Is sea snakes poisonous?....(SEA SNAKES)

 

 SEA SNAKES

Introduction

• Sea snakes are air-breathing, highly venomous reptiles.
• They are closely related to front-fanged cobras, kraits, and Australian elapids.
• The subfamily Hydrophiinae lives in marine environments for most or all of their lives.
• Most sea snakes evolved from land-dwelling ancestors but are now adapted to aquatic life.
• The genus Laticauda retains some ancestral traits, allowing limited movement on land.
• They inhabit warm coastal waters from the Indian Ocean to the Pacific.

Scientific Classification

• Kingdom: Animalia
• Phylum: Chordata
• Subphylum: Vertebrata
• Class: Reptilia
• Order: Squamata
• Suborder: Serpentes
• Family: Elapidae
• Subfamily: Hydrophiinae
• Viviparous Sea snakes (Hydrophiini): e.g., Hydrophis, Aipysurus
• Oviparous Sea kraits (Laticaudini)

Basic Biology

• Sea snakes have paddle-like tails and laterally compressed bodies, resembling eels.
• They do not have gills and must surface regularly to breathe.
• Some species possess highly potent venom.
• All species have valved nostrils and a sublingual salt-excreting gland.
• They can dive deeper than 100m and remain submerged for up to 2 hours.
• Their skin is thick, protecting against fluid loss and salt ion penetration.
• Coloration varies greatly; young snakes are more distinctly patterned than adults.

Habitat

• Sea snakes prefer shallow waters near land, around islands, and sheltered areas.
• They can swim up rivers and have been found up to 160 km from the sea.
• They are attracted to light and gather in large numbers near harbors.
• They enjoy basking on the water's surface, especially on calm days.

Feed & Feeding

• Their diet includes small fish, fish eggs, eels, piranhas, and marine invertebrates.
• Shrimp is their favorite food, and they occasionally eat young octopuses.
• Sea snakes can swallow prey larger than themselves and use camouflage to strike.

Marine Adaptations

Sea snakes have several adaptations that help them thrive in marine environments:

1. Tail Adaptation
• Most Hydrophiinae have a paddle-like tail that enhances swimming ability.
• Many species have laterally compressed bodies, especially pelagic species.
2. Scale Adaptation
• Ventral scales are reduced in size, making them almost indistinguishable.
• This adaptation makes them helpless on land, but they live their entire lives at sea.
• The genus Laticauda retains enlarged ventral scales, allowing them to grip on land.
3. Respiration
• Sea snakes have a unique respiratory system compared to terrestrial snakes.
• Pelamis platura can absorb up to 33% of its oxygen through the skin.
• They can dive for 30 minutes to 2 hours between breaths.
• They have a long lung that extends nearly the entire length of their body for efficient gas exchange.
• They also perform cutaneous respiration, allowing oxygen to diffuse through their skin.
4. Swimming
• Their elongated bodies are naturally suited for swimming.
• The paddle-shaped tail enhances locomotion in water.
• The large lung aids buoyancy and may store air for dives.
5. Salt Excretion
• Sea snakes ingest more salt than land animals due to their diet and seawater.
• They have evolved a salt-excreting gland under the tongue to regulate blood salt concentration.
6. Photoreceptors
• Aipysurus laevis has photoreceptors in its tail skin, helping it detect light and remain hidden in coral holes during the day.

Sea Snakes

Laticauda colubrina

• Common Names: Amphibious Sea Snake, Sea Kraits, Banded Sea Krait, Yellow-lipped Sea Krait
• Characteristics:
• Head shields entire
• Nostrils lateral
• Nasal shield separated by the internasals
• Color: Light or dark bluish-grey above, yellowish below, with dark-brown or black bands
• Head: Entirely black with a yellow snout
• Size: Maximum length of  1.42  metres
• Habitat: Found among rocky crevices around coasts
• Distribution: From the Persian Gulf, around the coasts of India to southern China, and northern coasts of Borneo and Java. In India, found in the Bay of Bengal (Kolkata) and Andaman and Nicobar Islands.

Laticauda laticaudata

• Characteristics:
• Closely related to L. colubrina
• Differs by the absence of an azygous prefrontal shield on the head and reduced number of scales (19 rows around the body)
• Color: Light or dark bluish-grey above with numerous black bands, belly yellowish
• Size: Maximum length of  1.07  metres
• Habitat: Usually found in the vicinity of rocky coasts
• Distribution: From the Bay of Bengal and the seas south of Japan to the coast of Australia and islands of Oceania. In India, found in the Bay of Bengal (Kolkata) and Nicobar Islands.

Effect of Venom

• Bites may be painless and go unnoticed.
• Symptoms:
1. Early symptoms:
• Headache
• Thick-feeling tongue
• Thirst
• Sweating
• Vomiting
2. Symptoms after 30 minutes to several hours:
• Generalized aching
• Stiffness and tenderness of muscles
• Paralysis of muscles involved in swallowing and respiration (can be fatal)
• After  3-8 hours:

• Myoglobin may appear in blood plasma, causing urine to turn dark reddish, brown, or black, potentially leading to acute renal failure.

• After  6-12  hours:

• Severe hyperkalemia can lead to cardiac arrest.

Threats

• Sea snakes are a delicacy in countries like Singapore, Hong Kong, and Japan.
• In Japan, millions of sea snakes are shipped from the Philippines for edible purposes.
• Sea snakes are roasted and smoked, served with side dishes.
• Their skin is also used for leather.
• In India, sea snakes are not commercially exploited but are often killed during fishing operations.
• Population decreases due to fishery-related mortalities, mainly from trawl and gill nets bycatch.
• Loss of coral reefs and coastal habitat also contributes to their decline.

Conservation Status

• Most sea snakes are not on the CITES protection lists.
• IUCN Red List:
• 9% of marine elapids are threatened with extinction.
• 6% are Near Threatened.
• 34% are Data Deficient.
• Threatened species are found in areas like Ashmore and Hibernia Reefs in the Timor Sea, the Philippines, Niue, and Solomon Islands.
• The presence of critically endangered species in the Timor Sea indicates a need for conservation efforts.
• Long-term monitoring of populations is necessary to evaluate conservation measures and assess Data Deficient species.

Sea Snakes Overview

General Characteristics

• Sea snakes have a slender anterior and a larger, compressed posterior.
• Common colors include:
• Greyish or dirty yellow above
• White below
• Lengths can vary, with some species reaching up to 1.75 meters.

Species Descriptions

Hydrophis gracilis

• Body Shape: Similar to H. cantoris; second upper labial touches prefrontal.
• Color:
• Young: Black with 35-61 paired spots.
• Adults: Grey with yellowish spots and fading markings.
• Length: 1.03 meters.
• Habitat: Persian Gulf to Southern China and coasts of Australia; common on the Coromandel and Malabar coasts of Southern India.

Hydrophis lapemoides

• Body Shape: Moderate head, robust body.
• Color:
• Young: Yellowish or whitish with 33-43 dark dorsal bands.
• Adult: Black head with a yellow curved mark.
• Length: 1.30 meters.
• Habitat: Persian Gulf, coasts of India and Sri Lanka; rare on the east coast.

Hydrophis mamillaris

• Body Shape: Small head, slender anterior, compressed posterior.
• Color:
• Young: White.
• Adult: Light grey with 42-57 broad black bands.
• Length: 82.5 cm.
• Habitat: Rare, found in coastal areas of India from Mumbai to Visakhapatnam.

Hydrophis nigrocinctus

• Body Shape: Moderate head, elongate and robust body.
• Color:
• Usually olivaceous to brownish with 40-60 narrow dark bands.
• Yellowish head with dark markings.
• Length: 1.08 meters.
• Habitat: Coastal areas of the Bay of Bengal, particularly around the Sundarbans.

Hydrophis obscurus

• Body Shape: Eccentric sea snake.
• Color:
• Juveniles: Bluish-black with 35-55 bright yellow bars.
• Adults: Greyish or bluish above, yellowish below.
• Length: 1.2 meters (females larger).
• Habitat: East coast of India to the Myanmarese coast; common in Chilka Lake.

Hydrophis ornatus

• Common Names: Spotted sea snake, Cochin banded sea snake, Ornate sea snake.
• Body Shape: Robust and stocky.
• Color: Pale greyish or olivaceous with 41-45 dark bars.
• Length: 1.25 meters.
• Habitat: Persian Gulf to coasts of China and New Guinea; found in Indian waters.

Hydrophis spiralis

• Body Shape: Large head, slender and compressed body.
• Color: Golden yellow to yellowish green with 44-48 dark rings.
• Length: Maximum 2.75 meters (largest sea snake).
• Habitat: Persian Gulf to Celebes and Philippines; recorded in Indian waters.

Hydrophis stricticollis

• Common Name: Bengal Sea Snake.
• Body Shape: Small head, long and slender body.
• Color: Greyish or olivaceous above, yellowish below with 45-65 dark dorsal bands.
• Length: 1.06 meters.
• Habitat: East coast of India to the Myanmarese coast.

Hydrophis jerdoni

• Body Shape: Short, narrow head; slender body.
• Color: Olive brown above, yellowish or white below with black spots.
• Length: 1 meter.
• Habitat: Coasts of India and Sri Lanka to the Straits of Malacca.

Lapemis curtus

• Common Name: Short-tailed sea snake.
• Body Shape: Large head, nostrils on top of the head.
• Color: Light or dark greyish above, whitish below with 45-55 narrow black bars.
• Length: Up to 1 meter.
• Habitat: Coastal areas of the Arabian Sea, Indian Ocean, and Bay of Bengal.

Pelamis platurus

• Common Name: Pelagic sea snake; Yellow-bellied sea snake.
• Body Shape: Long, narrow head distinct from slender neck.
• Color: Black above, yellow or brown below with a prominent yellow line.
• Length: Maximum 98 cm.
• Habitat: Lives only in salt water; ranges from the east coast of Africa to the west coast of Mexico.

Thalassophis viperina

• Common Name: Viperine Sea Snake.
• Body Shape: Short head, not very wide.
• Color: Grey above and white below.
• Length: Not specified.
• Habitat: Coastal areas, specific locations not detailed.