Glossary

77 terms beginning with D · showing 1–40

1. dacriform

   Teardrop-shaped.

2. Dahomey Gap

   Dry corridor of savanna interrupting the West African rain forest and separating it into two parts known as the western Guinea and Central African Congo zones and reaching the Atlantic coast in Togo and Benin. Due to the separation, the resident flora and fauna of the Guinea and Congo zones differs to a significant extent. In terms of climate the gap has been wetter a number of times through history and has existed in its current state for around 4000 years.

   Used in 6 profiles

3. Daphnia

   Any representative of the genus Daphnia; small, planktonic crustaceans commonly referred to as 'water fleas' and often used as food for ornamental fishes. They're members of the order Cladocera and reproduce by parthenogenesis.

   Used in 749 profiles

4. Darwinism

   Used here on SF in reference to the theory of biological evolution whereby evolution occurs by a process of natural selection thus ensuring survival of the fittest. Includes some theories unconnected with the work of Charles Darwin and has been applied to a range of different philosophies over time, however.

5. decapod

   Any member of the crustacean order Decapoda, comprising species possessing 5 pairs of jointed, thorassic limbs such as crabs, crayfish, lobsters and shrimp. Also used historically in reference to molluscs of the Cephalopod superorder Decapodiformes, members of which have 8 short limbs plus 2 longer tentacles and include cuttlefish and squid.

6. decomposer

   Organism feeding on dead or decaying material aiding the natural process of decomposition by breaking down organic substances which subsequently become nutrients.

7. decomposition

   Natural, ecological process in which organic material is broken down into simpler substances which may then be used by other organisms. Typically biotic and carried out by microbes, worms, and other organisms but can also be abiotic and occur via chemical or physical processes such as oxidation or hydrolysis.

   Used in 204 profiles

8. decurved

   Curved downwards. Sometimes used in reference to the lateral line of certain fishes.

9. deep sand bed

   Method of filtration, mostly used in marine aquaria, whereby the increased depth of the sand substrate facilitates formation of an anaerobic layer where nitrate can be converted into nitrogen gas. Also known as "Jaubert" or "plenum" system and often associated with live sand.

10. defecate

    To discharge waste from the body via the anus.

11. deionisation

    Purification process, often abbrevaited to DI, by which mineral ions are removed from water, usually via ion exchange over a specialised type of resin. The process does not remove non-ionic molecules thus organic cells such as bacteria tend to remain. Often used in conjunction with reverse osmosis to produce more-or-less pure water which normally requires a degree of remineralisation before being used in aquaria.

12. deionising unit

    Device used to purify water via the process of deionisation. Some units combine both reverse osomosis and deionisation functions.

13. deleterious

    Having an adverse effect.

    Used in 2 profiles

14. demersal

    Living, occurring close to, deposited or sinking onto the bottom of a water body.

    Used in 5 profiles

15. denitrification

    Reduction of nitrates to nitrites and ammonia by the breakdown of nitrogenous compounds, or conversion of nitrates into nitrogen-containing gases. Usually carried out by microorganisms.

16. denitrify

    To reduce nitrates to nitrites and ammonia by the breakdown of nitrogenous compounds, or convert such compounds into nitrogen-containing gases.

17. dentary

    Anterior, largest and usually only tooth-bearing bone in the mandible.

    Used in 59 profiles

18. dentate

    Possessing a serrated or tooth-like edge or margin.

19. denticle

    A small tooth or toothlike projection, also see dermal denticle.

    Used in 1 profile

20. dentigerous

    Possessing teeth or tooth-like structures.

    Used in 4 profiles

21. dentition

    The arrangement, type, and number of the teeth in a particular species

    Used in 60 profiles

22. deoxygenate

    To remove oxygen from.

23. depensation

    Reduction in breeding population size leading to reduced fecundity in the overall population or stock of a species.

24. depressed

    Vertically or dorsoventrally flattened.

    Used in 51 profiles

25. derived

    Used in phylogenetics in reference to a character or character state not present in the ancestral form of a species; apomorphic.

    Used in 190 profiles

26. derived character state

    See derived trait.

27. derived state

    See derived trait.

28. derived trait

    In phylogenetics, a trait present in an organism which was absent in the last common ancestor of the group being considered; an apomorphy. Also used to refer to traits present in the ancestral form that have subsequently been lost.

29. dermal

    Of or relating to skin.

    Used in 3 profiles

30. dermal bone

    Bone-type ossifying directly from connective tissue membranes and thus lacking a cartilaginous predecessor. Tend to be more numerous in primitive fish forms.

    Used in 5 profiles

31. dermal denticle

    See placoid scale.

32. dermis

    Innermost layer of skin containing nerve endings and blood vessels. Lies under the epidermis and also known as corium.

33. description

    Used in ichthyology in reference to a written description of a new species, usually in the form of a scientifically-published paper though many have been also appeared in aquarium literature, particularly in the late twentieth century. Also referred to as 'type description' or 'original description'.

    Used in 283 profiles

34. designation

    In icthyology, the nomenclatural act by which the type specimen of a previously or newly-established genus, subgenus, species, or subspecies is fixed via an express statement.

    Used in 6 profiles

35. dessicated

    Dry; completely dried out.

    Used in 7 profiles

36. detritus

    In biology, organic debris most often formed via the decomposition of organisms.

    Used in 205 profiles

37. diadromous

    A fish that migrates between fresh and salt waters.

    Used in 17 profiles

38. diapause

    Period of suspended development in an organism characterised by greatly reduced metabolic rate; resting phase. Especially common under times of environmental stress, e.g., hibernation, aestivation.

    Used in 3 profiles

39. diaphanous

    Delicate, translucent.

40. diatom

    Large group of algae often referred to as 'brown algae' in relation to aquaria. Most are unicellular but there also exist colonial types. Very common component of phytoplankton.