研究紹介海洋高次捕食者、特に板鰓類の生物学的・生態学 - 東海大学

研究紹介
海洋高次捕食者、特に板鰓類の
生物学的・生態学的研究
生物資源科学コース
清水校舎
田中彰
高次捕食者の役割と現状
栄養段階
トップダウン
効果
• 下位段階の過度な生産
を抑制し、安定した生態
系の構築に寄与。
• 漁業活動による高次捕
食者の減少。
• 食物連鎖の単純化。
• 生態系の脆弱化。
高次捕食者の生物学的・
生態学的知見の充実
研究項目
• 分布・生息場
養育場の保護
• 繁殖
繁殖様式
繁殖価
成熟
• 年齢・成長
成長率
寿命
成熟年齢
• 食性
摂餌物・摂餌量
捕食器官・行動
• 多様性
ある海域の軟骨魚類の種多様性
個体群内の遺伝的多様性
同腹胎仔間の遺伝的多様性
• 分類・系統類縁
形態学的・分子生物学的手法に
よる種査定・系統関係
調査海域
駿河湾、八丈島・石垣島周辺海域
研究例
Age, Growth and Genetic Status of White Shark,
Carcharodon carcharias, from Kashima-nada, Japan
Sho TANAKA*1, Toru KITAMURA*2, Toshihiko MOCHIZUKI*3 and Kazuya KOFUJI*3
*1School of Marine Science and Technology, Tokai University,
*2 Environmental Science Laboratory, Japan NUS Co., *3 Ibaraki Prefectural Oarai Aquarium
The great white shark is included in the category of “Vulnerable” on the IUCN Red List and in
CITES Appendix II.
In Japan, the white sharks are rarely caught with coastal fisheries as large set nets or gill nets.
Recently, the white sharks around South Africa, Australia, New Zealand and California are
studied actively on the movements, habitats and population structure by electric tags and
DNA analysis.
These reveal that white sharks move large spatial areas; South Africa to Australia, New Zealand
to Australia and California to Hawaii.
However, their biological and ecological information around Japan are little known (Nakaya,
1993,1994; Uchida et al. 1996).
We hypothesized that the life history traits would vary among populations because the
conditions of the species’ various habitats are diverse and change through time.
The objectives of this study were to: (1) show a simple means of enhancing the visibility of
growth bands accumulated in the corpus calcareum of white shark centra, (2) estimate the
age and growth rate from the band counts, and (3) examine the relationship between white
sharks caught in Japanese waters with other populations in the Indian and Pacific Oceans
using genetic techniques.
Marine and Freshwater Research;62 (2011)
(a)
A
C
B
D
(b)
E
(e)
(c)
(d)
Fig.1 X-radiographs of a whole centrum (a) and only half of a corpus calcareum (b-e)
in the white shark. (a,b) Male of 442.0 cm TL with 12 bands. (c) Female of 383.2 cm
TL with 5 bands. (d) Male of 310.9 cm TL with 4 bands. (e) Male of 231.4 cm TL with
2 bands. Scale bars = 10 mm.
500
500
Female
Total length (cm)
Male
450
450
400
400
350
350
300
300
250
250
200
200
Symbols with observed TL
150
100
231.4
310.9
353
364.6
323.9
381
406
408
411
426.4
442
150
100
50
50
0
0
0
1
2
3
4
5
6
7
8
9
10
11
12
0
1
2
3
231.8
280.4
320.2
360.0
383.2
398.2
446.3
482.0
4
5
6
Age (years)
Fig. 3. Back-calculated lengths at age of individual white sharks using the Fraser-Lee
equation .
7
600
Total length (cm)
500
400
300
200
MaleVBG
FemaleVBG
CA
SA
100
0
0
2
4
6
8
10
12
14
16
18
Age (years)
Fig. 4. von Bertalanffy growth curves of white sharks from Japan, California (CA) and
South Africa (SA). Closed and open circles indicate observed length of males and
females, respectively.
Table 2. Growth parameter estimates and goodness-of-fit from the von
Bertalanffy growth model for male and female white sharks
Male
Parameter
Estimate
Female
95% confidence limits
Estimate
95% confidence limits
k (year-1)
0.196
0.158
0.234
0.159
0.130
0.167
L∞ (cm)
455.0
439.7
472.6
606.7
591.5
635.4
t0
-1.92
-1.64
-2.23
-1.80
-1.63
-1.93
(year)
L0 (cm)
χ2cal
142.5
2.130 (P=0.546)
150.7
4.259 (P=0.239)
von Bertalanffy growth model
Lt = L∞(1-EXP(-k(t-t0)))
8000
80
6000
70
60
5000
50
4000
40
3000
30
Maturing
female
2000
1000
20
10
0
0
100
150
200
250
300
350
400
450
500
Total length (cm)
Fig. 5. Relationship of total length with gonad weight and clasper length in white
sharks from Japan .
Clasper length (cm)
7000
Gonad weight (g)
Maturing male
Ovary
Testis
Clasper
Table 3. FST estimates for pairwise comparisons among four white shark
populations in Indo-Pacific OceansFST values are all significant (P<0.001)
Japan
California
0.828
California
Australia & New
Zealand
GU002308 CA
GU002321 CA
GU002310 CA
GU002312 CA
GU002313 CA
GU002314 CA
GU002309 CA
GU002307 CA
‐
GU002306 CA
GU002317 CA
GU002305 CA
Australia & New Zealand
0.433
0.343
‐
South Africa
0.938
0.951
0.855
GU002315 CA
GU002316 CA
GU002303 CA
GU002320 CA
GU002302 CA
GU002304 CA
Fig. 6. Genetic relationship
of 56 white sharks from 5
locations inferred using the
Neighbor-Joining method.
GU002311 CA
GU002318 CA
AY026205 Au
ｶﾘﾌｫﾙﾆｱ、ｵｰｽﾄﾗﾘｱ
ﾆｭｰｼﾞｰﾗﾝﾄﾞ
AY026204 Au
GU002319 CA
AY026209 NZ
AY026202 Au
AY026208 NZ
AY026197 Au
AY026207 NZ
AY026196 Au
AY026203 Au
AY026210 NZ
The bootstrap consensus was
inferred from 1000 replicates.
The tree is drawn to scale, with
branch lengths in the same units
as those of the genetic distances
used to infer the phylogenetic
tree. The genetic distances are in
the units of the number of base
substitutions per site. There
were a total of 403 positions in
the final dataset. The bootstrap
values are indicated near nodes.
AY026200 Au
AY026198 Au
AY026199 Au
D-loop region sequences
of mitochondrial DNA
AY026201 Au
AY026206 Au
No 2 Jp
No 1 Jp
No 3 Jp
No 5 Jp
No 7 Jp
No 4 Jp
日本
No 6 Jp
AY026212 SA
AY026219 SA
AY026213 SA
AY026214 SA
AY026217 SA
AY026222 SA
AY026223 SA
南アフリカ
AY026220 SA
AY026221 SA
AY026216 SA
AY026224 SA
AY026215 SA
AY026211 Au
Genetic distance
AY026218 SA
Au: Australia
CA: California
Jp：Japan
NZ: New Zealand
SA: South Africa
Summary
• The von Bertalanffy growth parameters were estimated at L∞=455 cm TL,
k=0.196 year-1 and t0=-1.92 years for males and L∞=607 cm TL, k=0.159
year-1 and t0=-1.80 years for females.
• The growth rate to maturity was higher than that known for individuals
from California and South Africa.
• Male sharks matured at 310 cm TL and an age of 4 years, and females
began to mature at about 450 cm TL and 7 years.
• The D-loop region sequences of mitochondrial DNA extracted from
Japanese white sharks and GenBank datasets from sharks of California,
Australia, New Zealand and South Africa indicate that Japanese white
sharks formed a monophyletic clade, separate from the populations of
other regions.
• The results suggest that unique life history traits of Japanese white sharks
may be caused by genetic differences.
進行中の研究
• Growth of young smooth hammerheads, Sphyrna zygaena, in the inner area of
Suruga Bay, Japan. 15th EEA Scientific Conference (2011)で発表、論文作成中。
• Morphological and genetic comparison of the genus Deania between European and
Japanese waters. Symposium: Biology of Deep-water Chondrichthyans [Sponsored by AES]
August 8 - 14, 2012: Vancouver, BC Canadaで発表予定。
共同研究
• 東海大学医学部
Genetic and family structure in a group of 165 common bottlenose dolphins caught off the
Japanese coast. Marine Mammal Science 2012
Sequence analysis and phylogeny of whole mitochondrial genomes from Hexanchiform sharks.
BMC Evolutionary Biology 投稿中
• 国立遺伝学研究所
反復配列の変異がもたらすミトコンドリアDNA調節領域の多様性と進化
学会発表予定
• Radboud University Nijmegen
SEARCH FOR THE PRESENCE OF THE CL- CHANNEL PHOSPHOLEMMAN IN ORGANS AND TISSUES
OF THE FRILLED SHARK CHLAMYDOSELACHUS ANGUINEUS . 投稿準備中

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