Postispinatus youngi, Santos, Kátia Christol Dos, Santana, William & N, Ana Maria Setubal Pires - Va N I, 2012

Santos, Kátia Christol Dos, Santana, William & N, Ana Maria Setubal Pires - Va N I, 2012, Postispinatus youngi n. gen., n. sp. (Apseudomorpha; Tanaidacea; Crustacea): phylogenetic analysis and taxonomic remarks about kalliapseudids, Zootaxa 3192, pp. 24-38 : 28-36

publication ID	https://doi.org/ 10.5281/zenodo.215017
DOI	https://doi.org/10.5281/zenodo.6176096
persistent identifier	https://treatment.plazi.org/id/03A787CE-CD4C-FF90-569A-D4D4FBCEBA9D
treatment provided by	Plazi
scientific name	Postispinatus youngi
status	gen. nov.

Treatment

Postispinatus youngi n. gen., n. sp.

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

Type locality. off Rio de Janeiro, Campos Basin, Brazil.

Holotype: adult male, Campos Basin, 21°36' S – 40° 38' W, 26m, 30–VI–02, BMC–6–loc2 ( MNRJ 22874); Allotype: adult female, Campos Basin, 21°36' S – 40° 38' W, 26m, 30–VI–02, BMC–6–loc2 ( MNRJ 22875). Paratypes: Campos Basin, 21°36' S – 40° 38' W, 26m, 30–VI–02, BMC–6–loc2 (99 females, 6 adult males, 9 young males, 2 manca) ( MNRJ 17201); Campos Basin, 21°39' S – 40° 34' W, 23m, 01–VII–02, BMC–6–loc1 (2 females) ( MNRJ 17205).

Geographic distribution. BRASIL: Rio de Janeiro.

Additional material examined. BRAZIL: Rio de Janeiro: Arraial do Cabo, Massambaba beach, off Monte Alto, 30m, 30–X–86, (1 female) ( MNRJ 9385); same locality, 40m, 26–I–88, (1 female and 1 adult male) ( MNRJ 9387);

Description. (Female) Body ( Figs. 2 View FIGURE 2 A, B) dorsoventrally flattened, 3.5mm in length, about 7.5 times as long as wide. Cephalothorax as long as wide, same length as pereonite 2. Rostrum rounded. Eye lobes absent, without visual elements.

Pereon: pereonite 1 shortest, 5 and 6 same length; pereonites 2 to 4 quadrangular. Ventral apophyses absent. Last three pereonites bearing simple setae laterally.

Pleon: pleonites 1–4 with acute process laterally, pleonite 5 rounded ( Fig. 2 View FIGURE 2 .B1, dorsal view and Fig.2 View FIGURE 2 B.2, lateral view); all pleonites with two to five simple setae on lateral margins, without ventral processes. Pleotelson smaller than four pleonites combined, distal end acute, with several simple setae on inner and dorsal margins ( Fig. 2 View FIGURE 2 B.3).

Antennule ( Fig.2 View FIGURE 2 C) article-1 2.5 times as long as maximum width, four simple setae on inner side, six simple setae and broom seta on outer margin; articles-2 and 3 with three and two simple setae respectively; common article naked; inner flagellum with two articles and outer with seven articles, with aesthetascs and three terminal simple setae distally.

Antenna ( Fig. 2 View FIGURE 2 D) with nine articles, article-4 longest. Article-1 with inner margin laterally expanded, bearing short seta; squama with four long simple setae. Article-3 with simple seta on inner side. Article-4 with simple and broom setae. Article-5 with four long simple setae. Last three articles with simple setae.

Labrum ( Fig. 2 View FIGURE 2 E) with flat or slightly concave apex, setules present.

Mandibles ( Fig. 2 View FIGURE 2 F). Molar typical for Apseudomorpha, wide and with heavily chitinized apex ( Fig. 2 View FIGURE 2 F.1). Palp present, articles 1 and 2 approximately same length, article-3 about half length of articles 1 or 2. Article-2 with small spiniform serrated seta distally. Lacinia mobilis present only on left mandible, with two very small spines and large spiniform projection distally ( Fig. 2 View FIGURE 2 F.2). Setiferous lobe with simple setae originating from common peduncle ( Fig. 2 View FIGURE 2 F.3).

Labium ( Fig. 3 View FIGURE 3 A). Outer margin spinulate; with pair of palps, articulated, three simple setae apically; about 6 times as long as wide.

Maxillule ( Fig. 3 View FIGURE 3 B) with two endites, without palp; inner endite with three plumose setae apically, inner margin with lobe medially; outer endite with denticulate outer margin, three subterminal simple and nine apical setae, four of them blunt.

Maxilla ( Fig. 3 View FIGURE 3 C). Both margins with small rows of reduced setules; outer lobe of movable endite with simple setae, inner lobe with three distally pinnate setae. Outer lobe of fixed endite with simple and furcated setae; inner lobe with stout pinnate seta and row of basally–inflated setae.

Maxilliped ( Fig. 3 View FIGURE 3 D) coxa naked, as wide as basis; basis with four spiniform setae proximally on outer margin; endite with six thick plumoserrate setae, one plumose seta near midlength above them; inner margins with three and two coupling hooks, five plumose setae distally; palp articles 1 and 2 with simple seta on outer margin, distally; articles 2 to 4 inner margin with several simple setae, distally on article-3, terminally on article-4.

Epignath ( Fig. 3 View FIGURE 3 E) lobe narrower at the top, with terminal circumplumose seta, setulose.

Cheliped ( Fig. 3 View FIGURE 3 F) with 3-articled exopod bearing six plumose setae. Basis with three distoventral simple setae. Merus about half length of carpus with two proximoventral and three distoventral setae. Carpus four times as long as wide, with two simple setae on both sides. Propodus same length of basis, fixed finger with several simple setae distally and three simple setae next to articulation with movable finger. Dactylus with dentiform process proximoventrally, short simple setae distally near unfused unguis.

Pereopod 1 ( Fig. 3 View FIGURE 3 G) exopod 3-articulated, last article bearing six plumose setae. Basis enlarged, 1.7 times as long as wide, with five simple setae, broom seta proximodorsally, two simple setae distoventrally. Ischium not observed. Merus about twice as long as wide, with three simple setae on distal half of ventral margin, spiniform seta distoventrally, one distodorsally. Carpus short, with two spiniform setae with accessory setule distally, three simple setae distoventrally, three simple setae distodorsally. Propodus more globose than carpus, three spiniform setae with accessory setule ventrally intercalated with simple setae, four simple setae dorsally, followed by spiniform seta distodorsally; pinnate seta subterminally, next to the dactylus insertion; reduced ventral spiniform seta next to the unguis insertion.

Pereopod 2 ( Fig. 4 View FIGURE 4 A). Basis with three simple setae on first half dorsally, two distoventrally. Ischium short with small simple seta. Merus with spiniform seta distoventrally, two simple setae midventrally, three simple setae terminally. Carpus of same length as propodus with three spiniform setae ventrally, one spiniform distodorsal setae, each one bordered by simple seta. Propodus with four unequal spiniform ventral setae, two simple anterior setae ventrally, half disto-serrate setae terminally, two unequal spiniform setae distodorsally, broom seta on first half dorsally. Dactylus with fused unguis.

Pereopod 3 ( Fig. 4 View FIGURE 4 B). Basis with broom seta on each margin proximally; two long simple setae distoventrally, three simple setae on dorsal margin. Ischium short with short simple seta distoventrally. Merus with one spiniform and five simple setae ventrally. Carpus same length as propodus with three spiniform setae intercalated with four simple setae ventrally, two unequal spiniform and one simple setae distodorsally. Propodus with four unequal spiniform and three simple setae ventrally, broom seta mid-dorsally, two unequal spiniform distodorsal setae. Dactylus with fused unguis.

Pereopod 4 ( Fig. 4 View FIGURE 4 C). Basis with one long distal simple seta on both margins, three broom setae proximodorsally. Ischium as long as merus, with midventral simple seta. Merus with two spiniform setae and three simple setae distoventrally. Carpus 1.5 times as long as propodus with row of unequal spiniform setae on ventral margin; simple setae distodorsally. Propodus shorter than merus with broom seta dorsally; eleven distally- serrate setae terminally; dactylus bordered by two spiniform setae. Dactylus with fused unguis.

Pereopod 5 ( Fig. 4 View FIGURE 4 D). Basis with four simple setae on distal half and two broom setae proximodorsally, long simple seta distoventrally. Ischium with simple medioventral seta. Merus with one spiniform and four simple setae ventrally. Carpus 1.5 times as long as propodus with five spiniform and five simple setae on ventral margin. Propodus with three spiniform setae ventrally, three terminal, two smaller spiniform setae subterminally, broom seta mediodorsally. Dactylus with fused unguis.

Pereopod 6 ( Fig. 4 View FIGURE 4 E). Basis with row of seven simple setae increasing in length ventrally and three long simple setae distoventrally. Ischium short, with three simple setae. Merus with dorsal lobate expansion with three long circumplumose setae; row of twelve long simple setae ventrally. Carpus 1.25 times as long as propodus with row of fifteen long simple setae ventrally, two circumplumose setae dorsally. Propodus with row of eighteen half-pinnate setae, three long spiniform setae ventrally, three dorsally. Dactylus with fused unguis.

Pleopods ( Fig. 4 View FIGURE 4 F) basal article with long plumose seta; endopod with seven plumose setae; exopod biarticulated, proximal article with plumose seta, distal article with six plumose setae.

Uropods ( Fig. 4 View FIGURE 4 G) basal article with two curved spiniform processes; endopod with more than six articles (articulation between segments not clear), some articles with simple and broom setae circling the articles; exopod with three articles, articles 1 and 2 with one simple seta each, last article with three terminal simple setae.

Male. ( Fig. 5 View FIGURE 5 A, B) Cephalothorax twice as long as wide, approximately same length as first three pereonites combined in adults or first two pereonites in initial males.

Rostrum conspicuous, anterior margin of cephalothorax with three rounded projections, rostrum emerging between two projections over the antennule article 1.

Pereon pereonites 1 and 6 shortest, pereonite 2 quadrangular, pereonites 3–5 with similar shape, decreasing in length. All pereonites with two to five simple setae on lateral margins.

Mandibles similar to female; palp with strong sexual dimorphism ( Fig. 5 View FIGURE 5 A); article 1 about two times the length of articles 2 and 3 combined; article 1 almost 2.5 times as long as wide, with three simple setae; article 2 with one pinnate and one trifurcate distal setae on adults, juveniles with only pinnate seta; article 3 with row of simple setae terminally and pinnate seta.

Cheliped ( Fig. 5 View FIGURE 5 C) exopod with 3 articles, bearing five plumose setae. Basis with one distoventral and three terminal simple setae, three middorsal simple setae. Merus 3 times as long as wide with two midventral and one terminal setae. Carpus distally enlarged, with simple setae on both sides. Propodus well developed, about 1.7 times as long as wide, with simple setae on anterior half, row of simple setae terminally; fixed finger cutting edge with one large tooth with a rugose margin with few simple setae, followed by a deep depression and a lobe near to the fused unguis; fixed finger –dactylus– arched, with a tooth proximoventrally and several small simple setae terminally near the reduced unguis.

Ontogeny ( Fig. 6 View FIGURE 6 ). During the development of males there are proportional changes in the length of the article 1 of the mandible, cheliped and cephalothorax. We observed three stages in males: initial, intermediate and adult. In the initial stage, the article 1 of the mandible palp is approximately 1.4 times the length of article 2 ( Fig. 6 View FIGURE 6 C); in the intermediate stage this proportion increases to 1.8 times ( Fig. 6 View FIGURE 6 B) and in the adult stage to 3.5 times ( Fig. 6 View FIGURE 6 A).

Initial and intermediate males have the cephalothorax equivalent to the length of two pereonites combined ( Fig. 6 View FIGURE 6 L, M) while that in the adult is equivalent to the length of three pereonites combined ( Fig. 6 View FIGURE 6 K). The propodus of the cheliped of females ( Fig. 6 View FIGURE 6 G) has a similar shape to the initial stage of the males ( Fig. 6 View FIGURE 6 J), with a dentiform projection medially on fixed finger and a smaller one near the dactylus insertion; without a lobe on dactylus ventral margin. In the intermediate stage the propodus is much more expanded laterally ( Fig. 6 View FIGURE 6 H), the dentiform projection is more developed, increasing the concavity between the two dentiform projections, a proximal lobe on ventral margin of the dactylus is present.

Adult males have an extended propodus ( Fig. 6 View FIGURE 6 I) approximately 1.6 times as long as wide, with a conspicuous morphology on the fixed finger distal end, with several simple setae on ventral margin; dentiform process near junction with dactylus, with a rugose tip and four simple setae. Dactylus curved, with a dentiform process proximoventral; several simple setae distally, unguis diminute.

Manca. There are exopods on pereopods four and five ( Fig. 6 View FIGURE 6 E–F).

Etymology. This species is dedicated to the memory of Paulo Secchin Young, a gifted taxonomist with a great knowledge of marine biology and a great collector with profound concerns for biodiversity and conservation issues, along with a leader in the broad sense with indefatigable passion for his work ( Serejo & Paiva, 2006). He encouraged the first author (KCS) to pursue taxonomic studies of tanaids with the loan of material for post–graduate studies.

Remarks. The phylogenetic analysis reveals a group of characters that combined is diagnostic for Postispinatus youngi sp. nov.: (i) absence of maxillule palp; (ii) absence of aesthetasc on pereopod 1 dactylus; (iii) spiniform setae on dorsal margin of propodus of pereopod 6; (iv) mandibular palp tri-articled; (v) pereonite lateral apophyses smooth and (vi) with “square” form; (vii) pleon narrower than pereon; (viii) pereopod 3 with unguis; (ix) male cheliped with dentiform process on dactylus. Despite not having setae or a sensorial structure on the dactylus of pereopod 1, this species was considered as belonging to the Kalliapseudidae Lang, 1956 , based on presence of multiarticled exopods on pereopods four and five of the manca stage and the absence of a maxillule palp. The family Kalliapseudidae is being reviewed (D. Drumm pers. comm.) and it is suspected that the character “long sensory setae on the dactylus of the pereopods” as one defining feature of the family (Lang, 1956; Guţu, 2006) is incorrect. The genus Tanapseudes Bäcescu, 1978 (and re-examined by Hansknecht, Heard and Bamber, 2002) only has one short seta on the dactylus and it is not clear what “sensorial setae” actually means. The dactylus of members of the subfamily Kalliapseudinae have a unique sensory structure but this cannot be interpreted as being homologous across the entire family. These sensorial structures on pereopods were used to include Thaicungella in the Kalliapseudidae (Araújo-Silva & Larsen, 2010) , along with the absence of a palp on the maxillule. Apseudella (Apseudellidae) also does not have a maxillule palp so we suggest that there will be a cluster of combined characters to diagnose this family, including ontogenetical development. The discovery of Postispinatus without any “sensorial setae” confirms Drumm and Heard’s hypothesis that this character should not be used in the diagnosis of the family Kalliapseudidae ( Drumm & Heard, 2010).

Only two families of Apseudomorpha Sieg, 1980 do not have a maxillule palp, the Apseudellidae Guţu, 1972 (monotypic) and Kalliapseudidae . One morphological feature that differs between these two families is the epignath, large and kidney–shaped in Kalliapseudidae and small and falciform in Apseudellidae . The general body aspect of both families is distinct, as well as their bathymetric distribution (i.e. Apseudellidae in deep sea and Kalliapseudidae in shallow waters).

Another character that separates P. youngi from other apseudomorphs is the presence of a curved spiniform process on the basal article of the uropod. This structure differs significantly from that observed for Whiteleggiidae species by having two acute terminations instead of only one. This structure is unique (long and curved) with only one process found in the Whiteleggiidae Guţu, 1972 .

The number of articles on some appendages (e.g. antennule, antenna, mandible, maxillule, uropod) is crucial for identification of several families. The identification key for superspecific taxa of Apseudomorpha proposed by Guţu (1996), despite not being up–to–date, is still used. The Whiteleggiidae are found in juveniles to have spiniform projections on the uropod basal articles. However, examination of the other family diagnostic characters reveals that the palp of the maxillule is not present in the new species, but present and two-articled in the Whiteleggiidae . Species of the Whiteleggiidae have a highly calcified body with several carinas and tubercles, distinct from the new species that has a fragile body structure without ornamentation. In spite of these spiniform projections on the basal article of the uropod, which was used exclusively by Guţu (1996) to diagnose the Whiteleggiidae , we believe that with the inclusion of P. youngi , this concept will be changed. A currently proposed alternative would include this character with the presence or absence of the maxillule palp.

The monophyly of Kalliapseudidae is corroborated by our data as suggested by previous authors ( Drumm, 2010; Araújo-Silva & Larsen, 2010). The analyses also confirm the results of Araújo-Silva & Larsen (2010) as: (i) the genus Bacescapseudes is polyphyletic; (ii) T. lideeiensis belongs to Kalliapseudidae . The inclusion of P. m i r a - bilis shows that the genus Psammokalliapseudes is also polyphyletic. Thaicungella lideeiensis is not related to S. paulensis or S. fragilis , parapseudids included in these analyses. Also, T. lideeiensis forms a clade with P. m i r a b i l i s and B. grossidigitus , both kalliapseudids, supported by two homoplastic characters.