Tag Archives: purple urchin

Strongylocentrotus purpuratus: Purple sea urchin– The Race Rocks Taxonomy

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Purple Urchins and Californianus sp mussels at a “zero” level tide on the west side of Great Race Rocks.
July 2000

The purple sea urchin is about 10 cm. across, spines up to 2cm. and is bright purple. Its body “skeleton”, called the test, is shell like with bumps and holes from which the moveable spines and tube feet extend .The spines are used for protection, movement and for trapping drifting algae. It has a claw like mouth with 5 teeth-like plates. It is composed of over 60 shells and is called Aristotle’s lantern and is located on the underside or oral side of its body. The anus and the genital pores are on the aboral side of the sea Urchin.

In February, 2004 we had a note from CECIERJ requesting permission to use our video of the purple sea urchin in media being prepared for their undergrad distance learning courses. By offering these courses, the consortium CEDERJ contributes to bringing high quality free education to the inner cities of the Rio de Janeiro State. As well as permitting such use of our resources, we have added for them, an introduction by one of our Brazilian students, Rita who helped us make this video in Portuguese about the Sea Urchins and Echinoderms..

Diet: The Sea Urchin feeds on algae, plankton, kelp, periwinkles, and occasional tiny barnacles or mussels.

They are eaten by crabs, sunflower stars, snails, sea otters, some birds, fish, and people.

Reproduction: Fertilization in Sea Urchin is external, the female release several million tiny, yellow jelly-coated eggs at a time. The gametes join the water column as planktonic forms .

Behaviour: Although they often live in sheltering holes that they have worn in the rocks and they have also been observed to makes holes in solid steel, this behaviour is not evident at Race Rocks. Most of them live in shallow water here, They move surprisingly fast on their tube feet and spines. Moving their feet by a hydraulic water vascular system which creates suction in the end of the foot by pulling water out of the madreporite. They can also regrow broken spines.

The following images show the structural features on the test of a dead purple sea urchin. The image was produced by scanning.


This image shows the aboral view of a purple sea urchin.The dark patch in the middle is the anus. These were dead specimens.Thus the spines are missing.

Domain Eukarya
Kingdom Animalia
Phylum Ecinodermata
Class Echinodea
Order Echinoida
Family Strongylocentrotidae
Genus Strongylocentrotus
Species purpuratus
common name Purple Sea Urchin

The lower image shows the oral view of a purple sea urchin. The hole in the middle is its mouth with the sharp edges its 5 teeth. Note the pentaradial symmetry.

Tidepool # 5

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Pool 5 viewed from Pool 6

This file has been started to present some of the information we have accumulated on the pool in order to stimulate students to raise further questions and devise problems that can be investigated at the pool. It is also intended to be part of a cumulative digital legacy that those examining the pool can pass on to future students.

 

Tidepool 5 when the surge is filling it.

Pool 5 with a compass bearing of 210 degrees from Peg 6 is only cut off from the open ocean at a very low tide so it has a number of invertebrates that need cooler water to survive. Some anemone and purple urchins and several snail species inhabit this pool.

The following is a student lab done on an analysis of this pool:

TIDE POOL LABORATORY

BY: SARA PAVAN, ROCIO GIL, ANA MARIA VEGA, MARIUXI ZAMBRANO

Introduction

THE INTERTIDALZone: It is an area occupied by a great number of individuals and species. It is sufficiently inundated by tides and waves that provide plant nutrients, Oxygen and plankton. It is the zone where tide pools form.The intertidal zone of Race Rocks is very rich of tide pools. They are conventionally numbered for the purpose of identification. The tide pool that was studied for this lab is pool #5.

POOL NUMBER 5: It is a very low pool but very high in biodiversity. It is located in an area very open to the swells of the sea.

STRUCTURE OF THE LAB

BIOTIC FACTORS: measurement of horizontal and vertical distribution.

ABIOTIC FACTORS: temperature and salinity.

AIM OF THE LAB: TO STUDY THE HIGH BIODIVERSITY IN THE LOW POOL.

PROCEDURE AND ANALYSIS.

In the middle of the tide pool and at point#1.1 temperature and salinity were measured. The table shows the data collected.

 

  salinity-parts per thousand  temperature °Celsius
 middle-surface  27.5 parts  9°
 middle-8 centimetres  28.5  9°

middle- 48 centimetres 9° 30

point 1- 8 centimetres 9° 28.5

point 1- 28.5 centimetres 9° 29

The above results were obtained in the morning and comparing with the results given by other groups at 4:00 pm, we can see that the temperature increased one degree.

The data collection process has caused some problems, as big swells came regularly every three minutes from 9:22 to 9:28, a smaller swell came at 9:31 and an even smaller one came at 9:36. At these times we had to clear a pool, this slowed down the process quite a bit.

The following species were found in the following points.

In point 2 Balanus was found at 20 cm. of depth to the surface. It was found also in point 3 at 23 cm. of depth to the surface.Two Anthopleura elegantissima were found at 25 cm. of deph. Two Purple Sea Urchins were found at the point of 1 metre of length, covered by rocks. Two cabezons were present as well as mussels. Fucus distichus algae were covering the left part of the pool.

Some of the species were weighed the same day that were collected.Then they were dried and weighed again, with the aim of obtaining the biomass. The next table shows the results obtained

Species Weight before dry Weight after dry Biomass

Corallina 14.1 g 4.8 g 34 %

Fucus 20.1 g 1.3 g 6.5 %

Green algae 8.7 g 0.6 g 0.6 %

Phylospadix (surf grass)  -10.5 g 2.3 g 21.9 %

 

To get the Biomass results we multiplied the dry weight for 100 and divided by normal weight.

To get more data about pool 5, we measured the amount of plankton of each sample of water. The results were that there was less plankton in the surface than in the bottom due to the constant exchange of oxygen produced by the waves

Measurements of the pool 5.

1.Aea: 34546.95 cm2

2.Length: 1449.65 cm.

To obtain these measurements, refer to this file on using NIH IMAGE

Obviously, the level of oxygen in pool 5 must be really high due to the huge diversity of animals and plants found. As we know, the plants produce oxygen and the animals consume it while producing carbon dioxide, which provokes an interaction increasing and decreasing the level of ph and oxygen  depending on whether sunlight is present for photosynthesis or not.

OUR EVALUATION.

From the beginning of the lab, we had some problems to take the samples due to the high tide that made the collecting of samples a lot more difficult. A more accurate study of the pool, could have been done by measuring the levels of ph and oxygen. Team work was effective, the effort came from everyone in the group and we succeeded in computer work by obtaining  excellent pictures and measurements of the pool.