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Lab module 7: sampling eelgrass habitat structure and epifauna
Template for completing lab exercise
TYPE YOUR NAME HERE:
NAME OF ANY COLLABORATORS
Introduction: Use the dipnet.csv and droptrap.csv files on Canvas to make graphs and perform
the appropriate statistical analyses for the questions below. Copy and paste the results of your
statistical tests into your answer and explain what the results of that test tell you about
relationships between the data. Do the results indicate that you have disproven the null
hypothesis? Display the P value and/or R2 value for the test you used and explain what these
numbers mea explicitly. Please submit a completed version of this worksheet by1:00PM on
Monday 3/22. Remember to include the name of anyone you collaborated with for this
assignment.
♠Part 1: How does edge vs interior eelgrass habitat affect the Simpson’s diversity of animals
collected in dipnet samples?
Hypothesis:
Rationale:
Graph(s) of the data:
Statistical test:
Page | 1
Your interpretation of the results:
♠Part 2: How does mean shoot length correlate with Simpson’s diversity in the droptrap
samples?
Hypothesis:
Rationale:
Graph(s) of the data:
Statistical test:
Your interpretation of the results:
Page | 2
♠Part 3: How does shoot density (shoot count) correlate with Simpson’s diversity in the droptrap
samples?
Hypothesis:
Rationale:
Graph(s) of the data:
Statistical test:
Your interpretation of the results:
Page | 3
Page | 4
BIOL517 Lab 7 2021
Laboratory 7 – sampling seagrass habitat
Goals for the lab
1. Learn what structural characteristics of seagrasses (and other plants) typically are quantified
from field samples, and how these are quantified in the lab
2. Obtain data on these structural characteristics to statistically correlate with the abundance and
diversity of epifaunal animals that live in seagrass habitat
Introduction
A major focus in marine ecology today involves the influence of habitat structure on ecological
processes. Habitat structure is defined as “the physical arrangement of objects in space” and it
includes characteristics like the amount and variation of structural elements that make up a
habitat. For a coral reef, characteristics of habitat structure could include the biomass, height, or
perhaps the volume of coral present in a given area of seafloor. It could also include a measure of
the variety (i.e. complexity) of coral structures found within a given area (e.g. the percent cover
of branching coral vs. massive coral). For seagrasses like Zostera marina (eelgrass), habitat
structure includes the biomass of shoots and roots present in a given area, the density of shoots
(the number of shoots per unit area), and the average height of shoots. Another element of habitat
structure to quantify for seagrass could be the relative amount of epiphytic and drift algae within
a given area. The algae would add a level of complexity to the Zostera bed that otherwise would
not be there.
Habitat structure in environments like
seagrass beds is highly variable from place
to place, and this may have profound
influence on the abundance, diversity, and
survival of organisms in this habitat. More
habitat structure can mean more living space
for organisms. For instance, on a coral reef,
the more coral is present in a given area, the
more living space may be available
organisms that attach directly onto coral.
Living space also could include small
crevices that fishes and crustaceans tend to
inhabit, and the surfaces of seagrass blades. Figure 1: Fish in a seagrass bed from Australia.
Another reason that habitat structure often
correlates with organism abundance is that the ability of predators to find and capture their prey
is significantly reduced within a dense habitat. Picture yourself as a fish looking for prey to eat
within the seagrass bed pictured (Figure 1). A small animal (your potential prey) can hide behind
the seagrass blades or even among filaments of epiphytic algae if they are small enough, making
it difficult to find, and the seagrass blades would hamper your ability to capture the prey item
once you did detect it. Thus, prey organism density tends to be higher where habitat structure is
greater, i.e. where the density of shoots is high or the biomass of shoots per unit area is high.
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BIOL517 Lab 7 2021
Organismal density
Another major question
Linear
Hyperbolic
Sigmoidal
concerning habitat structure that
A
B
C
many marine ecologists have
focused on is the form of the
relationship that exists between
habitat structure and the density
and diversity of organisms. For
instance, a linear function may
best describe the relationship
Habitat complexity
between the structure of a habitat
Figure 2: Hypothesized relationships between habitat complexity and
and how many individual organisms organismal density.
there are in an area of a habitat
(Figure 2a). The linear relationship suggests that there is a steady increase in organismal density
with structure. A hyperbolic relationship (Figure 2b), on the other hand, suggests that the density
of organisms quickly increases just by adding a small amount of habitat. Eventually, however,
this reaches an upper asymptote. A third common relationship between structure and the density
of organisms is sigmoidal (Figure 2c), which suggests that a threshold level of structure needs to
be reached before the structure begins to significantly attract or affect organisms. Each of these
functional forms also could be applied to biodiversity or survival of organisms in habitat.
General Procedures
In part 1 of this lab, we usually visit a seagrass bed in San Diego Bay to collect samples of
eelgrass habitat and the organisms that live there in different ways. The samples we collect will
be frozen and then in part 2 we process them to quantify seagrass habitat structure and the
density and diversity of animals that live in seagrass. Finally, after we collect all of these data we
will use statistics and graphs executed in R software to determine if there are correlations
between seagrass habitat structure and the animals that live there.
Part 1
Since you all can’t come out to the field this year, I went out and collected some samples and
made a video of the procedures described below.
1. We first want to collect small areas of seagrass and the animals that live within the seagrass
blades. Most of these animals are crustaceans and gastropods that are a few millimeters to a few
centimeters in size. To collect seagrass and organisms at this scale, we typically use small
circular samplers called drop traps. These are pieces of PVC pipe with mesh bags attached to
the tops. The trap is placed down over seagrass blades in shallow water, the seagrass is pulled
from the sediment by hand, and the trap is inverted and washed into the mesh bag. A label is
placed into the bag, and the seagrass and organisms are then placed in a cooler, and eventually
frozen to preserve them so that they can be counted and identified later.
2. We sometimes want to sample larger organisms from seagrass habitat, and for this we have a
number of options. We will use dipnets to sample 10 meter transects through eelgrass bed
interiors and along eelgrass bed edges. By pushing the dipnet along the sediment surface we
scrape and stir up most of the larger organisms living in the eelgrass into our net.
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BIOL517 Lab 7 2021
Other options for sampling macrofauna include throw traps which are usually larger,
lightweight square or circular traps that can be dropped or thrown into shallow habitat to trap the
organisms inside. The trapped animals are then scooped out with dipnets, or sucked out of the
trap with a device known as a suction sampler, which uses air pressure from a scuba tank to
create a vacuum effect within a long tube. To capture even larger and faster animals like fishes,
one can use a beach seine, which is a very long net that is deployed from the shoreline. An
alternative to the beach seine is a trawl, which is a large net towed behind a boat that is used to
capture animals on the bottom or in the water column.
3. Since we want to see if the density and diversity of animals is correlated with the amount of
seagrass, we need a way of collecting seagrass to quantify habitat structure. To get these
samples, another type of sampler is used, a seagrass corer. This is a cylinder of PVC pipe,
usually about 20 cm in diameter, that is pushed into the sediment to collect the shoots and roots
of seagrass within small areas. These samples of the habitat are returned to the lab and the shoots
are counted, measured, and weighed.
Each sample will be preserved in a mesh bag (drop trap samples) or a plastic Ziploc bag (core
samples and dipnet samples). All bags with samples MUST BE LABELED. Samples will be
frozen before being processed in the lab.
Part 2
For part 2, we will process the three types of samples in the lab.
Instructions for processing seagrass core samples
Each group will need: 2 glass trays; 4 glass bowls; 2 metersticks; 1 marker.
1. Remove a thawed sample from the bag and place it in the glass tray.
2. Label one glass bowl with the sample number and the word “roots”. Label the other glass
bowl with the sample number and the word “shoots”.
3. Pick up an eelgrass shoot. Unless it has been broken off, you will see roots and rhizomes
attached to the shoot. At the base of the shoot is a white area that connects the shoot to the
roots.
4. Break off the shoot just below this white area. Place the roots in the proper glass bowl. Take
the shoot and lay it next to the meterstick, with the white base at the zero mark. Record the
length of the longest blade in the shoot on the data sheet (last page).
5. Place the shoot in the other glass bowl.
6. Repeat steps 3-5 until all of the shoots have been measured.
7. You will probably have some leftover shoot and root material. Place these in the proper
bowls. Try to leave any sediment in the tray, rather than placing it in the bowls.
8. Place the full, labeled bowls on the lab cart with the other bowls.
9. On the data sheet, count the number of shoots in your samples and calculate the mean shoot
length for each of your samples. The weight of shoots and roots will be recorded separately
after drying.
These samples will be dried in a drying oven at 60º C for 48 h and then weighed. Then the dried
material will be removed from the bowls and the bowls weighed alone. The difference in the
weights equals the weight of the material that was in the bowl (i.e. shoots or roots). After all this
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BIOL517 Lab 7 2021
is completed, we will have measures of shoot density (count), shoot biomass, mean shoot length,
and root biomass for all of the core samples.
Instructions for processing drop trap samples
1. Using a 1 mm sieve, rinse the loose seagrass material under running water to remove any
animals from the plant material. Place the rinsed seagrass in a plastic weigh boat that has the
sample number written on it. We will dry and weigh this material to obtain a measure of the
biomass of seagrass within the sample.
2. Use a squirt bottle to rinse the animals into a glass pan. Separate any clumped animals and
then begin to separate them by species as you did for the throw trap samples. Many of the
animals you see likely will be gammarid amphipods, which represent many different species
that are very hard to distinguish. We are not going to try to distinguish among these species,
and will simply call these “gammarid amphipods”. These can easily be distinguished from
caprellid amphipods, otherwise known as “skeleton shrimp”.
3. Record the counts of different species on the data sheet marked “drop trap” at the end of this
lab. After you have counted every individual, all of the animals from a sample should be
placed into a labeled (with Sharpie) plastic (or aluminum) weigh boat. The animals will be
dried in a drying oven and the dry weight will be obtained to get animal biomass for each
sample.
Instructions for processing dipnet samples
These samples consist of organisms that were captured by sweeping a dip net through seagrass
shoots. There will probably be some small amount of plant or algal material, but most of the
sample should consist of small animals that were captured in the net. We are going to count
these animals by species to obtain data on density of the animals and the number of species we
find. For these samples we will focus on macrofauna, i.e. organisms that are larger than 6 mm
(about a quarter of an inch) in size.
1. Empty the contents of the plastic bag into a sieve, and rinse the inside of the bag to remove
any organisms that are stuck to the mesh.
2. Rinse the sieve with water and rinse any loose material with water, and discard any loose
plant or algal material once it is rinsed.
3. Use a squirt bottle to get the animal material in the sieve into a glass pan. Spread the animals
out on the pan so you can count and identify them.
4. Use the epifaunal identification guide available on Blackboard to identify, separate and count
animals by species. Keep a count of the number of individuals for each species on the data
sheet. Many common species are already listed on the data sheet, but some species you find
may not be listed. You do not need to know every species that you find, but you should do
your best to identify different species, so we can obtain measures of diversity.
5. After you have counted every individual, all of the animals from a sample should be placed
into a labeled (with Sharpie) plastic (or aluminum) weigh boat. The animals will be dried in a
drying oven and the dry weight will be obtained to get animal biomass for each sample.
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BIOL517 Lab 7 2021
A brief introduction to statistical tests.
Statistical test are crucial tools that help scientists rigorously interpret their data and test
hypotheses. We will begin a more thorough discussion of different statistical tests, their utility,
and their limitations during next week’s lab, but for now we will focus on the basic results of ttests and linear regressions.
T-tests are used to compare means between two categorical treatments. Given that we expect
to see randomness and variability in any real-world data, we need this test to tell us how likely is
that an observed difference between two treatments is due to some underlying ecological
relationship as opposed to random chance. The null hypothesis is that the two means do not
differ; that the treatments produce essentially the same results. The main output of this test is a P
value. A low P value (generally p1000 micron >500 micron
•
Date: 6 month / Nov 2017, or 12 month / April 2018
Please label all vials with my initials (KG) and ‘UNB [sample period]’. UNB stands
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for Upper Newport Bay. The date is really important!
Intro
Kaylee G. samples protocol
1. Gather tools: Fine forceps, probe, shallow dish, pipette, microscope, EtOH bottle, tapwater
bottle, podcast/lecture/something to listen to ;)
2. Choose a jar. Pull out/label (cap and side) the scintillation vials with the appropriate sublevels and rest of the proper ID (site/date/KG/etc), and EtOH:
1. Gammarids
Example:
DA ES-E3 4/21/17 (time zero) (jar)
1. DA ESE3 gam
UNB T0 EtOH KG (vials)
2. Caprellids
2. DA ESE3 capr
UNB T0 EtOH KG
3. DA ESE3 crust
UNB T0 EtOH KG
3. Crustaceans (all other crustaceans go here)
4. DA ESE3 other
UNB T0 EtOH KG
4. Other (molluscs, worms, etc.)
5. DA ESE3 unsure
UNB T0 EtOH KG (optional)
6. DA ESE3 trash
UNB T0 EtOH KG (jar)
5. Optional: ‘help’ or ‘unsure’
3. Sort and count. Add a small aliquot from the jar to the dish. Use the OH/tapwater squeezy
bottles to distribute the contents. See tips.
1. If using new vials, fill the vial a quarter of the way (approx. 70% EtOH, 30% H20)
2. Carefully separate organisms from debris/junk. As you place organisms into the vials,
count and record! Make sure organisms are submerged.
1.
Count heads.
2.
Isopods, tanaids, shrimp, and molluscs get sorted to SPECIES. Others are more broad.
3. Place the debris into a separate jar labeled ‘ID Trash’. KG will go through it to make sure
nothing was missed.
4. If you knock anything over, its ok. Return everything you can to proper vials, record that
something was spilled. Wipe down the microscope if needed.
4. Clean up your area when finished for the day (don’t forget to cover microscope/turn off its 7
light). Return EtOH to fume hood.
Intro
Subphylum Crustacea
Phylogeny of Malacostraca compiled after Richter and Scholtz (2001)
1. Segmented body regions with specialized appendages (varied functions)
1. head, thorax (sometimes fused to form cephalothorax), abdomen
2. Two pairs of antennae, Three pairs of mouthparts (mandibles and 2
pairs of maxillae)
3. Biramous appendages: thoracic and abdominal
2. Calcium carbonate in cuticle
3. Compound eyes
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Crustacea
Class Malacostraca
Order Amphipoda
Amphipods are characterized by these traits:
1) Laterally compressed (most)
2) No carapace
3) Cephalon: Head + first thoracic segment
4) the abdomen is divided into two parts
each with three segments
1) Typically have 6 pairs of legs per
abdomen
5) Non-stalked eyes
6) Thoracic brood pouch
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Gammarids
Suborder Gammaridea
Gnathopods (G) are the two large claws- there are 5 types.
The telson (T) is the most anterior part of the abdomen. There also five types.
Uropods (Ur) can be thought of as tails (sometimes with spines) that have additional tails called
rami. The rami on uropod 3 are especially important, and vary by family. They are not the easiest to
see, but can sometimes aid in identification if they can be seen.
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Adapted from Barnard and Karaman 1991, SD guide 2013
Gammarids
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Suborder Gammaridea
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Temporary slide
The gammarid family slides that follow need to be
thoroughly checked, since they have not been updated
since ~2014. They could be perhaps bolstered by
Chapman key chapter/LSM/etc. More figures from that
key could be added?
This would be a great task for whomever would be
interested in sorting gammarids to families.
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Gammarids
Pleustidae
PLEUSTIDAE rostrum massive to minute,
lacking a ventral antenna sinus, telson notch
ventrally keeled.
Pleustidae has a very large rostrum and large
subchelate gnathopods. If you are still unsure
that it is Pleustidae look for a laminar, uncleft
telson.
LSM page(s) 599-603
Eusiriodea
EUSIROIDEA rostrum pointed or minute,
rostrum inserted between antenna 1
peduncle first articles, ventral antenna
sinus notched (except Batea), dorsal
urosome spineless
Eusiriodea has some similar looking species (and has the
same telson and uropods), but their gnathopods are not
as large and are usually simple and not subchelate.
Eusiridoea usually has modified pleons (Pleustidae does
not), like the specimen above, that make it easy to identify
besides looking at the telson. So far the only Eusiriodea
species that I’ve found is the specimen above. If you still
cannot differentiate them, start staring at the plates in the
book and pick the one that looks the most similar to your
specimen. They are both common in South Bay eelgrass.
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Gammarids
Hyalidae
HYALIDAE maxilla 1 palp of 2 articles, male
gnathopod 1 dactyl modified for clasping
female.
Dexaminidae
DEXAMINIDAE pereopods 3–7 dactyls short, pleated
gills.
Do not confuse this gammarid with Pleustidae. Though,
it does have a large rostrum note that it’s eyes are quite
small and the gnathopods are also not as large.
The definitive characteristic however, is it’s telson. The
telson is laminar like Pleustidae, but is cleft instead
(Pleustidae has an uncleft telson).
Found in South Bay eelgrass. (specimen in picture may
or may not be species in figure)
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LSM page(s) 583
Gammarids
Ischyroceridae
ISCHYROCERIDAE uropod 3 outer ramus with
denticles or teeth, telsons diverse
These guys have distinct spotting throughout their
body and are a black or purplish blue color. They have
small subchelate gnathopods that have an
indentation that makes them look like mittens. Their
antennae are usually gone and all that is left are the
peduncles.
Their bodies are thin and long compared to the fat,
rounded bodies of most Gammarids. The telsons are
variable in this family, so the best thing to do if you
are having trouble is to look at vials of this Gammarid
and become familiar with them as they are the most
abundant of all the Gammarids around Shelter Island.
Also found in South Bay. (specimen in picture may or
may not be species in figure)
LSM page(s) 569-570
Leucothoidae
LEUCOTHOIDAE gnathopod 2 article 5 extending
along article 6, telson distally acute.
Liljeborgiidae: mandibular molar reduced, telson
lobes distally notched, commensal with
polychaetes and echiuroids.
Very easy to identify. The type of gnathopods they have
are carpochelate and are extremely large compared to
other Gammarids. They are the only Gammarids that
have gnathopods like this.
However, they look almost identical to Ischyroceridae
besides that, so be careful when identifying smaller
specimens of either type (Leucothoidae specimens are
generally larger). They are the next abundant after
Ischyroceridae in Shelter Island waters. Also found in
South Bay. (specimen in picture may or may not be the
species in figure)
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LSM page(s) 282
Gammarids
Corophiidae
COROPHIIDAE basket-shaped gnathopod 2,
suspension feeders, sediment tube builders
***This description should be read in conjunction with
Aoridae’s as they are very similar***
They have a purplish blue color with stripes on their
pereons. They have extremely large, I’m assuming this
is what they are, molar extensions. If you look closely
though they have merochelate gnathopods. Their
telsons + uropods do not look like the typical
gammarids. It’s very flat and resembles Idotea
somewhat, so be careful when making your decisions.
They tend to be on the medium to larger size of
Gammarids, which make them easy to identify.
Very rare around Shelter Island, still pretty uncommon
around South Bay but more frequent. (specimen in
picture may or may not be the species in the figure)
LSM page(s) 571-572
Aoridae
AORIDAE gnathopod 1 basket-shaped and merochelate
or carpochelate and larger than gnathopod 2, uropod 3
biramous except for uniramous Grandidierella.
***This description should be read in conjunction with
Corophiidae’s as they are very similar***
This gammarid has only been found in South Bay. The
stripes are not as dark and resemble dots more than
clear stripes. The gnathopods are also a lot smaller,
however they are of merochelate shape. The telsons are
unfortunately of the same type, but they look very
different. Aoridae has the general looking telson and
uropods unlike Corophiidae.
Found in South Bay eelgrass. (specimen in picture may
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or may not be species in figure)
Gammarids
LSM page(s) 561
Stegocephaloidea
STEGOCEPHALOIDEA epimeron 3 ornate, coxa 1
ventrally acute, rostrum large decurved (Iphimediidae
gnathopod 2 with long lysianassoid article 3).
How I identify this guy is by looking at it’s pleons.
They have a distinctive shape that resembles curved
hooks (figure). They are unfortunately hard to see as
they are close to transparent. You have to pick the
specimen up and sort of turn in it from side to side to
allow the light to reveal the spines.
The telsons and gnathopods are not reliable in
identifying this specimen. They all look very similar
so matching it to this picture and looking for the
pleons should be all that you need to do.
Found in South Bay eelgrass. (specimen in picture
may or may not be species in figure)
LSM page(s) 587
Oedicerotidae
OEDICEROTIDAE eyes dorsal, rostrum helmet-shaped,
gnathopods 1 and 2 article 5 variously extended along
article 6, pereopod 7 is 50% longer than pereopod 6 and
with long straight dactyl
The only thing you need to look for here is its one eye.
This is the only gammarid whose eyes have
coalesced into a single mass.
Found in South Bay eelgrass. (specimen picture may
or may not be species in figure)
LSM page(s) 584
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Gammarids
Podoceridae
Taxon
PODOCERIDAE telson spinose, pleopods
powerful, eyes bulge laterally.
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Gammarids
Melitidae???
??
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Gammarids
Ampeliscidae???
Stenothoidae??
STENOTHOIDAE coxa 3 and 4 massive, coxa 1 small,
obscured, distal telson bluntly acute, tongue-like.
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Gammarids
Suborder Caprellidea
Caprella californica
One of the easiest organisms to identify. Often
called ‘skeleton shrimp’, even though they are
amphipods. They have several feeding modes,
but C. californica is a filter-feeder ad a scraper,
There are only two Caprellids that you will find.
They can range from very large (over 3 cm) to
very tiny, sometimes smaller than the
Gammarids. The smaller ones tend to lose color
after preservation, are translucent and difficult to
find, and get tangled in each other and on debris.
Common at all sites.
LSM page(s) 622-623
C. californica can be distinguished from
Caprella equilibra (not shown) by having a
spike on its head. The spike might be hard to
see, if not impossible, unless under severe
magnification.
The females may have a brood pouch.
Illustration from Takeuchi, I., Oyamada, A. 2012. https://doi.org/10.1007/s10152-012-0329-9
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Caprellids
Order Isopoda
Idotea resecata
1) Dorso-ventrally compressed
2) No carapace
3) Cephalon: Head + first thoracic
segment
4) Pereon: Rest of thorax
(w/ 7 pairs of legs)
5) the abdomen’s pleopods are used
for swimming and respiration
Rather large isopod. Note the fused telson.
Uncommon.
LSM page(s)
Parasitic isopods
6) Non-stalked eyes
7) Thoracic brood pouch
E.g. Elthusa californica. Distinctive body shape.
Parasitic on fish, uncommon.
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Adapted from Brusca, R. C., V. Coelho and S. Taiti. 2001. A Guide to the Coastal Isopods of California. http://tolweb.org/notes/?note_id=3004
Isopods
Erichsonella crenulata
They have obvious “scalloping” of the body, with each segment having
lateral “bumps”. Unlike Idotea, telson is a single unit (pleotelson). Very
elongated isopod with large, long antennae. They appear glassy brown
under the scope. Rare at all sites.
LSM page(s) 526
Heteroserolis carinata
Not to be confused with Paracerceis. They are not opaque but appear
clear to light brown under the scope. They sort of resemble horseshoe
crabs with large black eyes that are ventrally located. They are also
smaller than Paracerceis and are fragile. Rare at all sites.
LSM page(s) 520
Paranthura elegans
Unlike Tanaids, their telson is comprised of five different parts that
together look like pairs of spread wings. They are also thinner than
Tanaids and Idotea. Also, unlike Tanaids and Idotea, they do not have
large claws or long antennae. They appear translucent brown under the
scope. Rare at all sites. LSM page(s) 507
Paracerceis sculpta
These guys are fairly large compared to most of the organisms you’ll be
identifying. They resemble rollie pollies and feel hard when picked up
with the forceps. Most of the time you’ll find them curled in a ball. They
have distinct large black eyes. They appear black or grey under the
scope. Rare in Shelter Island, but very abundant in South Bay eelgrass.
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LSM page(s) 523
Isopods
Order Tanaidacea
Anatanais pseudonormani
They slightly resemble the Gammarid family Corophiidae
because of their purple/violet coloration and large claws.
However, they do not have the many legs that
Gammarids have. If you compare the specimen to the
pictures they have the distinct “Tanaid” body plan.
They are rare in Shelter island, but are the common Tanid
in South Bay eelgrass.
LSM page(s) 543
Leptochelia dubia
They appear white with a blueish black line (probably
the notochord or intestine) running down the length of
their bodies. Very easy to identify as they resemble the
figure exactly. Some can be very tiny, but most
segments can be counted under the scope to identify
them.
Not to be confused with Idotea which have a large
unsegmented (fused) telson. They also have large
claws, while Idotea have large antennae. The most
common Taniad in the waters around Shelter Island.
LSM page(s) 542
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Adapted from C Phillips and D. Wendt, originally from Barnard and Karaman 1991
Tanaids
Order Cumacea
Cumacea sp.
Relatively small compared to most organisms you will find. The
defining structure is their pleon and telson, which looks like a
proboscis but is actually an extended part of the abdomen.
Broken limbs from other amphipods can sometimes look similar,
so make sure to examine things closely when you are not sure.
Rare at all sites.
LSM page(s) 495-502
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Other crustaceans
Order Decapoda, Infraorder Caridea
Hippolyte californiensis
Extremely abundant shrimp found in the eelgrass beds. They are generally
the largest crustacean you’ll find in these samples.
They can be identified by their spines on their “cheeks,” located posterior to
the rostrum, which Cragnon does not have. The spines are very hard to see,
but look exactly as in figure. Hippolyte also has stalked eyes. Unless it is very
large it is probably Hippolyte, since Cragnon is very rare in our samples.
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LSM page(s) 639
Other crustaceans
Order Decapoda, Infraorder Brachyura
Lophopanopeus bellus
Shore crabs
Hemigrapsus oregonensis
Three carapace spines
Hairy legs
Portunus xantusii
Note pointed claws and hind leg swimmerettes. Adults have
spines at the lateral ends of the carapace.
Pachygrapsus crassipes
Two carapace spines
Genus species
Text
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Other crustaceans
Class Ostracoda
Very tiny bivalve Crustacean. They look like little clam
shells with black dots, which are their eyespots. They
appear white and a tad translucent under the scope. Very
fragile and easy to crush.
Rare in Shelter Island, but very abundant in South Bay
eelgrass.
LSM page(s) 422
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Other crustaceans
Class Maxillopoda
Order Copepoda Order Leptostraca
“Leptostracans are usually small, typically 5 to 15
millimetres (0.2 to 0.6 in) long,[6] crustaceans
distinguished from all other members of their class in
having seven abdominal segments, instead of six.
1) Very small!
2) Cephalic ‘shield’
3) Naupliar eye
The carapace is large and comprises two valves which
cover the head and the thorax, including most of the
thoracic appendages, and serves as a brood pouch for the
developing embryos. The first six abdominal segments
bear pleopods, while the seventh bears a pair of caudal
furcae, which may be homologous to uropods of other
crustaceans.”
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Wikipedia.org/wiki/leptostraca
Other crustaceans
Phylum Mollusca
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Assiminea californica
Not to be confused with Alia carinata, these guys are found in
more southern waters such as South Bay and are extremely
abundant. They are rounder and more squat. Also unlike Alia,
they are not found with algae covering their shells. They
appear smooth and brown under the scope.
LSM page(s) 730
Volvarina taeniata (taeniolata)
Very distinctive gastropod, they have the exact body shape as
the figure, but can have varying colorations. Things to look for
is the large open-slit shaped aperture that spans the entire
length of this organism and the spiraled cone at the top.
Alia carinata
Sometimes called Mitrella carinata. Generally larger then
Assiminea californica, they are often found covered in algae
and appear dark black or brown under the scope. They have
also been known to have white spots in a ring around the
circumference of the shell, this is common when they are
found in South Bay but not in Shelter Island. They do not have
a circular aperture as Assiminea does. Extremely abundant
around Shelter Island.
LSM page(s) 744.
Bulla gouldiana
Gould’s Bubble Snail or California Bubble Snail. Really
distinctive shell shape with an overall aperture, which is most
wide anteriorly. Their eggs (‘yellow spaghetti) are frequently
found on eelgrass and sometimes in samples. Be sure to
carefully check the eggs for inconspicuous crustaceans. 33
Gastropods
Common.
Crepidula sp.
Called the ‘slipper limpet’. Often found on other molluscs
(especially oysters), crabs, or rocks. The images above serve
as a general body plan reference.
Crucibulum spinosum
Called the ‘spiny cup-and-saucer snail’, this limpet is common
on dead oyster shells.
Tectura depicta
Most common limpet that you’ll find. Very abundant around
Shelter Island. They have distinct orangeish brown chevrons
and range from very tiny to 1 centimeter in length.
LSM page(s) 756
Scallops
E.g. Argopecten aequisulcatus, Argopecten ventricosa,
Leptopecten latiauratus. A. aequisulcatus, the speckled
scallop, is common in eelgrass. As adults, they can be 2 to 4
inches long and are rounded with projecting wings of unequal
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size and 21 radiating ribs. The color varies.
Gastropods, Bivalve
Musculista senhousia
Mytilus sp. (mussels)
The invasive bivalve also known as the Asian Mussel. Sizes range
from a couple millimeters to several centimeters. They have
beautiful colorations and are darkly opalescent with brown stripes.
They are commonly found in a cocoon made of mucus and
sediment near seagrass roots.
LSM page (s) 521
Chione undatella
This tiny bivalve has horizontal and vertical ridges down the
length of its shells starting from the hinge. The horizontal
ridges tend to be more lifted than the vertical ridges. Has been
found in South Bay eel grasses.
Macoma nasuta
Very fragile, will probably break as soon as you try to handle it.
They are usually white and have very fine horizontal ridges
with some discolorations and are opalescent. The description
is for juveniles as that is what we are finding. Found in South
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Bay eelgrass.
Bivalves
Others
Polychaetes
‘Poly-keets”. See figure for diversity of forms.
Most common form is a worm with eyespots
and conspicuous parapodia! Sometimes they
are found in sediment-covered tubes, be sure to
check those. One of the Annelid worms.
Fishes
You may occasionally find juvenile fishes,
such as bass, gobies, or pipefish.
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Misc.
Others
Pycnogonids
Midge Fly larvae
‘Sea spiders’ are really distinctive arthropods
(they aren’t crustaceans though!). They are
uncommon in our samples.
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Misc.
Unidentified
This is iridescent…what is it? I
think I’ve seen it