Description: Pelagic aquatic environments differ from terrestrial environments in being three-dimensional and relatively homogeneous, rather than two-dimensional and heterogeneous. The present paper examines the causes and consequences of these differences in the context of their influence on the interactions of animals with environmental light. Particular emphasis is placed on light as a determinant of effective modes of crypsis in the two different habitats. The terrestrial world has selected for the expression of crypticity in the form of superficial color patterns. The heterogeneity of this habitat has resulted in evolutionary divergence of these superficial color patterns, often in very closely-related animals. In contrast, in the homogeneous pelagic aquatic habitats, evolutionary convergence on three main forms of crypsis is evident: (1) transparency; (2) reflection of most, if not all visible wavelengths; and, (3) ventral bioluminescence as counterillumination; thus, to be cryptic most animals in these habitats use one or a combination of these modalities to variously transmit, reflect or mimic environmental light. In the present paper, special attention is given to transparency as the most prevalent, yet least understood, of these mechanisms that are used in predator-prey interactions.

Description: Work on the life histories of common antarctic benthic marine invertebrates over the past several decades demands a revision of several widely held paradigms. First, contrary to expectations derived from work on temperate species, there is little or no evidence for temperature adaptation with respect to reproduction (gametogenesis), devel? opment, and growth. It remains to be determined whether the slow rates of these processes reflect some inherent inability to adapt to low temperatures, or are a response to features of the antarctic marine environment not directly related to low temperature, such as low food resources. Secondly, contrary to the widely accepted opinion designated as "Thor- son's rule," pelagic development is common in many groups of shallow-water marine invertebrates. In fact in some groups, such as asteroids, pelagic development is as prevalent in McMurdo Sound, the southern-most open-water marine environment in the world, as in central California. In other taxonomic groups, especially gastropods, there does seem to be a genuine trend toward non-pelagic development from tropical to antarctic latitudes. Although this trend has been predicted by theoretical models, its underlying causes appear to be group specific rather than general. Thirdly, pelagic lecithotrophic development, often considered to be of negligible importance, occurs in many shallow-water antarctic marine macroinvertebrates. Pelagic lecithotrophy may be an adaptation to a combination of poor food conditions in antarctic waters most ofthe year and slow rates of development. Nevertheless, some of the most abundant and widespread antarctic marine invertebrates have pelagic planktotrophic larvae that take very long times to complete development to metamorphosis. These species are particularly prevalent in productive regions of shallow water (〈 30 m), which are frequently disturbed by anchor ice formation, and the production of numerous pelagic planktotrophic larvae may represent a strategy for colonization. Although planktotrophic larvae tend to be seasonal in occurrence, their production is not linked particularly closely to the mid-summer pulse of phytoplankton production. These larvae show no evidence of starvation, even during times when phytoplankton abundance is very low, and they may depend on unusual sources of food, such as bacteria. How they escape the selective conditions that apparently led to a predominance of non-feeding modes of development in antarctic marine invertebrates remains as a major challenge for antarctic marine biology.

Description: A study of individual and group growth rates based on a method of growth determination using the gladius was carried out in two populations of the purple-back flying squid (Sthenoteuthis oualaniesis) in the Arabian Sea. The duration of the life cycle in all populations and size groups examined was approximately one year. The growth pattern of linear increase was either slightly S-shaped or almost linear, while growth in weight followed a power-type pattern. Generally, females grew faster than males. Use of the gladius as a recording structure makes it possible to study the real growth of a specimen, rather than the statistical correlation of length/weight versus age, as in the commonly used statolith method. Analysis of individual growth rates in large-sized sawning females revealed growth rhythm with roughly a one-month periodicity in which phases of rapid growth (17-21 days; 1.6-3,6mm per day) alternate with phases of slow growth (12-14 days; 0.4-1.2mm per day). This new method is simple to use and may be applied even on board a vessel during research cruises.

Description: The microstructure, morphology and ontogenetic development of statoliths and age and growth of 405 planktonic paralarvae and 117 juveniles belonging to 10 species of gonatid squids (Cephalopoda, Oegopsida) were studied in the region of the continental slope in the western part of the Bering Sea (57°00′–61°30′N, 163°00′E–179°20′W). The statolith microstructure of all species was characterized by the presence of a large droplet-shaped nucleus and bipartite postnuclear zone divided into two by the first stress check, except for Berryteuthis magister which had only one stress check and an undivided postnuclear zone. In Gonatus spp., completion of development of the postnuclear zone coincided with full development of the central hook on the tentacular club. Daily periodicity of statolith growth increments was validated by maintaining 13 paralarvae of the four most abundant species in captivity. All species might be subdivided into two groups based on statolith microstructure, i.e. species with a central position of the nucleus within the first statolith check (Gonatopsis spp., Egonatus tinro and B.magister) and species with the nucleus shifted to the inner side of the first statolith check (Gonatus spp.). Comparative analysis of statolith morphology showed that paralarval statoliths have species-specific characters that allowed the construction of keys to identify species of gonatid paralarvae based on their statoliths. Analysis of paralarval growth using statoliths revealed that these cold-water planktonic gonatid paralarvae have fast growth rates, attaining a mantle length of 7–10 mm at 15–20 days and 20–25 mm at 35–70 days.

Description: Statolith microstructure was studied in two abundant planktonic cranchiids, Cranchia scabra (56 specimens, 38-127mm mantle lengh, ML) and Liocranchia reinhardti (34 specimens, 99-205mm ML) sampled in epipelagic waters of the western part of the Gulf of Guinea (tropical Atlantic). Growth increments were revealed in ground statoliths of both species. It was possible to distinguish two growth zones in statolith microstructure by their colour in reflected light of the microscope: the translucent postnuclear zone and pale white opaque zone. Assuming that growth increments in statoliths were produced daily, ages of the largest immature C. scabra and L. reinhardti were 166 and 146 days, respectively. Both cranchiids are fast-growing squids with growth rates in length resembling those of juveniles of tropical ommastrephids and Thysanoteuthis rhombus. Liocranchia reinhardti grows faster: its growth rate in ML is approximately twice that of same-aged C. scabra. The life cycle of both cranchiids consists of two phases. During their epipelagic phase, C. scabra and L. reinhardti feed and grow rapidly from paralarvae to immature young in the epipelagic waters, attaining 120-130 and 170-200 mm ML by ages of 4-5 months, respectively. Then they change their life style to a deepwater phase.

Description: The sexual cycle of the cuttlefish, Sepia officinalis, from the northern part of the Bay of Biscay was followed over several years (1988 to 1990 and 1992 to 1993). Sucessive maturity stages are reached at the same time regardless of site in the northern part of the Bay. In this area, the majority of cuttlefish reproduce during their second year of life (group II) whereas the remainder reproduce in their first year (group I). The first visible signs of sexual development concern the testis in males and the genital tract in females. Males mature earlier than females: the first spermatophores appear in July (group II) and October (group I) while mature eggs appear from December (group II) and March (group I). The breeding season lasts from about mid-March to late June (3.5 months).

Description: An investigation was carried out on the recently discovered ‘giant’ extra large (XL) form of the squid Sthenoteuthis oualaniensis from the Arabian Sea. The sample consisted of 2 males, which have not been previously described, and 13 females. Diet composition, parasite loading, sucker ring dentition, biolumi-nescence and sexual dimorphism were examined and compared to known parameters of the medium (M) form. Reproductive strategy, potential fecundity, egg size distribution in the ovary and oviducts were examined in mature XL females. Evidence of multiple spawning in the giant form was also investigated. Overall body shape, bioluminescent structures and coloration of the giant form were similar to the M form, though the XL form had a smaller fin angle than the M form. The mature female XL form has a dorsal mantle length about twice that of a mature female M form. Adult females of the XL form have a dorsal mantle length about twice that of adult males of the same form. Differences between males and females were found in arm sucker ring dentition and parasite load, suggesting a difference in diet. This could be linked to size differences between the sexes. A strong correlation between ovary mass and mantle length was found (r2 = 0.64). Poor correlation was found between mantle length and oviduct mass (r2 = 0.128) and potential fecundity (r2 = 0.07). Potential fecundity ranged between 2–5 million eggs and the holding capacity of the oviducts was approximately 300, 000 eggs. This combined with the presence of spermatangia and the presence of food in the stomach suggest that the XL form is a multiple spawner. S. oualaniensis appears to have a plastic phenotype and has adapted to the Arabian Sea conditions by evolving the capacity to grow to a giant size.

Description: Age composition and growth rates of the squid Loligo vulgaris (Lamark, 1797) were studied by examination of growth increments within statoliths of 419 specimens (mantle length, ML, ranging from 32 to 400mm). The squid were obtained by monthly sampling from the catches of commercial trawls off southern Portugal between March and September, 1993. The total number of growth increments in the mounted and ground statoliths was counted using a semi-automatic image analysis system. ML was significantly correlated with both the statolith length, TSL and the number of increments, NI. The female statolith was slightly larger than the male statolith for the same mantle size. Growth rates of individuals showed high variability with an average estimated at 34.6mm month-1 for males and 33.5mm month-1 for females. Growth in length between 70 and 280 days was best described by a power function for both sexes. The growth index of the statolith (TSL/NI) decreased with individual growth. The result may be related with the onset of sexual maturation. L. vulgaris hatched throughout the year with two distinct peaks, in spring which is the main breeding period, and in autumn. The life cycle of the L. vulgaris population on the south Portugese shelf was completed in one year.