Synchelidium purpurivitellum, Durham & White, 2023

Durham, Elizabeth L. & White, Kristine N., 2023, Caribbean Amphipoda (Crustacea) of Panama. Part I: parvorder Oedicerotidira, ZooKeys 1159, pp. 37-50 : 37

Synchelidium purpurivitellum sp. nov.

Figs 3 , 4 , 5 , 6B

Type locality.

Bocas del Toro, Panama: Crawl Cay, 9.2475°N, 82.1290°W, depth 5 m, in sand.

Material examined.

Holotype: Panama • 1 ♀, 2.3 mm; Bocas del Toro, Crawl Cay ; 9.2475°N, 82.1290°W; depth 5 m, in sand; 12 Aug 2021; K.N. White leg; USNM 1522429.

Paratypes: Panama • 1 ♂, 2.0 mm; same station data as for preceding; USNM 1522430 • 1 ♀, 2.0 mm; same station data as for preceding; USNM 1522431 .

Other material: Panama • 2 ♀, 1 ♂, 3 juvenile, same station data as for preceding; USNM 1522432 .

Diagnosis.

Gnathopod 1 propodus, palm regularly toothed. Gnathopod 2 propodus slender, 6 × length of dactyl. Pereopod 3 propodus with anteroproximal margin longer than anterodistal margin, dactylus short, stubby. Coxa 4 posteroventral angle slightly produced. Coxa 6 posteroventral angle narrowly rounded. Pereopod 7 merus with spines on posterior margin slightly shorter than width of article. Epimeron 3 anteroventral margin narrowly produced. Telson thickened dorsoventrally, narrowing distally, apex subtruncate with two medium setae dorsolaterally, two short setae medially.

Description.

Female (holotype, 2.3 mm). Head. Rostrum deflexed, reaching ventral margin of head, not surpassing article 1 of antenna 1. Eyes large, covering entire anterior portion of head. Antenna 1 length surpassing peduncle of antenna 2, moderately setose, peduncle segments subequal; flagellum 5-articulate. Antenna 2 is 1.2 × length of antenna 1, flagellum 5-articulate. Maxilliped, inner plate with four apical setae, outer plate with four or five distomedial, marginal setae. Lower lip, inner lobes rounded, outer lobes with large gape, apically setose. Maxilla 1 outer lobe with five apical plumose setae; palp bi-articulate, with three apical setae. Maxilla 2 inner plate with two apical setae, outer plate with three apical setae. Mandibles similar, incisors dentate; left mandible lacinia mobilis 6-dentate, right mandible lacinia mobilis 4-dentate; four accessory spines; molar process small; palp tri-articulate, article 2 with three setae, article 3 subequal in length with article 1, with two or three setae. Upper lip asymmetrical, apically setose.

Pereon. Coxae weakly setose on distal margin; coxae 1-3 subrectangular; coxa 4 subquadrate, slightly produced posterodistally. Gnathopod 1 subchelate; basis with few short setae on anterior margin; merus not expanded; carpal lobe reaching palmar angle, with two distal setae; propodus ovate, palm oblique, regularly toothed, defined by blunt tipped spine; dactylus reaching palmar angle. Gnathopod 2 chelate; basis slender, with one short seta on anterodistal margin; propodus minutely toothed on cutting edge of fixed finger, sparsely setose; total length of dactylus one-sixth of propodus, smooth. Pereopods 3 and 4 bases slender, with long plumose setae on anterodistal and posterodistal margins; propodus with anteroproximal margin longer than anterodistal margin; dactylus short, stout, one-fourth length of propodus. Pereopod 5 basis anterior margin with distally located plumose setae and a single row of medial plumose setae along the midline; propodus subequal to carpus. Pereopod 6 moderately setose; propodus subequal to carpus. Pereopod 7 basis subrectangular, lacking posterodistal lobe, posterior margin lined with short setae; dactylus styliform, at least as long as propodus (broken).

Pleon. Epimera 1-3 margins smooth, bare; epimeron 3, posteroventral margin evenly rounded. Uropod 1, peduncle 1.2 × length of outer ramus, inner and outer rami subequal in length, inner ramus with one robust marginal seta, outer ramus with four robust setae, inner and outer rami lined with fine setae. Uropod 2 peduncle subequal in length to outer ramus, inner ramus broken, inner ramus with one robust marginal seta, outer ramus with three robust setae, inner and outer rami lined with fine setae. Uropod 3 peduncle 0.3 × length of outer ramus, inner ramus 1.2 × length of outer ramus, each ramus with one robust seta, lined with fine setae. Telson thickened dorsoventrally, narrowing distally, apex subtruncate with two medium setae dorsolaterally, two short setae medially.

Male (paratype, 2.0 mm). Similar in all aspects to the female with the exception of the following: Eye slightly larger; antenna 2 flagellum elongate, at least 0.5 × body length (broken); gnathopods 1 and 2 bases slightly wider than in female.

Etymology.

After the Latin purpur, meaning purple and vitellum, meaning yolk and referring to the striking purple color of the eggs in the brood pouch of females of this species.

Distribution.

Panama: Bocas del Toro (present study).

Ecology.

These amphipods burrow into sand in shallow subtidal habitats.

Remarks.

Synchelidium purpurivitellum sp. nov. is similar to the geographically close species Americhelidium americanum in many aspects, but differs in having a strongly toothed gnathopod 1 propodal palm (smooth in A. americanum ), a broadly rounded posteroventral corner of epimeron 2 (produced in A. americanum ), and lacking the posterodistal lobe found on the basis of pereopod 7 in A. americanum .

Within the genus, Synchelidium purpurivitellum sp. nov. is most similar to Synchelidium maculatum Stebbing, 1906, sharing the long gnathopod 1 carpus and toothed propodus palm, minute pereopod 3 and 4 dactyls, and rounded posteroventral corner of epimeron 2. It differs from S. maculatum in having shorter antenna 1 flagellum, subrectangular gnathopod 1 propodus (ovate in S. maculatum ), and subtruncate telson (rounded in S. maculatum ). The subtruncate telson distinguishes S. purpurivitellum sp. nov. from all other Synchelidium species, but this character most resembles Synchelidium intermedium Sars, 1892, which has a truncate telson.

Figures

Figure 3. Synchelidium purpurivitellum sp. nov. holotype female, 2.3 mm, habitus; paratype male, 2.0 mm: head, antennae broken. Scale bars: 0.5 mm.

Figure 4. Synchelidium purpurivitellum sp. nov. holotype female, 2.3 mm, gnathopods 1 and 2 lateral, G 1 medial palm, left mandible, maxilla 1 and 2; paratype male, 2.0 mm: pereopod 7 (dactyl broken), telson. Scale bars: 0.1 mm.

Figure 5. Synchelidium purpurivitellum sp. nov. holotype female, 2.3 mm, antennae 1 and 2, pereopods 3 and 4, uropods 1 - 3; paratype male, 2.0 mm: maxilliped. Scale bars: 0.1 mm.

Figure 6. Photographs of live specimens A Hartmanodes nyei, male B Synchelidium purpurivitellum sp. nov. female. Scale bar: 1.0 mm.