Ceratopera cascadiensis, Van Steenkiste & Leander, 2018

CERATOPERA CASCADIENSIS View in CoL SP. NOV.

( FIG. 3)

Etymology: The species epithet refers to Cascadia, the Pacific Northwest of North America.

Type locality: Clover Point , Victoria, British Columbia, Canada (48°24 ′ 12 ″ N, 123°21 ′ 03 ″ W), algae in rocky lower intertidal (16/03/2015) GoogleMaps .

Type material: One whole mount which is designated as the holotype ( SMNH Type-8919) .

Other material: Observations on a live animal.

Diagnosis: Species of Ceratopera with a 158- μ m-long stylet. Stylet composed of a stylet proper that makes a 90° proximal turn, and a mantle consisting of a proximal girdle bearing two 100- μ m-long, plate-like tubes with pointed tips. Distal end of the stylet proper pointed. Plate-like tubes provided with a ridge of which at least one has a combed edge. Bursal appendage 91 μ m long, with broad base and spirally curled funnel that distally splits into two short insemination tubes.

Description: Animal 1.2 mm long with eyes and some parenchymatous brownish coloration ( Fig. 3A). General appearance much plumper than the more typical fusiform C. axi found at the same locality ( Figs 3A, 4A). Pharynx slightly anterior to the midpoint of the body. Epidermis packed with oblong rhabdites. Rhabdite tracks present in the anterior body half.

Internal organization identical to C. axi with paired testes posterior to the pharynx, paired seminal vesicles entering the prostate vesicle, an elongated bursa with a sclerotized bursal appendage, paired ovaries and vitellaria.

The sclerotized parts of the male copulatory organ measure 158 μ m (non-axial: 117 μ m) and consist of (1) a 158- μ m-long stylet proper that is proximally curved over 90° and distally straight with a pointed tip; and (2) a mantle modified into a proximal girdle that modifies into two 100- μ m-long, plate-like tubes with pointed tips ( Fig. 3B, C). The girdle connects to and surrounds the proximal curved part of the stylet. The distal tubes run adjacent to the stylet and bear a ridge of which at least one has a combed edge (arrow in Fig. 3B, C).

The bursal appendage is typical of Ceratopera and consists of a broad, striated proximal base and a spirally curled, more sclerotized funnel that distally splits into two short insemination tubes ( Fig. 3D, E). The spiral length of the bursal appendage measures 91 μ m.

Discussion: This species closely resembles representatives of Ceratopera sensu Den Hartog because of the typical construction of the stylet with a mantle surrounding the stylet proximally and the funnel-shaped bursal appendage. Ceratopera sensu Den Hartog encompassed 11 recognized species, which are discussed in Den Hartog (1964), Ehlers & Ax (1974) and Karling (1986) (but see also the discussion on C. complicata sp. nov. and the general discussion). The mantle associated with the stylet is modified into two structures in only three species of this group: C. sellai (Steinböck, 1933) Den Hartog, 1964 , C. levinseni Den Hartog, 1964 and C.reisingeri (Riedl, 1959) Den Hartog, 1964 . In the first two species, these modifications consist of elongated plates (‘lamellae’ in Den Hartog, 1964) proximally originating on a girdle surrounding the stylet, while in the latter species a girdle is absent. The stylet of C. cascadiensis sp. nov. mostly resembles the one of C. sellai as one plate is also tubular and runs closely adjacent to the stylet. However, the other plate in C. sellai is curved and distally modified into a sheet ( Den Hartog, 1964), thus differing from the situation in C. cascadiensis sp. nov.

Ax (1995) reports on a Greenlandic specimen of Ceratopera he provisionally attributes to C. cfr. levinseni . The elongated stylet of the live specimen he observed ( Ax, 1995: figs 14D, 16) shows a general resemblance to the stylet of C. cascadiensis sp. nov. Although Ax (1995) did not notice any division of the mantle into two ‘lamellae’, two elongated plates or tubes seem to be present ( Ax, 1995: fig. 16B). Unfortunately, no further details on the morphology of the mantle or the bursal appendage of the Greenlandic specimen are available. As such, this individual remains without a formal species designation.

Ceratopera cascadiensis View in CoL sp. nov. further differs from all other species of Ceratopera sensu Den Hartog View in CoL by the presence of a combed edge on at least one of its mantle tubes. In all other species the edges of the mantle plates or tubes are smooth. With four species of Ceratopera View in CoL known from the Northeast Pacific Ocean ( C. axi View in CoL , C. pacifica View in CoL comb. nov., C. ehlersi Karling, 1986 View in CoL , and C. pilifera View in CoL ), C. cascadiensis View in CoL sp. nov. is the fifth species described from this region.