mammal research institute (mri), department of zoology and entomology, university of pretoria,...
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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