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The Biology of Amphibians @ Agnes Scott College Mark Mandica Executive Director The Amphibian Foundation [email protected] 678 379 TOAD (8623) 2.1: Introduction to Caecilians Microcaecilia dermatophaga Synapomorphies of Lissamphibia There are more than 20 synapomorphies (shared characters) uniting the group Lissamphibia Synapomorphies of Lissamphibia Integumen is Glandular Synapomorphies of Lissamphibia Glandular Skin, with 2 main types of glands. Mucous Glands Aid in cutaneous respiration, reproduction, thermoregulation and defense. Granular Glands Secrete toxic and/or noxious compounds and aid in defense Synapomorphies of Lissamphibia Pedicellate Teeth crown (dentine, with enamel covering) gum line suture (fibrous connective tissue, where tooth can break off) basal element (dentine) Synapomorphies of Lissamphibia Sacral Vertebrae Sacral Vertebrae Connects pelvic girdle to The spine. Amphibians have no more than one sacral vertebrae (caecilians have none) Synapomorphies of Lissamphibia Amphicoelus Vertebrae Synapomorphies of Lissamphibia Opercular apparatus Unique to amphibians and Operculum part of the sound conducting mechanism Synapomorphies of Lissamphibia Fat Bodies Surrounding Gonads Fat Bodies Insulate gonads Evolution of Amphibians † † † † Actinopterygian Coelacanth, Tetrapodomorpha †Amniota *Gerobatrachus (Ray-fin Fishes) Lungfish (stem-tetrapods) (Reptiles, Mammals)Lepospondyls † (’frogomander’) Eocaecilia GymnophionaKaraurus Caudata Triadobatrachus Anura (including Apoda Urodela Prosalirus †) Salientia Batrachia Lissamphibia *Gerobatrachus may be the sister taxon Temnospondyls † to Batrachia Tetrapods Osteichthyes Sarcopterygian (Bony Fishes) (Lobe-fin Fishes) Amphibian Reign Time Period Devonian Carboniferus Permian Triassic Jurassic Cretaceous Millions of Years Ago (420 MYA) (350 MYA) (300 MYA) (250 MYA) (200 MYA) (150-65 MYA) Present Day resembles Plate Tectonics Gondwana + Laurussia Pangea Pangea Pangea begins to break Pangea breaks present day The Biology of Amphibians amphibbio.amphibianfoundation.org CLassification of Order: Gymnophiona † Eocaecilia Rhinatrematidae Ichthyophiidae Scolecomorphidae Chikilidae Herpelidae Caeciliidae Typhlonectidae Indotyphiidae Dermophiidae Siphonopidae † † † † Actinopterygian Coelacanth, Tetrapodomorpha †Amniota *Gerobatrachus (Ray-fin Fishes) Lungfish (stem-tetrapods) (Reptiles, Mammals)Lepospondyls † (’frogomander’) Eocaecilia GymnophionaKaraurus Caudata Triadobatrachus Gymnophiona Anura (including Apoda Urodela Prosalirus †) Salientia Apoda Batrachia Lissamphibia *Gerobatrachus may be the sister taxon Temnospondyls † to Batrachia Tetrapods Osteichthyes Sarcopterygian (Bony Fishes) (Lobe-fin Fishes) Lissamphibia The Biology of Amphibians amphibbio.amphibianfoundation.org Order: Gymnophiona | Family: Ichthyophiidae cloaca tail tentacular organ annuli Ichthyophis kohtaoensis Order: Gymnophiona The ‘naked snakes’ Apoda (no feet) includes all amphibians more closely related to caecilians than to frogs or salamanders, including Eocaecilia micropodia † (which had tentacular fossa and an os basale), as well as Rubricacaecilia monbaroni † and Chinlestegophis † Fossorial (though several species are aquatic) Pan-tropical distribution (excluding Madagascar) Order: Gymnophiona Order: Gymnophiona Integumen Dermal Scales - Present in some species of caecilian, but no other Lissamphibia Dermal Scales - Found in pouches below Annular Groove Poison - Not all caecilians have been tested, but based on the samples of Siphonops and Typhlonectes, at least most caecilians are toxic to predators* *see Jared, 2018 - in the ‘additional readings’ folder for a great description of the use of toxin in Siphonops Order: Gymnophiona Coral Snake vs Caecilian Order: Gymnophiona Integumen Lateral Line System - Caecilians posses a lateral line system - a sensory system located in the epidermis of the head and body. They consist of two types of receptors. A. Ampullary Organs - Electroreceptors (the solid structures in the figure on right) B. Neuromasts - Mechanoreceptors (the open structures in the figure on right) Ichthyophis sp. Order: Gymnophiona Anatomy Annular Grooves - Primary, Secondary and Tertiary annuli correspond with vertebrae Order: Gymnophiona | Family: Siphonopidae Primary annuli Siphonops sp. Order: Gymnophiona | Family: Dermophiidae Tertiary annuli Secondary annuli Primary annuli Gymnopis multiplicata Order: Gymnophiona Anatomy Caecilians lack limbs and girdles Order: Gymnophiona Anatomy Caecilians lack limbs and girdles Order: Gymnophiona Anatomy Tail - Cloaca at end of the body. Caecilians either have no tail (synapomorphy) or short tail (pleisiomorphy) Order: Gymnophiona Anatomy Tail - Cloaca at end of the body. Caecilians either have no tail (synapomorphy) or short tail (pleisiomorphy) Order: Gymnophiona Small vestigial eyes Can only detect light and dark Are covered with skin or bone The Caecilian Skull Order: Gymnophiona The Caecilian Skull High ossification and reduction in number of bones (fused) to increase strength of skull, which is basically used as a battering ram through the dirt. Caecilian skulls are adapted for burrowing. Order: Gymnophiona The Caecilian Skull Two main skull conditions in caecilians, the stegokrotaphic condition in which the bones of the skull are completely fused, and the zygokrotaphic condition, which allows for kinetic movement, in a ‘zone of weakness’ between the parietal and squamosal bones in the temporal region. Order: Gymnophiona The Caecilian Skull The Os basale is unique to caecilians, and is a shared trait by extant caecilians (Gymnophiona) as well as all of Apoda, including Eocaecilia †. It is the formation of the fused parasphenoid, basioccipitals, exoccipitals, and otic capsules. Caecilians also posses two rows of maxillary pedicellate teeth on the upper jaw. This feature, with the fused condition of the skull makes them easily recognizable. Order: Gymnophiona The Caecilian Skull The caecilian skull is adapted to exert maximum force on the soil in which it burrows (with its face) Caecilians also have tremendous bite force which is delivered through a series of muscles using the retroarticular process of the jaw as a lever to increase force without adding lateral girth (which would impede burrowing) Order: Gymnophiona The Caecilian Skull Os basale tentacular fossa maxillary retroarticular process articulation pseudo dentary The Caecilian Skull Jaw adduction musculature Longis capitus Interhyoideus posterior major temporalis Temporalis: adducts the upper and lower jaw; Longis capitus connects the vertebrae with the base of the skull, when contracted, the skull is rotated down onto the jaw; Interhyoideus posterior major originates in the fascia of the ventral and lateral body wall and inserts on the retroarticular process. When contracted it pulls on the process like a lever The Caecilian Skull Jaw adduction musculature Temporalis: adducts the upper and lower jaw; Longis capitus connects the vertebrae with the base of the skull, when contracted, the skull is rotated down onto the jaw; Interhyoideus posterior major originates in the fascia of the ventral and lateral body wall and inserts on the retroarticular process. When contracted it pulls on the process like a lever The Caecilian Skull Jaw Mental Symphisis V VV Caecilian teeth fit like this The mental symphisis firmly fused at the joining of Articulation Retroarticular the left and right lower jaw bones Process The Caecilian Skull Tentacular organ The tentacular organ. The only example of a tentacle in all of vertebrates. This organ is a chemosensory receptor. The Caecilian Skull Tentacular organ tentacular fossa The Caecilian Skull Terminal mouth Sub-terminal mouth (pleisiomorphic) (apomorphic) Order: Gymnophiona Reproduction Order: Gymnophiona Internal fertilization (Quite a novelty in the amphibian world) Reproduction is internal via the male copulatory organ — the phallodeum phallodeum Internal fertilization in caecilians Order: Gymnophiona Internal fertilization Order: Gymnophiona Caecilian Reproduction Viviparous bringing forth live young that have developed inside the body of the parent. Oviparous producing young by means of eggs that are hatched after they have been laid by the parent. Order: Gymnophiona Caecilian Embryonic Development Stages in the development of the caecilian Ichthyophis glutinosus. A. Neurulation. B. Early organogenesis. C. Late development. Branchial arches are designated by roman numerals. Caecilian Fetal Development Oviparous caecilians can lay their eggs in or near water, which hatch into free- swimming larvae, as is common with most amphibians. These caecilian larvae have large, leaf-like gills which are Oviparous Caecilians resorbed at metamorphosis. Oviparous Oviparous caecilians can also lay their eggs terrestrially, which are direct developing, skipping the free- swimming larval stage and hatch into miniature versions of the adult form. Chikila sp. Viviparous Typhlonectes natans Herpele squalostoma Viviparous caecilians can be aquatic or terrestrial. Viviparity is the most common condition and is considered apomorphic among the more derived caecilians. Typhlonectes natans Viviparous Although most caecilians are viviparous, only certain groups exhibit a novel form of nutrient provisioning for their offspring called maternal dermophagy. Schistometopum thomense Viviparous With maternal dermophagy, the mother produces a nutritious outer layer of skin for her young to feed on by scraping with their ‘paint scraper’ like teeth. This provides nourishment which allows the young caecilians to grow and mature rapidly The mother can replace this skin layer in a couple of days. Dermophagy occurs externally, with the outer layer of skin (as pictured) or internally with offspring feeding on the uterine lining. Viviparous Fetal Teeth Parental Care.
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  • Early Tetrapod Relationships Revisited

    Early Tetrapod Relationships Revisited

    Biol. Rev. (2003), 78, pp. 251–345. f Cambridge Philosophical Society 251 DOI: 10.1017/S1464793102006103 Printed in the United Kingdom Early tetrapod relationships revisited MARCELLO RUTA1*, MICHAEL I. COATES1 and DONALD L. J. QUICKE2 1 The Department of Organismal Biology and Anatomy, The University of Chicago, 1027 East 57th Street, Chicago, IL 60637-1508, USA ([email protected]; [email protected]) 2 Department of Biology, Imperial College at Silwood Park, Ascot, Berkshire SL57PY, UK and Department of Entomology, The Natural History Museum, Cromwell Road, London SW75BD, UK ([email protected]) (Received 29 November 2001; revised 28 August 2002; accepted 2 September 2002) ABSTRACT In an attempt to investigate differences between the most widely discussed hypotheses of early tetrapod relation- ships, we assembled a new data matrix including 90 taxa coded for 319 cranial and postcranial characters. We have incorporated, where possible, original observations of numerous taxa spread throughout the major tetrapod clades. A stem-based (total-group) definition of Tetrapoda is preferred over apomorphy- and node-based (crown-group) definitions. This definition is operational, since it is based on a formal character analysis. A PAUP* search using a recently implemented version of the parsimony ratchet method yields 64 shortest trees. Differ- ences between these trees concern: (1) the internal relationships of aı¨stopods, the three selected species of which form a trichotomy; (2) the internal relationships of embolomeres, with Archeria