Two separate sightings, two years apart, of the mimic octopus Thaumoctopus mimicus Norman & Hochberg, 2005 are reported from the Inhambane Province of southern Mozambique within the protected waters of the Vilanculos Coastal Wildlife Sanctuary. Individuals were encountered in May 2020 and 2022 in shallow waters, at a depth of less than 30 cm. Both individuals were fully exposed moving along a sandy substrate at the water's edge in a tidal flat. These represent the first documented sightings of T. mimicus in Mozambique, confirming the occurrence of the species along the eastern coast of Africa and extending this species' known range west from the Arabian Sea and south from the Red Sea.

Bobtail squids (Family Sepiolidae) have a variety of sperm storage patterns, but their reproductive biology has not been studied in many species, especially those in Japanese waters. Two species, Austrorossia bipapillata (Subfamily Rossiinae) and Sepiolina nipponensis (Subfamily Heteroteuthinae) inhabit Suruga Bay in Japan. These were sampled approximately bimonthly by trawling at around 500 m between the end of September, 2020 and May, 2022. They were measured for body size (dorsal mantle length) and weighed for gonadosomatic index (GSI) calculation, and their sperm storage mechanism was investigated. The reproductive season occurs from May to October in A. bipapillata and from December to February in S. nipponensis. In both species, spermatangia were deposited inside the mantle cavity as implanted spermatangia. In A. bipapillata, 5.7 ± 6.5 spermatangia were deeply implanted in the opening of the oviduct, and in S. nipponensis 62.7 ± 61.5 spermatangia were attached to the left gill and surface of the connective-tissue capsule enclosing the digestive gland. The GSI was lower and there were fewer spermatophores stored in the spermatophoric sac of A. bipapillata males compared to S. nipponensis, leading us to suggest that it is exposed to weaker sperm competition than S. nipponensis, irrespective of similar sperm storage mechanism in the two species.

Cephalopods are common inhabitants of the deep ocean's mesopelagic zones worldwide, yet very little is known about their behaviour due to the inaccessibility of this environment. Recent studies suggest that, contrary to historical predictions, deep-sea cephalopods exhibit a wide array of visual behaviours. We used in situ footage from remotely operated vehicles, coupled with laboratory observations to assemble the first behavioural ethogram for the juvenile and subadult life stages of the mesopelagic squid, Chiroteuthis calyx. The number of behavioural components we described is comparable to or exceeds those recognized in ethograms of shallow-water teuthids. We used the ethogram to make a detailed behavioural comparison between the juvenile and subadult life stages, and found distinctly different patterns. Behavioural and morphological differences between the two life stages support the hypothesis that juvenile C. calyx mimic the abundant siphonophore Nanomia bijuga, in order to deter predation.

Malcolm Roy Clarke, FRS (1930–2013) made lasting contributions to cephalopod biology through his productive research programme, his commitment to furthering cephalopod biology and his congenial spirit. His professional legacy includes many important contributions. He wrote over 150 scientific papers, book chapters and other scholarly works, including, the Discovery Report on the role of cephalopods in the diet of sperm whales in the Southern Hemisphere, he edited A handbook for the identification of cephalopod beaks, which made the study of trophic interactions more accessible, and with colleagues he developed and instituted the Cephalopod International Advisory Council to provide advice on cephalopods and a framework for international meetings. His impact on marine science was broad and longstanding.

Acceleration data loggers can be used to construct time–energy budgets or identify specific behaviours in free living animals. Within a marine context such devices have been largely deployed on vertebrates with comparatively little attention paid to commercially important invertebrates such as cephalopod molluscs. Here we tested the utility of tri-axial accelerometers to tease apart six discrete behaviours in the common cuttlefish Sepia officinalis. By considering depth profiles in conjunction with body pitch and roll and overall dynamic body acceleration we were able to make distinctions between resting at the seabed, active swimming, mating, post-coital panting and active manoeuvring along the seabed.

Water drift and tidal rise make the use of bonding mechanisms beneficial for small benthopelagic or interstitial marine animals. Chemical adhesives for attachment are very common in molluscs; however, only a few cephalopods have glue producing organs. The family Idiosepiidae is characterized by an epithelial adhesive organ (AO) located on the posterior part of the dorsal mantle area. Previous morphological and histological studies described three non-glandular cell types (basal, interstitial and fusiform cells) and three glandular cell types (goblet, columnar and granular cells) containing protein and carbohydrate components. However, these studies provide different information about the nomenclature and characteristics of the cell types. The present ultrastructural analyses and a 3D reconstruction of the AO of Idiosepius pygmaeus and Idiosepius biserialis therefore serve to investigate the cell distribution, the fine structure of the cells and possible interactions between the cells.We found that basal cells form a continuous cell layer along the basal membrane, overlapped by the other epithelial cells. Embedded in microvilli-covered interstitial cells the glandular cells are more or less evenly distributed within the AO. Goblet and granular cells are solitary glandular cells without conspicuous morphological characteristics, whereas the columnar cells are arranged in dense aggregations of 5–15 cells. Each columnar cell is enclosed by a narrow supporting interstitial cell which contains dense longitudinal filament strands. The secretory process of the cells in the aggregation is synchronized. Each columnar cell aggregate bears approximately two ciliated sensory fusiform cells. The fusiform cells are connected to a neuronal network, aligned along the epithelium base.The results suggest that the bonding system is affected by two secretory cell types (granular and columnar cells). Both are similar in content, synthesis and secretory process but columnar cells are embedded in a particular cell environment. It is unclear in what way this arrangement is associated with the function of the AO. The neurons in several parts of the AO point to a neuronal control of the bonding mechanism. Comparisons with the AO cells of other cephalopods provide no indications for a morphological relationship between the adhesive systems.

Stomach content analyses were performed in 28 dolphins stranded between 1994 and 2007 on the beaches of Rio de Janeiro State (23°06′S 44°18′W/22°14′S 41°54′W), Brazil, comprising six delphinid species: Stenella frontalis (N = 10), Steno bredanensis (N = 7), Tursiops truncatus (N = 4), Delphinus delphis (N = 5), Lagenodelphis hosei (N = 1) and Stenella coeruleoalba (N = 1). Fish otoliths and cephalopod beaks were used to identify the prey species and to estimate the original length and weight. Seven different cephalopod species from six families and 15 fish species belonging to 10 families were identified. Although the fish contribution could be underestimated, cephalopods constituted the group of higher importance, revealing that these invertebrates may represent an important source of energy for delphinids in the region. In this context, the squid Loligo plei should be highlighted due to its important contribution. Most preys were coastal and demersal, and such consumption could indicate coastal foraging habits of the quoted dolphin species. Although dolphins consumed many species of prey in common, they fed on different size-classes of prey. The foraging area of the dolphins could be the same region used by fishing operations, which would represent a risk for incidental capture.

A study of the reproductive biology of the loliginid squid, Alloteuthis subulata in the North Sea, Irish Sea and Portuguese waters was carried out. A predominance of small squid (<50 mm ML) during autumn was observed in all three areas. Multi-modal size-frequency distributions were apparent in both sexes. The greatest complexity was observed in Portuguese waters, with males exhibiting possibly four or more modal size classes. Sexually mature squid were found throughout the year, with generally more mature squid in spring-summer and fewer in autumn-winter. In Portuguese waters, maturity in both sexes peaked in spring, whereas maturity in the other areas peaked in summer. Similar sizes-at-maturity were observed, with male squid maturing over a greater size range (40–125 mm ML) than females (30–50 mm ML). An apparent secondary peak in male maturity at 65 mm ML suggests two different size-maturation patterns in Portuguese waters. Estimates of potential fecundity in the Irish Sea ranged from $\sim $2200–13 500 eggs per female. Mean egg diameters of 0.45 mm and 1.55 mm were recorded for developing oocytes and mature ova, respectively. Three to four modal size classes of oocytes were apparent in each ovary. There was some indication of latitudinal effects on growth, maturation and reproduction of A. subulata across its geographic range. The greater complexity of size-structure in warmer waters suggests that water temperature may be the main factor involved, possibly through shorter incubation times, faster growth and maturation rates and extended spawning periods.

Recruitment variability is commonly attributed to variation in spawning stock size and environmental variability. Here, the abundance of Loligo forbesi in the English Channel was estimated using cohort analysis. Environmental and adult biomass effects on recruitment variation were then tested. A stochastic length-age key was included in the cohort analysis, considering inter-individual variability in age at length. The number of recruits and parental stock biomass per monthly age-class were computed for a series of 13 fishing seasons (1989-2002). Recruitment was examined in relation to adult biomass and environmental parameters (sea surface temperature, SST, and the North Atlantic Oscillation, NAO) at the time of hatching. Recruits were approximately 7 months old and recruitment for each annual cohort occurred between April and August. Squid bigger than the length at maturity were assumed to be spawners. In the spawning season (September December), spawners were 11–13 months old. Parametric stock-recruitment curves (Ricker, Beverton and Holt, Shepherd, etc.) fitted poorly, while SST was negatively correlated with recruitment in a simple linear model. Recruitment was unrelated to NAO. A model combining SST and adult biomass showed that recruitment is probably density-dependent when stock size is high, and negatively correlated with temperature. The study did not indicate obvious recruitment overfishing in the English Channel L. forbesi population.

A new tissue slice preparation of the cuttlefish eye is described that permits patch-clamp recordings to be acquired from intact photoreceptors during stimulation of the retina with controlled light flashes. Whole-cell recordings using this preparation, from the retinas of very young Sepia officinalis demonstrated that the magnitude, latency, and kinetics of the flash-induced photocurrent are closely dependent on the magnitude of the flash intensity. Depolarizing steps to voltages more positive than −40 mV, from a membrane holding potential of −60 mV, induced a transient inward current followed by a larger, more sustained outward current in these early-stage photoreceptors. The latter current resembled the delayed rectifier (IK) already identified in many other nerve cells, including photoreceptors. This current was activated at −30 mV from a holding potential of −60 mV, had a sustained time course, and was blocked in a dose-dependent manner by tetraethylammonium chloride (TEA). The smaller, transient, inward current appeared at potentials more positive than −50 mV, reached peak amplitude at −30 mV and decreased with further depolarization. This current was characterized as the sodium current (INa) on the basis that it was inactivated at holding potentials above −40 mV, was blocked by tetrodotoxin (TTX) and was insensitive to cobalt.

Intracellular perfusion of the photoreceptors, via the patch pipette, demonstrated that U-73122 and heparin blocked the evoked photocurrent in a dose-dependent manner, suggesting the involvement of the phospholipase C (PLC) and inositol 1,4,5-triphosphate (InsP3), respectively, in the phototransduction cascade. Perfusion with cyclic GMP increased significantly the evoked photocurrent, while the inclusion of phorbol-12,13-dibutyrate reduced significantly the evoked photocurrent, supporting the involvement of cGMP and the diacylglycerol (DAG) pathways, respectively, in the cuttlefish transduction process.

The deep sea is the largest habitat on earth. Its three great faunal environments – the twilight mesopelagic zone, the dark bathypelagic zone and the vast flat expanses of the benthic habitat – are home to a rich fauna of vertebrates and invertebrates. In the mesopelagic zone (150–1000 m), the down-welling daylight creates an extended scene that becomes increasingly dimmer and bluer with depth. The available daylight also originates increasingly from vertically above, and bioluminescent point-source flashes, well contrasted against the dim background daylight, become increasingly visible. In the bathypelagic zone below 1000 m no daylight remains, and the scene becomes entirely dominated by point-like bioluminescence. This changing nature of visual scenes with depth – from extended source to point source – has had a profound effect on the designs of deep-sea eyes, both optically and neurally, a fact that until recently was not fully appreciated. Recent measurements of the sensitivity and spatial resolution of deep-sea eyes – particularly from the camera eyes of fishes and cephalopods and the compound eyes of crustaceans – reveal that ocular designs are well matched to the nature of the visual scene at any given depth. This match between eye design and visual scene is the subject of this review. The greatest variation in eye design is found in the mesopelagic zone, where dim down-welling daylight and bioluminescent point sources may be visible simultaneously. Some mesopelagic eyes rely on spatial and temporal summation to increase sensitivity to a dim extended scene, while others sacrifice this sensitivity to localise pinpoints of bright bioluminescence. Yet other eyes have retinal regions separately specialised for each type of light. In the bathypelagic zone, eyes generally get smaller and therefore less sensitive to point sources with increasing depth. In fishes, this insensitivity, combined with surprisingly high spatial resolution, is very well adapted to the detection and localisation of point-source bioluminescence at ecologically meaningful distances. At all depths, the eyes of animals active on and over the nutrient-rich sea floor are generally larger than the eyes of pelagic species. In fishes, the retinal ganglion cells are also frequently arranged in a horizontal visual streak, an adaptation for viewing the wide flat horizon of the sea floor, and all animals living there. These and many other aspects of light and vision in the deep sea are reviewed in support of the following conclusion: it is not only the intensity of light at different depths, but also its distribution in space, which has been a major force in the evolution of deep-sea vision. “Now that he had seen him once, he could picture the fish swimming in the water with his purple pectoral fin set wide as wings and the great erect tail slicing through the dark. I wonder how much he sees at that depth, the old man thought. His eye is huge and a horse, with much less eye, can see in the dark.”The Old Man and the Sea, Ernest Hemingway

Theory predicts that, in a closed exploited population showing no sampling or other bias, the mean age of fish or squid between one sampling date and the next should increase by the time interval between samples. Age data, derived from statoliths, have been used to test the hypothesis that the effect of migration through an area where a population of Loligo gahi is sampled would be apparent as an increase in mean age per modal group of less than one day per daily time interval between samples. The data show that, in both females and males, the relationship between mean statolith increment number and elapsed time between samples is positive in some months and negative in others. The months in which the relationship between mean increment number and elapsed time is negative are similar to those months in which recruitment has previously been demonstrated to occur, in February, April/May and September for both females and males. Cohorts of squid remain available to the fishery from June–September (females) and February–May and June–July (males) thus allowing mean monthly growth rates of 0.4 mm d−1 for females and 0.7 mm d−1 for males to be calculated. The present study shows that putative age data derived from statoliths apparently demonstrate some sampling biases within a fishery and their effects on the measurement of growth. Migration through the sampled population is manifested by an increase in mean increment number of less than one per day between samples, and growth can only be assessed where the increase in mean increment number is not significantly different from the time elapsed between samples.

In the summer of 1995/96, 25 southern elephant seals, Mirounga leonina, were stomach lavaged at Stranger Point, King George Island, South Shetland Islands. Cephalopod remains were present in 72% of the individuals sampled (n = 18). Seven species of squid and three of octopus were identified. The squid Psychroteuthis glacialis was the most important prey in terms of numbers (77%), biomass (80.8%) and frequency of occurrence (94.4%). Next in importance in terms of mass was the squid Alluroteuthis antarcticus (7.8%) in the diet of females and the octopodid Pareledone ?charcoti in the diet of males (13.2%). Females preyed on a wider variety of squid taxa than males (7 vs 3) but octopodids occurred only in stomach contents from males. The predominance of P. glacialis in the prey of the South Shetland Islands elephant seals can be explained by the southerly location of the foraging areas of this population compared to South Georgia, Heard and Macquarie islands, where the diet of southern elephant seals has previously been analysed. Psychroteuthis glacialis is the predominant squid in waters close to the Antarctic continent.

The most familiar examples of erectile tissue are the genitalia of mammals, notably the penis and clitoris. Among the soft-bodied invertebrates, erectile tissue is virtually unknown, even in sex organs. Here we report that the ligula, the copulatory organ that is a modification of an arm tip of male octopuses, is erectile in Octopus bimaculoides. The normally minute ligula was observed during an unsuccessful mating attempt to be engorged. Histological sections of the ligula reveal striking structural convergences with mammalian erectile tissue: large, well-vascularized internal cavities subdivided by networks of collagen fibres and enclosed by an array of collagen fibres. This internal structure differs markedly from the dense, three-dimensional array of muscles and connective tissues seen in the other octopodid ligulae examined. Erectile tissue may represent an evolutionary compromise between opposing selective forces. Small ligulae may be advantageous because O. bimaculoides hunts in daylight and the white-faced ligula may be conspicuous to predators. Large ligulae, however, may be advantageous if the intense sexual selection thought to occur among octopodids selects for large ligulae, which can transfer larger spermatophores that carry more sperm. An erectile ligula may minimize the impact of these opposing selective forces.

A type of apparent photoreceptor, the nuchal organ, is described in the sepiolid squid Euprymna scolopes. These vesicles are identified in a variety of other cephalopod species. The nuchal organs have specific structural similarities to the already well-described photosensitive vesicles. Both organs have a distinct vesiculate structure and possess a rind consisting of several types of cells. Certain rind cells from both organs send processes with microvilli into the lumen of the vesicle forming a core area. Within the cores of both organs numerous microvilli occupy much of the core volume. These histological similarities provide strong evidence that the nuchal organs, like the photosensitive vesicles, are photoreceptors. Three distinct differences also exist between the nuchal organs and photosensitive vesicles: (1) the location of the nuchal organs differs from that of all known photosensitive vesicles in cephalopods; (2) the location of the nuchal organs is highly conservative in decapod cephalopods compared to the varying locations of the photosensitive vesicles; (3) the degree of structural order generally found within photosensitive vesicles is not apparent in the nuchal organs. The function of the nuchal organ is probably different from previously described photoreceptors in cephalopods.

This study sought to determine if the tropical loliginid squid Photololigo sp. stores energy in the form of lipid, carbohydrate or protein for reproductive investment. Individuals were examined for changes in morphometry, mantle muscle structure and concentrations of water, lipid, carbohydrate and protein in muscle tissue and the digestive gland, associated with the stage of reproductive maturation. Muscle mass was affected by reproductive maturation in females. Mature individuals were lighter for their length compared with females in the early stages of maturation. Concentrations of lipid and carbohydrate in the muscle tissue were very low, and female Photololigo sp. showed equivocal evidence of declining lipid and carbohydrate levels with egg production. There was no evidence of dramatic changes in protein concentration in the mantle muscle with reproductive maturation. Male Photololigo sp. showed a change in the digestive gland with maturation, with water content increasing and protein concentrations decreasing. The digestive gland of both male and female Photololigo sp. increased in size and contained less water with growth. There was little evidence that the storage and transfer of energy for reproduction occurred in Photololigo sp. Instead, it is probable that energy for reproduction is predominantly sourced directly from consumed food.

Observations were made in Senegal between 1997−1998 on the length of embryonic development in Octopus vulgaris. The data were from eggs which had been laid by two females in the open sea and fourteen females in concrete tanks. The observations in natural surroundings are the first concerning this species. Hatching occurred after 15−42 d at 27 °C, 29−49 d at 22−23 °C, 57−65 d at 21 °C and 80−87 d at 17 °C. These values are higher than the few data previously recorded in European aquariums, particularly for temperatures under 20 °C.