Mesokalliapseudes quadriflagellata, Drumm, David T. & Morales-Núñez, Andrés G., 2010

Drumm, David T. & Morales-Núñez, Andrés G., 2010, A new species of Mesokalliapseudes Lang, 1956 (Crustacea: Tanaidacea: Kalliapseudidae) from Puerto Rico, with remarks on the genus, Zootaxa 2687, pp. 45-55 : 46-54

publication ID	https://doi.org/ 10.5281/zenodo.199449
DOI	https://doi.org/10.5281/zenodo.6207119
persistent identifier	https://treatment.plazi.org/id/4C71879C-6525-FFE4-D0D3-01F4FEB8FCC2
treatment provided by	Plazi
scientific name	Mesokalliapseudes quadriflagellata
status	sp. nov.

Treatment

Mesokalliapseudes quadriflagellata View in CoL n. sp.

( Figs. 2–6 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Material examined. Holotype: adult female with oostegites ( USNM 1148172), Puerto Rico, Southwest of La Parguera, Isla de los Pájaros, 17°57.557΄N, 67°02.246΄W, 0.8 m depth, coll. Oct. 17, 2009. Allotype: adult male ( USNM 1148173), Puerto Rico, Southwest of La Parguera, Margarita, 17°55.337΄N, 67°07.084΄W, 16.8 m depth, coll. Feb. 2, 2010. Paratypes: 1 male, 1 juvenile, 1 manca ( USNM 1148174), same locality data as holotype; 1 ovigerous female, 1 juvenile, 3 mancas ( USNM 1148175), same locality data as allotype; 1 adult female with oostegites (partly dissected) ( USNM 1148176), Puerto Rico, Southwest of La Parguera, North El Palo, 17°56.249΄N, 67°06.192΄W, 9.4 m depth, coll. Aug. 1, 2008; 1 juvenile ( USNM 1148177), Puerto Rico, Southwest of La Parguera, El Peñón, 17°53.886΄N, 66°56.607΄W, 57 m depth, coll. Jun. 10, 2008; 3 juveniles ( USNM 1148178), Puerto Rico, Southwest of La Parguera, Margarita, 17°55.964΄N, 67°06.808΄W, 14.9 m depth, coll. Aug. 1, 2008.

Diagnosis (adult). Rostrum rounded. Pereonites lacking anterolateral apophyses. Pleotelson broader than long. Inner flagellum of antennule with four articles; first peduncle article approximately 3.5 times as long as broad. Third article of antenna without distinctive spinulate process. Mandibular palp terminally with plumose seta. Fixed finger of cheliped more than two-thirds length of dactylus. Pereopod 1 basis with serrate spiniform seta. Pereopod 6 propodus with four outer serrate spiniform setae; dactylus with one subterminal seta. Last article of uropod exopodite approximately 1.5 times as long as second article. Hyposphenia absent.

Etymology. Quadra (Lat.) + flagellatus (Lat.). Named after the 4-articulate inner flagellum of the antennule.

Description of adult female with oostegites. Body length ( Fig. 2 View FIGURE 2 A) approximately 5 mm, 5.8 times as long as broad.

Carapace ( Fig. 2 View FIGURE 2 A) as broad as long, one pair each of mid-lateral and dorsal setae; rostrum rounded.

Pereonites ( Fig. 2 View FIGURE 2 A). Pereonites 4 and 5 longest and subequal in length, pereonites 1 and 2 subequal in length and shorter than pereonite 3, pereonite 6 shortest, all rounded laterally; one to several simple setae on anterior corners, one or two simple setae on posterior corners, and at least one pair of dorsal simple setae; hyposphenia absent.

Pleonites ( Fig. 2 View FIGURE 2 A) subequal in length; epimera rounded, with several plumose setae and two pairs of short simple dorsal setae and one longer pair of lateral simple setae; hyposphenia absent. Pleotelson ( Fig. 2 View FIGURE 2 A) tapering posteriorly to rounded tip, with several lateral and dorsal simple setae; two long terminal plumose setae.

Antennule ( Fig. 2 View FIGURE 2 B). First peduncle article approximately 3.5 times as long as broad, with several simple and broom setae on outer margin and several simple setae on inner margin. Second peduncle article with several distal simple and broom setae. Third peduncle article with several distal simple setae. Fourth peduncle article with one simple and one broom setae. Inner flagellum with four articles, distal article with three simple setae; outer flagellum with 11 articles, nearly as long as peduncle, one aesthetasc each on articles 6, 7, 8 and 9, and three simple and one broom setae on distal article.

Antenna ( Fig. 2 View FIGURE 2 C). First article with medial extension bearing eight plumose setae. Squama with five simple setae. Third article short and rounded, with few spinules on inner margin. Fourth peduncle article shorter than first three flagellum articles together, with three proximal plumose and three distal simple setae on ventral surface, three broom setae on outer margin and two distal broom setae, and four simple setae on inner margin. Flagellum with seven articles bearing long, simple setae; distal article with five simple setae.

Labrum ( Fig. 2 View FIGURE 2 D) sub-rectangular bearing numerous hair-like setae.

Mandibles ( Figs. 2 View FIGURE 2 E, F). Right mandible ( Fig. 2 View FIGURE 2 E) with five-dentate incisor process and spine row with five spiniform setae. Left mandible ( Fig. 2 View FIGURE 2 F) with approximately nine denticulations on incisor process; lacinia mobilis appearing to have four denticulations; spine row with four spiniform setae. Mandibular palp terminating in short plumose seta.

Labium ( Fig. 3 View FIGURE 3 A). Distal margin provided with short hair-like setae and spinulate on outer margin. Palp with long hair-like setae.

Maxillule ( Fig. 3 View FIGURE 3 B). Inner endite bearing four terminally setulate setae and dense row of hair-like setae on outer and inner margins. Outer endite with seven long serrate, four long naked and one short spiniform setae, two subterminal setae and dense row of hair-like setae on outer and inner margins.

Maxilla ( Fig. 3 View FIGURE 3 C). Inner lobe of fixed endite with posterior row of two serrate spiniform setae and with long anterior row of filter setae. Outer lobe of fixed endite with three serrate setae, one plumodenticulate (bearing setules and denticles) and several simple setae distally and one short pectinate seta on posterior face. Inner lobe of moveable endite with one short plumodenticulate seta, two long serrate setae and several simple setae; outer lobe of moveable endite with two serrate and two plumodenticulate setae. Inner margin spinulate.

Maxilliped ( Fig. 3 View FIGURE 3 D). Basal article fringed with plumose setae on outer margin, four simple setae on inner margin. First article of palp with five simple setae on inner margin and three simple setae near outer margin. Last three articles of palp with double row of long plumose setae on inner margin; second article with one distal simple seta on outer margin; last article terminating in three simple setae. Endite with several pappose setae along margin (distal setae broken off and thus not illustrated); two coupling hooks. Epignath not examined.

Cheliped ( Figs. 3 View FIGURE 3 E, F). Basis with two simple ventrodistal setae. Merus with one long and one short simple setae. Carpus approximately 2.5 times as long as broad, with double row of long, plumose setae and two simple setae on dorsodistal corner. Propodus slender and very long, approximately 1.5 times as long as carpus, with diagonal row of long plumose setae on inner face; palm region with several long simple and serrate setae distally; fixed finger more than two-thirds length of dactylus, with several simple setae; cutting edge with 10 bipectinate spiniform setae interspersed with one to several spinules. Dactylus with three long setae on inner face (only the bases are shown on the whole cheliped illustration); cutting edge with nine spinules increasing in length distally, proximal ones interspersed with one or two short protuberances.

Pereopod 1 ( Figs. 4 View FIGURE 4 A, B). Basis with acute, proximal process, several short simple setae on dorsal margin and two setae (one serrate and one simple) ventrodistally. Ischium short with two simple setae on ventrodistal corner. Merus approximately 2.8 times as long as broad, approximately 3.4 times as long as carpus, with several simple setae on ventral margin, one ventrodistal spiniform seta, and one short dorsodistal spiniform seta. Carpus short with two ventrodistal and one dorsodistal spiniform setae, outer surface with row of small tubercles. Propodus shorter than carpus, three ventral and two dorsodistal spiniform setae; outer surface with small tubercles, inner surface with two short distal pectinate setae. Dactylus represented by sensory organ with numerous distal sensory setae and inner surface with two setae (one long and one short).

Pereopod 2 ( Fig. 4 View FIGURE 4 C). Basis approximately 3.5 times as long as broad, several short simple setae on dorsal margin, one simple and one spiniform ventrodistal setae. Ischium with two simple ventrodistal setae. Merus shorter than carpus, with two simple and one spiniform ventrodistal setae. Carpus approximately 1.7 times as long as broad, with seven short spiniform setae and two long dorsodistal setae. Propodus approximately onehalf length of carpus, with six spiniform setae, one long simple seta and one long serrate spiniform setae dorsodistally, one broom seta midway on dorsal margin. Dactylus long and slender, shorter than basis, with thin outer digitiform lobe terminating in three sensory setae.

Pereopod 3 ( Fig. 4 View FIGURE 4 D). Similar to pereopod 2. Carpus with eight spiniform setae. Proximal digitiform lobe of dactylus with four sensory setae.

Pereopod 4 ( Figs. 4 View FIGURE 4 E, F). Basis approximately 3.5 times as long as broad with two simple setae on dorsal margin and ventrodistal corner, and two broom setae on proximal outer surface near dorsal margin. Ischium with three simple setae. Merus shorter than carpus with three simple and one spiniform setae ventrodistally. Carpus with six spiniform setae on inner surface and six spiniform setae on outer surface, one long simple dorsodistal seta. Propodus with eight spiniform setae on each side increasing in length distally, one short pectinate seta on inner and outer surfaces and one broom seta proximally on dorsal margin. Dactylus represented by sensory organ with numerous distal sensory setae.

Pereopod 5 ( Figs. 5 View FIGURE 5 A, B). Similar to pereopod 4. Carpus with five spiniform setae on inner surface. Propodus without pectinate seta on the outer surface.

Pereopod 6 ( Fig. 5 View FIGURE 5 C). Basis with two long plumose setae on dorsal margin, one long plumose seta on ventral margin, four simple ventrodistal setae, and one proximal broom seta on outer surface. Ischium with three ventrodistal simple setae. Merus with four ventrodistal simple setae, and one plumose seta near dorsal margin. Carpus approximately two times as long as merus with seven simple setae near ventral margin and four distal simple setae. Propodus with four outer spiniform setae and approximately 21 inner bipectinate setae. Dactylus longer than propodus with one subterminal seta.

Pleopods ( Fig. 5 View FIGURE 5 D). Basal article with two long plumose inner setae. Exopodite biarticulate with one plumose seta on first article and 16 plumose setae on distal article. Endopodite uniarticulate with 17 plumose setae.

Uropod ( Fig. 5 View FIGURE 5 E). Exopodite with short basal article with one simple seta followed by two longer articles, last article approximately 1.5 times as long as second article and terminating in four simple setae. Endopodite multiarticulate (exact number unknown due to incomplete fusion in some articles).

Male. Similar to female but with the following differences:

Antennule ( Fig. 6 View FIGURE 6 A). First four articles of main flagellum each with cluster of aesthetascs.

Pereopod 6 ( Fig. 6 View FIGURE 6 B). Dactylus nearly as long as carpus and propodus combined.

The cheliped is illustrated ( Figs. 6 View FIGURE 6 C, D) in order to show that it is nearly identical to the female cheliped.

Manca. Exopodites on the last two pairs of pereopods present.

Distribution. Known only from Puerto Rico, 0.8–57 m (Figs. 1,8).

Remarks. Mesokalliapseudes quadriflagellata n. sp. can be distinguished from its congeners by the following combination of characteristics: 1) fixed finger of propodus more than two-thirds the length of the dactylus, and 2) inner flagellum of antennule with four articles. The only other congener that has the fixed finger of the propodus more than two-thirds the length of the dactylus is M. crassus ( Menzies, 1953) , but this species has a pointed rostrum, a more robust first peduncular article of the antennule, the antenna being more setose and with a distinct spinulate process on the third peduncular article, and the pereopod 6 being more setose and spinose. Mesokalliapseudes quadriflagellata also appears to be closely related to M. soniadawnae Bamber, 1993 , but can be distinguished by lacking anterolateral apophyses on the pereonites and by having a serrate spiniform seta on the first pereopod basis not as robust as that of M. soniadawnae . Mesokalliapseudes quadriflagellata is unique in having the inner flagellum of the antennule with four articles (all other congeners have three articles).

The nature of the chelae (i.e. ratio of fixed finger/dactylus length; spination on cutting edges) appears to be one of the most important characters for differentiating species of Mesokalliapseudes . Figure 7 View FIGURE 7 shows the chelae in all seven nominal species. Based on the morphology of the chelae, a potential quadriflagellata / crassus ( Menzies, 1953) and bahamensis Sieg, 1982 / viridis ( Menzies, 1953) relationship is supported which would make these two species-pairs trans-isthmian geminates. This can only be tested with a robust molecular phylogeny because a recent morphology-based cladistic analysis (Drumm, 2010) could not resolve the relationships within this genus. It has been shown that morphological similarities may hinder the accurate identification of trans-isthmian geminate species pairs ( Lessios, 1998; Craig et al., 2004).

The distribution of this genus occurs exclusively in the New World (western Atlantic/northeastern Pacific) ( Fig. 8 View FIGURE 8 ), and it would be interesting to investigate the role, if any, of the rise of the Isthmus of Panama over 16- 3 million years ago ( Coates and Obando, 1996) in the speciation of this group. The Isthmus of Panama separated the Pacific and Atlantic Ocean basins and created a barrier to gene-flow between marine organisms on either side, causing a large number of closely related species (geminate species pairs) to occur along the Atlantic and Pacific coasts. It is peculiar that no species have been discovered off the west coast of South America. This might be due to low sampling effort. It is expected that new species are yet to be discovered in the eastern Pacific.