Mexctenapseudes boeschi, Drumm & Heard, 2022

Drumm, David T. & Heard, Richard W., 2022, Mexctenapseudes boeschi, a new tanaidacean genus and species (Crustacea: Peracarida: Apseudomorpha: Parapseudidae) from the Mexican coast of Campeche with the designation of a new related Australian genus to receive Longiflagrum caeruleus (Boesch, 1973), Zootaxa 5116 (2), pp. 200-222 : 206-216

publication ID	https://doi.org/ 10.11646/zootaxa.5116.2.2
publication LSID	lsid:zoobank.org:pub:F66FE8C9-B813-41CF-ABB1-B9646EC1CB05
DOI	https://doi.org/10.5281/zenodo.6369020
persistent identifier	https://treatment.plazi.org/id/03939E49-FFE2-FFD4-FF7A-FF6A92CCFB19
treatment provided by	Plazi
scientific name	Mexctenapseudes boeschi
status	sp. nov.

Treatment

Mexctenapseudes boeschi View in CoL n. sp.

( Figs 2–10 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 View FIGURE 10 )

Material examined. Holotype: female (♀), 7.0 mm, ( CNCR 35897 ). Campeche Coast , Mexico; Station 11 (18°51’0’’N, 91°57’35.9994’’W), depth 16.1 m GoogleMaps . – Allotype (Paratype): male (♂), 7.5 mm, ( CNCR 35898 ). Additional paratypes: 11 ♂♂ (7.5 mm max.); 11 ♀♀ (7.5 mm max.) (7.5 mm max.) ( CNCR 35899 ), same collection data as holotype. 71 ♂♂ (7 mm max.); 80 ♀♀ (7.5 mm max.) ( USNM 1550586 About USNM ), same collection data as holotype. -- 5 ♂♂ (7mm max.); 5 ♀♀ (7.5 mm max.) ( GCRL 6614 View Materials ), same collection data as holotype GoogleMaps . Additional specimens from all locations near the type locality retained in the collection of the senior author at EcoAnalysts, Inc., and the Museum of the USM Gulf Coast Research Laboratory.

Etymology. Named in honor of Dr. Donald Boesch, whose excellent 1973 descriptions of Apseudes estuarius and A. caeruleus led, respectively, to the establishment of the genera Longiflagrum Gutu, 1995 and Pseudolongiflagrum .

Description. Based on adult female holotype ( Figs 2 View FIGURE 2 , 3 A, C, D View FIGURE 3 ) and adult male and female Paratypes ( Figs 3B, E View FIGURE 3 , 4A View FIGURE 4 – 7D View FIGURE 7 ). Body ( Figs 2 View FIGURE 2 , 3A View FIGURE 3 ) about 5 times longer than greatest width. Cephalothorax as long as wide, longer than first two pereonites combined, lateral margins naked; rostrum ( Fig. 3B View FIGURE 3 ) subtriangular, gently tapering to finely spinulate subacute tip (tip is ventrally curved, often broken off). Eye lobe distinct; eyes with visual elements with brownish-red pigment. Epistomal spine ( Fig. 3C View FIGURE 3 ) well-developed, directed antero-dorsally. Pereon about 60% of body length; pereonite-2 shortest, pereonites 4 and 5 longest and subequal; hyposphenia weakly developed, at least one small hyposphenium on pereonites 2–6 (absent on pereonite 1). Pleon ( Fig. 3A, D View FIGURE 3 ) short, slightly longer than pereonite-6, about 11% of body length; pleonite 1 with continuous dorsal row of short plumose setae; pleonites 2–5 with posterolateral apophyses increasing in length posteriorly; all pleonites with one small dorsolateral simple seta and several lateral plumose setae; hyposphenia present, decreasing in length posteriorly. Pleotelson ( Fig. 3A View FIGURE 3 ) sub-rectangular, slightly longer than greatest width (at juncture with pleon), gently tapering posteriorly to insertion of uropods, with one seta on each side and pair of small dorsoposterior setae; posterior margin rounded, lobate, not extending past uropodal peduncle.

Antennule ( Fig. 3E View FIGURE 3 ) peduncle article-1 about 3.5 times longer than wide with several simple setae as illustrated and several PSS along lateral margin; article-2 about half length of article-1, with several simple setae and distal PSS; article-3 slightly less than half length of article- 2, with several simple distal setae; article-4 (common article) half-length of article-3. Accessory flagellum slightly shorter than main flagellum, with eight articles (second article with pseudo-articulation). Main flagellum with 12 articles, article-6 with one aesthetasc, two aesthetascs on articles 8 and 10.

Antenna ( Fig. 4A View FIGURE 4 ) peduncle with five articles; article-1 with antero-medial tooth-like projection, three dorsal plumose setae near medial margin; article-2 with one simple seta on inner margin and two simple setae on outer margin; squama slightly longer than combined length of articles 3 and 4, bearing 12 simple setae; article-3 short with one short and one long (broken off in illustration) seta on inner margin; article-4 twice length of article-3, bearing few PSS; article-5 slightly longer than article-4, bearing several simple on inner margin and few PSS on outer margin. Flagellum with eight articles (second article with pseudo-articulation).

Labrum ( Fig. 4B View FIGURE 4 ) with medial depression bearing hair-like setae on either side.

Mandibles ( Fig. 4C–F View FIGURE 4 ). Incisor process with five teeth and setiferous lobe with five spiniform setae in both right and left mandibles; lacinia mobilis of left mandible with four teeth; molar process with grinding surface having well-developed micro-denticles; palp article-1 shortest, about half length of article-2, bearing several simple setae, article-2 longest and both articles 1 and 3 bearing long simple and short pectinate setae.

Labium ( Fig. 4G View FIGURE 4 ) with outer margin spinulate, distal margin setulose; palp with lateral hair-like setae and three distal spiniform setae.

Maxillule ( Fig. 4H View FIGURE 4 ) inner endite with five setulate setae, both margins with hair-like setae; outer endite with 10 spiniform setae and two subdistal bipectinate setae, both margins with hair-like setae; palp biarticulate with six distally setulate setae increasing in length distally.

Maxilla ( Fig. 4I View FIGURE 4 ) inner lobe of fixed endite with posterior row of eight bipectinate setae increasing in length laterally and with long anterior row of setae; outer lobe of fixed endite with four trifurcate and quadrifurcate spiniform setae, one setulate spiniform seta, several simple and pectinate setae, posterior face with setulate spiniform seta; inner lobe of moveable endite with several simple and setulate setae; outer lobe of moveable endite with two pectinate, two plumose-denticulate, and several simple setae; outer distal margin serrate.

Maxilliped ( Fig. 5A View FIGURE 5 ) basis longer than broad, naked, outer distal corner produced into subacute apophysis; endite with inner margin having four coupling hooks, row of nine setulate setae and several distal simple and blunttipped setae, outer margin with short hair-like setae; palp article-1 with outer distal corner produced and bearing spiniform seta, inner distal corner with several long simple setae; article-2 with long (not illustrated) and shorter simple setae on inner and distal margins; article-3 as long as broad with several simple setae on inner distal corner; article-4 short with several distal simple setae.

Epignath ( Fig. 5B View FIGURE 5 ) with stout, setulate spiniform seta.

Cheliped ( Fig. 5C View FIGURE 5 ) basis about 2.7 times as long as broad with three spinules on ventral margin and three distoventral simple setae; merus about 2.8 times as long as broad with several simple setae; carpus elongate, narrow, about four times longer than broad with ventral, dorsal, and dorsodistal simple setae; propodus with several simple setae on outer face of palm, one simple seta on ventral margin, and four simple setae near dactylus insertion, fixed finger with two ventral simple setae, cutting edge with row of spinules and row of short simple setae on outer face; dactylus with row of spinules on cutting edge and three simple setae on inner face, unguis about half as long as dactylus; exopodite article-2 with two spinules on dorsal margin, last article with four plumose setae.

Pereopod-1 ( Fig. 5D, E View FIGURE 5 ) basis about twice as long as broad, with three or four ventrodistal simple setae and with or without a small ventrodistal spiniform seta; ischium with a few to several simple setae; merus widest distally, about 1.3 times as long as broad, with several simple setae on ventral margin and on inner and outer surfaces and a spiniform seta on ventrodistal and dorsodistal corners; carpus slightly longer than wide and with dorsodistal expansion, with simple setae on ventral and dorsal margins and on inner and outer surfaces, two ventral spiniform setae and dorsodistal spiniform seta nearly as long as propodus; propodus slightly shorter than carpus, with long simple setae on ventral, dorsal, and distal margins, four or five ventral spiniform setae and two dorsodistal spiniform setae; dactylus + unguis combined length subequal to propodus with three ventral spinules and minute seta proximal to junction with unguis, two minute proximally dorsal setae, unguis simple, about one third total length of dactylus; exopod last article with six plumose setae.

Pereopod-2 ( Fig. 6A View FIGURE 6 ) basis about 3.2 times as long as wide with spinule on ventral margin and several ventrodistal simple setae; ischium with four ventrodistal simple setae; merus almost twice as long as wide with ventrodistal spiniform setae, dorsodistal simple seta, and several simple setae on ventral margin and outer surface; carpus more than twice as long as wide with three spiniform and several simple setae on ventral margin and four spiniform setae and several simple setae on outer surface; propodus shorter than carpus, almost 2.5 times as long as wide with four spiniform setae and several simple setae on ventral margin and three spiniform setae and several simple setae on outer surface, one dorsal PSS; dactylus with minute proximal seta on dorsal margin, dactylus + unguis combined slightly shorter than propodus; unguis about one half total length of dactylus.

Pereopod-3 ( Fig. 6B, C View FIGURE 6 ) almost three times as long as wide with spinule on dorsal margin and three ventrodistal simple setae; ischium with five ventrodistal simple setae; merus similar to pereopod 2 merus; carpus about 2.5 times as long as wide with several simple on ventral margin and outer surface and two ventral, two outer, and two dorsodistal spiniform setae; propodus similar to pereopod 2; dactylus with minute distal seta on ventral margin.

Pereopod-4 ( Fig. 6D, E View FIGURE 6 ) basis slightly longer than twice the width with two ventrodistal simple setae; ischium with four ventrodistal simple setae; merus about twice as long as wide with several simple setae and one short and one long spiniform setae on ventral margin and short dorsodistal simple seta; carpus about 3.4 times as long as wide with six spiniform setae on outer surface near ventral margin and six ventral and distal spiniform setae, several ventral simple setae; propodus about half as long as carpus with five ventral simple setae and five long ventrodistal pectinate spiniform setae, outer surface with row of 14 short bipectinate spiniform setae, inner surface with row of nine short bipectinate setae, one proximal PSS on dorsal margin; dactylus with minute seta proximally on outer surface and minute seta distally on ventral margin; unguis subequal in length to dactylus.

Pereopod-5 ( Fig. 6F View FIGURE 6 ) basis about twice as long as wide with ventrodistal simple seta; ischium with four ventrodistal simple setae; merus similar to pereopod 4 but with three ventral spiniform setae; carpus about 2.5 times as long as wide with several simple and seven spiniform ventral setae, dorsodistal spiniform seta; propodus slightly longer than half the length of carpus with several ventral simple setae and nine ventral and distal spiniform setae, one PSS midway on dorsal margin; dactylus similar to pereopod 4; unguis shorter than dactylus.

Pereopod-6 ( Fig. 7A, B View FIGURE 7 ) basis about twice as long as wide with row of long plumose setae on outer surface near dorsal margin spanning entire margin, six plumose setae on outer surface near ventral margin, and one long plumose and two short simple ventrodistal setae; ischium with four simple ventrodistal setae; merus about 1.8 times as long as wide with three plumose setae on dorsal margin, three simple and spiniform setae on ventral margin, and one simple and one spiniform seta ventrodistally; carpus about 2.3 times as long as wide with four simple and spiniform setae on outer surface, several simple and four spiniform setae on ventral margin, dorsodistal spiniform seta, and plumose seta on dorsal margin; propodus longer than half the length of carpus with eight spiniform and several simple setae, five dorsodistal pectinate setae, inner surface with row of about 22 bipectinate spiniform setae, and one PSS midway on dorsal margin; dactylus with minute seta distally near dorsal margin; unguis + dactylus length combined subequal to propodus.

Pleopods ( Fig. 7C View FIGURE 7 ) foliaceous, basal article about 1.4 times as long as wide with numerous plumose setae on lateral margins; exopod shorter than endopod, with 41 plumose setae; endopod with 38 plumose setae (four short ones proximally on outer margin and one robust proximally on inner margin).

Uropod ( Fig. 7D View FIGURE 7 ) about half body length; basal article almost twice as long as wide with several distal simple setae; number of articles in exopod and endopod hard to discern due to multiple pseudo-articulations (only first article of endopod illustrated).

Male ( Figs 8 View FIGURE 8 , 9A View FIGURE 9 ) similar to female but with the following differences:

Pereon ( Fig. 9A View FIGURE 9 ) with one large hyposphenia behind maxilliped insertion, two small hyposphenia on pereonites 1-5, and one small hyposphenia and genital cone on pereonite-6.

Antennule ( Fig. 9B View FIGURE 9 ) accessory flagellum with 11 articles; main flagellum with 15 articles, two aesthetascs on articles 4, 5, 7, and 11, three aesthetascs on article-9, and one aesthetasc on article-13.

Antenna ( Fig. 9C View FIGURE 9 ) flagellum with nine articles (article-3 with pseudo-articulation), one aesthetasc on articles 2, 3, and 5.

Cheliped ( Fig. 10A–C View FIGURE 10 ) basis about 1.5 times as long as broad with one ventral spinule and three ventrodistal simple setae, linguiform proximal apophysis (not illustrated) present on inner surface; merus about 2.3 times as long a broad with two inner simple setae midway near ventral margin and several ventrodistal simple setae; carpus robust, about twice as long as broad with several simple setae on inner surface and ventral margin; propodus about 1.5 times as long as broad with several simple setae dorsodistally and on inner and outer surfaces; fixed finger about half as long as dactylus with two ventral simple setae, cutting edge with three small proximal teeth each with small seta and distal medial scalloped expansion, and several outer distal simple setae (only bases illustrated), distal nail minute; dactylus with large proximal tooth and four spinules distal to tooth on cutting edge and three subdistal inner simple setae, unguis about one third as long as dactylus.

Pereopod-1 ( Fig. 10D View FIGURE 10 ) basis with linguiform proximal apophysis on inner surface.

Intraspecific variation. The outer distal corner of maxilliped basis can vary in how much it is produced; pereopod-1 having posterior margin of propodus with four or five ventral spiniform setae and can vary in number of setae on ischium, from few to many ( Fig. 5D, E View FIGURE 5 ); the fixed finger of the male cheliped usually has three proximal teeth but can have four, two ( Fig. 10C View FIGURE 10 ), or one, a large distal tooth can be present with several spinules between it and nail, the ventral margin can have four simple setae; number of articles of antennae and number of setae on squama can slightly vary depending on developmental stage.

Type locality. Gulf of Mexico, Southwest coast of Mexico off the coast of Campeche, (18°51’0’’N, 91°57’35.9994’’W), depth 16 m in soft bottom substrata GoogleMaps .

Distribution. Known only from the type locality and adjacent benthic study station sites sampled during the present study.

Ecological observations. Sediment type consisted predominantly of silt (69% silt, 27% clay, and 4% sand). Other crustaceans co-occurring with M. boeschi , included a tanaidacean (Apseudes sp. A), amphipods (Ampelisca sp., Netamelita sp., and Idunella sp.]; decapods [Alpheus sp. and Pinnixa sp.]; and an undescribed apseudid tanaidacean.

Non-crustaceans commonly co-occurring with the new tanaidacean were polychaete worms [Armandia maculata (Webster), Nereis grayi Pettibone, Scoletoma verrilli (Perkins), Nephtys spp.]; bivalves [Varicorbula limatula (Conrad), and Abra aequalis (Say)]; a sipunculan (Apionsoma sp.), and the ophiuroid [Amphipholis squamata (Delle Chiaje)].

Remarks. Besides Mexctenapseudes boeschi n. sp., only two other parapseudid species, Discapseudes (Discapseudes) mexicanus Guţu, 2006 (= D. holthuisi sensu Escobar-Briones & Alvarez 1999) and Parapseudes sp. sensu Abarca–Ávila (2019) have been reported from the SW GoM Coast. Based on setation of pleotelson and other characters, Discapseudes (Discapseudes) mexicanus, which is euryhaline and occurs in coastal bays adjacent to the near shore type locality of M. boeschi , is distinctly different morphologically from the new genus (see Remarks for the genus). The genus Parapseudes is readily distinguished from M. boeschi by lacking an inflated merus and carpus of pereopod-1 and the absence of an anterodorsal row of setae on pleonite-1.