Cymbasoma mediterranea, Suárez-Morales & Goruppi & de Olazabal & Tirelli, 2017

Suárez-Morales, Eduardo, Goruppi, Alenka, de Olazabal, Alessandra & Tirelli, Valentina, 2017, Monstrilloids (Crustacea: Copepoda) from the Mediterranean Sea (Northern Adriatic Sea), with a description of six new species, Journal of Natural History (J. Nat. Hist.) 51 (31 - 32), pp. 1795-1834 : 1815-1817

Cymbasoma mediterranea sp.nov.

( Figure 7 (a – h))

Material examined

Adult holotype female from station 8 ( Figure 1 ), harbour of Trieste, North Adriatic Sea, specimen partially dissected, appendages mounted on slide in glycerine, sealed with Entellan®. Date of collection: 20 July 2016. Slide deposited in ECO-CHZ-009525.

Description of adult female

Body elongated, slender ( Figures 7 (a, b)); body length of holotype female 1.04 mm. Cephalothorax 0.61 mm long, representing 58.7% of total body length. Midventral oral papilla located at 14% of cephalothorax length. Pair of large ocelli present, pigment cups moderately developed, medially separated by less than half of one eye diameter, pigmented only on inner margin; ventral cup slightly larger than lateral cups ( Figure 7 (d)). Cephalic area with strongly produced ‘ forehead ’, ornamented with relatively deep ridges on anteriormost end ( Figure 7 (c, d)); frontal sensilla absent. Cephalic section not constricted, but narrower than medial part of cephalothorax ( Figure 7 (b, c)). Paired ventral papilla-like processes between antennule bases with few adjacent transverse striae (arrow in Figure 7 (e)). Nipple-like processes on preoral surface surrounded by striae arranged in incomplete concentric pattern ( Figure 7 (c)).

Urosome consisting of fifth pedigerous somite, genital double-somite and anal somite, together representing 18% of total body length. Relative lengths of urosomites (fifth pedigerous, genital-double and anal somite) as: 34.2: 42.4: 23.4 = 100, respectively. Fifth pedigerous somite subrectangular, with shallow striation on dorsal surface ( Figure 7 (g)). Genital double-somite with globose anterior part; somite with anteroventral protuberance visible in lateral view ( Figure 7 (g, h)), with shallow ventral suture line and small rounded posterolateral process (arrow in Figure 7 (h)). Caudal ramus subquadrate, armed with three subequally long, sparsely setulated caudal setae ( Figure 7 (g)). Ovigerous spines paired, relatively long (0.48 mm), representing 47% of total body length, reaching well beyond distal end of caudal setae ( Figure 7 (a)). Spines basally separated, slender, straight at their base and along shaft, without distal expansions and tapering distally, both spines subequally long. Anal somite unconstricted, with smooth dorsal and ventral surfaces.

Antennule length 0.20 mm, relatively short, not divergent, representing about 19% of total body length and 30% of cephalothorax length. Antennule 4-segmented, all segments completely separate. Distal antennulary segment relatively short, representing 37% of antennule length. In terms of pattern described by Grygier and Ohtsuka (1995) for female monstrilloid antennulary armature, setae (Roman numerals) and spines (Arabic numerals), slender spiniform element 1 present on first segment; elements on second segment: 2d1-2, 2v1-3 and IId; all subequally long, except for relatively longer element 2v 3. Third segment with strong, long element 3 plus elements IIId and IIIv. Segment 4 bearing elements 4aes, 4d1,2, 4v1-3; elements 4v1,2 remarkably long. Setae IVd, Vv, Vd present. Element 5 not observed. Subterminal elements b1-3, 4, 6 present, unbranched; elements 61 – 2 relatively large; aesthetasc 6aes present in specimens ( Figure 7 (d)). Legs 1 – 4 as described by Suárez-Morales and Riccardi (1997) and Suárez-Morales (2002) (as C. tumorifrons ). Fifth legs basally separate, represented by a single subrectangular lobe armed with three subequally long biserially setulated setae on distal position ( Figure 7 (f)).

Male. unknown.

Type locality

Harbour of Trieste , North Adriatic Sea (45°39 ʹ 06.08 ” N, 13°45 ʹ 22.63 ” E) ( Figure 1 ) .

Etymology

The name makes reference to the Mediterranean Sea, the geographic area from which this species has been previously reported under a different name.

Remarks

The new species was originally described as C. tumorifrons by Isaac (1974) from material collected in Emborios Bay, Aegean Sea. He determined that the four males and three females collected belonged to the same species, based on its co-occurrence in the same sample and probably in the relatively common character of a produced forehead in both genders, but overlooking other characters. In the redescription of the males of this species (holotype and three paratypes), Suárez-Morales (1999) argued that the name, published in Isaac ’ s (1974) doctoral dissertation, was, thus, nomenclaturally unavailable and it was explicitly deemed as a nomen nudum there. The subsequent mention of this species and the application of the most recent rules of the ICZN with respect to nomenclatural acts validates Cymbasoma tumorifrons as a name that is attributed to Suárez-Morales (1999) (Grygier and Suárez-Morales in preparation). This name, however, exclusively refers to the male type specimens, thus excluding the females mentioned by Isaac (1974) from the type series, because the conspecificity of these males and the female specimens was unlikely ( Suárez-Morales 1999). Hence, the three adult female specimens designated as (1) allotype and (2) paratypes by Isaac (1974) are not part of the type specimens of C. tumorifrons and, thus, represent an undescribed species. A redescription of these female specimens was published by Suárez-Morales (2002), who at that time attributed these females as C. tumorifrons based on Isaac ’ s type specimens, plus a female found in Toulon Bay. A comparison of the original illustrations by Isaac (1974) and Suárez-Morales ’ (2002) redescription of these female specimens from the Aegean Sea and Toulon Bay allowed us to determine that our specimen from Trieste clearly belongs to the same species. They share the same body shape and proportions, a protuberant forehead, large eyes, a fifth leg with a single segment armed with three long setae, long ovigerous spines reaching well beyond the distal end of caudal setae and also characters of the antennule armature (i.e. the relatively strong apical elements 61,2, the moderately long, strong element 3 and the unbranched b-group setae) ( Isaac 1974; figures A – E; Suárez-Morales 2002, figs. 12 – 21).

Other species of Cymbasoma with uniramous female P5 armed with 3 setae include: C. claparedei Giesbrecht, 1893 , C. striatum Isaac, 1974 , C. boxshalli Suárez-Morales, 1993 , C. quintanarooense Suárez-Morales, 1994 , C. bowmani Suárez-Morales and Gasca, 1998 , C. concepcionae Suárez-Morales and Morales-Ramírez, 2003 , C. guerrerense Suárez-Morales, 2009 and C. cocoense Suárez-Morales and Morales-Ramírez, 2009 . In C. claparedei ( Giesbrecht 1893, fig. 5) and in C. quintanarooense ( Suárez-Morales 1994, fig. 1F; Suárez- Morales and Escamilla 2001, fig. 2E), the fifth leg setae are equally long, thus diverging from the pattern observed in the new species. In addition, in C. boxshalli the innermost fifth leg seta is very short (i.e. as long as bearing segment) ( Suárez-Morales 1993, 2001a), also diverging from the new species. Cymbasoma striatum has a distinctive, conspicuous fringe of cuticular striation around the anterior half of the cephalothorax ( Suárez-Morales 2000b), a character clearly absent in the new species. Cymbasoma bowmani has a distinctive expanded cephalothorax with a protuberant oral papilla ( Suárez-Morales and Gasca 1998, fig. 1A), which differs from the new species; also, the shape of the genital double-somite (weakly expanded in C. bowmani vs anteriorly globose in the new species) and the perioral ornamentation ( Suárez-Morales and Gasca 1998, fig. 2B) are useful to separate them. Cymbasoma guerrerense was first reported as C. tumorifrons by Suárez-Morales and Alvarez-Silva (2001) from the Mexican Pacific, but was later recognised as an undescribed species ( Suárez-Morales and Morales-Ramírez 2009). The new species differs from C. guerrerense in several characteristics (i.e. antennule relative size and features of selected elements, cephalothorax shape and proportions), as already discussed by Suárez-Morales and Morales-Ramírez (2009). In C. concepcionae the genital double somite has an expanded proximal half with straight margins ( Suárez-Morales and Morales-Ramírez 2003, fig. 2B), thus differing from the globose anterior half of the same somite in the new species ( Figure 7 (g)); also, it has a field of ventral and lateral protuberances on the fifth pedigerous somite and a distinctive field of striae running around the ‘ neck ’ area (Suárez-Morales and Morales- Ramírez 2003, figs. A – D), a character absent in the new species ( Figure 7 (a, b)). Cymbasoma cocoense closely resembles the new species from Trieste, but differs in the following respects. The genital double-somite is weakly expanded anteriorly, with softly rounded margins ( Suárez-Morales and Morales-Ramírez 2009, fig. 1C), thus diverging from the clearly globose condition observed in the new species ( Figure 7 (g)). The position of the oral papilla differs in the two species: located at 0.21 of way back along cephalothorax in C. cocoense and 14% in the new species; also, the preoral ornamentation is different in the two species (see Suárez-Morales and Morales-Ramírez 2009, figs. 2A, B). In addition, several elements on the antennulary armature (i.e., 3, 2d1,2, 2v1,3, 61,2) show differences in relative size and compliments ( Suárez-Morales and Morales-Ramírez 2009, fig. 2C) with respect to the pattern observed in the new species ( Figure 7 (d)). The new species is known only from the Mediterranean, in Toulon and the Aegean Sea.

Figures

Figure 1. Location of zooplankton sampling stations in the Gulf of Trieste (Italy), where monstrilloid copepods were obtained during the surveyed period.

Figure 7. Cymbasoma mediterranea sp. nov., holotype adult female. (a) habitus, lateral view; (b) same, dorsal view; (c) cephalic region showing preoral ornamentation, ventral view; (d) frontal area and right antennule with armature, dorsal view; (e) cephalic region showing preoral ornamentation, lateral view; (f) urosome and fifth legs, ventral view; (g) urosome, dorsal view; (h) urosome and fifth legs, lateral view. Scale bars: 200 µm (a, b), 50 µm (c–h).