Manuel E. Garci

The mussel Xenostrobus securis: a well-established alien invader in the Ria de Vigo (Spain, NE Atlantic)

Biological and habitat characterization of the non-indigenous invasive species Xenostrobus securis was undertaken in the Ria de Vigo. This study included genetic identification of mussel samples collected from introduced and endemic areas, and the assessment of mussel size, population abundance, geographic distribution, pathological condition, and sediment composition of substrata type. The mussel had a marked patchy distribution, being more abundant in brackish sites with fine sediments and high organic matter content. Pathological analysis revealed that X. securis does not play any role as vector for introducing allochthonous pathogens in the Ria de Vigo. Nevertheless, depending on its invasiveness potential, the mussel could be a key host favouring spreading and epizootic outbreaks of marteliosis which is known to be harmful for local bivalve populations. Phylogenetic analyses of the COI gene placed all the resulting sequences in a clade within the genus Xenostrobus and its phylogeny congruent with an Australian/Pacific origin. The COI tree suggests two historical introductions in European waters. One of these invasions seems to have started in Galicia, moving from there towards Italy and France, while the geographical spread of the second invasion cannot be deciphered, although the Australian/Pacific origin of this invasion seems very possible. The 18S network is congruent with one invasion starting in Galicia or in Italy, as the Australian haplotype is closely related to the haplotype found in these areas. Several hypotheses accounting for the colonization history of this species in Galician waters are discussed.

Xenostrobus securis (Lamarck, 1819) (Mollusca: Bivalvia): first report of an introduced species in Galician waters

The presence of the non-indigenous species, the black-pygmy mussel Xenostrobus securis, is reported here for the first time in an intense shellfish farming area off Galicia (NW Spain). Very high concentrations of this mytilid bivalve have colonized estuarine waters located at the inner part of the Ria de Vigo. The invasive role of X. securis is discussed in the context of the wide ecological tolerance of the species and the recent finding of settlements of this species on numerous colonies of the economically-important blue mussel Mytilus galloprovincialis. The mode of introduction of the black-pygmy mussel is also discussed in relation to human management activities.

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.

The black-pygmy mussel Limnoperna securis in Galician Rias (north-eastern Atlantic): new records and first evidence of larval stages predation by copepods

The presence of the non-indigenous species, the black-pygmy mussel Limnoperna securis , was surveyed for the first time in the Rias of Pontevedra and Arousa, areas adjacent to the first location (Ria of Vigo) of this potential invader in Atlantic waters. Molecular identification of the mussels was conducted by polymerase chain reaction amplification and sequencing of nuclear and mitochondrial genes. This paper describes for the first time the species in the Ria of Pontevedra, confirming that this invader was absent in an intense shellfish farming area of the Ria of Arousa (Galicia, north-western Spain). Field sampling revealed that relatively high concentrations of this mytilid bivalve have colonized some localities of the inner part of the Ria of Pontevedra located in brackish waters. A comparison between population densities, size and substrate preference of L. securis in the Rias of Pontevedra and Vigo was conducted. Dispersion capacity of L. securis is discussed based on molecular detection of larval stages in the stomach contents of the copepod Centropages typicus coupled with physical oceanography of the southern Galician Rias. The invasive role of L. securis is also discussed in the context of the bissus secretion and attachment strength, ecological tolerance of the species, and the recent finding of settlements of this species on numerous colonies of the economically important blue mussel Mytilus galloprovincialis .

Burying behaviour in the bobtail squid Sepiola atlantica (Cephalopoda: Sepiolidae)

Abstract The burying behavioural pattern of the small Atlantic bobtail squid (Sepiola atlantica) in natural substrate is described, quantitatively differentiating the movements in different phases and the chromatic changes associated with this behaviour. All specimens showed the same two-part sequence of burying, which triggered a display of colour changes peculiar to this species. Our results suggested that this was a consistent behaviour during burial. The mean latency time in the alert posture was 9.55 ± 5.49 s. The mean duration of the first phase was 12.2 ± 4.37 s. The mean duration of the second phase was 10.2 ± 2.95 s. The average time spent completing the behavioural pattern was 21.9 ± 4.93 s. Burying time was not related to size. Differences observed between individuals were associated with the number of movements in each phase. However, these movements were not significantly related to the size of the animals. A comparison of the burying pattern of this species with other members of the family Sepiolidae is made.

From brooding to hatching: new insights from a female Octopus vulgaris in the wild

A brooding Octopus vulgaris female was monitored for 128 days in her natural habitat. The main reproductive events and embryonic development in relation to the temperature inside the spawning den, which was recorded by long-battery-life mini-data loggers, are described in the wild. The den temperature ranged from 12.9 to 19.3°C. The total number of egg strings was 160, and the total number of eggs spawned ranged between 139,040 and 241,760 (mean 190,400). The brooding period, the egg laying interval and the duration of the hatching course lasted 128, 35 and 43 days, respectively. Both egg laying and hatching were intermittent processes. The time taken for embryonic development was variable (85–128 d) and depended on the laying date, temperature and position of the string in the egg cluster and the position of the egg in the egg string. The first hatching observed occurred after a progressive and gradual increase of the temperature from 14.9 to 19.3°C. The 280 min of video recordings taken by scuba divers showed that several times, this female opened and closed a small window in the obstructions of the den entrance to facilitate a way out for the hatchling batches.

Seasonal abundance of the Atlantic bobtail squid Sepiola atlantica in Galician waters (NE Atlantic)

Abstract The abundance of the bobtail squid Sepiola atlantica was assessed for Areamilla beach at Ría de Vigo. Sampling was carried out monthly and simultaneously by two scuba divers at two sandy submersed zones between December 2007 and November 2009. A total of 505 specimens of S. atlantica (204 juveniles, 149 males and 152 females) were collected. The mean annual abundance of the species was 0.01±0.01 ind./m2 from December 2007 to November 2008, and 0.02±0.01 ind./m2 from December 2008 to November 2009. Abundances were not significantly different between the two depth zones for each year, nor for seasons. However, total abundance was significantly different between seasons. Abundance showed a seasonal pattern with the lowest values in summer. For each season populations were formed by specimens of different size during the two sampling years, as well in both depth zones. Spawning occurs throughout the year. Two peaks of recruitment, one in summer and another in autumn, were observed. Whether seasonal differences in abundance are due to migration of the individuals from shallow to deeper zones related to changes in bottom temperature is discussed.

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.