Lab IV: Anurans Comprising approximately 5,569 species, frogs and toads are by far the most diverse of the three extant lineages of amphibians (Caudata approx. 562 sp., Gymnophiona approx. 175 sp.). Currently anurans are classified in approx. 29 families; however, the phylogenetic relationships of the families and higher level taxonomy are not well established. Anurans are found everywhere in the world except for Arctic and Antarctic latitudes, some oceanic islands, and very dry deserts. The earliest known fossil of an anuran is the Leiopelmatid Vieraella from the Lower Jurassic (~160-180 MYA) in South America. The majority of extant species and endemic families of anurans are found in the tropics of Asia, Africa, and South America. If anyone has a desire to describe a new species that is a tetrapod, your best bet would be to study tropical frogs. Anurans are easy to recognize with elongate hind-limbs, fused ulna and radius, fused tibia and fibula, small number of presacral vertebrae (mode = 8), the fusion of postsacral vertebrae into the urostyle, the presence of transverse processes on all vertebrae, and general reduction or absence of ribs. Anurans exhibit a wide variety of reproductive strategies (wonderfully outlined in Duellman and Treub Ch. 2) with external fertilization in most species. The mode of reproduction that is thought to be primitive involves aquatic eggs and aquatic larvae. Frogs have diversified from this general mode, with many lineages exhibiting terrestrial deposition of eggs with aquatic larvae, terrestrial eggs with direct development (no tadpole), ovoviviparity, and viviparity. Goals: In this lab we will examine the diversity of the frogs and toads through the use of preserved material. You are to use the dichotomous key provided to help guide you through identification. It is imperative to use this key so you can focus on the characteristics that diagnose the different species, genera and families, you will be responsible for knowing these diagnostic characters. You are responsible for being able to identify any of the lab specimens on an exam. You are required to know all Illinois specimens to the species level; non-illinois, U.S. specimens to the genus level; and non-u.s. specimens to the family level. Full credit on exams is given only for the proper scientific name; use of the common name on exams will be worth only half credit. Further, you should know the distribution of the Illinois species within the state, the genera within the U.S., and the families in the world. Please note, as before that preservation in ethanol will eventually remove the natural colors from a specimen. The colors indicated below may therefore not be present in some specimens. 1
ORDER ANURA Family Ascaphidae (Tailed Frogs) Ascaphidae is monotypic (Ascaphus truei). This family, along with the Leiopelmatidae, are considered to be the most primitive groups of extant anurans. Ascaphidae occurs in the Pacific Northwest of North America. These primitive frogs are characterized by having vestigial tail wagging muscles, free ribs in adults, nine ectochordal-amphicoelous pre-sacral vertebrae, arciferal pectoral girdle, and inguinal amplexus. Distribution: Pacific Northwest. Ascaphus Tailed Frog males develop a tail-like copulatory organ cryptically colored lacks tympana strongly webbed hind feet Ascaphus is one of the most interesting frogs found in North America. The most obvious morphological feature of this frog is the extension of the cloaca (not really a tail), which is used as a copulatory organ for internal fertilization. This is a unique and interesting exception, as the vast majority of anurans exhibit external fertilization. Tailed frogs are nocturnal, hiding under rocks and debris along fast-flowing streams during the day and emerging to feed at night. Courtship and reproduction occurs in late summer; however, females do not lay eggs until the following summer. Several features of Ascaphus appear to be adapted for life in fastflowing streams, these include the presence of strongly webbed hind-feet, absence of tympana, and tadpoles which are streamlined with a modified oral disc that acts like a ventral sucker. Distribution Pacific Northwest. The monotypic genus Ascaphus is found between the Cascade Mts. And coastal southern British Columbia through western Washington and Oregon into northwestern California. A disjunct population extends from the Blue Mts. Of southeastern Washington and northeast Oregon through central Idaho into western Montana. Family Bombinatoridae (Fire-Bellied Toads) 2
The Bombinatoridae consist of about 10 species in 2 genera. They get their name from their brightly colored ventral side which they display to predators by arching their back (called the unken reflex). This display acts as a warning of their toxic skin secretions. Members of the genus Bombina are quite popular in the pet trade and sell for the bargain price of approx. $5 at some local pet shops. Distribution Europe, Asia, Philippines, and Borneo Family Bufonidae (True Toads) Bufonidae consists of 35 genera which contain approximately 511 species. They are characterized by 5-8 holochordal-procoelous presacral vertebrae, no ribs, arciferal or pseudofirmisternal pectoral girdle, and axillary amplexus. Most toads have thick glandular skin with or without warts. The genus Bufo has parotoid glands. Most bufonids are terrestrial or fossorial and have short limbs. Distribution - The bufonids have a cosmopolitan distribution and are only absent from Australia, Papua-New Guinea, Madagascar, and Oceanic regions. Bufo americanus - American Toad dry, warty skin cutting tubercles on heel of hind-foot prominent parotid glands horizontally elongate pupils one or two large warts in each of the largest dark spots parotoid gland separated from postorbital ridge or connected to ridge by a spur venter is usually spotted with dark pigment tibial warts are larger than femoral warts Bufo americanus is found in all sorts of habitats, from suburban backyards to forest floors. All that seems to be required is shallow bodies of water in which to breed, moist hiding places, and an abundant supply of invertebrates for food. In Illinois the peak of the breeding season is mid-april. Illinois Distribution - This species is widespread in the state, absent only from the east-central portion of Illinois along the Wabash River Drainage. Status - Common Bufo fowleri - Fowler s Toad 3
dry, warty skin cutting tubercles on heel of hind foot prominent parotoid glands horizontally elongate pupils three or more small warts in each of the largest dark spots parotoid gland touches the postorbital ridge venter is usually unspotted tibial warts are smaller than femoral warts Like the closely related B. americanus, B. fowleri is found in all sorts of habitats. In Illinois, breeding occurs in shallow bodies of water from late April to June, the peak occurring in mid-may. Illinois Distribution - This species occurs throughout the southern two-thirds of the state. Status - Common Family Centrolenidae (Glass Frogs) Centrolenids are called glass frogs because the skin on the venter is transparent, which allows the viscera to be seen through the body wall. The family is moderately diverse with three genera containing approx. 129 species in 5 genera. Similar to Hylidae, there is a short cartilaginous intercalary element between the penultimate and terminal phalanges. The T-shaped terminal phalanges and the presence of a medial protuberance on the third metacarpal can distinguish centrolenids from the hylids. Other characteristics include eight holochordal-procoelous presacral vertebrae, no ribs, arciferal pectoral girdle, horizontal pupil, and axillary amplexus. There is no known fossil record. Centrolenids are most diverse in wet mountain forests, and tremendous numbers of new species are being discovered in the Andes. Eggs are laid on rocks or leaves above streams and are usually attended by the male. Hatching tadpoles fall into the water and develop in oxygen poor areas in gravel or detritus. Distribution - Southern Mexico to Bolivia and northern Argentina. Family Dendrobatidae (Poison Arrow Frogs) This is a moderately diverse family, 12 genera containing approximately 167 species of small frogs that are famous for their exquisite color patterns and toxicity. The fingers of dendrobatids bear a pair of dermal scutes on the dorsal surfaces. There are 4
eight holochordal-procoelous presacral vertebrae, ribs are absent, pectoral girdle is firmisternal, the pupil is horizontal, and amplexus is cephalic or absent. The species of dendrobatids that are the most toxic have bright aposomatic coloration. The toxin is a lipophilic (soluble in lipids) alkaloid. In some cases 0.2 mg is a lethal human dose. Not all dendrobatids are highly toxic and in these cases aposomatic coloration is absent. There seems to be a dietary origin for the Dendrobatid toxins, with certain beetles and ants being the likely sources. The vast majority of dendrobatids are diurnal and terrestrial. Small clutches of eggs are laid in terrestrial or arboreal locations and attended by a parent. Once eggs hatch, tadpoles are carried on the dorsum of a parent and carried for a period before being deposited in water. The females of some Dendrobates species deposit eggs in arboreal sites, returning occasionally to deposit unfertilized eggs, which serve as food for the tadpoles. Distribution - Southern Central America to the northern half of South America. Family Discoglossidae (Disc tongued Frogs and Midwife Toads) There are 2 genera and approximately 11 species in this family. Extant species of Discoglossidae range from small toad-like terrestrial species to large aquatic species with webbed fore- and hind-limbs. Eight stegochordal-opisthocoelous presacral vertebrae, presence of ribs, arciferal pectoral girdle, inguinal amplexus, external fertilization, and aquatic larvae characterize Discoglossidae. Fossils of Discoglossidae are found in Europe and Montana from the Upper Jurassic-Lower Cretaceous (~140-120 MYA) to the Miocene (~26-15 MYA). The genus Alytes is a small toad-like terrestrial anuran where the male carries the eggs on the back and thighs and enters water when they are ready to hatch. Distribution Europe and Northwestern Africa. Family Hylidae (Treefrogs and Allies) Hylids are a widespread and diverse group of anurans. There are 849 species grouped in 49 genera. Distinguishing characters include well-developed toe discs, clawshaped terminal phalanges, and intercalary cartilages that separate the penultimate and terminal phalanges. Other characteristics include eight holochordal-procoelous presacral vertebrae, arciferal pectoral girdle, horizontal pupil, and axillary amplexus. Most hylids are arboreal; however a few species are aquatic or fossorial. Reproduction is diverse in the family and includes aquatic eggs and larvae, eggs laid on vegetation over water- into which hatching tadpoles drop, eggs deposited in water-filled cavities in trees, and brooding the eggs on the dorsum of females. Both direct and indirect development is present. Distribution - North America, Central America, West Indies, South America, Australia, Tasmania, New Guinea, and the Solomon Islands. 5
Acris crepitans - Cricket Frog digital toe pads are narrow toes are fully webbed dark stripe on back of thigh with irregular edges dark triangle between the eyes numerous small warts usually present Cricket frogs are common and occupy both terrestrial and aquatic habitats. This hylid is not arboreal, as evidenced by the reduced toe pads. Breeding in Illinois extends from April through the summer. Eggs are laid in water. Tadpoles are easily recognized by the presence of a black-tipped tail. Distribution in Illinois - This frog is everywhere (except perhaps in NE Illinois)! Localities are documented from all over the state. Status - Common Pseudacris crucifer - Spring Peeper digital pads are distinctly wider than penultimate joints a distinctive X mark is present on the dorsum dark mark is present between the eyes lateral stripe continues past the eye along the side of the body The spring peeper inhabits mesic forests, living in trees or on herbaceous plants. It is abundant around woodland ponds in early spring but is difficult to find at other times of the year. Breeding season in Illinois occurs from early March to early June. Eggs are laid in water. Phil Smith (Illinois herpetologist) notes that P. crucifer does not occur in forest islands that are surrounded by cultivated fields, but only occurs in unbroken forested areas along rivers. Distribution in Illinois Statewide Status Common Pseudacris feriarum - Upland Chorus Frog usually with three broad dark stripes running down the dorsum that are broken into dots or dashes webbing absent between toes slightly expanded toe pads 6
dark triangle between the eyes may be present dark lateral stripe continues well past the eye a light line along the upper lip is present P. feriarum is a terrestrial frog that is usually only encountered during the breeding season. Breeding occurs in temporary ponds and ditches. The breeding season extends from February into May, the peak occurring in early March. Eggs are laid in water. Distribution in Illinois - Extreme southern portion of the state. Status Common in Southern counties Pseudacris streckeri - Strecker's Chorus Frog (Illinois Chorus Frog) robust body with thick forelimbs a dark spot below the eye is present a dark lateral stripe passes through the and ends at the shoulder Like other species of Pseudacris, P. streckeri is usually only encountered during the breeding season. Breeding occurs from the beginning to the end of March. Eggs are laid in water. Illinois P. streckeri are disjunct from the rest of the species (occurs in Oklahoma and Texas). Populations in Illinois occupy sand prairie habitats and provide evidence to support the Prairie Peninsula hypothesis (Dr. Phillips will discuss this in lecture). Distribution in Illinois - Sand prairies in Morgan, Cass, Mason, and Tazewell counties along the Illinois River. Status Threatened in Illinois Pseudacris triseriata - Western Chorus Frog usually with three broad dark stripes running down the dorsum webbing absent between toes slightly expanded toe pads dark triangle between the eyes may be present dark lateral stripe continues well past the eye a light line along the upper lip is present P. triseriata is a terrestrial frog that is usually only encountered during the breeding season. Breeding occurs in temporary ponds and ditches. The breeding 7
season extends from March into May, the peak occurring in late March. Eggs are laid in water. Distribution in Illinois Statewide except the extreme southern portion of the state. Status - Common Hyla avivoca- Bird-voiced treefrog : Smooth skin Light spot under each eye Dark bars on arms and legs Green to yellow yellowish green patches in groin and inner thigh H. avivoca inhabits bald cypress tupelo swamps. In Illinois, breeding occurs from mid-may to August. Status: Threatened. Distribution in Illinois Limited to extreme southern tip of the state Status Threatened in Illinois Hyla cinerea - Green Treefrog usually bright green (before treatment with formalin!) white or yellow stripe along sides of body, length of stripe variable smooth skin rear of femur unmarked H. cinerea inhabits cypress swamps, areas along floodplain sloughs, and in cattail marshes. Breeding season in Illinois is thought to begin in May. Eggs are laid in water. Distribution in Illinois - Limited to the extreme southern tip of the state Status Locally Abundant Hyla versicolor-chrysoscelis - Gray Treefrog light spot under eye dorsum and limbs with irregular dark bands or blotches skin rough 8
rear of femur (in life) bright orange with dark mottling The gray tree frog inhabits forested areas and is arboreal. In Illinois breeding occurs from late April to August, the peak in late May. Eggs are laid in water. Distribution in Illinois Statewide Status - Common Family Leptodactylidae (Southern Frogs) Leptodactylidae with 60 genera and approximately 1,345 species is the most specious family of anurans. Morphologically and ecologically leptodactylids are extremely diverse. Some are toad-like, some are large-headed carnivores, and some are strictly aquatic. Reproduction in Leptodactylidae is also diverse and includes aquatic eggs and tadpoles, terrestrial nests and tadpoles, terrestrial eggs with hatching tadpoles moving to water, and direct development of terrestrial eggs. They are sometimes called narrow-toed frogs because both the fore- and hind-limbs lack webbing. Other characteristics of the family include eight holochordal-procoelous presacral vertebrae, no ribs, arciferal pectoral girdle, and axillary amplexus in all but three genera. Fossil record is extensive throughout the Cenozoic of South America. This family includes the well known pac-man frog (Ceratophys ornata), popular in the pet trade. Distribution - South America, southern North America, and the West Indies. Family Microhylidae (Narrow-mouthed Toads) Microhylids are a diverse family with 70 genera which contain approximately 433 species. The family exhibits variable morphologies and life histories. Since we only have a single species in Illinois, we will not discuss the range of diversity in lab. However, characteristics of the family include eight holochordal-procoelous presacral vertebrae, no ribs, firmisternal pectoral girdle, and axillary amplexus. Distribution - Cosmopolitan, except for Europe and temperate Asia, most of Australia, West Indies, and oceanic islands. Gastrophryne carolinensis - Eastern Narrowmouth Toad small plump frog very pointed snout fold of skin across the back of the head G. carolinensis is a terrestrial woodland frog. Eggs are laid in water. Tadpoles of G. carolinensis are the only ones in Illinois that have an oral sucking disc. 9
Distribution in Illinois - Confined to southwestern areas of the state along the Mississippi River. Status May be locally common within its small range Family Myobatrachidae (Terrestrial Australian Frogs) This is a large family of frogs with 20 genera and approximately 126 species. The large number of species is paralleled by an amazing level of morphological and life history variation. Myobatrachids are characterized by the persistence of the notochord in adults, eight presacral vertebrae, no ribs, arciferal pectoral girdle, and inguinal amplexus. Fossils of Myobatrachidae date from the Eocene, Miocene and Pleistocene of Australia. The range of extensive diversity in this family makes it hard to provide good characters for diagnosis in the lab specimens. The representative species that we have chosen for this family will be easy to recognize because they look like other families that we are studying today. For instance, Myobatrachus looks surprisingly similar to Rhinophrynidae (Mexican Burrowing Frog) and Heleioporus is very similar to Scaphiopus holbrooki (even the tarsal pad on hind-foot is shared between these two taxa). These similarities have evolved as a result of convergent evolution. The specimens of this family are presented to 1) attempt to cover a major component of the Australian anuran fauna, and 2) to present some striking exampls of convergent evolution in anurans. Distribution - Endemic to Australia, New Guinea, and Tasmania. Family Pelobatidae (Spadefoot Toads) There are 3 genera and approximately 11 species in this family. Eight stegochordal-procoelous presacral vertebrae, no free ribs, arciferal pectoral girdle, and inguinal amplexus characterize pelobatids. Pelobatids have an extensive fossil history extending from Late Cretaceous of North America and Asia and the middle Eocene of Europe through the Pleistocene. The common name for the family comes from the large keratinous tubercle (similar in consistency to a callus) that is present on the outside edge of each hind-foot. This structure allows pelobatids to burrow rear first by alternating movements of the hind-limbs. Distribution North America, Europe, northwest Africa, southeast Asia, Pakistan to northern India and China, and the Philippines. Scaphiopus holbrooki - Eastern Spadefoot one elongate, cutting tubercle present on heel of each hind-foot vertically elongate pupil males have stout fingers and black horny deposits on upper surface of first 10
and second fingers light colored crescentric lines extending from behind the eyes to the middle of the back chin and venter unspotted inconspicuous parietal glands In Illinois S. holbrooki breeding has been observed in May and August. Breeding sites are temporary ponds following heavy summer rains. Hatching of eggs and development of tadpoles is rapid, requiring a total of only 2 to 3 weeks. Because of its subterranean existence, S. holbrooki is usually found only in breeding ponds. Phil Smith tells of capturing S. holbrooki by following farmers while plowing and by raising logs on the forest floor. Illinois Distribution - In Illinois, S. holbrooki is found only in the southern tip of the state. Status Largely unknown due to secretive habits, thought to be common Family Pipidae (Pipas & Clawed Frogs) Pipids consist of approximately 31 species in five genera. These frogs are entirely aquatic. Characteristic of pipids is the strong webbing of the hind-limbs, long un-webbed fingers, presence of a lateral-line organ, small eyes, and no tongue. Other features include 6-8 epichordal-opisthocoelous presacral vertebrae, presence of ribs in adults, pseudofirmisternal pectoral girdle, and inguinal amplexus. Tadpoles have barbels and are pelagic filter feeders. Pipids have an extensive fossil record from the Lower Cretaceous to the Paleocene. The genus Xenopus should be familiar as the ubiquitous African Clawed Frog of the pet trade. Xenopus is an important laboratory organism used in reproductive physiology, development, and molecular genetic research. Some of the Xenopus species are polyploid. The genus Pipa contains a species whose eggs are imbedded on the dorsal skin of the female, where they develop directly into froglets. Distribution - Tropical South America and sub-sahara Africa Family Ranidae ( True Frogs) There are 51 genera and approximately 821 species in this family. If you were to close your eyes and think of a frog, more than likely you would envision a ranid. There are really no defining characteristics for the family; however, all you will need to study for this course are the species that occur in Illinois. Characteristics of Ranidae include eight holochordal-procoelous presacral vertebrae, firmisternal pectoral girdle (arciferal in some species of Rana), and axillary amplexus. Ranids tend to have long legs, narrow waists, smooth skin, and digits that lack terminal toe pads. The family is diverse and may not represent a monophyletic group. 11
Distribution - Ranidae is cosmopolitan except southern South America, the West Indies, most of Australia, and most oceanic islands. Rana areolata - Crayfish Frog plump frog large head short legs dorsum covered with dark round spots surrounded by a light border that are closely crowded together mottled upper jaw prominent hump at middle of back tympanum smaller than eye dorsolateral folds extend the length of the back R. areolata occupies abandoned crayfish burrows except in breeding season. Breeding season occurs in March to mid-april. Eggs are laid in water and tadpoles transform in late June through early July. Distribution in Illinois - Southern half of Illinois, absent north of the Shelbyville Moraine. Status Declining Rana blairi- Plains Leopard Frog light spot on tympanum distinct line extends from upper jaw (near tip of snout) to tympanum or slightly beyond pale borders around dorsal spots very pale or absent dorsal spots rounded and dark brown dorsolateral fold along sides interrupted near posterior end and offset towards midline dark spot on snout R. blairi occurs and can hybridize with the southern leopard frog (R. sphenocephala). Adults breed from March to April, sometimes in large numbers. The female lays from 3 to 7000 eggs with tadpole transformation occurring in mid-summer. Distribution in Illinois Primarily central Illinois 12
Status Widespread but not locally abundant Rana catesbeiana - Bullfrog no dorsolateral folds on back tympanic fold prominent webbing extending to tips of toes dorsum lacking discrete dark spots Bullfrogs are the largest of the Rana species in Illinois. It can be found in almost any type of permanent water bodies, such as lakes, ponds, rivers, and streams. Breeding in Illinois occurs from late April to early August. Males are territorial and vigorously defend home patches along the water edge. Eggs are laid in water and tadpoles over-winter and do not metamorphose until the following summer. Distribution in Illinois Statewide Status - Common Rana clamitans - Green Frog dorsolateral folds present but terminate just beyond mid-back tympanic fold inconspicuous dark spots are usually present on chin, breast, and undersides of legs R. clamitans seems to be most common in clear, small streams with rock outcrops. Breeding occurs from May to September. Eggs are laid in water and tadpoles over-winter and metamorphose the following summer. Distribution in Illinois - Present throughout the state, but absent from a significant portion of central Illinois that corresponds to the Grand Prairie. Status - Common Rana palustris - Pickerel Frog two parallel rows of dark rectangular spots that run between the dorsolateral folds 13
dorsolateral folds extend the length of the back tympanic fold inconspicuous hidden surfaces of hind legs and belly yellow (in life) R. palustris is found in a variety of aquatic habitats. Breeding occurs in slow moving bodies of water. Distribution in Illinois - Found in the extreme northern portion of the state and along the entire western edge adjacent to the Mississippi River. Status - Uncommon Rana pipiens - Northern Leopard Frog two or three rows of irregular round spots with white borders run between the dorsolateral folds numerous dark spots on the sides of the body light line is present on the upper jaw dorsolateral folds extend the length of the back tympanic fold inconspicuous R. pipiens is found in permanent bodies of water; however, it is also terrestrial. Breeding occurs from mid-march to May. Eggs are laid in water and tadpoles metamorphose from June to late August. Distribution in Illinois - Documented throughout the northern half of the state. Status Locally abundant Rana sphenocephala - Southern Leopard Frog two or three rows of irregular round spots that lack white borders run between the dorsolateral folds few dark spots on the sides of the body often a white spot on the tympanum light line is present on the upper jaw dorsolateral folds extend the length of the back tympanic fold inconspicuous The habits of R. sphenocephala are similar to R. pipiens. Breeding occurs earlier, starting in early March and extends into April. Eggs are laid in water and tadpoles metamorphose in June and early July. 14
Distribution in Illinois - Southern half of the state. Status Common in southern half of state Rana sylvatica - Wood Frog a prominent dark mask passes through the eye and tympanum dorsolateral folds extend the length of the back tympanum smaller than the eye tympanic fold inconspicuous no distinct spots on dorsum R. sylvatica (as implied by the species name) inhabits mesic forests with permanent or semi-permanent pools. They are solitary and in summer months appear to be entirely terrestrial. Breeding season is short and occurs in March (which is early for Ranids). The species is an explosive breeder with large congregations of breeding adults that disappear after a week or two. Eggs are laid in water and tadpoles transform in May and June. Distribution in Illinois - Eastern Illinois along tributaries of the Wabash R., southwestern Illinois, northwestern Illinois, and northeastern Illinois. Absent from the central parts of the state. Status Scattered range, can be locally abundant Family Rhacophoridae (Asian Treefrogs) 11 genera and approximately 293 species make up this family. Rhacophorids seem to be the ecological equivalent of Hylids. They have enlarged toe pads, large eyes with horizontal pupils, and some species have extensive webbing between their toes allowing them to glide through the air. Dorsal coloration varies, and many species also have flash patterns on their venter and inner thighs. Distribution - Asia Family Rhinophrynidae (Mexican Burrowing Frog) This monotypic family is characterized by the cone-shaped head, which has a small, calloused snout at the end. Other features include short limbs; robust flattened body, no free ribs, ectochordal-opisthocoelous vertebrae, eight presacral vertebrae, an arciferal pectoral girdle, and inguinal amplexus. Tadpoles have barbels and are pelagic 15
filter feeders. Fossil forms have been found from the Late Paleocene (~54 MYA) and the middle Eocene (~40 MYA) of Wyoming. Rhinophrynus dorsalis is unique among anurans in having a tongue that is catapulted out of a small mouth. The specialized head, tongue, and body are used for a fossorial existence where termites and ants make up its diet. Distribution - Mexico to Costa Rica, reported from extreme southern Texas. 16
Lab IV: Frogs and Toads Handout- Characteristics of Anurans A.) Tadpole Types A) Type I: No cornified beak or teeth, paired lateral spiracles (Pipidae, Rhinophrynidae). B) Type II: No cornified beak or teeth, a single midventral spiracle (spatulate lower lip) (Microhylidae). C) Type III: Cornified beak and teeth, a single midventral spiracle (Ascaphidae, Discoglossidae) D) Type IV: Cornified beak and teeth, a single spiracle on left side of center (sinistral). All other families E) Unusual larva (Otophryne robusta) 17
B.) Vertebral Types 1) Vertebrae are all derived embryologically from the hollow perichordal sheath. Three types can be distinguished: Holochordal: Entire vertebra ossified (most families) Ectochordal: Only a ring ossified, notochord persistent internally (Ascaphidae, Rhinophrynidae) Stegochordal: Only dorsal third ossified, flattened notochordal reminant present below arched centrum (Pipidae, Discoglossidae, Pelobatidae) DIAGRAMATIC CROSS-SECTIONS OF VERTEBRA: Bone Notochord Holochordal Ectochordal Stegochordal 2) Anuran vertebral centra and intervertebral bodies develop, respectively, as thin and thick cylindrical segments that alternate along the length of an unbroken fibrocartilagenous perichordal tube. The intervertebral elements chondrify more rapidly than the centra (i). At the juvenile stage, the vertebral column consists of a chain of ossified centra linked by undivided intervertebral cartilages (ii) with both centra and intervertebral bodies pierced by a continuous strand of notochordal tissue. Each intervertebral body is now invaded from the periphery by an arc of connective tissue that divides the intervertebral body into two unequal portions: a small cup and a larger ball. Each part remains attached to a centrum - the anterior part forms the posterior face of the centrum in front of the intervertebral body, the posterior part of the intervertebral body forms the anterior face of the vertebra immediately behind the intervertebral body (iii, iv). If the arcs are such that a cup is attached to the anterior face of the vertebra and a ball is attached to the posterior face, that vertebra is procoelous (iii). If all the vertebrae are procoelous, the vertebral column is also procoelous. Conversely, if the arcs are such that the cup is attached to the posterior face of the vertebrae with the ball anteriorly, the vertebra is ophisthocoelous (iv). A column of uniformly ophistocoelous vertebra is also ophistocoelous. Occasionally two arcs invade one intervertebral body forming two cups one attached to each centrum, and a free median movable ball (anomocoelous). If a vertebra has cups attached to both ends it is amphicoelous (v). A vertebral column in which the first presacral vertebra is amphicoelous and all other presacral vertebra are procoelous, the column is termed diplasiocoelous. DIAGAMMATIC REPRESENTATION OF VERTEBRAL TYPES: 18
Centrum Intervertebral body anterior Centrum Intervertebral body Centrum i-perichordial sheath ii-early development iii-procoelous iv-ophistocoelous v-amphicoelous, free discs Dorsal view of the vertebral columns of (A) Ascaphus truei (ectochordal, acoelous), (B) Pipa myersi (stegochordal, ophistocoelous), (C) Leptodactylus pentadactylus (holochordal, procoelous), and (D) Rana esculenta (holochordal, procoelous). 19
C.) Pectoral Girdles Pectoral Girdles can be divided into two types: Firmisternal - Epicoracoids are fused both anteriorly and posteriorly (and usually mesially). Epicoracoids never have posterolateral extensions (horns); sternum fused to posterior junction of epicoracoids. Arciferal - Epicoracoids with free posterolateral extensions that typically fit into grooves in front of sternum. Sternum never fused with epicoracoids. Epicoracoids usually fused only anteriorly, being free and overlapping mesially and posteriorly. Firmisternal girdle (Kaloula pulchra) Arciferal girdle (Bufo coccifer) Abbreviations: cl, clavicle; cor, coracoid; epc, epicorocoid; sc, scapula; ssa, suprascapula; Lab IV: Frogs and Toads - Vocalizations GOALS: Familiarize yourself with the different types of anuran vocalizations. You will only be responsible for knowing the calls of the anurans from Illinois. I. HOW SOUND IS PRODUCED Sound in most tetrapods is produced through the voice box (laryngeal apparatus), which is composed of the larynx and the vocal chords. In most frogs the larynx is composed of two arytenoid cartilages that form compressed hemispheric structures. The arytenoid cartilages are situated within the cricoid cartilage at its base. It is within the lumen of the arytenoid cartilages that you find the vocal chords. The vocal chords are composed of flaps and strings of connective tissue. There is much musculature associated with the entire apparatus (see Duellman and Treub for more information on the structure of the laryngeal apparatus). Although both sexes have laryngeal apparatuses, it is only the males which posses vocal sacs. The vocal sacs are formed as a diverticuli of the lining of the buccal cavity and act as resonators. In sound production the larynx acts as transducer converting muscular activity to acoustic energy. There are two cycles, the oscillatory cycle and the ventilatory cycle. The oscillatory cycle involves respiration and exchange of the air in the buccal cavity. The ventilatory cycle is more complex and air is pumped into the lungs in two stages. First, air is pumped from the outside to the buccal cavity prior to the exhalation of pulmonary air through the larynx. Second, air goes from the buccal cavity to the lungs after exhalation. Prior to vocalizing, some muscles constrict and some dilate to retract the laryngeal apparatus locking the arytenoids cartilages into place. Then pulmonary air rushes over the vocal chords creating sound. The frequency of the sound varies depending upon the tension of the vocal and the mass of the arytenoids cartilages. II. TYPES OF VOCALIZATIONS 20
Advertisement Calls. These calls are emitted to attract conspecific females (courtship calls), or define territorial boundaries (territorial or encounter calls). The latter two are specific to male-male interactions. A resident male in response to an advertisement call produces Territorial calls, whereas encounter calls are evoked during close range interactions between males. Reciprocation Calls. In some species, receptive females give reciprocation calls. An example of this is the European discoglossid Alytes obstetricans. Release Calls. Either an unreceptive female or a male in response to amplexus evokes a response call. These calls often are emitted as a series of short chirps. The release signals may inform the amplexing male the partner is incapable of reproducing. These calls are unknown in the microhylids. Distress Calls. Distress calls are loud vocalizations, usually with the mouth open, in response to disturbance. It is unknown if they convey and information to other individuals. These calls are unlikely to startle a snake; however, loud vocalizations may surprise a mammalian or avian predator allowing the frog to escape. III. THE CALLS OF THE FROGS AND TOADS OF ILLINOIS. CDs containing all of the following calls are available to check out from the TAs. Calls of many of the species below are also available as WAV files at various Internet sites. Use your search engines! A. Ranidae a. Rana catesbeiana b. Rana clamitans c. Rana sylvatica d. Rana pipiens e. Rana sphenocephala f. Rana palustris g. Rana areolata B. Hylidae a. Acris crepitans b. Pseudacris crucifer c. Pseudacris triseriata d. Pseudacris streckeri e. Hyla avivoca f. Hyla cinerea g. Hyla versicolor h. Hyla chrysocelis C. Bufonidae a. Bufo americanus b. Bufo fowleri D. Pelobatidae a. Scaphiopus holbrooki E. Microhylidae a. Gastrophryne carolinensis 21