Diapositiva 1

1
Cephalopod International Advisory Council,
CIAC09 Symposium. Vigo (Spain), 3-11 September
2009
Age validation in common octopus, Octopus
vulgaris Cuvier 1797, using stylet increment
analysis
Hermosilla, C.A.1, Rocha, F.1, González, A.F.2,
Guerra, A.2 and Fiorito, G.3 1. Dpto. Ecología y
Biología Animal. Universidad de Vigo. Spain. 2.
Instituto de Investigaciones Marinas (CSIC).
Eduardo Cabello 6, 36208 Vigo, Spain. 3.
Laboratorio di Neurobiologia, Stazione Zoologica
A. Dohrn, Villa Comunale, 80121 Napoli, Italy.
Introduction The common octopus, Octopus
vulgaris Cuvier, 1797, is the most important
commercially harvested octopus species. However,
although this is a well-known cephalopod species,
only a few ageing studies were made. Two hard
structures have been used in ageing studies
regarding octopods beaks and stylets. In this
sense, stylets seem to be the most promising
structure to age studies. We present here the
validation of the daily periodicity of growth
increments in stylets of laboratory reared
Octopus vulgaris specimens. Daily periodicity was
corroborated by staining the stylets either with
oxytetracycline or tetracycline and comparing the
number of rings produced with the elapsed days.
Figure 1. Photograph showing the fluorescent
Oxytetracycline (OCT) stylet mark in a female of
1140 g (stained with 124 mg OTC per Kg).
Material and Methods A total of 19 individuals
(10 males and 9 females, 680 to 1470 g body
weight) were marked with oxyetracycline (OTC) in
Vigo facilities (mean of 124 mg OTC per Kg of
octopus) and 6 individuals (1 male and 5 females,
248 to 570 g body weight) were stained with
tetracycline (TC) in Naples (mean of 120 mg/Kg).
The animals were successfully maintained in
captivity until sacrificed for up to 6 (1
specimen), 9 (1 specimen), 18 (6 specimens from
Naples) and 21 (17 specimens) days. Stylets were
removed from specimens and fixed in 4 formalin.
Transverse stylet sections were embedded in
thermo-plastic resin and polished until a thin
and translucent section was achieved. Several
sections of each stylet were prepared and
photographed (Figures 1 and 2). Increments were
counted 3-5 times by two different readers.
Increments counts for each stylet were analysed
and outliers excluded using statistical methods.
Figure 2. Light photograph showing the stylet
increments in the same specimen of Fig.1. Arrows
showing the location of OTC mark.
Results and discussion The number of increments
counted was 18.91.4 and 20.51.5 days for 18 and
21 days specimens, respectively (Figure 3). Mean
rate of increments formation was 1.02 increments
per day (1 increment 1 day). Photograph
analysis corroborated the regular deposition
pattern of stylet growth increments (Figures 1
and 2). Consequently, this study successfully
validates daily increments deposition in stylets
of Octopus vulgaris to the size range analysed.
Acknowledgements This research was supported by
ECOSUMMER actions (European Union). C. Hermosilla
has an early training ECOSUMMER (Marie Curie
Action). F. Rocha is an Isidro Parga Pondal
Researcher. Animals were housed and maintained at
ECIMAT (University of Vigo, Vigo, Spain) and
Stazione Zoologica A. Dohrn (Napoli, Italy).
Figure 3. Relationship between number of days
elapsed after OTC staining and number of
increments counts between OTC mark and stylet
border.