Description: Reproductive maturity and morphometric characteristics were compared for two samples of the octopus Eledone cirrhosa from geographically widely separated sites, Aberdeen, Scotland (320) and Banyuls, France (285).At the two locations the collecting period was synchronized (13 months) and laboratory procedures standardized. In both samples the sex ratio was strongly biased to females, which were about twice the body size of the males. Both sexes were significantly larger in the northern population. Analysis of a limited selection of morphometric characters (mantle, arms, brain and body weight) showed significant differences, but these were insufficient to confirm any divergence in body shape between the two populations.

Description: A preparation of the mantle of Octopus which is inverted over a solid support and which exposes the stellate ganglion and associated nerves is described. 2. Afferent activity can be recorded from stellar nerves following electrical stimulation of the pallial nerve. The latency and frequency of the phasic sensory response is correlated with the contraction of the mantle musculature. 3. It is proposed that receptors cells located in the muscle, and their activity following mantle contraction, form part of a sensory feedback system in the mantle. Large, multipolar nerve cells that were found between the two main layers of circular muscle in the mantle could be such receptors.

Description: The movements of the isolated buccal mass of Octopus vulgaris have been investigated. The beaks undergo rhythmic cycles of activity in the absence of applied stimulation and after electrical stimulation of the inter-buccal connective. Initial opening, closing, retraction and re-opening phases of movement are described. This cycle of movements is taken to resemble those in the intact animal. Anatomical and electrical evidence identifies the superior mandibular muscle as being partly responsible for the closing and retraction phases of movement. The inferior buccal ganglion determines the sequence of these buccal movements, but modification by sensory feed-back from the musculature is also implied. The preparation will allow a closer comparison of the control of movement in cephalopods and gastropods.

Description: The major light and dark components of body displays are described and classified for the octopus Eledone cirrhosa (Lamarck) under aquarium conditions. Comparisons are made with Octopus vulgaris and Eledone moschata. Upon the basic similarity of white display components in the three species is superimposed a trend of modification. Dark components are less various in Eledone cirrhosa and although the chromatophores are organised with leucophores into chromatic units these are not clearly limited morphologically by “grooves”. The mottle patterns of Eledone seem to be arranged along the longitudinal and latitudinal (radial) axes of the animal, the grade of mottle does not respond to grade of background contrast.

Description: Studies of sexual maturation have been made on a large sample of Eledone cirrhosa from the North Sea off Aberdeen, Scotland. In females the wet weights of the ovary and oviducal glands have been recorded for a wide range of body sizes and related to the total body weight. The length dlstribution of a sample of eggs from each ovary was also measured. Assessed either by ovary enlargement or the mean egg length, female E. cirrhosa become mature at a wide ränge of body size and so state of maturity is not predictable from size of the animal. In males the total weight of genital bag is, by contrast, clearly correlated with body weight although this is not true for testis alone, presumably because of transfer of sperm from testis to spermatophoric sac.

Description: The growth of the octopus Eledone cirrhosa has been studied in a population from the North Sea off Aberdeen. Data are presented for the growth of individuals isolated in aquarium conditions; the growth of size classes in thefieldpopulation; and preliminary information on the growth relationships of gonad, somatic, cardiac and brain components of the body. At 15 °C Eledone cirrhosa is capable of growing from 10 to 1000 g in 270 days. From octopuses which feed readily in captivity, weight specific growth rates of up to about 3–5 % day-1 for animals of 100 g body weight are recorded, falling to a maximum of about 1–5 % day-1 at body sizes above 500 g. Females stop growing when sexually mature, but in the sample captured they were consistently larger than males, a feature which may account for the 7:1 bias towards the incidence of females. On a wet-weight basis, the mean food incorporation into growth is 37 % of the food ingested, which is 49% of the gross weight of crabs killed. Field data for 1978/79 suggest that animals recruited to the population at the beginning of the year grew steadily until December, overwintered without growing, then grew rapidly for several months in the subsequent year before disappearing from the samples. The estimated average age of those animals and by implication, the life span, is 20 months.

Description: Microsatellite DNA markers developed for the squid Loligo forbesi were used to determine the genotype of a series of embryos obtained from egg strings of individual females. The results demonstrate that at least 2 males had been successful in fertilizing the eggs of a single female. The findings are compatible with observations of male competition at mating in other species of loliginid squid. They are discussed in relation to interpretation of specific questions of cephalopod ecology.

Description: 1. As a preliminary step towards a fishery management strategy for the squid Loligo forbesi, indices of reproduction, egg production and recruitment were derived for this species in Irish (1991-93) and Scottish (1990-95) waters to give a quantitative estimate of peaks in spawning and fishery recruitment. 2. The indices were derived by combining landings or catch per unit effort (CPUE) data with the estimated proportions of mature squid (reproducers) and immature squid (recruits) to give an index of the number of squid spawning in and recruiting to the fished population each month. 3. The reproductive index peaked between November and December in Irish waters and between December and January in Scottish waters, earlier than predicted by simply examining peaks in the proportion of mature squid. 4. The index of recruitment showed peaks in the autumn in both Irish and Scottish waters, but there was also an additional April peak in Scottish waters. The two periods of recruitment in Scottish waters, together with a decrease in the size of mature females during the spawning season, are not compatible with a single breeding season and possible explanations for this are discussed. 5. By helping to define the timing of the fishing season (to avoid overfishing) and by providing estimates of natural mortality (for assessment of population size), the indices provide important input for population models for fisheries management of squid and short-lived fish species. 6. A possible model for a directed fishery for L. forbesi is proposed. In the model, the start of the fishing season is delayed to prevent growth overfishing and the season curtailed during spawning to prevent recruitment overfishing. However, on the basis of the indices developed here, this leaves only a narrow time window in which such a fishery could operate.

Description: Octopuses ( Eledone cirrhosa (Octopoda: Cephalopoda)) held in an aquarium were subjected to varying conditions of feeding and starvation to evaluate putative indices of feeding and growth. Specific growth rate (%d −1 ) was linearly related to feeding rate (% of the body mass d −1 ) in animals with a mean body mass of 250 g at 15°C. Maximum growth rates varied between 〉 2% d −1 (body weights 〈 300 g) to 〈 1% d −1 (body weights ≤ 900 g) but specific growth rates were not related to body weight. Growth rates became negative (weight loss) after one week without food. The digestive gland index (DGI) was significantly correlated with short and long-term feeding and specific growth rates, and with body weight. Muscle RNA concentration was linearly correlated with growth rate during the previous 1–3 weeks but not with feeding rate. RNA:protein ratios were not different between mid-arm and mantle sample sites but arm tip values were significantly higher. RNA:protein ratio was related to body weight only in feeding animals. It is concluded that DGI is an index of feeding rate and that RNA:protein ratio can be used as an index of recent (~ 4 weeks) growth rate.