Statolith microstructure and age of early life stages of planktonic squids Galiteuthis phyllura and Belonella borealis (Oegopsida, Cranchiidae) from the northern North Pacific

Statolith morphology and microstructure were studied in two common species of panktonic cranchiid squids, Belonella borealis [four juveniles with mantle length (ML) 375–450 mm] and Galiteuthis phyllura (13 paralarvae and juveniles, ML 9–235mm), caught near the bottom and in pelagic layers over the continental slope of Siberia in the northwest Bering Sea. The total number of growth increments within the statoliths ranged from 277 to 294 in B.borealis and from 10 to 209 in G.phyllura. Assuming that these increments were produced daily, both species grow rapidly in length (daily growth rate = 1.13mm day−1 during the first 8–10 months of their juvenile phase in the mesopelagic layers, prior to migration into deeper waters for maturation

Reproductive System Structure, Development and Function in Cephalopods with a New General Scale for Maturity Stages

The main types of reproductive system structure, development and functions in cephalopods are described from personal observations and use of the literature. There is one type in males and three in females which are order specific. These have provided a basis for examining possible evolutionary trends in reproductive system development and in reproductive strategies within coleoid cephalopods and for developing a general scale for maturity staging for males and females. Development of the cephalopod reproductive system consists of two main phases. The first includes sexual cell differentiation, growth and maturation (i.e. juvenile phase and physiological maturation). The second begins after maturation of sexual cells. It includes their transport and accumulation in different parts of the reproductive system and their conversion into spermatophores in males and eggs with protective coverings in females (i.e. physiological maturity, functional maturation and maturity). It was found that species with different life styles within each order have similar reproductive systems. This may be attributable to the relative youth in an evolutionary sense of the main groups of living cephalopods. A general scale of seven maturity stages for cephalopods was developed. Distinct characteristics of each stage are described and supplemented with a generalized drawing of gonad structure. In the first phase of reproductive system development, maturity stages are distinguished by the degree of development of the gonad and accessory glands. In the second phase maturity stages are distinguished by the fate of the mature sexual cells, particularly by their transport and location in different parts of the reproductive system up to the time of spawnin

Effective unidirectional pumping for steady-state amplification without inversion

We discuss an opportunity to achieve amplification without inversion in three-level cascade scheme using an effective unidirectional pumping via bidirectional incoherent pump. Analytical solution to the population and the coherence are obtained in the steady-state regime. With a proper choice of the parameters, obtained here, the possibility for amplification without inversion is presented.Comment: 8 Pages, 7 figure

Using statolith elemental signatures to confirm ontogenetic migrations of the squid Doryteuthis gahi around the Falkland Islands (Southwest Atlantic)

This work was supported by the Falkland Islands Government. We thank Dr. Simon Chenery and the British Geological Survey for assistance with the LA-ICP-MS analysis and training and use of their facilities. We are grateful to the scientific observers from the Falkland Islands Fisheries Department for sample collection. We thank the Director of Fisheries, John Barton, and the director of SAERI, Paul Brickle, for supporting this work. We thank Dr. Elena Ieno, Dr. Andreas Winter, Dr. Haseeb Randhawa and three anonymous reviewers for their helpful comments that greatly improved the manuscript.Peer reviewedPostprin

Links between marine fauna and oceanic fronts on the Patagonian Shelf and Slope

One of the main oceanographic features in the Southwest Atlantic is the transport of cold waters of Sub-Antarctic origin along the Patagonian slope to temperate latitudes (40-42ºS) by the Falkland Current. Originating from the Antarctic Circumpolar Current in the Drake Passage, the Current splits into two main northward streams skirting the Falkland Islands from west and east. The strongest eastern branch meanders onto the shelf to the south of Beauchêne Island and north-east of the Falkland Islands and creates four fronts with strong upwellings of the Sub-Antarctic Surface Water Mass (SASW). Extension of SASW to the shelf break and its mixture with shelf waters creates quasi-stationary areas of high productivity. Sub-Antarctic fishes (e.g., southern blue whiting) utilise these areas as their feeding and spawning grounds. Deepwater toothfish and squid (Onykia ingens) use them as pathways to migrate from the shelf to deepwater habitats. Temperate fish (e.g., hoki and rock cod) and squid (Illex argentinus) feed mainly at the frontal zones with mixture of SASW and Patagonian Shelf waters. The presence of four quasi-stationary meso-scale fronts between the deepwater Falkland Current and shelf waters plays an important role in distribution, migrations and spawning of marine fauna that use them in accordance to their Sub-Antarctic and temperate origins

Age, growth and reproductive biology of diamond-shaped squid Thysanoteuthis rhombus (Oegopsida:Thysanoteuthidae)

Age and growth of the large oceanic squid Thysanoteuthis rhombus were estimated by statolith increment analysis of 72 specimens [mantle length (ML) ranging from 25 to 805 mm] and reproductive biology was studied on 162 T. rhombus (ML 150 to 850 mm) captured in the eastern tropical Atlantic and southwestern Pacific between 1976 and 1990. The maximum ages found in our samples were observed in a mature female of 750 mm ML (305 d) and in a mature male of 770 mm ML (309 d). The life span of T. rhombus was estimated to be about 1 yr; males and females matured at age 6 to 8 mo. T. rhombus is one of the fastest-growing squids: by age 300 d, they reached 750 to 800 mm ML and 17 to 17.5 kg body weight (BW). The increase in both ML and BW during ontogenesis was best fitted by a logistic growth curve. T. rhombus has high potential fecundity (up to 4.8 million oocytes), but a rather small maximum volume of oviducts (up to 140 000 eggs) and egg masses (35 000 to 75 000 eggs). It is suggested that T. rhombus is an intermittent spawner with multiple filling and evacuation of oviducts. The main function of the (for squid) unusual behaviour of T. rhombus, i.e. living in pairs consisting of a male and female, is reproduction and is optimal given the low density of T, rhombus populations and low active movement of squids