Monitoring the spread of non-indigenous species is fundamental to study global warming effects on marine biodiversity. A valuable tool is represented by the continuous updating of the geographic range expansion of non-indigenous species. Lamprohaminoea ovalis is a Lessepsian mollusc initially recorded in the Mediterranean Sea in 2001. This paper reports its range expansion over the last 20 years related to water warming. The first record of Lamprohaminoea ovalis from the Ligurian Sea (NW Mediterranean) is also reported. Two individuals (about 10 mm length) were observed on a sub-vertical rocky bottom at 26 m depth displaying potential trailing behaviour. This recent finding extends the currently known distributional range of Lamprohaminoea ovalis, representing the northernmost occurrence of this non-indigenous species in the western Mediterranean Sea.

Global warming is facilitating the poleward range expansion of plant and animal species. In the Mediterranean Sea, the concurrent temperature increase and abundance of (sub)tropical non-indigenous species (NIS) is leading to the so-called ‘tropicalization’ of the Mediterranean Sea, which is dramatically evident in the south-eastern sectors of the basin. At the same time, the colder north-western sectors of the basin have been said to undergo a process of ‘meridionalization’, that is the establishment of warm-water native species (WWN) previously restricted to the southern sectors. The Gulf of Genoa (Ligurian Sea) is the north-western reach for southern species of whatever origin in the Mediterranean. Recent (up to 2015) observations of NIS and WWN by diving have been collated to update previous similar inventories. In addition, the relative occurrences of both groups of southern species have been monitored by snorkelling between 2009 and 2015 in shallow rocky reefs at Genoa, and compared with the trend in air and sea surface temperatures. A total of 20 southern species (11 NIS and 9 WWN) was found. Two WWN (the zebra seabream Diplodus cervinus and the parrotfish Sparisoma cretense) and three NIS (the SW Atlantic sponge Paraleucilla magna, the Red Sea polychaete Branchiomma luctuosum, and the amphi-American and amphi-Atlantic crab Percnon gibbesi) are new records for the Ligurian Sea, whereas juveniles of the Indo-Pacific bluespotted cornetfish Fistularia commersonii have been found for the first time. While temperature has kept on increasing for the whole period, with 2014 and 2015 being the warmest years since at least 1950, the number of WWN increased linearly, that of NIS increased exponentially, contradicting the idea of meridionalization and supporting that of tropicalization even in the northern sectors of the Mediterranean basin.

Okenia aspersa is a north-eastern Atlantic species, only previously recorded as Okenia quadricornis from the Malta Archipelago in the Mediterranean Sea, and in juvenile forms, from Sicily and the Gulf of Naples. A second adult specimen is recorded in the present paper, which was found along the Noli Cape coast, in the western Ligurian Sea (Italy). It was found on pebbles at a depth of 10 m. In the same area, at a depth of 5.5 m, two specimens of Doto koenneckeri and three of their egg masses were found. This species, also described from Norway and Ireland, was only previously known to occur in the Mediterranean Sea off Spain and France. It is likely that the cold winter temperatures of the Ligurian Sea allowed this species to live and reproduce.

The northernmost record of the alien nudibranch Godiva quadricolor is reported here, about 400 km farther north than the previously published one and the farthest to be recorded from the equator. It is also the second published record of this species along the Italian coasts and the first record from the Ligurian Sea. A single specimen was reported during a scuba dive, crawling on small stones inside the Site of Community Importance ‘Fondali Noli – Bergeggi SCI’, at a depth of 3.5 m. The species, described in 1927 in South Africa, is considered to be rapidly expanding its original areal distribution thanks to maritime traffic. A review of the known actual distribution is also reported here.

The stomach contents of a male sperm whale, Physeter macrocephalus, stranded on Forte dei Marmi beach (Italy, Ligurian Sea) were examined. Food items consisted exclusively of cephalopod hard parts: 233 upper and 291 lower beaks and one fish eye lens. The majority of the identified cephalopod beaks belonged to Histioteuthis bonnellii, but a few beaks of Galiteuthis armata and Octopoteuthis sp. were also found. A new beak size–cephalopod size regression was created for H. bonnellii with specimens caught in the study area. Reconstructed prey weight for the species was much higher when applying this new regression instead of Clarke's, highlighting the need for area- and species-specific regressions for dietary studies. Our analysis represents the second report on the stomach contents of sperm whales from the Mediterranean and the first available information for the Western basin.

In summer 2010, a systematic survey was carried out in the harbours of La Spezia (Ligurian Sea) and Olbia (western Tyrrhenian Sea) with the aim of studying alien species in Italian commercial harbours. Biological samples were collected by replicate scraping on the concrete walls of docks at the beginning and at the end of the summer season. Identification to species level revealed the presence of Tricellaria inopinata, an invasive alien cheilostome bryozoan of Pacific origin, first introduced to Europe in the Lagoon of Venice (Italy) in 1982. Thereafter it has been reported in other ports in Britain, Belgium, The Netherlands, France, Spain, Portugal, Tunisia, Ireland, Scotland, Germany and Massachusetts (USA). Its finding in the harbours of La Spezia and Olbia represents the first record of the species in the Ligurian Sea and in the western-central Tyrrhenian Sea, respectively. Commercial harbours are common sites of biotic invasions due to the presence of the most important vectors of alien species introduction, namely aquaculture, and shipping. The occurrence of T. inopinata in the harbours of La Spezia and Olbia is discussed, taking into consideration possible pathways of introduction into the western Mediterranean Sea, which very likely is the transfer of molluscs from the northern Adriatic (namely the Lagoon of Venice).

A new capture of Kyphosus saltatrix in the eastern Ligurian Sea confirms the increasing presence of this species in the Mediterranean Sea.

The presence of herbivorous fish of the family Kyphosidae in the Mediterranean has increased with the first record of the species Kyphosus incisor which occurred in July 2009 at Camogli, eastern Ligurian Riviera.

The first record of Gobius couchi for the Ligurian Sea and the second record of this rare gobiid fish for the western Mediterranean are reported.

The first confirmed records of two blonde rays (Raja brachyura) in the Ligurian Sea for 140 years are described. Two specimens were caught off Cogoleto (western Ligurian Sea) and they were deposited in the Civic Museum of Natural History ‘Giacomo Doria’ of Genoa. Morphometric and meristic features have been reported.

The first case of albinism in the kitefin shark, Dalatias licha, is reported here through the study of one specimen caught by professional bottom trawl in the Gulf of Genoa, Ligurian Sea. The albino surface was quantified and morphometric and meristic characteristics were compared with those of normal specimens of the same sex and equivalent length, caught within the same area. The shark body presented a partial reduction in pigmentation and no morphometric differences between the albino specimen and the normal individuals were observed.