Macrinella lavradoae Segadilha & Dos Santos & Serejo 2017, sp. nov.

Macrinella lavradoae sp. nov.

urn:lsid:zoobank.org:act: 74E71132-4585-49FD-8773-CD1F739E7872

Figs 1, 4–5

Diagnosis (based on female)

Pereonites with convex lateral edges. Pleon narrower than pereon. Pleotelson pentagonal, with rounded projection at the posterior edge. Antennule 0.6 times longer than carapace. All pereopods with coxae present. Pereopods 1–3 merus with short seta, not reaching carpus proximal edge. Pereopods 2–3 propodus with one penicillate terminal setae. Pleopods absent. Uropod exopod uniarticulate; endopod robust, with two articles.

Etymology

The new species is named in honour of Dr Helena Passeri Lavrado (IB/UFRJ) in recognition of her incentive and encouragement to the first author to initiate taxonomic studies on tanaidaceans. Moreover, she coordinates the subproject MABIREH and is a member of the committee board of the Instituto Nacional de Ciência e Tecnologia Antártico de Pesquisas Ambientais (INCT-APA).

Material examined

Holotype

ANTARCTICA: ♀, dissected, adult non-ovigerous, length 1.9 mm, Bransfield Strait, station #3, 62º17′26.4″ S, 58º19′49.5″ W, 1.153 m, 5 Dec. 2009 (MNRJ 24445).

Description

BODY (Fig. 4). About eight times as long as wide (broken in the pereonite 4). Cephalothorax oval, about 1.3 times as long as wide; eyelobes absent. All pereonites with convex lateral edges. Pereonite 1 shortest, 0.8 times longer than wide. Pereonites 2 and 3 longest, about as long as wide. Pereonite 5 slightly longer than pereonite 6, both about as long as wide. Pleon (Fig. 4) short, about 19% of body length, narrower than pereon. All pleonites sub-equal in size, wider than long. Pleonite 5 with lateral simple seta. Pleotelson pentagonal, slightly wider than long, with rounded projection at the posterior edge and with one pair of lateral and two pairs of terminal simple setae.

ANTENNULE (Fig. 4). With four articles, shorter than cephalothorax (about 0.6 times as long as carapace). Article 1 longest, about 1.8 times as long as wide, with one simple and five penicillate inner distal setae. Article 2 about as long as wide, with one simple and three penicillate inner distal setae. Article 3 stout, about 0.8 times as long as wide, with one simple and two penicillate outer distal setae. Article 4 slender, twice as long as wide, with five simple and two penicillate terminal setae.

ANTENNA (Fig. 4). With six articles. Article 1 short and fused to the cephalothorax, naked. Article 2 as long as wide, naked. Article 3 about 0.8 times as long as wide, with one simple outer distal seta. Article 4 longest, about 2.8 times as long as wide, with two simple and three penicillate distal setae. Article 5 narrow, 1.5 times as long as wide, with one distal simple seta. Article 6 minute, with five simple terminal setae.

MOUTHPARTS. Labrum (Fig. 4) rounded and setulose. Mandible molar process longer than incisor and relatively broad, distal part with few blunt denticles. Left mandible (Fig. 4) lacinia mobilis rounded, in the shape of two blunt spines, as long as incisor; incisor with two blunt denticles. Right mandible (Fig. 4) incisor with three blunt denticles. Labium not recovered. Maxillule (Fig. 5) endite with nine distal spiniform setulose setae. Palp slender, with two distal setae. Maxilla not recovered. Maxilliped (Fig. 5) basis rectangular and partly fused. Endites not fused, with one distal short seta and one small tubercular process. Palp article 1 smooth; article 2 with three inner penicillate and one outer simple setae; article 3 with three inner penicillate and one simple setae; article 4 with five inner setae (one simple, four penicillate) and one outer simple seta. Epignath not recovered.

CHELIPED (Fig. 5). Basis unequally divided by long prominent sclerite, shorter than carpus, proximal part wide, distal part narrow, attached to cephalothorax via large sclerite. Merus triangular, with one simple ventral seta. Carpus about 1.9 times as long as wide, no carpal shield, with two simple ventral and one minute dorsal setae. Propodus about three times as long as wide, with two simple setae on inner view. Fixed finger with three simple setae on cutting edge and two ventral simple setae. Dactylus slightly longer than fixed finger.

PEREOPOD 1 (Fig. 5). Coxa present (not figured). Basis slender and naked, four times longer than wide. Ischium with one simple seta. Merus about 1.7 times as long as wide, with one spiniform distoventral seta. Carpus longer than merus, with two simple and two spiniform distal setae. Propodus shorter than merus and carpus combined, with one spiniform distoventral seta and a row of spinules terminal setae. Dactylus 0.8 times as long as unguis. Dactylus and unguis combined as long as propodus.

PEREOPOD 2 (Fig. 5). Coxa present. Basis slender and naked, about 4.7 times as long as wide. Ischium with one simple seta. Merus about 1.2 times as long as wide, with one spiniform distoventral seta. Carpus longer than merus, with two distoventral and two distodorsal spiniform setae. Propodus shorter than merus and carpus combined, with one spiniform distoventral, a row of spinules and one penicillate terminal setae. Dactylus 0.7 times as long as unguis. Dactylus and unguis combined longer than propodus.

PEREOPOD 3 (Fig. 5). Similar to pereopod 2, except merus about 1.5 times as long as wide; propodus with one simple distodorsal, one spiniform distoventral and one penicillate terminal setae.

PEREOPOD 4. Missing.

PEREOPOD 5 (Fig. 5). Thicker than pereopods 1–3. Coxa present. Basis about 4.3 times as long as wide, with two midventral penicillate setae. Ischium short, with one simple seta. Merus about 1.7 times as long as wide, with two spiniform distoventral setae. Carpus longer than merus, with one simple and three spiniform distal setae. Propodus shorter than merus and carpus combined, with one penicillate mid-dorsal seta, one spiniform distodorsal and two distoventral setae. Dactylus about 1.1 times as long as unguis. Dactylus and unguis combined shorter than propodus.

PEREOPOD 6 (Fig. 5). Similar to pereopod 2, except for basis with one penicillate dorsal seta; propodus with three distodorsal and one spiniform distoventral setae.

PLEOPODS. Absent.

UROPOD (Fig. 5). Shorter than pleotelson. Basal article naked. Exopod uniarticulate, longer than half length of endopod first article, with one medial and two terminal simple setae. Endopod biarticulate, first article longer than second article, with one penicillate distal seta; second article with one simple medial, three penicillate and four simple terminal setae.

Remarks

The genus Macrinella is currently monotypic and includes Macrinella clavipes recorded from Davis Strait, Greenland (Lang 1971).

Macrinella lavradoae sp. nov. is distinct from M. clavipes in having:

(i) maxilliped endites with only one distal small tubercular process;

(ii) the dactylus of pereopods 5–6 short (1.2 times longer than wide);

(iii) pleopods absent;

(iv) the uropod exopod shorter than the first article of the endopod;

(v) the uropod about as long as the pleotelson;

(vi) the pleotelson with a rounded tip.

Macrinella lavradoe sp. nov. is a new record of the genus for Antarctica.

Distribution

Bransfield Strait, Antarctica, 1.153 m.