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First record of Europe's smallest marine fish Lebetus guilleti (Gobiidae) in the Italian seas

Published online by Cambridge University Press:  27 January 2015

Francesca Riolo  and
Federico Betti
Francesca Riolo*
Affiliation:
Mappamondo GIS, Via Rubens 3, 43123 Parma, Italy
Federico Betti
Affiliation:
AMP Isola di Bergeggi, Via De Mari 28/D 17028Bergeggi, SV, Italy
*
Correspondence should be addressed to: F. RioloMappamondo GIS, Via Rubens 3, 43123 Parma, Italy email: francesca.riolo@mappamondogis.com

Abstract

The first record of Lebetus guilleti for the Italian seas is reported here. The finding is based on photographic records of specimens located in shallow waters off the Conero Promontory (An) along the Adriatic coast of Italy. This record expands the distribution range of this species in the Mediterranean and moves its southern limit in the Adriatic Sea 170 km further south, adding to the suspicion that the distribution of this cryptic species might be wider than previously described. Recreational SCUBA diving focused on biodiversity observations and underwater photography proved instrumental again in providing information about the presence and distribution of marine fauna, including the most easily overlooked species.

Keywords

Mediterranean SeaLebetus guilletiGobiidaefirst recordAdriatic SeaConero

Information

Type
Research Article
Information
Marine Biodiversity Records , Volume 8 , 2015 , e12
Copyright
Copyright © Marine Biological Association of the United Kingdom 2015 

INTRODUCTION

Guillet's goby, Lebetus guilleti, is a very small marine fish (maximum observed length 24 mm; Maitland & Herdson, Reference Maitland and Herdson2009), belonging to the family Gobiidae, and was first described by Le Danois in Reference Le Danois1913 based on a specimen collected off the shores of Roscoff in Brittany. Le Danois attributed the specimen to the sub-species Lebetus scorpioides guilleti. It was only recognized as a species in 1971 (Miller, Reference Miller1971). Very few sightings have been recorded since then, especially of living specimens in their habitat. The first record in the Mediterranean Sea was made in 1979 at Banyuls-sur-Mer in France (Zander, Reference Zander1982). The first records in the eastern Adriatic Sea were made in Croatia in 1999 near the towns of Selce and Klenovica and in 2002 near the town of Rovinj (Herler & Kovačić, Reference Herler and Kovačić2002).

Other living specimens were observed on the south coast of England, along the western shores of the Scottish Highlands (Baldock & Kay, Reference Baldock and Kay2012) and at a site in the Shetlands Islands (Hope & Shucksmith, Reference Hope and Shucksmith2010).

Figure 1 shows the current known distribution of Lebetus guilleti, including the areas inferred by Miller from museum specimens, and the larvae and post-larvae observations recorded by Demir & Russell (Reference Demir and Russell1971), Rè (Reference Rè1981), Moyano & Hernandez-Leon (Reference Moyano and Hernandez-Leon2009) and Rodriguez et al. (Reference Rodriguez, Gonzalez-Nuevo, Gonzalez-Pola and Cabal2009).

Fig. 1.

Map displaying the current known distribution and the new sighting of Lebetus guilleti, indicating the type of specimen linked to the record (living adult, museum specimen, post-larval and larval stage).

MATERIAL AND METHODS

The Conero Promontory divides the Upper and the Middle Adriatic Sea, located about 20 km south of the city of Ancona, along the Italian shores. The area is characterized by some peculiar environmental constrains; in particular, the small extension of rocky bottoms of the Conero Promontory breaks the continuity of the Adriatic sandy and muddy coasts, creating important stepping stones for larval dispersal. Moreover, the area is characterized by very shallow waters, a high sedimentation rate and an extremely wide annual range of temperatures (Di Camillo et al., Reference Di Camillo, Coppari, Bartolucci, Bo, Betti, Bertolino, Calcinai, Cerrano, De Grandis and Bavestrello2012). Due to the peculiarity of the habitat, the area is populated by a large number of animals, in particular Mollusca and Crustacea, and because of this it can be considered a biodiversity hot-spot for this region. Additionally, most of the Conero fauna is composed of species that are considerably rare in other areas of the Mediterranean Sea (Betti, Reference Betti2011). Many species of gobies, typical of both rocky and sandy/muddy bottoms, are present.

A review of the literature regarding the distribution of Lebetus guilleti was performed to better describe the novelty of information provided by this new record.

The record presented here is based on the examination of underwater photographs obtained during five SCUBA dives that took place between 5 June 2014 and 12 June 2014 at the ‘Due Sorelle (Two Sisters)’ diving site located at 43.5482°N 13.6282°E. The depth at the location where the specimens were observed was 8 m and the bottom temperature was 21°C.

The camera equipment used was a Nikon D7000 in Isotta housing, equipped with a Nikon Nikkor 60 mm micro lens and two Sea & Sea external strobes for the photo shown in Figure 2A and a Canon G12 in Canon WP-DC34 housing for the photo shown in Figure 2B.

Fig. 2.

Lebetus guilleti photographed at the Two Sisters diving site off the Conero Promontory in the municipality of Sirolo (An), Italy: (A) on 7 June 2014; (B) on 9 June 2014.

RESULTS

An isolated specimen of Lebetus guilleti was observed on gravel (legit Francesca Riolo and Federico Betti) during five dives, but there is no sufficient evidence to state if the sightings were of the same or multiple specimens. All specimens were observed within a radius of 3 m at the same location of the diving site. Since the specimen was not identified as the rare and little known Guillet's goby at the time of the dives, no effort was put into searching for additional specimens in the surrounding area.

Specimens were very well camouflaged in the yellowish gravel and coarse grained sand present in the area, and it was only their rapid movements when disturbed that allowed the divers to notice their presence and take photographs. After being disturbed, the fish rested on the bottom, trusting in their camouflage abilities. The size of the specimens was between 8 and 12 mm. The key features that allowed the identification of a specimen included the wide white band on the caudal peduncle, the black vertical bars on the side of the body, the small and white D1 dorsal fin, the six orange bands on the D2 and the bright blue spot on the upper anterior part of the D2 (Figure 2). The presence of the blue spot on the D2 and the absence of the small green spot on the D1 identified the specimens in the photographs as males (Herler & Kovačić, Reference Herler and Kovačić2002). The six orange bands on the D2 easily distinguish the Lebetus guilleti from the closely related Lebetus scorpioides, which is characterized by four bands on the D2 (Miller, Reference Miller1963, Reference Miller1971; Herler & Kovačić, Reference Herler and Kovačić2002).

DISCUSSION

This is the first record of Lebetus guilleti in the Italian seas, further expanding the known distribution range of this species in the Mediterranean, and moving its known southern limit in the Adriatic Sea 170 km south. The habitat in which this record was made – coarse-grained sand/gravel – is in accordance with the habitat of previous records (Herler & Kovačić, Reference Herler and Kovačić2002; Hope & Shucksmith, Reference Hope and Shucksmith2010). The depth recorded is within the previously observed range 2–30 m. It would be interesting to know the temperature range of tolerance for this species and this record provides an additional reference for the upper limit.

Due to its small size, cryptic behaviour and camouflage coloration, it is very likely that the presence of Lebetus guilleti on the Italian Adriatic coast has been overlooked until now. For this reason, the authors believe that this is not a climate-change-related range expansion, but rather a new record related to the widening of observations made possible by recreational SCUBA diving, more financially and technically accessible digital underwater photography as well as an increase in the interest and contributions of ‘non-experts’ to marine flora and fauna biodiversity assessment.

Data collected by recreational divers has great potential in complementing the surveys carried out by experts for the identification of specific taxa and for filling the gaps that are highlighted in the literature, where it is pointed out that the distribution of rare species reflects, in some cases, the spatial distribution of the experts studying them (Giangrande & Licciano, Reference Giangrande and Licciano2004).

The Conero Promontory area is becoming an increasingly popular destination, thanks to its uniquely rich and diverse invertebrate and small vertebrate fauna. Some diving business ventures have developed their operations to focus on the careful observation of micro fauna rather than the more common ‘big fish’ or ‘deep dive’ target. This type of diving approach attracts recreational divers who have a particular interest in marine biology, biodiversity and photography. This trend has resulted in the first record of Lebetus guilleti, currently Europe's smallest marine fish. Further surveys are required to know if its presence is restricted to the biodiversity-rich Conero Promontory area or if it is more widespread along the Adriatic coast.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the help of the Centro Sub Monte Conero for providing logistic support for the dives. The authors would like to thank Leslie Whaylen Clift for proof reading the manuscript and above all for inspiring people in the observation and discovery of the marine fish world.

References

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Figure 0

Fig. 1. Map displaying the current known distribution and the new sighting of Lebetus guilleti, indicating the type of specimen linked to the record (living adult, museum specimen, post-larval and larval stage).

Figure 1

Fig. 2. Lebetus guilleti photographed at the Two Sisters diving site off the Conero Promontory in the municipality of Sirolo (An), Italy: (A) on 7 June 2014; (B) on 9 June 2014.