Typhlocirolana longimera sp . n . ( Crustacea , Isopoda , Cirolanidae ) from north-western Algerian ground waters with notes on Algerian Typhlocirolana

A new species of hypogean cirolanid isopod, Typhlocirolana longimera sp. n. is reported and described from a region located in north-western Algeria. Typhlocirolana longimera sp. n. can be distinguished from all other species of the genus especially by the peculiar shape of the merus of pereiopod I longer than in any other Typhlocirolana species, and for the presence of 6 molariform robust conical robust setae, the bottle shape of uropods and the aesthetasc formula of flagellum in antennulae. The presence in the same region of the two already known species T. fontis and T. gurneyi is also discussed.

One of the most interesting taxa of cirolanid isopods is the western Mediterranean stygobitic genus Typhlocirolana Racovitza, 1905.Widely spread in the area, it has colonized the continental groundwater of Sicily, Iberian Peninsula, Balearic Islands, Tunisia, Algeria and Morocco with several species (Racovitza 1912, Monod 1934, Boutin et al. 2002, Baratti et al. 2004).The genus occurs in the western Mediterranean with ten described species and several as yet undescribed species, whose phylogenetic relationships have been investigated (Baratti et al. 2004) and still need deeper investigation, especially after the recent transfer of the species T. leptura Botosaneanu et al. 1985 to a new genus Botolana Coineau and Boutin, 2015 (Coineau and Boutin 2015).
During a survey of the subterranean waters of north-western Algeria, several specimens of the Typhlocirolana were collected from several wells of the region.Most of the specimens collected in one of the wells were attributed to the already described species T. fontis (Gurney 1902) and T. gurneyi Racovitza, 1912.
The aim of this paper is to describe a new species of the North African Typhlocirolana and comment on the presence of other Algerian species of the genus.

Methods
The specimens were collected (Fig. 1) using Cvetkov's net (Cvetkov 1968) and baited traps.Dissected specimens were pencil drawn and the figures composed using the GIMP 2.8.14 program (Montesanto 2015).
Antennula (Fig. 2e): Antennula short, reaching mid-length of pereonite 1. Flagellum shorter than peduncle with 6 articles, with few simple setae, aesthetascs present from second to fourth segment.Aesthetascs formula is 022210 in male and 012220 or 012210 or 011110 in female.
Antenna (Fig. 2d): Antenna reaching the distal margin of pereonite 5, flagellum extending to posterior part of pereonite 4. Flagellum nearly 2 times longer than peduncle, with about 32 segments in male and 35 in female.Segment length regularly decreasing from the base to the apex; all segments with 5 to 9 setae, mainly long and simple setae.1-3 long plumose setae in each of segment number 4 and 5 of peduncle, and one tufted setae in segment number 4 of peduncle.
Maxillae (Fig. 3c): Outer lobe with 3-4 barbed setae on one side in the distal part.Inner lobe with 3-4 similar setae.Basal endite with 9 setae of different lengths, delicately plumose on the two sides and at the tip.Propod with a short simple setae in the middle of distal margin.
Maxilliped (Fig. 3e,f): Palp with 5 articles provided with setae and a well-developed endite with only one coupling hook.Article 1 with one inner simple setae at apex; article 2 with 2 on outer corner margin and 6 on inner margin; article 3 with 4 setae on outer margin and 14-18 on inner margin; article 4 with 2 setae on outer margin and 12 on inner margin (2 of which are plumose in one side); article 5 with 13-17 distal setae, all setae are simple excepted 4-5 which are plumose in one side.Endite with single hook and 4 plumose setae.
Pereiopod 1 (Fig. 4a) Basis with one tufted setae and one simple setulae on outer margin.On inner margin, 2 medial small setae and 2 small setae on distal angle.Ischium 5 setulae, 3 of which on inner margin and 2 distal near outer corner and one spine on inner distal corner.Merus with inner margin elongate, depassing carpus and reaching the 2/3 length of propodus , with 3 setulae on distal outer angle.Inner margin with 6 molariform robust conical robust setae and 2 short, robust setae with additional setule and 1 long simple setae.This armature is constant and similar in male and female.Two to three simple small setae are close to the three proximal molariform robust setae.Carpus with 2 simple setae and 1 single spine with additional setula on distal inner corner.Propodus with inner margin proximally crenulate, with 2 distal spines with additional setula (one which is stronger) and a bunch of 5 apical setae (one of which is barbed on one side).Two simple setae at distal corner on outer margin.One setula on outer side.Dactylus with 5 short setae and 1 spine with additional setula on distal inner corner, 4 subdistal setae on lateral surface.
Pereiopods 2-7 (Fig. 4b-g) similar to each other and progressively growing in length from 2 to 7. Pereopods 2 and 3 exhibit the propodial organ in both males and females.These pereiopods differ by their chaetotaxy, bearing 2 to 5 tufted setae   on outer margin of basis; 4-5 along the margin of P2-P3, 2 proximal setae on P4, 2 proximal with 1 distal setae on P5, 4 setae along margin of P6 and 3 proximal setae with penial processes on P7 and about ¼ the length of the same.
Uropods (Fig. 2f) Sympod subtriangular.Lateral margin with 3 spines with additional setula, 1 medial and 2 on distal corner.Two small and simple setae on the outer margin.Seven to eight plumose setae distal on mesial margin in male and 8-12 in female.Exopod styliform, shorter than endopod, regularly slender from base to apex, with 2 strong robust setae with additional setula on lateral margin and 1-2 on mesial margin accompanied by 1 to 2 long simple setae and 1-2 small simple setae; outer margin with 1 small proximal spine with additional setula and one line of 3-4 small simple setae.Apex with about 13 long simple setae of different length.Endopod bottle shaped, clearly wider than exopod.Slightly longer than exopod, with 6 plumose setae on internal margin in male and 5-8 in female and 2-3 strong robust setae with additional setula.Nine tufted setae on external margin grouped by 2 or 3 proximally and distally.Apex bearing about 12 simple distal setae of different lengths.
Remarks.Typhlocirolana longimera is different from all other Typhlocirolana species described by the combination of the following characters: -The peculiar shape of pereiopod 1 merus, which is longer than in any other species, depassing carpus and reaching the 2/3 length of propus.-The presence of 6 molariform conical robust setae and 2 short strong robust setae usually 4 molariform robust setae; -Propodus of pereiopod I with only 2 distal robust setae with accessory seta on internal margin, which is proximally crenulated and devoid of setae.-The bottle shape of uropods; -The chaetotaxy of pleopods1-5 more abundant.

Differential diagnosis with other materiel examined.
Based on the general morphological aspect, as well as some characters, Typhlocirolana longimera sp.n. exhibits the greatest affinities with T. fontis and T. haouzensis Boutin, Boulanouar, Coineau & Messouli, 2002.However there is a mix of characters approaching T. longimera to several other Typhlocirolana species.
In addition to the main characters that make the difference with the other species of the genus Typhlocirolana, as cited above, T. longimera differs greatly from the others according to the aesthetasc formula of flagellum in antennulae: 122222222212 in T. buxtoni Racovitza, 1912, 12222212 in T. fontis, 12222212 in T. gurneyi, 121221 in T. ichkeuli Ghlala, Della Valle & Messana, 2009, 22210 in T. rifana Margalef, 1953.Dentition and number of robust setae in propodus of pereopod I: in T. gurneyi not toothed with 2 or 3 short strong robust setae, in T. buxtoni not toothed with 3 strong robust setae, in T. fontis we don't have information, in T. haouzensis not toothed with 3 medio distal robust setae, in T. ichkeuli not toothed with 3 robust setae.
Propodial organ is present in both male and female in T. longimera as well as T. buxtoni, but it is present only in the male in T. fontis, T. gurneyi, T. haouzensis and T. tiznitensis Boulal, Boulanouar & Boutin, 2009, while, it is absent in T. ichkeuli.
The basal palp article of the mandible in Algerian species (T.buxtoni, T. fontis and T. gurneyi) including T. longimera, exhibits a strong plumose seta.On the contrary this article is bare in Moroccan (T.haouzensis and T. tiznitensis) and in the Tunisian species T. ichkeuli.
Article III of the mandibular palp has 30 plumose setae in the Algerian species and only 13-16 in the Moroccan one.Whereas, T. longimera has an intermediate position with 9-11.
A complete transversal suture is present in pleopod 3, 4 and 5 in Moroccan (T.haouzensis and T. tiznitensis) and in the Tunisian species (T.ichkeuli), while it is present only in pleopod 4 and 5 in Algerian species (T.buxtoni, T. fontis and T. gurneyi) including T. longimera.

Discussion
The first surveys of the underground aquatic fauna in Algeria run by Gurney (1908) and Racovitza (1912), lead to the discovery of three species of Typhlocirolana: T. fontis, T. gurneyi and T. buxtoni.However, Monod (1930, 1934) and Nourisson (1956), argued the status of the two species, T. fontis and T. gurneyi, suggesting they might be a single species.These authors underline the great variability of the characters used by Racovitza (1912).Typhlocirolana buxtoni has been maintained as an independent species probably by the presence of propodial organ in the two sexes (Por 1962).Later, other authors suggest to maintain the separation between the three Algerian species (Botosaneanu et al. 1985, Boutin et al. 2002).We do agree about this point, because we have not enough arguments to separate the three species.On the other hand, we need other new observations for an exhaustive comparison.
The history of Typhlocirolana evolution and colonization of subterranean waters, such as that of several other stygobitic crustaceans (Baratti et al. 2010), is the result of multiple vicariance events, which happened in the Mediterranean basin in the last 90-15 MYA.In particular the western Maghreb region has experienced extensive marine ingressions in different periods that allowed a connection between the Tethyan basin and the Atlantic Ocean.The articulated palegeographic history of the region resulted in a complex of species strictly related morphologically and genetically whose position is not easy to elucidate (Boutin et al. 2002, Baratti et al. 2004, 2010, Ait Boughrous et al. 2007, Boulal et al. 2009).
The Algerian situation is rather complicated and will need an accurate revision of the taxa both morphological and molecular.As has been pointed out by other authors (Nourisson 1956), many of the characteristics examined do not correspond to the descriptions that have been given or are common to several species.

Figure 1 .
Figure 1.Map showing collection localities of the genus Typhlocirolana from the north-western Algeria.