Sicifera cahawba, Cannizzaro & Daniels & Berg, 2022

Cannizzaro, Andrew G., Daniels, James D. & Berg, David J., 2022, Phylogenetic analyses of a new freshwater amphipod reveal polyphyly within the Holarctic family Crangonyctidae, with revision of the genus Synurella, Zoological Journal of the Linnean Society 195, pp. 1100-1115 : 1105-1112

SICIFERA CAHAWBA SP. NOV.

( FIGS 3–10 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: AF8DF95F-3679-4C14-B754-506892A1CED5

Type material

Holotype, male, 6.38 mm: Old Cahawba Prairie Fo r e v e r Wild T r a c t, D a ll a s C o u n t y, A L, U S A (32.319696, − 87.104513); collector: James D. Daniels, 20 February 2020; USNM 1660542 . Allotype, female, 8.27 mm: Old Cahawba Prairie , Dallas County, AL, USA (32.32048, −87.10624); collector: James D. Daniels, 20 February 2020; USNM 1660543 . Paratype female, 5.15 mm: Old Cahawba Prairie Forever Wild Tract, Dallas County, AL, USA (32.319696, −87.104513); collector: James D. Daniels, 28 February 2019; USNM 1660544 . Paratypes, three females: Old Cahawba Prairie Forever Wild Tract, Dallas County, AL, USA (32.319696, −87.104513); collector: James D. Daniels, 20 February 2020; USNM 1660545-47 .

Type locality: Old Cahawba Prairie , Dallas County, AL, USA (32.32048, −87.10624) .

Etymology

The specific epithet cahawba is given in direct reference to the distribution of the species, which is currently endemic to the Old Cahawba Prairie in Dallas County, AL, USA. The name is probably a corruption of two Choctaw words: oka, meaning water, and uba, above ( Owen & Owen, 1921).

Diagnosis

Medium-sized epigean species distinguished from all other members of the genus Sicifera by the combination of the following characteristics: maxilla 1 inner plate with up to eight setae; gnathopod propodi rectangular, 1.5–1.7× longer than tall; palmar margins concave, armed with ≤ 19 large robust setae; propodi with superior medial setae singly or doubly inserted; inner margin of gnathopod dactyli of females with six serrations; gnathopod bases of females armed with numerous long setae; uronites fused (not free); telson of male with weakly bifurcate apices, cleft width-todepth ratio of four, 50% cleft; female telson 40% cleft. Females ≤ 8.5 mm long, males ≤ 6 mm long.

Description: male ( Figs 3–8 )

Length 6.38 mm. Eyes circular to ovate in shape, pigmented ( Fig. 3A ). Interantennal lobe narrow, with rounded upper and lower margins. Integumentary pigment bluish grey or brown when alive.

Antennae: Antenna 1 ( Fig. 4A ): 58% body length, 1.9× longer than antenna 2; peduncle segment 1 with three lateral setae, plumose setae absent; primary flagellum with 21 segments, aesthetascs present on distal segments, aesthetascs shorter than respective segments; accessory flagellum two-segmented, shorter than first flagellar segment in length. Antenna 2 ( Fig. 4B ): gland cone distinct; peduncle 1.5× longer than flagellum, with one robust seta placed laterally on segment 3 and plumose setae placed on distal margins of segments 4 and 5, peduncular segment 4 subequal in length to segment 5; calceoli present on flagellum and peduncular segments 4 and 5; flagellum eight-segmented.

Mouthparts: Mandibles ( Fig. 4C, D ): left mandible incisor five-dentate, lacinia mobilis six-dentate, with seven robust and plumose accessory setae; molar process developed with one plumose seta; palp threesegmented, second segment subequal in length to third, with nine alpha setae and three beta setae, outer margin of segment covered in fine setae; third segment rounded distally, inner margin straight, with two C-setae, five E-setae, two A-setae, two B-setae and 11 plumose D-setae, face of segment covered in numerous, fine pubescent setae. Right mandible, incisor three-dentate, lacinia mobilis bifurcate, proximal lobe with numerous fine dentations, distal lobe with four dentations; accessory setae row with six robust and plumose setae; molar process and palp as in left mandible. Upper lip ( Fig. 5A ): rounded, apical margin of labrum with numerous fine setae. Lower lip ( Fig. 5B ): inner lobes reduced, outer margin of both inner and outer lobes covered in numerous fine setae; face of lip pubescent. Maxilla 1 ( Fig. 5C ): inner plate with eight plumose marginal setae and fine pubescence covering entire plate; outer plate with seven apical comb-spines, pubescence covers entire plate, decreasing laterally; palp two-segmented, distal segment covered in pubescence; apical margin of distal segment with three submarginal setae and seven marginal setae. Maxilla 2 ( Fig. 5D ): both inner and outer plates covered in pubescence; outer plate subequal in length to inner plate, with 23 apical setae; inner plate narrowing slightly distally, with 20 apical setae and nine plumose facial setae. Maxilliped ( Fig. 5E ): inner plate much shorter than outer plate, with three unarmed spine-teeth along apical margin and five plumose inner marginal setae, surface of plate covered in fine pubescence; outer plate armed with numerous setae, surface of plate covered in fine pubescence; palp four-segmented, second segment with 25 marginal and submarginal setae on inner margin and one distal outer marginal seta, third segment with numerous distal setae, lateral surface pubescent marginally; dactylus with three inner setae.

Gnathopods: Gnathopod 1 ( Fig. 6A ): coxal plate with seven apical setae and sparse amounts of short facial setae; basis with one anterior and five posterior setae, along with two shorter posterodistal setae, small patches of pubescence are present on posterodistal and posteroproximal corners; ischium with five setae and pubescence along the posterior margin; merus with pubescence covering posterior surface and 15 plumose posterodistal setae; carpus 70% length of propodus, with two anterior setae, six posterior setae and five medial setae; propodus 1.6× longer than broad, with four superior medial setae, six inferior medial setae and five posterior setae, anterodistal margin of propodus ending with small spine-like projection covered by tuft of setae; palm slightly convex, with seven inner robust setae and ten outer robust setae; defining angle armed with four inner and outer robust setae; dactylus inner margin not dentate, outer margin with two setae. Gnathopod 2 ( Fig. 6B ): coxal plate with seven apical setae and sparse amounts of short facial setae; basis with two anterior and five posterior setae, along with two shorter posterodistal setae, a small patch of pubescence is present on posterodistal corner; ischium with two setae and pubescence along the posterior margin; merus with pubescence covering posterior surface and eight plumose posterodistal setae; carpus 55% length of propodus, with four anterior setae, four groups of posterior setae and three medial setae; propodus 1.7× longer than broad, with two anterior setae, five superior medial setae (distal-most paired), six inferior medial setae and four groups of posterior setae, anterodistal margin of propodus ending with a small spine-like projection covered by a tuft of setae; palm slightly convex, with nine inner robust setae and five outer robust setae; defining angle armed with two inner and five outer robust setae; dactylus inner margin not dentate, outer margin with three setae.

Pereopods: Pereopod 3 ( Fig. 7A ): coxal plate with seven apical setae and sparse facial setae; basis with numerous anterior and posterior setae; merus 1.4× longer than carpus, carpus 90% length of propodus; dactylus 42% length of propodus, with one plumose seta on outer margin and two inner marginal setae. Pereopod 4 ( Fig. 7B ): subequal to pereopod 3 in length; coxal plate 2× longer than broad, with distinct excavation along the posteroproximal margin, armed with nine apical setae and sparse facial setae; merus 1.2× longer than carpus, carpus 90% length of propodus; dactylus ~53% length of propodus, setation like pereopod 3. Pereopod 5 ( Fig. 7C ): coxal plate large, bilobate, with distinct anterior and posterior lobes, posterior lobe with three setae; basis posterior margin weakly convex with seven shallow serrations and a convex distal corner, anterior margin with seven split-tipped robust setae and three distal setae, face of segment with sparse setae; merus 90% length of carpus; carpus subequal to propodus in length; dactylus 40% length of propodus, setation like other pereopods. Pereopod 6 ( Fig. 7D ): coxal plate bilobate, with produced posterior lobe, posterior lobe bearing one apical seta; basis posterior margin slightly convex with ten shallow serrations and a straight distal corner, anterior margin with seven split-tipped robust setae, face of segment with sparse setae; merus 85% length of carpus; carpus 80% length of propodus; dactylus 30% length of propodus, setation like other pereopods. Pereopod 7 ( Fig. 7E ): coxal plate lobes indistinct, with a single posterior seta; basis posterior margin convex with 12 serrations and a slightly convex distal corner, anterior margin with six split-tipped robust setae and three distal robust setae, face of segment with sparse setae; merus 73% length of propodus; carpus subequal to propodus in length; dactylus 30% length of propodus, setation like other pereopods.

G i l l s (Fi g s 6B, 7A –E): C o x a l g i l l s p r e s e n t o n somites 2–5; somite 7 with pereopod 7 gill subequal in size to coxal gills. Sternal gills present on somite 6.

Pleosome: Second and third segments with one or two setae arising on dorsodistal margins. Pleopods ( Fig. 8A–C ): peduncle of pleopod 1 55% length of rami, with two setae and two coupling hooks; outer and inner rami with 12 and 14 segments, respectively, basal segment of outer ramus with clothes-pin setae. Pleopod 2 peduncle similar to first, with two coupling hooks; outer and inner rami with 12 and 13 segments, respectively. Pleopod 3 peduncle like first and second, with two coupling hooks; outer and inner rami with 12 and 13 segments, respectively. Epimera ( Fig. 8D ): first epimeron ventral margin unarmed, distoposterior corner with small toothlike extension, posterior margin with one seta placed proximally from distoposterior corner; second epimeron ventral margin with two robust setae, distoposterior corner with tooth-like extension, posterior margin with one seta; third epimeron ventral margin with three robust setae, distoposterior corner with small tooth-like extension, posterior margin with one seta.

U r o s o m e: B a r e d o r s a l l y, s e g m e n t s 1–3 f u s e d. Uropod 1 ( Fig. 8E ): peduncle 1.3× length of rami, with six inner robust setae and five outer robust two plumose setae arising dorsolaterally from outer margins of both lobes.

Description: female ( Figs 3 , 9 , 10 )

Length 8.27 mm. Differing from male in larger body length; lack of calceoli on peduncle and flagellum of antenna 2; presence of more robust gnathopods with more setae on bases, enlarged propodi, more robust setae on palmar margins, convex palms and dentate inner dactyli margins; uropod 1 setation; uropod 2 setation; uropod 3 structure; and telson shape. Structures not described below are as in male.

Antennae: Antenna 1 ( Fig. 3B ): ~52% body length, 2.2× longer than antenna 2; primary flagellum with 24 segments; accessory flagellum two-segmented, shorter than first flagellar segment in length. Antenna 2 ( Fig. 3B ): gland cone distinct, peduncle 1.2× longer than flagellum, calceoli absent on both peduncle and flagellum; flagellum seven-segmented.

setae; rami narrowing slightly distally, outer ramus subequal in length to inner ramus, with five robust setae on inner margin, seven robust setae on outer margin and five apical robust setae; inner ramus with four robust setae on inner margin, five robust setae on outer margin, five apical setae and one small seta placed proximally on ventral margin. Uropod 2 ( Fig. 8F ): peduncle 1.3× length of rami, with two inner/outer robust setae; rami not narrowing distally, outer ramus subequal in length to inner ramus, with four robust setae on inner margin, one robust seta on outer margin and three apical robust setae; inner ramus with five inner/outer robust setae, three apical robust setae and one small seta placed proximally on ventral margin. Uropod 3 ( Fig. 8G ): small, 90% length of telson, uniramous; peduncle 2× the length of ramus, with two apical robust setae, apical corner of peduncle produced with shallow serrations on surface; ramus with two marginal robust setae and two apical setae. Telson ( Fig. 8H ): quadrate, 1.3× longer than broad, lobes fused, cleft ~50% of length, apices armed with eight or nine large robust setae, Gnathopods: Gnathopod 1 ( Fig. 9A ): coxal plate with eight apical setae and sparse amounts of short facial setae; basis with numerous anterior and posterior setae, along with two shorter posterodistal setae, and small patches of pubescence are present on posterodistal corner; ischium with eight setae and pubescence along the posterior margin; merus with pubescence covering posterior surface and 13 plumose posterodistal setae; carpus 42% length of propodus, with two anterior setae, ten posterior setae and five medial setae; propodus 1.7× longer than broad, with five superior medial setae, five inferior medial setae and seven posterior setae, anterodistal margin of propodus ending with small spine-like projection covered by tuft of setae; palm distinctly convex, with seven inner robust setae and eight outer robust setae; defining angle armed with four inner and five outer robust setae; dactylus inner margin with six dentations, outer margin with three setae. Gnathopod 2 ( Fig. 9B ): coxal plate with eight apical setae and sparse amounts of short facial setae; basis with numerous anterior and posterior setae, along with two shorter posterodistal setae, a small patch of pubescence present on posterodistal corner; ischium with four setae and pubescence along the posterior margin; merus with pubescence covering posterior surface and eight plumose posterodistal setae; carpus 70% length of propodus, with two anterior setae, five groups of posterior setae and three medial setae; propodus 1.7× longer than broad, with two anterior setae, five superior medial setae (distal-most paired), five inferior medial setae and six groups of posterior setae, anterodistal margin of propodus ending with small spine-like projection covered by tuft of setae; palm distinctly convex, with eight inner robust setae and 11 outer robust setae; defining angle armed with one inner seta and two outer robust setae; dactylus inner margin with six dentations, outer margin with two setae.

Brood plates: ( Fig. 9B ): large, setaceous brood plates present on somites 2–5, decreasing in size posteriorly.

Urosome: Bare dorsally, segments 1–3 fused. Uropod 1 ( Fig. 10A ): peduncle 1.4× length of rami, with four inner robust setae and six outer robust setae; rami narrowing slightly distally, outer ramus 95% length of inner ramus, with six robust setae on inner margin, four robust setae on outer margin and four apical robust setae; inner ramus with five robust setae on inner margin, four robust setae on outer margin and four apical setae. Uropod 2 ( Fig. 10B ): peduncle subequal in length to rami, with three inner and one outer robust seta(e); rami narrowing slightly distally, outer ramus 75% length of inner ramus, with three outer robust setae (inner robust setae lacking) and four apical robust setae; inner ramus with four inner/outer robust setae and four apical robust setae. Uropod 3 ( Fig. 10C ): small, 95% length of telson, uniramous; peduncle 2× the length of ramus, with two apical robust setae; ramus with two marginal robust setae and two apical setae. Telson ( Fig. 10D ): quadrate, 1.5× longer than broad, lobes fused, cleft ~40% of length, apices armed with nine or ten large robust setae, two plumose setae arise dorsolaterally from outer margins of both lobes.

Variation

Individuals examined were shown to vary in several morphological characteristics ( Table 2 ).

Distribution and ecology

Sicifera cahawba is currently known only from its type locality in the Old Cahawba Prairie in Dallas County, AL, USA. Specimens were collected from the 1217 ha (3007 acre) Old Cahawba Forever Wild Tract (OCFWT). This area is managed by the Alabama Department of Conservation and Natural Resources (AL-DCNR). The unnamed watercourse where specimens were collected is a first-order stream that drains Blackland Prairie remnants and mixed hardwood forest, emptying into the Cahaba River. During the seasonally heavy rains of winter, sheet flow across the soil surface is common. The watercourse is essentially permanent, with deeper pockets and pools holding water even in the driest months (J.D.D., pers. obs.).

KEY TO SPECIES OF ‘SYNURELLIDS’ ( EOSYNURELLA / SICIFERA ) IN THE NEARCTIC

[Modified from Holsinger (1972, 1977)]

1a. Dactyli of pereopods 3–7 with two to five setae on inner margin(s), male telson> 50% cleft-to-base. Juveniles with spine-like projections on anterodistal corners of gnathopod propodi, which decrease in size until maturity .......................................................................................................................… 2. Sicifera 1b. Dactyli of pereopods 3–7 with one or two inner marginal setae, male telson <50% cleft-to-base. Lacking spine-like projections on anterodistal corners of gnathopod propodi … Eosynurella johanseni (Alaska) 2a. Uronites not fused (free) …............................... Sicifera chamberlaini (Atlantic Coastal Plain of the USA) 2b. Uronites fused …............................................................................................................................................. 3 3a. Palmar margins of gnathopod propodi straight to weakly convex; male telson apices distinctly bifurcate, cleft width-to-depth ratio of 1.6; inner margin of female gnathopod dactyli lacking teeth … Sicifera bifurca (Mississippi Embayment and surrounding regions)

3b. Palmar margins of gnathopod propodi distinctly concave; male telson apices weakly bifurcate, cleft widthto-depth ratio of three to four; inner margins of female gnathopod dactyli dentate ..............................… 4 4a. Mature males larger than mature females; gnathopods subquadrate, 1.3× longer than tall; female gnathopod bases similar in setation to those of males; telson of female 60% cleft; gnathopods 1 and 2, propodi with triply/doubly inserted superior medial setae; maxilla 1, inner plate with 12 plumose setae …...................................................................................... Sicifera dentata (Ohio River Basin) 4b. Mature females larger than mature males; gnathopods rectangular, 1.5–1.7× longer than tall; female gnathopod bases with numerous setae; telson of female 40% cleft; gnathopods 1 and 2, propodi with singly/doubly inserted superior medial setae; maxilla 1, inner plate with eight plumose setae ..................................................… Sicifera cahawba (Old Cahawba Prairie, Dallas County, AL, USA)

Figures

Figure 3. Habitus photographs of Sicifera cahawba. A, holotype, male (USNM 1660542), 6.38 mm, Old Cahawba Prairie, Dallas County, AL, USA. B, allotype, female (USNM 1660543), 8.27 mm, Old Cahawba Prairie, Dallas County, AL, USA. Scale bar: 1 mm.

Figure 4. Sicifera cahawba; holotype male, Old Cahawba Prairie, Dallas County,Alabama (USNM 1660542), 6.38 mm. A, antenna 1 (single aesthetasc enlarged). B, antenna 2 (single calceolus enlarged). C, left mandible (lacinia mobilis enlarged). D, right mandible (palp omitted, lacinia mobilis enlarged). Scale bars: 1 mm in A, B; 0.5 mm in C, D.

Figure 5. Sicifera cahawba; holotype male, Old Cahawba Prairie, Dallas County, AL, USA (USNM 1660542), 6.38 mm. A, upper lip. B, lower lip. C, maxilla 1 (outer plate spine teeth enlarged). D, maxilla 2. E, maxilliped (apical margin of inner plate enlarged). Scale bars: 0.5 mm.

Figure 6. Sicifera cahawba; holotype male, Old Cahawba Prairie, Dallas County, AL (USNM 1660542), 6.38 mm. A, gnathopod 1 (palmar margin and dactylus enlarged). B, gnathopod 2 (palmar margin and dactylus enlarged). Scale bar: 1 mm.

Figure 7. Sicifera cahawba; holotype male, Old Cahawba Prairie, Dallas County, AL, USA (USNM 1660542), 6.38 mm. A, pereopod 3. B, pereopod 4. C, pereopod 5. D, pereopod 6. E, pereopod 7. Scale bar: 1 mm.

Figure 8. Sicifera cahawba; holotype male, Old Cahawba Prairie, Dallas County, AL, USA (USNM 1660542), 6.38 mm. A, pleopod 1 (coupling spines and clothes-pin setae enlarged). B, pleopod 2 coupling spines. C, pleopod 3 coupling spines. D, epimera. E, uropod 1. F, uropod 2. G, uropod 3. H, telson. Scale bars: 1 mm.

Figure 9. Sicifera cahawba; allotype female, Old Cahawba Prairie, DallasCounty,AL, USA (USNM 1660543), 8.27 mm. The arrows in this figure associate the enlargement of the palmar margin/dactylus with the respective gnathopod. A, gnathopod 1 (palmar margin and dactylus enlarged). B, gnathopod 2 (palmar margin and dactylus enlarged). Scale bar: 1 mm.

Figure 10. Sicifera cahawba; allotype female, Old Cahawba Prairie, Dallas County, AL, USA (USNM 1660543), 8.27 mm. A, uropod 1. B, uropod 2. C, uropod 3. D, telson. Scale bars: 1 mm.

Tables

Table 2. Notable morphological variation observed among individuals of Sicifera cahawba

Character	Variability (%)
Ratio of antenna 1 to body length	55–58
♀ Antenna 1 flagellar segments	22–24
♀ Antenna 2 flagellar segments	7–8
Maxilla 1 inner plate facial setae	7–8
Maxilla 2 inner plate facial setae	8–9
Epimeron 2/3 ventral robust setae	2–3
♀ Telson cleft	38–42