Population structure and life history of Siriella jaltensis (Malacostraca: Mysida) in the Ebre Delta (NW Mediterranean)
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1
Institut de Recerca de la Biodiversitat. BiologiaEvolutiva, Ecologia i Ciències Ambientals de la U B, Biologia Evolutiva, Ecologia i Ciències Ambientals de la U B, Spain
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2
Ins. Sec. Canet, Ciències de la Naturalesa, Spain
Some aspects of the population and reproductive biology of the mysida Siriella jaltensis Czerniavsky, 1868 were studied in the Alfacs Bay, semi-enclosed estuary placed at the South of the Ebre Delta in the western Mediterranean. The Alfacs bay not only has a high ecological interest, but also economic. It is the most important shellfish farming area in Catalonia (Spain).
It is a very threatened ecosystem by pollution and salinization, and taking into account the effect of climate change in a few years the Delta can be reduced in size due to rising sea levels.
Siriella jaltensis is known from the Mediterranean Sea, Black Sea, Cantabrian Sea, and N-Atlantic Ocean, English Channel and the Seine Estuary, in the Moroccan coast and Madeira Island, in West Pacific and Indian oceans. However, our knowledge about population ecology and reproductive cycle is incomplete. S. jaltensis is very similar to S. clausii, in fact the two species can be found together in many coastal areas at night and in dark submarine caves.
S. jaltensis individuals were collected from Sant Carles de la Ràpita harbour, from June 2010 to March 2012. The sampling was always performed at night, after the sunset (20:00–23:00 hours, according to the season), and the specimens were preserved in 70% ethanol.
The collected individuals were identified to the specific level, and assigned to one of the following six demographic categories on the basis of their sexual and reproductive characteristics: (1) juveniles; (2) immature males; (3) mature males; (4) immature females; (5) mature females; and (6) brooding (incubating) females. The embryos or larvae in each brooding female were counted, measured, and classified according to the following stages: embryonic stage (eggs), nauplioid stage (hatched larva with antennules, antennae and mandibles) and post-nauplioid stage (thoracic appendages fully development and distinct stalked eyes).
S. jaltensis population density showed considerable fluctuations throughout the year with a maximum abundance in summer. The sex-ratio (number of females: number of males) calculated from the complete data set was not significantly different from 1. However, the sex-ratio fluctuated along the sampling period (from 0.25 in April 2011 to 2.0 in September 2011). The mean sizes among the different demographic categories showed marked seasonal variations, with two main individual size types: larger-sized winter individuals and smaller-sized summer individuals, however a third size category can be considerate an intermediate size who appears around the year.
During November - February, the overwintering generation matured and then released juveniles in April, May and June, forming the spring-summer generation. The larger mature females (and mature males) observed in winter; disappear in July-August from the sampled zone. Several cohorts were present simultaneously during the year.
Brooding females were observed throughout the year, except in March 2011, and showed a peak in their percentage respecting the total females in winter. The females are iteroparous, and the majority of mature females carry embryos or larvae throughout the yearly cycle. The brood size (N) was related to the size of the brooding females (range: 1- mean value: 14): N=11 CL -15 (n females =192, r = 0.48, P < 0.01). The volume (V) of the eggs was also related to the size of the females (range: 0.06 mm³, 0.01 mm³, mean value: 0.03mm³,): V=0.01 CL +0.01 (n females =192, r = 0.3 P < 0.001).
In the females of intermediate size range, that are present throughout the year, the major axis of eggs was inversely related to temperature D = - 0.05 T +0.62 (n females = 43, r = 0.5 P < 0.001) (D = major axis). This feature is also reflected in Hemimysis lamornae mediterranea and Mesopodopsis slabberi, who have a presence in Ebre Delta as well.
A possible survival strategy for communities that inhabit shallow waters and the coast, where the mortality rate is higher for juveniles in their early stages, would be to have larger eggs and bigger juveniles in the winter, that would be more resilient.
Keywords:
Malacostraca,
Mysida,
Population Biology,
Reproductive ecology,
Ebre Delta.
Conference:
XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016.
Presentation Type:
Poster Presentation
Topic:
1. ECOLOGY, BIODIVERSITY AND VULNERABLE ECOSYSTEMS
Citation:
Delgado
L,
Ribera
C,
Guerao
G and
Fortuny
C
(2016). Population structure and life history of Siriella jaltensis (Malacostraca: Mysida) in the Ebre Delta (NW Mediterranean).
Front. Mar. Sci.
Conference Abstract:
XIX Iberian Symposium on Marine Biology Studies.
doi: 10.3389/conf.FMARS.2016.05.00140
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Received:
27 Apr 2016;
Published Online:
03 Sep 2016.
*
Correspondence:
Dr. Lídia Delgado, Institut de Recerca de la Biodiversitat. BiologiaEvolutiva, Ecologia i Ciències Ambientals de la U B, Biologia Evolutiva, Ecologia i Ciències Ambientals de la U B, Barcelona, Barcelona, 08028, Spain, lidiadelgadogarcia@gmail.com