Monophyletic clade. Synapomorphies include… –Smooth skin with mucous and granular glands What...

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• Monophyletic clade.• Synapomorphies include…

– Smooth skin with mucous and granular glands

What are Lissamphibia features?

• Synapomorphies include…– Germinal ridge origin of fat bodies

• Synapomorphies include…– Green rods in the retina– Levator bulbi muscles

• Synapomorphies include…– Pedicellate teeth

• Synapomorphies include…– 2 middle ear bones (stapes/operculum)

• Synapomorphies include…– 2 middle ear papillae (basilaris & amphibiorum)

• Respond to different frequencies of sound, one > 1 kHz and one < 1 kHz

• Compare ear bones and cochlea of humans to amphibians…

• Synapomorphies include…– Short, straight ribs (or missing)

• Synapomorphies include…– 2 occipital condyles– Loss of skull bones

(exceptions?!?)

Theloderma stellatum, Taylor's Bug-eyed Frog

• Synapomorphies include…– Cutaneous respiration & buccopharyngeal

pumping

http://www.youtube.com/watch?v=GU_VieIkDZE

• Gametogenesis (oo- and spermato- )

• Various states of “ploidy”

• Fertilization (internal/external?!?)

• Cleavage patterns and ovum/zygote fate

• Direct or indirect development?

Development & Growth

How do these embryological features relate to Deuterostomes and Protostomes?

• Radial cleavage

• Spiral cleavage

• Blastopore => mouth

• Blastopore => anus

• Enterocoely

• Schizocoely

Types of eggs:

Microlecithal – iso-lecithal distribution of yolk… found in placental mammals and amphioxus

Mesolecithal – telolecithal distribution of yolk concentrated at the vegetal pole… found in lampreys, bony fish, amphibians

Macrolecithal – telolecithal eggs… found in marine lampreys, cartilaginous fish, reptiles, monotremes

http://www.bio.unc.edu/faculty/harris/Courses/biol104/frog.jpg

Oviparity & Viviparity:

Animals that “lay” their eggs are considered oviparous.

Animals that give birth are considered viviparous.

If the embryo could develop without maternal tissue then ovoviviparous, while dependent strategies are euviviparous

No viviparous turtles, crocodiles, or birds

http://www.nationalaquarium.ie/images/dogfishEgg.jpg

Viviparity:

Histotrophic vs. placental nourishment

http://www.biologie.uni-hamburg.de/zim/herpe/bilder/Ichthyophis_Embryo.jpg

Life in cold blood caecilian clip

Fertilization:

Internal and external modes exist

In which type of “–parity” are eggs by necessity internally fertilized?

Usually external fertilization requires millions and millions of sperm

Urodeles (salamanders) may use spermatophores and spermatheca

http://www.amphibiainfo.com/gallery/caudata/salamandridae/triturus/cristatus/

triturus_cristatus_mazzei.jpg

Cleavage and the blastula:

As fertilized egg cells divide this is called cleavage.

What happens to cell size initially?

Hollow sphere is called the blast-ulaand it contains a hollow space… the blastocoel.

Excessive yolk impedes cell division… such that a blastoderm develops on an otherwise undivided yolk.

What taxonomic group(s) would utilize this mode?

Early Development

Let’s review what we can infer since we know this is “Chordate” development…

What type of cleavage pattern?

What does the 1st opening become?

How many germ layers do we have?

Early Development

Extra-embryonic membranes include:

Yolk sac, amnion, chorion and allantois

http://embryology.med.unsw.edu.au/Movies/larsen/fetalmembranes.jpg

Extra-embryonic membranes

Yolk sac is a highly vascular membrane that surrounds the yolk.

Empties into the midgut

Can secrete enzymes to digest yolk

Can serve as respiratory organ in viviparous amphibians/fish

Can absorb nutrients from mother… functions as a simple yolk sac placenta or a “pseudoplacenta”

http://www.minkhollow.ca/HatchingProgram/Resources/Pictures/embryo-1-wk.JPG

What does a yolk sac accomplish? How?

Reptiles and mammals develop inside 2 sacs… Amnion and Chorion:

Amnion surrounds the embryo

Chorion surrounds the amnion and the yolk sac

Important feature that allows eggs to be laid on land (with less dependence on water)

Amniotic fluid surrounds the embryo and is contained by the amnion

Where does this water come from?

Allantois is an evagination of the cloaca

Communicates with the inner surface of the chorion forming the chorioallantoic membrane

Reptiles and monotremes aids in transferring gases (respiration)

In most mammals serves as a membrane of the placenta… transferring nutrients and wastes.

Base of this sac becomes the urinary bladder

http://www.youtube.com/watch?v=lXN_sDnd1ng

Figure 2.1 Selected developmental states of a turtle embryo showing the formation of the extra-embryonic membranes. Clockwise from upper left: shelled egg showing early embryogenesis; embryonic disc during neural tube formation and initiation of amniotic folds; embryo during early morphogenesis as somites form showing rearward growth of the amniotic fold as it envelopes the embryo; embryo in early organogenesis with initial outgrowth of the allantois; near-term embryo encased in amnion showing the yolk-sac attachment protruding ventrally.Adapted from Agassiz, 1857.

Figure 2.2 Paedogenesis and isogenesis in Ambystoma talpoideum. The life history of A. talpoideum demonstrates the complexities of trait development patterns. The ancestral condition for this species is metamorphosis into a terrestrial salamander in less than one year. Under certain environmental conditions, paedogenesis occurs when metamorphosis is delayed and results in sexual maturation of the individual with retention of larval traits (i.e., the larval morphology) producing paedotypic individuals. Isogenesis occurs when similar early larvae follow different developmental trajectories but ultimately produce similar adults. The adults are termed isotypic individuals. Figure courtesy of S. M. Reilly.

Development & GrowthHeterochrony

Figure 2.3 The concept of heterochrony can be applied to a wide variety of traits. The New World microhylid, Dermatonotus muelleri, has a tiny head relative to its body and, because other New World microhylids are similar, truncation of head development likely occurred in an ancestor to the clade of New World microhylids. (Luis Gasparini)

Development & GrowthHeterochrony

Figure 2.4 Body forms of some amphibian larvae arranged by habitat type.

Figure 2.6 Selected larval stages of a typical anuran. Stage terminology from Gosner (1960).

Free-living Embryos

Figure 2.5 Reptiles are tightly coiled inside of eggs prior to hatching. Embryos of Plestiodon fasciatus inside of eggs. Developmental stage 39 (upper); stage 40 (lower). (James R. Stewart)

Figure 2.7 Photograph of the egg of a Geochelone sulcata just beginning to hatch. The arrow points to the emerging egg tooth as it begins to slice through the leathery shell. (Tim Colston)

Figure 2.8 General growth pattern trends for amphibians and reptiles. Top: comparison of indeterminant and determinant growth. When growth is relatively indeterminant, constant growth rate as a juvenile is followed by slower, but continuous growth once sexual maturity is reached. When growth is determinant or asymptotic, a sigmoid pattern during juvenile stages is followed by slower growth after sexual maturity and finally curtailment of growth. Bottom graph: hypothetical growth for an ectotherm in a seasonal environment follows a pattern of rapid growth during equable seasons and greatly reduced or no growth during adverse seasons.

Figure 2.9 Amphibian skin. Cross section through the ventral skin of a marine toad Rhinella [Bufo] marina. Abbreviations: Mg, mucus gland; Pg, poison or granular gland; Sc, stratum compactum; Sg, stratum germinativum; Ss, stratum spongiosum.

Integument

Chapter 02 FIG 34

Figure 2.10 The tropical toad Rhaebo guttatus has enlarged paratoid glands behind the head as well as many other glands over the body surface. Secretions from the paratoid glands are toxic. (Janalee P. Caldwell)

Integument

• Details from Chpt. 2 (skin)• Chromatophores

– Xanthophore– Iridophore– Melanophore

Figure 2.14 The arrangement of chromatophores in amphibian skin, called the dermal chromatophore unit. The unit consists of xanthophores, which give yellow, orange, or red coloration; the iridophores, which reflect light and cause bright colors; and the basal melanophores, which have dendritic processes that extend between the xanthophores and the iridophores.

Figure 2.15 Frog skin contains a variety of pigments that often result in bizarre intricate patterns, as in this Amazonian Ceratophrys cornuta (Janalee P. Caldwell).

Integument

Figure 2.11 Femoral pores of the male of the lizard Sceloporus undulatus are located along the posterior edge of the underside of the thighs. They appear as lines of black spots. (Laurie Vitt)

Integument

Figure 2.12 Diagram of the sequential cellular changes during a single shedding cycle in squamate epidermis. Adapted from Landmann (1986).

Reptile skin is different in that:

* Thickness/layers

* Structure/texture

* Types of keratin

* Growth patterns

Integument

Figure 2.13 Anolis punctatus shedding its skin. Note that the old skin separates in several places from the new skin (Laurie Vitt).

Integument

Figure 2.16 Cranial skeletons of representatives of the three clades of extant amphibians. Dorsal, lateral, and ventral views (left to right) of the caecilian Epicrionops petersi, the salamander Salamandra salamandra, and the frog Gastrotheca walkeri.

Skeleton

Figure 2.17 The hyobranchial skeleton of a typical vertebrate, the salamander Cryptobranchus (dorsal view), and the caecilian Ichythyophis (ventral view).Reproduced, with permission, from Duellman and Trueb, 1986.

Skeleton

Figure 2.23 Postcranial skeletons (ventral view) of a gray treefrog (Hyla versicolor) and a hellbender (Cryptobranchus alleganiensis). Adapted from Cope (1898).

Skeleton

Figure 2.18 Cranial skeletons of representatives of the three clades of living reptiles. Dorsal, lateral, and ventral views (left to right) of the turtle Pseudemydura umbrina, the crocodylian Alligator sinensis, and the lizard Ctenosaura pectinata. Adapted from Gaffney (1979), Iordansky (1973), and Oelrich (1956), respectively.

Skeleton

Figure 2.19 Reptile teeth can sit on top of the jaw (acrodont), embedded in the jaw (thecodont), or on the side of the jaw (pleurodont). Tooth location is one of the many important taxonomic characters used to separate major taxa. Adapted from Kardong, 2006.

Skeleton

• Amniota• Mammalia• Reptilia/Aves

What are Reptilia features?

• Amniote skulls– Stem reptiles lacked

temporal fossae (An-apsid skull)

– Modern reptiles have two fossae (di-apsid skull)

– Ancestors to mammals have a single fossae (syn-apsid skulls)

Skeleton

Figure 2.20 Evolution of skull openings (fenestre) in modern reptiles. Variation exists in the openings (fenestre) behind the orbit and the position of the postorbital (Po) and squamosal (Sq) bones that form the arch from the orbit to the back of the skull. The anapsid (closed) condition is thought to be ancestral. Lizards (including snakes) clearly have modified diapsid (two fenestre) skulls. Turtles, which have been placed historically in the Parareptilia based on the absence of a second fenestra, more likely have a highly modified diapsid skull in which both fenestre have closed. Other bones shown include the quadratojugal and the jugal. Adapted from Kardong, 2006.

Skeleton

Figure 2.21 Evolution of jaw structure and function in squamates. Clockwise from upper left, ancestors of squamates had rigid jaws and skulls such that the skull lifted as a unit when opening the mouth (metakinesis). The "hanging jaw" of squamates (streptostyly) allowed rotation of the lower jaws on the quadrate bone. Scleroglossans have kinetic joints in the skull located behind the eyes (mesokinesis), and snakes have an extra joint located anterior to the eyes (prokinesis). Increased flexibility of the skull allows greater prey-handling ability. The red circle with a cross indicates focal point of rotation.

Skeleton

Figure 2.24 Partial skeleton of a crocodylian showing the variation in structure of vertebrae. The vertebral column is divided into five regions. Note the location of the gastralia (floating "ribs"). Redrawn from Kardong, 2006.

Skeleton

Figure 2.25 Skeleton of a modern turtle showing fusion of vertebrae to the shell. Adapted from Bellairs, 1969.

Skeleton

Figure 2.26 Graphic showing primitive lateral-sequence gait of a salamander. The center of mass (red circle) remains within the triangle of support (dashed line), and three of the four limbs meet the ground at the same time. During a trot gait (not shown), diagonal limbs meet the ground at the same time and the center of gravity falls on a line connecting those limbs. Often, the tail is used to stabilize the trot gait, which forms a triangle of support. Redrawn from Kardong, 2006.

Skeleton

Figure 2.28 Above: A diagrammatic lateral view of the brain and spinal cord of a frog. Below: Structure of the frog brain.

Nervous system

Figure 2.29 Infra-red heat-sensing pits are located below and posterior to the nares in pit-vipers. These sense organs detect movement across a thermal landscape based on relative temperature. The snake in the photograph is Bothriopsis bilineata from the Amazon rain forest. (Laurie Vitt)

Sensory adaptations

Figure 2.30 Lateral view of the anatomy of a lizard's ear. The otic capsule consists mainly of the opisthotic and prootic. Adapted from Baird, 1970.

Sensory adaptations

Figure 2.31 Cross section of the anatomy of a snake's eye. Adapted from Underwood, 1970.

Sensory adaptations

Figure 2.32 Lepidosaurians can have gustatory organs (taste buds), nasal olfactory systems (sense of smell), and/or vomeronasal systems (chemosensory using the tongue to transport chemicals). Adapted from Schwenk, 1995.

Sensory adaptations

Figure 2.33 Lateral view of the circulatory system of a frog.

Circulatory system

Figure 2.34 Heart anatomy of a turtle and a varanid lizard; diagrammatic ventral views of frontal sections. The arrows indicate only the general pathway of blood flow through the ventricle into the aortic arches. Adapted from Burggren, 1987.

Circulatory system

Figure 2.35 A variety of glands occur in the oral region of the head of reptiles, although not all reptiles have all glands shown. Premaxillary, nasal, and palatine glands secrete mucous to lubricate the mouth. Lacrimal and Harderian glands secrete fluids that wet the vomeronasal region and the eyes. The Duvernoy's gland occurs in venomous snakes and produces venom.

Digestive system

Figure 2.36 Visceral anatomy of a generalized male snake; a ventral view.

Digestive system

Figure 2.39 Schematic lizard showing the location of some digestive and endocrine glands.

Digestive system

Figure 2.37 Internal morphology of generalized reptilian lungs; schematic cross sections of a single-chambered lung (top), a transitional lung (middle), and a multichambered lung (lower). The central chamber of a single-chambered lung is not divided by a major septum, although small niches are commonly present along the wall. The transitional lung has a central lumen partially divided by large septum. The multichambered lung is partitioned into numerous chambers of various sizes; all chambers communicate with the intrapulmonary bronchus via an airway. Adapted from Perry, 1983.

Respiratory system

Figure 2.38 Ventral view of the reproductive tracts of a female (left side) and male (right side) salamander.

Reproductive system

Monophyletic clade. Synapomorphies include… –Smooth skin with mucous and granular glands What...

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