Morphological identification and molecular confirmation of the deep-sea blue and red shrimpAristeus antennatuslarvae

Abstract

The early life stages of the blue and red shrimp Aristeus antennatus (Decapoda: Dendrobranchiata: Penaeoidea: Aristeidae) were described by Heldt in 1955 based on plankton samples, larval rearing and assumptions of species habitat. Even with adequate keys, identification of its first larval stages remained a difficult task due to the lack of specific morphological characters which would differentiate them from other Penaeoidea species. Larvae of Aristeus antennatus were collected in the continental slope off the Spanish Mediterranean coast in August 2016 with a neuston net and preserved in ethanol 96%. DNA from the larvae was extracted and the molecular markers Cytochrome Oxidase I and 16S rDNA were sequenced and compared to that of adults with the objective of confirming the previous morphological description. Then, we present additional information to the morphological description of Aristeus antennatus larval stages through scanning electron microscopy and molecular analysis. This represents the first documented occurrence of Aristeus antennatus larvae off the Catalan coast and sets the grounds for further work on larval ecology and population connectivity of the species, which is an important contribution to a more sustainable fishery.

Modeled buoyancy of eggs and larvae of the deep-sea shrimp Aristeus antennatus (Crustacea: Decapoda) in the northwestern Mediterranean Sea

“…The study indicated that near-bottom vertical currents do not advect individuals up to shallower layers, and suggested that the vertical distribution of eggs or larvae can only be explained by their capacity of moving across the water column. To our knowledge, the youngest stage of A. antennatus' larvae found in superficial waters is the first substage of protozoea [11,13]. This finding supports the hypothesis of positive buoyancy in the previous stages of A. antennatus' larvae.…”

“…In our study, over half of the released individuals reached the layer where a high quantity of A. antennatus' larvae is found (i.e., the surface layer [11]). We estimated an average egg density of 884 kg/m 3 , which was around 100 kg/m 3 lighter than the ones described for other deep-sea shrimp eggs (1025-1082 kg/m 3 ; [17]) and the seawater densities of the northwestern Mediterranean Sea (from 1025.3 kg/m 3 in Cap de Creus to 1024.1 kg/m 3 in the Eivissa channel; [23]).…”

“…The buoyancy module was initially activated at the release of the eggs. The eggs were positively buoyant by assuming that on the one hand, young larvae of A. antennatus are found in the surface layer [11,13] and on the other hand, if the buoyancy is neutral or negative, the swimming abilities of the nauplius could not explain an average vertical rise on 600 m. When individuals reached a non-buoyant stage, the module was deactivated. For simplification, and due to lack of knowledge, we neglected the temporal change of egg size and density.…”

“…In the case of A. antennatus, knowledge can be gathered from various larvae of Dendrobranchiata species, which is the taxonomic family of A. antennatus, e.g., larvae molt after the hatching of eggs with the following order: nauplii, protozoea, and mysis. Lecithotrophic stages (eggs and nauplii) of A. antennatus have not been observed yet, but its first planktotrophic stage (protozoea) is largely found in the surface layer [11]. Because ripe females spawn on the sea bottom, the embryonic and nauplius stages are assumed to have abilities (buoyancy, swimming ability) that take them to the surface.…”

Influence of the summer deep-sea circulations on passive drifts among the submarine canyons in the northwestern Mediterranean Sea

“…where dX is the three-dimensional displacement vector of the particles during a time step dt of 30 min under the veloc-ity vector U from the hydrodynamic models. RK4 is a stable and reliable multistep method for numerical integration (North et al, 2009;Qiu et al, 2011) and is commonly used in Lagrangian dispersal models (North et al, 2009;Chen et al, 2003;Paris et al, 2013). The Ichthyop algorithm used trilinear and linear interpolations in space and time from the daily average ROMS velocity field output to each particle position at all time steps.…”