Craig Wm Schneider's Seaweed Lab

Simple methods for the cultivation of reproductive Vaucheria(Vaucheriaceae, Chrysophyta) in the laboratory

by C.W. Schneider

Marine and brackish water species of Vaucheria are frequently encountered in salt marshes and salt flats, along estuarine river banks and even subtidally in tidal channels; in each of these areas the penetrating siphons of Vaucheria are ecologically important substrate stabilizers. Freshwater species are commonly found along pond, river and stream banks, drainage ditches along highways, and freshwater marshes and swamps. If samples are collected from any of these disparate environments for later identification or classroom demonstrations, more often than not, the siphons are found to be vegetative when observed under a compound microscope and thus are unidentifiable at the species level. With a little patience and effort, field collections can be coaxed into producing gametangia in vitro in a short period of time, thus allowing the collector to easily identify the species collected or just demonstrate oogamous reproduction in this genus to his or her students.

Vaucheria is often found as fuzzy green algal mats emanating from the substrate, but siphons actually penetrate well below the substrate surface (an edaphophyte). Sediment quadrats with siphons emanating should be cut with a serrated knife, removed using a wide spatula along with mud or sandy substrate 2-3 cm thick, placed in zip-lock plastic bags, jars or other collecting devices and placed on ice for later transport to the laboratory. Vascular plants within the quadrats should be cut off at surface level. Clearly label the bag or jar with the precise location from which each sample originated, as several samples could be obtained from different parts of the same estuary. These different samples could easily yield different species due to microhabitat variability. Single quadrats of mud 6.5 cm on each side and 2-3 cm thick (size compatible with deep-dish Pyrex culture vessels) have produced as many as four different Vaucheria species over time in vitro (Schneider et al. 1993). Mud samples without obvious Vaucheria can also be taken from a marsh, as the substrate may contain either subsurface siphons or resting spores. For later reference, the salinity of water near each of the samples should be tested with a refractometer at the time of collection and recorded on the collecting bag or vessel.

In the lab, samples should first be observed under a compound microscope for the presence/absence of gametangia. Vegetative samples should be placed into labeled deep culture vessels, covered finger bowls or formalin-free collection jars and filled to one-half of the substrate thickness with marine or freshwater culture media depending upon the source of the sample. Successful growth of gametangia can be obtained with any number of enriched or synthetic culture media including Grund (von Stosch 1969) and ES (Provasoli 1968) for marine species and Bold’s basal medium for freshwater species (Bischoff & Bold 1963). If you wish to produce brackish salinities for your cultures you can use the modified ASP-V media of Entwisle (1988). After the addition of appropriate liquid media, the cultures should then be placed in a controlled growth chamber with photoperiod set at 16L:8D, fluorescent light intensity of ca. 125 umol/m2/s and a temperature of 15 deg.C. If no growth chamber is available, place the samples with media on a lab windowsill, in a greenhouse or under fixed lights in the lab. Long photoperiods will induce gametogenesis more quickly than shorter ones for most species. Within ten days to two weeks, incubated cultures will begin to produce gametangia. Antheridia and oogonia can be observed by pulling filaments from several locations within the sample and making wet mounts on glass slides. Because several species may be present in the same salt marsh sample and not all might fruit at the same time, it is necessary to continue checking the samples over the next few weeks for “late bloomers.”

Literature Cited

  1. Bischoff, H. and Bold, H. C. 1963. Phycological studies IV. Some soil algae from Enchanted Rock and related algal species. Univ. Tex. Publ. No. 6318, Austin.
  2. Entwisle, T. J. 1988. An evaluation of taxonomic characteristics in the Vaucheria prona (Vaucheriaceae, Chrysophyta). Phycologia 27: 183-200.
  3. Provasoli, L. 1968. Media and prospects for the cultivation of marine algae. In, A. Watanabe & A. Hattori, eds., Cultures and Collections. Proc. U.S.-Japan Conf. Hakone, Sept. 1966. Jap. Soc. Plant Physiol. pp. 63-75.
  4. Schneider, C. W., MacDonald, L. A., Cahill, J. F. and Heminway, S. W. 1993. The marine and brackish water species of Vaucheria(Tribophyceae, Chrysophyta) from Connecticut. Rhodora 95: 97-112.
  5. von Stosch, H. A. 1969. Observations on Corallina, Jania and other red algae in culture. Proc. Int. Seaweed Symp. 6: 389-99.