Genetic diversification and life-cycle of the polychaete Capitella spp. from the English Channel: evidence for sympatric cryptic species and alternative reproductive strategies

The distinguishing features of the common squid of British waters, Loligo forbesi, are summarized, and contrasted with those of L. vulgaris. The life-cycle and growth of L. forbesi are described, based on samples from trawl catches off Plymouth. This species seems to be an annual - young squid first appear in the trawl in late May, when their length is about 10 or 11 cm. Subsequent growth is rapid, and the males reach 30 cm and the females 25 cm by November. Spawning takes place mainly in December-January, but may continue into the spring. Neither sex survives beyond a single spawning season. Hatching of the spawn probably takes 30–40 days, and if the young squid taken in the trawl in late May hatched in the early part of the same year, a growth rate of about 25 mm/month would be required. Known growth rates for other species of Loligo are about 20 mm/month, so that indicated for L. forbesi does not seem to be impossibly high. The life-cycle is summarized in Fig. 8. There is also a summer spawning population, which grows to a rather smaller size at maturity, and which also seems to be annual.During the summer L. forbesi ranges throughout the English Channel and southern North Sea, particularly in inshore areas. In October the squid migrate farther offshore and tend to occupy the western part of the Channel.Values for total weight of squid/2 h trawl are given, on a monthly basis, for 1966–9. The largest quantities are usually taken in October and November, the highest single figure being 30.54 kg/2 h trawl, in November 1967.

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Metamorphosis of Pectin Aria Koreni (Annelida: Polychaeta) and Recruitment of an Isolated Population in the English Channel

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s002531540002899x ◽

1996 ◽

Vol 76 (1) ◽

pp. 23-36 ◽

Cited By ~ 4

Author(s):

R. Lambert ◽

C. Retière ◽

Y. Lagadeuc

Keyword(s):

Life Cycle ◽

Survival Rate ◽

Morphological Study ◽

High Survival ◽

Isolated Population ◽

English Channel ◽

High Survival Rate ◽

High Level ◽

First Contact

In the Bay of Seine (English Channel) the polychaete Pectinaria koreni exhibits interannual stability in its abundance, despite its isolated distribution and its bentho-planktonic life cycle. To test the hypothesis of a high level of recruitment related to high survival rate of the post-larvae due to metamorphosis in the water column (transformation of metatrochophore into aulophore), we undertook a study of the morphology and the dynamics of the aulophore stage during May and June 1987. The morphological study snowed that aulophore larvae do not possess all the morphological features needed for benthic life on their first contact with the substratum. Fifteen days are needed to complete this development, and during this time the mortality rate is high. The possible role of this delayed metamorphosis on the transport of aulophore larvae towards sites favourable to adults is also discussed.

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Stock structure of the English Channel common cuttlefish Sepia officinalis (Linnaeus, 1758) during the reproduction period

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315415001162 ◽

2015 ◽

Vol 96 (1) ◽

pp. 167-176 ◽

Cited By ~ 6

Author(s):

Michaël Gras ◽

Georges Safi ◽

Hugo Lebredonchel ◽

Jérôme Quinquis ◽

Éric Foucher ◽

...

Keyword(s):

Life History ◽

Life Cycle ◽

Life History Traits ◽

Age Determination ◽

Fishing Effort ◽

Sepia Officinalis ◽

Size At Maturity ◽

English Channel ◽

Reproduction Season ◽

New Research

Within the English Channel, the common cuttlefish Sepia officinalis is a semelparous species for which a 2-year life cycle was exclusively described in the 1980s. In the 1990s, new research indicated that whilst a 2-year life cycle was still evident for females and the large majority of males, a small proportion of males were actually maturing at only 1 year of age. Since 1980, the interest of French and UK fishers for this resource has increased and it is nowadays one of the most important demersal species of the area and is considered to be fully exploited. From the start of the 20th century, fishing effort and sea surface temperatures have increased in the English Channel and have probably impacted the life history traits of S. officinalis. A 2-year sampling programme was undertaken at French landing sites of the English Channel during the reproduction season in 2010 and 2011 to estimate if the proportion of 1-year-old mature animals has changed. Age determination was carried out by coupling polymodal decomposition and lipofuscin measurement. Size-at-maturity for each year and each sex was estimated by fitting a binomial error GLM. Results highlight that a variable percentage of males and females belonging to the first cohort are mature and that size-at-maturity was lower than that observed in the 1990s. Finally, different parameters, such as temperature and fishing pressure are explored to discuss changes in life history traits suggesting that cuttlefish could be an indicator of the temperature regime shift in the English Channel.

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Life cycle, dynamics and productivity of Crustacea-Amphipoda from the western English Channel. 5. Ampelisca sarsi Chevreux

Journal of Experimental Marine Biology and Ecology ◽

10.1016/0022-0981(89)90091-9 ◽

1989 ◽

Vol 128 (1) ◽

pp. 31-56 ◽

Cited By ~ 26

Author(s):

Jean-Claude Dauvin

Keyword(s):

Life Cycle ◽

English Channel

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Harmozica zangezurica (Gastropoda, Pulmonata, Hygromiidae) - a cryptic species of land molluscs from southern Armenia

Ruthenica, Russian Malacological Journal ◽

10.35885/ruthenica.2022.32(1).1 ◽

2022 ◽

Vol 32 (1) ◽

pp. 1-6

Author(s):

N. V. Gural-Sverlova ◽

R. I. Gural

Keyword(s):

Life Cycle ◽

Cryptic Species ◽

Diagnostic Feature ◽

Similar Species ◽

Additional Material ◽

Reliable Identification ◽

Total Length ◽

The Stability ◽

Land Molluscs

Additional material collected in September 2019 made it possible to clarify the range of conchological variability of Harmozica zangezurica recently described from the Syunik region of Armenia, which largely overlaps with that of Harmozica pisiformis thus rendering impossible the reliable identification of empty shells. At the same time the stability has been proven of a diagnostic feature of H. zangezurica - very long vaginal appendages whose length is approximately equal to the total length of the penis and epiphallus. This character allows reliable distinguishing of H. zangezurica not only from the conchologically similar species H. pisiformis , but also from other representatives of the genus Harmozica . Some data on the ecology and life cycle of H. zangezurica were obtained.

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Ultrastructural analysis of “Sensory” surface nerve endings and “putative” neurotransmitter sites in Schistosoma mansoni Miracidia

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156791 ◽

1989 ◽

Vol 47 ◽

pp. 962-963

Author(s):

Betty Ruth Jones ◽

Steve Chi-Tang Pan

Keyword(s):

Nervous System ◽

Life Cycle ◽

Schistosoma Mansoni ◽

Snail Host ◽

Complex Life Cycle ◽

Rational Approach ◽

Effective Control ◽

The Social ◽

Social And Economic Development ◽

Basic Biology

INTRODUCTION: Schistosomiasis has been described as “one of the most devastating diseases of mankind, second only to malaria in its deleterious effects on the social and economic development of populations in many warm areas of the world.” The disease is worldwide and is probably spreading faster and becoming more intense than the overall research efforts designed to provide the basis for countering it. Moreover, there are indications that the development of water resources and the demands for increasing cultivation and food in developing countries may prevent adequate control of the disease and thus the number of infections are increasing.Our knowledge of the basic biology of the parasites causing the disease is far from adequate. Such knowledge is essential if we are to develop a rational approach to the effective control of human schistosomiasis. The miracidium is the first infective stage in the complex life cycle of schistosomes. The future of the entire life cycle depends on the capacity and ability of this organism to locate and enter a suitable snail host for further development, Little is known about the nervous system of the miracidium of Schistosoma mansoni and of other trematodes. Studies indicate that miracidia contain a well developed and complex nervous system that may aid the larvae in locating and entering a susceptible snail host (Wilson, 1970; Brooker, 1972; Chernin, 1974; Pan, 1980; Mehlhorn, 1988; and Jones, 1987-1988).

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