Atlantoscia australis Campos-Filho, Cardoso & Araujo, 2018

Zimmermann, Bianca Laís, Campos-Filho, Ivanklin Soares, Cardoso, Giovanna Monticelli, Santos, Sandro, Aguiar, José Otávio & Araujo, Paula Beatriz, 2018, Two new species of Atlantoscia Ferrara & Taiti, 1981 (Isopoda: Oniscidea: Philosciidae) from southern Brazil described in the light of integrative taxonomy, Zootaxa 4482 (3), pp. 551-565 : 555-560

Atlantoscia australis Campos-Filho, Cardoso & Araujo sp. nov.

Figs 4–6

Zoobank. urn:lsid:zoobank.org:act:39BAE885-6EE1-46A6-AAE0-60CAFC82FA41.

Etymology. The new species is named after the Triangulum australe constellation, located in the far of the southern hemisphere sky. This constellation represents the state of Santa Catarina in the Brazilian National flag.

Material examined. Holotype: Male, Santa Catarina, Santa Rosa de Lima , 28°06’09”S 49°07’35”W, alt. 225 m., 25 Jun 2012, leg. P.B. Araujo and B.L. Zimmermann ( MZUSP 36764 ) . Paratypes: 2 males (one in micropreparations), 9 females ( MZUSP 36765 ), same data as holotype .

Description. Maximum body length: male 5.5 mm, female 8.5 mm. Color light brown; antenna strongly pigmented; cephalon with irregular unpigmented spots; pereon with unpigmented spots on median and paramedian regions, epimera more pigmented with one or two unpigmented spots; pleonites 1 and 2 with two unpigmented spots, pleonites 3 and 4 with one unpigmented spot on median region and two unpigmented spots laterally, pleonite 5 more pigmented with one unpigmented spot on media region; telson with three unpigmented spots.

Body outline as in Fig. 4A . Cephalon ( Fig. 4B ) with lateral lobes not developed, frontal line absent, suprantennal line bent downwards on middle. Dorsum covered with elongated triangular scale-setae ( Fig. 4C ). Pereon ( Fig. 4A ) with pereonite 1 epimera directed frontwards, not surpassing eyes; pereonites 5–7 epimera gradually directed backwards; pereonite 7 with posterior margin arched. Pereonites with glandular pores on lateral margin. Noduli laterales coordinates as in Fig. 4D and E . Pleon ( Fig. 4A, F ) narrower than pereon; pleonites 3–5 epimera not well-developed, directed backwards. Telson ( Fig. 4F ) triangular, lateral sides almost straight.

Antennula ( Fig. 4G ) of three articles, distal article longest bearing eight lateral aesthetascs in four rows plus apical pair. Antenna ( Fig. 4H ) reaching pereonite 4 when extended backwards; flagellum of three articles, proximal and distal articles subequal in length, medial and distal articles bearing lateral aesthetascs, distal organ about half of length of distal article of flagellum.

Mandibles with dense cushion of setae, molar penicil of about five branches, left mandible ( Fig. 5A ) with 2+1 penicils, right mandible ( Fig. 5B ) of 1+1 penicils. Maxillula ( Fig. 5C ) inner endite with distal margin rounded bearing two hairy penicils; outer endite of 4+6 teeth, five of them with cleft at apex. Maxilla ( Fig. 5D ) inner lobe rounded bearing thick setae; outer lobe three times as wide as inner lobe covered with thin setae, distal margin sinuous. Maxilliped ( Fig. 5E ) basis subrectangular, palp with two long setae on proximal article, endite with distal margin rounded bearing two hook-like setae.

Pereopods ( Fig. 6A, B ) rather slender bearing fringe of scales on merus and carpus; carpus 1 with transverse antennal grooming brush and distal seta double fringed at apex. Dactylus ( Fig. 6A ) of two claws, inner claw not surpassing outer claw; ungual seta and dactylar organ simple, not surpassing outer claw.

Uropod ( Fig. 4F ) protopod subquadrangular, protopod and exopod grooved on outer margin bearing many glandular pores; exopod about twice as long as endopod; endopod inserted proximally.

Respiratory areas of floridana -type on pleopod exopods.

Male. Genital papilla ( Fig. 6C ) with triangular ventral shield, distal papilla bearing two subapical orifices. Pleopod 1 (Fix. 6D) exopod heart-shaped, outer margin concave bearing one small seta; endopod longer than exopod, distal portion slightly bent outwards bearing small setae on median margin and serrate plaque. Pleopod 2 ( Fig. 6E ) exopod triangular, outer margin concave bearing five small setae; endopod slightly longer than endopod. Pleopod 3 ( Fig. 6F ) exopod triangular, outer margin concave bearing three setae. Pleopod 4 ( Fig. 6G ) exopod triangular, outer margin slightly concave bearing four setae. Pleopod 5 ( Fig. 6H ) exopod triangular, outer margin sinuous bearing three setae.

Remarks. Atlantoscia australis sp. nov. differs from A. antennamaculata sp. nov. in having the distal portion of the telson triangular (vs. narrower in A. antennamaculata ), antennula with eight aesthetascs (vs. 11 in A. antennamaculata ), male pleopod 1 exopod with distal portion not elongated (vs. elongated in A. antennamaculata ), male pleopod 1 endopod with distal portion slightly directed outwards (vs. bent outwards in A. antennamaculata ), and male pleopod 5 exopod triangular (vs. rhomboid in A. antennamaculata ).

Phylogenetic Analysis. All specimens of A. antennamaculata sp. nov. and A. australis sp. nov. presented a single mitochondrial haplotype for the COI sequences. In addition, no intraspecific variation was found in the 18S sequences for both species. For this reason, the new species are represented, each one, by a single sequence in the phylogenetic trees. Final COI alignment consists of 640 bp, with 203 variable sites and 170 parsimony informative sites. On the other hand, final 18S alignment consists of 434 bp (including gaps), with 33 variable sites and 22 parsimony informative sites. Maximum likelihood and Bayesian analyses produced trees with similar topologies (data not shown). Although the phylogenies generated with mitochondrial COI ( Fig. 7 ) and 18S nuclear ( Fig. 8 ) sequences did not exhibit the same groupings among the Atlantoscia species, they were congruent regarding the taxa of interest; that is, both markers support the validity of the two new species of Atlantoscia . Some disagreement between the molecular markers is expected due to the different evolutionary rates between them. More specifically, the short size of the nuclear sequences added to their lower evolutionary rates may have generated the lack of congruence among some of the generated clades when compared to the mitochondrial tree. These results, however, do not interfere with the validity of the new species described herein. Sequences were deposited in GenBank under the accession numbers MH047282 to MH047285.3

The average mtDNA genetic distance among species of Atlantoscia was 13.9%, ranging from 13.4 to 20%. The genetic distance between A. antennamaculata sp. nov. and the other congeneric species was 15.4%; for A. australis sp. nov. this value was 17% ( Table 1). In relation to the conserved nuclear sequences, the average genetic distance among Atlantoscia species was 0.8%. The genetic distances between Atlantoscia species and the new species A. antennamaculata sp. nov. and A. australis sp. nov. were 1.2% and 0.7%, respectively ( Table 2).

Species delimitation. The likelihood of the null model in the GMYC analysis was significantly lower than the maximum likelihood of species delimitation (38.31 versus 45.11, ratio = 14.96, P = 0.001). As the null model assumes that all individuals within the sample belong to a single species, we reject this model. The GMYC analyses based on the COI dataset indicated the presence of 7 ML entities. Meanwhile, ABGD analysis with JC69 and K2P models produced ten recursive partitions, which recovered seven groups in all cases. These results support those of the phylogenetic analysis and confirmed the taxonomic validity of the currently recognized species of Atlantoscia .

Figures

FIGURE 4. Atlantoscia australis Campos-Filho, Cardoso & Araujo sp. nov., MZUSP 36765. Female paratype: A, habitus in dorsal view. Male paratype: B, cephalon in frontal view; C, dorsal scale-seta; D, b/c noduli laterales coordinates; E, d/c noduli laterales coordinates; F, pleonites 3–5, telson and uropod; G, antennula; H, antenna.

FIGURE 5. Atlantoscia australis Campos-Filho, Cardoso & Araujo sp. nov., male paratype, MZUSP 36765. A, left mandible; B, right mandible; C, maxillula; D, maxilla; E, maxilliped.

FIGURE 6. Atlantoscia australis Campos-Filho, Cardoso & Araujo sp. nov., male paratype, MZUSP 36767. A, pereopod 1, arrow indicating the dactylus; B, pereopod 7; C, genital papilla; D, pleopod 1; E, pleopod 2; F, pleopod 3 exopod; G, pleopod 4 exopod; H, pleopod 5 exopod.

FIGURE 7. ML tree based on COI mitochondrial sequences of Atlantoscia species. Numbers above branches represent bootstrap support. Codes next to the species names represent GenBank accession numbers of the analyzed sequences. New species are highlighted in gray.

FIGURE 8. Bayesian tree based on 18S rRNA nuclear sequences of Atlantoscia species. Numbers above branches represent Bayesian posterior probabilities. Codes next to the species names represent GenBank accession numbers of the analyzed sequences. New species are highlighted in gray.