by justin speaks

A Phylogenetic Survey of A Phylogenetic Survey of Dental Sexual Dimorphism in Dental Sexual Dimorphism in Chondrichthyan Fishes of the Chondrichthyan Fishes of the

North Carolina CoastNorth Carolina Coast

By Justin SpeaksBy Justin SpeaksFaculty Advisor: Dr. Thomas Lankford

Mating BehaviorMating Behavior

Typical for male to bite female prior Typical for male to bite female prior to and during copulation, leaving to and during copulation, leaving what are called mating scars.what are called mating scars.

Sharks and Rajiformes Sharks and Rajiformes

practice in vitro practice in vitro

fertilization.fertilization.

What is Dental Sexual What is Dental Sexual Dimorphism?Dimorphism?

A difference in tooth shape between A difference in tooth shape between males and females.males and females. Some stingrays have displayed this on a Some stingrays have displayed this on a

seasonal basisseasonal basis Sharper teeth during mating seasonsSharper teeth during mating seasons

Photo courtesy of Florida Museum of Natural History Ichthyology Department

Research QuestionsResearch Questions Do other species of ray or skate, or even sharks Do other species of ray or skate, or even sharks

with similar dentition, display this adaptation?with similar dentition, display this adaptation?

Hypothesis: Dental Sexual Dimorphism is Hypothesis: Dental Sexual Dimorphism is widespread among Chondrichthyan species who widespread among Chondrichthyan species who posses flat, crushing dentition.posses flat, crushing dentition.

Is this a new evolutionary trend or something Is this a new evolutionary trend or something that has been passed down the lineage of that has been passed down the lineage of cartilaginous fishes?cartilaginous fishes?

Will we be able to determine mating seasons Will we be able to determine mating seasons for those species that are currently unknown?for those species that are currently unknown?

The Species ListThe Species List

chim

aera

s

bullh

ead

shar

ks

carp

et s

hark

s

grou

nd s

hark

s

mac

kere

l sha

rks

cow

sha

rks

dogf

ish

shar

ks

ange

l sha

rks

saw

sha

rks

skat

es &

ray

s

Relationship Between Sharks and Rajiformes

8 Orders of Sharks (350 spp.)

12 families

62 genera

456 spp.

“batoid fishes”

How to Answer These How to Answer These QuestionsQuestions

N

EW

S

North Carolina

SouthCarolina Cape Fear

Cape Lookout

Cape Hatteras

34 o

78 o

0 25 50 mi.0 25 50 mi.

33 o

79 o 77 o 76 o

35 o

36 o

AtlanticOcean

Masonboro inlet

Jacksonville

Bottom trawl collections once a month for twelve Bottom trawl collections once a month for twelve months (May ’06-April ’07)months (May ’06-April ’07)

New MethodsNew Methods Pictures of dentition Pictures of dentition will be taken immediately will be taken immediately upon capture so as to upon capture so as to release all animals alive.release all animals alive.

We will survey sex, size, We will survey sex, size, ovulation and mating scars ovulation and mating scars (in females only)(in females only)

Photo record will be compiled and interpreted as it is Photo record will be compiled and interpreted as it is collected.collected.

Trawls will collect in Onslow Bay, from Cape Fear to Cape Lookout.

Example of Tooth Example of Tooth Photography MethodPhotography Method

Why Answer These Why Answer These Questions?Questions?

Basic information for the scientific Basic information for the scientific record.record. Which species exhibit this adaptationWhich species exhibit this adaptation Mating seasonsMating seasons EvolutionEvolution

Information for Fisheries BiologistsInformation for Fisheries Biologists Reduce by-catch during Reduce by-catch during

mating seasonsmating seasons

ReferencesReferences

Kajiura, Stephen M.; Sebastian, Agustin P.; Tricas, Kajiura, Stephen M.; Sebastian, Agustin P.; Tricas, Timothy C. Timothy C. Dermal Bite Wounds as Indicators of Dermal Bite Wounds as Indicators of Reproductive Seasonality and Behavior in the Reproductive Seasonality and Behavior in the Atlantic Stingray, Atlantic Stingray, Dasyatis sabinaDasyatis sabina. . Environmental Biology of Fishes: 2000; vol. 58, Environmental Biology of Fishes: 2000; vol. 58, pp. 23-31pp. 23-31

Kajiura, Stephen M.; Tricas, Timothy C. Kajiura, Stephen M.; Tricas, Timothy C. Seasonal Seasonal Dynamics of Dental SexualDynamics of Dental Sexual Dimorphism in the Dimorphism in the Atlantic Stingray, Atlantic Stingray, Dasyatis sabinaDasyatis sabina.. Journal of Journal of Experimental Biology: June 1996; vol 199, pp. Experimental Biology: June 1996; vol 199, pp. 2297-23062297-2306