ANNUAL REPRODUCTIVE CYCLE OF TRIGLA LYRA
Marta Muņoz
1 *
, Maria Sābat
1
, Sandra Mallol
2
and Silvia Vila
1
1
Ārea de Zoologia, Departament de Cičncies Ambientals, Universitat de Girona, Spain - * marta.munyoz@udg.es
2
Centre Oceanogrāfic de Balears, Institut Espanyol dOceanografia, Palma de Mallorca, Spain
Abstract
Seasonal histological changes of the gonads and the condition factor and the gonadosomatic, hepatosomatic and mesenteric fat indices of
Trigla lyrawere studied for both sexes. Sexual dimorphism was not found. The standard length at first maturity was 200 mm for the
females and 180 mm for males. Spawning in Western Mediterranean occurred in late winter, early spring.
Keywords: Trigla lyra, reproduction, annual cycle
Rapp. Comm. int. Mer Médit., 37,2004
406
The piper gurnard (Trigla lyraL., 1758) lives in soft and rocky sub-
strates off the coast up to depths of 700 m (1). In the present work, the
seasonal histological changes of the gonads of piper gurnard were
studied. The condition factor as well as the gonadosomatic, hepatoso-
matic and mesenteric fat indices were analysed.
The annual development of the indices in relation to the maturation
phase of the gonad is shown in Figure 1. The graphs show the average
monthly values of these indices related to reproduction for both sexes.
The ovaries were classified according to the more developed type of
oocyte they contain (2), and the stage of development of the testis was
determined following the criteria of Grier (3).
The gonadosomatic index (GSI = weight of gonad / eviscerated
weight) showed monthly significant differences for both sexes
(ANOVA, p=0.000 for males, and p=0.029 for females). The energy
used up in reproduction is clearly depicted in the changes of the
hepatosomatic (HSI = weight of liver / eviscerated weight) and
mesenteric fat (MFI = weight of mesenteric fat / eviscerated weight),
both of which showed their minimum values after spawning, although
we only detected monthly significant differences for the HSI of
females (ANOVA, p = 0.002). The condition factor (K = eviscerated
weight / standard length
3
) was not affected by reproductive activity,
since its monthly variations are not considered statistically significant
(ANOVA, p>0.05).
The reproductive cycle of piper gurnardstarted in March, when
both the ovary and the testes were in the initial phases of development.
In September, and coinciding with the appearance of the first vitel-
logenic oocytes in the ovaries and the formation of the first spermato-
zoa in the testes, the activity of the gonads begun to increase progres-
sively. The functional maturity period of the testes, when the lobules
and all the ducts were full of sperm, coincided with the observed
spawning period (between January and February).
Information about the spawning period of piper gurnard is a little
contradictory (4,5,6) probably because of the difficulty to obtain large
specimens. Females matured only after they reach a standard length of
200 mm, and males a standard length of 180 mm. In this way,
although we only detected mature oocytes and postovulatory follicles
in January and February, a more prolonged spawning period up to
March cannot be ruled out, because of the lack of large specimens
caught in this month.
The sex ratio was 1.4 in favour of males and differed significantly
from 1 (
?
2
=8.20, g.d.l.=1, p=0.004) especially for smaller sizes. This
agrees with the results from Greek waters (7, 8).
References
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3-Grier H.J., 1981. Cellular organization of the testis and
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4-Bini G., 1969. Atlante dei pesci delle coste italiane, VII. Roma: Mondo
somerso, Roma.
5-Mouneimné N., 1971. Les triglidae de la mer catalane. Distribution,
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(Pisces, Triglidae) of the Greek seas. Cybium,7 (4) :71-88.
Fig. 1. Annual development of the indices related to reproduction. Below
each graph are details of the stage which the gonads are going through.
