Additional information on the biology of Argonauta argo (Cephalopoda:Octopoda) in the Mediterranean Sea from gastrointestinal contents of Risso's dolphin

2005·2.2 MB·English

by  Carmen Blanco

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SociedadEspañola deMalacología Iberus, 23 (1): 83-86, 2005
Notas breves
Additional information on the biology ofArgonauta argo
(Cephalopoda: Octopoda) in the Mediterranean Sea from
gastrointestinal contents ofRissos dolphin
Aportación a la biología de Argonauta argo (Cephalopoda:
Octopoda) en el mar Mediterráneo a partir del contenido gastroin-
testinal del delfín de Risso
Carmen BLANCO*, Ángeles RADUÁN* andJuanAntonio RAGA*
Recibidoel27-VIII-2004.Aceptadoel14-IV-2005
KEYWORDS:Argonautaargo, Grampusgriseus, cephalopodbiology, Mediterranean.
PALABRAS CLAVE:Argonautaargo, Grampusgriseus, biologíacefalópodos, Mediterráneo.
INTRODUCTION
Argonauta argo Linnaeus, 1758 is a Mediterranean Sea (Laptikhovskyand
cosmopolitan epipelagic octopod living Salman, 2003), but the life span and
in tropical and subtropical waters. It is period of reproduction of the species
sexually dimorphic, with dwarf males continué tobeunknown. The aim ofthis
and females lodged in calcareous shells paper is to provide some data on the
that serve as brood chambers (Guerra, biology of this little known Mediter-
1992). Despite its abundance, whole ranean species by means ofremains col-
animáis are rarely caught, so that their lected from the gastrointestinal contents
life cycle is not completely known. The of Risso's dolphins, Grampus griseus
reproduction of this species shows a (Cuvier, 1812) (Cetácea: Delphinidae), a
protracted and continuous spawning teuthivorous predator (Kruse, Cald-
which has been defined as asynchro- WELLANDCALDWELL, 1999).
nous ovulation with monocycle spawn-
ing reproductive strategy (Rocha,
GuerraandGonzález, 2001). MATERIALAND METHODS
Livingindividuáis ofthis species are
rarely found in the Mediterranean Sea The data analysed in this paper
(BOLETZKY AND CENTELLES, 1979; BELLO carne from gastrointestinal contents of
and Rizzi, 1990; Popper, Barash and eleven Risso's dolphins, Grampus
Galil, 1990). Continuous spawning is griseus, stranded on the west Mediter-
believed to take place in the eastern ranean coast, between40° 25' N, 00° 32'
*CavanillesInstituteofBiodiversityandEvolutionaryBiology, UniversityofValencia,P.O.Box22085,46100
Valencia, Spain. E-mail: [email protected]
83
Iberia, 23 (1), 2005
1 2 3 4 5 6 7 8 9 10 11 12
Figure 1. Annual distribution ofspecimens oíArgonauta argo from gastrointestinal contents of
Mediterranean Risso'sdolphin. N: numberoíA. argo; n: numberofdolphins.
Figura 1. DistribuciónanualdelosejemplaresdeArgonautaargo obtenidosdelcontenidogastrointesti-
naldeldelfíndeRissoenelMediterráneo.
W
and 37° 35' N, 00° 45' E, collected April, is shown in Figure 3; significant
fromApril 1987toJanuary2003.Allgas- length distribution differences were
trointestinal tracts were stored deep- found between these two months (Kol-
frozen (-20°C) and their contents subse- mogorov-Smirnov test, máximum dif-
quently washed through a 0.2 mm mesh ferences between samples= 0.268, N
mm
sieve and preserved in 70% ethanol; (192, 99), P< 0.001), 25.6-28.7 and
mm
glycerine was added to the preservative 31.8-35.0 being the estimated
solutionforcephalopodbeaks. mantle length of modal class in March
The beaks were identified according and April, respectively. In all available
to Smale, Clarke, Klages and samples there were individuáis whose
Roeleveld (1993). Cephalopod mantle mantle length was longer than 35 mm.
length was estimated from hood length An oviscapte with eggs (modal valué
mm
of lower beak (Smale et al., 1993), due size 1.22-1.42 length) was found in
to the frequent rotten condition of the the intestine of a dolphin stranded in
crest. Some underestimating of hood January; this valué may be underesti-
lengthand, henee, mantlelengthmaybe mated due to the possible shrinking
assumedbecauseofthe digestive action. actionofpreservationinalcohol.
RESULTS DISCUSSION
In the gastrointestinal contents of The high number of beaks from A.
Risso's dolphins, 336 lower beaks of argo gathered in this study, in contrast
Argonauta argo were found, hood length with the scarcity oftheir catches (see the
range: 1.31-5.87 mm. Distribution Introduction), corroborates the effective-
through the time period for which data ness of teuthophagous predators as
were available (see Figure 1) shows a cephalopodcollectors (Bello, 1996).
higher number in early spring. The esti- All remains of A. argo found in this
mated mantle lengths are shown in study, apart from one collected inApril,
Figure 2. Significant differences were were ascribed to female specimens
found in the size of specimens through- based on their size, since dwarf males
out the year (nested ANOVA (F9,325 = only reach 10 mm of dorsal mantle
11.1, P < 0.001). The frequeney distribu- length (Guerra, 1992). In accordance
tion ofbeak length (HL) in the months withthesmallestfemale sizeatmaturity
of máximum abundance, March and in the Mediterranean, i. e. 32 mm ML
84
BLANCO ETAL.: Argonauta argo in gastrointestinal contents ofRisso's dolphin
80 3
40-
60 m 20 - _r — March
1
40- e n
-T
20 - April
20-
40-
12
3 4 5 6 7 8 9 10 11 12 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Months Beaklength (HLmm)
Figure2.Annual length distribution ofestimated mande length (ML) ofArgonautaargofrom gas-
trointestinal contents ofMediterranean Risso's dolphin. Box-and-whisker-plot (TUKEY, 1977).
Figure3. Frequencydistributionoflowerbeaklength (HL) oíArgonautaargoinMarchandApril.
Figura2. Distribución anualdela longitudestimadadelmanto (ML) deArgonauta argo apartirdel
contenidogastrointestinaldeldelfín de Risso en elMediterráneo. Gráfico "Box-and-whisker" (TlJKEY,
1977). Figura3. Distribución delafrecuencia dela longituddela mandíbula inferior (HL) deArgo-
nautaargo en marzoyabril.
(Laptikhovskyand Salman, 2003), ma- in the size of specimens through the
ture femaleswerepresentinall sampled year, especially in the two consecutive
seasons. Such a find and the occurrence months could indicate either seasonality
of fertilized eggs in the brooding cham- or a preferential period of spawning
ber from January, in addition to brood- time.
ing females collected in the Adriatic in
November (Bello and Rizzi, 1990) and
ACKNOWLEDGEMENTS
mature females found in the eastern
Mediterranean Sea during winter (Lap-
tikhovsky and Salman, 2003), show This study was supported by Con-
that the spawning period for Mediter- sellería de Territorio y Vivienda, Gener-
ranean A. argo extends longer than pre- alitat Valenciana, and Dirección General
viously believed (from May to October de Conservación de la Naturaleza, Min-
according to Guerra, 1992). Differences isterio deMedioAmbiente.
BIBLIOGRAPHY
Bello, G., 1996. Teuthophagous predators as Kruse,S.,Caldwell,D.K.andCaldwell,M.
collectorsofoceaniccephalopods:thecaseof C, 1999.Risso'sdolphinGrampusgriseus(G.
theAdriaticSea.BollettinoMalacologico,32(1- Cuvier,1812).InRidgway,S.H.andHarrison,
4):71-78. R. (eds.): HandbookofMarineMammals, Vol.
Bello,G.andRizzi,E.,1990.Comportamiento 6,pp. 183-212.AcademicPress,London.
ditrefemminediArgonautaargoinacquario Laptikhovsky, V. andSalman, A., 2003. On
(Cephalopoda:Argonautidae).AttidellaSocieta reproductivestrategiesoftheepipelagicoc-
Italianadi ScienzeNaturaliedelMuseo Cívico topods of the superfamily Argonautidea
diStoriaNaturalediMilano,131:450-452. (Cephalopoda: Octopoda). Marine Biology,
Boletzky,S.V.andCentelles,J.,1979.Argo- 142:321-326.
nautaargo(Mollusca,Cephalopoda)dansla Popper,D.,Barash,A.andGalil,B.S., 1990.
regióndeBanyuls-sur-mer. VieetMilieu,28- Argonauta argo - A rare occurrence off the
29(4):659-660. shoresofIsrael. IsraelJournalofZoology, 37:
Guerra, A., 1992. Mollusca. Cephalopoda. In 51-53.
Ramos,M.A.etal. (eds.):FaunaIbérica,vol. Rocha, F., Guerra, A. andGonzález, A. F.,
1. Museo Nacional de Ciencias Naturales, 2001.Areviewofreproductivestrategiesin
CSIC,Madrid,327pp. cephalopods. BiologicalReview,76:291-304.
85
Iberus, 23 (1), 2005
Smale, M. }., Clarke, M. R., Klages, T. W. Tukey, J. W. 1977. Bob-and-whisker-Plot. In
andRoeleveld,A. C, 1993.Octopodbeak Explanatorydataanalysis,pp.39-43.Addison-
identification-resolutionataregionallevel Wesley,Massachusetts.
(Cephalopoda,Octopoda:SouthernÁfrica).
South African Journal ofMarine Science, 13:
269-293.
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