Vertical and horizontal larval distribution of an offshore brachyuran crab, <em>Monodaeus couchii</em>, off the south coast of Portugal

Abstract

Summary:A strong understanding of larval distribution and abundance is of major value in delineating the location and size of a breeding population of deep-sea species such as Monodaeus couchii. In this study, vertical distribution of the larvae of a brachyuran crab, M. couchii, was assessed during two week-long cruises conducted at the end of January 2006 and 2007 off the South Coast of Portugal. Larvae were collected by oblique plankton hauls with a Longhurst-Hardy Plankton Recorder from the surface to 300 m. Abundance and distribution of zoeae I and II were correlated during both years. For all stages, abundance decreased with depth during the day while it increased with depth at night; the larvae thus displayed reverse diel vertical migration. Abundance of zoeae I and II was correlated with chlorophyll a levels, whereas those of later stages were correlated with neither physical parameters (chlorophyll a, temperature or salinity) nor each other. An ontogenic shift in vertical distribution explained the results; earlier zoeal stages remain in the food-rich upper water column while later stages were not correlated with any physical parameters (i.e. chlorophyll a, salinity or temperature) and migrated to the bottom for settlement.Keywords: diel vertical migration; crustacean; deep sea; invertebrate larva; vertical distribution; Monodaeus couchii; Iberian Peninsula. Distribución vertical y horizontal de larvas de Monodaeus couchii frente a la costa sur de PortugalResumen: El conocimiento de la distribución y abundancia larval es de vital importancia para comprender la localización y tamaño de la población reproductora adulta en especies abisales como Monodaeus couchii. En este estudio, la distribución vertical de las larvas de un cangrejo braquiuro, M. couchii, se evaluó durante dos campañas de una semana de duración al final de enero de 2006 y 2007, frente a la costa sur de Portugal. Las larvas se recogieron por pescas oblicuas de plancton con un "Longhurst-Hardy Plankton Recorder" (LHPR) desde la superficie hasta 300 m de profundidad. La abundancia y distribución de las zoeas I y II fueron correlacionadas para cada uno de los años de estudio. Para todos los estadios larvares la abundancia disminuyó con la profundidad durante el día, mientras que se incrementó con la profundidad durante la noche, mostrando por tanto un patrón de migración vertical inverso. La abundancia de zoeae I y II se correlacionó con los niveles de clorofila a, mientras que la abundancia de estadios posteriores no mostró correlación alguna con los parámetros físicos (clorofila a, temperatura o salinidad), ni entre sí. Estos resultados indican un cambio ontogénico en la distribución vertical de las larvas; los primeros estadios de zoea permanecen en la zona superficial de la columna de agua rica en alimento, mientras que las ultimas etapas que no mostraron correlación con los parámetros físicos (i.e. clorofila a, salinidad o temperatura) migran a zonas más profundas para el recrutamento.

Sabellariidae from Lizard Island, Great Barrier Reef, including a new species of Lygdamis and notes on external morphology of the median organ

“…Members of Gesaia have been reported from all major oceans and from depths ranging from 770 to 5790 m (Kirtley 1994), but the eight species described to date have each been reported only once or a few times from nearby localities, leading workers to assume that species were allopatric and narrowly distributed. Undoubtedly, the potential for dispersal over long distances is greater when larvae reach shallower waters, due to low speed currents in deep water (Kelly et al 1982;Shanks 1986;Bouchet & Waren 1994;Arellano et al 2014;Pochelon et al 2014). This suggests a larval ability to survive under a range of physical factors encountered if migrating vertically from the deep to the euphotic zone (e.g., including a broad variation in temperature and pressure).…”

Composition and distribution of the larval decapod community in the deep sea of the Western Mediterranean Sea Balearic Sub‐basin

“…They have, in general, abbreviated larval life cycle, and larvae occurred according to the recognized reproduction periods of the adults’ populations, of species such as M. turbeculatus , M. couchi , and L. depurator . Their growth and feeding are coupled with periods of high productivity and phytoplankton peaks—in spring–summer or early winter (Estrada, 1996; Pochelon et al., 2014) to avoid starvation. By contrast, the groups with extened development life cycle (e.g.…”