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. 1 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. 2 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 3 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. 4 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 6 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 8 9 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 10 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. 11 Adapted from Barnard and Karaman 1991, SD guide 2013 Gammarids 12 Suborder Gammaridea 13 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. 14 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. 15 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) 16 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) 17 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 18 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 19 Gammarids Podoceridae Taxon PODOCERIDAE telson spinose, pleopods powerful, eyes bulge laterally. 20 Gammarids Melitidae??? ?? 21 Gammarids Ampeliscidae??? Stenothoidae?? STENOTHOIDAE coxa 3 and 4 massive, coxa 1 small, obscured, distal telson bluntly acute, tongue-like. 22 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 23 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. 24 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. 25 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 26 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 27 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. 28 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 29 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 30 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.” 31 Wikipedia.org/wiki/leptostraca Other crustaceans Phylum Mollusca 32 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 34 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 35 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. 36 Misc. Others Pycnogonids Midge Fly larvae ‘Sea spiders’ are really distinctive arthropods (they aren’t crustaceans though!). They are uncommon in our samples. 37 Misc. Unidentified This is iridescent…what is it? I think I’ve seen it