Distribution and Taxonomy of Shallow Marine Ostracods from the Western Coast of the Red Sea , Egypt

A total 5849 individuals of ostracods constituting twenty species were collected from five shallow marine sites along the area from El-Quseir to Marsa Alam on the West Coast of the Red Sea. The twenty ostracod species belonging to sixteen genera and ten different families. The three genera; Loxoconcha, Neonesidea and Xestoleberis have high species diversity. Furthermore, the species Loxoconcha ghardaqensis, Xestoleberis rotunda, Paranesidea fracticorallicola, Tanella gracilis and Neonesidea schulzi were the best recognized in the collecting region. Otherwise, the distribution of the collected ostracod species in relation to environmental variables and plants were discussed in detail here. Based on this, it is concluded that, vegetation type appears to be the most important factor controlling the distribution of ostracod species in the investigated area. Also, other factors such as, water temperature, salinity, dissolved oxygen, pH and electrical conductivity play an important role. Scanning electron microscope images of valves are delivered of the recorded taxa. These fauna displays close affinities to those of the Red Sea and the Indo-Pacific region.


Introduction
Ostracoda are a class of small crustaceans distinguished by a carapace of two valves enveloping soft parts and appendages.The dorsal margin of the two valves is joined by hingement.Ostracods are inhabiting in all watery environments (marine, brackish, freshwater and terrestrial) and they are playing vital  Species of osracods were examined in details to identify to the species level.As well as some references used in of ostracods [1] [6] [7] Bonaduce et al. [2]; Bonaduce et al. [3] [8] [9] [10]; Nishath et al. [11] [12] and [5].

The Water Parameters
During the present study, sea water temperature, salinity, pH, dissolved oxygen, electrical conductivity and the total dissolved salts (TDS) are summarized in Table 2.The water temperature in the area under investigation ranged between 28.8˚C -34.7˚C.Moreover, the salinity is high and fluctuated between 41.22 to 42.75‰.By comparing the pH values in all collection sites showing small variations and ranged from 8.27 to 8.65, this is indicated that the studied area is weakly alkaline.The dissolved oxygen in the study area ranged from 6.9 to 8.8 (mg/l) and the electrical conductivity fluctuates between 63.2 and 64.5.Additionally, the total dissolved salts (TDS) were observed in the range of 37.98 to 39.
49 g/l.According to the above result, the ecological factors have an important role in the distribution and numbers of Ostraccoda in the Red Sea.
Nishath et al. [13] reported that, salinity has a direct effect on the number and abundance of specimens in marine and marginal marine environments.Moreover, [14] stated that dissolved oxygen considered one of the factors contributing to the abundance of some living inhabitants.
The most common species in the collecting region are Loxoconcha ghardaqensis, Xestoleberis rotunda, Paranesidea fracticorallicola, Tanella gracilis and Neonesidea schulzi, whereas, Hemicytherura videns aegyptica and Caudites sublevis occurred in few numbers.Ostracods are highly diverse in the first and Table 2. Water temperature (˚C), salinity (pp), dissolved oxygen (DO), pH and total dissolved salts (TDS) and electrical conductivity (mS/cm) at the sampling stations.the third sites constituting 29.37% and 32.39%, respectively.While, the second, fourth and fifth sites are less diverse in ostracods constituting 10.17%, 16%, 12.05%, respectively.On the other hand, the three genera Loxoconcha, Neonesidea and Xestoleberis displayed a high diversity of species.
The plants on the sites under study deliver food and shelter for ostracod species [5] [15] [16] [17].Moreover, [18] noted that the density of ostracods fluctuates according to the grade of structure complexity of algae.
In the current study, it is generally observed that sites which are covered with macro-algae are occupied by dense ostracods (e.g., site I and site III).Similarly, collecting sites which covered with mangrove trees have less numbers of ostracods (e.g., sites II, IV and V).

Systematic Descriptions
The current study presents identification of twenty species of Ostracoda from Remarks: The caudal process of our specimen is smaller than that of Bonaduce et al. [1] [2] and [12].As well as, our species differs from that of [10] in the lateral ornamentation and dorsal margin, but resembles it in the shape of caudal process at the dorsal margin.Loxoconcha gisellae Bonaduce et al. [23], pl.Remarks: The current species are closely related to that of [19] and larger than it.But, the caudal process of our species is shorter than that of [19] and the reticulation of the dorsal margin is less obvious.Also, the present species resemble Loxoconcha gurneyi [21], but differ from it in carapace ornamentation and outlines.Our species are closely related to L. amygdalanux but differs in the sinus ventral margin.Loxoconchella dorsobullata [1], pls.21-22, Figures 101-113.Loxoconchella sp.[25], Figure 51.Loxoconchella dorsobullata Hartmann: Bonaduce et al. [1], pl.10: Figure 10.Loxoconchella dorsobullata Hartmann: [8], pl. 2, Figures 6-9.
Measurements: L = 0.57 mm, H = 0.35 mm Geographical distribution: Red Sea (Hurghada, Gulf of Aqaba and Jeddah in Saudi Arabia).Occurrence: L. dorsobullata is widely distributed species in the Red Sea and occurs with several numbers.
Ecology: The present species found in shallow water and occurred in large numbers in algae.The suitable ecological factors for this species are: Water temperature equal 28˚C, pH is 8.27, salinity is 42.13‰.Also, dissolved oxygen is 6.9 (mg/l).Remarks: Our specimens (L.dorsobullata) is larger than those of [1] and [8].
Moreover, the caudal process of our species resembles that of [8] and more obvious than that of Bonaduce et al. [2].The pores on the carapace of L. dorsobullata in [8] are more obvious than our specimen.Xestoleberis ghardaqae [1], pl.Remarks: The ornamentation of Paranesidea fracticorallicola carapace consists of circular punctate be wide at the center and narrow at the peripheral margins.The left valve of present species is longer than the right one and overlap it.
Our species have blunt spines at the dorsal margin, which are absent from that of Bonaduce et al. [27].
Genus: Neonesidea Maddocks, 1969a Occurrence: This species occurred in large numbers in the fourth site and moderate numbers in the remaining sites.
Remarks: The carapace of Moosella striata characterized by the presence of similar striated ridges without fossae, however, the carapace surface of the same species of [12] intercalated with fossae.Moreover, the present species is larger than that of M. striata which recorded by [12].Tanella gracilis Kingma: [12], Figure 7: 97-100.
Occurrence: Tanella gracilis is widely distributed species in the Red Sea and occurs with several numbers in the first and third sites.Ecology: This species found in shallow water and occurred in large numbers in algae.The suitable environmental factors for this species are: Water temperature ranges between 28.8˚C -32.6˚C, pH varies between 8.27 and 8.48, salinity fluctuates from 42.13‰ to 41.22‰.Also, dissolved oxygen ranges from 6.9 to 7.2 (mg/l).Remarks: The lateral outlines Aglaiella sp.resembles our species, but the latter has a wider inner lamella.On the other hand, there are no differences between the present species and ones of [1] and Bonadouce et al. [2].

Discussion
Macro-algae and mangrove trees of the Red Sea are inhabited by different ostracod species.The present study recorded and counted the ostracod species from five collection sites (on the Egyptian Red Sea coast), three sites of them are inhabited by mangrove trees and the other two ones are covered with macro-algae.We concluded that, collection sites occupied by macro-algae have yielded larger numbers and diversity of ostracods than those occupied by mangrove trees.So, the diversity and abundance of ostracod species are controlled by the type vegetation.[5] concluded that the areas with the algae contain dense communities of ostracod species.Twenty Shallow marine ostracods of five samples from Al-Quseir to Marsa Alam on the Egyptian Red Sea Coast were studied.[4] collected twenty-three ostracod species belonging to 21 genera, and 13 families from Safaga bay along the Red Sea coast, Egypt.Similarly, [5] collected 36 and 26 ostracod species from Wadi Gemal area and Abu Ghoson area, respectively.During our study, the most common species in the collecting region are Loxoconcha ghardaqensis, Xestoleberis rotunda, Paranesidea fracticorallicola, Tanella gracilis and Neonesidea schulzi, whereas, Hemicytherura videns aegyptica and Caudites sublevis occurred in few numbers.[11] reported 83 species belonging to 54 genera from Gulf of Oman at depths ranging from 30 to 103 m.The ostracod species Hemicytherura aegyptica, Tanella gracilis, Moosella striata and Loxoconcha ornatovalve are recorded by [11].
Tanella gracilis is common in algae in the area under study.[19] and [37] reported this species from the lagoon in the Arabian Gulf and from the deep water of the Gulf of Oman, respectively.[39] also found T. gracilis in the western coast of India and [38] found it in Indonesia as well as the western coast of Australia.
The recorded fauna show close affinities to those of the Red Sea and the Indo-Pacific region.Also, Tanella gracilis have wide distribution (Red Sea, Gulf of Aden, Kuwait, Gulf of Oman, Arabian Gulf, Australia, west African coast, Kenya, Malaya, Andaman Islands, India, Reunion Islands).Furthermore, Neonesidea schulzi occurred in east Coast of Africa and Neonesidea michaelseni found in Australia and Polynesia.Paranesidea fracticorallicola occurred in Madagascar and Gulf of Oman.Add to that, Moosella striata present in Kenya.Although, most of studied species occurred in red sea and the Indo-pacific region.

Figure 1 .
Figure 1.A map study area with photographs of the five collecting sites (from google earth).

Figure 2 .
Figure 2. Scanning Electron Microscope showing.(a) External view of female carapace of Loxoconcha ghardaqensis; (b): Internal view of left valve of male of L. ghardaqensis (c) Internal view of right valve of female of L. ghardaqensis (d) External view of left valve of Loxoconcha ornatovalve (e) Internal view of left valve of L. ornatovalve (f) External view of right valve of Loxoconcha gisellae.

Figure 3 .
Figure 3. Scanning Electron Microscope showing.(a) Lateral view of carapace of Loxoconchella dorsobullata (b) Ventral view of carapace of L. dorsobullata (c) Lateral view of carapace Xestoleberis ghardaqae (d) Internal view of right valve of female of X. ghardaqae (e) External view of left valve of X. rotunda (f) Internal view of right valve of X. rotunda.

Figure 4 .
Figure 4. Scanning Electron Microscope showing.(a) External view of left valve of Paranesidea fracticorallicola (b) Internal view of left valve of P. fracticorallicola (c) External view of right valve of P. fracticorallicola (d) Internal view of right valve of P. fracticorallicola (e) External view of left valve Neonesidea schulzi (f) Internal view of right valve of male of N. schulzi.

Figure 5 .
Figure 5. Scanning Electron Microscope showing.(a) External view of right valve of-Neonesidea michaelseni (b) External view of left valve of Moosella striata (c) Internal view of opening carapace of Moosella striata (d) External view of left valve of Hiltermannicythere rubrimaris (e) Internal view of left valve Hiltermannicythere rubrimaris (f) Internal view of right valve of Cyprideis littoralis.

SubfamilyFigure 6 .
Figure 6.Scanning Electron Microscope showing.(a) External view of left valve of male of Hemicytherura videns aegyptica (b) Internal view of right valve of male H. videns aegyptica (c) External view of carapace of female of H. videns aegyptica (d) Internal view of right valve of female of H. videns aegyptica (e) External view of left valve of Tanella gracilis (f) Internal view of left valve of Tanellagracilis.

Figure 7 .
Figure 7. Scanning Electron Microscope showing.(a) External view of carapace of Callistocythere arcana (b) Internal view of right valve of Callistocythere arcana (c) External view of right of Leptocythere arenicola (d) Internal view of left valve of female of Leptocythere arenicola (e) External view of left valve of Quadracythere borchersi (f) Ventral view of carapace of Quadracythere borchersi.

3. 3 . 17 .Figure 7 Figure 8 .
Figure 8. Scanning Electron Microscope showing.(a) Internal view of left valve of Quadracythere borchersi (b) External view of right valve ofCaudites sublevis (c) External view of rightvalve of Paradoxostoma altecaudatum (d) External view of leftt valve ofGhardaglaia triebeli (e) Internal view of left valve of Ghardaglaia triebeli (f) Internal view of right valve of Ghardaglaia triebeli.

Table 1 .
Sampling stations and geographical position.

Table 3 .
Distribution the individual numbers of ostracod species in five collecting sites.