Corrado Costa

Relationship between shape and trophic ecology of selected species of Sparids of the Caprolace coastal lagoon (Central Tyrrhenian sea)

SynopsisThe shapes of juveniles of nine species of the family Sparidae (Diplodus annularis, Diplodus puntazzo, Diplodus sargus, Diplodus vulgaris, Lithognathus mormyrus, Pagellus acarne, Sarpa salpa, Sparus aurata, Spondyliosoma cantharus), collected in the tide channel of the Caprolace Lagoon (Central Tyrrhenian Sea—Italy) were studied using geometric morphometry. These species have different ecologies. The trophic ecology of each species, reported as TROPH values, are related to shape. For the first time the relationship between shape and trophic ecology in sparids was studied in a quantitative way giving an ecomorphological meaning to the shape differences. Mean shapes of carnivorous, omnivorous and herbivorous fish were extracted, analyzed and found to be unique. Strict herbivores such as Sarpa salpa have a small mouth gap; omnivores such as the four species of the genus Diplodus have a higher body (discoidal) and a caudal peduncle shorter and higher; carnivorous species such as Lithognathus mormyrus, possess a relatively larger head region, a larger mouth gap, a longer body and a caudal peduncle longer and narrower.

Skeletal quality assessment of reared and wild sharpsnout sea bream and pandora juveniles

In this study, skeletal descriptors of wild and reared juveniles of sharpsnout sea bream (Diplodus puntazzo) and pandora (Pagellus erythrinus) were compared to assess the quality of farmed individuals. A total of 1016 wild and reared juveniles of sharpsnout sea bream and pandora were inspected for skeletal abnormalities and a qualitative evaluation of aquaculture production was achieved. The applied approach was based on the analysis of meristic character counts, and incidence and pattern of skeletal anomalies. Correspondence Analysis (CA), Multi-Response Permutation Procedure (MRPP) and Indicator Species Analysis were performed on a data matrix. Such methodology allowed the identification of different levels of disturbance generated by the captive conditions.

Ecomorphology of morpho-functional relationships in the family of Sparidae: a quantitative statistic approach.

In many fish species, morphological similarity can be considered as a proxy for similarities in habitat use. The Sparidae family includes species that are recognized for common morphological features such as structure and positioning of the fins and specialized dentition. The aim of this study was to quantitatively describe the relationship of body shape morphology with habitat use, trophic level, and systematics in the majority of known Sparidae species (N = 92). This ecomorphological comparison was performed with a geometric morphometric approach considering as variables the Trophic Index (TROPH), the habitat (i.e., classified as demersal, benthopelagic and reef associated) and the phylogenetic relationship of species at the subfamily level. The analysis by the TROPH variable showed a positive relation with shape because the morphological features of all the species are strongly correlated with their trophic behavior (e.g., herbivore species have a smaller mouth gap that make them able to feed upon sessile resources). The morphological analysis according to the Habitat variable was used to classify species according to a feeding‐habitat niche in terms of portion of the water column and seabed space where species mostly perform their behavioral activities. We described three kinds of morphological designs in relation to a benthopelagic, demersal and reef‐associated habit. The six subfamily groups were morphologically well distinguishable and the cladogram relative to Mahalanobis morphological distances was compared with those proposed by other authors. We also quantified the phylogenetic relationship among the different subfamilies based on the analysis of shape in relation to trophic ecology, confirming the observations of the authors. J. Morphol., 2009.

External shape analyses in Atherina boyeri (Risso, 1810) from different environments

Abstract In this study, specimens of the large-scale sand smelts Atherina boyeri, a fish species occurring in different environments (freshwater lakes, coastal lagoons, sea), were examined for their body shape and the differences observed were analysed statistically. The variation of external morphology was investigated in 11 populations from different environments. The morphology was characterized by means of geometric morphometrics and compared; results showed that the phenotypic (morphometric) distances among samples differed significantly by Relative Warp Analysis, specimens from the coastal lagoon being clearly separated from those belonging to lake and marine populations on the first RW1 axis and the latter ones separated on the RW2 axis. The results obtained also show the absence of a gradient of shape differences according to lake–lagoon–sea origin or eidonomic convergence in fish from environments with similar (high) trophic productivity. An integration of geometric morphometric data in a multidisciplinary approach with genetic, biochemical, geographical, molecular and other morphological analyses is necessary to describe the phylogenetic relationships of Atherinidae, shedding light on some ambiguous taxonomic ranks.

Evidences on the transient disruption of Sabella spallanzanii (Polychaeta, Sabellidae) fan activity rhythm in laboratory constant darkness

Circadian and ultradian rhythms were analyzed in Sabella spallanzanii tested in laboratory constant darkness conditions. A video camera took images per 30 s during a week. The number of times animals opened the fan per 30 min was counted by an observer. Resulting time series were subdivided into 24‐h segments in order to assess the change of the activity rhythm over consecutive days. Periodogram and waveform analyses measured the periodicity and the pattern of fluctuation, at each cycle. Results indicate that animals express a major circadian peak in the first day of test, and this progressively spits into subcomponents from days 2 to 4. At days 5 and 6 the circadian peak is reconstituted. The activity phase of a rhythm (α) and its amplitude of oscillation were also computed per 24‐h segments. The values of different time series were averaged at corresponding 24‐h stages. A significant increment of mean α was observed from days 1 to 4, while conversely the amplitude decreased. From days 5 to day 6, an opposite trend in both variables was observed. These results are descriptive but can be interpreted in the context of models accounting for the generation of ultradian rhythms when controlling oscillators became transiently uncoupled.

Shape changes and differences in the cranial region in Acipenser baerii and A. naccarii of different size

Abstract Geometric morphometric techniques were used to characterize shape changes of the cranial region during growth of Acipenser baerii and A. naccarii and to compare the two species. A total of 54 individuals of A. baerii and 268 individuals of A. naccarii were analysed. Species identification in sturgeons is sometimes difficult, influenced by morphological plasticity and individual variability, and complicated by human intervention and manipulation (aquaculture, hybridization, and pollution). There are several statistically significant allometric shape changes during the growth of the two species and their cephalic region is significantly different. Geometric morphometrics appears to be a good candidate to become a low‐cost standard methodology for use in morphometric analysis and systematics of Acipenseridae.