Nemopsis mianzani, Oliveira, Otto M. P., Feliú, Guillermo & Palma, Sergio, 2015

Oliveira, Otto M. P., Feliú, Guillermo & Palma, Sergio, 2015, Nemopsis mianzani n. sp. (Hydrozoa, Bougainvilliidae), a new hydromedusa from central Chile, Zootaxa 3990 (2), pp. 296-300 : 297-298

Nemopsis mianzani n. sp.

( Figure 1–2 ; Table 1)

Material examined. Holotype: Male medusa with 9.5 mm in length. 11.xi.2013. Off Dichato, Chile (36°30’S, 73°05’W) (MNHNCL/CNID-15001); Paratypes: Two female medusa with 9.3 and 8.9 mm in length. 11.xi.2013. Off Dichato, Chile (36°30’S, 73°05’W) (ZOOTIMO201404).

Length of umbrella, from top to edge 9.48 mm

Diameter or umbrella at the top of the gastric cavity 7.53 mm

Diameter or umbrella at the edge 7.48 mm

Length of subumbrella 5.69 mm

Diameter or subumbrella at the edge 6.62 mm

Width of velum 480–546 μm Diameter of gastric cavity 3.24 mm

Length of gastric cavity, from top to the edge of manubrium 2.59 mm

Diameter of manubrium 1.08 mm

Length of oral tentacles up to 1.49 mm Diameter of oral tentacles at the base 171–183 μm Number of oral tentacle ramifications up to 7

Diameter of nematocyst aggregations at the oral tentacles extremities up to 47 μm Distance between radial canals 2.61 mm

Diameter of radial canal 193–208 μm Tentacular bulb length up to 3.06 mm Number of filiform tentacles per bulb 26–30

Diameter of filiform tentacles tentacles at the base 80–95 μm Diameter of club-shaped tentacles at the base 109 μm

Length of the club-shaped tentacles up to 1.36 mm Diameter of the club-shaped tentacle ocellum 30 μm

Diameter of the filiform tentacle ocellum 72–79 μm Description. Medusa. Umbrella bell-shaped, transparent, about 1.5 times higher than wide, with top and sides curved. Thick apical jelly, about 2/5 of bell-height. Four interradial subumbrellar pockets projecting into apical jelly. Four radial canals connected to a thin ring canal near broad marginal bulbs. Bulbs curved with 23-29 filiform tentacles. In some bulbs, a pair of short club-shaped tentacles is present in the median portion, inserted above the filiform tentacles. Ocelli at the base of each filiform tentacle, and on a swelling near the base in club-shaped tentacles. Manubrium conical, ending in a mouth with four short lips. Base of manubrium with perradial lobes restricted to the proximal 1/3 of the radial canals. Four perradial oral tentacles arising well above mouth margin, branching 6-8 times; extremities swollen with concentration of nematocysts. Gonads are translucent with a thick layer on the manubrium and its basal outgrowths. Female gonads yellow, male gonads milk white in color. Microbasic euryteles and desmoneme nematocysts present along the oral and marginal tentacles.

Polyp not known.

Paratypes variation. No important variation was observed in the paratypes, except for the slight variation in the length of umbrella (8.9 to 9.3 mm).

Etymology. The specific name was given in honor of Dr. Hermes Mianzan, deceased in 2014, for his important and enthusiastic contributions for the knowledge of gelatinous zooplankton biology and diversity in South America.

Remarks. Nemopsis mianzani differs from the other Nemopsis species for presenting four interradial sub-umbrellar projections, a thicker mesoglea in the apical portion of the umbrella, and short basal perradial lobes of the manubrium. Table 2 presents a comparison between the four valid species of Nemopsis . In the other species, the umbrella is more semi-spherical in form (viz. N. dofleini in Maas 1909; N. hexacanalis in Huang & Xu 1994; N. bachei in Schuchert 2007). Although Uchida (1925) illustrated a thick jelly for N. dofleini from Japan and Kramp (1959, p.111) a N. bachei with the same characteristic from the Atlantic, none of them presents the interradial sub-umbrellar projections and both present gonads more longer distributed along the radial canals than observed in N. mianzani . Despite of the known that N. bachei is a potential invasive species and that populations of newly invaded regions might show a strong founder effect, no previous records on the morphological variation of that species could suggest a similarity with N. mianzani 's morphology.

Figures

FIGURE 1. Living holotype of Nemopsis mianzani n. sp. (MNHNCL / CNID- 15001). A, lateral view of the medusa; B, closer view of the oral tentacles; C, closer view of the tentacular bulb. Legend: cst, club-shaped tentacles; ft, filiform tentacle; go, gonad; isp, interradial sub-umbrellar projection; mo, mouth; ot, oral tentacle; otr, oral tentacle ramification; rc, radial canal; tb, tentacular bulb.

Tables

TABLE 2. Comparison between the fourspecies of Nemopsis, based on the original descriptions and re-descriptions by Uchida (1925), Kramp (1959; 1968) and Schuchert (2007).

Characteristic \ Species	N. bachei N. dofleini N. hexacanalis	N. mianzani
Number of radial canals	4 4 6	4
Length of basal lobes of manubrium	from 1/2 to 3/4 from 1/2 to 3/4 about 3/4	up to 1/4
Number of branching of oral tentacles	up to 8 5–7 3–4	6–8
Number of filiform tentacles on each bulb	14–36 about 40 8	26–30
Umbrella length	up to 12 mm about 13 mm about 6 mm	up to 10 mm
Interradial sub-umbrellar projections	absent absent absent	present