Golden-Eyed Walking Stick (Peruphasma Schultei)

Taxonomic Information

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Phasmatodea

Family: Pseudophasmatidae

Genus: Peruphasma

Species: schultei

Peruphasma schultei is commonly known as the golden-eyed walking stick or the black beauty walking stick. The nearest captive colony of the golden-eyed walking stick to Iowa State University is Rieman Gardens in Ames. Native to a small area along the Peru and Ecuador border, colonies are kept by institutions all over the world in order to conserve the species. Fortunately, this species is easy to keep in captivity and reproduce quite easily allowing us to observe their reproduction and certain genetic factors. They have very interesting anatomy and physiology with distinct cuticle structures and gut microbiology. They have a very unique defense mechanism that allows them to spray an irritant at predators which is atypical for phasmids.

Habitat

This species is native to an area of less than 5 hectares in the Cordillera del Cóndor region of northern Peru. Because this species is maintained by several institutions, including Reiman Gardens, we have the ability to maintain genetic diversity and ensure the survival of the species.In the wild, Peruphasma eat Schinus, which is a flowering shrub known as the pepper tree, which is the source of the spice pink peppercorns.

The Cuticle

Peruphasma schultei is described for its characteristic velvety matte black cuticle. This appearance is due to two different types of microstructures that vary in size in the cuticle. These microstructures scatter the light in such a way that causes the matte appearance while different pigments cause the black color. There is a maximum reflectance of 2.8% preventing any shine. The microstructures are also hydrophobic decreasing wettability and increased heat absorption allowing them to have better warming properties.

Morphs

There are two distnict morphs of peruphasma schultei. The common wild type has red wings and red mouthparts. The second type has light pink wings and white or yellow mouthparts. The second type is rare in the wild but is more common in captivity.

Genetics

It has been shown that wing color and mouthpart color are genetically linked and can be easily tracked using a Pennet Square. The red morph is dominant which explains why it is more common in the wild. The pink morph is recessive and is more prevalent in captivity likely due to increased inbreeding.

The Gut

The microbiology inside of phasmid's digestive tract is relatively unknown. Symbiotic bacteria are common in herbivorous insects to help aid digestion, however, the thin body shape and gut structure of phasmids prevent the gut enlargement needed for microbial fermentation. All Phasmatodea have rigid proventriculi lined with small spines and some have anterior projections of the midgut which can also block the proventriculus. Sequencing the entire microbiota of the fat bodies, salivary glands, and midguts showed that most bacterial sequences belong to a strain of Spiroplasma (Tenericutes) and that there was a large lack of bacteriocytes. Based on the results of these sequences, it is likely that phasmids do not depend on bacteria for digestion. This suggests that phasmids have to produce enzymes that many other herbivorous insects would get from their symbionts.

Defense

In Peruphasma schultei, the suboesophageal ganglion (SOG) controls many fine motor functions including the prothoracic defense glands. These glands, located at the base of the head, secrete a substance that can cause irritation to the skin and eyes. During an anti-predator event, they have two behavioral options. 1) The secretion can be released onto its own body or 2) it can be aimed and sprayed onto the target. Like we talked about, arthropod innervation is different from vertebrates because it can be innerved by multiple types of nerves, and the strength of a response is due to the rate of impulses. The musculus pronoto-occipitalis (Idlm2) muscle is close to the ejaculatory duct of the gland and controls neck movements and the direction of discharge. This muscle and others surrounding the gland are innerved by three neurons, the ipsilateral neuron (ILN), the contralateral neuron (CLN), and the prothoracic intersegmental neuron (PIN). The ILN causes a fast contraction of large muscles around the gland. It is suggested that the CLN might be involved in the coordination of discharge and is closely associated with the ILN of the contralateral gland.

Peruphasma schultei, native to northern Peru, is kept by a variety of institutions all over the world which helps conserve genetic diversity and the population. This species is easy to keep in captivity and reproduces easily. Recent studies on the species have focused on the interesting features in the cuticle, gut microbiota, and their defense mechanism. If you're interested in this species you can see a colony over at Reiman Gardens to learn more!

Works Cited:

Doris L. Maurer, Tobias Kohl, Michael J. Gebhardt, Cuticular microstructures turn specular black into matt black in a stick insect, Arthropod Structure & Development, Volume 46, Issue 2, 2017, Pages 147-155, ISSN 1467-8039, https://doi.org/10.1016/j.asd.2016.11.006.

J. of Orthoptera Research, 24(1):29-40 (2015). https://doi.org/10.1665/034.024.0105

Konrad Stolz, Johannes Strauß, Joscha Arne Alt, Reinhard Lakes-Harlan, Independent suboesophageal neuronal innervation of the defense gland and longitudinal muscles in the stick insect (Peruphasma schultei) prothorax, Arthropod Structure & Development, Volume 47, Issue 2, 2018, Pages 162-172, ISSN 1467-8039, https://doi.org/10.1016/j.asd.2018.02.003.

Shelomi, M., Lo, WS., Kimsey, L.S. et al. Analysis of the gut microbiota of walking sticks (Phasmatodea). BMC Res Notes 6, 368 (2013). https://doi.org/10.1186/1756-0500-6-368

van de Kamp, Thomas. (2011). The “pink wing” morph of Peruphasma schultei Conle & Hennemann, 2005 (Phasmatodea: Pseudophasmatidae). Entomologische Zeitschrift. 121. 55-58. https://www.researchgate.net/publication/224805782_The_pink_wing_morph_of_Peruphasma_schultei_Conle_Hennemann_2005_Phasmatodea_Pseudophasmatidae/citation/download

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