A New Species Of Ectinosoma Boeck, 1865 (Copepoda : Harpacticoida : Ectinosomatidae) From Northwestern Mexico

12 Pages·2001·3.6 MB·English

by  S Gómez

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
114(1):207-218. 200L
A new species of Ectinosoma Boeck, 1865 (Copepoda: Harpacticoida:
Ectinosomatidae) from northwestern Mexico
Samuel Gomez and Sybille Seifried
(SG) Institute de Ciencias del Mar y Limnologia, Unidad Academica Mazatlan, Universidad
Nacional Autonoma de Mexico, Joel Monies Camarena s/n, Ap. Postal 811, Mazatlan 82040,
Sinaloa, Mexico, Limburgs Universitair Centrum, Dept. SBG, Researchgroup Zoology,
Universitaire Campus Building D, B-3610, Diepenbeek, Belgium (SS) FB7/AG Zoosystematic
and Morphologie, University of Oldenburg, 26111 Oldenburg, Germany
—
Abstract. A new species of harpacticoid copepod, Ectinosoma mexicanum
(Harpacticoida: Ectinosomatidae), is described from a coastal lagoon in north-
western Mexico (Sinaloa state). Ectinosoma mexicanum appears to be allied to
E. porosum (Wells, 1967) by sharing a robust endopod on P2 and P4 and a
strong setae on the first and second endopodal segment ofP2 and P4. The new
Mexican ectinosomatid also has the seta next to the outermost seta of exopod
of P5 barely longer than the exopod inner edge as in E. porosum and E.
mediterraneum Kunz, 1975.
In 1991 a one-year study on the impact investigation. Observations and drawings
of organic enrichment on the distribution were made from the whole and then dis-
and abundance of meiofauna in a coastal sected specimen mounted in glycerin, at
lagoon in the southeastern Gulf of Califor- 1250X using a Leitz Periplan phase con-
nia (Mexico) was undertaken (G6mez-No- trast light microscope equipped with a
guera & Hendrickx, 1997). During this drawing tube. The terminology proposedby
study 63 harpacticoid taxa were identified, Huys & Boxshall (1991) for the general
most of which turned out to be new to sci- morphological description, Koomen (1992)
ence. Ectinosomatidae was by far the most and Seifried & Durbaum (2000) for U-
&
abundant family throughout the study pe- pores, Seifried (1997) and Seifried Diir-
riod (39.4%), and was represented by spe- baum (2000) for the somitic ornamentation
cies of Halectinosoma Lang, 1965, Hastig- (palisades), and Moore (1976) for hyaline
erella Nicholls, 1935, Pseudectinosoma frill, were adopted. Abbreviations used in
Kunz, 1935 and Ectinosoma Boeck, 1865. the text and tables: P1-P6, first to sixth leg;
This contribution deals with the description EXO, exopod; END, endopod; ae, aesthe-
of the only species ofEctinosoma found in tasc.
the sediment samples taken in Ensenada del
Pabellon lagoon (northwestern Mexico). Family Ectinosomatidae Sars, 1903
Genus Ectinosoma Boeck, 1865
Materials and Methods Ectinosoma mexicanum, new species
Figs. 1-6
Quantitative triplicate sediment samples
—
were taken in Ensenadadel Pabellonlagoon Type material. A single dissected female
(Sinaloa, northwestern Mexico). The sam- (holotype) catalogued EMUCOP-020591-17,
ple strategy was described in G6mez-No- deposited in the collection of the Institute of
&
guera Hendrickx (1997). Harpacticoids Marine Sciences and Limnology, Mazatlan
were stored in 70% ethanol prior to further Marine Station.
208 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
—
Type locality. Ensenada del Pabellon transverse rows ofpalisades and evenly dis-
lagoon (24°19'-24°35'N, 107°28'- tributed depressions and U-pores; ventral
107°45'W). Le—g. S. Gomez, May 1991. surface plain, with U-pores; P6 represented
Diagnosis. Ectinosomatidae. Rostrum by 2 setae, genital pore located in proximal
relatively large and fused to cephalothorax. half; hyaline frill of first post genital ab-
Antennule six-segmented. Armature for- dominal somite as in sixth thoracic somite.
mula of P1-P4 (EXO/END): 0.1.123/ Second and third post genital abdominal
1.1.221; 1.1.223/1.1.221; 1.1.323/1.1.221; somites ornamented with 3 and 4 rows of
1.1.323/1.1.221. First and second endopo- palisades; second post genital abdominal
dal segment of P2-P4 with one strong spi- somite with U-pores and with denticulate
nulose seta. Endopod ofP2-P4 robust, first hyaline frill; third post genital abdominal
endopodal segment ofP2 and P3 as long as somite without U-pores, with protruded
wide, first endopodal segment of P4 wider pseudoperculum dorsally, reaching to distal
than long. Seta next to the outermost seta third of anal segment, with entire striated
of exopod of P5 barely longer than inner hyaline frill ventrally (Fig. 2C). Anal seg-
edge of exopod. Setae I and VI of caudal ment (fourth post genital abdominal somite)
rami spine-like.— with palisades and U-pores. Caudal rami
Description. Habitus (Fig. lA-B, 2A- about 1.5 times longer than broad, with 7
C), fusiform. Length 773 |xm including ros- elements. Posterior dorsal edge of caudal
trum and caudal rami. Rostrum (Fig. lA) rami terminating as an acuminate lappet;
relatively large, fused with cephalothorax. rami with 1 ventral proximal row of small
The latter aboutVs oftotal body length, with palisades, and 2 sets of ventrolateral spi-
denticulate hyaline frill and sensilla; integ- nules at base of elements I and II; setae I
ument ornamented with tiny depressions ar- and VI developed as spines.
ranged longitudinally and perforated by U- Antennule (Fig. 3A), six-segmented. Sur-
pores. Surface of third to fifth thoracic so- face ofsegments smooth. Armatureformula
mites with tiny depressions arranged as in 1.10.3+ae.0.3.3+ae.
cephalothorax; U-pores present. Third tho- Antenna (Fig. 3B): basis massive, with 2
racic somite without palisades, fourth and inner long elements (indicated in Fig. 3B).
fifth thoracic somites with 2 and 4 trans- Endopod two-segmented; first segment
verse rows of palisades, respectively; third bare; second segment ornamented with
to fifth thoracic somites with denticulate strong and short proximal spinules and with
hyaline frill, that of the fifth one deeper longer spinules at base of 2 inner lateral
than that of the third and fourth thoracic spines; with 6 distal spines. Exopod three
somites. Fifth thoracic somite with 1 trans- segmented; first segment as long as third
verse row of small palisades and 3 trans- and about 2.3 times longerthan second one,
verse rows of long palisades. P5 bearing- with one seta; second segment with 1 spine;
somite (sixth thoracic somite) ornamented third segment with 2 spines and ornamented
with 3 transverse rows of small palisades with subapical set of spinules, one of them
and 1 row oflong palisades, and with even- markedly stronger.
ly distributed tiny depressions (possibly Mandible (Fig. 3C): gnathobase of coxa
pores) and U-pores; with denticulate hya- with a strong spinulose distal spine on cut-
line frill. W:L ratio of genital double-so- ting edge, 1 strong and 4 smaller teeth; ba-
mite, 1.19 (width measured in the proximal sis large with 2 long and slender inner setae
wider part of seventh thoracic somite); dor- and 1 thickened and spinulose inner ele-
sal surface with remains of ancestral sub- ment. Endopod one-segmented, with 8 se-
division between seventh thoracic somite tae, 2 each ofdistal 4 fused at base forming
and first post genital abdominal somite (in- 2 pairs of elements. Exopod one-segment-
dicated in Fig. lA-B) and ornamented with ed, small, with 1 lateral and 2 distal setae.
VOLUME NUMBER
114, 1 209
100pm
B,Fsiugr.fa1c.e oErcntaimneontsaotmiaonmeoxficfoaunrutmh.tonesewvesnptehcitehso.raHcoilcotsyopmei,tefsemaanlde,firEstMUpoCsOtPg-e0ni2t0al59a1b-do1m7inAal hsoambiitteu.s' dorsal-
210 PROCEEDINGS OFTHE BIOLOGICAL SOCIETY OF WASHINGTON
B
100Mm
Fig. 2. Ectinosoma mexicanum, new species. Holotype, female, EMUCOP-020591-I7. A, urosome, ventral
(first urosomite omitted); B, urosome, lateral, (first urosomite omitted); C, part ofanal segment and left caudal
ramus, ventral.
VOLUME 114, NUMBER 1 211
lOOMm 100pm
Fig. 3. Ectinosoma mexicanum, new species. Holotype female, EMUCOP-020591-17. A, antennule, third
segment separated from second and fourth; B, antenna; C, mandible; D, maxillule; E, maxilla; F, maxilliped
(endopodal setae lost during dissection).
212 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASfflNGTON
Fig. 4. Ectinosoma mexicanum, new species. Holotype female, EMUCOP-020591-17. A, PI, anterior; B,
P2, anterior.
VOLUME NUMBER
114, 1 213
Fig. 5. Ectinosoma mexicanum, new species. Holotype female, EMUCOP-020591-17. A, P3, anterior; B,
P4, anterior.
214 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
50 pm
Fig. 6. Ectinosoma mexicanum, new species. Holotype female, EMUCOP-02059I-17, Fifth leg, anterior.
Maxillule (Fig. 3D): arthrite of praecoxa exopod with 2 seta, endopod with 6 setae,
with 4 apical spines and 2 bare setae; coxa 2 each fused at base to form 3 pairs of se-
and basis fused, the latter with 3 setae; ex- tae.
opod and endopod not articulating at base; Maxilla (Fig. 3E): syncoxa with 3 en-
VOLUME NUMBER
114, 1
215
50 Mm
19667?.88..44'.221,. PEnrdorpord:of.P4L^~ ^^^"^' ''''' «°^°^^P^ ^-^^^ ^--^ ^--y Muscu. (London)-
216 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
—
Table 1. Armatureformulaofswimminglegs(Pl- dian anterior, and 1 distal and 1 median
P4) ofEctinosoma mexicanum. posterior U-pore; inner baseoendopodal ex-
pansion reaching middle of exopod. Exo-
EXO END
pod widerthan long, basal limitonlyvisible
PI I-O; I-l; in, II, 1 0-1; 0-1; I, n, 2 on posterior face; with 4 marginal setae and
P2 I-l; I-l; III, II, 2 0-1; 0-1; I, II, 2 ornamented with row of long spinules in
P3 I-l; I-l; III, II, 3 0-1; 0-1; L n, 2
P4 I-l; I-l; III, n, 3 0-1; 0-1; L n, 2 the middle and at the base ofthe three larg-
est marginal elements; outermost seta about
3.5 times longer than adjacent one, the lat-
dites, proximal endite with 3, middle endite terbarely longer than inneredge ofexopod;
with 2, distal one with 3 setae; allobasis seta adjacent to innermost seta about 1.8
with 3 setae medially. Endopod one-seg- times longer than innermost element, the
mented, with 2 long spines and 5 setae. latter about 1.2 times longer than outermost
Maxilliped (Fig. 3F): badly damaged; the seta of base—oendopod.
endopodal setae missing. Basis with 2 par- Remarks. At present about 35 species
allel rows of spinules. ofEctinosomatidae (apart fromE. mexican-
PI (Fig. 4A), with massive coxa orna- um new species), have been attributed to
mented with distal spinules. Basis with out- the genus Ectinosoma. The taxonomy and
er seta and inner strong spine, with spinules phylogeny of this genus has been obscured
at base of exo- and endopod and close to by poor descriptions that in most cases lack
inner spine. Rami three-segmented, orna- sufficient detail. Moreover, no revisions of
mented with strong spinules; exopod barely the genus are available and nothing is
reaching beyond second endopodal seg- known about the phylogenetic relationships
&
ment. Inner seta of second endopodal seg- of this taxon (Seifried, 1997; Seifried
ment spinulose at tip. Armature formula as Diirbaum, 2000).
in Table 1. Ectinosoma mexicanum and E. porosum
P2-P4 (Fig. 4B, 5A-B), with massive (Wells, 1967), seem to be related by the fol-
coxa ornamented with row of spinules in lowing synapomorphies: strong spinulose
outer distal corner. Basis ornamented with seta on the first and second endopodal seg-
strong spinules at base of exopod and with ment of P2 and P4, and by the robust en-
minute ones at base ofendopod and in dis- dopod of P2 in which the first segment is
tal inner comer, the latter with dentiform as long as wide. Unfortunately, Wells
process. Rami three-segmented, ornament- (1967) illustrated only the third exopodal
ed with spinules as in PI. Exopod of P2 segment ofP3, and did not discuss the gen-
barely reaching beyond second endopodal eral morphology of P4. In order to check
segment, of P3 and P4 reaching middle of the general morphology of P3 and P4 ofE.
third endopodal segment. Endopods robust; porosum, the only material available (Ho-
first endopodal segment of P2 and P3 as lotype 1967.8.4.21) was borrowed from the
long as wide, of P4 wider than long; first Natural History Museum (London). Unfor-
and second endopodal segment of P2-P4 tunately, the only slide on which the dis-
with strong curved setae ornamented with sected holotype of E. porosum was mount-
2 rows of spinules. Armature formula as in ed was badly damaged during transit and
Table 1. only the mouth parts, PI, P2, P4, P5 and
P5 (Fig. 6): baseoendopod with 2 inner abdomen were successfully recovered.
setae, innermost about 1.8 times longerthan The general morphology of P4 of E. po-
outer one; inner expansion of baseoendo- rosum (Fig. 7) showed that the robust rami
pod ornamented with fine spinules at base constitutes a synapomorphy for E. porosum
of both setae, and with strong ones along and E. mexicanum. On the other hand, the
inner margin of posterior face; with 1 me- general morphology of P2-P4 of E. mexi-