Digenea arenahauriens C.W. Schneid., Hamzeh et G.W. Saunders, 2018

Schneider, Craig W., Hamzeh, Bilal F., Lane, Christopher E. & Saunders, Gary W., 2018, A new species of Digenea (Rhodomelaceae, Ceramiales) based upon a molecular assessment and morphological observations of plants historically known as D. simplex in Bermuda, Phytotaxa 338 (1), pp. 90-98 : 93-95

Digenea arenahauriens C.W. Schneid., Hamzeh et G.W. Saunders , sp. nov.

Figures 2–8

Description: Plants rigid, cartilaginous, to 7.3 cm high, light to dark purplish- to reddish-brown ( Fig. 2 ) arising from rhizoidal filaments coalesced into thick, pad-like holdfasts; erect indeterminate axes terete, dichotomously to irregularly branched, polysiphonous, axial rows surrounded by (8–) 9–12 pericentral cells (only seen below apices), heavily corticated and 0.9–4.1 mm diam. below the apices ( Fig. 3 ); indeterminate branches 0.7–3.1 mm diam.; indeterminate axes covered densely with thin, wiry determinate branches to 7.7 mm in length and 120–270 μm diam., lower axes often less densely covered ( Fig. 2 ), determinate branches deciduous, abraded or grazed, with regrowth of shorter determinate branches than the longer ones distally; determinate branches polysiphonous, with axial cells, 27–78 μm diam, surrounded by (8–) 9–12 pericentral cells, 14.4–38.4 (–44.0) μm diam., these in turn surrounded by 17–34 cylindrical outer cortical cells, 9.6–38.0 μm diam. ( Fig. 4 ); determinate branches composed of 44–60 axial segments 110–170 μm long in median portions, with lengths defined by the single axial cell of each segment ( Fig. 5 ); outer cortical cells of determinate branches angular, lenticular to irregular in surface view forming in discrete packets over pericentral cells ( Fig. 5 ); apices with short vegetative trichoblasts remaining during development ( Figs 6, 7 ); tetrahedral sporangia ellipsoidal to globose, 38–82 μm diam., swelling determinate branches subapically when forming ( Fig. 6 ), plants presumably dioecious, cystocarps urceolate ( Fig. 8 ), 390–500 μm diam., formed laterally and subapically on determinate branches, one or more per branch ( Fig. 8 ); spermatangia unknown.

Diagnosis: Differing from the morphologically cryptic Digenea simplex by its production of a greater number of axial segments in determinate branches, and greater numbers of pericentral and cortical cells with larger diameters in these branches. The new species is easily distinguished from D. cymatophila by its upright habit, and the much smaller D. subarticulata by its size.

Type locality: Bermuda, northwestern Atlantic Ocean, Captain Williams’ Bay, south shore of Bermuda I.

Holotype (designated here): BERMUDA – Thea R. Popolizio (TRP) / Craig W. Schneider ( CWS) 12-171-1 [ BDA1808 ], 10 Dec. 2012, Capt. Williams’ Bay, south shore Bermuda I., 32°18’08.2”N, 64°44’18.1”W, intertidal rock and tide pools [deposited in MICH] ( Fig. 2 ); isotypes NY, US, UNB, Bermuda Natural History Museum, Herb. CWS [ BDA1808 b, GenBank MG648071 ].

Selected collections (genetic isolates listed in Table 1): BERMUDA — Harris’ Bay, Bermuda I., 23 April 1913, A. B. Hervey [ P. B.- A. 1939, Collins et al. 1913, as D. simplex ] ; West Whale Bay, Bermuda I., 32°15.3’N, 64°48.6’W, on int. rock, 1 April 2003, CWS / Christopher E. Lane ( CWS / CEL) 03-21-3 ; Capt. Williams’ Bay, south shore Bermuda I., loc. cit., int. rock/tide pools, 20 February 2008, CWS / CEL 08-44- 2 ; Capt. Williams’ Bay , loc. cit., 23 August 2010, CWS / CEL 10-22- 9 [ BDA0344 , 0345 ] ; Spanish Point Park, north shore Bermuda I., 32˚18’26.4” N, 64˚48’56.6” W, 0–2 m, 25 August 2010, CWS 10-33 - 14 [ BDA0503 ] ; Capt. Williams’ Bay , loc. cit., 15 January 2012, CWS / CEL 12- 2- 3 [ BDA0522 ] ; West Whale Bay, Southampton, Bermuda I., 32˚15’19.0” N, 64˚52’23.4” W, int. rock/boilers, 2–3 m, 20 January 2012, CWS / CEL / TRP 12-21- 18 [ BDA0712 , 0713 ] ; Ariel Sands, Cox’s Bay, south shore Bermuda I., 32˚17’45.5” N, 64˚44’50.0” W, int. rocks/pools, 31 January 2012, TRP/ CWS 12-27- 5 [ BDA0765 ] ; Grape Bay Beach, Paget, south shore Bermuda I., 32˚17’03.6” N, 64˚45’52.6” W, int. rocks/pools, 7 February 2012, TRP/ CWS 12-30- 18 [ BDA0827 ] ; Grape Bay , loc. cit., 18 June 2012, TRP/ CWS 12-77- 2 [ BDA1198 ] ; Rocky Bay, Devonshire Bay Park, south shore Bermuda I., 32˚17’53.2” N, 64˚44’40.8” W, int. rock, 20 August 2012, CWS / CEL / TRP 12-95- 2 [ BDA 1340 ] ; Grape Bay , loc. cit., 20 August 2012, CWS / CEL / TRP 12-96- 8 . LESSER ANTILLES– Sint Eustatius, Blue Bead Hole II, 16–18 m, 25 Jun. 2015, EUX 37.01 [ L 3960311 ] .

Geographic Distribution: Presently known only from Bermuda and Sint Eustatius, Dutch West Indies, Lesser Antilles, Caribbean Sea.

Etymology: The Latin participle arenahauriens is used for the epithet meaning “sand-drawing, drinking, sucking in” for this species’ habit of knocking down suspended sand and creating a sediment underneath a colony.

Figures

FIGURES 2–8. Digenea arenahauriens sp. nov. 2. Holotype specimen [TRP/CWS 12-171-1]. Scale bar = 2 cm. 3. Indeterminate axis below the apex in transverse section with radiating determinate branches [CWS/CEL 03-21-3]. Scale bar = 500 μm. 4. Transverse section of determinate branch with pericentral cell layer around axial cell and single outer cortical layer [CWS/CEL 10-22-9]. Scale bar = 50 μm. 5. Surface view of determinate branch showing discrete packets of cortical cells covering pericentral cells [CWS/CEL/TRP 12-21-18]. Scale bar = 100 μm. 6. Determinate branch apex with subapical tetrahedral sporangia [CWS/CEL/TRP 12-96-8]. Scale bar = 50 μm. 7. Determinate branch apex with incurved trichoblasts overtopping axial row [TRP/CWS 12-171-1]. Scale bar = 50 μm. 8. Paired cystocarps produced subapically on determinate branch [CWS/CEL/TRP 12-96-8]. Scale bar = 150 μm.