Crangonyx ephemerus Cannizzaro and Sawicki, 2019

Cannizzaro, Andrew G. & Sawicki, Thomas R., 2019, Two new species of the genus Crangonyx Bate, 1859 (Amphipoda: Crangonyctidae) from the St. Marks River Basin with notes on the “ Crangonyx floridanus complex ”, Zootaxa 4691 (4), pp. 301-332 : 305-316

publication ID	https://doi.org/ 10.11646/zootaxa.4691.4.1
publication LSID	lsid:zoobank.org:pub:2B6EC2BC-4500-4D9B-8EFB-639013CEC4D2
persistent identifier	https://treatment.plazi.org/id/67B5D2EB-42D6-4D0D-A3B4-8557085A9DF7
taxon LSID	lsid:zoobank.org:act:67B5D2EB-42D6-4D0D-A3B4-8557085A9DF7
treatment provided by	Plazi
scientific name	Crangonyx ephemerus Cannizzaro and Sawicki
status	sp. nov.

Treatment

Crangonyx ephemerus Cannizzaro and Sawicki View in CoL n. sp.

( Figs 3 – 9 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 )

Type material. Holotype, female 6.21 mm: St. Marks Headwaters Greenway, Leon County, Florida; Collector: Andrew G. Cannizzaro, 16 March 2018; Florida Museum of Natural History ; catalog number: UFID 52586 . Allotype, male 3.85 mm: St. Marks Headwaters Greenway , Leon County, Florida; Collector: Andrew G. Cannizzaro, 16 March 2018; catalog number UFID 52587 . Paratype, female 5.83 mm: St. Marks Headwaters Greenway , Leon County, Florida; Collector: Andrew G. Cannizzaro, 16 March 2018; catalog number UFID 52588 . Paratype, female 5.88 mm: St. Marks Headwaters Greenway , Leon County, Florida; Collector: Andrew G. Cannizzaro, 16 March 2018; catalog number UFID 52589 . Paratype, female 7.11 mm: St. Marks Headwaters Greenway, Leon County, Florida; Collector: Andrew G. Cannizzaro, 16 March 2018; Yale Peabody Museum of Natural History ; catalog number: YPM IZ 105549 . Paratype, female 6.32 mm: St. Marks Headwaters Greenway , Leon County, Florida; Collector: Andrew G. Cannizzaro, 16 March 2018; catalog number YPM IZ 105551 . Paratype, male 4.30 mm: St. Marks Headwaters Greenway , Leon County, Florida; Collector: Andrew G. Cannizzaro, 16 March 2018; catalog number UFID 52590 . Paratype, male 3.77 mm: St. Marks Headwaters Greenway , Leon County, Florida; Collector: Andrew G. Cannizzaro, 16 March 2018; catalog number YPM IZ 105550 .

Diagnosis. Medium sized epigean species distinguished from all other members of the genus Crangonyx except C. pseudoephemerus n. sp. by the combination of the following characteristics: palmar margins of gnathopods 1 and 2 with more than 10 robust setae; pereopod 6 dactylus relatively short, ~30% length of propodus; pereopods 5–7 (especially pereopod 7) possessing numerous deep serrations on posterior margins of bases; strongly produced distoposterior corners of epimera 1–3; posterior margins of epimera 1–3 with 1 seta; ventral margin of epimeron 2 lacking paired robust setae; pleopod 1 peduncle 30–45% length of rami; inner ramus of female uropod 3 with 2 robust setae; comb-spines, but no ventral spines on the inner margin of the outer ramus of the uropod 2 of males; and male uropod 3 inner ramus armed with single robust seta. Distinguished from C. pseudoephemerus n. sp. by mandibular palp second segment twice as long as third; meri of female pereopods 6 and 7 up to 80% length of corresponding carpals with up to 4 posteromarginal robust setae; female uropod 1 peduncle with 4 to 5 inner robust setae and 3 to 4 outer robust setae; female telson 30–35% cleft; male uropod 1 peduncle with 4 inner robust setae; male uropod 2 peduncle with 3 to 4 outer robust setae, with the apical-most paired; male uropod 2 outer ramus with small comb-spines, reaching less than half the length of the margin; and male telson 38–45% cleft. Females 5.8–7.1 mm, males 3.7–4.3 mm.

Description of female. Holotype (UFID 52586) 6.21 mm in length. Eyes full, pigmented ( Fig. 2A View FIGURE 2 ); interantennal lobe narrow, with rounded and upper lower margins. Integumentary pigment bluish grey when alive.

Antennae: Antenna 1 ( Fig. 3A View FIGURE 3 ): approximately 65% body length, 2.1 times longer than antenna 2; peduncle segment 1 with 2 lateral setae and several plumose setae along the posterior margin; primary flagellum with 25 segments, aesthetascs present on distal segments, aesthetascs shorter than respective segments; accessory flagellum 2-segmented, reaching past the first segment in length. Antenna 2 ( Fig. 3B View FIGURE 3 ): gland cone distinct; peduncle 2 times longer than flagellum, with 2 robust setae placed anteriorly and laterally on segment 3 and plumose setae placed on antero/posterodistal margins of segments 4 and 5, peduncular segment 4 subequal in length to segment 5; calceoli absent on both peduncle and flagellum; flagellum 8-segmented.

Mouthparts: Mandibles ( Fig. 3C, D View FIGURE 3 ): left mandible incisor 5-dentate, lacinia mobilis 4-dentate, with 6 robust and plumose accessory setae; molar process well developed with 1 plumose seta; palp 3-segmented, second segment 2.2 times longer than third segment with 5 Alpha setae and 3 Beta setae, inner margin of segment covered in fine setae; segment 3 rounded distally with 2 C setae, 5 E-setae, 1 B-seta, and 10 plumose D-setae, A-setae lacking; face of segment covered in numerous, fine pubescent setae. Right mandible, incisor 4-dentate, lacinia mobilis bifurcate, proximal lobe with numerous fine dentations, distal lobe branched with numerous dentations; accessory setae row with 5 robust and plumose setae; molar process and palp as in left mandible. Upper Lip ( Fig. 4A View FIGURE 4 ): rounded, apical margin of labrum with numerous fine setae. Lower Lip ( Fig. 4B View FIGURE 4 ): inner lobes highly reduced, outer margin of both inner and outer lobes covered in numerous fine setae; face of lip covered in pubescence. Maxilla 1 ( Fig. 4C View FIGURE 4 ): inner plate with 6 plumose marginal setae and fine pubescence covering entire plate; outer plate with 7 apical combspines, pubescence covers entire plate, decreasing laterally; palp 2-segmented, distal segment covered in pubescence; apical margin of distal segment with 3 submarginal setae and 6 marginal robust setae. Maxilla 2 ( Fig. 4D View FIGURE 4 ): both inner and outer plates covered in pubescence; outer plate slightly shorter than inner plate, with 15 apical setae; inner plate narrowing distally, with 14 apical setae and 5 plumose facial setae. Maxilliped ( Fig. 4E View FIGURE 4 ): inner plate much shorter than outer plate, with 4 unarmed spine-teeth, 1 armed spine-tooth along apical margin and 2 plumose inner marginal setae, surface of plate covered in fine pubescence; outer plate armed with 25 setae, several of which are plumose; palp 4-segmented, second segment with 21 marginal and submarginal setae on inner margin, and 2 distal outer marginal setae, third segment with numerous distal setae, lateral surface pubescent marginally; dactylus with 1 outer seta and 2 inner setae.

Gnathopods: Gnathopod 1 ( Fig. 5A View FIGURE 5 ): coxal plate with 12 apical setae and sparse amounts of short facial setae; basis with numerous long setae inserted along anterior, posterior, lateral and medial margins, along with shorter anterodistal setae, a small patch of pubescence is present on the posterodistal corner; ischium with 7 setae and pubescence along posterior margin; merus with pubescence covering posterior surface and 16 plumose posterodistal setae; carpus 80% length of propodus, with 9 anterior setae, 2 groups of medial setae and 10 plumose posterior setae; propodus 1.7 times longer than broad with 4 marginal anterior setae, 2 superior medial setae, 4 inferior medial setae and 12 posterior setae; palm transverse with 8 rows of short robust setae and 6 long setae; defining angle armed with 3 inner and 3 outer robust setae; dactylus with 1 outer seta and 7 inner setae. Gnathopod 2 ( Fig. 5B View FIGURE 5 ): coxal plate with 9 apical setae and sparse amounts of short facial setae; basis with numerous long setae inserted along anterior and posterior margins, shorter setae arise distally from anterior margin, a small patch of pubescence is present on the posterodistal corner; ischium with 3 short seta and pubescence along posterior margin; merus with pubescence covering posterior surface and 8 distal setae; carpus 80% length of propodus with 4 anterior setae, 1 group of medial setae and 5 groups of plumose posterior setae; propodus 2.2 times longer than broad, with 1 marginal anterior seta, 6 superior medial setae, 4 inferior medial setae and 5 groups of plumose posterior setae; palm oblique with 10 outer and 7 inner robust setae and 7 long outer setae; defining angle armed with 4 inner and 2 outer robust setae; dactylus with 1 outer seta and 6 inner setae.

Pereopods: Pereopod 3 ( Fig. 5C View FIGURE 5 ): coxal plate with 12 apical setae and sparse facial setae; basis with numerous anterior and posterior setae; merus 1.4 times longer than carpus, carpus subequal to propodus in length; dactylus 42% length of propodus, with 1 plumose seta on outer margin, a stout seta on distal corner of inner margin followed by a thin seta on distolateral margin. Pereopod 4 ( Fig. 6A View FIGURE 6 ): subequal to pereopod 3 in length; coxal plate slightly longer than broad, with distinct excavation along the posteroproximal margin, armed with 14 apical setae and numerous facial setae; merus 1.2 times longer than carpus, carpus subequal to propodus in length; dactylus approximately 30% length of propodus, setation similar to pereopod 3. Pereopod 5 ( Fig. 6B View FIGURE 6 ): coxal plate large, bilobate with distinct anterior and posterior lobes, posterior lobe with 1 seta on distal corner; basis posterior margin weakly convex with 13 shallow serrations and a convex distal corner, anterior margin with 7 split-tipped robust setae, 4 distal setae and 2 proximal setae, face of segment with sparse setae; merus 68% length of carpus; carpus 1.2x longer than propodus, dactylus approximately 35% length of propodus, setation similar to other pereopods. Pereopod 6 ( Fig. 6C View FIGURE 6 ): coxal plate bilobate, with produced posterior lobe, posterior lobe bearing 1 apical seta; basis posterior margin convex with 15 shallow serrations and a straight distal corner, anterior margin with 8 split-tipped robust setae, 2 distal robust setae and 2 proximal setae, face of segment with sparse setae; merus 75% length of carpus; carpus subequal to propodus in length, dactylus approximately 30% length of propodus, setation similar to other pereopods. Pereopod 7 ( Fig. 6D View FIGURE 6 ): coxal plate lobes indistinct, with 3 posterior setae; basis posterior margin convex with 14 serrations (increasing in depth distally) and a straight distal corner, anterior margin with 7 split-tipped robust setae, 3 distal robust setae, and 2 proximal setae, face of segment with sparse setae; merus 83% length of propodus; carpus subequal to propodus in length, dactylus approximately 30% length of propodus, setation similar to other pereopods.

Gills and brood plates ( Figs. 5 View FIGURE 5 B–C, 6A–D): coxal gills present on somites 2–6, somite 7 with pereopod 7 gill, subequal in size to coxal gills. Large, setaceous brood plates present on somites 2–5, decreasing in size posteriorly. Sternal gills present on somites 6 and 8.

Pleosome: second and third segments with 1 to 2 setae arising on dorsodistal margins and shorter pubescence weakly covering dorsal surface. Pleopods ( Fig. 6 View FIGURE 6 E–G): peduncle of pleopod 1 short, 40% length of rami, lacking setae, with 2 coupling hooks and a patch of pubescence on distal corner of outer margin; outer and inner rami with 17 and 18 segments respectively; pleopod 2 peduncle lacking setae, with 2 coupling hooks and a patch of pubescence on distal corner of outer margin; outer and inner rami with 15 and 16 segments respectively; pleopod 3 peduncle lacking setae, with 2 coupling hooks and a patch of pubescence on distal corner of outer margin; outer and inner rami with 15 segments each. Epimera ( Fig. 7A View FIGURE 7 ): first epimeron ventral margin unarmed, highly oblique, distoposterior corner distinctly produced, with tooth-like extension, posterior margin with 1 seta placed proximally from distoposterior corner, face of epimeron with 2 setae; second epimeron ventral margin with 3 robust setae, distoposterior corner distinctly produced, with tooth-like extension, posterior margin with 1 seta, face of epimeron with 3 setae and several short setae; third epimeron ventral margin with 3 robust setae, distoposterior corner weakly produced, with weaker tooth-like extension, posterior margin with 1 seta placed near distoposterior corner, face of epimeron with 2 setae and several short setae.

Urosome: mostly bare, with sparse setae covering dorsal surface. Uropod 1 ( Fig. 7B View FIGURE 7 ): peduncle 1.4 times length of rami with 5 robust setae on both inner and outer margins; rami narrowing slightly distally, outer ramus subequal in length to inner ramus, with 5 robust setae on inner margin, 6 robust setae on outer margin, and 5 apical robust setae; inner ramus with 3 robust setae on inner margin, 4 robust setae on outer margin, 5 apical setae, and 1 small seta placed proximally on ventral margin. Uropod 2 ( Fig. 7C View FIGURE 7 ): peduncle subequal in length to inner ramus; with 5 robust setae on both outer and inner margins, distal-most inner robust setae inserted in a pair; rami not narrowing distally, outer ramus 80% length of inner ramus, with 3 robust setae on inner margin, 5 robust setae on outer margin and 3 apical robust setae; inner ramus with 3 robust setae on inner margin, 5 robust setae on outer margin and 5 apical robust setae. Uropod 3 ( Fig. 7D View FIGURE 7 ): peduncle 60% length of outer ramus, with 3 robust setae on outer margin, and 3 robust setae inserted distally; inner ramus reduced, scale-like with 2 marginal robust setae; outer ramus 4.5 times longer than broad, 5 times longer than inner ramus, with 3 to 4 groups of robust, split-tipped setae on outer and inner margins, apex with a slender seta paired with a short robust seta.

Telson ( Fig. 7E View FIGURE 7 ): quadrate, as broad as long, lobes fused, cleft approximately 32% of length, apices armed with 4 large robust setae and 1 plumose seta, two additional plumose setae arise dorsolaterally from outer margins of both lobes.

Description of male: Allotype (UFID 52587) 3.85 mm in length, differing from female in smaller body length; shorter antennae; presence of calceoli on the peduncle and flagellum of antenna 2; presence of more robust gna- thopods with enlarged propodi and more robust setae on the palmar margins; gnathopod 1 lacking superior medial setae; pereopods 5–7 with fewer posterior serrations on bases; uropod 1 setation; uropod 2 setation, including presence of comb-spines on inner margin of outer ramus; and uropod 3 setation. Brownish in coloration when alive. Structures not described below as in female.

Antennae: Antenna 1 (not illustrated but see Fig. 2B View FIGURE 2 ): approximately 70% body length, 2.0 times longer than antenna 2; primary flagellum with 20 segments; accessory flagellum 2-segmented, slightly longer than second flagellar segment in length. Antenna 2 ( Fig. 8A View FIGURE 8 ): gland cone distinct, peduncle 2 times longer than flagellum, segment 3 with distal robust seta, plumose setae present on anterior and posterior margins of segment 4 and on anterior margin of segment 5, segments 4 and 5 subequal in length; elongate calceoli present on both peduncle and flagellum; flagellum 5-segmented, calceoli absent on final two segments.

Gnathopods: Gnathopod 1 ( Fig. 8B View FIGURE 8 ): coxal plate with 5 apical setae and sparse amounts of short facial setae; basis with a few long setae inserted along anterior and posterior margins, a small patch of pubescence is present on the posterodistal corner along with 1 smooth seta; ischium with plumose setae and pubescence along posterior margin; merus with pubescence covering posterior surface, with 5 plumose setae and 1 smooth seta along anterior margin; carpus 45% length of propodus with 1 anterior seta, 1 group of plumose medial setae and 1 group of plumose posterior setae; propodus robust, 1.5 times longer than broad with 2 marginal anterior setae, 2 inferior medial setae and 5 plumose posterior setae (superior medial setae lacking); palm oblique with 10 inner and outer bifid robust setae and 3 long outer setae; defining angle armed with 4 inner and 3 outer robust setae; dactylus with 1 outer seta and 1 inner seta. Gnathopod 2 ( Fig. 8C View FIGURE 8 ): coxal plate with 7 apical setae and sparse amounts of short facial setae; basis with a few long setae inserted along anterior and posterior margins, and 1 posterodistal seta; ischium with 1 seta and pubescence along posterior margin; merus with pubescence covering posterior surface and 2 distal setae; carpus 50% length of propodus with 1 group of anterior setae, 1 group of medial setae, and 10 plumose posterior setae; propodus robust, 2.2 times longer than broad with 5 singly-inserted superior medial setae, 1 inferior medial seta and 3 groups of plumose posterior setae; palm oblique with 13 outer and 11 inner bifid robust setae and 3 long outer setae, defining angle armed with 2 inner robust setae and 2 large outer robust setae; dactylus with 1 outer seta and 1 inner seta.

Pereopods: Pereopod 5 ( Fig. 9A View FIGURE 9 ): basis posterior margin with 10 extremely shallow serrations. Pereopod 6 ( Fig. 9B View FIGURE 9 ): basis posterior margin with 10 shallow serrations. Pereopod 7 ( Fig. 9C View FIGURE 9 ): coxal plate lobes indistinct, with 2 apical setae; basis posterior margin with 10 deep serrations (increasing in depth distally), and a straight distal corner, anterior margin with 5 marginal split-tipped robust setae, face of segment with sparse setae.

Urosome: mostly bare, with sparse setae covering dorsal surface. Uropod 1 ( Fig. 9D View FIGURE 9 ): peduncle 1.2 times length of rami with 4 inner and 6 outer robust setae; outer ramus 90% length of inner ramus, with 2 robust setae on inner margin, 4 robust setae on outer margin and 5 apical robust setae; inner ramus with 2 inner robust setae, 3 outer robust setae, and 4 apical robust setae. Uropod 2 ( Fig. 9E View FIGURE 9 ): peduncle subequal in length to inner ramus with 3 inner and outer robust setae, distal-most inner setae inserted in a pair; outer ramus 80% length of inner ramus with 5 outer robust setae and 3 apical setae, inner margin with 9 short comb-spines which reach approximately 30% the length of the ramus; inner ramus with 4 outer and inner robust setae, apex with 4 robust setae. Uropod 3 ( Fig. 9F View FIGURE 9 ): peduncle 45% length of outer ramus, with a robust seta on outer and inner margins and 3 robust setae inserted distally; inner ramus reduced, scale-like, with a single robust seta; outer ramus elongate, 4 times longer than broad, 5 times longer than inner ramus, with 4 groups of robust, split-tipped setae on outer and inner margins, apex with a slender seta paired with a short robust seta.

Telson ( Fig. 9G View FIGURE 9 ): quadrate, as broad as long, lobes fused, cleft 38% of length, apices armed with 3 large robust setae and 1 plumose seta, two additional plumose setae arise dorsolaterally from outer margins of both lobes.

Type locality. St. Marks Headwaters Greenway (30.46089, -84.10570), Leon County, Florida, ephemeral pools forming along the edges of a cypress swamp ( Fig. 1B View FIGURE 1 ) GoogleMaps .

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

Etymology. The specific epithet ephemerus is given in reference to the species’ occurrence in temporary (ephemeral) pools.

Distribution and Ecology. Crangonyx ephemerus n. sp. is currently known only from near the headwaters of the St. Marks River in Leon County, Florida, where it has been collected from ephemeral pools at the edges of a cypress swamp ( Fig. 1 View FIGURE 1 ). In the adjacent St. Marks River proper it is either absent or rare; in repeated collections the only macro-crustaceans present were Caecidotea spp. and Procambarus spp.

During the months of March and April eight individuals of C. ephemerus n. sp. were collected, five were females and of those females four (80%) were ovigerous. These data are suggestive of a late winter or early spring breeding season. Half of the individuals collected were male. Additional collections during different times of the year will be needed to better understand potential breeding seasonality and population sex ratios.