The Biology of Amphibians @ Agnes Scott College Mark Mandica Executive Director The Amphibian Foundation mark@amphibianfoundation.org 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 Tetrapodomorpha † *Gerobatrachus † obatrachus † Gymnophiona Gymnophiona (Reptiles, Mammals) Actinopterygian Triadobatrachus † (stem-tetrapods) Lepospondyls † (’frogomander’) (’frogomander’) (Ray-fin Fishes) Coelacanth, Caudata Eocaecilia † Eocaecilia † Karaurus † Amniota Karaurus Lungfish Anura (including Apoda Apoda Urodela Urodela Prosalirus †) Salientia Batrachia Lissamphibia *Gerobatrachus may be the sister taxon to Batrachia Temnospondyls † Tetrapods Osteichthyes Sarcopterygian (Bony Fishes) (Lobe-fin Fishes) A m p h i b i a n R e i g n Devonian Carboniferus Permian Triassic Jurassic Cretaceous Time Period (420 MYA) (350 MYA) (300 MYA) (250 MYA) (200 MYA) (150-65 MYA) Present Day Millions of Years Ago resembles Plate Tectonics Gondwana + Laurussia Pangea Pangea Pangea begins to break Pangea breaks present day T h e B i o l o g y o f A m p h i b i a n s amphibbio.amphibianfoundation.org
CLassification of Order: Gymnophiona Lissamphibia Eocaecilia † Rhinatrematidae Ichthyophiidae Apoda Scolecomorphidae Gymnophiona Chikilidae Herpelidae Caeciliidae (Bony Fishes) Osteichthyes Typhlonectidae T h e B i o l o g y o f A m p h i b i a n s Actinopterygian (Lobe-fin Fishes) (Ray-fin Fishes) Sarcopterygian Indotyphiidae Coelacanth, Lungfish Tetrapods Tetrapodomorpha † (stem-tetrapods) Dermophiidae Amniota (Reptiles, Mammals) Lepospondyls † Temnospondyls † Siphonopidae *Gerobatrachus † (’frogomander’) Lissamphibia amphibbio.amphibianfoundation.org Apoda Apoda Apoda Eocaecilia † Eocaecilia † Eocaecilia † *Gerobatrachus may be the sister taxon Batrachia Urodela Gymnophiona Gymnophiona Gymnophiona Karaurus † to Batrachia Salientia Caudata Triadobatrachus † Prosalirus †) (including Anura
Order : Gymnophiona | Family : Ichthyophiidae tail cloaca 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
Anatomy Order : Gymnophiona Caecilians lack limbs and girdles
Anatomy Order : Gymnophiona 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 V V Caecilian teeth fit like this The mental symphisis Articulation firmly fused at the joining of Retroarticular the left and right lower jaw Process bones
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
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