www.bryozoans.nl - General remarks

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Introduction

While scuba diving in Dutch lakes you encounter all kinds of things. If you look well among others you'll find bryozoans, also called moss animals. Most of them lead a fairly hidden existence, others are easier to find.
The first time i encountered a bryozoan consciously that was Cristatella mucedo which colonies were growing in masses on a branch of a tree that extended into the water. I did not know what this funny life form was and started searching.
I became fascinated en have used this website to bundle my knowledge, experiences and underwater pictures.

For underwater observation i partially use an underwater magnifying glass and partially a digital camera (Canon S50 and Canon A620, A640) in an underwater enclosure in combination with an underwater flashlight (Ikelite DS 50, DS 125). The A640 now has largely replaced the others as its macro ability is good (1 cm) and its resolution (10 Mpixel) better.
I use the S50 camera in combination with underwater mountable macro lenses from Sea&Sea and Inon. The Inon macro lenses i use stacked, 2 or 3 on top of each other, in order to get sufficient detail.
An advantage of a digital compact camera over a SLR camera is that it is doable to come close enough for a macro photo, even if the bryozoan lives in a fissure between rocks or under a piece of wood. And yes i am aware that SLR cameras can do better macro, but their housing is bulky and the dome port easily damaged.
The pictures are not always correctly lighted color wise, due to water color (sometimes peat brown) or flash color - they are too yellow. Where possible i adjust this later.

Scuba diving provides the option to study bryozoans in situ. As i go diving almost every week at least once in the same lake, the whole year round, i gain the unique possibility to get an understanding of the dynamics, both of the lake and of the bryozoans in relation to the lake.
As i study bryozoans mostly while diving, my focus for this website is on species description and specially on a search key that is focussed on recognizing and identifying bryozoans in situ or in combination with analysis of underwater macroscopic pictures later. This approach is markedly different for the one described in the almost all literature where study is done based on samples taken with fine-mesh nets and/or dredging for study later back in the laboratory. This sampling approach forces a focus on statoblasts as they are dominant in the material collected this way.

Since the first instance of this website i started using a microscope to further extend my bryozoa studies. As you can see elsewhere on this site i also make photos through my microscope(s). I have recently created a special section on statoblasts and intend to attempt to find and photograph them all in due time.

I am well aware of the fact that my approach is likely to lead to wrong identifications now and then. At the other hand and given the confusion in descriptions in the literature, this will not reduce the result too much and will definitely increase my pleasure and i hope other peoples' pleasure as well.

Web site structure

This site is partly built on my own experience, observations and pictures and partly on literature (see refrences and links).
The structure of the main page follows [Wood II], as far as it is likely that species exist in the Netherlands. P. rugosa is omitted as it resembles P. repens too closely for a diver to distinguish them and has so far not been found in the Netherlands as far as i am aware.
P. casmiana is included on the assumption the species may well inhabit the Netherlands, but has not yet been found. The same goes for P. geimermassardi, that may have been recently (June 2009) found for the first time (under investigation).
If it is not explicitly stated that an observation is my own, it is derived from the literature i used. The species description pages are explicit in this. The first part is literature derived, the "My obeservations" part is just that.
If it is not explicitly stated that a picture is made by someone else, pictures are my own.

Much of the general information is derived from [Ryland I], complemented by several other sources.
The synonyms mentioned in each species description are derived from [Geimer&Massard], with a crosscheck and completion with [Lacourt I]

I have standardized the species description by defining and using the following terms:

  1. Species name
  2. Colony form
  3. Colony branching
  4. Color (described as good as possible, includes zooid wall structure
  5. Appearance of the zooids
  6. Polypide form
  7. Polypide angle (to zooid)
  8. Number of tentakels per polypide
  9. Other relevant remarks

Open questions

Besides many practical questions that arise while studying bryozoans and developing this site, there are also a few more fundamental questions that keep nagging me:

  1. If bryozoans migrated from seawater to freshwater in a geologically more recent past, how did they solve the osmotic challenge?
    While in the sea they were osmotically challenged by the salt water that extracted water from the bryozoan body by osmotic pressure. In freshwater it is the other way around and the water keeps forcing its way into the bryozoan body.