Miguel Cabanellas-Reboredo

Relative Growth Rates of the Noble Pen Shell Pinna nobilis Throughout Ontogeny Around the Balearic Islands (Western Mediterranean, Spain)

ABSTRACT In this study, we evaluated the growth of adults and juveniles of the endangered noble pen shell Pinna nobilis, calculated the growth rates of newly recruited juveniles, and described relative directional growth during ontogeny. We described growth using posterior adductor muscle scars (PAMS) and fit of the von Bertalanffy growth curve for adult population data at shallow depths (5–10 m) around the Mallorca and Ibiza islands, and compared the parameters with other Mediterranean populations. Populations around Mallorca could be fitted according to the von Bertalanffy function Lt = 65.31(1 - e-0.11(t + 0.53)), whereas for Ibiza the function was Lt = 154.55(1 - e-0.03(t + 4.31)). We compared first-year growth rates obtained in the laboratory and from field collections with newly settled individuals. We found that experimentally evaluated growth rates of juveniles in the laboratory of 0.18 mm/day are low compared with minimum values obtained in the field, which range, on average, from 0.28–0.32 mm/day, indicating food availability can limit growth. Furthermore we investigated relative allometric growth patterns during ontogeny using a unique data set ranging from measurements of newly recruited juveniles with shell length less than 1 cm to measurements on adult shells of 69.8 cm length. Fitting a sigmoidal function to our data and solving for the allometric exponent b, we found 3 distinct growth periods: preferential growth in the length direction up to 5.82 cm in shell length, then widening of the shell up to 14.64 cm, after which the shape of the shell becomes more elongated once again.

Cannibalistic behavior of octopus (Octopus vulgaris) in the wild.

The first description of cannibalism in wild adult Octopus vulgaris is presented from 3 observations made in the Ría de Vigo (NW Spain), which were filmed by scuba divers. These records document common traits in cannibalistic behavior: (a) it was intercohort cannibalism; (b) attacks were made by both males and females; (c) in 2 of the records, the prey were transported to the den, which was covered with stones of different sizes; (d) the predator started to eat the tip of the arms of its prey; (e) predation on conspecifics occurred even if there were other abundant prey available (i.e., mussels); and (f) the prey/predator weight ratio in the 3 cases ranged from 20% to 25% body weight. The relationships between this behavior and sex, defense of territory, energy balance, food shortage, competition and predation, as well as how the attacker kills its victim are discussed.

Initial data on settlement and recruitment of macrobenthic organisms on artificial substrates located over Posidonia oceanica meadows

Abstract The present paper presents initial data about settlement and recruitment of macrobenthic organisms through the use of artificial substrates placed over Posidonia oceanica (L.) Delile meadows in the Western Mediterranean. Three settlement frames were submerged in the Marine Protected Area (MPA) of Palma Bay (Balearic Islands, Western Mediterranean). A total of seven macrobenthic species from five phyla were recorded. Assemblages were dominated by the bivalve Anomia ephippium with the largest percentage of surface covered being 43.5% (±4.96). This study provides information on massive primary settlement of A. ephippium. Moreover, this species generated an optimal recruitment substrate for the settlement of two species of polychaete (Serpula vermicularis and Hydroides elegans) and the barnacle Balanus amphitrite. An interspecific relation was observed between B. amphitrite and A. ephippium, since 99.9% of this cirriped recruited directly over A. ephippium. Additionally, this study demonstrated that there is a substantial larval pool available ready to colonize suitable substrates for benthic organisms such as the bryozoan Calpensia nobilis and the ascidian Botryllus schlosseri associated with Posidonia oceanica. Our study is the first approach to gain knowledge of the complex process regarding settlement and recruitment, as well as the application of artificial structures in order to investigate the larval pool over P. oceanica meadows.

New insights on the external features of egg capsules and embryo development in the squid Loligo vulgaris

Abstract The embryonic development of the squid Loligo vulgaris was observed from 183 egg masses collected from special devices deployed throughout Cabrera National Park (Baleares Islands, western Mediterranean Sea). Sequence alignment analysis of the cytochrome oxidase I gene revealed that all embryos belonged to L. vulgaris. In total, 549 egg capsules were examined. Viable egg capsules (n = 420) were classified into one of five maturation stages according to the primary external features. The length of the viable egg capsules varied between 40 and 170 mm, and increased with embryonic development. The non-viable capsules (n = 129) were categorized into four groups: I (Ginger root), non-viable II and III, and empty egg capsule (IV). The percentage of non-viable capsules (i.e. grades I, II and III) was 92.25%. Empty capsules accounted for 7.75% of the total non-viable egg capsules. Embryonic development was classified into a second scale of eight stages. Egg capsule stage and embryonic stage were significantly related (n = 420; p < 0.001), facilitating the determination of the embryo developmental phase based on the outward appearance of the egg capsules. The embryo development stage based on the external features of the egg capsules might constitute an innovative tool for in situ embryological data collection. This new method is neither time consuming nor invasive, and could be helpful in fishing cruises, for scuba diving visual census in natural habitats and for laboratory culture. Slight variability in the developmental embryonic stages within egg capsules from the same egg mass was identified. The origin of this asynchrony is discussed. Chronological appearance of organs was similar to that of the six loliginid species previously examined. However, some developmental changes in the timing or rate of events (heterochronies) were observed: Hoyle’s organ was formed earlier in L. vulgaris and the appearance of ventral chromatophores was slightly delayed (2 days) compared with the other species considered.