Marine Biology (1995) 123:505-510 9 Springer-Verlag 1995 T. Cortez 9 B. G. Castro - A. Guerra Reproduction and condition of female Octopus mimus (Mollusca: Cephalopoda) Received: 1 December 1994/Accepted: 24 February 1995 Abstract The relationship between reproduction and condition was studied in a 15 mo sample of 919 matur- ing, mature and post-spawning female Octopus mimus (388 to 3714g) caught in Iquique (North Chile). O. mimus is a semelparous species, with reproduction tak- ing place all year round. Investment in reproductive tissues was, on average, 9.9% of mature female body weight, independent of season. However, somatic growth during maturation was dependent on season and varied between 26 and 63% of the whole-body growth in weight. The condition of females did not vary markedly until spawning, although seasonal variations were apparent, winter being the most unfavourable. Condition deteriorated dramatically after spawning, during parental care of the eggs. During this period, somatic-tissue depletion, mainly from the muscles, was > 25% of the total body weight of mature females. The fecundity of O. mimus was probably limited by the costs associated with parental care of the eggs. Introduction Reproduction and condition are two extremely inter- dependent phenomena in the life cycles of organisms. Reproduction frequently taxes the condition of an or- ganism, and condition can determine the occurrence Communicated by A. Rodriguez, Puerto Real T. Cortez x (12N) Universidad Arturo Prat, Avenida 11 Septiembre 2120, Iquique, Chile B. G. Castro - A. Guerra Instituto de Investigaciones Marinas (CSIC), E-36208 Vigo (Pontevedra), Spain Present address: i Instituto de Investigaciones Marinas (CSIC), E-36208 Vigo (Pontevedra), Spain and intensity of the reproductive events (Silby and Calow 1986). The degree to which condition is affected by reproduction depends on the species concerned, but in general the condition of semelparous species is much more affected than that of iteroparous species (Calow 1979). The degree of interdependence of the two phenomena will also be affected by environmental factors. The Cephalopoda is a group of molluscs with a varied range of reproductive strategies, from typically semelparous, e.g. many Octopus species, to fully iter- oparous, e.g. Nautilus spp. (Mangold et al. 1993). Some species, e.g. Stenoteuthis oualaniensis (Harman et al. 1989), Illex argentinus (Hatfield and Rodhouse 1992), or Idiosepius pygmaeus (Lewis and Choat 1993), mature (Illex argentinus ) and lay eggs (S. oualaniensis and I. pygmaeus) apparently without any important loss of somatic mass, whereas in other species such as Loligo opalescens (Fields 1965) or O. vulgaris (Mangold 1983), spawning individuals are in poor condition. Labora- tory-maintained female O. vulgaris stop feeding two or more weeks before a single spawning period; during this period they divert nutrients from somatic tissues to egg production (O'Dor and Wells 1978). This pattern seems to be general for other Octopus species; but there are also some exceptions such as O. chierchiae, which spawns several times, feeding and growing between each spawning event (Rodaniche 1984). Octopus mimus Gould, 1852 occurs off the Pacific coast of South America, from Peru to the North of Chile (Guerra et al. 1995), an area subjected to con- siderable environmental variation, sometimes as excep- tional and unpredictible as E1 Nifio events (Barber and Chfivez 1986). In common with many other Octopus species, O. mimus is probably semelparous, reproducing but once in its life time, during a short period of time in captivity its spawning period can be as brief as 10 d. The perpetuity of a semelparous species is largely dependent on the survival of eggs and newly hatched individuals, the life-history stages most vulnerable to