Paracentrophyes

Sørensen, Martin V. & Landers, Stephen C., 2017, Description of a new kinorhynch species, Paracentrophyes sanchezae n. sp. (Kinorhyncha: Allomalorhagida) from the Gulf of Mexico, with differential notes on one additional, yet undescribed species of the genus, Zootaxa 4242 (1), pp. 61-76 : 72-74

Paracentrophyes sp.

( Figs 7–8 )

Besides P. sanchezae n. sp., samples from the Gulf of Mexico revealed four female specimens of one additional, yet undescribed species of Paracentrophyes . Three specimens were mounted for SEM, whereas the last one, which unfortunately was not in a good condition, was mounted for LM ( Fig. 7 ). Due to the restricted amount of material, especially for LM, we chose not to make a formal description of the species. We will, however, provide a short diagnostic account, which hopefully will enable researchers to recognize the species if additional specimens are collected in the future.

Material. One female specimen, adult or late juvenile stage, collected from mud on November 5, 2009, at station 099-2009 ( Fig. 1 ), at 129 m depth on the Florida Shelf, about 136 km south of Cape San Blas , Florida (position: 28o26’30’’N 085o11’27’’W) mounted in Fluoromount G, deposited at the Natural History Museum of Denmark, under catalogue number ZMUC KIN- 1016 . In addition, three female specimens, mounted for SEM and stored in the authors’ personal collections. The first specimen was collected on November 1, 2007, at station 094- 2007 ( Fig. 1 ), at 113 m depth about 125 km southeast of Pensacola, FL, (position: 29o33’56’’N 086o17’34’’W), whereas the two other specimens were collected on November 15, 2013, at station 78-2013 ( Fig. 1 ), at 142 m depth in the innermost extension of the submarine De Soto Canyon, 70 km southeast of Pensacola, Florida (position: 29o53’08’’N 086o47’31’’W) .

Diagnostic account. Head and mouth cone structures could not be studied in detail. It is however clear that outer oral styles alternate in size between larger and smaller ones. Segment 1 consists of a tergal and a sternal plate; sternal plate partly differentiated in epi- and midsternal plates ( Fig. 7 B). Segments 2 to 11 consist of one tergal and two sternal plates ( Figs 7 A, D, 8A). Trunk length = 600 µm. Segment 1 almost smooth near anterior margin, and without reticulated areas ( Figs. 7 B, 8B). Middorsal spinose processes are present on segments 1 to 9, and midlateral processes on segments 1 to 10. Segments 10 and 11 with middorsal spines, and segment 11 with lateral terminal spines ( Figs. 7 C–D, 8F, H). Spines are generally very short, i.e., middorsal spine segment 10 = 17 µm (MDS10/TL ratio 2,8%), middorsal spine segment 11 = 24 µm (MDS11/TL ratio 4,0%) and lateral terminal spines = 30 µm (LTS ratio 5,0%). Perispinal setae are found on a few segments only: ventrolateral positions on segment 1; unpaired paradorsal and paired ventrolateral on segment 5 ( Fig. 8 C); unpaired paradorsal on segment 7 ( Fig. 8 D); paired paralateral on segment 8 ( Fig. 8 D); unpaired paradorsal and paired ventrolateral on segment 9 ( Fig. 8 D). One specimen mounted for SEM carried several unidentified loricate, epibionts ( Fig. 8 C, F–G).

Remarks on diagnostic characters. The species is easily recognized by its very low number of perispinal setae, and by its very short spines. The middorsal processes/spines of segments 10 and 11 in female specimens of Paracentrophyes are usually short, but still, they are even shorter in Paracentrophyes sp. from the Gulf of Mexico ( Figs 7 A, C–D, 8A, F, H). The difference in dimensions gets most conspicuous in the lateral terminal spines though, where the LTS/TL ratios for P. quadridentatus , P. praedictus and P. sanchezae n. sp. are around 25–27%. In P. anurus the ratio is considerably smaller, i.e., 9.7%, but in Paracentrophyes sp. from the Gulf of Mexico we find even shorter lateral terminal spines, with an LTS/TL ratio of only 5.0%. Hence, this yet undescribed species is currently the Paracentrophyes with the shortest terminal spines.

Also the distribution of perispinal setae, and in particular the general scarcity of them, makes it easy to recognize the species. As noted above under diagnostic traits for P. sanchezae n. sp., the other three species of the genus are generally rich in setae, with continuous series of paired setae in paradorsal, paralateral and ventromedial positions from segment 1 to segment 9 or 10. The number of setae in P. sanchezae n. sp. is considerably lower, but Paracentrophyes sp. from the Gulf of Mexico has even fewer setae, and differs from P. sanchezae n. sp. by lacking perispinal setae in paralateral positions on segments 6 and 7, and in ventrolateral positions on segments 3 and 10. Based on these traits, we believe it would be easy to recognize the new species in future samples.

Figures

FIGURE 1. Map showing the collection sites for Paracentrophyes spp. in the Gulf of Mexico.

FIGURE 7. Light micrographs showing overviews and details trunk morphology of the only specimen of Paracentrophyes sp. available for LM, female. A. Ventrolateral overview. B. Segment 1, ventrolateral view. C. Segments 10 and 11, focused on middorsal spines (right) and one lateral terminal spine (left). D. Segments 10 and 11, focused on other lateral terminal spine and sternal plates. Abbreviations: isf, incomplete sternal fissures; lts, lateral terminal spine; mds 10 – 11, middorsal spine followed by segment number; vm 3, ventromedial sensory spot type 3.

FIGURE 8. Scanning electron micrographs showing overviews and details in head and trunk morphology of female Paracentrophyes sp. A. Lateroventral overview. B. Anterior part of segment 1, lateral view. C. Segments 4 and 5, lateral view. D. Segments 5 to 7, lateral view. E. Segments 7 to 9, ventrolateral view. F. Segments 10 to 11 with attached epibionts, ventrolateral view. G. Segments 4 to 8 with attached epibionts, lateroventral view. H. Segments 9 to 11, lateroventral view. Abbreviations: lts, lateral terminal spine; mds 10 – 11, middorsal spine followed by segment number; pds, paradorsal seta; pls, paralateral seta; vls, ventrolateral seta.