Sepiolinae (Mollusca, Cephalopoda) from the Ligurian Sea

A collection of 130 specimens of Sepiola (ligulata, robusta, rondeletii, intermedia), 115 Rondeletiola minor, 90 Sepietta ( obscura, neglecta) and more abundant samples of S. oweniana obtained by trawl fishing in the Ligurian Sea are briefly illustrated in terms of depth distribution, sex ratio and maturity stages

La reproducción de la cigala (Nephrops norvegicus, Crustacea Decapoda Nephropidae) en diferentes zonas del Mediterráneo

The main aspects of reproduction - namely times of ovarian maturation, brooding and hatching, sizes of maturation and fecundity - were studied in female Norway lobsters in seven areas of the Mediterranean biogeographic subprovince: the Algarve Sea, the Alboran Sea, the Catalan Sea, the Ligurian Sea, the Northern Tyrrhenian Sea, the Adriatic Sea and the Gulf of Euboikos. These included both shelf and slope populations within a latitudinal range of 8°. The reproduction showed clear seasonality with some small differences between areas: maturation delayed by 1-2 months in northern areas (Ligurian, N. Tyrrhenian and Adriatic Seas) compared to southern areas; absence of embryos for periods of 4-5 months in slope females and for less clearly defined periods in shelf females. The case study of the Ligurian Sea was used to illustrate the ovarian cycle and to describe the pre- and post-puberal growth of the female. First mating occurs at an average size of 32 mm CL, which corresponds to age 3+ of the female and the hatching of the first brood corresponds to age 4. Differences were registered in reproductive sizes in the study areas, with a range of 23-30 mm CL for the smallest berried females and a range of 30-36 mm CL in the 50% maturity size. These differences were ascribed to local factors, whereas ages of the basic steps of reproduction were assumed to be unchanged. Females of age 2 formed the most abundant share of the fished stock. An estimate of fecundity was made in terms of brood size (embryos were counted at an early stage of development): the range was 1119-1834 embryos in a standard female of 35 mm CL. Reproductive potential, calculated on the basis of a virtual population analysis, was strongly influenced by the size structure of the female population in each area and there was a ratio of about 14:1 between the least (Ligurian) and the most exploited (Catalan) fishing grounds.En siete áreas de la subprovincia biogeográfica Mediterránea: costas de Algarve, Alborán, mar Catalán, mar Ligur, norte del Tirreno, Adriático y golfo de Euboikos, se estudian los principales aspectos de la reproducción (período de maduración ovárica, incubación y eclosión, talla de primera maduración y fecundidad) de la cigala. Las poblaciones estudiadas proceden tanto de la plataforma como del talud continental abarcando un rango latitudinal de 8º. La reproducción muestra una clara estacionalidad con pequeñas diferencias entre áreas: la maduración puede presentarse retrasada en 1–2 meses en las áreas más septentrionales (Liguria, Tyrrheno y Adriático), respecto a las áreas más meridonales; ausencia de embriones durante 4-5 meses en hembras del talud y períodods menos claramente definidos en las hembras de la plataforma. Se presenta como ejemplo el caso concreto del mar Ligur con el fin de ilustrar el ciclo gonadal y describir el crecimiento pre y post pubertal de las hembras. La primera cópula ocurre alrededor de los 32 mm CL, lo que corresponde a una edad de 3+ años, mientras que la primera eclosión de los huevos corresponderá a los 4 años. También se observaron diferencias en las tallas reproductivas de las hembras entre las distintas zonas, desde un rango de entre 23 y 30 mm CL para las hembras ovadas más pequeñas, hasta un rango de entre 30-36 mm CL, para las hembras en la talla del 50% de madurez. Estas diferencias se atribuyen a factores locales asumiendo que el patrón reproductor básico es el mismo. Las hembras de edad 2 constituyen la mayor parte del stock pescado. La estimación de la fecundidad se establece en base al tamaño de la puesta (embriones contados en los primeros estados de desarrollo). Para hembras estándar de 35 mm de CL, se estimaron un número de huevos entre 1119 y 1834. El potencial reproductor se calculó en base al análisis de la población virtual y fue estrechamente influenciado por la estructura de tallas de la población de hembras en cada área. La máxima diferencia encontrada, con una proporción de 14:1, fue entre Liguria y Cataluña, esta última como zona más explotada

Pasiphaeid shrimps in the western Mediterranean:geographical variability in distribution and population pattern

Summary: This work aimed to analyse the main characteristics of the bathymetric and geographic distribution, population size structure and size at maturity of the continental slope caridean shrimps Pasiphaea sivado and Pasiphaea multidentata in the western Mediterranean, as well as to try to relate the patterns obtained with geomorphologic and hydrographic characteristics. The study area encompassed the Mediterranean coast of the Iberian Peninsula. In both species, marked differences in depth distribution, density, and population size structure were found between Algerian basin populations, particularly in the Alboran Sea, and those in the Catalano-Balearic basin. Both shrimps showed a shallower bathymetric range in the westernmost region of the Algerian basin than in the rest of geographic sectors, linked to the occurrence of upwelling areas on the northwestern edges of the Alboran Sea. Populations of P. sivado reached larger densities, sizes and maturity size in the Algerian basin. No recruitment of P. multidentata was detected in the Algerian basin, whereas it was present in the Catalano-Balearic basin. In both species, the window range of bottom temperature and salinity was larger in juveniles than in adults. These different distribution and population dynamics imply that ecological functioning of these species differs between the two eomorphological basins of the western Mediterranean Sea.Versión del edito

MEDITS-based information on the deep water red shrimps Aristaeomorpha foliacea and Aristeus antennatus (Crustacea: Decapoda: Aristeidae)

Special Volume: Mediterranean marine demersal resources: the Medits international trawl survey (1994-1999)The application of statistical models on a time series of data arising from the MEDITS International Trawl Survey, an experimental demersal resources survey carried out during six years (1994-1999) in the same season of the year (late spring - early summer) using the same fishing gear in a large part of the Mediterranean, has allowed for a study to compare, for the first time, the space-time distribution, abundance, and size structure of the two Aristeids Aristaeomorpha foliacea and Aristeus antennatus throughout most of the Mediterranean Sea. This research has shown a large variability among the six reference areas, that were arbitrarily defined within the basin. In particular the two shrimps do not seem to present any correlation or yield continuity in the years. The same lack of homogeneity was also observed in the time trend of the abundances and frequencies of each of the two species. These data seem to confirm the intrinsic variability of the species, the cause of which is still unknown and undocumented. Nevertheless, a longitudinal gradient of catches has been observed where A. antennatus is more abundant in the west and A. foliacea in the east of the basinVersión del editor1,006

Increment at molt for the Norway lobster (Nephrops norvegicus) from the south coast of Portugal

The increment at molt for Nephrops norvegicus was studied with the objective of obtaining a model for prediction of post-molt size based on pre-molt size for the population from the south coast of Portugal. Wild animals were maintained in a specially prepared laboratory facility until they malted. Individual values of increment at molt were obtained and used to evaluate alternative models and estimate their parameters. Six alternative models, used previously by several authors to relate pre- and post-molt size, were modified so that increment at molt was the dependent variable and pre-molt size the independent variable. These included the linear relationship of the growth factor (GF) on pre-molt size, the Hiatt equation, post-molt size a power function of pre-molt size, the hyperbolic function, GF exponential function of pre-molt size and the Misra equation. The analysis of the data showed that none of the models could be used to predict increment at molt for either sex. The distribution of the increment at molt was a random normal variable, with mean values not significantly different between sexes, 2.78 mm for males and 2.26 mm for females, variances 0.47 and 0.59, respectively. An analysis of the models suggests that using post-molt size or the GF as dependent variables may lead to a misinterpretation of the dependency of these variables on pre-molt size. It is suggested that the increment at molt should be the variable of interest for predicting post-molt size. The choice of a mathematical formulation should, besides having biological meaning, have the capacity of expressing a true relationship between increment at molt and pre-molt carapace length, namely, be able to model several options for the increment at molt after maturity, including a steady increase of the increment through life, the stabilization of the increment after maturity or the decrease of the increment for larger sizes. (C) 2003 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.info:eu-repo/semantics/publishedVersio

Reproduction in Heteroteuthis dispar (Rüppell, 1844) (Mollusca: Cephalopoda): a sepiolid reproductive adaptation to an oceanic lifestyle

Small cephalopods of the genus Heteroteuthis are the most pelagic members in the family Sepiolidae. This study examines the reproductive biology of Heteroteuthis dispar (Rüppell, 1844), the first such study on any member of the genus, based on 46 specimens (27 females and 19 males) collected during the Mar-Eco cruise in the North Atlantic in the region of the Mid-Atlantic Ridge in 2004, and compares it with reproductive features in the less pelagic members of the family. The unusually large spermatophores of the males have a very small ejaculatory apparatus and cement body, relative to the size of the sperm mass. Females first mate when they are still maturing: a large sperm mass (up to 3.4% of the female body mass), consisting of one to several spermatangia, was found in an internal seminal receptacle of the majority of the females examined regardless of their maturity state. The seminal receptacle has a unique form and position in this species. The receptacle is a thin-walled sac at the posterior end of the visceral mass that is an outpocketing of, and opens into, the visceropericardial coelom. Spermatangia and sperm from the spermatangia apparently enter into the visceropericardial coelom (which is mostly occupied by the ovary) from the seminal receptacle indicating that ova are fertilised internally, a strategy unknown for decapodiform cephalopods (squid and cuttlefish), but present in most octopods. Fecundity of Heteroteuthis dispar (1,100–1,300 oocytes) is much higher than in other sepiolids whereas the egg size (mean max. length ∼1.6 mm) is the smallest within the family. Spawning is continuous (sensu Rocha et al. in Biol Rev 76:291–304, 2001). These and other reproductive traits are discussed as being adaptations to an oceanic lifestyle