The life history and ecology of two North American gastrotrichs

TitleThe life history and ecology of two North American gastrotrichs
Publication TypeJournal Article
Year of Publication1949
AuthorsBrunson RBruce
JournalTransactions of the American Microscopical Society
Volume68
Pagination1-20
KeywordsLIFE HISTORY
Abstract

1. More than 1500 cultures of gastrotrichs have been successfully maintained by employing a solution of malted milk as a culture medium. 2. Whole cultures were preserved by first anesthetizing with menthol and then killing with formalin. 3. Lepidoderma squamatum occupies a diversity of habitats and was collected from waters within eleven counties of Michigan. 4. Predators of L. squamatum include Amoeba spumosa, Craspedacusta ryderi and Chlorohydra viridissima. 5. The life history of Lepidoderma squamatum may be summarized as follows: (a)Two types of eggs are produced; tachyblastic which normally start cleavage and development as soon as they are laid, and opsiblastic which experience a period of dormancy prior to development. (b) Embryonic development is completed within 36-50 hours. (c) Newly hatched animals average 121 micra in length, adults 154. Growth is at the rate of four micra per hour. (d) The post-embryonic life-span ranges from 8.5 to 21.5 days and averages 16.2 days. (e) Individuals lay from two to five tachyblastic eggs each; the average per individual is 3.67. (f) Some opsiblastic eggs have hatched after being dried for periods up to 23 months and others have hatched after being frozen for three months. 6.The life history of Chaetonotus tachyneusticus is in many ways similar to, but in some ways different from, that of Lepidoderma squamatum. (a) The embryology of the two species differs only in certain details. (b) The first cleavage plane may be either transverse or longitudinal. (c) Embryonic development is completed within 36-40 hours. (d) The young average 132 micra in length, whereas the adults average 171. (e) A tachyblastic egg may be laid after an animal has previously laid an opsiblastic egg, which appears not to be the case in L. squamatum. (f) C. tachyneusticus probably has a much lower biotic potential than L. squamatum.