Turtles VERTEBRATE ZOOLOGY (VZ Lecture16 – Fall 2012 Althoff - reference PJH Chapter 12)

Turtles essentially lack diversity in life history strategies compared to salamanders… a) ____ lay eggs (vs. some eggs, some live livebirth, etc.) b) ____ exhibit parental care of hatchling (vs. some that stay with eggs, young) c) generally low reproductive productivity (later maturity, few young per effort for turtle) Beyond Amphibians….or not???

Thought to have emerged in the Triassic (~_____ MYA) Little change suspected in design/function from early versions Shell morphology reflects the ecology of this group: Large terrestrial tortoises: high domed shells & elephant-like feet Small tortoises: front legs flattened for burrowing Pancake tortoise: flat shell, agile Box turtles: moderately domed, flexible plastron Etc. See Fig. 12-1, pg305 PJH Not much change…terrestrial & aquatic forms

Class: Anapsida Order: Testudomorpha (~ 300 species) Suborders ______________ (10 families) ______________ (3 familes) Classification

Cryptodires Greek crypto = dire = Retract head into the shell by bending the neck in a _________ S shape 10 families all turtle species find in ____________ are from this suborder None found in Australia Marine turtles fall into this suborder Pelvic girdle _____ fused to carapace External adductor tendon “over” trochlear process that is part of otic capsule Suborder: Cryptodira

Pleurodires Greek pleuro = dire = neck Retract head into the shell by bending the neck ________________ 3 families Species found in South America, Africa, Madagascar, Australia All extant species are at least semi-aquatic Pelvic girdle ____ fused to carapace External adductor tendon “over” trochlear process that is separate from of otic capsule Suborder: Pleurodira

Two “twists” here for this group a) many ancestral features b) many highly specialized characters ____ shared with any other group of vertebrates Turtles have anapsid skulls….but a) ______ unique b) _____________ skeletons are unique Result  two competing hypotheses: A) origin from ______________ B) origin with ___________ reptiles Phylogenetic Relationships of Turtles

Fig. 12-3, p307 PJH Amniotes Sauropods Diapsids LepidosaursArchosaurs Squamates Turtles A B PARAREPTILES DIAPSID REPTILES

Fig. 12-4, p308 PJH Position of the EXTERNAL ADDUCTOR TENDON— __________ vs. __________ suborder differences— TROCHLER PROCESS ancestral parareptiles cryptodirans pleurodirans trochlear process trochlear process

Covered in bone Limbs inside ribs Horny beaks instead of teeth Lungs attached to carapace dorsally and ventrally Structure & Function - Highlights

Snapping turtle loggerhead sea turtle

Composed of _____________ that grows from 59 separate centers of ossification 8 ________ along the dorsal midline a) forms “neural” series b) fused to neural arches of vertebrae 8 paired costal bones, lateral to neural bones, fused to broadened ribs Ribs are EXTERNAL to the girdles (unique among vertebrates) 11 pairs of peripheral bones plus 2 unpaired bones (uchal & pygal) form margin of carapace Carapace – “foundation” A

Fig. 12-5, p309 PJH A CARAPACE “foundation”

Composed of ______________ that originate from _____________ layer. These scutes do NOT coincide with the position of the underlying bones 5 rows of central scutes 4 rows of lateral scutes border central scutes 12 marginal scutes (marginals) on each side turn under the edge of the carapace Carapace – “covering” B

Fig. 12-5, p309 PJH B CARAPACE “covering” horny covering

10 trunk vertebrae (8 in neck) Pleurodires: pelvic girdle fused to dermal carapace (i.e., bony portion) vs. Cryptodires: 2 sacral vertebrae have broadened ribs that meet ilia of the pelvis (hence, not “fused” to carapace) Carapace – “inside view” C

Fig. 12-5, p309 PJH C CARAPACE “inside view” horny covering

Primitive amniotes used movements of the rib cage to draw air into the lungs and force it out. Because ribs are fused in turtles to their rigid shells, they cannot use that method to breath Lungs attached to carapace dorsally and laterally. On the ventral side, they are attached to a sheet of ______________ connective tissue that is itself attached to the viscera. Weight of this tissue keep this area stretched downward So, turtles produce pressure changes by contracting muscles that force the viscera upward (compress), then other muscles that increase volume of the visceral cavity Respiration

Fig. 12-7, p312 PJH Transverse abdominus USED IN EXHALATION

Fig. 12-7, p312 PJH USED IN INHALATION PECTORALIS SERRATUS ABDOMINAL OBLIQUE

Bottomline, turtles have done without ribs to help with ventilation Some variations noted among turtle species: a) aquatic turtles can use hydrostatic pressure of water to help move air in and out of lungs b) many aquatic turtle species capable of absorbing 0 2 and releasing CO 2 to the water, mainly via the ___________ and____________ Soft-shelled turtles have been observed to use hyoid apparatus to move water in and out of the pharynx…resulting in most 0 2 coming in that way Australian turtle almost exclusively uses “______” respiration  pumps H 2 0 in and out Respiration…con’t

Turtles: 3-chambered heart Turtles exhibit “right-to-left intracardiac shunt” process at times: a) result is some deoxygenated blood bypasses the lungs and flows into systemic system b) “shift” occurs in heart (i.e., “intra”) rather than between major blood vessels Right-to-left intracardiac shunting is not unique to turtles…snakes, lizards, and crocodilians known to do this, too. May help match lung ventilation with pulmonary gas flow, may be helpful for those species that dive (i.e., aquatic species)…results in more effective use of O 2 in lungs. Respiration & Circulation

Some species exhibit basking behavior. The result/need  raise body temperature. Raising body temperature can result in: a) b) c) ….otherwise these processes go very slowly or halt altogether Other benefits: a) rid themselves of algae & leeches b) activate Vit D, impacting Ca deposition Basking: Temperature & Etc. Benefits

Social interactions usually facilitated by tactile, visual, and olfactory signals Many pond turtle species have distinctive stripes of color on their head, neck, forelimbs, hindlimbs, and tail. Among terrestrial turtles, tortoises known for vocalizations (grunts, moans, and bellows) during courtship. Some produce pheromones during breeding period—species and sex specific Herds of tortoises have social hierarchies, determined by aggressive behaviors, impact access to food, mates, and nesting sites Social Behavior & Courtship

All turtle species are _____________ Females use hind limbs to excavate a nest in sand or soil. _______ species typically: 4-5 eggs _______ species typically: 100+ eggs Some species lay soft eggs, some hard eggs Typically embryonic development takes days, with soft-shelled eggs usually developing ______ rapidly than hard-shelled eggs. Some lay eggs in spring, others in late summer and fall (diapause) that hatch next spring…. What would be an advantage of such a strategy? Nesting Behavior

Temperature, wetness, O 2 and CO 2 concentrations impact embryonic development For many species, sex of hatchlings is determined by temperature (also known to occur for crocodilians, tuatara, and some lizard species) Temperature usually influences size of individuals, as it relates to sex. For most species, females larger than males. Thus, under higher temp- regimes, more females are result (just opposite in other taxa). Usually a 3-4 O C difference results in these patterns Implications are critical to conservation of endangered species Environmental Effects on Egg Development

Fig , p317 PJH European pond turtle speciesNA Map Turtle Lizard Agama agama