Biol 119 Herpetology Lab 2: External Anatomy & an Introduction to Local Herps Fall 2013 Philip J. Bergmann Lab objectives The objectives of today s lab are to: 1. Learn the external anatomy of amphibians and "reptiles". 2. Learn to use external anatomy characteristics to identify species. 3. Familiarize yourselves with common local amphibians and reptiles. 4. Continue to hone your skills with your field guide. These skills will set a foundation for all future labs, so are important to get a grasp of early on. Familiarity with local species and your field guide will prepare you for the upcoming field trip. Tips for learning the material Get started by examining specimens that are on display. If you find some species hard to identify or distinguish don t get frustrated or overwhelmed because you will see these species again in future labs. Again, please read the lab prior to coming and refer to the course study guide for various suggestions for learning the material. Work through this lab and answer the questions that are posed in it. The questions are in bold text. The questions should help guide you through the material and get you to think about what you are looking at. You will discuss some of the questions from last week at the beginning of lab, so prepare for next week's lab so that you can participate in discussion. It is important that you look at the specimens and other material on display to answer the questions. Make sure that you look at all the material on display; don t skip or gloss over any of it. Take additional notes that will help you when studying. Take digital photographs of the specimens and note the scientific name of each. Find the species that you are looking at in the field guide to see how drawings and photographs compare to the specimen. The field guide describes many characteristics that can be used to distinguish species, so is a valuable resource. If you are unsure of what you are looking at or the answer to a question, discuss it with a fellow student. Working in partners is a productive way to reason through difficulties. Your instructors are also excellent resources that will be able to help you (although they won't just answer all the questions for you). 1
Exercise 1: External Anatomy of Amphibians and "Reptiles" An important skill for identifying amphibians and reptiles using field guides and taxonomic keys is to know the external anatomy of the animals. Different scales, grooves, and other structures are frequently referred to in descriptions. At the beginning of the Species Accounts section in your field guide you will find labeled anatomical diagrams. You should learn all of these terms and those defined below. Write a short definition for the following terms from the field guide. What clade of herps is each one relevant to? Nasolabial groove - Costal grooves - Dorsolateral fold - Cranial crest - Parotid gland - Wart - Carapace - Plastron - Bridge - Tympanum - The ear drum, posterior to the eye, is external and visible in many frogs, particularly ranids, and some lizards. Sacral hump - Mid-dorsal elevation in many frogs. Notice that the field guide has a page devoted to how measurements are taken of various herps. These are standard measurements that you should be familiar with. Note that what the guide calls "head-body length" is more commonly called "snoutvent length" or SVL in herpetology. In addition, the "anus" is often called the "cloaca" or "vent". 2
Also learn the names of the scales or scutes on the turtle shell, the lizard head and the snake head. The snake scales are sufficiently detailed in your field guide. Some more detailed views of lizard scalation are shown below (from Powell et al. 1998, Fig. 137). Below are some additional comments on some of the external anatomical structures to help you better understand what they are. Some of these terms are also new. Axilla this is the arm pit. Pores many lizard species have some sort of pores on the ventral side. These may be preanal pores, as seen in Coleonyx, postanal pores, as seen in some other geckos, or femoral pores, as seen in many iguanids (check on Dipsosaurus dorsalis). These pores often are more defined on males and are an imprecise way of sexing a lizard. Enlarged postanal scales these also appear on the ventral side of many iguanian lizards. These are a good way to determine the sex of individuals from species that possess them. Males have them, females don t. Look at some specimens of Callisaurus to see which ones are male and which are female. Draw a diagram of these scales here. 3
Lamellae these are the scales on the ventral side of the digits of the manus (hand) and pes (foot). The term is most commonly used when describing geckos that have adhesive pads on their toes, but can validly be used with other lizards as well. In padbearing geckos, the lamellae are specialized for adhesion. Lamellae are enlarged and composed of small hairs that facilitate adhesion with the substrate. In these geckos, the pads are also called scansors. In addition to all of these structures, you should be familiar with the anatomical locations: dorsal, ventral, lateral, anterior, posterior, cranial, caudal and medial. Identify these on the figure below. Powell et al. 1998, Fig. 137. Which anatomical location is not visible in the diagram above? Use all of these terms when talking to other students or the instructors, whether in lab or in the field. This will get you accustomed to using precise anatomical terms instead of referring to a structure as that thing. It will also help you learn the terms without having to rely on pure memorization. In addition to looking at the terms on these pages of your field guide, identify the structures on a number of specimens. Pick different looking species to do this on, as the scales can look quite different from one to another. Note their relative positions, and notice that their names often refer to their relative positions. For example, the postocular scales are behind the eyes, exactly where you would expect to find them. Similarly, the interparietal is between the parietals. Use the specimens that are available today to help you answer the following questions. How many costal grooves does Ambystoma maculatum have? What species of salamander on display has a nasolabial groove? 4
How many marginal shields does Gleptemys insculpta have? How about a Chelonia mydas? How many dorsal scale rows does a Thamnophis sirtalis have? How about a Diadophis punctatus? How many upper labials does Lampropeltis triangulum have? What type of scales does the lizard Sceloporus on display have? Name a species that has a dorsolateral fold. Name one that doesn t. Name a species that has a parotid gland. Using anatomical terminology, describe the position of the parotid gland. 5
Exercise 2: An Introduction to Local Herps Following is a list of the amphibians and reptiles that live in Massachusetts that are on display, organized by higher taxon (There are a number of species of herps that live in Massachusetts that we do not have in the lab, although you will not need to know these, it is important to be aware of them. At the end of the lab, you will list of these species). Work through the species on display, looking at the specimens and try to identify them. Take notes and pictures. Try to gain an appreciation for what groups of herpetofauna are diverse in Massachusetts and which ones are not. Try to write down identifying features that allow you to distinguish between similar looking species. Also, keep in mind that the color of the specimens fades with preservation they will look different in life, so compare what you are seeing in the lab with the pictures in your field guide. Salamanders and Newts (Urodela) Ambystoma maculatum - Spotted Salamander Ambystoma opacum - Marbled Salamander Desmognathus fuscus - Northern Dusky Salamander Eurycea bislineata - Northern Two-Lined Salamander Plethodon cinereus - Eastern Red-Backed Salamander Necturus maculosus - Mudpuppy Notophthalmus viridescens - Eastern Newt What is a characteristic that can be used to distinguish a salamander of the genus Ambystoma from other local salamanders? What is a feature that allows you to group Desmognathus fuscus, Eurycea bislineata, and Plethodon cinereus together? You may need to use a dissecting microscope to see it! Take a look at the mudpuppy on display. It is an adult. What feature does it have that most adult salamanders lack? Why does it have this feature? We have a number of Notophthalmus viridescens on display, but some of them look different from others (they may look like different species). How do they differ? Why (how can they both be the same species)? 6
Frogs and Toads (Anura) Anaxyrus americanus - American Toad Anaxyrus fowleri - Fowler's Toad Pseudacris crucifer - Spring Peeper Lithobates catesbianus - American Bullfrog Lithobates clamitans - Green Frog Lithobates palustris - Pickerel Frog Lithobates pipiens - Northern Leopard Frog Lithobates sylvaticus - Wood Frog Considering what a word means in Latin or Greek can help you remember all of these names. For example, macula is Latin for spot, silva is Latin for forest/woods, and the ura part of Anura refers to a tail in Greek, and an refers to a lack. Hence, A. maculatum is a spotted salamander, L. sylvaticus is a wood frog, and the Anura are frogs because they don't have an external tail. What is one feature that you can use to distinguish the genus Lithobates from other local frogs? Of the frogs on display, what is a unique feature of Pseudacris crucifer, and of the clade that it belongs to? Many of the frogs in Massachusetts have undergone taxonomic changes as scientists learn more about their relationships. What genera were Lithobates and Anaxyrus before these changes? It is important for scientists to be aware of the taxonomic changes, which is why we attempt to have the most up-to-date names in this course. Turtles and Tortoises (Testudines) Chelydra serpentina - Snapping Turtle Chrysemys picta - Painted Turtle Clemmys guttata Spotted Turtle Gleptemys insculpta - Wood Turtle Terrapene carolina - Eastern Box Turtle - We have the non-local T. ornata on display. Chelonia mydas - Green Seaturtle Sternotherus odoratus - Stinkpot What four clades of turtles are represented by the species on display? 7
What is a feature that can be used to unite the species of the clade to which four of the above belong to? Where in Massachusetts would you expect to find Chelonia mydas? Why? Lizards and Snakes (Squamata) Agkistrodon contortrix - Copperhead Coluber constrictor - North American Racer Diadophis punctatus - Ring-Necked Snake Heterodon platirhinos - Eastern Hog-Nosed Snake Lampropeltis triangulum - Milksnake Nerodia sipedon - Northern Watersnake Opheodrys vernalis - Smooth Greensnake Storeria dekayi - DeKay's Brownsnake Thamnophis sauritus - Eastern Ribbonsnake Thamnophis sirtalis - Common Gartersnake Note: the Common Five-Lined Skink, Eumeces fasciatus was the only lizard species to live in Massachusetts, but was extirpated in the 1800s. What is a key identifying feature of Diadophis punctatus? What is an identifying feature of species of the genus Thamnophis? How many species of the Opheodrys live in North America? What prey are Heterodon spp. specialized for eating? What is one way to distinguish a snake from a legless lizard? There are 51 species of amphibians (21) and "reptiles" (30, including 5 seaturtles) that live in Massachusetts, 29 of which are on display today (listed above). Given how far north Massachusetts is, this is considerable diversity. The prospects of learning to 8
identify all of these species may seem daunting, but don t panic here are some suggestions: 1. You will see all of these specimens again. Future labs will make all of these specimens available to you again. Next week this exact set of specimens will be out on display for use with the phyogenetics exercise. There will be two diversity labs and a review on amphibians, as well as two diversity labs and a review for reptiles. During those labs, you will see a greater range of species, but they will include subsets of the ones you see today. 2. Don t worry about learning to ID all of these today. It can be helpful to start by using a top-down approach. Notice that we have 2 species of Anaxyrus on display, as well as 2 species of Ambystoma and 2 species of Thamnophis. Start by figuring out how to identify these genera and concentrate on the species as the semester progresses. Be able to identify a toad, a mole salamander or a gartersnake before worrying about whether it is an American Toad or a Fowler's Toad. 3. Take notes and draw or take pictures. This has already been mentioned but is important. Active learning by is more effective than passive learning (just looking). To end this lab off, make a list of all Massachusetts species that are not mentioned above in the space provided. There are also good online sources that can help you. 9