title: Physiological characterization of stolon regression in a colonial hydroid.
abstract: As with many colonial animals, hydractiniid hydroids display a range of morphological variation. Sheet-like forms exhibit feeding polyps close together with short connecting stolons, whereas runner-like forms have more distant polyps and longer connecting stolons. These morphological patterns are thought to derive from rates of stolon growth and polyp formation. Here, stolon regression is identified and characterized as a potential process underlying this variation. Typically, regression can be observed in a few stolons of a normally growing colony. For detailed studies, many stolons of a colony can be induced to regress by pharmacological manipulations of reactive oxygen species (e.g. hydrogen peroxide) or reactive nitrogen species (e.g. nitric oxide). The regression process begins with a cessation of gastrovascular flow to the distal part of the stolon. High levels of endogenous H(2)O(2) and NO then accumulate in the regressing stolon. Remarkably, exogenous treatments with either H(2)O(2) or an NO donor equivalently trigger endogenous formation of both H(2)O(2) and NO. Cell death during regression is suggested by both morphological features, detected by transmission electron microscopy, and DNA fragmentation, detected by TUNEL. Stolon regression may occur when colonies detect environmental signals that favor continued growth in the same location rather than outward growth.
authors.affiliation: Department of Biological Sciences, Northern Illinois University, DeKalb, IL 60115, USA.
authors.forename: Kimberly S Cherry
authors.initials: KS
authors.lastname: Vogt
authors.forename: Gabrielle C
authors.initials: GC
authors.lastname: Geddes
authors.forename: Lori S
authors.initials: LS
authors.lastname: Bross
authors.forename: Neil W
authors.initials: NW
authors.lastname: Blackstone
mesh_terms: D000825:Animal Structures / Q000000981:diagnostic imaging / Q000502:physiology*; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000633:toxicity; D037402:Hydrozoa / Q000033:anatomy & histology / Q000502:physiology*; D020287:In Situ Nick-End Labeling; D046529:Microscopy, Electron, Transmission; D009569:Nitric Oxide / Q000633:toxicity; D026361:Reactive Nitrogen Species / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014463:Ultrasonography
chemical_list: D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D006861:Hydrogen Peroxide