I do the sampling with an Apstein plankton net by HYDRO-BIOS. I generally sample during the high tide, just before the dawn. I drag the plankton net for 100m against the current. The samples are placed in sample bottles filled with sea water.

The nylon (Nytal/Nytex) mesh of the plankton net is in 55 microns size, therefore it retains both phytoplankton and zooplankton organisms. After having used the mesh for 5-8 times, I change it for it overfills with sediments.


The living specimens are sometimes narcotized with magnesium chloride in order to slow down their movements. The sample is placed on a Petri dish in order to the specimens to be observed with a routine stereomicroscope (Motic SMZ-168TL); furthermore, the specimens are collected with a Pasteur pipette or a micropipette.

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First, I prepare a wet mount slide. I use 1.5 coverslips to avoid aberrations caused by the glass.  Between the coverslip and the slide I add some droplets of vaseline, so that I can  control the water volume on the wet mount slide by slightly pressing the coverslip. The goal is to decrease the water volume without squashing the specimens.


This is a research Nikon E600 microscope from Eclipse series. It supports the following techniques: brightfield, darkfield, polarization, phase contrast and differential interference contrast (Nomarski) of Sénarmont type. Each method reveals different information about the organism’s morphology.

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Test of microscopic techniques with Sarsia tubulosa (Hydroidomedusa).

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Polarization / Phase Contrast / Differential Interference Contrast (DIC)
Objective: 10x Plan Fluor


The camera connected to the microscope is Canon EOS 80D. All the pictures were taken from live animals.


Coastal plankton from Santander Bay (Spain).


Taxonomic determinations were based on examination of external morphological characters and compared to original descriptions and/or further redescription. Taxa were identified to the nearest level posible.

My work as a researcher has been as an ophiuroid taxonomist. So, as far as other groups are concerned, I can only make identifications as some kind of approximation; I hope in most cases they are correct.

When I saw it necessary, I turned to specialists in different zoological groups to identify those specimens that were a “headache” for me, for I wasn’t able to reach any taxon. I am grateful to all of them.

At the moment this is the list of the contributors …

Dr. Claudia Castellani, Plymouth Marine Laboratory, Plymouth, U.K.

Dr. Elena N. Temereva, Professor of Invertebrate Zoology, Moscow State University, Russia.

Dr. Hannelore Paxton, Department of Biological Sciences, Macquarie University, Sydney, Australia.

Dr. Philip R. Pugh, National Oceanography Centre, Southhampton, U.K.

Dr. Rod A. Bray, Department of Life Sciences, Natural History Museum, U.K.

Classification and nomenclature

According to WoRMS (

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