Methods

Lab

Sampling

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. The net, after every use, must be washed with fresh water. After having used the mesh for 5-8 times, I change it for it overfills with sediments.

Procedure

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 specimen I am interested in is taken with a Pasteur pipette or a micropipette (depending on the size of the specimen) and is placed on another Petri dish with a filtered sea water.

Captura de pantalla 2017-01-15 a las 17.59.42

Then, from the second Petri dish, the specimen is taken one more time with the Pasteur pipette or the micropipette and placed on 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.

Thus, the specimen can be observed in a clean field.

And The Most Important Thing: taking good photos requires certain skills, these skills are only developed with much practice.

 

Microscope

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.

Nikon_E600.JPG  E600 Objectives.jpg  40x 60x.jpg

Test of microscopic techniques with Sarsia tubulosa (Hydroidomedusa).

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

Photos

All the pictures were taken from live animals. The camera connected to the microscope is Canon EOS 80D. The camera is coupled directly, without any intermediate lens. A dovetail and some rings to adjust the distance. At the moment I am not using flash. Most images are single shot, but in some cases, such as copepods that were narcotized, I make stacks with Zerene Stacker. The software that I use to connect the camera to iMac is Canon EOS Utility.

Location

IMG_1301.JPG
Coastal plankton from Santander Bay (Spain).

Identification

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. Demetrio Boltovskoy, Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA), Facultad de Ciencias Exactas y Naturales. Buenos Aires, Argentina.

Dr. Elena N. Temereva, Professor of Invertebrate Zoology, Moscow State University. Moscos, 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. London, U.K.

If you find any incorrect identification or you have any additional information, feel free to contact me.

Classification and nomenclature

According to WoRMS (http://www.marinespecies.org/index.php)

© Rafael Martín-Ledo

Follow my web on  Unknown

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