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Research Article
ScienceAsia 25 (1999) : 003-021 |doi: 10.2306/scienceasia1513-1874.1999.25.003
Classification of Germ Cells, Reproductive Cycle
and Maturation of Gonads in Haliotis asinina Linnaeus
Prasert Sobhona, Somjai Apisawetakana, Malee Chanpooa, Chaitip Wanichanona,
Vichai Linthonga, Amporn Thongkukiatkulc, Padermsak Jarayabhandd,
Maleeya Kruatrachueb, Suchart E Upathamc and Tanate Poomthonge
ABSTRACT: Germ cells in the gonads of Haliotis asinina, a species of abalone found along the coast of
Thailand, were classified basing on light and electron microscopies. Germ cells in oogenetic units could
be classified into six stages according to their histological and ultrastructural characteristics: oogonium
and five stages of oocytes, ie, Oc1 with light to intense basophilia and abundant polyribosomes, with
some in large aggregates; Oc2 with intense basophilia, oil droplets, numerous well developed Golgi
complexes and rough endoplasmic reticulum, but little secretory granules; Oc3 with a few yolk granules
and 2 types of cortical granules; Oc4 with increasing number of yolk granules, numerous cortical granules
and thin jelly coat; and Oc5 is the mature ovum with 2 types of yolk granules, numerous cortical granules
and fully formed jelly coat. The cells in spermatogenetic units could be classified according to the
pattern of chromatin condensation into thirteen stages: spermatogonium, five stages of primary
spermatocytes, secondary spermatocyte, four stages of spermatids and two stages of spermatozoa.
The gonads of adult H asinina reared in land-based culture system exhibit five phases of reproductive
cycle during the year: these are proliferative, premature, mature, spawning and spent phases. Gonads in
proliferative and premature phases contain primarily gonial cells, early oocytes1-3 and spermatocytes,
while mature phase contains mainly late stage cells, ie, oocytes4-5 in ovary and spermatids and spermatozoa
in testis. The spawning phase occurs at least twice during each year: from March to April and August to
October in females, and with similar intervals but slightly prolonged duration in males. Spent phase,
occurring after the period of spawning, is characterized by a complete discharge of gamete cells and the
breakdown of connective tissue stroma. It takes approximately 5 to 6 months for gonads to regenerate
their connective tissue stroma and germ cell population, and finally become repleted with mature
cells again.
In developing H asinina definitive gonads appear to be clearly separated from hepatopancreas at 2 months.
Histologically, gonial cells appear at 2 months, early spermatocytes and spermatids at 4 months; early
oocytes (Oc1-2) at 6 to 7 months. While completely mature spermatozoa could arise in the gonads as
early as 6 to 7 months, mature oocytes (Oc4-5) occur much later at 10 to 11 months. The male animals
tend to reach full sexual maturity and start normal reproductive cycle as early as 7 to 8 months, while
female animals reach sexual maturity and start reproductive cycle around 11 to 12 months.
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a Department of Anatomy, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
b Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
c Department of Biology, Faculty of Science, Burapha University, Chonburi 20131, Thailand.
d Department of Marine Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
e Coastal Aquaculture Development Center, Department of Fishery, Ministry of Agriculture and Cooperatives, Klong Wan, Prachuabkirikhun 77000, Thailand.
Received 29 Jan 1999
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