Munidopsis exuta Macpherson & Segonzac, 2005

Gaytán-Caballero, Adriana, Escobar-Briones, Elva, Robles, Rafael & Macpherson, Enrique, 2022, Munidopsis geyeri and M. exuta (Crustacea: Munidopsidae): A study of two deepsea, amphi-Atlantic species that co-occur in the southern Gulf of Mexico, Zootaxa 5213 (4), pp. 301-335 : 320-321

Munidopsis exuta Macpherson & Segonzac, 2005

( Figs 3 ; 4 ; 5A )

Munidopsis subsquamosa .— de Saint Laurent, 1985: 475 (not M. subsquamosa Henderson, 1885 ),

Munidopsis crassa .— Segonzac, 1992: 596 (not M. crassa Smith, 1885 ).

Munidopsis geyeri .— Macpherson & Segonzac, 2005: 26 (not M. geyeri , Florida Escarpment organisms: 1 male, 17.6 mm, 1 female, 10.2 mm) .

Munidopsis exuta Macpherson & Segonzac, 2005: 22–25 , tab. 2, fig. 5 (description, distribution and ecology).— Macpherson & Segonzac, 2006: 442, figs 1, 2, 3 (description); Jones & Macpherson 2007: 479, tab. 1, fig. 12 (phylogenetic analysis); Baba et al., 2008: 141 (list of taxa); Martin, 2011: 184 (distribution list); Coykendall et al., 2017: tab. 4, fig. 4 (phylogenetic analysis); Dong et al., 2019: 3, tab. 1, fig. 6 (phylogenetic analysis).

Type material examined. Holotype: ovigerous female, 34.7 mm ( MNHN Ga 4621 = MNHN IU 2014 19814), Mid-Atlantic Ridge, vent site Snake Pit-Les Ruches, HYDROSNAKE, Stn HS 08, 23 22.15′ N, 45 57.1′ W, 3502 m, 26.06.1988 . Paratype: 1 female, 32.0 mm ( MNHN IU 2014 19818), Mid-Atlantic Ridge, vent site Snake Pit-Elan, MAR93 , Alvin Dive 2617, Stn PLM09, 23 22.1′ N, 44 56.9′ W, 3500 m, 18.06.1993 .

Additional material examined. Soft abyssal substrate ecosystems: Bay of Biscay , BIOGAS 5, Stn CV40 , 47 33′ N, 09 02′ W, 2860 m, 15.06.1974: 1juv. female, 18.2 mm, 1ovig. female, 29.2 mm ( CEAB CRU 2004-01 , Fig. 3F, 3G ). BIOGAS 6, Stn CP10, 47 30′ N, 09 04′ W, 2878 m, 21.10.1974: 1 juv. male, 17.1 mm ( CEAB CRU 2004- 02 ) . Hydrothermal vent ecosystems: Mid-Atlantic Ridge, vent site, Akademik 50, Stn 4787, 30 07′ N, 42 07′ W, 3020 m: 1 ovig. female, 20.5 mm ( CEAB CRU 2004-03 , Fig. 3C ) . Mid-Atlantic Ridge, vent site TAG, AMK 47 , Stn 4343, 26 08′ N, 44 49′ W, 3650 m, 26.06.2002: 1ovig. female, 39.5 mm, 1 female, 31.6 mm ( CEAB CRU 2004- 04 ) . Cold seep ecosystems: Florida Escarpment, ALVIN 3637 , 4–5 , 26 01.8′ N, 84 54.9′ W, 3288 m, 30.10.2000: 1 juv. female, 10.2 mm, 1 male, 17.6 mm ( CEAB CRU 2004-05 , Fig. 3D, E ) . Southern Gulf of Mexico , Chapopote Knoll, Dive 81 Stn GeoB10617-5, 21 53.94′ N, 93 26.226′ W, 2919.2 m, 11.04.2006: 1 juv. male, 13.3 mm ( CNCR 24866 ) . Dive 82 Stn GeoB10619-19, 21 53.922′ N, 93 26.166′ W, 2875 m, 12.04.2006: 1 ovig. female, 41.2 mm ( CNCR 24846 = ULLZ 8792 , Fig. 3B ), 1 male, 25.72 mm ( CNCR 24857 = ULLZ 8861 , Fig. 3A ) . Dive 84, Stn 10625-13, 21 53.994′ N, 93 26.124′ W, 2916 m, 15.04.2006: 2 females, 28.5 mm ( CNCR 24867 ) , 32.6 mm ( CNCR 24869 ) , 1 male, 28.6 mm ( CNCR 24868 ) . Gulf of Guinea, Regab Pockmark site, BIOZAIRE 3, Stn CP20, 05 46.89′ S, 09 44.66′ E, 3113 m, 02.01.2004: 1 juv. female, 8.3 mm ( CEAB CRU 2004-06 ) .

Remarks. The specimens of Munidopsis exuta collected at Chapopote Knoll (n = 6) match the original description of the species; nevertheless, some variations are observed. The rostrum is horizontal or slightly upcurved (upcurved in the holotype from 3502 m depth). The antennal spine is present (left and right sides) in one specimen (CNCR 24867) and only the right antennal spine in another specimen (CNCR 24857 = ULLZ 8861, Fig. 3A ), being always smaller than the first lateral spine of the carapace (absent in the holotype and specimens from Bay of Biscay and Mid-Atlantic Ridge). Apart of the two well-developed conical epigastric spines (in adults), some specimens (50%) present spine-like tubercles on the gastric region (CNCR 24857 = ULLZ 8861, Fig. 3A ; CNCR 24846 = ULLZ 8792, Fig. 3B , CNCR 24868). The specimens from the Florida Escarpment (in the northeastern Gulf of Mexico) and the Regab Pockmark site (Gulf of Guinea) match the diagnostic identification of M. exuta with regards the shape of the rostrum, the absence of antennal spines, and the shape of the dactylus on the walking legs. These diagnostic characters are detected on juvenile organisms of all localities. Figure 4 shows a comparison between juvenile specimens of M. exuta and M. geyeri .

Ecology. Munidopsis exuta has been recorded on soft abyssal substrates and in the immediate vicinity of active hydrothermal vent structures ( Macpherson & Segonzac 2005). The specimens of M. exuta analyzed in this study were collected at three cold seep sites, two in the Gulf of Mexico (Chapopote Knoll, in the southern Gulf of Mexico and in the Florida Escarpment in the northeastern Gulf of Mexico), and one specimen from a cold seep site in the Regab Pockmark in the Gulf of Guinea. Those specimens from Chapopote Knoll were collected from the main asphalt field (continuous asphalt flow habitat), asphalt fragments (breccia with chemosynthetic influence habitat) and gas seepage habitats.

At the Mid-Atlantic Ridge hydrothermal vents M. exuta was collected at the base of an active edifice in a baited trap, together with a nephropid lobster Thymopides laurentae Segonzac & Macpherson, 2003 , and a macrurid fish Coryphaenoides armatus (Hector, 1875) , but also at the base of an inactive site among empty shells of mytilid bivalves ( Macpherson & Segonzac 2006). Munidopsis exuta was also collected along with M. geyeri on two cold seep ecosystems: Regab Pockmark and Chapopote Knoll (at breccia influenced by chemosynthesis). Morphological similarities among specimens through video identification were limited by the lack of close-up video by the ROV in Chapopote Knoll. The wide-angle images recorded a random distribution pattern among Chapopote Knoll’s seafloor habitats.

Geographical distribution. Our records extend the known distribution of M. exuta from Bay of Biscay and the Mid-Atlantic Ridge to the Gulf of Mexico and the Gulf of Guinea from 2860 to 4237 m depth ( Fig. 5A ). Within the Gulf of Mexico ( Felder et al. 2009b) the distribution extends from the north-northeastern (NNE; Florida Escarpment) to the south-southwestern (SSW; Chapopote Knoll) cold seep sites. The species displays an amphi-Atlantic distribution and matches the pattern described by Schnabel et al. (2011) and Navas et al. (2013).

Figures

FIGURE 3. Munidopsis exuta Macpherson & Segonzac, 2005. A, male, from Chapopote Knoll (CNCR 24857 = ULLZ 8861); B, ovigerous female, Chapopote Knoll (CNCR 24846 = ULLZ 8792); C, ovigerous female, Mid-Atlantic Ridge (CEAB CRU 2004-03); D, juvenile female and E, juvenile male, Florida Escarpment (CEAB CRU 2004-05); F, juvenile female, and G, ovigerous female, Bay of Biscay (CEAB CRU 2004-01). Scale bar = 10 mm in A, B, C, G; 5 mm in D, E, F.

FIGURE 4. Morphological comparison between Munidopsis exuta and Munidopsis geyeri juveniles. CL = carapace length.

FIGURE 5. Geographic distribution of A, Munidopsis exuta and B, M. geyeri. Numbers with circles represent specimens analyzed in this study, letters with triangles represent populations not examined on this study. See Table 1. Base map from UNINMAR (2020).