Research Article |
Corresponding author: Mohsen M. El-Sherbiny ( ooomar@kau.edu.sa ) Academic editor: Danielle Defaye
© 2014 Mohsen M. El-Sherbiny, Ali M. Al-Aidaroos.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
El-Sherbiny M, M Al - Aidaroos A (2014) First report of the presence of Acartia bispinosa Carl, 1907 (Copepoda, Calanoida) in a semi-enclosed Bay (Sharm El-Maya), northern Red Sea with some notes on its seasonal variation in abundance and body size. ZooKeys 444: 95-118. https://doi.org/10.3897/zookeys.444.7633
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The calanoid copepod, Acartia bispinosa Carl, 1907, is reported for the first time in the Red Sea, where it is found to be an important copepod in the mesozooplankton community structure of the Sharm El-Maya Bay. Female and male are fully redescribed and illustrated of as the mouthparts of this species have never previously been described and figured. Acartia bispinosa was collected in the plankton samples throughout the year and showed two peaks of abundance, a pronounced one in April (4234 individuals m-3), and second smaller peak during November (1784 individuals m-3). The average total length of females varied between 1.32 and 1.53 mm at the end of June and January respectively. For males, the average total length fluctuated between 1.07 and 1.16 mm at end of June and March respectively. Temperature showed an inverse relationship with the body length (P > 0.001) and seemed to be one of the prime factors affecting the body length of both sexes.
Copepods, Acartia bispinosa , morphology, seasonal abundance, body size, Red Sea
Acartiidae Sars, 1903 is a speciose family of copepods, that inhabits estuarine and neritic environments all over the world from boreal to tropical regions (
So far, nine species of Acartia have been recorded from the Red Sea (
Acartia bispinosa specimens were collected at monthly intervals from Sharm El-Maya Bay (with an average depth of 3 m), in the northern Red Sea (27°51'36"N and 34°17'39"E) using a conical 0.1 mm mesh plankton net (mouth diameter of 0.4 m and total length of 160 cm) fitted with a Hydro-Bios flowmeter, from January to December 2009. The net was towed horizontally for ten minutes 0.5 m beneath the sea surface and filtered volume was estimated from the flowmeter reading and the net diameter. Immediately after collection, samples were fixed in a final concentration of 4% formaldehyde-seawater until analyses after several months. According to
Acartia amboinensis (F):
A. tokiokai
A. hamata
Female: Body (Fig.
Acartia bispinosa female from the northern Red Sea. A habitus, dorsal view B habitus, lateral view C rostrum and proximal part of the antennule, lateral view D urosome, dorsal view E urosome, ventral view F urosome, later view right G urosome, lateral view left H–I antennule. All scale bars in mm.
SEM micrographs of Acartia bispinosa female from the northern Red Sea. A rostrum, ventral view B urosome, fine hairs on the posterior margin of genital compound somite indicated by arrow, ventral view C proximal part of antennule, claw-like curved spine indicated by arrow, lateral view D Female leg 5.
Antennule (Fig.
Antenna (Fig.
Acartia bispinosa female from the northern Red Sea. A antenna B mandible C maxillule D maxilla E maxilliped F Leg 1 G leg 2, posterior surface H Leg 3, posterior surface I leg 4, posterior surface J third exopodal segment of leg 1, anterior surface K second endopodal segment of leg 3, anterior surface L basis of leg 4, anterior surface I leg 5 anterior surface. All scale bars in mm.
Mandible (Fig.
Maxillule (Fig.
Maxilla (Fig.
Maxilliped (Fig.
Swimming legs 1 to 4 (Fig.
Coxa | Basis | Exopod segments | Endopod segments | ||||
---|---|---|---|---|---|---|---|
1 | 2 | 3 | 1 | 2 | |||
Leg 1 | 0–0 | 0–0 | 1–1; | I-1; | 2,I,4 | 0–1; | 1, 3, 2 |
Leg 2 | 0–0 | 0–0 | 0–1; | 0–1; | 0,I,5 | 0–2; | 1, 2, 4 |
Leg 3 | 0–0 | 0–0 | 0–1; | 0–1; | 0,I,5 | 0–2; | 1, 2, 4 |
Leg 4 | 0–0 | 0–1 | 0–1; | 0–1; | 0,I,5 | 0–3; | 1, 2, 3 |
Leg 5 (Fig.
Male: Body (Fig.
Acartia bispinosa male from the northern Red Sea. A habitus, dorsal view B rostrum, ventral view C urosome, dorsal view D urosome, latero-ventra view E left antennule F right antennule G leg 5 H terminal segment of left exopod of leg 5 I terminal segment of right exopod of leg 5. All scale bars in mm.
Left antennule (Fig.
Right antennule (Fig.
Other mouthparts and leg 1 to leg 4 as in female. Male leg 5 (Figs
Acartia bispinosa showed some variations in both sexes. In female left projection of prosome can be bifurcated (Fig.
Temperature, salinity and chlorophyll a measurements over the 12 months investigation are presented in Figure
Adults of A. bispinosa were present in the plankton samples throughout the year in our study area with an annual average of 716 individuals m-3, forming 12.7% of total zooplankton community. Their abundance pattern showed two peaks (Fig.
The minimum, maximum, mean, standard error and standard deviation of total length as well as the prosome length of A. bispinosa are given in Table
Minimum, maximum, mean, standard error (SE) and standard deviation (SD) in total and prosome length of Acartia bispinosa sampled in the study area.
Sex | Length (mm) | Minimum (mm) | Maximum (mm) | Mean (mm) | SE (mm) | SD (mm) |
---|---|---|---|---|---|---|
Female | Total | 1.20 (June) | 1.57 (Jan.) | 1.42 | 0.017 | 0.059 |
Prosome | 1.02 (June) | 1.34 (Jan.) | 1.16 | 0.020 | 0.071 | |
Male | Total | 1.04 (June) | 1.19 (Jan.) | 1.12 | 0.007 | 0.026 |
Prosome | 0.83 (June) | 0.99 (Mar.) | 0.88 | 0.008 | 0.028 |
In Figure
Results of analysis of variance (ANOVA) showed significant differences between months for both female and male total length (F= 36.97, P < 0.000 for female and F= 15.29, P < 0.000 for male). Statistically, total and prosome length of females are inversely correlated with temperature (r= -0.639 and -0.664 respectively, P < 0.05) and positively with pH, salinity and dissolved oxygen (Tables
Pearson’s correlation coefficient between length measurements of Acartia bispinosa and environmental factors in the northern Red Sea.
Sex | Length | Temp. | pH | Salinity | DO | Chl. a |
---|---|---|---|---|---|---|
Female | Total | -0.631 0.028 |
0.621 0.031 |
0.658 0.020 |
0.771 0.003 |
-0.523 0.081 |
Prosome | -0.647 -0.023 |
0.610 0.035 |
0.590 0.043 |
0.704 0.011 |
-0.461 0.132 |
|
Male | Total | -0.609 0.036 |
0.708 0.010 |
-0.597 0.041 |
0.851 0.000 |
-0.677 0.016 |
Prosome | -0.333 0.290 |
0.394 0.205 |
-0.571 0.052 |
0.544 0.067 |
-0.350 0.269 |
Regression analysis of mean total and prosome length (mm) of Acartia bispinosa against surface water temperature in the northern Red Sea. (TL: Total length, PL: Prosome length and T: Water temperature).
Sex | Temperature regression equation | r2 | Sign. |
---|---|---|---|
Female | TL= -0.012 T+1.721 PL= -0.013 T+1.499 |
0.398 0.419 |
0.028 0.023 |
Male | TL= -0.005 T+1.241 PL= -0.002T+0.950 |
0.371 0.111 |
0.036 0.290 |
The original descriptions of A. bispinosa were brief and the drawings incomplete. Some morphological features were probably overlooked or undescribed by the previous authors (
In genus Acartia, there are currently 62 valid species (
Acartia bispinosa closely resembles A. amboinensis and A. erythraea, but it differs from the latter two species in the following characteristics in the female: (1) the second segment of antennule with strong claw-like spine curved proximally from midposterior margin, (2) the exopod of the female leg 5 reduced and swollen at the base posteriorly and distal two-thirds furnished medially with very fine spinules; in the male: (1) left leg 5 distal segment with 2 terminal spines, a stout spine on the mid-anterior surface with fine setae near its base and tuft of hairs proximally, row of spinules along medial margin, and several spinules along lateral margin.
We report this particular species from the Red Sea for the first time. There are three possible explanations of this discovery: 1) most of the plankton studies in the Red Sea were focused mainly in oceanic regions resulting in ruling out of this species which were dominant mainly in the neritic waters, 2) it may have beeen present but overlooked or misidentified in the previous studies and 3) it may be a representative of an invasive species transported in the Red Sea by human activities (possibly in ballast water). In a way we can conclude that the presence of this species in the Red Sea is obviously due to the overlooking by previous authors (e.g.
Acartia bispinosa is distributed mainly in the Indo-West Pacific region. It has been recorded from Ambon Bay, Malaysian coastal waters (
The seasonal distribution patterns of A. bispinosa clearly showed a pronounced peak at the end of April (temperature: 24.9 °C) and a smaller one at the end of October (temperature: 26.4 °C). This pattern is similar to those found in a tidal mangrove-fringing reef lagoon in Kenya, western Indian Ocean (
Monthly variations in the abundance of A. bispinosa did not show correlation with any of the measured environmental parameters (temperature, pH, salinity, dissolved oxygen and chlorophyll a concentration). This implies that water temperature alone could not explain the variation in the abundance of A. bispinosa, although water temperature as well as food quantity and quality has been suggested as key parameters influencing the abundance of many Acartia species (
The character of changes in the population dynamics of A. bispinosa as well as the very low densities of this species in the plankton from December to March allow us to conclude that the dominance of adult females in April and October, during the condition of gradual warming and cooling of coastal water, is linked to resting eggs, that are capable to give a new generation. Correspondingly, resting eggs of Acartia were found in bottom sediment of the different bays all over the world (
Seasonal variations in the body sizes have often been observed in marine invertebrates including copepods. In our study, the total length of A. bispinosa varies less than 51.9% and 41.2% around the annual means for both the females and males respectively. The observed seasonal variability of the body size, seems to be inversely related to temperature, as confirmed by the Pearson correlation. Similar seasonal variability in size with a winter maximum are commonly observed in copepods (
Variations in prosomal ends, genital somite and leg 5 of both sexes are common within other species of Acartia as reported in many previous works (e.g.
In the present study, A. bispinosa has been observed as a monospecific aggregation in the study area during daytime at the end of April. In tropical reef environments many acartiid copepod species exhibit swarms. For example, Acartia (Acanthacartia) spinata Esterly, 1911 and A. tonsa Dana, 1849 were reported by
In this study we have reported the presence of A. bispinosa in the Red Sea for the first time with full redescription. There are three possible explanations of this discovery: 1) most of the plankton studies in the Red Sea were focused mainly in oceanic regions resulting in ruling out of this species which were dominant mainly in the neritic waters, 2) it may have be present but overlooked or misidentified in the previous studies and 3) it may be a representative of an invasive species transported in the Red Sea anthropogenically (possibly in ballast water). The seasonal distribution patterns of A. bispinosa clearly showed a pronounced peak at the end of April and a smaller one at the end of October during the condition of gradual warming and cooling of coastal water, that may be linked to resting eggs, that are capable to give a new generation. Females showed their highest total and prosome length in January and the lowest were observed at the end of June. The highest total and prosome length of the male were detected in March and the lowest value appeared in June. This variability of the body size, seems to be inversely related to temperature, indicating the influence of other environmental parameters.
The authors are grateful to the anonymous referees for their valuable comments and suggestions. We thank Dr. Satheesh Sathianeson and Dr. Gopikrishna Mantha for their critically reading the first draft whose suggestions and comments greatly improved this manuscript.