Life history of Gonatus onyx (Cephalopoda: Teuthoidea): ontogenetic changes in habitat, behavior and physiology

In the present study 670 individuals of Gonatus onyx (Cephalopoda: Teuthoidea) were observed in Monterey Bay, California from a remotely operated vehicle. The vertical distribution of this species was bimodal, with peaks at 400 and 800 m depth during the day and 300 and 500 m during the night. The bimodal distribution reflects a life stage shift between younger, schooling juveniles living in shallower water and older, solitary adults which live deeper. Ontogenetic changes in behavior associated with this life stage shift are reflected in the physiology of the organisms as well. Both aerobic and anaerobic metabolism, as estimated using mitochondrial and glycolytic enzymes, decline with increasing body mass, suggesting reduced locomotory capacity in deeper-living adults. Oxygen consumption rates were also determined in relation to oxygen partial pressure. Oxygen consumption regulation was similar between juvenile and adult squids. The critical oxygen partial pressures (29 to 30 mmHg) correspond precisely to the oxygen concentrations found at the depth of maximal abundance for day and night populations of juveniles and adults, respectively. Behavioral and physiological changes with ontogeny of G. onyx are believed to result from reduced visual predator/prey interactions in the light-limited deep sea. Received: 7 February 1999 / Accepted: 26 January 2000     

Fecundity and reproductive strategies in deep-sea incirrate octopuses (Cephalopoda: Octopoda)

Coleoid cephalopods show flexibility in their reproductive strategies or mode of spawning, which can range from simultaneous terminal spawning over a short period at the end of the animal’s life to continuous spawning over a long period of the animal’s life. Although a simultaneous terminal spawning strategy is typical of shallow water temperate octopuses, it is not known whether deep-sea octopods would have the same reproductive strategy. The reproductive strategies and fecundity were investigated in nine species of deep-sea incirrate octopuses: Bathypolypus arcticus, Bathypolypus bairdii, Bathypolypus ergasticus, Bathypolypus sponsalis, Bathypolypus valdiviae, Benthoctopus levis, Benthoctopus normani, Benthoctopus sp., and Graneledone verrucosa (total n = 85). Egg-length frequency graphs and multivariate analysis (principal components analysis) suggest that B. sponsalis has a synchronous ovulation pattern and therefore a simultaneous terminal spawning strategy. Although a simultaneous terminal spawning strategy is most likely for B. levis and B. normani, the egg-length frequency graphs and multivariate analysis also suggest a greater variation in egg-lengths which could lead to spawning over an extended period.     

Evidence for multiple spawning in the tropical oceanic squid Stenoteuthis oualaniensis (Teuthoidea: Ommastrephidae)

Indirect evidence suggests that Stenoteuthis oualaniensis is a multiple spawner, a reproductive strategy not reported previously for squid. After spawning once, S. oualaniensis apparently continues to feed, grow, and mature additional oocytes before spawning again. Squid were caught by jigging at night in waters around the main Hawaiian Islands during four cruises from 1981 to 1987. All females from 200 mm mantle length (ML) to at least 318 mm ML were sexually mature, indicating that considerable growth takes place after reaching sexual maturity. Size-frequency analyses of ovarian oocytes revealed continuous egg production throughout adult life. Mature ova are stored in the oviducts, but oviduct fullness is unrelated to body size, indicating repeat spawning.     

Biochemical genetic evidence supporting the taxonomic separation ofLoligo edulis andLoligo chinensis (Cephalopoda: Teuthoidea) from the genusLoligo

Confusion abounds regarding the relative generic status of many member species of the squid family Loliginidae. A taxonomie reorganisation within the family has been proposed in whichLoligo species from the Indo-Pacific possessing photophores on the ink sac, includingLogligo edulis andLoligo chinensis, are removed to the newly created genusPhotololigo. This system of classification has not however gained general acceptance, and some authors have continued to refer to these species asLoligo. Here biochemical genetic data gathered using allozyme electrophoresis are presented supporting the assertion thatL. edulis andL. chinensis should indeed be positioned in a genus distinct from that characterised by the type speciesLoligo vulgaris vulgaris. Cluster analysis of allele frequency data from 22 putative enzyme-coding loci suggests thatL. edulis andL. chinensis are as genetically distant fromL. vulgaris vulgaris as are members of the confamilial generaAlloteuthis, Uroteuthis andSepioteuthis, and as such warrant separate generic status. We conclude that the genusPhotololigo is valid.     

Biology of the deep-sea octopus Bathypolypus sponsalis (Cephalopoda: Octopodidae) from the western Mediterranean Sea

Several aspects of the biology of Bathypolypus sponsalis were studied from 297 individuals (115 males, 180 females and 2 indeterminates) caught in a depth range of 200–800 m depth in the western Mediterranean Sea. The paper presents data on sizes (length-weight relationships, size-frequency distributions) and reproduction (sex ratio, maturation, condition), and also analyses of the diet of B. sponsalis from samples taken throughout the year. Length-weight relationships showed that females are heavier than males at the same mantle length. Although mature individuals were found all year round, the maximum number occurred in spring and summer. Sexual maturation data revealed that males mature at smaller sizes than females. The gonadosomatic index increased with maturity in both sexes; the increase was gradual in males, but abrupt in females. The digestive gland index was used as a condition index and showed a differential behaviour with maturity; it increased gradually in females, but decreased in males. Like other octopus species, B. sponsalis appears to be an opportunistic predator, feeding on a great variety of preys. Stomach content analysis yielded a total of 19 different prey items belonging to four major groups (Crustacea, Mollusca, Ophiuroidea and Osteichthya). The first three groups were the more frequent preys, since crustaceans, molluscs and ophiuroids appeared in 76%, 49% and 30% of the stomachs, respectively. Decapoda Reptantia (among crustaceans) and cephalopods and bivalves (among molluscs) constituted the more abundant prey items. While the Decapoda Reptantia group was significantly more abundant in stomach contents of females, gastropods were taken more frequently by males. These differences in diet could reveal females as a more active predators than males. Received: 5 March 2000 / Accepted: 7 November 2000     

The location of spawning grounds,spawning and schooling behaviour of the squid Loligo vulgaris reynaudii (Cephalopoda: Myopsida) off the Eastern Cape Coast,South Africa

The location of spawning grounds of the squid Loligo vulgaris reynaudii (D'Orbigny) was investigated in the years 1988–1990. At least 39 spawning sites were found during this period along the inshore areas of the Eastern Cape coastline between Algoa Bay and Plettenberg Bay. The substrate chosen for egg laying was mostly fine sand or flat reef, frequently in large and relatively shettered bays. Spawning was found to occur sporadically throughout the year, and some spawning sites were used repeatedly within a particular year and in subsequent years. Squid migrate in discrete schools separated by sex in the vicinity of the spawning sites; these schools mix during spawning. Mating and egg deposition behaviour is described from observations made on the spawning grounds. Cannibalism was seen on a number of occasions, but no post-spawning mortality was recorded. Egg beds consisted mostly of large concentrations of egg strands (>3 m in diameter), with smaller aggregations of one to ten egg strands surrounding these, with single strands in the immediate vicinity. Three basic patterns of echotraces were identified and interpreted according to diving observations. These patterns were classified as loose patches, dense patches, and complex patterns. The first two represent non-spawning schooling patterns and the third, mating and egg laying behaviour. This observation led to the general classification of squid aggregations: schools (non-spawning mode) and concentrations (spawning mode). Concentrations as far as Loligo vulgaris reynaudii was concerned were further divided into two patterns: suprabenthic and benthic (spawning) squid.     

Life history and population dynamics ofKinbergonuphis simoni (Polychaeta: Onuphidae)

The relationship between life-history characteristics and population dynamics were investigated in the onuphid polychaeteKinbergonuphis simoni (Santos, Day and Rice) between 1982 and 1987. The studied population is located in Upper Tampa Bay, Florida, USA. This worm attains sexual maturity at 5 to 10 mo of age, depending on temperature. Several consecutive broods are produced during a female's life time, with 7 to 26 young per brood. Adults die in June–July after the breeding season. Generations of breeding individuals do not overlap and the replacement of generations occurs in July–August. Only one extended breeding season is experienced per life time. Life span does not exceed 2 yr. Field population density in 1982 was high in fall and spring (2000 to 9000 individuals/m²), low in summer (1600 individuals/m²), and slightly depressed in winter (2500 to 4000 individuals/m²). Changes in population density may be explained by seasonal, temperature-controlled changes in instantaneous birth and death rates. Birth rates are high in fall and spring, while death rates are high in early summer. Death of juveniles contributes to the winter density decrease.     

Locomotion modes of deep-sea cirrate octopods (Cephalopoda) based on observations from video recordings on the Mid-Atlantic Ridge

The behaviour of cirrate octopods of the genera Cirroteuthis and Grimpoteuthis in their natural habitat was studied using video recordings. Sequences were filmed during the French cruise “Faranaut”, from the manned submersible “Nautile” at depths between 2702 and 4527 m, in two zones in the Fifteen-Twenty Fracture Zone on the Mid-Atlantic Ridge. Four different modes of active locomotion, namely crawling, take-off, fin-swimming, and pumping, and one apparently passive mode of locomotion, umbrella-style drifting, were observed. Jet-propulsion, a characteristic mode of locomotion typically employed by cephalopods, was not observed in the cirrate octopods filmed, although breathing movements of the mantle to aerate the gills were assumed to generate some slight propulsion through the funnel. Fin-swimming was the mode of active locomotion most frequently observed. Neutral buoyancy was confirmed in one individual after capture. This buoyancy enables passive drifting in the umbrella-style attitude observed in Cirroteuthis spp., possibly using near-bottom ocean currents. Pumping, a mode of slow locomotion generated by peristaltic waves in the primary and intermediate webs, also observed in Cirroteuthis sp., is described here for the first time. The take-off mode of locomotion, a sudden, single contraction of the brachial crown and web, is also described; it was always followed by fin-swimming. No medusoid swimming of the type previously described for opisthoteuthid cirrates was observed. A flight response to the approach of or contact with a strange object, i.e. the submersible, using the crawling, take-off, or fin-swimming modes was observed. A ballooning response was observed in a high-stress situation when a C.magna individual was captured. Received: 27 November 1996 / Accepted: 9 December 1996     

Laboratory rearing of Sepiolinae (Mollusca: Cephalopoda)

Five species of Sepiola and Sepictta were reared in the laboratory from egg to adult size. Spawning was achieved in 3 species of Sepiola after 5 to 7 months. The growth rate of the species reared did not depend upon temperature, which ranged from 12.5° to 20°C. A fairly constant size increase (2.5 mm mantle length/month) was observed in Sepiola during the 5 months after hatching. In Sepietta, the same growth rate was observed until the fourth month after hatching, when it increased to the rate of 5 mm mantle length/month.Laboratoire associé au C.N.R.S.     

Reproduction and condition of female Octopus mimus (Mollusca: Cephalopoda)

The relationship between reproduction and condition was studied in a 15 mo sample of 919 maturing, mature and post-spawning female Octopus mimus (388 to 3714 g) caught in Iquique (North Chile). O. mimus is a semelparous species, with reproduction taking 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.     

Respiratory quotient and calcification of Nautilus macromphalus (Cephalopoda: Nautiloidea)

Respiration and calcification were investigated in the ectocochleate cephalopod Nautilus macromphalus Sowerby. Specimens were collected off New Caledonia, in October 1991, and kept at the Nouméa Aquarium until December 1991. The respiratory quotient and calcification rate of 5 individuals were measured during 14 short term incubations (63 to 363 min). Oxygen uptake was recorded with a polarographic oxygen sensor. CO₂ flux and calcification were calculated from changes in pH and alkalinity (alkalinity-anomaly technique). Several methods were used to compute the respiratory quotient (RQ); a functional regression indicated an RQ of 0.74. CaCO₃ exchange rates were linearly related to respiratory quotient, calcification occurring in individuals with a low RQ. CaCO₃ uptake from the surrounding water was noncontinuous. From the highest CaCO₃ uptake, maximum growth rate was estimated as 7.1 mg shell wt h^- (=61 g yr^-1).     

Vitesse de Digestion d'Octopus cyanea (Cephalopoda: Octopoda)

In the benthic octopus Octopus cyanea Gray, acclimated to high temperature (30°C), digestion takes 12 h. Animal weight and food intake do not influence the duration of digestion. By regulating the rate of food passage in the alimentary canal, the quantity of digested food (as a percentage of ingested food) is kept constant at a particular time. A comparison with other cephalopod species and with different fish species, leads to the conclusion that the mode of life is the main factor determining the duration of digestion and its efficiency. For a given species, the duration of digestion depends on temperature. For a similar mode of life and at equal temperatures, digestion is more rapid and more efficient in cephalopods than in fishes.     

Life history and fishery of Lepidopus caudatus (Pisces: Trichiuridae) in the Catalan Sea (Northwestern Mediterranean)

The frostfish Lepidopus caudatus (Euphrasen, 1788) is a mesopelagic species; it occurs along the shelf and slope down to 450 m in the Catalan Sea. Its' fishery, population structure, growth, diet and reproduction was studied on the basis of commercial statistics from 1984 to 1990 and on samplings made in 1988 and 1989. L. caudatus is fished by two types of commercial method, trawl and long-line; catches by the latter method display a marked seasonality. The minimum size of fish caught is 26 cm total length by trawling and 71 cm by long-line. Maximum sizes are similar for both gears: 196 and 188 cm, respectively. L. caudatus exhibits fast growth and attains an age of 8 yr. It feeds on small mesopelagic prey. It is a partial spawner reproductive activity occurring from April to November. Males attain sexual maturity at 97 cm and females at 111 cm total length.     

Life history and settlement preferences of the edible jellyfish Catostylus mosaicus (Scyphozoa: Rhizostomeae)

 The life history and settlement preferences of larvae of Catostylus mosaicus (Scyphozoa: Rhizostomeae) (Quoy and Gaimard, 1824) were investigated in New South Wales, Australia, over a 2 mo period beginning in November 1998. The life history consisted of an alternation between a sexual, medusoid stage and an asexual, polypoid stage, and was similar to that described for other rhizostomes. Planula larvae were brooded by the adults. Approximately 4 d after collection, larvae settled on a variety of substrata including wood, sandstone, shell, seagrass and glass, and metamorphosed into four-tentacled polyps. The number of tentacles increased and polyps strobilated when they had between 12 and 20 tentacles. Strobilation occurred within 15 d of settlement, but only polyps that settled on the concave surfaces of the shells strobilated. Both monodisk and polydisk strobilation was observed. Ephyrae were raised for one month and were observed developing oral arms. Polyps reproduced asexually via the formation of podocysts, by production of buds, and by partial fission. Received: 30 April 1999 / Accepted: 27 August 1999     

Bioluminescence of deep-sea coronate medusae (Cnidaria: Scyphozoa)

Bioluminescence is the production of visible light by a living organism. The light commonly appears as flashes from point sources (involving one or more cells, usually described as photocytes) or as a glandular secretion. A visible flash usually involves synchronous light emission from a group of cells or, if from a single-celled organism such as a dinoflagellate, from a group of organelles. The number of cells (or organelles) responding synchronously is the main determinant of the flash intensity. Bioluminescence is a common phenomenon in many deep-sea animals and is widespread among the Cnidaria. In this paper, we compare and contrast in situ and laboratory recordings of the bioluminescent responses of specimens of the deep-sea scyphozoans Atolla wyvillei, Atolla vanhoffeni, Atolla parva, Nausithoe rubra, Paraphyllina intermedia, Periphyllopsis braueri and Periphylla periphylla. Displays in all seven species consist of localised flashes and propagated waves of light in the surface epithelium. The first few single waves propagate at rates of up to 60 cm s^-1 but subsequent ones in any sequence of stimuli gradually decrease in speed. After several single wave responses, a subsequent stimulus may elicit multiple waves that persist for several seconds. Following such a frenzy, the specimen becomes temporarily refractory to further stimuli, but if rested will recover its normal responses and may produce further frenzies. The dome area, situated above the coronal groove, of the genera Paraphyllina, Periphylla, and Nausithoe is covered with luminescent point sources. Such point sources are generally absent from the dome of species of Atolla. Captured specimens of A. parva also produce secretory bioluminescence, corroborating prior in situ observations of this ability. Secretory bioluminescence in P. periphylla takes the form of scintillating particles released from the lappet margins. We did not observe secretory displays in specimens of any other species in the laboratory, but one instance of apparent secretory luminescence was recorded in situ in a specimen of A. wyvillei.Communicated by J. P. Thorpe, Port Erin     

Regulation of respiration during juvenile development of Sepia officinalis (Mollusca: Cephalopoda)

A culture of juvenile Sepia officinalis L. was kept during summer 1985 in the aquaria of the Station Marine, Wimereux, France. During the first four months of juvenile development, oxygen consumption under increasing hypoxia was measured with a closed respirometer. The experiments revealed a high regulatory capacity of juvenile S. officinalis. The critical oxygen concentrations were calculated and their ontogenetical evolution was studied. The critical oxygen concentration increased with increasing development. A linear relationship emerged between the critical oxygen concentration and the logarithm of the wet weight [CO_c (mg O₂ l^-1)=-0.393+0.893×log₁₀(W _w )]. The decreasing regulatory capacity of growing S. officinalis is most probably related to adaptations to a changing ecological environment during development. Another possibility is a physiological change, most probably related to the shift from embryonic to adult hemocyanin.     

Feeding dynamics of Octopus mimus (Mollusca: Cephalopoda) in northern Chile waters

The natural feeding of 485 Octopus mimus (164 to 3088 g) was studied in relation to the species' life cycle and environmental seasonal variations off the north of Chile from autumn 1991 to summer 1992. Analysis of digestive-tract contents revealed that O. mimus preyed upon 25 different prey items belonging to five zoological groups (Teleostei, Mollusca, Crustacea, Echinodermata and Polychaeta). Cannibalism was only occasional. The results indicate that the diet and food intake of this species are significantly affected by sex and maturation. Senescent individuals ingest a small amount of food, and their diet is mainly based on small, not very motile prey. The food intake, expressed as body weight, of non-senescent individuals is higher in females than in males. Seasonal changes in sea-water temperature seem to be followed by adjustments in food intake. Like other Octopus species, O. mimus appears to be an opportunistic predator.