Shallow water hydroids (Cnidaria, Hydrozoa) from the 2002 NOWRAMP cruise to the Northwestern Hawaiian Islands
Author
Calder, Dale R.
Author
Faucci, Anuschka
0000-0001-9002-8987
anuschka@hawaii.edu
text
Zootaxa
2021
2021-12-24
5085
1
1
73
journal article
288831
10.11646/zootaxa.5085.1.1
90f1f9ec-1bd9-4996-a544-48d41a9e0240
1175-5326
5802920
12FC3342-F2A0-4EE1-9853-9C5855076A10
Halopteris alternata
(
Nutting, 1900
)
Fig. 13e, f
Plumularia alternata
Nutting, 1900: 62
, pl. 4 figs 1, 2.
Halopteris diaphana
.—
Cooke, 1977: 99
, fig. 26.—
Carlton & Eldredge, 2009: 36
[not
Halopteris diaphana
(
Heller, 1868
)
].
Halopteris diaphena
.—
Coles
et al
., 2004: 73
[incorrect subsequent spelling; not
Halopteris diaphana
(
Heller, 1868
)
].
Type
locality.
Bahamas
:
Barracuda Rocks
(
Nutting 1900: 62
, as
Plumularia alternata
)
.
Voucher material.
Laysan Island
, on hydroid stem,
18.ix.2002
, two colonies or colony fragments, to
8 mm
high, without gonothecae, coll.
A. Faucci
,
ROMIZ
B5458
.
Remarks.
Hydroids examined here were referable to
Halopteris
Allman, 1877
, and to the “
H. diaphana
” species group recognized within that genus by
Schuchert (1997)
. Included in the group by him were
H. diaphana
(
Heller, 1868
)
,
H. tenella
(
Verrill, 1873b
)
,
H. alternata
(
Nutting, 1900
)
,
H. billardi
(
Vannucci, 1951
)
, and
H. platygonotheca
Schuchert, 1997
.
Halopteris violae
Calder
et al
. 2003
has subsequently been assigned to the same group. Within that assemblage, specimens examined here from Laysan Island are closest to
H. alternata
. Characters distinguishing the species from others in the cluster have been reviewed by
Schuchert (1997)
and
Calder
et al
. (2019)
.
For much of the 20
th
century,
H. alternata
was included in the synonymy of
H. diaphana
. Confusion over the status of two species was addressed and resolved by
Schuchert (1997)
. He resurrected
H. alternata
as valid based on its distinctive trophosomal and gonosomal characters. DNA barcoding has confirmed that the two are distinct species (
Moura
et al
. 2018
;
Galea
et al
. 2018
). In
H. alternata
, an axillar nematotheca is usually present behind each cauline hydrotheca, one nematotheca rather than two or three is present on the athecate hydrocladial internodes, and female gonothecae are fusiform and mostly straight rather than cornucopia-shaped. Additional characters distinguishing the two were noted by
Ansín Agís
et al.
(2001)
. In
H. alternata
, colonies were often found to be geniculate rather than straight, especially in younger parts. Also, they found segmentation of the hydrocaulus to be homomerous in basal parts but heteromerous in younger and apical parts, rather than being completely heteromerous as in
H. diaphana
.
Halopteris vervoorti
Galea, 2008
, another similar species, differs from
H. alternata
in having paired rather than single cauline axillar nematothecae (
Galea 2008
;
Galea
et al.
2018
;
Calder 2020
).
Halopteris alternata
is widely distributed in warm parts of the western North Atlantic (
Oliveira
et al
. 2016
; Calder 2019), and it has been reported as well from the eastern Atlantic (
Ansín Agís
et al.
2001
). In the Pacific, records of the species exist from
Ecuador
(
Calder
et al
. 2019
,
2021
), and hydroids from Hawaii that have been identified earlier as the mostly European
H. diaphana
are taken here to have been based instead on
H. alternata
.
Obvious cryptic diversity has been identified within the
H. alternata
complex by
Moura
et al
. (2018)
.
Reported Distribution.
Hawaiian archipelago. Oahu: Kaneohe Bay (
Cooke 1977
, as
Halopteris diaphana
).— Maui: Kahului Harbor, Pier 1 (
Coles
et al
. 2004
, as
H. diaphena
sic); Kahului Harbor, Pier 2 (
Coles
et al
. 2004
, as
H. diaphena
sic).
Elsewhere. Western Atlantic (
Oliveira
et al
. 2016
; Calder 2019); eastern Atlantic (
Ansín Agís
et al.
2001
); eastern Pacific (
Calder
et al
. 2019
,
2021
); central Pacific (
Cooke 1977
, as
Halopteris diaphana
); possibly Indian Ocean (
Jarvis 1922
, as
Plumularia alternata
;
Gravely 1927
, as
Plumularia
sp.
nr.
alternata
).