A1 Refereed original research article in a scientific journal
Growth and reproduction of an estuarine population of the colonial hydroidCordylophora caspia (Pallas) in the northern Baltic Sea
Authors: JORMALAINEN V, HONKANEN T, VUORISALO T, LAIHONEN P
Publisher: BIOLOGISCHE ANSTALT HELGOLAND
Publication year: 1994
Journal: Helgoländer Meeresuntersuchungen
Journal name in source: HELGOLANDER MEERESUNTERSUCHUNGEN
Journal acronym: HELGOLANDER MEERESUN
Volume: 48
Issue: 4
First page : 407
Last page: 418
Number of pages: 12
ISSN: 0174-3597
DOI: https://doi.org/10.1007/BF02366254
Web address : https://hmr.biomedcentral.com/articles/10.1007/BF02366254
Abstract
Growth and reproduction of the colonial hydroid Cordylophora caspia were monitored during the breeding season in natural conditions. In 1987, a life history study was carried out on the upright stems of the main stolen. Mean size of uprights varied cyclically. The first peak coincided with the peak number of sexual hydranths, after which the mean upright length decreased, possibly indicating somatic costs of sexual reproduction. Extrinsic factors like flooding may also have contributed to cyclical changes in upright size. In 1988 and 1989, colonies were reared on experimental plates in the estuary. In 1988, colonies grew until mid July, after which they regressed to a dormant condition and then started growing again in mid August. Predation and space competition are discussed as possible causes for this dormancy in the middle of the growing season. In 1989, colonies grew continually, with the exception of a decline in colony biomass and number of feeding hydranths at tile end of July, just following the peak of sexual reproduction. Sexual reproduction started in the early stages of colonial development for all years. During early summer, C. caspia allocated resources simultaneously in colonial growth and sexual reproduction. However, sexual reproduction had a clear peak in mid summer, and thereafter sexual reproduction ceased while colonial growth continued.
Growth and reproduction of the colonial hydroid Cordylophora caspia were monitored during the breeding season in natural conditions. In 1987, a life history study was carried out on the upright stems of the main stolen. Mean size of uprights varied cyclically. The first peak coincided with the peak number of sexual hydranths, after which the mean upright length decreased, possibly indicating somatic costs of sexual reproduction. Extrinsic factors like flooding may also have contributed to cyclical changes in upright size. In 1988 and 1989, colonies were reared on experimental plates in the estuary. In 1988, colonies grew until mid July, after which they regressed to a dormant condition and then started growing again in mid August. Predation and space competition are discussed as possible causes for this dormancy in the middle of the growing season. In 1989, colonies grew continually, with the exception of a decline in colony biomass and number of feeding hydranths at tile end of July, just following the peak of sexual reproduction. Sexual reproduction started in the early stages of colonial development for all years. During early summer, C. caspia allocated resources simultaneously in colonial growth and sexual reproduction. However, sexual reproduction had a clear peak in mid summer, and thereafter sexual reproduction ceased while colonial growth continued.
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