Marisano James

Brief Bio

Figure 0: Picture of me taken at a beach cleaning event.

I’m a Ph.D. candidate in the Population Biology Graduate Group at UCD. Before joining the Eisen Lab I attended undergrad at Franklin and Marshall College, then worked as a software developer in the computer industry for awhile, before graduating from Jacobs University, Bremen, in Bremen, Germany, where I studied Computational Biology and Bioinformatics. I joined the Eisen Lab in 2008, whereupon I expected to study microbial phylogeny or virus evolution but I was lured away to the macro side by a class on the evolution of senses. [So I’d say the Eisen Lab moniker should be something more like, “Mainly microbes, all the time.”]

Figure 0: Picture of me taken at a beach cleaning event.

Research

I study the visual system of an enigmatic order of insects called Strepsiptera, which consists wholly of tiny (1–6 mm) parasites of other insects. Unlike the compound eyes of all other extant arthropods, those of adult male Strepsiptera consist of a series of simple eyes that together form the animal’s compound eye. Being simple eyes, each has its own extended retina—of about 60 to 100 photoreceptors, depending on the size of the species—upon which a tiny image is formed. Due to lens dynamics, these images are inverted, and must also be merged to form a useful continuous whole—not unlike what is done to unite the separate pictures of a panoramic shot in a smartphone. But neither of those actions are taken in the case of a typical compound eye, because therein each facet resolves no more than a single point.

Figure 1: Comparison of the externally typical compound eye of a Drosophila fly with that of a Halictophagus Strep­sip­tera. A) Small abutting facets constitute the compound eyes of this drosopholid, each of which resolves a single pixel. B) The ‘facets’ of this Strepsiptera are much larger because each one projects onto an extended retina, thereby producing multi-pixel images. They are also clearly separated. Because of such differences, the facets of an adult male strepsip­te­ran’s eyes are often referred to as eyelets. Note that the ventral eyelets are much larger than the dorsal ones. This may represent a so-called acute zone of superior vision. (A) was taken from [1]. (B) from [2].

All this peculiarity and ‘extra’ visual work invites one to ask why. What does an adult male Strepsiptera get out of his eyes? (BTW—adult females are blind, wingless, legless, and lack antennae¹; but then, adult males starve to death in a few hours…) How well can they see? How did their eyes evolve and why has this eye morphology been retained? To address these questions I’ve been investigating Xenos peckii, a diurnal species, and Elenchus koebelei, a crepuscular species. Among many fascinating attributes, ostensibly Strepsiptera are the only order of insects in which the same eye design is used exclusively in all three major light regimes: broad daylight, dawn and dusk, and late night—so I have designs to work with a nocturnal species too. Stay tuned!

Figure 2: Enlarged image of a dead adult male Elenchus koebelei. Taken for me by ©David Liittschwager, 2013.

Mouse-over the menu buttons above, or pause over parts of the insect’s body.

• Abdomen
  Abdomen: The abdomen of an adult male Strepsiptera is very flexible. In mating he’ll curve a good portion of it up under his thorax.
  

• Antennae
  Antennae: Adult male Strepsiptera have forked antennae (those of this species are bifurcated). They use these to zero in on hosts infected with the female of their species.
  

• Eye
  Eye: The compound eye of an adult male Strepsiptera. Note that it is composed of a number of simple eyes, looking rather like fish roe, as opposed to the angular facets of the typical compound eye.
  

• Haltere
  Haltere: Adult male Strepsiptera have two little balancers that assist them in hovering and aerobatic flight. These are called halteres. However, unlike those of Diptera—flies, mosquitos, midges, and the like—they are positioned in front of the wings, suggesting a closer kinship with Coleoptera, aka beetles.
  

• Legs
  Legs: The legs of adult male Strepsiptera are positioned such that the animal does not walk levelly, but they work well for holding on tightly. The first two pairs are often used to cling onto the host, while the third pair is usually used to grasp onto the small portion of a female that she protrudes from her host.
  

• Mesothorax
  Mesothorax: The second pair of legs descend from the mesothorax. The halteres – being modified forewings – also appear on this subsection of the thorax.
  

• Metathorax
  Metathorax: The enormous bulge characterizing the strepsipteran metathorax is indicative of the strong flight muscles therein. Additionally, the third pair of legs descend therefrom.
  

• Mouth
  Mouth: Strepsiptera have non-functional mouthparts. Unable to feed, adult males typically starve to death within 3 hours of eclosing. They generally only have enough strength to fly for a fraction of that time, however.
  

• Prothorax
  Prothorax: The first pair of legs descend from the prothorax.
  

• Wings
  Wings: The fan-shaped appearance of the wings gave rise to the common English name for the animal, “twisted-wing parasite”.
  

^{1. ^This is true of all but a single ancient lineage in which strepsipteran females retain eyes and legs. In that one clade, adult females can leave the body of their host, but they are still very lacking in mobility. This general inability to oviposit freely has led all strepsipteran females to give birth to live young that seek out their own hosts!}

Other Info

I am co-advised by Dr. Elke Buschbeck of the University of Cincinnati.

Acknowledgements

[1] ^Pohl H, Beutel RG. The phylogeny of Strepsiptera (Hexapoda). Cladistics [Internet]. Blackwell Science Ltd; 2005;21:328–374. Available from: http://dx.doi.org/10.1111/j.1096-0031.2005.00074.x

[2] ^Madden V. The head of a fruit fly (Drosophila) — as prepared by Madden [Internet]. Courtright P, editor. University of North Carolina at Chapel Hill; 2009. Available from: http://gazette.unc.edu/archives/09aug12/file.3.html