Elena Marco-Herrero

The family Grapsidae is composed of 39 species belonging to seven genera. Currently, larval data are known for 24 out of the 39 species, but the megalopa stage remains unknown for the genera Goniopsis, Grapsus, Leptograpsus, and Planes, although megalopae collected in the plankton have been tentatively attributed to Grapsus and Planes. Thanks to the MALASPINA and MAF research projects, a significant number of megalopae were collected from open-ocean plankton worldwide, and, using DNA barcoding (16S and/or COI genes), a high percentage of them were identified. At the molecular level, Grapsidae have been widely studied, so the availability of barcode sequences in public databases has allowed us to identify the megalopa of Goniopsis pulchra, Grapsus grapsus, Leptograpsus aff. variegatus, Pachygrapsus socius, P. transversus, and Planes minutus. In the present work, these megalopae are described in detail and compared with those previously known. Consequently, for the first time, the morphology of the megalopa stage can be compared across all grapsid genera, and a set of characteristics is defined to identify the grapsid megalopa from the rest of the brachyuran megalopae.

Pinnotheres pisum (Linnaeus, 1767) is one of the pinnotherid crab species with the highest number of reported bivalve hosts. Here we first report this species living in the bivalve Glossus humanus (Linnaeus, 1758), and provide an update on P. pisum symbiotic associations (i.e., known hosts), reaching up to 34 taxa. Partial sequences of the mitochondrial gene cytochrome c oxidase subunit I were first obtained from P. pisum and the G. humanus host from the Mediterranean Sea, confirming conspecificity with specimens from the Atlantic Ocean of the same species.

The Ebre Delta (NW Mediterranean), which is considered a highly vulnerable ecosystem, is one of the most important European wetlands and belongs to the Natura 2000 network. The present study aims to characterize the benthic megainvertebrate communities inhabiting the Ebre Delta soft-bottom infralittoral to acquire faunistic and biological knowledge for two periods of time, 23 years apart. Experimental trawls were conducted during the two periods (1992–1993 and 2016–2017) in three depth strata, between 5 and 25 m. A total of 139 and 170 taxa were collected at each period, respectively. Our results showed that community species composition and structure varied between periods and among depth strata. Overall, a large decrease in density and biomass was detected for most species in all three depth strata examined (0–5, 15–20, and 20–25 m) in 2016–2017, especially in the shallowest stratum. Species richness was higher in 2016–2017 than in 1992–1993, and the lowest values were found at the shallowest stratum in both periods. The significant biomass losses herein reported highlight the need to increase, in time and effort, the monitoring of large marine invertebrates in coastal areas, where many taxa provide important ecosystem functions and services.

Seamounts are globally important and essential ecosystems for supporting and maintaining marine biodiversity. In the Mallorca Channel, three prominent seamounts are present: Ausias March, Ses Olives and Emile Baudot. Currently, this area is being evaluated for inclusion in the Natura 2000 network. For this objective three surveys were conducted in the seamounts of the Mallorca Channel during July 2018 and July 2020. Samples of macro-invertebrates obtained in the deep sea revealed a rich fauna of Mollusca (68 species belonging to 40 families). New Mollusca occurrences included: four species of Gastropoda: Colus jeffreysianus, Cantrainea peloritana, Fusiturris similis, Gymnobela abyssorum, and seven species of Bivalvia: Pododesmus squama, Allogramma formosa, Asperarca nodulosa, Cetomya neaeroides, Spondylus gussonii, Haliris granulata and Policordia gemma. Where possible, the identification of these species was confirmed using the DNA barcoding method (sequencing of the cytochrome c oxidase subunit I). This study contributes towards filling the gap in knowledge of deep-sea mollusc fauna of the north-western Mediterranean.

One of the objectives of the LIFE IP INTEMARES project is to assess the impact of bottom trawling on the vulnerable benthic habitats of the circalittoral bottoms of the Menorca Channel (western Mediterranean), designated a Site of Community Importance (SCI) within the Natura 2000 network. The present study compares the epibenthic communities of four areas, subjected to different bottom trawl fishing intensity levels. The assignment of fishing effort levels was based on the fishing effort distribution in the area calculated from Vessel Monitoring System (VMS) data and the existence of two Fishing Protected Zones in the Menorca Channel. Biological samples were collected from 39 beam trawl stations, sampled during a scientific survey on April 2019. We compare the diversity, composition, and density of the epibenthic flora and fauna, together with the rhodoliths coverage and the morphology of the main species of rhodoliths of four areas subjected to different levels of bottom trawl fishing effort, including one that has never been impacted by trawling. Our results have shown negative impacts of bottom trawling on rhodoliths beds and the first signals of their recovery in areas recently closed to this fishery, which indicate that this is an effective measure for the conservation of this habitat of special interest and must be included in the management plan required to declare the Menorca Channel as a Special Area of Conservation.

The scientific exploration of Mallorca Channel seamounts (western Mediterranean) is improving the knowledge of the Ses Olives (SO), Ausias March (AM), and Emile Baudot (EB) seamounts for their inclusion in the Natura 2000 network. The aims are to map and characterize benthic species and habitats by means of a geological and biological multidisciplinary approach: high-resolution acoustics, sediment and rock dredges, beam trawl, bottom trawl, and underwater imagery. Among the seamounts, 15 different morphological features were differentiated, highlighting the presence of 4000 pockmarks, which are seafloor rounded depressions indicators of focused fluid flow escapes, usually gas and/or water, from beneath the seabed sediments. So far, a total of 547 species or taxa have been inventoried, with sponges, fishes, mollusks, and crustaceans the most diverse groups including new taxa and new geographical records. Up to 29 categories of benthic habitats have been found, highlighting those included in the Habitats Directive: maërl beds on the summits of AM and EB, pockmarks around the seamounts and coral reefs in their rocky escarpments as well as fields of Isidella elongata on sedimentary bathyal bottoms. Trawling is the main demersal fishery developed around SO and AM, which are targeted to deep water crustaceans: Parapenaeus longirostris, Nephrops norvegicus, and Aristeus antennatus. This study provides scientific information for the proposal of the Mallorca Channel seamounts as a Site of Community Importance and for its final declaration as a Special Area of Conservation.

Megalopas of 15 brachyuran crab species collected in the open sea plankton, and unknown until now, were identified using DNA barcodes (COI and 16S rRNA). Specimens belonging to the families Portunidae, Pseudorhombilidae and Xanthidae (Crustacea, Decapoda, Brachyura), and corresponding to the species Achelous floridanus, Arenaeus mexicanus, Callinectes amnicola, C. arcuatus, C. ornatus, C. toxones, Charybdis (Charybdis) hellerii, Portunus hastatus, Thalamita admete, Scopolius nuttingi, Etisus odhneri, Liomera cinctimanus, Neoliomera cerasinus, Pseudoliomera variolosa, and Williamstimpsonia stimpsoni, are described and illustrated, and compared with other congeneric species previously described. We also provide a new geographical record for N. cerasinus and the most remarkable features for each species.

Small crabs belonging to the family Pinnotheridae are characterized by living inside mainly bivalves. In European waters the recently-described pea crab Pinnotheres bicristatus increased to five the known number of pinnotherid species. The know distribution of the recently-described pea crab Pinnotheres bicristatus encompassed the area between the Gulf of Cádiz (NE Atlantic) and the western Alboran Sea (SW Mediterranean). The species was so far reported to occur in the pallial cavity of the common saddle oyster, Anomia ephippium, between 11 and 52 m depth. During two years, a total of 43 specimens of Pinnotheres bicristatus were collected in two different projects/surveys along the Mediterranean coasts of the Iberian Peninsula, thus enlarging its known occurrence to the eastern Alboran Sea and the NW Mediterranean, at depths between 37 and 71 m. We also report a new bivalve host for the species, the flat oyster Ostrea edulis, and population structure information of these new records. As a conclusion, this study considerably extends both in latitude and longitude, as well as in depth, the known geographical distribution of P. bicristatus.

The first record of the ophiuroid family Ophiohelidae from the Mediterranean Sea is reported. It consists of the description of the new record ofOphiomyces grandisfrom the Mallorca Channel seamounts in the Balearic Islands, western Mediterranean, where it shows high abundances. We present both the morphological description of the individuals collected and, for the first time, the cytochrome oxidase subunit I (COI) sequence of this species. The morphological traits of our specimens match the available descriptions ofO. grandis. On the other hand, molecular analyses show a large genetic distance betweenO. grandisandOphiomyces delata, the two species being very similar morphologically. Despite the high abundances ofO. grandisreported here, previous surveys in the Mallorca Channel seamounts using ROV did not detect it, emphasizing the importance of beam trawl sampling to improving the biodiversity description of these geomorphological sea bottom features.