During the INDEMARES/CHICA 0610, 0211 and 0412 expeditions, carried out in the northern Spanish sector of the Gulf of Cádiz (Spain), samples were collected with a box-corer in 11 mud volcanoes and their adjacent bottoms. Chemoautotrophic communities were found in nine mud volcanoes. Among Decapoda, a rare eucalliacid, belonging to the genus Calliax and related to the Mediterranean infralittoral species C. lobata (de Gaillande and Lagardère 1966), was present in three of them. Data on its morphology, biogeographic distribution, vertical distribution within the burrows, sediment composition, pH and redox potential values (each in 5 cm intervals) are given; information on the chemoautotrophic communities associated with this species are also provided.

The alien nudibranch Polycera hedgpethi Er. Marcus, 1964, has been found in the Gulf of Cádiz (El Portil, Huelva). The present record in the Gulf of Cadiz could be considered an opportunity to connect the isolated Eastern Atlantic records for this species with those from the Mediterranean, even taking into consideration the possible unreported presence of this species along the North African Mediterranean coast. The collected specimens exhibited reproductive behaviour, suggesting the possibility of future additional records for this locality.

The occurrence of a living population of the giant deep-sea oyster Neopycnodonte zibrowii is reported on the slopes of Hespérides Mud Volcano Complex in the Gulf of Cádiz, south-western Iberian Peninsula, in 720 m depth. A noteworthy circumstance of this new record is its situation on a sea bottom which was suitable for the operation of a rock dredge and does not apparently feature abrupt cliffs or rocky overhangs as in previous reports on the species.

Here we report the stranding of two occasional species of the genus Mesoplodon not previously recorded on the Andalusian coast. Two Blainville's beaked whale stranded in two different events, one in Matalascañas (Huelva) in 1996 and another in Tarifa (Cádiz) in 2003, and two Sowerby's beaked whale were found stranded together on the coast of Rota (Cádiz) in 2007. These strandings are located near the range boundaries of both species, whose distribution is poorly known. Additionally, three new records of Gervais' beaked whale stranded on the Andalusian coast are presented.

The capture of a specimen of Polymixia nobilis, a rare species in the eastern Atlantic waters north of the Canary and Madeira Islands, is reported as the first record in the vicinity of the Strait of Gibraltar.

The capture of a specimen of Selene dorsalis in the Chipiona (southern Spain), a rare species in waters north of the Cape Verde Islands and Senegal, is reported as the first record in the Gulf of Cadiz.