Research Article |
Elizabeth L. Durham‡, Kristine N. White‡
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Corresponding author: Kristine N. White ( white.kristinen@gmail.com ) Academic editor: Alan Myers
© 2023 Elizabeth L. Durham, Kristine N. White.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Durham EL, White KN (2023) Caribbean Amphipoda (Crustacea) of Panama. Part I: parvorder Oedicerotidira. ZooKeys 1159: 37-50. https://doi.org/10.3897/zookeys.1159.102034
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Abstract
Amphipods in the parvorder Oedicerotidira are burrowers, furrowers, or surface skimmers. Members of the parvorder share a well-developed posteroventral lobe on coxa 4, an equilobate coxa 5, an immensely elongate pereopod 7 that differs in structure from pereopod 6, and an entire telson. Within the parvorder, only the family Oedicerotidae has been documented from Bocas del Toro, Panama, represented by two species. This research documents a range extension for Hartmanodes nyei (Shoemaker, 1933) and describes a new species of Synchelidium Sars, 1892. An identification key to the species of Caribbean Oedicerotidae of Panama is provided.
Keywords
Bocas del Toro, Caribbean, Hartmanodes nyei, identification key, new species, Oedicerotidae, Panama, Synchelidium purpurivitellum sp. nov.
Introduction
Parvorder Oedicerotidira Lilljeborg, 1865 (
Defining characteristics of amphipods in the family Oedicerotidae include having a well-developed antenna 2, reaching at least half the length of antenna 1; a strong down-curved rostrum; well-developed dorsolateral eyes; coxae 1–3 well-developed, each longer than the previous coxa; a subchelate gnathopod 1; article 3 of gnathopod 2 less than 2 × as long as wide; and a distally attenuate pereopod 7 that is longer and more slender than pereopod 6. Amphipods in the family Oedicerotidae differ from those in the families Exoedicerotidae and Paracalliopidae in having separate urosomite segments and lacking the oblique setal row on the maxilla 2 inner plate (
Two species of oedicerotid amphipods were collected from Bocas del Toro, Panama, one of which is new to science. Both species are diagnosed and the new species is described herein, and an identification key is provided to distinguish between the three species known from the Caribbean waters of Panama.
Materials and methods
Amphipods were collected by hand using a Ziploc bag to scoop up fine sand from Crawl Cay, Bocas del Toro, Panama at depths of 1.5–5.0 m. The sand was elutriated with freshwater to remove amphipods. Live specimens were sorted to morphospecies, placed in clove oil for imaging, and preserved in 99.5% EtOH for later examination. Preserved specimens were transferred to glycerol, measured from the tip of the rostrum to the base of the telson, and dissected under a stereomicroscope. Specimens were illustrated using a Meiji MT5900L phase contrast microscope with an Olympus U-DA drawing tube attached. Illustrations were digitally inked following
Results
Descriptions
Parvorder Oedicerotidira Lilljeborg, 1865 (Lilljeborg, 1865b)
Superfamily Oedicerotoidea Lilljeborg, 1865 (Lilljeborg, 1865a)
Family Oedicerotidae Lilljeborg, 1865 (Lilljeborg, 1865b)
Hartmanodes
Generic diagnosis
Antenna 1 shorter than antenna 2; male antenna 2 much longer than that of female; head, rostrum large, apex deflexed. Gnathopods 1 and 2 not sexually dimorphic; gnathopod 1 carpus broad, propodus long, ovate; Gnathopod 2 subchelate, carpus narrow, propodus elongate, narrowing distally. Pereopod 5 coxa large, deep, equilobate. Pereopod 7 basis with small posterodistal lobe. Telson short, apex truncate or emarginate.
Hartmanodes nyei
Monoculodes nyei Shoemaker, 1933: 9, fig. 5.
Hartmanodes nyei:
Material examined
Panama • 1 ♀, 4.0 mm; Bocas del Toro, Crawl Cay; 9.2475°N, 82.1290°W; depth 5 m, in sand; 12 Aug 2021; K.N. White leg;
Diagnosis
Antenna 1 of female subequal to peduncle of antenna 2; antenna 2 of male much longer than that of female; head, anterodorsal angle broadly subquadrate. Pereopods 3 and 4 propodus subrectangular, dactylus elongate, slender; pereopods 5 and 6 dactylus elongate, subequal to propodus in length; pereopod 7 basis posterior margin with several short setae, carpus and propodus, posterior margin with several spine groups, dactylus elongate, slender.
Distribution
U.S.A.: Gulf of Mexico (
Ecology
These amphipods burrow into sand in shallow subtidal habitats.
Synchelidium
Generic diagnosis
Antenna 1 shorter than antenna 2; male antenna 2 much longer than that of female; head, rostrum strong, distally deflexed. Gnathopods 1 and 2 not sexually dimorphic; gnathopod 1 carpus elongate, slender, propodus broad; Gnathopod 2 chelate, carpal lobe slender, propodus elongate. Pereopod 5 coxa medium, deep, equilobate. Pereopod 7 basis lacking or with weak posterior lobe. Telson short, apex emarginate or rounded.
Synchelidium purpurivitellum sp. nov.
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;
Paratypes
: Panama • 1 ♂, 2.0 mm; same station data as for preceding;
Other material
: Panama • 2 ♀, 1 ♂, 3 juvenile, same station data as for preceding;
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.
Identification Key to the Caribbean Oedicerotae of Panama
| 1 | Gnathopod 1, carpal lobe slender; gnathopod 2 chelate; pereopods 3 and 4, dactylus short | Synchelidium purpurivitellum sp. nov |
| – | Gnathopod 1, carpal lobe broad; gnathopod 2 subchelate; pereopods 3 and 4, dactylus long | 2 |
| 2 | Eye well-developed; pereopods 3 and 4, carpus subquadrate, not produced, subequal in width to propodus; pereopod 7, basis without facial setae; telson apically truncate | Hartmanodes nyei |
| – | Eye absent; pereopods 3 and 4, carpus posteroventrally produced, 3 × as wide as propodus; pereopod 7, basis with facial setae; telson apically convex | Aceroides (Patoides) synparis |
Discussion
The results of this study increase the number of Caribbean oedicerotid amphipods known from Panama to three, with the documentation of a new species and a range extension to include Panama for H. nyei. Hartmanodes nyei has previously been reported from the western Atlantic Ocean, including the Caribbean Sea (
The genus Synchelidium now contains eight species worldwide, with Synchelidium purpurivitellum sp. nov. being the first Caribbean species of the genus. Americhelidium americanum was reported from the Caribbean as Synchelidium americanum before the closely related genus Americhelidium Bousfield & Chevrier, 1996 was erected (
Funding
Funding for this study was provided by a National Science Foundation grant: Collaborative Research: ARTS: Understanding Tropical Invertebrate Diversity Through Integrative Revisionary Systematics and Training (1856421). Publication costs were provided by the Georgia College & State University GC Journeys Program.
Acknowledgements
Logistical support and facilities were provided by Georgia College & State University Department of Biological and Environmental Sciences and the Smithsonian Tropical Research Institute (STRI). Special thanks to Carolina Cesar for assistance with diving and collecting in Bocas del Toro. Comments and suggestions from Sara LeCroy and Azman Abdul Rahim greatly improved the manuscript.
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Supplementary material
Collection data for Caribbean Oedicerotidira of Panama
Data type: COL (.xlsx file)