On the Occurrence of the Blunthead Puffer, Sphoeroides pachygaster (Osteichthyes: Tetraodontidae), in the Strait of Messina (Central Mediterranean)

The blunthead puffer Sphoeroides pachygaster (Müller & Troschel, 1848) is widely distributed in tropical and temperate waters on both sides of the Atlantic Ocean [1, 2]. The species was reported from New England to Southern Brazil [3], off the Eastern Atlantic in Irish Waters [4], in the Bay of Biscay [5, 6] and off Portugal [7]. S. pachygaster was frequently reported in the south of the Strait of Gibraltar, from Morocco, Senegal [8], to the Gulf of Guinea [1, 9]. The species is known in the Mediterranean [10–12] where the northernmost extension range of the species was the Adriatic Sea [13]. In the Tunisian marine waters, the species was observed by Bradaı̈ [14] and recently by Chérif et al. [15], where a substantial population seems to be at present definitively established. In the Italian Seas S. pachygaster was found in the Southern Tyrrhenian Sea [16], Sicilian Channel [17], Ionian Sea [18], Adriatic Sea, and Northern Tyrrhenian Sea [13, 19].


Introduction
The blunthead puffer Sphoeroides pachygaster (Müller & Troschel, 1848) is widely distributed in tropical and temperate waters on both sides of the Atlantic Ocean [1,2].The species was reported from New England to Southern Brazil [3], off the Eastern Atlantic in Irish Waters [4], in the Bay of Biscay [5,6] and off Portugal [7].S. pachygaster was frequently reported in the south of the Strait of Gibraltar, from Morocco, Senegal [8], to the Gulf of Guinea [1,9].
The species is known in the Mediterranean [10][11][12] where the northernmost extension range of the species was the Adriatic Sea [13].In the Tunisian marine waters, the species was observed by Bradaï [14] and recently by Chérif et al. [15], where a substantial population seems to be at present definitively established.In the Italian Seas S. pachygaster was found in the Southern Tyrrhenian Sea [16], Sicilian Channel [17], Ionian Sea [18], Adriatic Sea, and Northern Tyrrhenian Sea [13,19].
Information available strongly supports the general opinion which considers S. pachygaster a recent immigrant, probably undergoing a fast diffusion eastwards [16,17] even though Relini and Orsi Relini [20] speculated on the possibility of a previous presence of the species within the Mediterranean on the basis of old ichthyological illustrations.
The aim of this paper is to point out that the species is present in the area.With the present note, the blunthead puffer can now be added to the Strait of Messina fish checklist.

Material and Methods
On 15 March 2012 in the Strait of Messina (Sicily), one specimen of Sphoeroides pachygaster was caught by a fisherman (Figure 1).The specimen was weighted to the nearest gram and measured to the nearest millimetre.The morphometric measurement and meristic counts were performed according to Ragonese et al. [17].
The specimen was photographed and preserved in the ichthyological collection of the Institute for Marine Coastal Environmental (IAMC) of the National Council of Research (CNR) in Messina (Italy).

Results and Discussion
The first finding of Sphoeroides pachygaster in the Strait of Messina was an adult male that weighted 461.5 g (Figure 2).The morphometric measurement with percents of total length (% of TL) and meristic counts are shown in Table 1.
Identification was made by skin completely smooth with total lack of scales, spines, and body plates; one lateral line  on each side convoluted; body inflatable, with large head and snout rounded; with beak-like jaws with two large teeth on each jaw forming a dental plate with entire cutting edge (Figure 3); eyes big and oval with a flat interorbital space; dorsal fin single placed in front of the similar-shaped anal fin, pelvic fin absent and caudal fin truncated or slightly concave; colour greyish on dorsal surface with brownish spots; belly whitish pale grey; caudal fin base dark.
Morphology, colour, morphometric measurements, and meristic counts of this blunthead puffer agree with previous descriptions [3,11,12,17,21].The number of alien fish species increased recently in the Black Sea-Mediterranean Basin because of the opening of the Suez Canal, climate change, and international shipping activities [22].Introduction of Alien species to new ecosystem is considered to be a major threat to its biodiversity, structure, and function [23,24].More than 790 alien species have been introduced to the Mediterranean Sea, most of which are benthos and fish species [25].Movements of species in relation with global warming may increase spatial overlapping between exotic and endemic species, which is a critical issue for the conservation of biodiversity.Marine biological invasions are becoming a reality with sometimes devastating effects [26].At the same time, it is important to study the genotypic changes of new populations driven by natural selection through the interactions with indigenous populations and in response to the new abiotic environment.Records of the Indo-Pacific and Atlantic fish species from the Mediterranean areas increase continuously [27].In particular in the Ionian Sea S. pachygaster, after its first occurrence in 1991, showed a significant increase with time and there is now a steady population [28].
This note provides information about a new discovery of Sphoeroides pachygaster.In this Mediterranean area all records and stranding due to upwelling phenomena (typical of the Straits of Messina) should be reported.

Figure 1 :
Figure 1: Area of discovery: Strait of Messina.

Figure 2 :
Figure 2: S. pachygaster captured in the Strait of Messina (Central Mediterranean Sea).

Table 1 :
Morphometric measurements (in mm and F% of TL) and meristic counts of S. pachygaster caught in the Strait of Messina.