Bat development

It always gives a fellow a warm feeling to see an old comrade-in-arms publish a good paper. Chris Cretekos was a graduate student working on the molecular genetics of zebrafish at the University of Utah when I was a post-doc there, and he's a good guy I remember well…so I was glad to see his paper in Developmental Dynamics. But then I notice it wasn't on zebrafish—Apostate! Heretic!

Except…it's on bats. How cool is that? And it's on the embryonic development of bats. Even cooler! I must graciously forgive his defection from the zebrafish universe since he is working on an organism that is weird and fascinating and important.

Here's the abstract:

There are approximately 4,800 extant species of mammals that exhibit tremendous morphological, physiological, and developmental diversity. Yet embryonic development has been studied in only a few mammalian species. Among mammals, bats are second only to rodents with regard to species number and habitat range and are the most abundant mammals in undisturbed tropical regions. Bat development, though, remains relatively unstudied. Here, we describe and illustrate a staging series of embryonic development for the short-tailed fruit bat, Carollia perspicillata, based on embryos collected at timed intervals after captive matings. As Carollia can be readily maintained and propagated in captivity and is extremely abundant in the wild, it offers an attractive choice as a chiropteran model organism. This staging system provides a framework for studying Carollia embryogenesis and should prove useful as a guide for embryological studies of other bat species and for comparisons with other orders of mammals.

What this paper is is meat-and-potatoes embryology—it's a staging series, the kind of paper that documents the pattern of normal development for an organism as a reference. The zebrafish staging series is online, so you can see what one is like; it's a collection of photos and descriptions coupled to a timeline so that everyone has a standard reference point for future studies.

I can't say much about the paper. It consists of tables of stages and dry Latin words and lots and lots of photos of embryos, and it's the kind of droolworthy thing where you just want to look at the pretty pictures. So, here, a few of the figures from the paper.

Of course I have to show you a bat pharyngula. Early development isn't very surprising—it's generic mammalian stuff—but here you can see that common appearance all of us vertebrates have early on, looking like a segmented worm with an odd cluster of protrusions at the head end. The glossopharyngeal arch (ga) is marked, as is the otic vesicle (otv) and forelimb bud (fl).

You can start to see some dramatic differences from the human pattern of development at 60-90 days of gestation. Look at those forelimbs; you can see our five-fingered layout there, but there is extensive webbing and the fingers just grow and grow. I love those first couple of shots. The little guy looks so shy, hiding behind those big hands.

These are some closer shots of the developing limbs in 54-70 day old embryos.

a, autopod; aer, apical ectodermal ridge; ca, calcar; chp, chiropatagium; cl, claw primordium; dc, digit condensation; fp, foot plate; hp, hand plate; id, interdigit; mc, metacarpal; pl, phalange; plp, plagiopatagium; prp, region of the propatagium primordium; s, stylopod; tm, thumb; urp, uropatagium; z, zeugopod. All panels show the dorsal surface of the right limb with anterior toward top and the proximal at left, views are not to scale.

A lovely piece of work like this makes me want to open up a few pregnant bats…but on the other hand, I also like to keep our local bats happy and thriving and eating mosquitos. At the very least, though, I hope there is more work on bat embryology coming up soon.

Cretekos CJ, Weatherbee SD, Chen C-H, Badwaik NK, Niswander L, Behringer RR, Rasweiler JJ (2005) Embryonic staging system for the short-tailed fruit bat, Carollia perspicillata, a model organism for the mammalian order Chiroptera, based upon timed pregnancies in captive-bred animals. Developmental Dynamics 233(3):721-738.