Monstrilla ghirardellii, 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 : 1818-1822

Monstrilla ghirardellii sp. nov.

( Figures 8 (a – f) and 9(a – c))

Material examined

Holotype: adult male from station LTER-C1 station, Gulf of Trieste , North Aegean Sea (45° 42 ʹ 2.99 ” N, 13°42 ʹ 36.00 ” E; Figure 1 ), specimen partially dissected, mounted on slides in glycerine, sealed with Entellan ®. Date of collection: 9 January 2014. Slides deposited in ECO-CHZ-009526.

Description of adult male

Total body length: 1.32 mm. Cephalothorax 0.71 mm long, representing 54% of total body length ( Figure 8 (a, b)). Midventral oral papilla well developed, located at 27% of cephalothorax length ( Figure 8 (b)). Cephalic region not protuberant bilaterally in dorsal view, as wide as cephalothorax. Pair of dorsal ocelli present; pigment cups medium-sized. Ocelli medially conjoined by strong pigmentation; ventral ocellus about same size and diameter as eyes. No sensilla observed between antennulary bases. Forehead area moderately produced, with rounded protuberance with marginal row of minute bud-like structures ( Figure 8 (c)). Other cuticular processes weak, represented by two nipple-like processes with adjacent faint striae on perioral area ( Figure 8 (c)).

Urosome consisting of fifth pedigerous, genital somite (carrying genital complex), two free somites, and anal somite ( Figure 8 (b, e, f)). Fifth pedigerous somite with moderately corrugated ventral surface, dorsal surface smooth. Genital somite slightly shorter than fifth pedigerous somite; genital complex of type I ( Suárez-Morales and McKinnon 2014), represented by an elongated or short cylindrical shaft with a short distal bifurcate rounded expansion with reduced lappets ( Figure 8 (b)). In ventral view lappets short, rounded, lacking processes or ornamentations at common basal joint ( Figure 8 (e)). Incomplete intersegmental suture between second free (preanal) and anal somites (arrows in Figure 8 (f)), suture visible only on ventral and dorsal surfaces. Anal somite about as long as preanal somite. Caudal rami subrectangular, approximately 1.4-times as long as wide, about as long as anal somite. Each ramus with five subequally long caudal setae ( Figure 8 (e)).

Antennulary length 0.53 mm. Antennules relatively long, representing 42% of total body length and 79% of cephalothorax length; 5-segmented, segments 1 – 2 separated by suture, segments 2 – 4 fused, intersegmental divisions marked by constrictions (arrows in Figure 8 (d)); segment 5 located distal to geniculation ( Figure 8 (d)). Element 1 on first segment slender, setiform, long, reaching halfway along second segment. Antennulary elements 2v1-3, 2d1,2 and IId present on second segment, with elements 2d1,2 being longest of 2v-d group. Setal elements IIId, IIIv and 3 present on third segment; element 3 slender, long. Fourth segment with elements 4d1-2, 4v1 – 3, IVd and IVv; all elements on this group small, spiniform. Fifth segment with 5 ‘ b ’ -group setae (setae A – D in Figure 8 (d)), elements b1-3 unbranched. As for Huys ’ et al. (2007) setal nomenclature of the distal segment, elements A – D and 1 – 3 present.

Incorporated first pedigerous somite and succeeding three pedigerous somites, each bearing well-developed biramous legs. Pedigerous somites 2 – 4, together accounting for 33% of total body length in dorsal view ( Figure 8 (b)). Coxae of each pair unarmed, joined by intercoxal sclerite, which is slightly longer than wide and ornamented with fields of spinules ( Figure 9 (a – c)). Bases of legs 1 – 4 separated from coxae posteriorly by oblique articulation; with basipodal outer seta; on leg 3 ( Figure 9 (c)), this seta about 7-times longer, sparsely setulated and slightly thicker than those on the other legs. Endopods and exopods of legs 1 – 4 triarticulated. Exopods of legs 1 – 4 longer than endopods. Inner seta on first exopodal segment of legs 1 – 4 absent. Outer spine on distal exopodal segment of legs 1 – 4 acute, about 0.3-times as long as segment. Also, outermost apical exopodal setae of legs 1 – 4 with inner margin smooth, outer margin sparsely spinulose. Armature formula of legs as in male of Cymbasoma pseudobidentatum .

Female. unknown.

Type locality

LTER-C1 station (45°42 ʹ 2.99 ” N, 13°42 ʹ 36.00 ” E), Gulf of Trieste , North Adriatic Sea ( Figure 1 ) .

Etymology

The species is warmly dedicated to Professor Elvezio Ghirardelli, an esteemed Italian marine biologist who strongly contributed to the revival of the plankton research in the

Gulf of Trieste after the Second World War and was the first director of the Laboratory of Marine Biology of Trieste.

Remarks

Type I male genital complex ( Suárez-Morales and McKinnon 2014) is known only in a few species of Monstrilla , i.e. M. reidae Suárez-Morales, 1993 , M. pygmaea Suárez-Morales, 2000c , M. bahiana Suárez-Morales and Dias, 2001 , M. globosa Suárez-Morales, 2003 and M. patagonica Suárez-Morales et al., 2008 and in one species of Monstrillopsis ( M. fosshageni Suárez-Morales and Dias, 2001 ). The specimen from Trieste shows some differences with respect to these other species of Monstrilla . It differs from M. bahiana in the number of caudal setae: 5 in the new species, 6 in M. bahiana ( Suárez-Morales and Dias 2001, figure 18), in the perioral ornamentation, a ventral protuberance is absent and elements like two pair of papilla-like processes are present in M. bahiana ( Suárez-Morales and Dias 2001, fig. 17), thus diverging from the condition observed in the new species. In addition, the genital complex is clearly more elongated than in the new species ( Suárez-Morales and Dias 2001, fig. 18) and the antennules have branched setae on the distal segment vs simple setae in the new species. In M. reidae the shaft of the genital complex is also clearly longer and narrower than that in the new species, the antennule segmentation is complete (i.e. no fused segments) ( Suárez-Morales 1993, figs. 1b, j), and it has 6 caudal setae (vs 5 in the new species). In M. pygmaea and M. patagonica the body proportions are different; both species have a more robust, short cephalothorax ( Suárez-Morales 2000c, figs. 1A, B; Suárez-Morales et al. 2008, figs. 1A, B) than that of the new species from Trieste. In addition, the last antennulary segment in these two species has distinctive rows of spinules on subdistal position, a character absent in the new species. Also, the terminal lappets are subquadrate in M. pygmaea , thus diverging from the rounded condition of these structures in the new species ( Figure 8 (f)). Monstrilla patagonica has 6 caudal setae ( Suárez-Morales et al. 2008, fig. 2D) vs 5 in the new species. Monstrilla globosa can be easily distinguished from the new species by the presence of a reduced fifth leg lobe (Suárez- Morales 2003), a character absent in the new species.

Figures

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

Figure 8. Monstrilla ghirardellii sp. nov., holotype adult male from Trieste. (a) habitus, ventral view; (b) same, lateral view; (c) cephalic region, ventral view; (d) right antennule with armature, dorsal view; (e) urosome and genital complex, ventral view; (f) same, lateral view. Scale bars: 200 µm (a, b), 50 µm (c), 100 µm (d–f).

Figure 9. Monstrilla ghirardellii sp. nov., holotype adult male from Trieste. (a) leg 1 with intercoxal sclerite; (b) leg 2 with intercoxal sclerite; (c) leg 3. Monstrilla grandis Giesbrecht, 1891, adult male, specimen A, from Trieste. (d) urosome and fifth legs, ventral view; (e) cephalic region, ventral view showing anteriormost row of bud-like processes (arrowed); (f) same, lateral view (protuberance arrowed). Scale bars: 100 µm.