New records of amphipod crustaceans along the Israeli Mediterranean coast, including a rare Mediterranean endemic species, Maera schieckei Karaman & Ruffo, 1971

Abstract Background A survey has been carried out at four Israeli rocky sites to evaluate the diversity of the amphipod fauna on various hard substrates, still scarcely monitored, as potential pabulum for amphipod crustacean species. New information A survey of shallow rocky reefs along the Mediterranean coast of Israel recovered 28 species and integrated the Amphipoda checklist for the country ofIsrael with 12 newly-recorded species. Such renewed national list includes Maera schieckei Karaman & Ruffo, 1971, a rare species endemic to the Mediterranean Sea, recorded here for the first time from the southern Levant Basin. The species, described from specimens collected in the Tyrrhenian Sea in 1970, has been only recorded eight times within the whole Mediterranean Sea. A revision of the bibliography on the distribution and ecology of M. schieckei showed that, although mentioned only for the western Mediterranean basin by some authors, it is listed in the checklist of amphipods of the Aegean Sea and neighbouring seas and has been found in the eastern Mediterranean basin since 1978. Maera schieckei was rarely found in the Mediterranean, one of the most studied marine biogeographic region as concerns the amphipod fauna; and the species seems to prefer bays or gulf areas. The role of updating and monitoring faunal composition should be re-evaluated.


Introduction
The link between the variation of biodiversity over time and the change of marine environment detected nowadays is becoming a challenge for different taxonomists' communities, which aim to re-evaluate the role of taxonomy in actual and historical collections, mainly if selectively focused on specific taxa , Beermann and Franke 2011, Hawkins et al. 2013, Pyke and Ehrlich 2010, Scipione 2013, De-La-Ossa-Carretero et al. 2010, Costello et al. 2010, Costello 2020. The updating of checklists (Sorbe et al. 2002, Christodoulou et al. 2013) is now becoming the prerequisite for ecological and monitoring studies, also in the light of invasive alien species monitoring (Cao et al. 2003, Servello et al. 2019).
Many habitats often represent a sink for invasive alien species, unknown species (not yet described) or rare species. Those can be the artificial (Bonifazi et al. 2018) or biogenic (Plicanti et al. 2016, Bertocci et al. 2017) hard substrates, which can significantly influence the faunal composition especially in countries, such as Israel, where sandy and muddy bottoms show a large extension along the coast. In some cases, such scattered habitats create the favourable conditions for settlement and successive establishment, facilitating the dispersal of the species also over long distances. An example was the vermetid platforms habitat whose shape and structure favoured the settlement and successive increasing density of the lessepsian mussel Brachidontes pharaonis (P. Fisher, 1870) (Sirna Terranova et al. 2006, Rilov et al. 2004, now widespread in the eastern and central Mediterranean (Servello et al. 2019).
In the light of that, a survey has been carried out at four Israeli rocky sites to evaluate the diversity of the amphipod fauna on variegate hard substrates (e.g. rocks, bryozoans, sponges, seaweeds, coralligenous, plastic objects etc.) as potential pabulum for an establishment of amphipod crustacean species, still scarcely monitored in scattered areas of the eastern Mediterranean Sea , Sorbe et al. 2002. In European aquatic ecosystems, including the coastal Mediterranean ones, where biodiversity is changing due to climate change and the invasion of alien species, such a ubiquitous animal group, as amphipods, plays a crucial role in detecting such changes and deserves relevant attention as fundamental tool in monitoring biodiversity (Borja et al. 2003).
Telson nearly as long as broad, deeply cleft. Telson lobes bifurcate with 2 long distal spines (of unequal length) and 3 plumose setae.

Notes
Five species of Maera have been recorded in the Mediterranean Sea: M. grossimana (Montagu, 1808), M. hirondellei Chevreux, 1900, M. pachytelson Karaman & Ruffo, 1971, M. schieckei and M. sodalis Karaman & Ruffo, 1971 (accessed at http:// www.marinespecies.org/amphipoda on 05-04-2020). Maera schieckei is distinguished from congeneric Mediterranean species by the presence of a median U-shaped excavation in the palm of the second gnathopods and several teeth on the posterodistal corner of third epimeral plate (character not always appreciable) (Fig. 2B,  C, D). The genus Maera, erected by Leach (1814), is one of the oldest amphipod genera, which has undergone extensive revision, throughout which Maera schieckei has maintained its original name and taxonomic position.
The specimens described in this study corresponds to the morphology of Maera schieckei as described by Karaman and Ruffo 1971 and available also in Ruffo (1982).

Discussion
In spite of their important ecological role within benthic ecosystems, hard bottom amphipods were rarely investigated on the Mediterranean coast of Israel compared with the soft-bottom ones , Sorbe et al. 2002.
Of the 28 amphipod species identified from the rocky reefs, 16 had been previously recorded (Sorbe et al. 2002) and 12 are new records for Israel (see Table 1), whereas 19 and 20 had been recorded off Cyprus and the Levantine coast of Turkey, respectively , Kocataş et al. 2001 and references herein). Bemlos leptocheirus (Walker, 1909), occasionally recorded as Mediterranean alien species and Synchelidium longidigitatum (Ruffo, 1947), an endemic Mediterranean species, are the first records for the whole Levantine Sea.
Currently, the Mediterranean Sea suffers a high anthropogenic impact due to warming water, internal and external boat traffic and pollution (Galil 2000, Occhipinti-Ambrogi 2007. The effects of these activities can be assessed by the spread of some species, for which the hard substratum can be a point of the pathway. Several studies focused on the spread of alien species (Marchini and Cardeccia 2017, Servello et al. 2019, Ulman et al. 2017) and do not often consider the spread of the autochthonous species as an additional significant signal of changing.
The value of the Mediterranean basin in relation to its role as a hotspot of endemisms can be enhanced also by the capture of rare species. Maera schieckei is here identified for the first time along the Israeli coast and it is the most south-eastern record of the species in the Mediterranean Sea (Fig. 2). This rare Mediterranean endemic species has only been collected from a few locations, with a low number of specimens found only four times in the western basin and three times in the eastern basin (Fig. 3). The zoogeography of M. schieckei is scarcely known and, in some cases, inaccurate. Though Christodoulou et al. (2013) recently reported the species only present in the western Mediterranean basin and it was not listed in the check-list of the north Aegean Sea (Stefanidou and Voultsiadou-Koukoura 1995) and Israel (Sorbe et al. 2002), this species has been identified in the eastern Mediterranean basin since 1978.
Even if this species occurred within a wide geographical range (approximatively all over the Mediterranean basin), in a wide habitat specificity (different types of substrate), it was recorded only in bay or gulf areas, often polluted and degraded areas due to the presence of commercial harbours (see references in Fig. 3); and it remains uncertain if a small-sized crustacean can spread for hundreds of kilometres along the Mediterranean basin and be recorded only few times. Studies on its life history needs to better understand dispersal and establishment. Data suggest it to be an opportunistic species. It is noteworthy to mention Ferrario et al. (2017) who evaluated the role of harbours in spreading non-native species; they can be probably significant in driving the range expansion of autochthonous species as well.
Its small populations make the species being attributed to a rarity with wide geographical range and low frequency of occurrence (Rabinowitz 1981)  A recent estimate fixes the number of benthic amphipod species in the Mediterranean basin at 449 ). Yet, there is no doubt that this number is an underestimate and that we lack information for wide swathes of the region as research efforts vary greatly along the coasts of the Mediterranean and even amongst particular habitats within wellstudied areas , Curatolo et al. 2013. A cursory examination of recent publications reveals the magnitude of the gaps. The number of species and genera new to science, some described from material collected in well-studied areas, confirm that the actual number of Mediterranean amphipods is a function of search effort and taxonomic expertise (Coleman 2015). For instance, a study along the Algerian coast listed 33 new records (Bakalem et al. 2014) and, even along the Spanish coast, a study of the shallow soft bottom fauna listed five new records and 14 second records (De-La-Ossa-Carretero et al. 2010). Records of native 'rare' species, whose role in the ecosystem and importance in bioassessment is still debated (Cao et al. 2003), accrue as well (Scipione 2013). The Marine Science Framework Directive, with its descriptors for 'good environmental status' (Review of the Commission Decision 2010/477/EU concerning MSFD criteria), opens new perspectives to monitor, manage and protect the marine environment. The three criteria for the assessment of any species are distribution, population size and population condition and special attention is called to the "integrated understanding of the distribution, extent and condition of their habitats … to make sure that there is a sufficiently large habitat to maintain its population, taking into consideration any threat of deterioration or loss of such habitats." During an era of intensification of anthropogenic activities which drive complex and fundamental changes in the Mediterranean Sea (European Environment Agency, EEA 2015), it is important to strengthen and augment the study of the faunal diversity of the Mediterranean Sea -a sea notable for its endemisms.