The Biology of Amphibians @ Agnes Scott College Mark Mandica - - PowerPoint PPT Presentation

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The Biology of Amphibians @ Agnes Scott College Mark Mandica - - PowerPoint PPT Presentation

May 05, 2023 472 likes •1.04k views

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

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The Biology of Amphibians

@ Agnes Scott College

Mark Mandica Executive Director The Amphibian Foundation mark@amphibianfoundation.org 678 379 TOAD (8623)

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Microcaecilia dermatophaga

2.1: Introduction to Caecilians

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Synapomorphies of Lissamphibia

There are more than 20 synapomorphies (shared characters) uniting the group Lissamphibia

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Synapomorphies

  • f Lissamphibia

Integumen is Glandular

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Synapomorphies

  • f 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

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Synapomorphies of Lissamphibia Pedicellate Teeth

gum line crown (dentine, with enamel covering) basal element (dentine) suture (fibrous connective tissue, where tooth can break off)

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Synapomorphies of Lissamphibia Sacral Vertebrae

Sacral Vertebrae Connects pelvic girdle to The spine. Amphibians have no more than one sacral vertebrae (caecilians have none)

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Synapomorphies of Lissamphibia Amphicoelus Vertebrae

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Synapomorphies of Lissamphibia Operculum

Opercular apparatus Unique to amphibians and part of the sound conducting mechanism

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Synapomorphies of Lissamphibia Fat Bodies Surrounding Gonads

Fat Bodies Insulate gonads

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SLIDE 11 Osteichthyes (Bony Fishes) Actinopterygian (Ray-fin Fishes) Sarcopterygian (Lobe-fin Fishes) Coelacanth, Lungfish Tetrapodomorpha † (stem-tetrapods) Tetrapods Lepospondyls † Temnospondyls † Amniota (Reptiles, Mammals) *Gerobatrachus † (’frogomander’) Lissamphibia Eocaecilia †

Gymnophiona

Apoda Batrachia Urodela Karaurus † Salientia

Caudata

Triadobatrachus †

Anura

(including Prosalirus †)

Devonian (420 MYA) Carboniferus (350 MYA) Permian (300 MYA) Triassic (250 MYA) Jurassic (200 MYA) Cretaceous (150-65 MYA)

Gondwana + Laurussia Pangea Pangea Pangea begins to break Pangea breaks resembles present day *Gerobatrachus may be the sister taxon to Batrachia

Present Day

Time Period Millions of Years Ago Plate Tectonics

A m p h i b i a n R e i g n

Evolution of Amphibians

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

  • batrachus †
(’frogomander’) Eocaecilia †

Gymnophiona

Apoda Urodela Karaurus
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SLIDE 12 Osteichthyes (Bony Fishes) Actinopterygian (Ray-fin Fishes) Sarcopterygian (Lobe-fin Fishes) Coelacanth, Lungfish Tetrapodomorpha † (stem-tetrapods) Tetrapods Lepospondyls † Temnospondyls † Amniota (Reptiles, Mammals) *Gerobatrachus † (’frogomander’) Lissamphibia Eocaecilia † Gymnophiona Apoda Batrachia Urodela Karaurus † Salientia Caudata Triadobatrachus † Anura (including Prosalirus †) *Gerobatrachus may be the sister taxon to Batrachia Eocaecilia † Gymnophiona Apoda Eocaecilia † Gymnophiona Apoda

Eocaecilia † Rhinatrematidae Ichthyophiidae Scolecomorphidae Chikilidae Herpelidae Caeciliidae Typhlonectidae Indotyphiidae Dermophiidae Siphonopidae

Gymnophiona

CLassification of Order: Gymnophiona

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

Apoda Lissamphibia

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Order: Gymnophiona | Family: Ichthyophiidae Ichthyophis kohtaoensis

tentacular organ annuli cloaca tail

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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)

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Order: Gymnophiona

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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

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Order: Gymnophiona Coral Snake vs Caecilian

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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.

  • B. Neuromasts - Mechanoreceptors (the
  • pen structures in the figure on right)
  • A. Ampullary Organs - Electroreceptors

(the solid structures in the figure on right)

Ichthyophis sp.

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Order: Gymnophiona

Anatomy

Annular Grooves - Primary, Secondary and Tertiary annuli correspond with vertebrae

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Order: Gymnophiona | Family: Siphonopidae Siphonops sp. Primary annuli

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Order: Gymnophiona | Family: Dermophiidae Gymnopis multiplicata Primary annuli Secondary annuli Tertiary annuli

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Order: Gymnophiona

Anatomy

Caecilians lack limbs and girdles

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Order: Gymnophiona

Anatomy

Caecilians lack limbs and girdles

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Order: Gymnophiona

Anatomy

Tail - Cloaca at end of the body. Caecilians either have no tail (synapomorphy) or short tail (pleisiomorphy)

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Order: Gymnophiona

Anatomy

Tail - Cloaca at end of the body. Caecilians either have no tail (synapomorphy) or short tail (pleisiomorphy)

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Order: Gymnophiona

Small vestigial eyes

Can only detect light and dark Are covered with skin or bone

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The Caecilian Skull

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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.

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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.

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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.

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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

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Order: Gymnophiona

The Caecilian Skull

retroarticular process articulation pseudo dentary maxillary tentacular fossa Os basale

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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

temporalis Interhyoideus posterior major Longis capitus

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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

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The Caecilian Skull

Jaw

The mental symphisis firmly fused at the joining of the left and right lower jaw bones

Mental Symphisis Articulation Retroarticular Process

V V V

Caecilian teeth fit like this

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Tentacular organ

The tentacular organ. The

  • nly example of a tentacle in

all of vertebrates. This organ is a chemosensory receptor.

The Caecilian Skull

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The Caecilian Skull

Tentacular organ

tentacular fossa

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The Caecilian Skull

Terminal mouth (pleisiomorphic) Sub-terminal mouth (apomorphic)

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Order: Gymnophiona

Reproduction

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Order: Gymnophiona

Internal fertilization

(Quite a novelty in the amphibian world) Reproduction is internal via the male copulatory organ — the phallodeum

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Internal fertilization in caecilians

phallodeum

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Order: Gymnophiona

Internal fertilization

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Order: Gymnophiona

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.

Caecilian Reproduction

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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.

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Caecilian Fetal Development

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Oviparous Caecilians

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 resorbed at metamorphosis.

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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.

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Viviparous

Viviparous caecilians can be aquatic or terrestrial. Viviparity is the most common condition and is considered apomorphic among the more derived caecilians.

Typhlonectes natans Herpele squalostoma

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Typhlonectes natans

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Viviparous

Although most caecilians are viviparous,

  • nly certain groups exhibit a novel form of nutrient

provisioning for their offspring called maternal dermophagy.

Schistometopum thomense

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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

  • f days. Dermophagy occurs externally, with the
  • uter layer of skin (as pictured) or internally with
  • ffspring feeding on the uterine lining.
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Viviparous

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Fetal Teeth

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Parental Care