuals from a given environment does not harm the natural balance.
Although all these animals are relatively small, they do have massive ecological roles. Their major threats are no different from those which harm other environmental components throughout the world, such as habitat loss, and other human-related activities. I shared here, just a few information of about a small number of invertebrates. There are literally thousands of other little creatures just as beautiful and interesting as those mentioned. Sadly, partially due to their cryptic and tiny nature, invertebrates are often left behind. I see macro photography as a powerful tool for scientific sharing, which can make the difference to provide a literally closer perspective on nature, particularly for those who go unnoticed.
*Parthenogenesis: Form of asexual reproduction, in which the egg can give rise to a new living being without being fertilized by a male.
Acknowledgments
