In “Molecular Phylogenetic Status of Microcentrum rhombifolium in the Family Tettigoniidae”, the authors of this paper focused on figuring out the molecular phylogenetic status of Microcentrum rhombifolium in the family Tettigoniidae. They did this by finding the partial sequence of the mitochondrial gene cytochrome oxidase subunit I (COI) of M. rhombifolium and comparing it to the other species in the family.

The family Tettigoniidae consists of about 6,000 species around the world. Included in the family are the katydids. The katydid we are focusing on today is the Microcentrum rhombifolium, or the “greater angle-wing katydid” of India. The paper focuses on its molecular phylogeny, or the DNA sequences of the organism, and uses them to analyze the organism’s relationship with the other species within the family. The specific DNA sequence found in this paper is the cytochrome oxidase subunit I. The cytochrome oxidase I gene is one that is mitochondrially encoded for cytochrome oxidase I, a protein that is the main subunit of the cytochrome oxidase complex of the electron transport chain.  

In order to analyze the COI subunit sequence for M. rhombifolium, the adult organisms were collected from the Calicut University in Malappuram, Kerala, India. After the genomic DNA was isolated from the thoracic legs of the organism, it was amplified using PCR for the mitochondrial COI gene. The PCR product was purified and sequenced from both ends using forward and reverse primers. Then, the forward and reverse sequences were assembled, the primer sequences were removed, and the sequence was analyzed. Finally, the divergence of COI sequence of M. rhombifolium from the other species of the family was calculated and placed in a phylogenetic tree.

Depicted is the phylogenetic status of M. rhombifolium among the 58 species of various genera of the family Tettigoniidae. (The text may not be clear in this picture. It is more clear on the original paper, which will be hyperlinked to this picture.)

Analyzing the COI subunit, it was found that the nearest relatives of genus Microcentrum were the genus Dioncomena and Monticolaria, Dioncomena ornate and Monticolaria meruensis being the nearest relatives to our species M. rhombifolium. Interestingly, Dioncomena and Microcentrum were found to come from a common ancestor. This makes sense as their evolutionary divergence between their COI sequences was one of the least, at 18.80%.

Since the genome is a fundamental property of all living organisms, it makes sense that some evolutionary trees have been constructed entirely from DNA sequences. This can be helpful in identifying organisms and their phylogenetic status. In the field of medicine, these evolutionary trees can be used to identify the origins of certain diseases caused by certain organisms in efforts to create a drug to combat the disease.

Overall, I found this paper very interesting! I have only ever seen phylogenetic trees based on external characteristics that organisms have in common. Therefore, I thought it was very unique how this study created a phylogenetic tree using entirely genomic DNA sequences. 

References:

Mashhoor, K., Akhilesh, V. P., Sebastian, C. D., Rosy, P. A., & Kottickal, L. V. (2012). Molecular Phylogenetic Status of Microcentrum rhombifolium in the Family Tettigoniidae. Developmental Microbiology and Molecular Biology, 3, 9-15.

The Katydids are a part of the family Tettigoniidae and the order Orthoptera which comprises of insects like grasshoppers, crickets, locusts, etc. Interestingly enough, “formal investigations into katydid phylogenetic relationships have never been published… this lack of a published phylogeny has made it difficult to decipher the evolutionary patterns in katydid morphology” (Mugleston, 2013).

The recurring feature of the katydids in my past blog posts is their complex acoustic signaling. It plays an important role in sexual selection, claiming territory, and sometimes attracting prey. Therefore, it only makes sense that the “shape of size of the organs associated with katydid hearing are one of the characters used to delineate tettigoniid subfamilies” (Mugleston, 2013). The acoustic signaling in katydids is one of the main features that unifies members of the family Tettigoniidae.

In the phylogeny I have chosen, the katydid family Tettigoniidae is differentiated into subfamilies based on features like the leaf-like tegmina and the thoracic spiracle which is an organ responsible for the acoustic signaling in katydids. In regards to my organism, the broad-winged katydid (Microcentrum rhombifolium) is part of the subfamily Phaneropterinae in the clade B.

This figure depicts the phylogeny of all the Tettigoniidae subfamilies in the Clade B. The picture is not clear, but if you click on the link it will take you to a clearer picture!

The family Tettigoniidae is found to be closely related to the suborder Ensifera which is a suborder of the order Orthoptera. In fact, “Sharov found fossil evidence to support Tettigoniidae as sister to all the remaining ensiferan families” (Mugleston, 2013). One of these families is the Grylloidea family which includes the “true crickets”. In the article, they found that these crickets were the sister family to Tettigoniidae based on ribosomal data. The relationship between the true crickets and the katydids seem to be the anatomy of the insects. Both crickets and katydids look similar because their “antennas are much thinner and longer” but the difference lies in their legs which are aligned with the body in katydids and perpendicular in crickets (Grasshopper, crickets and katydid, how to differentiate them…, 2019).

References:

Mugleston, J. D., Song, H., & Whiting, M. F. (2013). A century of paraphyly: A molecular phylogeny of katydids (Orthoptera: Tettigoniidae) supports multiple origins of leaf-like wings. Molecular Phylogenetics and Evolution, 69(3), 1120-1134.

Grasshopper, crickets and katydid, how to differentiate them ? (2019, January 15).

Although katydids can camouflage themselves onto the leaves that they reside on, one of the most impressive things they can do is acoustic signaling. Many insects can blend into the leaves they live on, but the katydids are some of the only insects with a very complex form of acoustic signaling. In fact, “insects like katydids have evolved biophysical mechanisms for auditory processing that are remarkably equivalent to those of mammals” (Montealegre-z, 2015). This impressive feature is shared among all katydid species, therefore I will be discussing this feature in terms of all the katydid species.

When the katydids first receive a signal, it can affect one of three sound inputs: the acoustic spiracle or the two tympanal membranes on the forelegs which act like ears. It is then received by the crista acustica which are the sound reception cells. The cells then send the received signals to the insect’s ganglia (Mugleston, 2013 & Montealegre-z, 2015).

The general anatomy of the Katydid ear including the acoustic spiracle and the two tympanal membranes (PTM and ATM).

These organisms use this complex way of receiving and sending auditory signals for not only sexual selection, but also territorial displays and sometimes to attract prey (Mugleston, 2013). Using the knowledge about this physiological feature, you could learn how these insects can differentiate between auditory signaling that are directed towards them and are not directed towards them.

References:

Mugleston, J. D., Song, H., & Whiting, M. F. (2013). A century of paraphyly: A molecular phylogeny of katydids (Orthoptera: Tettigoniidae) supports multiple origins of leaf-like wings. Molecular Phylogenetics and Evolution, 69(3), 1120-1134.

Montealegre-z, F., & Robert, D. (2015). Biomechanics of hearing in katydids. Journal of Comparative Physiology A, 201(1), 5-18.

As I mentioned in the previous blog post, what makes the katydid so interesting is the sound it makes! They make a loud, high-pitched clicking noises in order to attract mates.

However, in most species of katydids, the songs are only produced by the males. If the females also produce songs, they are usually non-repetitive and of such low intensity, and in response to the call of the males (Carlysle, 1975).

The way katydids produce these kinds of sounds are through a process known as stridulation. Typically one forewing possesses a vein modified with a series of cuticular teeth (the stridulatory file), whereas the contralateral wing bears a scraper or plectrum… During the closure of the wings, the scraper on one wing hits the file teeth on the other, creating a sound. Katydids produce two types of sound. These are the pure-tone sounds and the broadband sounds (Ewing, 1989).

Anatomical structure of the Katydid’s wings that creates the mating call

The wings of the katydid are mainly used as a mating call, since this structure is what they use to make the sound. In regards to evolution, besides the wings thickening over time, the function of these structures has not changed (Jost & Shaw, 2006).

Above, I have provided a video of a common meadow Katydid stridulating. Although it is not a broad-winged Katydid, they both still perform the same stridulating technique. It is super interesting to see and the video also includes a pretty awesome clip in slow motion!

References:

Carlysle, T. C. “MORPHOLOGY AND FUNCTION OF FEMALE SOUND-PRODUCING STRUCTURES IN ENSIFERAN ORTHOPTERA WITH SPECIAL EMPHASIS ON THE PHANEROPTERINAE.”

Ewing, A. W. “Arthropod bioacoustics; neurobiology and behavior. 1989.” Comstock, Cornell University Ithaca, NY

Jost, M. C., and K. L. Shaw. “Phylogeny of Ensifera (Hexapoda: Orthoptera) using three ribosomal loci, with implications for the evolution of acoustic communication.” Molecular phylogenetics and evolution 38.2 (2006): 510-530.

There are thousands of species of insects that all belong to the order Orthoptera, including some that many people are familiar with like grasshoppers, crickets, locusts, katydids, etc. (“Species Microcentrum rhombifolium“, 2014).

For my blog, I will be discussing the katydid, specifically the Microcentrum rhombifolium (broad-winged katydid or greater angle-wing katydid). These specific katydids are found in the eastern and southwestern regions of the United States where they live on deciduous trees and shrubs in various habitats (“Species Microcentrum rhombifolium“, 2014).

Pictured: the broad-winged katydid

Before I started my research, I had only ever heard of grasshoppers and crickets, so katydids were completely foreign to me. I chose the katydid for my blog project because they seem like very interesting creatures that I would love to learn more about!

One of the coolest things about the katydids is the sound they make! “Ka-ty-did” is the sound that you can hear when you listen to their repetitive clicks, which is where they get their name (“Katydid (Microcentrum rhombifolium)”, 2019).