Marco Mereu

Egg clutch, sperm reservoirs and fecundity of Neorossia caroli (Cephalopoda: Sepiolidae) from the southern Sardinian sea (western Mediterranean)

First observations on reproduction of Neorossia caroli from the southern Sardinian sea are reported, based on the analyses of an egg clutch and specimens collected by bottom trawl on sandy and muddy grounds. The egg clutch, consisting of 13 white eggs of 9 mm length with embryos at an advanced developmental stage, was found at 1200 m depth, attached to a piece of hard substrate. Adult specimens were collected in a depth range between 400 and 1600 metres. DNA sequences indicated that embryos, spermatangia and adults belonged to the same species, the carol bobtail squid, N. caroli. Fecundity analysis made on 40 females showed a variable number of eggs (20-611) in the ovaries, with the combined presence of advanced and developing oocytes, and few smooth eggs ready to be spawned in the oviducts of mature females. Several sperm reservoirs (spermatangia) were embedded in the mantle of some of the females, in the anterior ventral area overlying the oviduct.

Morphology, biology and molecular characterizations of Opisthoteuthis calypso (Cephalopoda: Octopoda) from the Sardinian Channel (central western Mediterranean)

Several aspects of the biology of Opisthoteuthis calypso were studied based on 3 8 individuals ( 23 males, 14 females and 1 indeterminate) retrieved from bottom trawls fished at 8 71 to 1420 m depth in the Sardinian Channel (central western Mediterranean). Data on full maturity of females are presented for the first time for this species. Information on the distribution, size, structure and fecundity for both sexes is provided, and the biological characteristics of the Sardinian samples are compared to those of other Mediterranean and Atlantic samples. Morphological variability and the peculiar structure of the shell and beak are reported and discussed. Molecular DNA sequences were obtained and compared with sequences available for the genus Opisthoteuthis.

Male reproductive system in Neorossia caroli (Joubin 1902) (Cephalopoda: Sepiolidae) from Sardinian waters (western Mediterranean Sea) with particular reference to sexual products

The male reproductive system of the bobtail squid Neorossia caroli (Cephalopoda: Sepiolidae) is described in detail, based on observations of 90 mature males caught from 500 to 1600 m depth in Sardinian waters (western Mediterranean Sea). Reproductive organs in mature specimens accounted for up to 6% of total body weight. Of this, 70% was represented by the spermatophoric complex. Up to 83 spermatophores were found inside the Needhams sac. Mean spermatophore length was 16.7 mm. Sperm mass, cement body, and ejaculatory apparatus represented 63.2%, 13.1%, and 23.7% of the total spermatophore length, respectively. Inverted spermatophores, empty spermatophore sheaths, and spermatangia were also found in the sac, and their presence is discussed. Spermatangia implanted in several parts of the bodies of males (e.g., head, funnel, and eyes) were recorded and their occurrence is discussed. The spermatophoric reaction was induced in the laboratory by submerging spermatophores in seawater, and it is described briefly.

Variability in Sepietta oweniana (Cephalopoda: Sepiolidae) hectocotyli

In this paper the morphological variability observed in hectocotyli of Sepietta oweniana specimens caught in the Sardinian seas (central western Mediterranean) is reported and measured. Atypical variants from the normal hectocotylus are described and illustrated. DNA sequencing of specimens with both the typical and atypical hectocotylization shows no genetic differences. The percentage occurrence of atypical hectocotylization and the possible causes of the origin of this phenomenon are briefly discussed.

Genetic population structure and phylogeny of the common octopus Octopus vulgaris Cuvier, 1797 in the western Mediterranean Sea through nuclear and mitochondrial markers

Genetic information is crucial for the proper exploitation of Octopus vulgaris, the most commercially valuable octopus species worldwide. The main aim of the present study was to investigate genetic structure, with the intent to inform effective management of the common octopus in Sardinia (western Mediterranean Sea), one of the most productive areas within Italian waters. Patterns of population structure were assessed in 246 specimens from seven population samples. Variation in five nuclear-encoded microsatellites and sequences of two mitochondrial genes (COI and COIII) highlighted high variability and low but significant genetic differentiation among populations, which clustered into four groups corresponding to the north, northwest, south, and east coasts of Sardinia. Secondarily, the sequence data from Sardinia were compared with GenBank data from other areas. AMOVA and Bayesian analyses supported the occurrence of significant differences within the Mediterranean Sea, and between Eastern Atlantic and Mediterranean samples. The described genetic differentiation at a regional geographical scale could be determined by a combination of historical and/or current events restricting gene flow. The occurrence of significant genetic structuring at different spatial scales is an important piece of information to define the most appropriate conservation strategies in the area, both at the local and regional level.

On the first record of the genus Octopoteuthis (Cephalopoda: Octopoteuthidae) in the Sardinian Channel (central western Mediterranean Sea)

A specimen of the rare squid genus Octopoteuthis (Cephalopoda: Octopoteuthidae) from 1600 m in the Sardinian Channel (central western Mediterranean) is described. Meristic and morphological data are provided. The specimen was a spent female and details of the reproductive system and implanted spermatangia are reported. Genetic analysis of this specimen and comparison with those available for species in this genus were carried out. Due to issues associated with the taxonomy of the genus Octopoteuthis, it was not possible to identify the specimen to the species level. The taxonomy of the genus is discussed.

Bathypolypus sponsalis (Cephalopoda: Octopoda) from the central western Mediterranean Sea

A sample of 360 Bathypolypus sponsalis from the central western Mediterranean Sea (the Sardinian Channel and the Tyrrhenian Sea) was analysed in order to describe size, depth distribution and reproductive data. The first record of the species in the Tyrrhenian Sea and of a spent female are reported in this paper. The size-structure of the sample was in between values of documented data from the western and eastern Mediterranean basins and the minimum mature sizes in both sexes and spermatophore length were similar to previous data from the eastern Mediterranean Sea. Low values of gonadosomatic index and fecundity, the asynchronous ovulation, in addition to an extended reproductive period, have been associated with an intermittent spawning strategy.