Two new species of Schizorhynchia (Kalyptorhynchia, Rhabdocoela, Platyhelminthes) from JapanAuthorJimi, Naoto0000-0001-8586-3320Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, 429 - 63 Sugashima, Toba, Mie, 517 - 0004, Japan & Centre for Marine & Coastal Studies, Universiti Sains Malaysia, 11800 USM, Penang, MalaysiaAuthorHookabe, Natsumi0000-0002-3498-8614Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2 - 15 Natsushima-cho, Yokosuka, Kanagawa 237 - 0061, JapanAuthorImura, Satoshi0000-0002-6803-6996National Institute of Polar Research, 10 - 3, Midoricho, Tachikawa 190 - 8518, Japan & Polar Science Program, The Graduate University for Advanced Studies, SOKENDAI, Tachikawa 190 - 8518, JapanAuthorDiez, Yander L.0000-0001-8741-4799Museum of Nature Hamburg – Zoology, Leibniz Institute for the Analysis of Biodiversity Change (LIB), Martin-Luther-King-Platz 3, 20146, Hamburg, Germany & Research Group Zoology: Biodiversity and Toxicology, Centre for Environmental Sciences, Hasselt University, Universitaire Campus Gebouw D, B- 3590 Diepenbeek, BelgiumtextZoosystematics and Evolution20242024-11-15100415851598journal article10.3897/zse.100.1250425E91BC1B-10CD-4E10-8B3A-0300757562D9Proschizorhynchella quadricaudatasp. nov.Figs 2
,
3
,
4 (New Japanese name: Yotsuo-kuchibashi-mushi
)
Video material.
Video of male copulatory organ of
Proschizorynchella
quadricaudata
(
https://doi.org/10.6084/m9.figshare.25568148.v1
).
Type material.Holotype
• (
NSMT
-Pl 6475
):
adult
,
intertidal sands
,
Imaihama Beach
,
30 Nov. 2019
, collected by
NJ
and
NH
; •
one reference specimen
(
NSMT
-Pl 6476
):
intertidal sands
,
Ishibu Beach
,
30 Oct. 2019
, collected by
NJ
and
NH
; •
one reference specimen
(
NSMT
-Pl 6477
):
intertidal sands
,
Manazuru
,
29 Oct. 2019
, collected by
NJ
and
NH
; •
one reference specimen
(
NSMT
-Pl 6478
):
intertidal sands
,
Yoichi
,
15 May 2019
, collected by
NJ
and
NH
; •
additional specimen
:
intertidal sands
,
Mihama
,
29 Oct. 2019
, collected by
NJ
and
NH
; •
additional specimen
:
intertidal sands
,
Imaihama Beach
,
30 Nov. 2019
, collected by
NJ
and
NH
, used for DNA extraction
.
Description.
Body
2.2 mm
long (
1.7–2.3 mm
, n = 4),
0.4 mm
at its widest point (
0.4–0.5 mm
, n = 4). Live specimens yellowish and translucent (Fig.
2
). Two pairs of short bristles (Figs
3 A
,
4 A
: br) and two pairs of small globular papillae (Figs
3 A
,
4 A
: gp) at anterior end. Proboscis consisting of two elongated lips, 360 μm in length, 100 μm at the widest part (Figs
2 A, B
,
3 A – C
,
4 A
: pr); a row of glands with 27–37 apertures in the four studied specimens on inner side of proboscis lips (Fig.
3 A, B, C
: indicated by white arrow, Fig.
4 A
); gland apertures rectangular; glands measuring 14–16 μm long and 6–8 μm in width in the four studied specimens. Pair of black eyes situated posterior to the proboscis (Figs
2
,
4 A
). Pharynx located at midbody, 160–240 μm in length and 200–260 μm in width in the four studied specimens (Figs
2 B
,
3 G
).
Proschizorhynchella quadricaudatasp. nov.
, live specimen.
A.
Holotype (
NSMT
-Pl 6475
);
B.
Reference specimen (
NSMT
-Pl 6478
).
A.
Whole specimen, dorsal view, pharynx discharged;
B.
Whole specimen, latero-dorsal view. Scale bars: 1 mm (
A
); 0.3 mm (
B
). Abbreviations: b, bursa; c, male copulatory organ; ca, common atrium; g, glands; oss, orange spherical structure; mgd, male genital duct; ov, ovary; ph, pharynx; s, stylet; sv, seminal vesicle; t, testis; v, vitellarium.
Proschizorhynchella quadricaudatasp. nov.
, live specimen, (
A – F
) reference specimen (
NSMT
-Pl 6478
), (
G, H
) holotype (
NSMT
-Pl 6475
).
A.
Anterior end;
B.
Proboscis with glands row;
C.
DIC view of proboscis with glands row (indicated by arrow);
D.
Midbody area; adhesive papillae are indicated by dashed lines (indicated by arrow);
E.
Overview of reproductive organs;
F.
Copulatory organ and common atrium;
G.
Pharynx;
H.
Tail with four finger-like projections. Scale bars: 200 μm (
A
); 100 μm (
B
); 200 μm (
C – E
); 100 μm (
F – H
). Abbreviations: br, bristles; ca, common atrium; g, glands; gp, globular papillae; mc, muscles; mgd, male genital duct; ov, ovary; ph, pharynx; pv, prostate vesicle; s, stylet; sv, seminal vesicle; t, testis.
Proschizorhynchella quadricaudatasp. nov.
, drawing based on a reference specimen (
NSMT
-Pl 6478
).
A.
Whole body;
B.
Male copulatory organ with stylet. Scale bars: 300 μm (
A
); 100 μm (
B
). Abbreviations: b, bursa; c, cirrus; ca, common atrium; e, eye; g, glands; gb, globular papillae; mgd, male genital duct; oss, orange spherical structure; ov, ovary; ph, pharynx; pr, proboscis; pv, prostate vesicle; sd, seminal duct; st, stylet; sv, seminal vesicle; t, testis; v, vitellarium; w, whisker.
One adhesive girdle located at the level of the pharynx, composed of six adhesive papillae arranged at regular intervals (Fig.
3 D
: indicated by black arrows). Tail with four finger-like projections presents at the posterior end (Figs
3 H
,
4 B
: fp), each projection similar in size, 40–50 μm in length and 20–30 μm in width in the four studied specimens, muscles strongly developed at their middle part (Fig.
3 H
: mc).
Pair of testes, each 180 μm in diameter (Figs
2
,
4 A
), located anterior to the pharynx. Seminal ducts widen and form a pair of seminal vesicles posterior to the pharynx (Figs
3 E
,
4 A, B
: sv), each 160 μm in length (150–170 μm, n = 4) and 40 μm in width (40–60 μm, n = 4). Seminal ducts (Fig.
4 B
: sd) fuse in a single duct just before entering the male copulatory bulb. Male copulatory organ comprising a proximal prostate vesicle and a distal stylet. Prostate vesicle globular, 80 μm both in length and width (60–120 μm, n = 4) (Figs
3 E
,
4 B
), separated in two packages; necks of the extracapsular prostate glands enter the copulatory bulb proximally. Stylet enclosed by the male genital duct, cone-shaped, 100–150 μm in length and 20–30 μm in width in the four studied specimens (Fig.
4 B
: st, mgd). Male genital duct opens into the common atrium (Fig.
3 E, F
: ca), and the latter leads to the exterior through the common genital pore. Common atrium brownish pigmented due to the secretions of atrial glands.
Female genital system consisting of a vitellarium (Fig.
2 A
: v) extending between the proboscis and the posterior end of the body, a single ovary (Figs
3 E
,
4 B
: ov), and bursa located behind the common genital atrium.
Diagnosis.
Species of
Proschizorhynchella
with its tail end exhibiting four finger-like projections. Proboscis with a well-developed row of glands on each lip. Cone-shaped stylet ~ 100 μm long.
Etymology.
The specific name is derived from a Latin prefix “
quadri
” + adjective “
caudata
”, referring to the tail with four finger-like projections of the new species.
Distribution and habitat.
Northern
Japan
: Yoichi, on fine-grained sand, lower intertidal.
Central Japan
: Manazuru, on coarse sand with rocks, lower intertidal;
Imaihama
(type locality),
on fine-grained sand, lower intertidal
; Mihama, on fine-grained sand, lower intertidal; and Ishibu, fine-grained sand, lower intertidal.
Remarks.
The studied specimens show characteristics that, provisionally, allow us to include them within
Proschizorhynchella
. Species of
Proschizorhynchella
are schizorhynchids characterized by a simple male copulatory bulb forming a spiny cirrus and / or one or two stylets. The stylets are simple funnel structures, spiralized plates, or bear ridges (
Schilke 1970
;
Takeda and Kajihara 2018
). The diagnostic characteristics provided by
Schilke (1970)
are shared by a group of species that likely belong to different genera (
Noldt 1985
;
Karling 1989
). As noted by
Noldt (1985)
, the only character differentiating species of
Proschizorhynchella
from species of
ProschizorhynchusMeixner, 1928
, is the lack of the curved stylet in the former. However, the presence of a sclerotized mouthpiece in the bursa of species of
Proschizorhynchus
easily allows their differentiation from species of
Proschizorhynchella
(
Armonies 2023
)
.
Karling (1989)
elaborated more on the idea that
Proschizorhynchella
includes a paraphyletic group of species and questioned the use of the pharynx position and testes number to differentiate among schizorhynchid genera. However, these authors and posterior ones (
Takeda and Kajihara 2018
) did not refine the diagnosis of
Proschizorhynchella
or make other taxonomical changes. Unfortunately, the morphological disparities among species of
Proschizorhynchella
have not been tested through molecular phylogenetic analyses, and none of the 18 previously known species of the genus has been molecularly tested (see Discussion). Therefore, we refrain from updating the diagnosis of
Proschizorhynchella
until more molecular and morphological data are available to elaborate a comprehensive reclassification of this taxon.
Among the other 18 known species of
Proschizorhynchella
,
P. quadricaudatasp. nov.
can easily be differentiated because of the four finger-like projections of its posterior end, a characteristic not present in its congeners. The row of glands that opens along its proboscis lips is also unique in this species, and this character has only been reported for an undescribed species of
Proschizorhynchella
(see
Smith III et al. 2015
: Fig.
3 A
).
Other characteristics are very variable among species of
Proschizorhynchella
(see
Takeda and Kajihara 2018
). Most species have two eyes, two testes, and one gonopore. However, the number of adhesive belts varies from 0 to 3.
Proschizorhynchella quadricaudatasp. nov.
exhibits a single adhesive belt at the level of the pharynx. Only three other species of
Proschizorhynchella
present a single belt:
P. bivaginataSchilke, 1970
;
P. robustaNoldt, 1989
; and
P. schilkeiKarling, 1989
.
Proschizorhynchella bivaginata
is unique among these species because it has a cirrus in the copulatory bulb, whereas the other species have a stylet.
Proschizorhynchella schilkei
has two pairs of testes, and its stylet is a curved, comma-shaped hook, while
P. robusta
has a spiralized stylet (
Karling 1989
;
Noldt 1989
). In contrast, the stylet of
P. quadricaudatasp. nov.
is a simple and more or less straight tube.