Ant Morphology

People have long been interested in morphological and behavioral differences between different worker castes in ants.

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(Photograph of a head of a major worker of Camponotus floridanus by April Nobile / ©AntWeb.org / CC-BY-SA-3.0, retrieved from Wikimedia)

A recent study published in Science teases apart some of the proximate mechanisms controlling foraging behavior in the Florida carpenter ant, Camponotus floridanus. Particularly, it focuses on the environmental factors that control genes by switching them on and off, an area of study called epigenetics. The study authors found that minor workers foraged much earlier in their lives than major workers, but by injecting major worker ant brains with compounds that reduced histone acetylation, they were able to stimulate foraging behavior in younger major ants.

This video summarizes parts of the study.

What do you think about the few blips in the video, such as the narration talks about foraging over the image of a minor worker carrying a pupa (brood tending?), as well as the first, slightly shaky definition of epigenetics?

What do you think of this study?

 

References

Sindya N. Bhanoo, Ants Can Change Their Roles, Study Finds New York Times, Dec. 31, 2015. (A version of this article appears in print on January 5, 2016, on page D2 of the New York edition with the headline: Insects: Chemicals Can Turn an Ant Society on Its Head.)

Daniel F. Simola, et al. Epigenetic (re)programming of caste-specific behavior in the ant Camponotus floridanus, Science  01 Jan 2016: Vol. 351, Issue 6268.
DOI: 10.1126/science.aac6633

Have you ever been on the quest for something and discovered something else entirely?

Take my pursuit to capture a "calendar-perfect" photograph of ants visiting peony buds. People have known that ants tend extrafloral nectaries on peony buds for a long time. It is one place that you are sure to find ants sitting relatively still (for ants) out in the open. Taking some colorful photographs of ants posing on peony buds seemed much easier than trying to capture one scurrying on the ground.

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As I was looking through the shots, I began to notice something else.

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It was subtle at first, but it's there if you look for it.

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The one on the left will give you a big hint.

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Here's one on a peony flower.

dented-gaster-2013

See it now?

 

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It seems like ants on peonies have more than their share of dents and missing body parts. If they were cars, you'd be sending them to the body shop.

I think it is conventional wisdom that foragers are the older ants in the colony and that older ants are probably more likely to be beat up a bit. It is possible, however, that tending peony buds is extra risky. What do you think?

Do you have a photograph of a "dented" ant? Leave us a link in the comments or share it on our Facebook page (No fair creating the dents yourself).

2 Comments

We have a question for the Consult-Ant* this week.

I have an ant question.
 
I was curious about ant eyesight. Not about their color vision but more specifically their quality of vision in the dark. Is it better or worse than a human's night vision?

This is a great question!

The first thing to remember about ants is that they perceive the world in vastly different ways then we humans do. They produce a number of different chemicals and communicate in ways that we can only dimly appreciate. Let's not forget, some ants are completely blind and they get around just fine.

That said, ants do usually live in dark tunnels, either underground or in wood. Many species forage at night, either all the time or during certain seasons. They are able to find their way around in the dark.

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For example, this carpenter ant lives in the hot desert. It forages at night and is rarely seen during the day.

To study how ants see at night, scientists have been looking closely that the anatomy of  the eyes of ants.

This figure from Invertebrate Vision, edited by Eric Warrant, Dan-Eric Nilsson shows that dark-adapted eyes of invertebrates are structurally different from light-adapted ones.

 

Ajay Narendra and his colleagues (2011) have been studying Australian bull ants (Narendra has photographs of bull ants ) that are active at night and comparing them to day-active species. They found that ants that were active at night had different eye measurements and eye structures, both within a given species (that is active both during the day and night) and between related species. The eye area, facet size, and ocelli (the smaller simple eyes at the top of the head) size, etc. were larger in night-active ants.  Reid et al. discusses more specific information about how the ants use their specialized eyes to see polarized light and landmarks during navigation at night.

Have I danced around your original question long enough? Comparing humans to ants is difficult because in a lot of ways it is comparing apples to oranges, plus our understanding of what other animals perceive is limited. Nevertheless, I'm going out on a limb. All these structural differences suggest that certain ants can be quite specialized for night vision. Based on that evidence, it would seem that ants are probably just as capable, if not more capable of night vision than unassisted humans. Of course humans are capable of inventing and using sophisticated devices to assist our night vision. In that case, humans win hands down.

What do you think about night vision in ants?

For more information:

Ajay Narendra, Samuel F. Reid, Birgit Greiner, Richard A. Peters, Jan M. Hemmi, Willi A. Ribi and Jochen Zeil.  (2011) Caste-specific visual adaptations to distinct daily activity schedules in Australian Myrmecia ants. Proc. R. Soc. B.  278:  1141-1149. (free .pdf available)

Reid, S.F., A. Narendra, J.M. Hemmi and J. Zeil. (2011). Polarised skylight and the landmark panorama provide night-active bull ants with compass information during route following. The Journal of Experimental Biology. 214: 363-370. (free .pdf available)

Wild About Ants post about color vision in ants

 

(* As I mentioned previously, I have been the “Consult-Ant” on the Leaping from the Box website. I answer questions about ants and ant farms. From now on I will post the answers here, and when Karen has time she will also post the answers on her site.)

Recently a reader had a question about ant anatomy. "I want to know the division of the ant's body where the head, chest and abdomen and what is from the antennae and legs and wings, eyes, etc."

In general, insects have three body parts: the head, thorax, and abdomen.

In ants, however, the main body parts are not as easy to tell apart.

When adult ants are developing their lovely thin “waists” within the pupa, a bit of the true abdomen gets pressed up against the thorax, and the rest of the abdomen becomes the "waist" and the hind section. When ant biologists realized this problem, they thought,  “Hum, we can’t really call that middle section a thorax, if it’s really a thorax and a bit of abdomen pushed together. And we can’t call the back section an abdomen if it’s only part of the abdomen… so we’ll call the middle part a mesosoma (in older literature an alitrunk) and the back part a gaster (or metasoma)." The thin part between the mesosoma and gaster is called the petiole. The head is still a head.

In some ant species, the "waist" is longer and consists of two segments, which are called the petiole and postpetiole.

Roberto Keller has an excellent illustration of the segments that make up the true abdomen.

Scanning Electron Micrograph, Roberto Keller/AMNH)

The bit of abdomen that joins with the thorax is labelled as I in this diagram. It is called the propodeum. The segments labelled II and III are the petiole and postpetiole. The rest form the gaster.

If the ant is a queen rather than a worker, you will see either the wings attached to the mesosoma (labelled as trunk), or wing scars where the wings were attached.

Hopefully that helps answer your question.

If you have anything to add, please leave a comment.