Z250 - Lec28 Outline- Arthropoda III (2017)

Zoology 250 (2017)

ARTHROPODA (III): General features (cont.)

(Crustacea study images, other arthropod study images;
click on tree to see full cladogram)

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7) Arthropods are divided into 4 subphyla based on: a) tagmatization, b) anterior limb form and function, c) location of mouth in embryo and adult:

Trait Chelicerata Trilobitomorpha Crustacea 'Uniramia'

Number of TAGMATA

2: cephalothorax (=prosoma*),
abdomen (=opisthosoma*) 3: head, thorax,
abdomen (=pygidium*) 2: head, trunk (primitive) or
3: head, thorax, abdomen (derived) 2: head, trunk (Myriapoda) or
3: head, thorax, abdomen (Insecta)

* equivalent terms in other textbooks

ANTERIOR LIMBS (*= mouth lies just anterior to this segment in adult):

Cephalothorax (#) head (#) head (#) head (#)

Acron- Pr++ # none # none # none # none

Segment #1- De++ # (lost) # antenna # first antenna # antenna

Segment #2- Tr++ # * chelicerae + # * head leg** # second antenna # (lost)***

Segment #3 # * pedipalps/legs # head leg** # * mandible # * mandible

Segment #4 # oviger/legs # head leg** # first maxilla # maxilla

Segment #5 # legs      thoracic leg** # second maxilla # labium/maxilla

Segment #6 # legs      thoracic leg      thoracic leg      thoracic leg

Segment #7 # legs      thoracic leg      thoracic leg      thoracic leg

Segment #8      abdomen limbs
     (if present)      thoracic leg      thoracic leg      thoracic leg

MOUTH LOCATION (*= location of mouth; A= acron; 1,2, etc.= segment number):

in embryo A*2 1*2 1*2 1*2

in adult: A*2+ or 2*3 1*2 2*3 1*3

+ mouth site in
Pycnogonida only ** thoracic-like *** transitory in Symphyla

++ segment homology based on brain regions: Pr- Protocerebrum, De- Deuterocerebrum, Tr- Tritocerebrum (Harzsch 2004. Evol. and Devel. 6:303)

8) Increasing evidence suggests the Uniramia may be an artificial group that should be split into two separate subphyla: Myriapoda (millipedes and centipedes) and Hexapoda (insects)

Trait	Chelicerata	Trilobitomorpha	Crustacea	'Uniramia'

Number of TAGMATA
	2: cephalothorax (=prosoma), abdomen (=opisthosoma)	3: head, thorax, abdomen (=pygidium*)	2: head, trunk (primitive) or 3: head, thorax, abdomen (derived)	2: head, trunk (Myriapoda) or 3: head, thorax, abdomen (Insecta)
* equivalent terms in other textbooks

ANTERIOR LIMBS (*= mouth lies just anterior to this segment in adult):
	Cephalothorax (#)	head (#)	head (#)	head (#)
Acron- Pr++	# none	# none	# none	# none
Segment #1- De++	# (lost)	# antenna	# first antenna	# antenna
Segment #2- Tr++	# * chelicerae +	# * head leg**	# second antenna	# (lost)***
Segment #3	# * pedipalps/legs	# head leg**	# * mandible	# * mandible
Segment #4	# oviger/legs	# head leg**	# first maxilla	# maxilla
Segment #5	# legs	thoracic leg**	# second maxilla	# labium/maxilla
Segment #6	# legs	thoracic leg	thoracic leg	thoracic leg
Segment #7	# legs	thoracic leg	thoracic leg	thoracic leg
Segment #8	abdomen limbs (if present)	thoracic leg	thoracic leg	thoracic leg

MOUTH LOCATION (*= location of mouth; A= acron; 1,2, etc.= segment number):
in embryo	A*2	1*2	1*2	1*2
in adult:	A2+ or 23	1*2	2*3	1*3
	+ mouth site in Pycnogonida only	** thoracic-like		*** transitory in Symphyla

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