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The harmful dinoflagellate, Heterocapsa circularisquama, has been causing mass mortalities of bivalve molluscs in Japan, at relatively low cell densities. Although several studies have been conducted to determine the toxicity mechanisms, the specific cause of death is still unclear. In a previous study, in our laboratory, it was shown that H. circularisquama (10(3) cells ml(-1)) caused extensive cytotoxicity in the gills of short-neck clams, Ruditapes philippinarum. In the present study, Mediterranean mussels, Mytilus galloprovincialis, were exposed to H. circularisquama at four cell densities (5, 50, 500, 10(3) cells ml(-1)), three temperatures (15, 20, and 25°C), and three exposure durations (3, 24, and 48 h), and the pathologies in nine organs (gills, labial palps, mantle, hepatopancreas, stomach, intestines, exhalant siphon, adductor muscles, and foot) were assessed. Foot, adductor muscles, and exhalent siphons of mussels were not affected; however, 16 inflammatory (hemocytic infiltration and aggregation, diapedesis, hyperplasia, hypertrophy, edema, melanization, and firbrosis) and degenerative (thrombus, thrombosed edema, cilia matting and exfoliation, epithelial desquamation, atrophy, and necrosis) pathologies were identified in the gills, labial palps, mantle, hepatopancreas, stomach, and intestines. The total prevalence and total intensity of pathology in each individual mussel, and the prevalence and intensity of pathology in each organ increased significantly with increased cell density, exposure duration, and temperature. The prevalence of pathology was the highest in gills, followed by the prevalence in labial palps, mantle, stomach, and intestines. Pathology was least prevalent in the hepatopancreas. The intensity of pathology was the highest in the gills, followed by the labial palps and mantle, the stomach and intestines, and the hepatopancreas. This detailed quantitative histopathological study demonstrates that exposure to H. circularisquama induces a broad cytotoxic effect in six vital organs, even at low density (5 cells ml(-1)) and low temperature (15°C), but not in muscular organs. Combining cell density, time, and duration of exposure, the organ most affected by the harmful alga was the gill, followed by the labial palps and mantle, the stomach and intestines, and the hepatopancreas. The results of this pathological analysis show that exposure to H. ciruclarisquama severely affects the gills, the labial palps, and mantle thereby interfering with particle clearance and sorting, cleansing, and respiration, but also affects the stomach, intestines, and hepatopancreas, altering the digestive processes and possibly detoxification pathways, if mussels are able to detoxify the toxins of H. circularisquama. In the most severe cases, bivalves would most likely have died as a result of combined severe alterations of the vital functions, failure of tissue repair, and moderate to heavy hemorrhaging in both the external organs and the digestive organs concomitantly with light to moderate alterations in the detoxifying processes.

東京海洋大学名誉教授

Blooms of the toxic dinoflagellate Heterocapsa circularisquama cause massive bivalve kills in Japan. Mariculture of the Japanese pearl oyster, Pinctada fucata martensii, is the industry most affected by these blooms, especially in Ago Bay, Mie Prefecture, where they are frequent, cause mass mortality of oysters, and overlap with their spawning season. The goal of this August 2009 study was to assess the effects of a toxic strain of H. circularisquama isolated from Ago Bay on gametes, fertilization, and embryo development of pearl oysters. Spermatozoa, eggs, spermatozoa and eggs, and fertilized eggs of pearl oysters from Ago Bay were exposed to H. circularisquama at cell densities reported during the bloom (10–104 cells mL−1) for different periods of time. The concentration of H. circularisquama, exposure duration, and their interactions all had significant effects on gamete quality, fertilization, and embryo development. The motility and swimming velocity of spermatozoa, egg viability, fertilization, and embryo development rate were significantly reduced in all concentrations, with a cell density of 10 cells mL−1 determined to be the critical density of H. circularisquama for deleterious effects. This is the first evidence of inimical effects of an HAB species on bivalve spermatozoa upon direct exposure. Further field and laboratory studies are required to investigate the potential effects of H. circularisquama blooms on the reproduction and recruitment of Japanese pearl oysters and other bivalves.

In a laboratory study, we investigated the clearance rates (CRs), respiration rates (RRs), total hemocyte count (THC), pathological alterations, and mucocyte densities in the gills of the short-neck clam Ruditapes philippinarum when exposed to the toxic dinoflagellate Heterocapsa circularisquama. Within 2 h of exposure to H. circularisquama at a concentration of 5–103 cells/mL, both the CRs and the RRs were significantly decreased by 43–52% compared with the control CRs and 43–93% compared with the control RRs, respectively (ANOVA, Newman-Keuls, P < 0.05). Clams exposed to H. circularisquama at 103 cells/mL for 96 h showed a set of defensive and degenerative pathologies that were absent in control clams. Within 3 h, the gills exhibited cilia matting, followed within 24 h by heavy hemocytic infiltration in the connective tissue of plicae, distortion of filaments, hyperplasia, and fusion of adjacent filaments with matted cilia. Within 48 h, the gill plicae became contracted and showed multifocal ep...

We examined the feeding behavior and energy consumption of Octopus ocellatus preying on short-neck clams under experimental conditions. Observed feeding patterns of individual octopuses of 7.0–52.1 g in wet weight were classified as “pulling”, “pulling–drilling–pulling” or variations of pulling and drilling. Octopuses used pulling for clams with shell lengths (SL) of 0.9–2.9 cm and a combination of pulling and drilling for clams with SL of 0.8–3.6 cm. Pulling alone resulted in a mean time for opening a clam (handling time) of 3.1 min and energy consumption of 8.0 μgO 2 g − 1 . Pulling plus drilling involved longer handling times. Prior to drilling, octopuses showed one of two pulling strategies, “low-energy pulling” or “high-energy pulling”. The latter was more similar to the type of pulling behavior seen when drilling was not used. The high-energy strategy resulted in a mean handling time of 55.4 min and an energy cost of 78.9 μgO 2 g − 1 . Low-energy pulling plus drilling resulted in a shorter handling time (29.5 min) and a lower energy cost (26.4 μgO 2 g − 1 ). We calculated the profitability (yield of energy gain per unit handling time) and energy efficiency (yield of energy gain per unit energy cost) of these feeding strategies. Pulling alone was the most efficient method in terms of profitability, whereas low-energy pulling plus drilling was the most efficient in terms of energy expenditure for young octopuses eating clams.

The effects of the toxic dinoflagellate Heterocapsa circularisquama on the activity rate, development rate, prevalence of damage, and survival rate of trochophore and D-shaped larvae of the pearl oyster Pinctada fucata martensii were studied in relation to H. circularisquama cell densities and exposure duration. In addition, larvae were regularly processed via scanning electron microscopy to investigate morphological damage. The activity rate of both larval stages was significantly decreased after 3–6 h of exposure to H. circularisquama at densities ranging from 100 to 2 × 104 cells/mL. The prevalence of damage was significantly high after 3–6 h of exposure to H. circularisquama at densities of 100 to 2 × 104 cells/mL and 5 × 103 to 2 × 104 cells/mL for trochophores and D-shaped larvae, respectively. Cytoplasmic discharge, mass mucus production, irregular shape, delayed or inhibited mineralization of the shell, mantle protrusion, the appearance of abnormal masses in the velum, and the exfoliation...

To understand the mechanism of the peripheral auditory system of the cephalopod statocyst, the frequency dependence of particle motion sensitivity in cephalopods was estimated using a physical model of the sensory system, which was assumed to be forced oscillation. Reported perception thresholds of Sepia officinalis, Octopus vulgaris, and O. ocellatus fit the model well at low frequencies, whereas at frequencies above 150 Hz, the empirically measured threshold increased more steeply than the predicted increment. These results indicate that the frequency response of the perception threshold of cephalopods to particle motion can be primarily understood using the forced oscillation model, while unknown factor(s) play a role in the higher frequency range. Cephalopods are thought to be sensitive to low-frequency particle motion rather than high-frequency motion. The evolutionary function of cephalopod acoustical perception is not clear; however, the data suggest that they recognize the low-frequency particle motion that may be generated by prey, predators, and conspecifics.

Mortality of the short-neck clam Ruditapes philippinarum exposed to the toxic dinoflagellate Heterocapsa circularisquama was studied under controlled conditions to clarify the mechanisms of recurrent mass deaths of clams occurring in western Japanese coastal areas. One-week mortality tests, involving three water temperatures, six H. circularisquama concentrations, and two clam body sizes, showed a significant increase in mortality with increasing temperature, H. circularisquama concentration, exposure duration, and body size (ANOVA, P

Five tRNA-derived short interspersed repetitive elements (SINEs), named SepiaSINE, Sepioth-SINE1, Sepioth-SINE2A, Sepioth-SINE2B and OegopSINE, were isolated from the genomes of three decabrachian species [Sepia officinalis (order Sepiida), Sepiotheuthis lessoniana (suborder Myopsida), and Mastigoteuthis cordiformes (suborder Oegopsida)], by random sequencing and genome screening. In addition, two tRNA-derived SINEs, named IdioSINE1 and IdioSINE2, were further detected from EST (expressed sequence tag) data of Idiosepius paradoxus (order Idiosepiida), using a GenBank FASTA search with a conserved sequence of the SepiaSINE as the query. All the isolated SINEs had a common and unique highly conserved 149-bp sequence in their central structures (Sepioth-SINE2B and IdioSINEs, however, had a continuous 73-bp deletion in the conserved region.), and are therefore grouped as the fourth SINE superfamily "Ceph-SINEs", following the CORE-SINE, V-SINE, and DeuSINE superfamilies. Our analysis suggested that the central conserved region called the "Ceph-domain" might have originated before the diversification of cephalopods (505 myr ago). A sequence alignment of Sepioth-SINE1, Sepioth-SINE2A, and Sepioth-SINE2B demonstrated that Sepioth-SINE2A has a chimeric structure shared with two other SINEs. The above relationship suggests possible template switching in the central conserved domain during reverse transcription for the birth of Sepioth-SINE2A, providing the possibility that the presence of the conserved domain contributed to yield a variety of SINEs during evolution. Furthermore, the distributions of the isolated SINEs showed that order Sepiida, suborders Oegopsida and Myopsida, and order Idiosepiida have their own independent SINE(s), and suggest that order Sepiida can be largely separated into two groups, with clarification of the phylogenetic relatedness between subfamily Sepioteuthinae and the other loliginid squids.

The effects of the toxic dinoflagellate Heterocapsa circularisquama on the valve movements of adult Ruditapes philippinarum (Bivalvia, Veneridae) were investigated. The valve movement behaviour was continuously measured using a non invasive Hall element sensor-automated data acquisition system. Individual clams acclimated to the experimental conditions were subjected to different food regimes over a 96 h period: (1) unfed in filtered seawater for the first 24 h, (2) batch-fed1, in which clams were given one ration of non-toxic Isochrysis galbana at the beginning of the second 24 h, (3) batch-fed2, in which clams were given a mixture of I. galbana and H. circularisquama (5 × 10 4 cells ml − 1 ) for the third 24 h, and (4) starved for 24 h in filtered seawater after exposure to the toxic alga. For each food regime, the valve activity was analyzed by quantifying: (1) the duration of valve opening (DVO, %), (2) the amplitude of valve opening (AVO, mm), and (3) the frequency of valve adductions (FVA, adductions h − 1 ). The real-time monitoring of the clams' valve movements proved that R. philippinarum detects H. circularisquama in the mixture of food at as low as 0.5 cells ml − 1 . Typically, the addition of the toxic alga induced a short and incomplete valve closure reaction. A strong correlation between the closure reaction time and H. circularisquama concentration was found ( R 2 = 0.91), the closure reaction occurring faster with increasing concentrations. Reopening of the valves was characterized by a significant increase in the FVA starting from 5 cells ml − 1 (ANOVA, P − 1 (Wilcoxon, P − 1 (ANOVA, LSD, P P Our results indicate that the Manila clam is highly sensitive to the toxic H. circularisquama and detects efficiently its presence at extremely low concentrations, in mixture of food, and in a time- and concentration-dependent manner. The Manila clam and the valve movement monitor could thus be used as an early biological warning system to monitor the outbreaks of this toxic alga along marine coastal areas and in bivalve farms. However, field experiments are required to provide further evidence for the use of this monitor in natural environment where several factors may interfere with the valve movement behaviour.

In octopus, growth trajectories have implications for survivorship, adult size and fecun- dity. Many species exhibit a 2-phase growth pattern starting with rapid exponential growth before shifting to a slower (commonly power) growth rate. Based on the concept that energy conservation enforces this threshold, we developed a temperature-dependent model which incorporates the energy balance between food intake and expenditure in growth and metabolism. We employed the model to investigate growth patterns occurring at different temperatures for 2 octopus species, Octo- pus ocellatus and O. pallidus. Model projections were consistent with laboratory data and suggest that increases in temperature as small as 1°C could have a significant influence on cephalopod growth, affecting the threshold body mass by up to 15.5% and the body mass at 100 d by up to 62.6%. Sensitivity analyses suggest that threshold size is more sensitive than threshold age to any given change in parameter values, and that metabolic rate has the greatest influence on the growth thresh- old. This model provides a basis for predicting individual growth trajectories and consequential pop- ulation structure of natural octopus populations. This type of analysis also has the potential to predict optimum conditions for a species and could be a powerful tool for predicting how climate change might affect species distribution as well as population structure and abundance.

The cephalopod receptor of particle motion was identified. In a previous study, it was suggested that statocysts served this function, but there was no direct supporting evidence, and epidermal hair cells had not been conclusively ruled out. Experiments on Octopus ocellatus were conducted using respiratory activity as an indicator of sound perception. Intact animals clearly responded to 141-Hz particle motion at particle accelerations below 1.3 ¥ 10 -3 m/s 2 , and the mean perception threshold at this frequency was approximately 6.0 ¥ 10 -4 m/s 2 . Specimens in which the statoliths had been surgically removed did not show any response for accelerations up to 3.9 ¥ 10 -3 m/s 2 at 141 Hz, which was approximately 16 dB greater than the mean perception threshold at this frequency. Specimens that had undergone a control operation in which the statoliths remained intact showed positive responses at 2.8 ¥ 10 -3 m/s 2 for the same frequency stimulus. This indicates that the statocyst, which is morphologically similar to the inner ear system in fish, is responsible for the observed responses to particle motion in O. ocellatus. This is the first direct evidence that cephalo- pods detect kinetic sound components using statocysts.

Oxygen consumption and ammonia excretion rates of three abalone species, Haliotis discus discus, H. gigantea, H. madaka and their hybrids were measured at 20 °C by incubating for 3 h under dark and light (N = 9–13 for each species and hybrid). Animals were fasted before and during the experiment and measurements were made first under dark followed by light on the next day. The rates increased with the increase in body weight and were higher under light than dark. On average, H. discus discus had higher oxygen consumption (DD; dark = 0.039, light = 0.04 ml/g/h) than H. gigantea (G; D = 0.033, L = 0.036) and H. madaka (M; D = 0.034, L = 0.035); the hybrids had varied patterns with respect to their parental species [DD × M (D = 0.032, L = 0.038); M × DD (D = 0.03, L = 0.038); G × DD (D = 0.035, L = 0.04) and DD × G (D = 0.03, L = 0.034), mother first]. M (0.261, 0.298 μmol/g/h) had the highest ammonia excretion rate while G (0.162; 0.264) and DD (0.229; 0.232) had the lowest under dark and light, respectively. The hybrids had varied patterns in comparison with their parents (DD × M = 0.247, 0.32;M × DD= 0.177, 0.28; DD × G = 0.249, 0.364 and G × DD = 0.116, 0.155). The O/N ratios under both conditions in all species and hybrids indicated that they had carbohydrate dominated metabolism. Results demonstrated physiological variability among the species and hybrids indicating necessity of different strategies for their management and aquaculture.

In this study, we prove that the mass die-offs occurring in conjunction with red adductor disease in pearl oysters are caused by an infection. Our research also reveals the influence of water temperature on the onset of the disease and its progress, and we propose measures that are effective in mitigating harm from the disease. To analyze the effect of water temperature on the onset and progress of the disease, laboratory infection experiments were performed over a range of water temperatures (13 °C–31 °C). The experiments showed that disease onset and progress were highly dependent on water temperature. No outbreak was observed at temperatures below 16 °C, while the adductors of experimentally infected oysters turned red in a short time at temperatures between 19 °C and 31 °C. Our research showed that the cumulative water temperature value for days when water temperature was above 19 °C (AT 19 = Σ( T i ), T i > 19) is an effective numerical indicator for the onset of red adductor disease. We also found that when pearl oysters already infected with red adductor disease at a high rate are kept at water temperatures below 16 °C in the winter for a certain minimum period of time, clinical signs regress, and that this treatment is also effective in delaying relapses of the disease with rising water temperatures in the spring. We determined a numerical indicator for finding the low-temperature index that is most effective in delaying disease onset. This is the low-temperature burden based on the number of days with water temperatures of 16 °C or below and those days' temperatures (LTI 16 = Σ(16 − T i ), T i 16 value, the greater the effectiveness in suppressing the onset of red adductor disease. Hence, appropriate low-water-temperature management in the winter helps prevent the relapse and progress of the disease in the spring and beyond when water temperature rises. Results of this research strongly suggest that the LTI 16 value in wintering fisheries and the cumulative water temperature of the days in spring and beyond when the water temperature is above 19 °C (AT 19 ) make it possible to predict when red adductor disease will break out in pearl oysters, and therefore help efforts to mitigate damage from relapses.

To explore behavioral responses to sound and the detectable frequency range of Octopus ocellatus, responses of the octopus to 120 dB rms sound stimuli of various frequencies were observed. The octopus did not respond at 200-1000 Hz, but clearly responded at 50-150 Hz by showing lengthened respiratory activities. Their respiratory activity was frequently suppressed for more than 5 sec after the sound stimulation, and the longest respiratory suppression reached 55.6 sec, while the mean respiratory activity length without sound stimulation was 1.23 sec. In the case of long-lasting respiratory suppression, they retracted the basal parts of their eyes simultaneously. This suggests that underwater sound may play an important role in the life of the octopus, possibly to detect predators.

Estimated age, hatching date and sexual maturation were investigated for the loliginid squids Loligo duvauceli and L. chinensis, the commercially important neritic species in the Andaman Sea of Thailand. The specimens caught by commercial bottom-trawl in Phang-nga Bay and southern area off Phuket Island were obtained monthly from Phuket fish landing between April and August 2005. Age was estimated based on the counting of statolith increments from a total of 329 individuals of L. duvauceli (ML ranges from 41 to 224 mm) and 116 individuals of L. chinensis (ML ranges from 42 to 186 mm). The estimated age ranged from 41 to 161 and 67 to 158 days old for L. duvauceli and L. chinensis, respectively. The length–weight relationships differed among sexes and the sexual dimorphism was expressed as mature females having a greater body weight than males of the same length. Males showed a wide range of maturity size possibly because of the seasonal change in size at maturity. The results of the back calculation for the hatching date of individuals fell between November 2004 and June 2005 which suggests that L. duvauceli and L. chinensis hatch continuously and recruit to the fishing ground for a relatively short period with a shorter lifespan than expected.

The adoption of an upright posture in abalones is essential to enable them to use their foot, and hence to be able to move and seek shelter, as well as to avoid exposure of soft parts and possible predation. In mass restocking programs for abalone, juveniles are released by divers near the seabed, but without control over their posture when they reach the bottom. Thus, the time to recover the upright posture is an important consideration in abalone restocking programs as the quicker they assume this posture the higher the likelihood of survival. This study reports significant differences in the speed of recovering the upright posture between juveniles of the abalones Haliotis discus discus, H. gigantea and H. madaka and between tests conducted under stagnant and flowing water conditions. Longer times were required for recovery in all species in stagnant than flowing water. On average, juveniles of H. discus discus (17.16 and 10.43 s) and H. gigantea (22.54 and 11.89 s) recovered faster than those of H. madaka (161.13 and 49.02 s) under stagnant and flowing water conditions respectively. These results suggest that different species require different levels of care and that water flow or current at the time of release may affect post-release survival.

The subtraction imaging in confocal microscopy is demonstrated by using two vector beams with radial and azimuthal polarizations. The longitudinal electric component, which appears near the focus of a radially polarized beam under the tight focusing condition and produces a smaller focal spot, is effectively extracted by the subtraction using an azimuthally polarized beam. This subtraction imaging with vector beams provides the improvement of the lateral resolution in confocal microscopy without the degradation due to the excess subtraction.

We proposed a subtraction method using vector beams for resolution enhancement in confocal microscopy. The imaging simulation revealed that the negative side lobe due to the excess subtraction resulted in the degradation of the object image. The subtraction imaging using vector beams demonstrated high spatial resolution with avoiding the negative side lobe. Further resolution enhancement beyond 100 nm was predicted by using a flat-top beam obtained by the combination of beams with radial and azimuthal polarizations and a higher-order transverse mode azimuthally polarized beam without significant negative side lobe.

Restocking of cephalopods originated from the awareness of the depletion of natural resources and a need for conservation from stakeholders, public and private sectors. The concept of cephalopod restocking activities is to produce the cephalopod seeds and then release them back into the habitat where the species occur. The process of seed production comprises the collection of broodstocks from the wild, incubation of egg masses, post-hatching management and releasing the seeds at selected locations. The aquaculture methodology that enhances the hatching rate of the eggs and survival rate of the hatchling must produce high yields for the success of restocking. The neritic species, particularly Sepioteuthis lessoniana, Sepia spp. and Octopus vulgaris have been one key focus for restocking due to its success in previous studies on aquaculture as well as their importance to fisheries. The success of aquaculture restocking, supported by the public sector, has been outstanding in Japan and Thailand with a long historical background. Millions of cephalopod seeds were annually released during the peak activities. Although the biological significance of restocking activities to natural stocks requires further research and evaluation, the activities are considered to have produced a significant social success.

A recent revival in using cephalopods as experimental animals has rekindled interest in their biology and life cycles, information with direct applications also in the rapidly growing ornamental aquarium species trade and in commercial aquaculture production for human consumption. Cephalopods have high rates of growth and food conversion, which for aquaculture translates into short culture cycles, high ratios of production to biomass and high cost-effectiveness. However, at present, only small-scale culture is possible and only for a few species: the cuttlefish Sepia officinalis , the loliginid squid Sepioteuthis lessoniana and the octopuses Octopus maya and O. vulgaris . These four species are the focus of this chapter, the aims of which are as follows: (1) to provide an overview of the culture requirements of cephalopods, (2) to highlight the physical and nutritional requirements at each phase of the life cycle regarded as essential for successful full-scale culture and (3) to identify current limitations and the topics on which further research is required. Knowledge of cephalopod culture methods is advanced, but commercialization is still constrained by the highly selective feeding habits of cephalopods and their requirement for large quantities of high-quality (preferably live) feed, particularly in the early stages of development. Future research should focus on problems related to the consistent production of viable numbers of juveniles, the resolution of which requires a better understanding of nutrition at all phases of the life cycle and better broodstock management, particularly regarding developments in genetic selection, control of reproduction and quality of eggs and offspring.

Post-hatching development of the brain in the oegopsid squid, Todarodes pacificus was described using conventional histological and Cajal's silver impregnation methods. The oegopsid squids spend a specific paralarval period before attaining adult-like juveniles. In the just-hatched paralarvae, the brain lobes (lower and intermediate motor centers) are differentiating only in the ventral part of the brain (subesophageal mass, SBM), and development of the dorsal part of the brain (supraesophageal mass, SPM) shows a heterochronic delay. In the SPM, an arched bundle of axonal tracts (transverse arch, TA) crosses the region over the oral ingrowth. In the early paralarval period, the basal lobes and precommissural lobe (higher motor centers) begin to develop along the TA. A little later, a pair of longitudinal axonal tracts (supraesophageal ladder, SPRL) elongates anteriorly from the TA, and accessory lobes (centers for memory and learning) and superior buccal lobes begin to differentiate along the SPRL. In the mid paralarval period, the lobes of the olfactory center and the peduncle lobe develop well in each optic tract region. In the late paralarvae, all brain lobes become identifiable and the brain shows substantially the same organization as that in the adults. The dorsal-most region of the SPM largely increases in volume with striking growth of the accessory lobes. The SBM elongates in anterior and posterior directions and the rostral end (anterior SBM) separates from the middle SBM. The optic lobes become very large with neuropils arranged in layers. In the juveniles, the neuropils increase in relative volume to the perikaryal layers, and neuronal somata enlarge markedly in some lobes. The retarded development of higher motor centers during paralarval development suggests that the early paralarvae of T. pacificus are not active predators but suspension feeders.

Early ontogeny of the Japanese Common Squid Todarodes pacificus was described for artificially inseminated and collected specimens to present new criteria for developmental stages in relation to its ecological adaptation. For the purpose, details for formation of the following organs and tissues were observed with special attention: cilia on the integument, mouth part, shell sac and stellate ganglia, visceral mass, funnel-collar complex, statocysts, eye parts, and ventral photosensitive vesicles. At the embryonic stage (i.e., pre-hatching), various types of epidermal cilia that seem to work as the embryonic rotation were detected. At the early postembryonic stage (i.e., post-hatching), the epidermal lines were characteristically arranged at the scattered condition on arms, tentacles, head, and funnel. Novel strong muscle fibers were distinct in the base of tentacles and funnel retractor muscles at the early postembryonic stage, which is clearly related to the head withdrawal behavior of the paralarvae. The lip cilia and toothed beak developed at the early postembryonic stage, but disappeared later; these apparatus were considered to be related with a change of unique feeding mode in the paralarval life. Based on such morphological features, four distinct stages, namely, paralarval stage 1, 2, 3, and juvenile stage are proposed. The present observations are discussed in relation to survival strategy at early life of T. pacificus and they are compared with those in other cephalopods.

Summary Development of the oval squid Sepioteuthis lessoniana is marked by a large embryonic size resulting in the most fully developed planktonic hatchlings within loliginids. We analyzed the embryonic development with special reference to the external morphology and the surface ultrastructure with a scanning electron microscope to identify both phylogenetic conservation and diversity of structures in the organogenesis of a loliginid. Developmental states of various cilia, namely the scattered, tuft, and uniform types are described. The ciliature pattern of S. lessoniana is more closely similar to the patterns of other loliginids than to those of sepioids and sepiolids, although characteristic numerous uniform-type cilia exist in the embryos of S. lessoniana. The conserved pattern can be recognized in the organogenesis of S. lessoniana and other loliginids; on the other hand, heterochronic variations are noted, particularly in photosensitive organs and chromatophores. Eye pigmentation does not start at t...

An atlas of the developing brain up to hatching stage is established using conventional histo-logical methods in the oegopsid squid, Todarodes pacificus. The brain originates from placodal thickenings in the ectoderm at the end of epiboly. The neuroblasts composing the placodes ingress in a group and accumulate into ganglia under the proximal surface of the surface epithelium. Four pairs of the ganglia, pedal, palliovisceral, cerebral, and optic, form the brain primordium. These ganglia come into contact with one another, and eventually accumulate into a ring-like cluster (circumesophageal cluster) encircling the oral ingrowth and the inner yolk around the surface of the head. The circumesophageal cluster regionally differentiates into brain lobe anlagen through formation of neuropiles and nerve tracts. The neuropiles form a ladder-like structure with two longitudinal columns situated in the ventrolateral parts of the circumesophageal mass and some axonal tracts bridging the left and right column...

The embryonic development of the central nervous system (CNS) in the oval squid Sepioteuthis lessoniana is described. It has three distinct phases: (1) The ganglionic accumulation phase: Ganglionic cell clusters develop by ingression, migration, and accumulation of neuroblasts. (2) The lobe differentiation phase: Ganglia differentiate into lobes. The phase is identified by the beginning of an axogenesis. During this phase, neuropils are first formed in the suboesophageal mass, then in the basal lobe system, and finally in the inferior frontal lobes and the superior frontal-vertical lobe systems. (3) The neuropil increment phase: After the shape of the lobes reached its typical form, neuropil growth occurs, specifically in the vertical lobe. The paralarval central nervous system (CNS) is characterized by neuronal gigantism of the giant fibers and some suboesophageal commissures and connectives. The neuropil formation in the CNS of S. lessoniana occurs somewhat earlier than in Octopus vulgaris, although the principal developmental plan is quite conservative among the other coleoids investigated. Some phylogenetic aspects are discussed based on the similarities in the morphologic organization of their brains. J. Comp. Neurol. 437:449–475, 2001. © 2001 Wiley-Liss, Inc.

Bioaccumulation of cadmium (Cd) by oval squid, Sepioteuthis lessoniana, the relative contributions of Cd in water and food to bioaccumulation, and the distribution of cadmium among organs were studied. In a bioconcentration test, oval squid was exposed to 0.2 mg Cd/l seawater for 14 days, then was reared in Cd-free seawater for 14 days. After the exposure and elimination periods, the Cd concentrations in the whole body were 3.10 ± 0.18 and 1.90 ± 0.05 μg/g wet weight (ww), respectively. The bioconcentration factor (BCF) was 15.5 after exposure for 14 days. The liver exhibited the highest Cd concentration ( 49.3 μg / g ww), and had the highest proportion of organ Cd content (42.8%) to whole-body burden at the end of the exposure period. In a biomagnification test, oval squid was exposed to 0.12 mg Cd/l seawater for 15 days and was simultaneously fed mummichog, Fundulus heteroclitus, that were simultaneously exposed to the same Cd concentration. For a further eight days the squid was kept in Cd-free seawater and was fed mummichog that were also kept in Cd-free seawater. After the exposure and elimination periods, the Cd concentrations in the whole body were 4.18 ± 0.69 and 2.80 ± 0.44 μg/g ww, respectively. The concentration of whole-body Cd in the oval squid that was derived from water was estimated at 1.86 μg / g ww after calculation of a BCF from the bioconcentration test. The contribution of Cd derived from water to the whole-body Cd burden appeared similar to that of the Cd derived from food. In the biomagnification test, the liver Cd concentration ( 58.8 μg / g ww) and its proportion of the whole-body Cd concentration (40.6%) were the highest among those of all the organs after exposure for 15 days, regardless of the uptake route. Because wild squid seem to be exposed to much lower Cd concentrations in water and are subjected to similar Cd concentrations in their prey, compared with squid of the present study, the main Cd source for squid would appear to be dietary.

Summary Oocyte development in the small penaeid shrimp Metapenaeopsis dalei was studied histologically. Seven stages were distinguished, namely (1) oocytes 10μm in diameter are strongly basophilic and spherical, (2) weakly basophilic ooplasm appears around the germinal vesicle, (3) follicle cells appear, (4) lipid globules appear in the ooplasm, (5) yolk granules start to appear in the ooplasm, (6) the germinal vesicle shrinks and migrates marginally, (7) the follicle cells disappear. This is the first report of a fully matured penaeid oocyte without cortical crypts which release materials forming a jelly coat when the eggs are exposed to seawater. Since ovulated oocytes occur in the same section of the ovary as earlier stages, M. dalei is concluded to be a multiple spawner which has short spawning intervals.

Summary Histological observations were made to reveal the origin of young brooded in the enteron of adult Actinia equina from Japan. A total of 295 specimens were collected from four rocky intertidal areas of Sagami Bay and eastern Suruga Bay, Pacific coast of Japan, during the period from February 1994 to January 1995. In the enteron of adults, regardless of sex, 910 young individuals were found. Among them, blastulae with a structure resembling a syncytial blastoderm were found. Development of blastulae to young with tentacles was inferred. Early embryos were observed in both sexes all year round, although the spawning season of A. equina from Japan was restricted to early summer. This observation suggests that early embryos observed during the non-spawning season are produced asexually. Somatic embryogenesis is suggested as the mode of asexual reproduction of A. equina from Japan because of the existence of blastulae in the enteron of anemones in both sexes.

Batissaviolacea Lamarck (l806) locally known as “cabibi” is considered endemic in Cagayan River at Lallo, Philippines and the most expensive freshwater bivalve in the region. This study described through monthly histological examination the cytological characteristics of gametogenesis and sexual dimorphism of the gonad of B. violacea collected from the wild, and determined spawning response using serotonin. Eight category sizes of the species were established, and 10 samples from each size were processed. Gonads were preserved, and subjected for histological processes to confirm gametogenesis. Using descriptive data analysis, confirmation of the identified mature stage at 31-35 mm was further tested through induction of serotonin. Results showed progressive stages of sperm formation in male follicles. Follicles could be seen in clusters and identified as to their sizes from spermatogonia, spermatocytes, spermatids and spermatozoa. Growing female follicles appeared attached to a cytoplasmic stalk in different sizes and shapes. Initially male germ cells appeared tiny and became concentrated at the lumen in radiating bands as they become mature. Likewise, mature oocytes with enlarged nucleus and tiny nucleolus fill the center of the lumen of the female gonad was observed. B. violacea successfully spawn using either 0.2 ml or 0.5 ml earlier (0.21 hour) compared to 36.70 hour when no injection was administered. This is a first time report in the country along the possibility of breeding the species in captivity.Keywords: Aquatic ecology, Batissa violacea, gametogenesis, Cagayan River, induced spawning,experimental design, Cagayan river

We determined the complete mitochondrial (mt) genomes of the deep-sea squid (Bathyteuthis abyssicola; supperfamily Bathyteuthoidea), the bob-tail squid (Semirossia patagonica; order Sepiolida) and four giant cuttlefish (Sepia apama, S. latimanus, S. lycidas and S. pharaonis; order Sepiida). The unique structures of the mt genomes of Bathyteuthis and Semirossia provide new information about the evolution of decapodiform mt genomes. We show that the mt genome of B. abyssicola, like those of other oegopsids studied so far, has two long duplicated regions that include seven genes (COX1-3, ATP6 and ATP8, tRNA(Asn), and either ND2 or ND3) and that one of the duplicated COX3 genes has lost its function. The mt genome of S. patagonica is unlike any other decapodiforms and, like Nautilus, its ATP6 and ATP8 genes are not adjacent to each other. The four giant cuttlefish have identical mt gene order to other cuttlefish determined to date. Molecular phylogenetic analyses using maximum likelihood and Bayesian methods suggest that traditional order Sepioidea (Sepiolida+Sepiida) is paraphyletic and Sepia (cuttlefish) has the sister-relationship with all other decapodiforms. Taking both the phylogenetic analyses and the mt gene order analyses into account, it is likely that the octopus-type mt genome is an ancestral state and that it had maintained from at least the Cephalopoda ancestor to the common ancestor of Oegopsida, Myopsida and Sepiolida.

Abalones are one of the most important coastal animal resources in Japan, and the study of their seed culture has a long history of more than 40 years. Most of the produced seeds have been released to the seabeds. The total number released nowadays is almost 3 million (small individuals) per year. However, the annual production of natural abalones has decreased remarkably in the last 10 years.

Oxygen consumption rates of the young oval squid Sepioteuthis lessoniana (0.033-27.54g BW) reared from eggs and those captured from wild population were investigated on an individual basis by both water bottle and flow-through methods. Oxygen consumption rate (R in ml oxygen/ind./h) increased linearly with increase in BW (W in g) expressed as R=aWb. For squid smaller than about 2g BW, there was not a significant difference in the values of the exponent b and the coef-ficient a between R's measured respectively by water bottle and flow-through methods. The R was not significantly different from each other between squid reared from eggs and captured from the sea. The exponent b and coefficient a for young squids ranged from 0.741 to 0.944 and from 0.697 to 0.966, respectively. There was a tendency for the exponent to change with growth, such as b for the squids less than 0.5g BW being 0.944, while for the squids over 0.5g was 0.813, respec-tively. This suggests that R in very early life stage tends to increase more rapidly with growth than in older stages.

Oxygen consumption and ammonia excretion were investigated during a long term starvation in an abalone Sulculus diversicolor aquatilis. Abalone used in the present study were 14 specimens ranged from 0.14 to 17.10g in wet weight of soft body (W, g). They were kept starved in a closed aquarium at 24°C. Oxygen consumption and ammonia excretion rates were measured by individual in a closed bottle with several days interval until death by starvation. Oxygen consumption rate (R, μl O2/ind./h) of the abalone increased linearly with an increase in W and decreased with the period of starvation (T, days); R=92.019 W0.914 0.987T. Ammonia excretion rate (E, μmol/ind./h) increased linearly with an increase in W. Until the 17th day from commencement of the experiment E increased with an extention in T, however, it decreased with extention of T after the 17th day and they are expressed as E=0.369 W0.78 T0.413 and E=2.151 W1.012 T-0.454, respectively. The O/N ratios for abalones just after feeding were relatively high and indicate an apparent dependence upon carbohydrates in the feeding period. After about 2 weeks starvation, the O/N ratios showed relatively low and constant, followed by standard protein energy utilization thereafter.

Food consumption, food conversion and growth rates of the oval squid Sepioteuthis lessoniana were measured on an individaul basis fed on three kinds of live organisms, namely, fish, mysid and squid hatchling. Squid used in the present study were all reared from egg to the experimental size, ranged from 0.06 to 42.1g in wet body weight in an indoor aquarium. The daily food con-sumption rate ranged from 0 to 72% of body weight and depended upon the growth stage of the squid. Food conversion rate on a wet weight basis ranged from 15.4 to 43.8% and the rate was largely independent of the size of squid. Growth rate of the oval squid decreased with increasing size. The daily growth rate in body weight of hatchling reached 12.9% and that of the squid grown up to 30-50g in body weight ranged from 1.8 to 4.1%. The growth was dependent upon quality of food. Squid fed on squid hatchlings showed the highest growth rate followed by those fed on fish. The daily growth rate increased with each increment of the daily food consumption rate.

In the 1980s, there still had been the argument whether cephalopods could detect sound stimulus or not. The ability of sound detecting (hearing ability or an ability to detect vibration) in cephalopods was proved around 1990, however, there have been few studies about sound detection in cephalopods afterwards. Based on morphological and behavioral studies, it seems that cephalopods do not perceive sound pressure. Provided that compressional waves do not stimulate the nervous systems of the animals, they do response to sound waves due to water particle movement. In this study, the ability to detect sound waves in cephalopods was investigated from the standpoint of water particle movement perception. An object would be well vibrated by sound waves when the length of the object is much smaller relative to the wavelength; consequently, when an animal detects water particle movement, the smaller the animal is, the higher frequency and weaker stimulus it would detect.

Oxygen consumption and ammonia excretion rates were investigated in young Octopus maya (hatching to 139 days old; 0.11–81.23 g wet body weight, BW; 22.5–23.9°C), young squids of Loligo forbesi (hatching to 45 days old; 9.4–115.3 mg BW; 12.3–13.1°C) and young squids of Lolliguncula brevis (2.00–39.98 g BW; 23.8–24.7°C). Except at hatching, oxygen consumption and ammonia excretion rates on an individual basis (M) of these three cephalopods increased linearly with increasing body weight (BW) expressed as M = aBWb . Values of b for oxygen consumption were 0.900, 0.910 and 0.848 and for ammonia excretion were 0.744, 0.809 and 0.751 for O. maya, L. forbesi and L. brevis, respectively. Among the three species the value a varied widely, while b was similar for both oxygen consumption and ammonia excretion rates. Based upon these data, metabolism for hatchlings of O. maya and L. forbesi was estimated to be relatively lower than that of older juveniles. The O/N ratios for hatchlings of O. maya and L. forbesi were r...

Experiments on moult frequency, growth, filtering and ingestion rates, and size selection of food particles were conducted in the Antarctic krill, Euphausia superba. The intermoult period ranged from 14 to 28 days, with a slight tendency that it was longer for larger specimens than for smaller ones. The dry weight proportion of the exuvium to the body varied between 4.7 and 14.1%. Carbon and nitrogen contents in the exuviae were 10.50±3.22 and 1.84±0.69% of the dry weight, respectively. During the rearing experiments, some krill clearly showed an increase in body length, but some showed a decrease. The most rapid growth is expressed by the regression equation y=0.0116x+5.88 (y : carapace length in mm, x : time in days). Growth rate expressed as an increase in body length per month was 4.5% for krill of 25mm in length. The filtering rate increased with the increase in body dry weight, while the filtering rate per unit dry weight decreased. The filtering rates at high phytoplankton concentrations were much higher than at low concentrations. Krill ingested phytoplankton by active filter feeding when it was plentiful. If phytoplankton was scarce, the filter feeding became inactive. In this case, krill cannot compensate for their metabolic loss and thus depend on predatory feeding. Krill ingested food particles larger than 8μm through their filter feeding when the particles were composed of various sizes, but they can also take minute particles less than 8μm when the majority of particles in medium were smaller than 8μm.

The enhanced spatial resolution in confocal laser microscopy is demonstrated by subtracting two confocal images acquired by radially and azimuthally polarized beams. The effect of the side-lobe emerging in the subtraction processes is also discussed.