Gilvossius howellorum, Felder Rafael Robles, 2020

Gilvossius howellorum View in CoL n. sp.

( Figs. 2 View Figure 2 , 3 View Figure 3 , 6D–F View Figure 6 )

Zoobank: urn:lsid:zoobank.org:act:619EC744-BAD2-4F0E-B09A-326CA8444C97

Callianassa atlantica View in CoL .– Williams, 1965: 103 (part? Franklin County, Florida?) ; Williams, 1974: 41 (part? Franklin County, Florida?) ; Williams, 1984: 181 (part? Franklin County, Florida?) .

Gilvossius setimanus View in CoL .– Manning and Felder, 1992: 558 (part, Rickenbacker Causeway, Miami, Florida only); Felder and Robles, 2009: 335, 336, tab. 1, fig. 1; Felder et al., 2009: 1062, 1093 (part,northeastern Gulf of Mexico and Tampa Bay, Florida only); Poore et al., 2019: 94 (part, molecular evidence attributed to Robles et al., 2020).

Type material. Western to southeastern coasts of

Florida (northeastern Gulf of Mexico to Biscayne Bay). Holoty pe: male (DNA and photograph voucher), pocl 12.4 mm, ( USNM 1546234 About USNM = ULLZ 12183 View Materials ), <1 m depth, subtidal sand flat, Pinellas Point, lower Tampa Bay , St. Petersburg , 3 September 2010. — Paratypes : 1 ovigerous female (DNA voucher), pocl 11.5 mm, embryo diameter 1.02–1.17 mm ( USNM 1540396 About USNM = ULLZ 4500 View Materials TB-A), <1 m depth, subtidal sand flat, Pinellas Point, lower Tampa Bay, St. Petersburg , 8 May 2001 ; 1 male (DNA voucher), pocl 8.6 mm ( USNM 1607368 About USNM = ULLZ 4500 View Materials TB-B), data same as preceding; 1 ovigerous female (DNA voucher), pocl 12.5 mm ( USNM 1607369 About USNM = ULLZ 4500 View Materials TB-C), data same as preceding ; 1 male, pocl 7.6 mm, 1 female 11.0 mm, embryo diameter 1.00– 1.10 mm ( USNM 1607370 About USNM = ULLZ 4500 View Materials TB-D), data same as preceding ; 1 male, pocl 10.5 mm, 1 ovigerous female, pocl 12.8 mm ( NMV J-58373), data same as preceding; 1 ovigerous female (DNA voucher, atypical chelipeds), pocl 7.6 mm ( USNM 1543411 About USNM = ULLZ 7919 View Materials ), <1 m, sand bar, mouth of Tampa Bay, St. Petersburg , 17 August 2005 ; 1 male (cheliped photograph voucher), pocl 12.2 mm, ( USNM uncataloged), Anna Maria Island Causeway, Manatee County , Florida, 15 April 1988 ; 1 female, pocl 6.0 mm ( USNM 221848 About USNM ), shallow subtidal flat, west side of Key Biscayne, 28 May 1988 .

Morphological diagnosis. Antennular peduncle third (distal) article 3–4 times length of second (penultimate) article. Adult eyestalks terminated in short, subtriangular, weakly divergent tips. Second maxilliped exopod equal to or exceeding length of endopod merus, endopod with propodus length more than three times propodus width. Third maxilliped operculiform, ischium-merus subrectangular in outline, width of ischium less than greatest length. Adult male major chela fixed finger with primary tooth positioned near or distal to midlength (rare cases slightly proximal), finger margin distal and proximal to tooth broadly depressed or concave, distal slope of tooth usually lacking abrupt marginal offset, tooth not positioned against small marginal notch. Third pereopod propodus inferodistal margin cuspate, marginal setation separated into dense tufts on marginal elevations. Telson rounded over posterior half, posterior margin lacking median spine.

Diagnostic gene sequences. GenBank Accession numbers for paratypes USNM 1540396 About USNM (= ULLZ 4500 View Materials TB-A) , USNM 1607368 About USNM (= ULLZ 4500 View Materials TBB) , USNM 1607369 About USNM (= ULLZ 4500 View Materials TB-C) , and ( USNM 1543411 About USNM = ULLZ 7919 View Materials ): (16S) EU882934, EU882935, EU882936, EU874924; (12S) EU875044, EU8750 45, EU8750 4 6, M N2 38 478; (18S) MN237985 , MN237986 , MN237987 , EU874974; (H3) MN238221 , MN238222 , MN238223 , MN238294 .

Description. Carapace frontal margin with short, broad, triangular rostrum, rostrum f lattened in lateral view, terminally subacute, not reaching to corneas of eyestalks, rostral base flanked laterally by low, bluntly subtriangular shoulders forming orbits ( Figs. 2A, B View Figure 2 ; 6D–F View Figure 6 ); rostral tip not exceeding 1/3 length of eyestalks in dorsal view; dorsal oval weakly defined, becoming obscure near post-rostral midline.

Eyestalks elongate, reaching to penultimate (second) article of antennular peduncle, strap-like, subrectangular in dorsal view, carried slightly def lected, divergent subtriangular tips subacute, slightly upturned distally ( Figs. 2A, B View Figure 2 ; 6D–F View Figure 6 ); medial borders of stalks closely opposed for most of length, meeting along nearly straight line, dorsal surfaces elevated near medial borders, sloping to more narrowly flattened distolateral margins; white corneal pigment well defined in life, corneal surface weakly faceted.

Antennular peduncle longer and distinctly heavier than antennal peduncle, length of distal antennular peduncle article 2 times length of distal antennal peduncle article ( Fig. 2A, B View Figure 2 ); second (penultimate) article shorter than basal, third (distal) article about 4 times length of second; second and third articles with ventromesial and ventrolateral rows of long, distoventrally directed setae. Antennular flagellum dorsal and ventral rami slightly longer than third article of peduncle, ventral with longer setation than dorsal ramus; dorsal ramus heavier than ventral, especially in distal 1/3 where broadest subterminal articles fringed with, dense ventral aesthetascs. Antennal peduncle reaching into distal 1/4 of third antennular peduncle article; basal article dorsolateral carina arched to form lip above excretory pore; length of second article slightly exceeding width, distal articulation to third article with weak scaphocerite; fourth article exceeding combined lengths of first three, distinctly longer than fifth, fourth and fifth ventrally setose; fifth article slightly narrower than others. Antennal flagellum about 3 times longer than rami of antennular flagellum, antennal flagellum setation sparse, setae very thin, 1–4 articles in length.

Mandibular palp 3-segmented, elongate third article heavy, arched, dense elongate setae on second article and proximally on third, dense short stiff brush of setae on distal half of third ( Fig. 2C View Figure 2 ); gnathal lobe of mandible distinctly subquadrate, distolateral shoulder forming rounded obtuse angle, incisor process with about 15 well-defined subtriangular corneous teeth on cutting margin, concave internal face with thickened lip giving rise to weakly dentate molar process positioned proximal and internal to incisor teeth. First maxilla endopodal palp narrow, tip of terminal article deflected ( Fig. 2D View Figure 2 ); proximal endite forming rounded mesial lobe; distal endite elongate, terminally broadened with dense setation. Second maxilla margins setose, endopod narrow, strap-like, terminus wrapping behind adjacent endite ( Fig. 2E View Figure 2 ); first and second endites each longitudinally subdivided, exopod forming large, broadly cupped scaphognathite, distal lobe rounded, proximal lobe subangular.

First maxilliped margins setose, endopod very small, concealed between base of distal endite and exopod ( Fig. 2F View Figure 2 ); distal endite weakly arcuate, narrowing distally to rounded terminus, external surfaces densely setose medially and terminally; exopod elongate, subrectangular, weakly arcuate, incompletely divided by oblique suture, close-set comb of very long plumose setae on mesial margin, those near oblique suture longer than others; epipod shorter than exopod, broadly triangular, anterior and posterior lobes narrowing to rounded angles

Second maxilliped small, margins of both rami setose; endopod merus weakly arcuate, broadest proximally, length exceeding 3 times width, exceeding combined length of subcylindrical propodus and dactylus, length of narrowly elongate propodus about 4 times width, length equal to or exceeding 1/2 length of merus ( Fig. 2G View Figure 2 ); dactylus about twice as long as broad, rounded terminally; exopod narrow, strap-like, carried closely against internal surface of endopod, distinctly longer than endopodal merus, terminally rounded; small rounded epipod present, vestigial branchiae lacking.

Third maxilliped lacking exopod, ischium-merus operculate in form, palp digitiform ( Fig. 2H, I View Figure 2 ); endopod fringed by long setae, especially on mesial margins of ischium and merus, along with most of palp articles; ischium subrectangular, greatest length exceeding width, internal surface with slightly arcuate longitudinal row of minute, terminally cornified, spiniform teeth forming low crista dentata; merus much broader than long, length about 1/2 length of ischium; carpus as broad as propodus, both longer than broad, both with dense field of setae on internal surface, propodus subcylindrical, length near 2 times width; dactylus digitiform, length exceeding 2 times breadth, weakly arcuate, terminally bearing long, stiff bristles.

First pereopods strongly heterochelous in both sexes ( Figs. 3A–C View Figure 3 , 6D–F View Figure 6 ); major cheliped located on either right or left side, shape and ornamentation somewhat sexually dimorphic, typically heavier, stouter, more coarsely ornamented in mature male than in female; ischium slender, superior margin slightly arched or sinuous, inferior marginal carina weakly armed by row of small denticles distally; merus superior margin smooth, slightly depressed in proximal third, sloping smoothly to rounded longitudinal carina subdividing upper and lower halves of external surface, longitudinal carina weakly undercut by longitudinal furrow, terminated proximally where incised by arched furrow above proximal lobe on ventral keel; inferior (flexor) margin forming keel bearing line of subacute denticles, keel proximally bearing broad hooked lobe, terminated in single or multiple denticles, distal and proximal margins of lobe usually armed with additional denticles, most acute on distal margin, larger and usually more rounded on proximal; carpus broad, subquadrate, superior and inferior margins keeled, superior margin bearing few short setae, inferior margin bear few if any setae, terminating distally in acute to subacute angular corner; propodus broad, heavy, median length of postdactylar palm exceeding length of carpus, about 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, opposable edge of fixed finger with primary tooth positioned near or distal to midlength (rare cases slightly proximal), finger margin distal and proximal to tooth broadly depressed, concave, distal slope of tooth usually lacking abrupt marginal offset, tooth not positioned against small marginal notch; dactylus superior margin with array of large punctae bearing tufts of long setae to either side of dorsal crest, extending to near tip, opposable edge with subquadrate to subtriangular tooth proximally, remainder lined by uniform low denticles diminishing in size distally, weak submarginal longitudinal depression to internal side of edge, external side marked by row of large punctae bearing tufts of long setae, tip strongly hooked.

Minor cheliped ischium narrowly elongate ( Figs. 3C View Figure 3 ; 6D, E View Figure 6 ), inferior margin at most weakly serrated by low denticles; merus subrectangular, unarmed; carpus narrow at proximal articulation, elongate with parallel superior and inferior margins in distal half, about twice length of palm ( Figs. 3C View Figure 3 ; 6D, E View Figure 6 ); inferior margins of carpus and propodus bearing slightly longer, denser setae than superior; fixed finger length less than length of palm, fixed finger opposable margin usually with weakly elevated tooth in proximal half, dactylus weakly sinuous, fingers closely opposed, minimal gape, tips acute.

Second pereopod chelate, finger lengths exceeding height of palm; flexor margin of merus and carpus lined by long regularly spaced setae, inferior margin of propodus and superior margin of dactylus similarly setose, setae becoming shorter, stiffer, becoming more hooked distally ( Fig. 3D View Figure 3 ); external surfaces of distal propodus and dactylus with few flattened tufts of setae.

Third pereopod merus length less than 3 times width; propodus with inferodistal margin cuspate, marginal elevations bearing dense tufts of elongate setae ( Fig. 3E, F View Figure 3 ), external surface 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 less than 1/2 length of coxa.

Fourth pereopod very weakly subchelate, inferodistal process of propodus (= fixed finger) developed as a low densely setose rounded lobe extending distally about 1/4 length of dactylus ( Fig. 3G View Figure 3 ); dactylus elongate, weakly sinuous, tapering distally, tip twisted to terminate in ventrolaterally directed triangular tooth.

Fifth pereopod minutely but distinctly chelate terminally amid dense setation, opposable surfaces of fingers slightly spooned, terminally rounded ( Fig. 3H, I View Figure 3 ); propodus with dense field of long, close-set setae on internal surface.

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

Pleonal tergites mostly smooth, glossy dorsally ( Fig. 6D, E View Figure 6 ). First pleonal tergite well sclerotized dorsally, lacking transverse furrow in anterior half, sclerite extended posteroventrally as narrowing lobe, subdivided by conspicuous poorly sclerified furrow. Second tergite about 1½ times length of first, tergite ventral margin weakly bowed, rounded posterolateral lobe with scant setation limited to linear tuft. Third to fifth tergites each with very broad field of very fine soft setae overlying posterolateral lobe, that of third more posteriorly restricted than successively those on fourth and fifth, the fifth originating near midlength. 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. 3M View Figure 3 ). Ventral surfaces of pleonal somites mostly membraneous, lacking extensive armor of sclerotized plates dense tubercles embedded in integument.

Male without first and second pleopods; female first pleopod uniramous, composed of 2 articles, bearing tufts of long setae along length;female second pleopod biramous ( Fig. 3J, K View Figure 3 ), exopod bearing scattered tufts of elongate setae, narrow, bowed, reaching about to end of endopod when flexed against it, endopod with tufts of elongate setae, including at tip of appendix interna. Third to fifth pleopods forming large, posteriorly cupped fans, endopod of each subtriangular with short heavy appendix interna embedded in mesial margin, opposed surfaces on appendix internae of two sides each with small field of microscopic hook setae ( Fig. 3L View Figure 3 ).

Telson wider than long, posterolateral to posterior margin distinctly rounded ( Fig.3M View Figure 3 ), posterior margin without median spine in shallow depression; dorsal surface with weak median elevation in anterior 2/5 bearing bilaterally separated small fields or tufts of setae.

Uropodal endopod broadly ovate, about 1½ times longer than broad, posterior margin with fringe of long setae, lacking marginal development of stiff spines and bristles, dorsal surface lacking stiff spines or bristles, at most with tuft or two of setae posteriorly ( Fig. 3M View Figure 3 ); exopod anterodorsal plate strong, well developed, distally not reaching to endopod margin, setae along posterodistal edge of plate including slightly stronger spiniform bristles posteriorly, grading laterally to thinner, dense, elongate setae of exopod distal margin, continuous dense fringe of fine long setae on exopod distal and posterior margin, posterior margin lacking row of conspicuous stiff bristles.

Etymology. The name of this species honors Joan and George Howell, in recognition of funding provided to support environmental research and education at many levels, including contributions to our studies in marine biodiversity.

Size. Largest male pocl 12.4 mm, largest female pocl 12.8 mm. Smallest ovigerous female pocl 7.6 mm. Range of embryo diameters, measured as greatest dimension, 1.00– 1.17 mm.

Habitat. Known only from deep burrows in intertidal to shallow (<1 m depth) muddy sand f lats along shorelines of high salinity inlets and embayments, all known specimens having been extracted with hand-operated yabby pumps.

Distribution. Tampa Bay to Anna Maria Island on the western coast of Florida; Biscayne Bay on southeastern coast of Florida.

Remarks. Molecular genetic comparisons of Gilvossius howellorum n. sp. to G. setimanus s.s. were for the present limited to 16S mt sequence data. However, the morphologically based separation of these two somewhat similar species is clearly supported at a level of sequence divergence found between other pairings of congeneric callianassid species. For example, species of Lepidophthalmus Holmes, 1904 show sequence divergence from 5.3 to 10.3% ( Robles and Felder, 2015). Our measured 16S sequence divergence between analyzed specimens of Gilvossius howellorum n. sp. and those of G. setimanus s.s. ranged from 18.1 to 19.1%.

Gilvossius howellorum n. sp. and G. setimanus attain maturity at a similar size, and both species appear to be coastally restricted. This, and the posteriorly rounded telson in both, readily separates them from a second new offshore species from the northwestern Gulf of Mexico, to be treated below. While very similar in general habitat and habitus, these species can be separated morphologically by close inspection of the posterior margin of the telson, which bears a very small median spine in G. setimanus and lacks it in G. howellorum n. sp. Very careful microscopic study is sometimes required, as this spine can be minute, concealed among setae, translucent in long-preserved specimens, folded beneath the telson margin, or damaged in varied ways. It is not usually set into a conspicuous median marginal depression. Separation of the two species can also often be based on sculpture and dentition of the adult male major chela fixed finger. In G. howellorum n. sp., the opposable margin is typically armed with a broad-based primary tooth with its apex centered near the finger midlength, distal to it, or slightly proximal to it ( Fig. 6D–F View Figure 6 ); when normally developed, the marginal slopes of this tooth distal and proximal to the apex are broadly depressed or concave, with the distal slope not forming an abrupt marginal offset or positioned against a marginal notch. In G. setimanus , the opposable margin of the adult male major chela fixed finger typically has the primary tooth, when present (often absent in females), positioned at midlength or proximal to it, with the distal slope of this tooth commonly forming an abrupt marginal offset or positioned to butt against a small notch ( Fig.6A–C View Figure 6 ); when the primary tooth is present, the margin proximal to the tooth apex is typically more distinctly serrate (coarsely granulate or denticulate) than is the margin distal to it. In addition, the terminal spines of the ocular peduncles in mature specimens of G. setimanus are often, though not always, more elongate and strongly divergent than are the typically less produced tips of the peduncles in G. howellorum n. sp.

The specimen referred to by Manning and Felder (1992: 558) from the Rickenbacker Causeway, Miami, Florida, now cataloged ( USNM 221848), is now regarded to represent G. howellorum n. sp. As also noted in the preceding treatment of G. setimanus , the distribution of that species reported by Williams (1984) and Abele and Kim (1986) included Franklin County, Florida, in the northeastern Gulf of Mexico. While no archived materials from that site have been located, prompting their listing under questionable status in the synonymy above, coastal habitats there would now be regarded as likely inhabited by G. howellorum n. sp. than by G. setimanus s.s.