Mesanthura cocoae, Jarquín-Martínez & Gálvez-Zeferino & Morales-Zárate & Salinas-Zavala, 2023

Jarquín-Martínez, Ubaldo, Gálvez-Zeferino, Neysi, Morales-Zárate, María Verónica & Salinas-Zavala, César Augusto, 2023, Four new species of anthuroids (Peracarida: Isopoda) from the temperate-tropical transition zone of the western coast of Baja California Peninsula, Mexico, Zootaxa 5360 (1), pp. 91-112 : 102-106

Mesanthura cocoae sp. nov.

Figs 8–10

Material examined. Holotype: CIB-0063_ISO 10, adult female, 8.7 mm, Guerrero Negro Lagoon, Baja California Peninsula (station 4, in fine sand, 8.0 mm), Sep 12, 2017, coll. M. V. Morales-Zárate.

Paratype: CIB-0064_ISO 11, 9 adult females, same sampling station as holotype.

Additional material: CIB-0065_ISO 12, 5 adult females, station 10, in fine sand, 8.2 m, Dec 14, 2012, coll. M. V. Morales-Zárate; CIB-0066_ISO 13, 3 adult females, station 5, in fine sand, 8.2 m, Nov 7, 2012, coll. Morales-Zárate; CIB-0067_ISO 14, 1 adult female, station 8, in fine sand, 2.5 m, Nov 6, 2012, coll. M. V. Morales-Zárate; CIB-0068_ISO 15, 8 adult females, station 5, in fine sand, 8.2 m, Dec 4, 2012, coll. M. V. Morales-Zárate .

Diagnosis: Body 11.5 times longer than wide; pigment of pereonites 1–6 in circular shape; pigment of pereonite 7 rectangular. Article 3 of the mandibular palp with seven robust setae; projected molar process. Pereopod 1 palm projected medially, with one row of eight short setae. Pleopod 1 exopod operculiform, 1.8 times longer than wider, with 38 distal setae, endopod with nine distal setae. Pleotelson rounded with 10 apical setae.

Holotype description (adult female CIB-0063_ISO 10): Body length 8.7 mm ( Fig. 8A ), 11.5 times longer than wide; pigment of pereonites 1–6 in circular shape; pigment of pereonite 7 rectangular. Cephalon 1.1 times larger than wider, 0.7 times the length of pereonite 1. Pereonite 7 square, 0.7 times the length of pereonite 6. Pleon 1.1 times longer than wide and 1.2 times longer than pereonite 7; pleonites 1–5 completely fused. Pleotelson linguiform, rounded apex with 10 setae.

Antennula ( Fig. 8B ) with three peduncular and three flagellar articles. Article peduncular 1 1.7 times larger than wider, external margin with five plumose sensorial setae; article 2 subsquare, 0.5 times the length of the article 1, with three medial and three ventrodistal sensorial setae; article 3 cylindrical, 1.4 times larger than the article 2, with 4 distal simple setae. Flagellar article 1 with one plumose sensorial seta; article 3 with three aesthetascs and five simple setae.

Antenna ( Fig. 8C ) with five peduncular and five flagellar articles. Peduncular article 1 with one short seta; article 2 1.3 times longer than wide, with two distal setae; article 3 partially embedded in article 2, with two ventrodistal setae; article 4 subsquare, with a long and two short distal setae; article 5 cylindrical, 1.3 times larger than article 4, internal margin with a row of short setae. Flagellum much shorter than the last peduncular article; distal article minute, with numerous fine setae.

Mandible ( Fig. 8D ) palp with three articles. Article 1 elongated, cylindrical, 0.6 times the length of the second article, with a distal seta; article 2 cylindrical, with one short medial and one long distal seta; article 3 0.4 times the length of the article 2, with seven robust setae. Incisor with three cusps; lamina dentata with five denticles, projected molar process.

Maxilla ( Fig. 8E ) with eight distal teeth, dorsodistal margin with fine setae.

Maxilliped ( Fig. 8F ) palp with three articles. Article 1 rectangular, 0.6 times the length of the article 2, internal margin with two short and one long setae; article 2 with one short proximal seta; article 3 oblique, internal margin with three plumose setae, one proximal and two distal; medial margin with two long smooth and three short setae.

Pereopod 1 ( Fig. 9A, B ) subchelate. Basis more robust distally. Ischium thinner than the basis. Carpus triangular, rugose apical margin, with one mediodistal and four distal short setae. Propodus oval, palm projected medially with a row of eight marginal short setae, distal part with two long setae.

Pereopods 2–3 ( Fig. 9C, D ) similar in shape and setation. Basis oval-elongated, with dorsal plumose sensorial setae. Merus with 1–2 ventral and one dorsodistal seta. Carpus triangular, with four distal setae. Propodus cylindrical, 2.7 times longer than wide in P2 and 2.3 times longer than wide in P3, internal margin with one short spine seta and 4–5 simple setae.

Pereopods 4–7 ( Fig. 9E–G , 10A ) similar in shape and setation. Carpus pentagonal, with one ventrodistal short spine seta and 3–4 simple setae. Propodus cylindrical, with two ventromedial short setae, one ventrodistal short spine seta, and one long simple seta; internal margin of the propodus and dactylus of pereopod 7 with setulated scales.

Pleopod 1 ( Fig. 10B ) exopod operculiform, 1.8 longer than wide, distal margin with 39 plumose setae. Endopod cylindrical, as long as the exopod, 0.3 times the width of the exopod, with nine distal plumose setae.

Pleopod 2 ( Fig. 10C ) exopod 3.1 longer than wider, with 10 plumose setae. Endopod with eight distal setae.

Uropod ( Fig. 10D, E ) rectangular protopod, 2 times longer than wide and 1.7 times longer than the endopod; external margin with numerous plumose setae. Endopod sub-circular, 1.1 times longer than wider, margin with numerous smooth setae and some of them plumose. Exopod auriculiform, almost 2 times longer than wider, distal region emarginated, crenulated margin with numerous plumose setae accompanied with smooth ones.

Etymology: This species receives the nickname “Coco” in honor of Dr. María del Socorro García-Madrigal aka Coco, a Mexican scientist who has dedicated her scientific legacy to the study of marine crustaceans in Mexico.

Habitat: In soft bottom, fine sand.

Geographic distribution: Coastal lagoon of the temperate-tropical climatic transition zone of the Mexican Pacific, western coast of the Baja California Peninsula: Guerrero Negro Lagoon, Baja California, Mexico .

Remarks. Mesanthura cocoae sp. nov. differs from the previously recorded Mesanthura species by the following diagnostic characteristics: Pigmentation pattern; distal article of the mandibular palp with seven setae; molar process projected; pereopods 2–7 with scarce setae. M. cocoae sp. nov. is similar to M. occidentalis Menzies & Barnard, 1959 by showing the following characteristics: (1) palm of pereopod 1 medially projected; (2) propodus of pereopods 2–7 with ventral setulated scales; and (3) antennular flagellum with three aesthetascs. However, M. cocoae sp. nov. differs in the pigmentation pattern of pereonites 1–6, which is subcircular reticulated and rectangular in pereonite 7; the apical region of the pleotelson has six pairs of setae; setation of the antennae is scarce; article 3 of mandibular palp has seven setae, and the uropodal endopod is circular and 1.1 times longer than wide. In M. occidentalis the pigmentation of pereonites 1–6 is circular and distributed on the segment periphery, in pereonite 7 the pigment is a distal line; pleotelson apical region has eight pairs of setae; antennae show numerous short setae in the articles; article 3 of the mandibular palp with five setae; uropodal endopod is oval and as long as wide. This brings to six the number of species of Mesanthura from Mexico, the others being M. antenniformis Jarquín-Martínez & García-Madrigal, 2021 , M. estacahuitensis Jarquín-Martínez & García-Madrigal, 2021 , M. nubifera Wägele, 1984 , and Mesanthura sp. Brusca, 1980 .

Figures

FIGURE 8. Mesanthura cocoae sp. nov., holotype, female, 8.7 mm, CIB-0063_ISO 10, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, station 4. A) Body, dorsal view; B) antennula; C) antenna; D) mandible; E) maxilla; F) maxilliped.

FIGURE 9. Mesanthura cocoae sp. nov., holotype, female, 8.7 mm, CIB-0063_ISO 10, Guerrero Negro Lagoon, Baja California Peninsula, Mexico, station 4. A) Pereopod 1; B) palm of pereopod 1; C) pereopod 2; D) pereopod 3; E) pereopod 4; F) pereopod 5; G) pereopod 6.

FIGURE10. Mesanthura cocoaesp. nov., holotype,female, 8.7mm,CIB-0063_ISO10, Guerrero Negro Lagoon,Baja California Peninsula, Mexico, station 4. A) Pereopod 7; B) pleopod 1; C) pleopod 2; D) uropodal endopod; E) uropodal exopod.