Gilvossius fredericqae, Felder Rafael Robles, 2020

Gilvossius fredericqae View in CoL n. sp.

( Figs. 4 View Figure 4 , 5 View Figure 5 , 6G View Figure 6 )

Zoobank: urn:lsid:zoobank.org:act:61F5311E-C506-4E23-B592-B03F3F32C673

Callianassa atlantica .– Rabalais et al., 1981: 96, 99, 101–103 (part, Gulf of Mexico only), 107, 110–112 (part, Gulf of Mexico only), tab. 1, fig. 2a, d, g (only), figs. 5A, B, 6A–E.

Callianassa setimanus View in CoL .– Manning, 1987: 386–388 (part, Gulf of Mexico only).

Gilvossius setimanus View in CoL .– Heard et al., 2007: 21–22 (part, Gulf of Mexico only); Felder et al., 2009: 1062, 1093 (part, northwestern Gulf of Mexico only); Sakai, 2005: 47–48 (part, Gulf of Mexico only); Sakai, 2011: 372–373, 374 (key), 378–379 (part, Gulf of Mexico only).

Callianassa setimana .– Sakai, 1999: 29 (part, Gulf of Mexico only).

Type mate r ial. Of f Te x a s coa st, U.S.A. (northwestern Gulf of Mexico). Holotype: ovigerous female, pocl 4.0mm, embryos 0.65–0.75 mm ( USNM 1607374 = ULLZ 17894), BLM/ STOCS station 6/ II-6, depth 98 m, 27°24’N 96°29’W, 19 November 1976. — Paratypes: 1 male, pocl 2.7 mm ( USNM 1607375 About USNM = ULLZ 17495 View Materials ), BLM/ STOCS station 3/ III-1, depth 106 m, 26°58’N 96°33’ W, 19 February 1976 GoogleMaps ; 1 ovigerous female, pocl 3.6 mm ( USNM 1607376 About USNM = ULLZ 17903 View Materials ), BLM/ STOCS station 3/ II-5, depth 131 m, 27°18’N 96°23’W, 9 December 1976 GoogleMaps ; 2 females (larger one ovigerous), pocl 3.6, 2.4 mm ( USNM 172306 About USNM ), BLM/ STOCS station 3/II, depth 131 m, 27°18’N 96°23’W, 16 May 1975 GoogleMaps ; 1 juvenile male, pocl 2.3 mm ( USNM 1607377 About USNM = ULLZ 17904 View Materials ), BLM/ STOCS station 6/III-5, depth 125 m, 26°58’N 96°30’W, 27 June 1976 GoogleMaps ; 1 mutilated juvenile male, pocl 2.4 mm, ( USNM 1607378 About USNM = ULLZ 17905 View Materials ), BLM/ STOCS station 6/I-2, depth 100 m, 27°39’N 96°12’W, 1 June 1977 GoogleMaps ; 1 juvenile male, pocl 2.2 mm ( USNM 1607379 About USNM = ULLZ 17906 View Materials ), BLM/ STOCS station 6/III-3, depth 125 m, 26°58’N 96°30’W, 26 May 1977 GoogleMaps ; 1 juvenile female, 1 unsexed immature, pocl 2.2, 1.1 mm ( USNM 1607380 About USNM = ULLZ 17496 View Materials ), BLM/ STOCS station 3/II-3, depth 131 m, 27°18’N 96°23’W, 27 March 1976 GoogleMaps ; 1 juvenile male, pocl 2.1 mm ( USNM 1607381 About USNM = ULLZ 17497 View Materials ), BLM/ STOCS station 3/I-2, depth 134 m, 27°34’N 96°07’W, 1 June 1977 GoogleMaps .

Morphological diagnosis. Antennular peduncle third article 3–3.5 times length of second article (both juveniles and mature adults). Adult eyestalks terminated in short, subtriangular, weakly divergent tips. Second maxilliped exopod length less than that of endopod merus, endopod propodus robust, length no more than twice propodus width. Third maxilliped with operculiform ischium-merus subovoid, width of ischium about equal to or greater than length. Male major chela fixed finger opposable margin usually lacking enlarged primary tooth or with any enlarged tooth positioned at or proximal to midlength, opposable margin little if any more coarsely granulate proximally than distally. Third pereopod propodus inferodistal margin not strongly cuspate, regularly arcuate, marginal setation not strongly clustered on elevations along edge. Telson subquadrate, posterior margin truncate, weakly bilobate, small median spine(sometimes minute vestige) on margin centered in shallow depression.

Description. Carapace frontal margin with short, broad, triangular rostrum, rostrum flattened in lateral view, terminally subacute, not reaching to corneas of eyestalks, rostral base flanked laterally by low, bluntly subtriangular shoulders forming orbits ( Fig. 4A, B View Figure 4 ); rostral tip not exceeding 1/2 length of eyestalks in dorsal view; dorsal oval weakly defined ( Fig. 6G View Figure 6 ), obscure near post-rostral midline.

Eyestalks elongate, subtriangular, reaching to penultimate (second) article of antennular peduncle, carried slightly def lected, slightly divergent tips subacute, slightly upturned distally ( Fig. 4A, B View Figure 4 ); medial borders of stalks diverging in distal half, dorsal surfaces elevated near medial borders, sloping to more narrowly flattened distolateral margins; corneal surface weakly faceted.

Antennular peduncle longer and distinctly heavier than antennal peduncle, length of distal antennular peduncle article less than 2 times length of distal antennal peduncle article ( Fig. 4A, B View Figure 4 ); second (penultimate) article shorter than basal, third (distal) article about 2.5 times length of second; second and third (more so) articles with scant distoventrally directed tufts of long setae in broken ventromesial and ventrolateral rows. Antennular flagellum dorsal and ventral rami longer than third (distal) article of peduncle, ventral with some longer setae than dorsal ramus; dorsal ramus heavier than ventral over full length, subterminal articles fringed with, dense ventral aesthetascs. Antennal peduncle reaching to distal 1/4 of third antennular peduncle article; basal article dorsolateral carina arched to form lip above excretory pore; length of second article exceeding width, distal articulation to third article with small triangular scaphocerite; fourth article slightly exceeding combined lengths of first three, distinctly longer than fifth, fourth and fifth with sparse ventral setae; fifth article little if any heavier than fourth. Antennal flagellum unknown.

Mandibular palp 3-segmented, elongate third article heavy, more so than second, arched, dense elongate setae distally on second article and proximally on third, dense short stiff brush of setae on distal half of third ( Fig. 4C View Figure 4 ); gnathal lobe of mandible subquadrate, distolateral shoulder forming broadly rounded obtuse angle, incisor process with about 9 well-defined subtriangular corneous teeth on cutting margin, concave internal face with thickened lip giving rise to weakly molar process bearing several small corneous teeth positioned proximal and internal to incisor teeth. First maxilla endopodal palp narrow, tip of terminal article deflected ( Fig. 4D View Figure 4 ); proximal endite forming obtusely angular mesial lobe; distal endite elongate, broadening distally to densely setose terminal fan. Second maxilla margins setose, endopod narrow, strap-like, terminus wrapping behind adjacent endite ( Fig. 4E View Figure 4 ); first and second endites each longitudinally subdivided, exopod forming large broadly cupped scaphognathite, distal lobe rounded, proximal subangular.

First maxilliped margins setose, endopod very small, concealed between base of distal endite and exopod ( Fig. 4F View Figure 4 ); distal endite weakly arcuate, narrowing distally to rounded terminus, external surfaces densely setose medially and terminally; exopod elongate, broadly strap-like, distinctly arcuate, incompletely divided by suture, close-set patch of setae on mesial margin near oblique suture; epipod as long as exopod, broadly subrectangular, posterior lobe weakly if at all narrowed, anterior lobe narrowing to rounded acute angle.

Second maxilliped small; endopod mesial margin densely lined by long setae, merus mesial margin nearly straight, lateral margin arched, article narrowing distally, length no more than 3 times width, exceeding combined lengths of carpus, propodus, and dactylus; length of short, robust propodus less than 2 times width, length less than 1/2 length of merus ( Fig. 4G View Figure 4 ); dactylus about as long as broad, rounded terminally; exopod narrow, strap-like, carried closely against internal surface of endopod, shorter than endopodal merus, terminally rounded, bearing long distal setae; vestigial branchiae lacking.

Third maxilliped lacking exopod, ischium-merus broadly operculate in form, palp digitiform ( Fig. 4H, I View Figure 4 ); endopod fringed by long setae, especially mesial margins of ischium and merus, along with most of palp articles; ischium subquadrate, greatest length less than or near equal to greatest width, internal surface with longitudinal, weakly sinuous row of terminally cornified spiniform teeth forming distinct crista dentata; merus much broader than long, length greater than 1/2 length of ischium; carpus as broad as propodus, both longer than broad, both with a few tufts of elongate setae on internal surface, propodus robust, subfusiform, length much less than 2 times width; dactylus digitiform, length exceeding 2 times breadth, very weakly arcuate, terminally bearing long, stiff bristles.

First pereopods strongly heterochelous in both sexes ( Figs. 5A–E View Figure 5 , 6G View Figure 6 ); major cheliped located on either right or left side, typically heavier, stouter in mature male than in female; ischium slender, superior margin slightly bowed inward or sinuous, inferior marginal carina weakly armed by row of low denticles, strongest distally; merus superior margin mostly smooth, sometimes roughened by few low tubercles in proximal 1/4, sloping smoothly slightly depressed longitudinal sulcus above ventral keel; inferior (flexor) margin forming keel bearing sharply spiniform lobe in posterior 1/3, lobe slightly excavate on external side, broad terminal spine of lobe distally directed, variably hooked, proximal margin of lobe usually armed with 1–3 additional denticles or spines; carpus broad, subquadrate to subrectangular, superior and inferior margins keeled, superior margin bearing few short setae, inferior margin more densely setose, terminating distally in rounded angular corner; propodus broad, heavy, median length of postdactylar palm slightly less than to slightly exceeding length of carpus, less than two times length of fixed finger, superior and inferior margins keeled proximally, inferior margin with rows of punctae to internal and external sides bearing tufts of long setae, sparsely setose along superior margin, fixed finger opposable margin usually lacking enlarged primary tooth or with any enlarged tooth positioned at or proximal to midlength, opposable margin little if any more coarsely granulate proximally than distally, tip variably hooked; dactylus superior margin with array of punctae bearing tufts of long setae to either side of dorsal crest, extending to near tip, opposable margin lined by minute denticles, opposable margin indented or gaping to varied degree in proximal 1/4, tip variably hooked.

Minor cheliped ischium narrowly elongate ( Fig. 5E View Figure 5 ), inferior margin unarmed or with few very low denticles; merus subrectangular, unarmed; carpus narrow at proximal articulation, elongate with parallel superior and inferior margins in distal half, less than twice length of palm; inferior margins of carpus and propodus bearing longer, denser setae than superior; fixed finger length approximating length of palm, opposable margin at most minutely serrate, otherwise unarmed; dactylus weakly sinuous, fingers closely opposed, minimal gape if any, tips acute.

Second pereopod chelate, fingers short, not exceeding height of palm; flexor margin of merus and carpus lined by long regularly spaced setae, inferior margin of propodus lined by long regularly spaced setae becoming stiffer and more hooked distally, similar to tufts along extensor margin of dactylus ( Fig. 5F View Figure 5 ); external surfaces of distal propodus and dactylus bearing few flattened tufts of setae.

Third pereopod merus length less than 3 times width; propodus inferodistal margin not distinctly strongly cuspate, lobe regularly arcuate with marginal setation not strongly clustered on elevations ( Fig.5G View Figure 5 ), external surface partially covered by tufts of short setae; dactylus tear-shaped, concealed by long dense setae on external surface, article terminating in elongate, narrow, laterally directed corneous spine. Diameter of female gonopore 1/2 length of coxa.

Fourth pereopod not obviously subchelate, inferodistal corner of propodus concealed by dense setation, not produced ( Fig. 5H, I View Figure 5 ); dactylus elongate, tapering distally to narrow corneous tip forming distolaterally directed talon concealed by dense setation.

Fifth pereopod minutely chelate to subchelate terminally amid dense setation, fixed finger short, subtriangular, no longer than breadth at base ( Fig.5J View Figure 5 ); propodus with distal fields of, close-set setae on internal and external surfaces.

Branchiae limited to pair of arthrobranchs on third maxilliped and each of first through fourth pereopods.

Pleonal tergites mostly smooth dorsally ( Fig. 6G View Figure 6 ). First pleonal tergite lightly sclerotized dorsally, broad transverse depression or furrow in anterior half, extended posteroventrally, sclerite extended posteroventrally as undivided lobe. Second tergite about 1½ times length of first, tergite ventral margin weakly bowed, lined by long setae, rounded posterolateral lobe with long setae in patch on lower half.Third to fifth tergites each with linear patch of long supramarginal setae on lower part of posterolateral lobe, broader patch of long setae centered higher above margin in posterior half of third tergite, at midlength of fourth tergite, in anterior half of fifth tergite.Sixth tergite with distinct posterolateral groove and short suture defining posterolateral lobe, suture not extending across tergite, lobe with submarginal tuft of stiff setae posterolaterally, posterior margin of tergite with similar tuft to mesial side of lobe ( Fig. 5O View Figure 5 ). Ventral surfaces of pleonal somites mostly membraneous, lacking extensive armor of sclerotized plates or dense tubercles embedded in integument.

Female with first and second pleopods; first uniramous, composed of 3 articles, bearing tufts of elongate setae; second biramous ( Fig. 5K, L View Figure 5 ), exopod with scattered tufts of elongate setae, narrow, bowed, shorter than endopod when flexed against it, endopod with tufts of elongate setae, including at tip of appendix interna. Male with small uniramous first pleopod composed of 2 articles, lacking second male pleopod ( Fig. 5M View Figure 5 ). Third to fifth pleopods forming large, posteriorly cupped fans, endopod of each subtriangular with short heavy appendix interna embedded in but extending short distance beyond mesial margin, opposed surfaces on appendix internae of two sides each with small field of microscopic hook setae ( Fig. 5N View Figure 5 ).

Telson wider than long, subquadrate, posterior margin truncate, weakly bilobate, bearing small median marginal spine (sometimes minute vestige) centered in shallow depression ( Fig. 5O View Figure 5 ); dorsal surface with weak median elevation in anterior 1/4 bearing bilaterally separated fields or tufts of setae.

Uropodal endopod broadly ovate, about 1½ times longer than broad, posterior margin with continuous fringe of long setae, lacking posterolateral development of stiff spines and bristles, dorsal surface at most with few short spiniform setae ( Fig. 5O View Figure 5 ); exopod anterodorsal plate small, distinct distally, weakly evident proximally, not reaching to endopod margin, setae along posterodistal edge of plate including spiniform bristles posteriorly, grading laterally to thinner, dense, elongate setae of exopod distal margin, continuous dense fringe of long setae on exopod distal margin replaced posteriorly by marginal row of heavy stiff spines or bristles, posterior margin of exopod very weakly sinuous.

Color. Unknown in life, as all present specimens are preserved and are largely translucent except for opaque whitish at thickened areas of integument, especially at tips of cheliped fingers.

Size. Largest male pocl 2.7 mm, largest female pocl 4.0 mm. Smallest ovigerous female pocl 3.6 mm. Range of embryo diameters, measured as greatest dimension, 0.65–0.75 mm.

Habitat. The depth range of 98–104 m for this species far exceeds depths reported for confirmed specimens of G. setimanus , the species with which it was long confused under the junior synonym C. atlantica . This range represents the deepest stations for box core collections of burrowing infauna along transects of the 1976–1977 BLM/ STOCS survey off the Texas coast, the only sites in that extensive survey where G. fredericqae n. sp. was found to occur. In addition to collection depths, salinity and sedimentary profiles were reported for this species by Rabalais et al. (1981: fig.6). These show its restriction to high salinity offshore waters in muddy substrates that include little sand, in contrast to the nearshore settings and sandier substrates occupied by its presently known western Atlantic congeners.

Distribution. Known only from offshore continental shelf waters of Texas in the northwestern Gulf of Mexico.

Etymology. This species is named for Suzanne Fredericq, a distinguished seaweed specialist based at the University of Louisiana – Lafayette, cherished friend, and respected colleague with whom we have very productively and enjoyably collaborated during multiple research cruises over several decades. Her broad general knowledge of marine biota and contagious enthusiasm have inspired us no less than the many students and postdoctoral associates that she has trained.

Remarks. Several morphological features of this species lead us to make its assignment to Gilvossius provisional, pending our securing of gene-sequence quality specimens for analyses to confirm its generic affiliations. In particular, the posteriorly truncate telson differs from those of most other species of Gilvossius , as redefined by Poore et al. (2019). Also, at least one of the immature males has a small first pleopod ( Fig. 5M View Figure 5 ), though no second pleopod is evident so far as known from limited available material.

No example exists of a fully mature male cheliped among presently available specimens of this species, many of which are fragmentary or immature.Intending to more fully represent characters of C. atlantica in the course of reporting the species from the Gulf of Mexico, Rabalais et al. (1981: fig. 2B, C, E, F, H) illustrated the third maxilliped, cheliped, carapace front with eyes and peduncles, minor cheliped, and tail fan from a female museum specimen that had been collected off North Carolina ( USNM 51007), having concluded at the time that both populations represented a single species. These selected figures, including the cheliped with a distinct tooth on its opposable margin, are now identifiable as G. setimanus s.s. However, with Chorazole Black E staining, one of the unsexed immature specimens that those authors listed from the Gulf of Mexico can now be definitively identified as a male, and its cheliped is intact ( Fig. 5D View Figure 5 ). While the propodus and carpus of this male cheliped are proportionally broader than in the illustrated mature females ( Fig. 5A–C View Figure 5 ), dentition on the cutting edges of the fingers is similar in both sexes, with neither having an enlarged primary tooth on the fixed finger as typically found in G. setimanus and G. howellorum n. sp. Even so, a mature male is required to confirm that this persists in the adult of that sex, just as it appears to do in females.

We have not definitively assigned a small (pocl 3.5 mm) mature female cataloged as G. setimanus ( USNM 256541), taken by the Johnson Sea Link submersible at 274 m depth in the Bahamas. While from much deeper water than the northwestern Gulf of Mexico materials,this specimen resembles G.fredericqae n. sp. in being sexually mature at the same size and in having a median spine on a somewhat truncate posterior margin. It also shares a third pereopod propodus that does not have setation distinctly clustered along a cuspate ventral margin and closely resembles G. fredericqae n. sp. in general characteristics of the anterior carapace, eyestalks, peduncles, and most features of the major cheliped.However, the dactylus of the major chela differs in having a deep narrow incision proximally, the minor chela fingers gape more conspicuously, and the minor cheliped propodus and carpus are relatively broader than in available specimens of G. fredericqae n. sp. While this specimen clearly does not represent G. setimanus s.s., we also are reluctant to assign it to G. fredericqae n. sp. and defer more definitive treatment in hopes that additional materials from this depth and location become available.