Augusto César Crespi-Abril

Analysis of the ontogenetic variation in body and beak shape of the Illex argentinus inner shelf spawning groups by geometric morphometrics

In this paper we analysed size and shape differences of body (mantle and fins) and inferior beak of the squid Illex argentinus from two Patagonian inner-shelf spawning groups. A new method was developed to reconstruct three-dimensional coordinates based on the 2-D projection of the beak on a plane. Shape of the beak did not vary between groups, sexes and maturity condition of individuals. Also, no beak shape changes were observed through the ontogeny. In contrast, as larger and heavier squids were considered in shape analysis, body widened near the fin insertion, and fin area increased. Our results suggest that shape adaptations of I. argentinus through the ontogeny reflect modifications to optimize swimming performance rather than to increase gamete holding capacity.

Analysis of the morphological variation of Doryteuthis sanpaulensis (Cephalopoda: Loliginidae) in Argentinian and Brazilian coastal waters using geometric morphometrics techniques

Shape variation of individuals from three locations, two from Argentina and one from Brazil, was analysed by geometric morphometrics techniques. Individuals were weighed, measured, sexed, assigned to a maturity stage and photographed. For the analysis, two landmark configurations were used: one of nine landmarks (9L) and another of 25 landmarks (25L). To visualise shape variation, a principal component analysis (PCA) on Procrustes coordinates was conducted. The percentage of total shape variation explained by the 9L configuration was 80.5% (PC1: 61% and PC2: 19.5%), while the percentage for the 25L configuration was 76.4% (PC1: 54.8% and PC2: 21.6%). Based on this, shape analyses were performed using only the 9L configuration. The PCA results indicated that specimens show a large overlap between the categories based on sex and maturity stage. When location is considered, squid shape from São Sebastião and Rawson Port were very similar, while in Nuevo Gulf, the presence of two different morphological groups were observed: one similar to São Sebastião and Rawson Port, and the other with a morphology typical of Nuevo Gulf. Thus, two different morphotypes were defined: (i) morphotype of the continental shelf and (ii) morphotype typical of the gulf. The continental shelf morphotype is characterised by larger fins and wider mantle than the gulf morphotype. These results suggest that the morphotypes of Doryteuthis sanpaulensis are adaptations to oceanographic regimens.

Perspective: Continental Inputs of Matter into Planktonic Ecosystems of the Argentinean Continental Shelf—the Case of Atmospheric Dust

Land-derived dissolved and particulate matter (allochthonous matter) affect pelagic ecosystems by changing factors which include light penetration, nutrient availability, substrate concentration, and in general, biogeochemical cycles in the ocean. In a context of growing anthropogenic impact, this material may not only increase its load but also carry toxic substances. Riverine runoff is the most studied mechanism of particulate matter input from the continent to the sea in the southern region of South America where the continental shelf is widest (e.g., Atlantic Patagonia). However, there are other sources of particulate matter which are not affected by rivers in this semiarid region: aeolian material. Winds in this region (notably the Southern Hemisphere westerlies) are the only way continental aeolian material (atmospheric aerosols or “dust”) can reach not only the shelf but even further onto oceanic HNLC (high nutrient–low chlorophyll) regions of the Atlantic Southern Ocean. This potential impact of Patagonian dust beyond the continental shelf attracts the attention of the global climate community, and at the same time, it opens questions about the potential effects of dust in coastal waters. According to previous work and ongoing studies, deposited particles can have significant impacts in the chemical and biological components in the euphotic zone. However the effects of this airborne material in plankton communities of South America are largely unknown, mostly due to the lack of in situ studies and observations. Since the events of dust mobilization, transport, and deposition are expected to increase (due to climate change) and interact with other global change factors such as warming and more intensive land use, the influence of dust input may become more prominent for coastal and oceanic regions of southern South America in the next decades.

Analysis of shape variability and life history strategies of Illex argentinus in the northern extreme of species distribution as a tool to differentiate spawning groups

ABSTRACT This study aimed to differentiate local and migratory spawning groups of the shortfin squid Illex argentinus caught in Brazilian waters using geometric and traditional morphometric methods and size-selective processes. The back-calculated length distributions reconstructed from daily growth increments deposited in the gladius allowed the identification of size-selective processes that may be related to different life history strategies. Landmark analysis on body shape (geometric morphometric) revealed that spawning groups presented significant ontogenetic variations in terms of body outline. In addition, traditional morphometric methods, based on multivariate analysis, associated juveniles of the expected migratory group (large size) and differentiated them from the local group individuals (small size). The changes in form, probably linked to the environmental gradients experienced by individuals throughout ontogeny, were interpreted as adaptations to improve swimming capacity. Migrant individuals have being differentiated from the smaller sizes group by body characteristics (broad fins, elongated and thicker mantle), which may increase the ability to perform long migrations.