Mammal Research Institute (MRI), Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa

Timing is everything: Seasonal reproduction in the spiny mouse,

Acomys spinosissimusKatarina Medger

Supervisors: Prof. N. C. Bennett & Prof. C. T. Chimimba

Bronson 1985

Introduction

Distribution south of the equator

Habits: nocturnal, rocky habitats solitary, groups and family parties

Reproduction: seasonal as well as aseasonal breeding Acomys species indications for seasonality in A. spinosissimus (Pienaar et al. 1980, South Africa; Smithers 1971, Botswana)

(reviewed in Skinner & Chimimba 2005)

Spiny mouse – Acomys spinosissimus

Does Acomys spinosissimus reproduce

seasonally or aseasonally?

Does A. spinosissimus show reproductive

photoresponsiveness?

Objectives

1. Seasonality

Trapping10♀ & 10♂ monthly

1 year

Dissection &

Blood samples

Endocrinology centrifuge bloodanalyzing plasma

forhormones

Histology ♀ reprod. organstestes weighed,length & width

Skull & DNA sequencing

heart, liver,

kidney

Materials & Methods

2. Photoperiod

14 ♂

8L:16D

8L:16D

7 ♂

16L:8D

40 days

30 days 30 days

Materials & Methods

Climate data

Mean monthly temperature and monthly rainfall (August 2007 - March 2008)

0

5

10

15

20

25

Sep

tem

ber

Oct

ober

Nov

embe

r

Dec

embe

r

Janu

ary

Feb

ruar

y

Mar

ch

Apr

il

May

June

July

Aug

ust

2007 2007 2007 2007 2008 2008 2008 2008 2008 2008 2008 2008

Month

Te

mp

era

ture

in °

C

0

20

40

60

80

100

120

140

160

Ra

infa

ll in

mm

monthly rainfall

mean monthly temp

Goro Game Reserve – Soutpansberg – 22°S

0,00

50,00

100,00

150,00

200,00

250,00

300,00

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Months

Te

sti

cu

lar

vo

lum

e (

mm

³)

0

2

4

6

8

10

12

14

Co

rre

cte

d t

es

tic

ula

r m

as

s (

mg

/g)

Testicular volume Testicular mass

Testes volume and mass

Mean ± SD; p<0.001 (Generalized linear model)

p<0.001 (Generalized linear model)

Testosterone

Results

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Months

0

200

400

600

800

1000

1200

1400

1600

1800

Pla

sm

a t

es

tos

tero

ne

co

nc

en

tra

tio

n (

ng

/dL

)

Median 25%-75% Non-Outlier Range

Results

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Months

Ova

rian

vol

ume

(mm

³)

Ovarian volume

Mean ± SD; p<0.001 (ANOVA)

p<0.001 (Generalized linear model)

ProgesteroneJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Months

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

Pla

sm

a p

rog

este

ron

e c

on

cen

trati

on

(ng

/mL

)

Median 25%-75% Non-Outlier Range

0

20

40

60

80

100

120

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Months

Pe

rce

nt

(%)

pre

gn

an

t a

nd

la

cta

tin

g f

em

ale

s

% pregnant females % females lactating

Pregnant and lactating females

Results

Results - Photoperiod

Mean ± SE; p<0.001 (t-test)

SD – short day (8L:16D)LD – long day (16L:8D)

Testes volume Testes mass

0

20

40

60

80

100

120

SD LD

Tes

ticu

lar

volu

me

(mm

³)

0

1

2

3

4

5

6

SD LD

Tes

ticu

lar

mas

s (m

g/g

)

Results - Photoperiod

0

50

100

150

200

250

300

350

SD LD

Pla

sm

a t

esto

ste

ron

e c

on

cen

trati

on

(n

g/d

L)

Testosterone

Mean ± SE; p<0.001 (t-test)

SD – short day (8L:16D)LD – long day (16L:8D)

Discussion

Seasonal reproduction

main breeding season from September – January

reproductively inactive from February – August

But significant increase of testes size from June

rain (September – April) and warmest months (>20°C; September – May)

females lactating until April but last pregnancy January

Reproductive photoresponsiveness (long days)

increase of testes size and testosterone

concentration after 30 days under 16L:8D

Acknowledgments

National Research Foundation

Dave Dewsnap and the staff of the Goro Game Reserve

Field assistants: Jacklyn Chan, Amélie Broucke, Edith Mertz, Luisa

Riato, Khomotso Ntuli, Mathews Sebonego, André Prins, Warren

Matten, Adrian Harwood, Angela Köhler, Darren Pietersen

Dissection & histology: Marietjie Oosthuizen, Hermien Viljoen, Caroline

Yetman

iButtons: Fred Dalerum

others: Babsie Potgieter, Marna Ferreira, Martin Haupt

Nigel Bennett & Chris Chimimba