Macrostylis cerritus, Vey & Brix, 2009

Vey, Aidan & Brix, Saskia, 2009, Macrostylis cerritus sp. nov., a new species of Macrostylidae (Isopoda: Asellota) from the Weddell Sea, Southern Ocean *, Zootaxa 2096 (1), pp. 356-370 : 358-367

publication ID	https://doi.org/ 10.11646/zootaxa.2096.1.21
DOI	https://doi.org/10.5281/zenodo.5334752
persistent identifier	https://treatment.plazi.org/id/03F787EC-AD68-5C2B-FF2A-82D6587C39DF
treatment provided by	Felipe
scientific name	Macrostylis cerritus
status	sp. nov.

Treatment

Macrostylis cerritus sp. nov. ( Figures 1 View FIGURE 1 –7)

Holotype: Female preparatory, length 1.8 mm, ZMH K-41431, station 78-9- E, Brenke sledge, depth 2149 m, RV Polarstern.

Paratypes: 1 subadult male, length 1.9 mm, not drawn for description, ZMH K-41432, allotype, same sample data as holotype ; 3 females, ZMH K-41433: 1 preparatory, length 2.8 mm, 2 unknown, lengths 2.3 mm, 2.0 mm, same sample data as holotype ; 9 females, ZMH K-41434 : 3 adult brooding, lengths 2.2 mm, 2.3 mm, 2.0 mm, 4 preparatory, lengths 1.6 mm, 1.7 mm, 1.8 mm, 1.7 mm, 2 unknown, lengths 2.0 mm, 2.4 mm, same sample data as holotype .

Type locality: ANDEEP III, station 78-9- E (71°09.52'S, 14°00.76'W) GoogleMaps .

Distribution. Known only from type locality.

Etymology. “cerritus”, Latin, meaning “crazy”, referring to the appearance of the species. During description we were talking about labelling the species as such because the ventral spines and dorsally oriented pereopod 3 with hook-like ischium make the species look like a “crazy little thing”.

Diagnosis. Body elongate, at least 4 times as long as broad. Head broader than long, not fused to first pereonite. Antennula short, of 5 articles, with one thick distal aesthetasc. Antenna with broom setae present only on article 5. Mandibles truncated and robust, incisor with 4 cusps, molar with many setulose setae at apex. Mandible with long robust seta laterally. Maxilliped palp with 5 articles and many short setae. Ventral spines present on pereonites 1, 6 and 7. Pereopod 3 with long, thin, curved ischium lobe. Pereopod 4 greatly reduced in size, juvenile looking. Operculum with strong spine-like unequally bifid setae ventrally. Pleopod 5 absent.

Description. Body approximately 3.1 mm long, almost 5 times as long as wide, body dorsum and margins smooth, without setae. Head almost as long as wide, almost as wide as pereonite 1, without eyes. Coxae not visible in dorsal view. Pereonites 1–3 strongly fused, with 1 and 2 shortest, 3 widest. Pereonites 5–7 with posteriorly directed small spines inserting apically. Distinct anterior-oriented spine on pereonite 1 ventrum, posterior-oriented spines on pereonite 6 and 7 ventrum. Pleotelson 0.24 times body length, 0.8 times body width, 1.4 times longer than wide, slightly shorter than pereonites 5–7 together. Anterior and posterior dorsal margins rounded.

Antennula ( Figure 2D View FIGURE 2 ) short, approximately 0.1 times body length, with 5 articles. Article 1 longest and widest, length 0.07 mm, width 0.04 mm, with 3 simple setae and 1 broom seta. Article 2 length 0.6 times article 1 length, width 0.8 times article 1 width, with 3 broom setae. Article 3 length 0.5 times article 1 length, width 0.6 times article 1 width, without setae. Article 4 length 0.25 times article 1 length, width 0.45 times article 1 width, distally with 1 simple seta. Article 5 minute, terminally with 1 aesthetasc.

Antenna ( Figure 2C View FIGURE 2 ) approximately 0.3 times body length, with 12 articles. Articles 1–3 small, article 1 with lateral simple seta, article 2 without setae, article 3 with 2 slender setae. Article 4 longest, slightly longer than article 5, without setae. Article 5 long and slender, distally with 5 broom setae and 2 whip (as in Brandt 1992) setae. Distal 7 flagellar articles small, of subequal length, eighth, ninth and eleventh article each with 1 slender seta, terminal article with distal sensory setae.

Mandibles ( Figure 3A, 3B View FIGURE 3 , 6A View FIGURE 6 ) without palp, palp replaced with robust seta (missing on left mandible), both with 4 cusps on incisor. Right setal row with 5 robust setulose setae and 2 attenuating simple setae, left setal row with 5 robust setulose, 1 setulose simple attenuating seta and 1 simple attenuating seta. Lacinia mobilis of left mandible with 3 teeth, right with 2. Molar a distinct process, with a dense row of 9 setulose slender setae.

Maxillula ( Figure 2B View FIGURE 2 ) mesial lobe stalked, with 12 setae, and slightly smaller than lateral lobe. Lateral lobe length 2.2 times width, dorsal margin with 12 setae, ventral margin with 8 setae, terminally with 11 strong spines (3 of which serrated).

Maxilla ( Figure 2A View FIGURE 2 ) mesial lobe shorter than middle and lateral lobes. Mesial and lateral lobes distally with 2 long and 1 setulose setae, and a number of setae pairs laterally. Lateral lobe length 6.9 times width. Mesial lobe length 4.7 times width, distally with 3 large and 3 small robust setae. Laterally with 12 long slender setae.

Maxilliped ( Figure 2E View FIGURE 2 , 6B View FIGURE 6 ) epipodite length 2.7 times width, length 0.8 times endite length. Endite with 2 retinaculae, 1 lateral simple seta, distally with 3 fan setae, 8 simple setae and many marginal fine setae. Palp inserted at approximately two thirds the basis length, width 0.6 times length and palp length about 0.5 times basis length; palp article 1 with some marginal fine setae; palp article 2 about 5 times as long as article 1, almost twice as wide as article 1, with 4 medial and 1 distolateral setae; article 3 approximately a third the length of article 2, with 6 setae; article 4 less than half the width of article 3 width, with 3 distal setae; article 5 narrower than article 4, with 5 setae.

Pereopod 1 ( Figure 3C View FIGURE 3 ) basis length 2.9 times width, dorsally with 4 short setae, ventrally with 1 short slender and 1 long slender setae. Ischium length 2.4 times width, dorsally with 2 long slender setae, ventrally with 1 robust simple seta, laterally with 3 long slender setae. Merus length 1.8 times width, dorsally with 1 distally setulate seta, ventrally with 2 robust setae, laterally with 4 long slender setae. Carpus length 1.4 times width, ventrally with 1 distally setulate and 1 robust setae, laterally with 1 robust simple and 1 short robust simple setae, distally with 1 long robust seta. Propodus length 3 times width, dorsally with 1 slender seta, ventrally with 3 short simple setae. Dactylus length 4.4 times width, claw composed of 1 conate and 1 cuspidate setae with 2 slender setae inserting in between, 2 slender setae inserting terminally into conate setae.

Pereopod 2 ( Figure 3D View FIGURE 3 ) basis length 3.1 times width, dorsally with 4 simple setae, ventrally with 3 simple and 1 long slender setae. Ischium length 2.9 times width, dorsally with 2 simple setae, ventrally with 1 minute seta, laterally with a composed row of 5 long slender setae. Merus length 1.6 times width, dorsally with 1 robust unequally bifid seta, ventrally with 2 unequally bifid and 1 simple setae, laterally with a (composed) row of 5 long slender setae. Carpus length 2.4 times width, dorsally with 2 long simple, 1 small broom and 1 long simple setae, ventrally with 2 unequally bifid setae. Propodus length 3.1 times width, dorsally with 1 unequally bifid and 1 broom setae, ventrally with 1 simple seta. Dactylus length 3.7 times width, claw composed of 1 conate and 1 cuspidate setae with 2 slender setae inserting in between, 2 slender setae inserting into conate seta.

Pereopod 3 ( Figure 3E View FIGURE 3 ) basis length 2.4 times width, dorsally with 1 simple seta, ventrally with 3 simple slender and 1 unequally bifid setae. Ischium length 2.3 times width, dorsally with large hook-shaped triangular lobe, 1 short slender and 4 long slender setae. Merus length 1.4 times width, dorsally with a row of 4 long simple setae and a row of 4 robust unequally bifid setae, ventrally with 1 small simple seta. Carpus length 2.8 times width, dorsally with a row of 5 long simple setae. Propodus length 2.5 times width, dorsally with 1 small simple seta, ventrally with 1 simple seta, distally with 1 simple seta. Dactylus length 1.1 times width, claw composed of 1 conate and 1 cuspidate setae with 2 slender setae inserting in between, 1 terminal slender seta and 1 simple seta inserting ventrally into conate seta.

Pereopod 4 ( Figure 4A View FIGURE 4 ) short, only half the length of pereopod 3. Basis length 3.4 times width, dorsally with 1 broom seta, ventrally with 1 broom and 3 slender simple setae. Ischium length 2.8 times width, dorsally with 1 slender simple and 1 simple setae. Merus length 1.7 times width, ventrally with 2 distal simple robust setae, distally with 1 simple robust and 1 long simple robust setae. Carpus length 2.3 times width, ventrally with 2 robust setae, distally with 1 long and 1 short robust setae. Propodus length 2.3 times width, distally with 1 short robust and 1 long robust setae. Dactylus very compressed with one terminal robust seta.

Pereopod 5 ( Figure 4B View FIGURE 4 ) basis length 2.9 times width, dorsally with 2 long simple robust (1 broken) setae, ventrally with 2 small broom, 1 simple slender and 1 large broom setae, distally with 1 robust simple seta. Ischium length 3.3 times width, dorsally with 1 unequally bifid seta, ventrally with 2 simple and 1 long slender setae, distally with 2 long slender setae. Merus length 2.4 times width, ventrally with 2 sets of an unequally bifid and simple setae, distally with 4 unequally bifid setae. Carpus length 4.5 times width, dorsally with 1 broom seta, ventrally with 1 unequally bifid seta, distally with 3 short unequally bifid and 1 long unequally bifid setae. Propodus length 5.1 times width, dorsally with 1 simple and 1 broom setae, ventrally with 1 unequally bifid seta, distally with 1 unequally bifid and 1 long slender setae. Dactylus length 3.5 times width, terminally with 2 unequally bifid setae with setulose smaller lobes.

Pereopod 6 ( Figure 4C View FIGURE 4 ) basis length 2.7 times width, dorsally with 1 unequally bifid, 1 simple and 3 slender setae, ventrally with 3 slender setae, distally with 1 robust seta. Ischium length 2.7 times width, dorsally with 2 simple and 1 unequally bifid setae, ventrally with 5 slender setae. Merus length 2 times width, ventrally with 1 simple seta, dorsally with 5 short, 2 long unequally bifid and 1 simple setae. Carpus length 6 times width, dorsally with 1 broom seta, ventrally with 1 simple seta, distally with 1 unequally bifid and 1 long setae. Propodus length 8 times width, distally with 1 long slender, 1 unequally bifid and 1 broom setae. Dactylus length 5.8 times width, distally with 1 open-ended sensory seta and 1 unequally bifid seta.

Pereopod 7 ( Figure 4D View FIGURE 4 ) basis length 3 times width, dorsally with 10 long distally slender plumose setae, 6 slender setae (1 broken), 1 short simple seta and 1 unequally bifid seta, ventrally with 4 slender setae. Ischium length 3.4 times width, dorsally with 2 distally setulate and 1 unequally bifid setae, ventrally with 1 distally setulate and 1 distal simple setae. Merus length 2.4 times width, ventrally with 1 simple seta, distally with 4 unequally bifid and 1 robust unequally bifid setae. Carpus length 6.3 times width, ventrally with 1 simple seta, distally with 2 unequally bifid, 2 simple and 1 short robust setae. Propodus length 8.8 times width, dorsally with 1 broom seta, ventrally with 2 slender setae, distally with 2 long distally setulate setae. Dactylus length 4.7 times width, terminally with 1 long distally setulose and 1 long unequally bifid setae.

Operculum ( Figure 5B View FIGURE 5 ) length 1.5 times width. Ovoid, tapering towards posterior, broadest medially, narrower towards anterior. Mediolaterally with 11 slender setae on both sides. Ventrally with 5 robust setae inserting towards both the left and right margins. One distally setulose unequally bifid seta inserting towards posterior near the mediocentral line. Caudally with a row of 18 long and slender plumose setae.

Pleopod 3 ( Figure 5C View FIGURE 5 ) endopod length 1.5 times width, distally with 3 plumose setae. Exopod length 6.2 times endopod length, reaching almost as far as endopod, laterally with many slender setae, of which the anterior half are long and insert into a groove, distally with 9 setae.

Pleopod 4 ( Figure 5D View FIGURE 5 ) endopod quadrangular, length 1.6 times width, distally with 1 minute seta. Exopod length 5.5 times width, outer margin with row of 20 slender setae, distally with 1 plumose seta, exceeding length of endopod.

Pleopod 5 absent

Uropods ( Figure 5A View FIGURE 5 ) uniramous, sympod 4 times ramus length, 17 times longer than wide, with 9 broom setae of varying lengths. Ramus 5 times longer than wide, distally with 2 broom setae and 1 (broken) seta.